kapil....network rollout for 2g & 3g

Lyallpur khalsa college Network Rollout for 2G &3G

MSC[NPD]-IVSEM/890438


1.1 Network Roll Out For 2G &3G.

This project is based on the telecommunication. The network planning is not only to define the initial network roll-out targets, but also to provide moving targets to the continuous process that takes the whole life time of the network. Before the2G and 3G network is launched, all the work is focused on estimating how the network should look like. After the network launch customer intake and behaviour will decide the network development direction.

The most demanding tasks are to gather all the required information for the planning work and making the network roll-out decisions based on all these estimations, operator demands and assumptions of future costs. Cost estimations are usually very sensitive to the changes in basic assumptions and it is crucial that all assumptions are recorded to the network roll-out plan.

Network roll out is the foundation to establish a 2G& 3G network. In this project we will design a network theoretically as well as practically. the whole planning of a network give details about the frequency need, type of media required , type of antennas , orientation ,how was the clutter in that area, How many sites we need to establish a good network etc………

1.2 Aim of network rollout

The main aim of radio network planning is to provide cost effective solution in terms of coverage and quality. The process of radio network planning starts with collecting the parameters such as network requirement of coverage and capacity. These inputs are used to make a theoretical coverage and capacity plan.Coverage planning would be defined as the coverage area services probability and related signals strength.Capacity planning would include subscribers and traffic behavior in a region.

The requirement of radio planner is to cover 100% of the area but usually it is impossible. So efforts are made to design a network that covers all the regions that may have good traffic and to have coverage hole with no traffic zone.


Pre-Planning:Define networkservices, basicnetworkconfigurationparameters…

Main Planning:Site survey,digital map,link budget,coverage plan,capacity plan…

begin End


1.3 SOFTWARE USED

MCOM ASSET EFT TEMS PLANNER

1.3.1 MCOM:

Mobile Communications Network Application (MCOM) was first introduced as a Mapbasic application tool to create a graphical representation of a mobile network in MapInfo. Starting version 3.0, MCOM has become a stand-alone application. Using OLE Automation technology, MCOM acts as an OLE client with MapInfo running in the background. This allows MCOM to have the flexibility and versatility to integrate new functions that MapBasic cannot provide.In this latest version, you get the similar user-interface as in MapInfo plus the additional ND/NPI tools.MCOM’s features can be categorized into following groups:

Cell Planning Tools Drive Test Analysis Tools [GSM only] STS Analysis Tools



System Requirements For McomMCOM2001 requires MapInfo application to be installed in your PC with a minimum physical memory of 32Mb. It has been tested for both Window 95/98 and NT Operating Systems.

1.3.2 TEMS PLANNERTEMS CellPlanner Universal is an advanced tool for designing and planning 2G, 2.5G, and 3G networks.Designed and developed by Ericsson, TEMS Cell-Planner Universal provides superior planning capabilities to save time and money during network deployment.TEMS CellPlanner Universal meets the needs of today’s complex radio networks. It features open interfaces, a new more flexible architecture, and support for all major technologies. It also utilizes unique, patented algorithms for accuracy and speed. The modular platform makes it easy to customize and add new functionality.TEMS CellPlanner Universal provides a flexible system configuration and an efficient workingenvironment. Operators can choose stand-alone configuration for quick and easy planning in the field; no database installation is required. Choosing network configuration allows multiple users, as part of a team, to share network data and simultaneously plan a common network. This team approach is regulated by a unique system of security features for safe and secure handling of data.Here is the view of TEMS planner :

Some important features of Tems planner:

2G and 3G co planning Gsm/gprs/edge support

Quality performance indicator



Propagation modeling Geographical information system

1.3.3 EFT (ERICSSON ENGINEERING TOOL)During the initial phases of the network design process, a reliable radio wave propagation tool is necessary. This need continues to exist even for the most mature radio networks. One of the primary responsibilities of an RF engineer is to improve the radio network when required to do so. This could be the result of growth or decreased performance. Ericsson Engineering Tool (EET) is based on experience and continual development adapted to a rapidly changing technology.EET is based on Planet by Mobile Systems International Ltd. (MSI). It is a UNIX open-windows-based software package designed to simplify the process of planning and optimizing acellular network.Some important features of asset tool are as follow:

Network dimensioning Frequency planning Predicting

EET can import radio survey files which can be used to tune the prediction model for the area where the network is to be planned.Data can be imported and exported to OSS

1.3.4 ASSET

Asset is also a rf planning tool .it is a GUI support tool. This software is used to design a network . it provides a step by step procedure to design a network . following can be done by using ASSET.

Adding site and site database Analysis for all sites. Use to analysis network with and without frequency hopping turn-on Used for predictions for coverage Frequency re use pattern Layer configurations Coverage threshold and types Easy to export and import data from different softwares.



1.4 ABOUT TELECOM AND TELECOM DEPARTMENTS

The Indian telecommunication industry is the world's fastest growing industry with 791.38 million mobile phone subscribers as of February 2011. It is also the second largest telecommunication network in the world in terms of number of wireless connections after China. Basically we will discuss about the wireless communication. The wireless communication works on the policies of TRAI.

1.4.1 Telecom Regulatory Authority Of India (TRAI) The entry of private service providers brought with it the inevitable need for independent regulation. The Telecom Regulatory Authority of India (TRAI) was, thus, established with effect from 20th February 1997 by an Act of Parliament, called the Telecom Regulatory Authority of India Act, 1997, to regulate telecom services, including fixation/revision of tariffs for telecom services which were earlier vested in the Central Government.

TRAIs mission is to create and nurture conditions for growth of telecommunications in the country in manner and at a pace, which will enable India to play a leading role in emerging global information society. One of the main objectives of TRAI is to provide a fair and transparent policy environment, which promotes a level playing field and facilitates fair competition. In pursuance of above objective TRAI has issued from time to time a large number of regulations, orders and directives to deal with issues coming before it and provided the required direction to the evolution of Indian telecom market from a Government owned monopoly to a multi operator multi service open competitive market. The directions, orders and regulations issued cover a wide range of subjects including tariff, interconnection and quality of service as well as governance of the Authority.

The TRAI Act was amended by an ordinance, effective from 24 January 2000, establishing a Telecommunications Dispute Settlement and Appellate Tribunal (TDSAT) to take over the adjudicatory and disputes functions from TRAI. TDSAT was set up to adjudicate any dispute between a licensor and a licensee, between two or more service providers, between a service provider and a group of consumers, and to hear and dispose of appeals against any direction, decision or order of TRAI.

1.4.2 Departments of telecom1. NSS (Network Switching Centre)

2. BSS (Base Station System)

3. OMC-R (Operations and Maintenance for Radio)

4. EFD (Engineering Front Desk)

5. Planning

6. Performance



NSS is involved in the maintenance of the Switch, over which all the calls of the customers are routed in the Network.

BSS is involved in the maintenance of the GSM Network. It involves all daily routines like Preventive Maintenance, Weather proofing, Site Expenditures, Fuel availability, Power availability, etc. These people if required also do any reconfiguration.

OMCR is there for the maintenance and operations of the radio. Any alarms in the Network are raised in OMCR, notification for which are then are sent to the concerned regions.

EFD is the front desk for the Engineering department. Any customer complaints or queries from any other department have to go through this for evaluation.

Planning Department is involved in the planning of the sites ,survey, drive tests,optimization etc.

Performance department is there to keep a check on the Network performance and to enhance the performance whenever required time by time.

Network rollout project comes under the PLANNING and BSS department. The data collected by the planning team is send to the BSS department .

1.5 Network planning project organization:

Network planning team: network pre planning and post planning and giving site proposal as an output.

Site acquisition team: responsible for actual site location finding via technical survey, lease contract etc.

Construction team: responsible for construction work of site and stability check. Telecom team: responsible for installation and commissioning of site and also for

acceptance test. Optimization team: responsible for pre-launching optimization phase.



1.6 Network planning project

There are three types of network planning project.

1. All the planning is done by the operator if they had the desired knowledge the risk factor is that the operator might not have the full knowledge of the equipments of the vendor.

2. Operator is involve in defining the network planning criteria after the roll out finish the care phase has to be out sourced but it can be done by those who has sufficient knowledge.

3. Network planning consultancy: - for planning function of a particular aspect of the job. This is done for the new technology to come these are different from the equipment vendor.

1.7 Planning criteria and targets:

The target is to plan the network in a cost effective way. It start with current market situation analysis like competitors, market share, network coverage area, services, traffic behavior, nature of targeted user and average use of that services. Target is to generate revenue for this has to provide coverage capacity and quality.

Pre planning:1. Coverage planning2. Capacity planning3. Dimensioning

Detailed planning1. Frequency planning2. Neighbor planning3. Parameter planning

Optimization1. Acceptance test 2. Verification3. Quality check

Market Analysis 1. competitors analysis2. potential customers3. traffic 4. network coverage5. user profile



Customers Requirements1. Coverage department2. Capacity department3. Quality department4. Financial limitation5. Future deployment plans



2.1 A BOUT 2G

2G (or 2-G) is short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland by Radiolinja in 1991. Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted; 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels; and 2G introduced data services for mobile, starting with SMS text messages.

After 2G was launched, the previous mobile telephone systems were retrospectively dubbed 1G. While radio signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

2G has been superseded by newer technologies such as 2.5G, 2.75G, 3G, and 4G; however, 2G networks are still used in many parts of the world.

2.2 ARCHITECTURE

Mobile

The GSM mobile station (or mobile phone) communicates with other parts of the system through the base-station Base station system

SIM (SUBSCRIBER IDENTITY MODULE)

The sim determines the identity number and calls billed to subscriber. The sim is the database on the user side. Physically it is chip,which user must insert into the mobile phone before it can be used. The sim communicates directly to the VLR and indirectly to HLR



BSS

Base transceiver station (BTS).

The base transceiver station (BTS) handles the radio interface to the mobile station. The base transceiver station is the radio equipment (transceivers and antennas)

Base station controller (BSC).

The BSC provides the control functions and physical links between the MSC and BTS. It provides functions such as handover, cell configuration data and control of RF power levels in base transceiver stations. A number of BSCs are served by a MSC.

Network Subsystem

Mobile services switching center (MSC). The MSC performs the telephony switching functions of the system. It also performs such functions as toll ticketing, network interfacing, common channel signaling and others.

Home location register (HLR).

The HLR database is used for storage and management of subscriptions. The home location register stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status. Visitor location register (VLR).

The VLR database contains temporary information about subscribers that is needed by the mobile services switching center (MSC) in order to service visiting subscribers. When a mobile station roams into a new mobile services switching center (MSC) area, the visitor location register (VLR) connected to that MSC will request data about the mobile station from the HLR, reducing the need for interrogation of the home location register (HLR). Authentication center (AUC). The AUC provides authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call. The authentication center (AUC) also protects network operators from fraud.

Equipment identity register (EIR).

The EIR database contains information on the identity of mobile equipment to prevent calls from stolen, unauthorized or defective mobile stations.



2.3 NETWORK ROLLOUT PROCESS

Network rollout can be described briefly as all the activities involved in determining which sites will be used for the radio equipment, which equipment will be used, and how the equipment will be configured. Planning means building a network able to provide service to the customers wherever they are

In order to ensure coverage and to avoid interference, every cellular network needs planning.

Flow chart of network planning


Begin

Network requirement

Nominal cell planning

Site survey selection

Frequency planning

Parameter planning

Detailed network planning

End

System tuning


2.3.1 STEP 1: NETWORK REQUIREMENTSThe cell planning process starts with traffic and coverage analysis. The analysis should produce information about the geographical area and the expected need of capacity. The types of data collected are:CostCapacityCoverageGrade of Service (GoS)Available frequenciesSpeech Quality IndexSystem growth capabilityThe traffic demand (i.e. how many subscribers will join the system and how much traffic will be generated) provides the basis for cellular network engineering. Geographical distribution of traffic demand can be calculated by using demographic data such as:Population distributionCar usage distributionIncome level distributionLand usage dataTelephone usage statisticsOther factors such as subscription charges, call charges, and price of mobile stations

2.3.2 STEP 2: NOMINAL CELL PLAN

Upon compilation of the data received from the traffic and coverage analysis, a nominal cell plan is produced. The nominal cell plan is a graphical representation of the network and simply looks like a cell pattern on a map. However, a lot of work lies behind it Nominal cell plans are the first cell plans produced and form the basis for further planning. Quite often a nominal cell plan, together with one or two examples of coverage predictions, is included in tenders.At this stage, coverage and interference predictions are usually started. Such planning needs computer-aided analysis tools for radio propagation studies, e.g. Ericsson’s planning tool known as the Ericsson Engineering Tool (EET).

2.3.2 STEP 3: SURVEYS (AND RADIO MEASUREMENTS)

The nominal cell plan has been produced and the coverage and interference predictions have been roughly verified. Now it is time to visit the sites where the radio equipment will be placedand perform radio measurements. The former is important because it is necessary to assess the real environment to determine whether it is a suitable site location when planning a cellular network. The latter is very important because even better predictions can be obtained by using field measurements of the signal strengths in the actual terrain where the mobile station will be located.



2.3.4STEP 4: SYSTEM DESIGN & IMPLEMENTATIONOnce we optimize and can trust the predictions generated by the planning tool, the dimensioning of the RBS equipment, BSC, and MSC is performed. The final cell plan is then produced. Asthe name implies, this plan is later used during system installation. In addition, a document called Cell Design Data (CDD) containing all cell parameters for each cell is completed.System installation, commissioning, and testing are performed following final cell planning and system design.

2.3.5STEP 5 FREQUANCY PLANNINGThe main goal of the frequency-planning task is to increase the efficiency of the spectrum usage, keeping the interference in the network below some predefined level. Therefore it is always related to interference predictions. There are two basic approaches to solve the frequency assignment problem.

• Frequency reuse patterns • Automatic frequency allocation

Some software’s are used with automatic frequency allocation algorithms for finding the optimum solutions.

2.3.6. STEP 6: SYSTEM TUNINGAfter the system has been installed, it is continually evaluated to determine how well it meets the demand. This is called system tuning. It involves:Checking that the final cell plan was implemented successfullyEvaluating customer complaintsChecking that the network performance is acceptableChanging parameters and performing other measures (ifneeded)The system needs constant retuning because the traffic and number of subscribers increases continuously. Eventually, the system reaches a point where it must be expanded so that it can manage the increasing load and new traffic. At this point, a coverage analysis is performed and the cell planning process cycle begins again.



3.1



Network requirements

Database Antenna patterns Path loss predictions

3.1.1 Database: Several types of databases are available, depending on the scenario a computation should be done. Following types of data is available

Topographical Database 3D Vector Building Databases 3D Indoor Databases

Topographical DatabaseThe topography has a significant influence on the accuracy of the propagation model. Shadowing by hills is quite important and therefore highly accurate databases are required. Databases can be purchased in different resolutions from several distributors.

the USGS(United States Geological Survey) has been offering topographical databases for a large area of the earth (except the polar regions) This data can directly be converted with WinProp to WinProp's data format. So WinProp can be used together without any further costs for topographical databases.

Topographical datbase

To increase the accuracy of the prediction, the land usage (forest, open area, suburban, urban, dense urban, traffic,...) at the receiver pixel can be used for a specific additional loss to be added to the receiver pixel. In WinProp this loss can be defined frequency dependent, i.e. different losses for different frequency bands.



Besides the loss at the reciver pixel the clutter database can also be used to define the ground properties (for ground reflection or scattering)

Topographical data is than converted into clutter file format. So that analyzer can estimate all the related information of that particular region .

Clutter / Morpho / Land Usage

3D Vector Building Databases Vector databases are the most accurate type of building databases for urban scenarios. These vector databases should therefore be used in (dense) urban areas to get the highest accuracy in the path loss predictions.

3d vector building database



The objetcs (i.e. buildings) in the database should be compatible to the following requirements: Polygonal cylinders Arbitrary number of corners (supported during conversion)

During computation WinProp uses inrternally max. 256 corners and removes redundant corners if necessary.

Flat rooftop (uniform height of building)

Individual characterization of material properties for each building

Vegetation blocks (parks and trees) - also defined as polygonal cylinder

Additional consideration of topography possible (either building height relative to ground level or absolute to sea level).

If CNP for combined urban/indoor analysis is selected, indoor walls can be considered additionally (this is optional). In CNP mode also non-falt-rooftops can be modeled.

3D Indoor Databases

In indoor environments an accurate description of the walls and objects inside the buildings is very important. WinProp uses full 3D vector databases (palanr objects with polyginal shape) for its accurate propagation models to describe the scenario (walls,...).

The databases should have the following features:

Polygonal shape of each object Arbitrary number of corners can be converted - WinProp uses internally max. 256 corners

and removes redundant corners if necessary.

Flat / planar objects

Individual characterization of material properties for each wall

Additional subdivisions (e.g. doors, windows,... max 256 subdivisions per wall possible) with individual material properties possible.

3.1.2 Antenna patterns Each antenna has a unique radiation pattern.This pattern can be represented graphically by plotting the received time-averaged power, as a function of angle with respect to the direction ofmaximum power in a log-polar diagram. The pattern is representative of the antenna’s performance in a testenvironment. However, it only applies to the free-space environment in which the test measurement takes place. Upon installation, the pattern becomes more complex


http://www.awe-communications.com/Databases/Indoor.html

http://www.awe-communications.com/Propagation/General/CNP/index.htm


due to the extra factors affecting propagation under field conditions. Thus the real effectiveness of any antenna is measured in the field.

ISOTROPIC ANTENNA: An isotropic antenna is a completely non-directional antennathat radiates equally in all directions. Since all practical antennas exhibit some degree of directivity, the isotropic antenna exists only as a mathematical concept. The isotropic antenna can be used as a reference to specify the gain of a practical antenna. The gain of an antenna referenced isotropically is the ratio between the power required in the practical antenna and the power required in an isotropic antenna to achieve the same field strength in the desired direction of the measured practical antenna. The directive gain in relation to an isotropic antenna is called dBi.

HALF-WAVE DIPOLE ANTENNA: A half-wave dipole antenna may also be used as a gain reference for practical antennas. The half-wave dipole is a straight conductor cut to one-half of the electrical wavelength with the radio frequency signal fed to the middle of the conductor.Figure illustrates the radiation pattern of the half-wave dipole which normally is referred to as a dipole. Whereas the isotropic antenna’s three dimensional radiation pattern is spherical, the dipole antenna’s three dimensional pattern is shaped like a donut.

When choosing an antenna for a specific application, the manufacturer’s data sheet must be consulted. The data sheet contains information including antenna gain, beam width(vertical and horizontal), and graphs showing the vertical and horizontal patterns. The patterns displayed are those of a directional antenna. The antenna’s gain is approximately 15 dBd.



3.1.3 Path loss predictions: For the installation of mobile radio systems, wave propagation models are necessary to determine the propagation characteristics. The path loss predictions are required for the coverage planning, the determination of multipath effects as well as for interference and cell calculations, which are the basis for the high-level network planning process. signal path loss is a particularly important element in the design of any radio communications system or wireless system.

The radio signal path loss will determine many elements of the radio communications system in particular the transmitter power, and the antennas, especially their gain, height and general location. The radio path loss will also affect other elements such as the required receiver sensitivity, the form of transmission used and this planning process includes the prediction of the received power in order to determine the parameter sets of the base transceiver stations (or access points)..

Propagation Scenarios Satellite scenario Rural scenario Urban scenario Indoor scenario Time variant scenario



Satellite scenario: Geostationary satellites are defined by their height (e.g. 36,000 km) and their longitude. All LEOs and navigation satellites are described either by the Two Line Element method or for the GPS satellites. Antenna gains for the satellite transmitters are considered in the path loss predictions. The satellite radio transmission to the mobile terminal is strongly affected by the variation of the received signal power because of the presence of fading phenomenaRural scenario: Propagation of electromagnetic waves in areas with a low density of buildings depends mainly on the topography and the land usage(clutter). The vector data of the buildings must not be considered in such scenarios

Generally the usage of topography and land usage without any further vector building data is recommended if the transmitting antenna (basestation) is located on a hill (or very tall building/mast) and if the propagation in the vertical plane between Tx and Rx is dominating.Urban scenario: Propagation of electromagnetic waves in urban scenarios in the frequency range above 300 MHz is influenced by reflections and diffractions at the buildings. Therefore a detailed vector data base of the buildings is required.

Indoor scenario: Propagation of electromagnetic waves inside buildings in the frequency range above 600 MHz is influenced mainly by the walls (and large furniture elements). Diffractions around corners as well as waveguiding in corridors (due to multiple reflections) are dominating the propagation inside buildings.

Time variant scenario: Wireless communications in time variant ad-hoc networks is very challenging. The increasing demand for mobile multimedia and safety applications in time-variant environments requires new concepts for the development of such wireless systems. Time variant scenarios can be found in several environments:

car-to-car (or car-to-infrastructure) communication scenarios used for driving assistance systems

MESH and sensor networks in time-variant scenarios

Wi-Fi hotspots in railroad stations, airports or city centers



Stations and underground stations with moving trains

Airports with moving airplanes Elevators inside buildings

Car-to-car communications

The main difference in such applications compared to the classical network planning is the time variance of these scenarios. The locations of transmitters, receivers, and obstacles are time-variant (i.e. moving). These effects influence the propagation and lead to time variant channel impulse responses. Doppler shifts and the directional channel impulse response are mandatory results when simulating such time-variant scenarios.

Propagation model: Propagation models are essentially curve fitting exercises. Propagation tests are conducted at different frequencies, antenna heights, and locations over different periods and distances. The receive signal data is analyzed using mathematical tools and are fitted to an appropriate curve. Formula to match these curve are then generated and used as models. Some of the major propagation models are:

• Long-distance propagation model • Longley-Rice model (irregular terrain model) • Okumara • Hata • Cost 231-Hata (similar to Hata: for 1500-2000 MHz band) • Wolfish-Ikegami Cost 231 • Wolfish-Xia JTC • XLOS (Motorola proprietary model) • Bullington • Du Path loss model • Diffracting Screens model


http://www.awe-communications.com/Propagation/Automotive/images/scenario_large.jpg


Which model should be used:Cell planners using various planning tools have their favourite models.To find the path

loss in the particular area we have a tool asset. By filling the parameters values from k1to k7 we can calculate the path loss

Where the parameters from k1 to k7 are as follow:

k1/k2 – attenuation intercept and slopek3 – mobile antenna height correction factork4 – mobile antenna height multiplying factork5 – BTS antenna height multiplying factork6 – Hata multiplying factork7 - diffraction loss (model-dependant)Clutter loss – Clutter attenuation adjustment

3.2 PRE PLANNING OF COVERAGE AND CAPACITY:

The cell planning process starts with traffic and coverage analysis. The analysis should produce information about the geographical area and the expected need of capacity. The typesOf data collected are:

Cost Capacity



Coverage Grade of Service (GoS) Available frequencies Speech Quality Index System growth capability

The traffic demand (i.e. how many subscribers will join the system and how much traffic will be generated) provides the basis for cellular network engineering. Geographical distribution of traffic demand can be calculated by using demographic data such as:

Population distribution Car usage distribution Income level distribution Land usage data Telephone usage statistics Other factors such as subscription charges, call charges, and price of mobile stations

All the above mentioned data will be collected using the network planning tools. Tools are the software packages that help for planning the network. Some of the software packages used in cellular network planning is

• Networking planning system (NPS/X) • Network measurement system (NMS/X) developed by Nokia

Cellular planning with NPS/X is based on utilization of digitized map and measurement results. The design database includes the parameters of the base stations, antennas, propagation models and system parameters. Planning process can be divided into three parts:

1. Capacity Planning 2. Coverage Planning 3. Parameter Planning

3.3 CAPACITY PLANNING Network dimensioning Network Dimensioning (ND) is usually the first task to start the planning of a given cellular network. The main result is an estimation of the equipment necessary to meet the following requirements.

• Capacity • Coverage • Quality

ND gives an overall picture of the network and is used as a base for all further planning activities.



3.3.1 Network dimensioning input The inputs are

• Capacity related Spectrum available. Subscriber growth forecast

Traffic density map Traffic per subs)

• Coverage related Coverage regions Area type’s information

• Quality related MS classes Blocking probability Location probability Redundancy Indoor coverage.

The operator normally supplies the input data, but use of defaults is also possible. The technical parameter and characteristics of the equipment to be used are another very important part of the input. This includes the basic network modules (MSC, BSC, and BTS) as well as some additional elements (antennas, cables…)

3.3.2Capacity calculation The capacity of a given network is measured in terms of the subscribers or the traffic load that it can handle. The former requires knowledge of subscriber calling habits (average traffic per subscriber) while the latter is more general. The steps for calculating the network capacity are

• Find the maximum no of carriers per cell that can be reached for the different regions based on the frequency reuse patterns and the available spectrum.

• Calculate the capacity of the given cell using blocking probability and the number of carriers.

• Finally the sum of all cell capacities gives the network capacity.

Spectrum efficiency = S / (n X A X B)

S - Total spectrum available n - Reuse factor A - Cell area B - Channel bandwidth

Erlang B table To calculate the capacity of the given cell using blocking probability and the number of carriers we need the well-known Erlang B table or formulas and the no of traffic channels for different



number of carriers. The result we get is the traffic capacity in Erlangs, which can easily be transferred into the number of subscribers. Erlangs = n X t / 3600

• n = no of calls attempted • t = total duration in seconds

3.4 COVERAGE PLANNING:

The first step in coverage planning is to create a preliminary plan based on the calculated numberof base stations from the dimensioning phase, which is agreed with the operator. The BTS locations are theoretical in this phase, because they have not been verified in the field. The usage of omni and/or sectorised antennas is part of the planning strategy. Omni cells can be used in rural or other sparsely inhabited areas, where there are not high capacity requirements. As stated before for base stations having sectorised antennas, it is easier to give coverage to precise locations.The next step is to start to find actual base station locations, which is a task of the site acquisitionteam. To find an optimal BTS location is an essential but complicated task. What makes it complicated are the many practical requirements and especially the transmission that need to be arranged. When the actual BTS location has been found the preliminary location changes and the plan is updated and the cell coverage areas are calculated again using the new parameters. All the preliminary BTS locations are gone through in the order the actual BTS locations are found and the coverage areas are always recalculated. Normally the plan is divided into smaller segments, each consisting of some base stations located close by. The segment can be drawn on the map as a geographically logical area, with the particular base stations inside the area. The aim is to find actual BTS locations segment by segment and to finalize the preliminary coverage plan one area at a time. When finding the actual base station locations it is important to reach the planning



requirements. The coverage and capacity requirement needs to be reached with the actual BTS locations.When calculating the cell coverage with a planning tool the calculation range has to be wide, especially when the later interference estimation needs to be accurate. The common way to show the calculated coverage for a certain area is to view a composite plot with specified thresholds. In this type of presentation it is easy to see possible gaps in the coverage area.The objective of coverage planning phase in coverage limited network areas is to find a minimum amount of cell sites with optimum locations for producing the required coverage for the target area. Coverage planning is normally performed with prediction modules on digital map database. The basic input information for coverage planning includes:

• Coverage regions • Coverage threshold values on per regions (outdoor, in-car, indoor) • Antenna (tower height limitations) • Preferred antenna line system specifications • Preferred BTS specification

Activities such as propagation modeling, field strength predictions and measurements are usually referred to as coverage planning.

3.4.1 Coverage predictions The possibilities for rough coverage calculations based on propagation curves formulas. These average values are not enough for the detailed network planning; therefore many computer-aided tools based on digital maps usage have been developed to improve the quality of the predictions.

3.4.2 Digital maps There are different types of information that can be digitized and used for coverage predictions. The most important from the network planning point of view are topography (terrain heights), morphography (area types), rods traffic density. For the micro cell modeling, which is required in a dense urban environment, more information and heighten resolution maps should be used. Information about the buildings and streets is essential, so the pixel size from 5m to 25m is reasonable. The streets can be stored and used in vector format.



4.1NOMINAL CELL PLANNING:Upon compilation of the data received from the traffic and coverage analysis, a nominal cell plan is produced. The nominal cell plan is a graphical representation of the network and simplylooks like a cell pattern on a map. However, a lot of work lies behind it.Nominal cell plans are the first cell plans produced and form the basis for further planning. Quite often a nominal cell plan, together with one or two examples of coverage predictions, is included in tenders.At this stage, coverage and interference predictions are usually started.Following is the procedure of cell planning using the MCOM :

4.2Getting started with MCOMTo get started with MCOM, first create a new MCOM Project file (*.mcm). This project file contains general information of the project, links the corresponding MapInfo workspace files and STS databases. The project file also contains customised settings. MCOM Project has .mcm extension. You can open a project file from File menu or Open Project button in the Main Toolbar. For quick starts, double-clicking the project file in Windows Explorer will launch MCOM and open the file.

4.2.1Creating a new project file

1. On the File menu, click New or Click New2. In Project Properties Dialog, enter Network name and Country3. Select the Map Projection type, which will be used in creating map data. n)4. Select the type of network: GSM or TDMA5. Select the Frequency Group file 6. Click OK7. In the File name box, type a name for the project.

4.2.2Getting Network Data into MCOMAfter creating the project file, the second step is to extract network data such as the site, carrier and neighbour databases into MCOM. MCOM offers a user-friendly Import Wizard to help you to perform these tasks.In the Import Wizard, the following import types are supported:

Import MCOM Text Database files; Site data, Carrier data and Neighbour data. for more information about this format.

Import Carrier and Neighbour data from one or more BSC dump files, either from the OSS or FIOL terminals. [GSM only]

Import Carrier and Neighbour data from one or more MSC dump files, either from the OSS or FIOL terminals. [TDMA only]

Import MCOM Version 2 MapInfo Database files (e.g. Msite.tab,Mcarrier.tab and Mniegh.tab)

Import Site data from EET's Site Database.



Import Map Vector Data Importing MCOM Text Database On the Cell-Planning menu, click Import Wizard Select MCOM2001 Data Text file in the import types list. Select the import files (Site data, Carrier data & Neighbour data)

and click Next Select the output directory and click Next Select the size of the antenna and carrier font Enter the Offset for X and Y if required For Carrier file import, you can choose to update the BSC and CI fields in MCOM2001

Site database from the Carrier database clicking Create New Folder button.

Importing Site data from EET's Site Database.Since most Ericsson customers use EET or TCP as their Cell Planning Tool, MCOM2001 provides an easy way to import the site database directly from EET’s Site Database.Following are the steps: On the Cell-Planning menu, click Import Wizard Select ‘Import EET Site Database’ in the import types list and click Next Select the EET Site database and flag type files and click Next.

4.3 Working with Cell-Planning ToolsMCOM2001 provides a geographical presentation of a mobile network using the MapInfo engine.

4.3.1 Redrawing the Sites on the map1. In the Cell-Planning menu, click Redraw Sites2. Select the new Antenna size3. Select the new Carrier Font size4. Select the new STS Label Position5. If you want to keep the same Thematic layer after redrawing,tick the ‘Preserve Thematic

Layer’ checkbox6. Click OK

In the Redraw Sites dialog box, user can

1. " choose to not to redraw certain object by ticking the ‘No Redraw’ checkbox2. " use the existing size value in the database field ‘Ant_size’ or ‘Font_size’3. User can also select a group of cells required to be redrawn using the ‘Redraw Selection’

tool button.

.4.3.2 Managing Site DatabaseMCOM2001 offers a Site Database control for you to add new site, edit an existing site or delete a site. You can view the Site Database control from Cell-Planning…Site Database or clicking the Site Database tool button



Following are the functions in the Site Database control:

Add New Sites—After entering the new site Id, a new site with a single cell will added to MCOMSite database. This new cell do not has any Site object until provide the co-ordinates in the Edit Site control. This new cell also does not contain any carrier data until you edit the site in the Edit Site control.

Delete Site—Delete the selected Site in the list box. Once deleted, MCOM will remove the carrier data and STS label data from the MCOM Database.

Find the site—Once click MCOM will centre the map to the selected site Edit Site—Once clicked, the Edit Site control will be displayed.

site database dialog box4.3.3 Edit the Site DataYou can edit all any site information using the Edit Site control. The Edit Site dialog can be displayed from the Site Database or using the ‘Click-on Map Edit Site’ tool buttonFollowing are the functions in the Edit Site control:

Change the Site information such as Site Id, Site name Move the site using ‘Position Site’ function. After clicking the ‘Position Site’ button,

click a new location on the map to get the latitude and longitude. Press ‘Apply’ to move the site.

Add, delete or Edit the cell information Commit All—Save all changes made in the MCOMSite, MCOMCarrier, MCOMSTS

database4.3.4 Carrier data of a cellFrom the main menu: In the Cell-Planning menu, click Edit Carrier

1. Carrier Database Dialog will appear.2. Double-click the cell which you want to edit its’ Carrier data3. Edit the Carrier data4. Click OK to take effect

From the toolbar:



1. Click Edit Frequency Tool button On the map, click the carrier text that you want to edit2. Edit the Carrier Data3. Click OK to take effect

Edit site data base dialog box

The above figure shows the nominal cells.

4.4 LINK BUDGET PLANNING



Linkbudget is a calculation to balance the uplink and downlink signal strength. The effect of this calculation is basically applicable only in places where the signal level is very low (below -95dbm) - usually at the fringe of a cell.In mobile communication environment the mobile ERP is the limiting factor, i.e. Up link limited. The losses/gain due to the following components equally affect both up & down links, so these components have negligible effect on the path balance equation. The common components are BS (Base station) cable loss, BS connector loss, BS antenna gain, MS (Mobile station) antenna gain, MS cable loss, Body/polarization loss.

Down Link equ. PApwr - Comb. Loss- Other losses = -102 dBm (mobile recv. Sens.)

Up Link equ. Mob. ERP- Div. Gain- Other losses = -104 dBm (Base recv. Sens.)

Combining the above equationsPApwr -Comb. Loss = Mob. ERP + Div. Gain*- 102+104

= 33 dBm + 4 dB + 2 dB= 39 dBm

* RBS 918 uses Max ratio combining scheme (MRCB) for which 4 dB Diversity gain isConservativeSince PA output power is adjusted insteps of 2 dB by BSTPWRRED parameter, 40 dBm atthe output of the combiner results in a balanced path.

Accompanying table is provided to illustrate above calculations. PApwr in the table is beforethe combiner. Attenuation factor for Filter combiner = 2.1 dB, for Hybrid combiner = 4.8 dB.R.F Link Budget for FILTER combinerNote: Enter all losses as negative values

Uplink downlinkMS/BS transmit pwr 33 43 dbmMS/BS transmit ERP

33 48.2 dbm

BS comb. loss -4,8 dbBS cable loss -3 -3 dbBS connector loss -1 -1 dbBS antenna gain 13 13 dbdMS antenna gain 0 0 dbMS cable loss 0 0 dbBS diversity gain 4 dbFade margin -6 -6 dbBody polarization -4 -4 dbMax path loss 140 140.2 dbPath imbalance -0.2 0.2MS/BS rcv sens. -104 -102 dbm



5.1 SITE SURVEY SELECTION:



The survey for a site is done so as to find the best cell site location. After site selection ,frequencies are allocated to each site keeping in mind there shouldn’t be interference. Then after parameter planning is done this includes :- cell services, area definition, channel configuration ,handover parameters, power control parameter and other desired network parameters.Final radio planning consist of coverage plan, capacity estimation, interference analysis, power budget calculation, parameter plan, acceptance test and verification.

Radio network survey:The cell planning process results in a cell plan with nominal site positions. If the operator has access to existing locations, it is necessary to adapt the cell plan according to these locations.For this reason, it is important that the cell planner has a basic knowledge of the locations that can be used. The on-site cell planning work that takes place is called the “Radio Network Survey”.

There are two type of site surveys Anchor site survey Sharing site survey

ANCHOR SITE: anchor site is of two type : nominal site and blind site. Nominal site following data will given to the rf engineer

Latitude and longitudes of that place which has been selected for the site . Search ring : In case the given points are not available then that the area

around the given latitude and longitude is the search ring. So that rf engineer will search out new place. Normally this search ring is of 50 to 300 mtrs.

Hot spots : two or three latitudes or longitudes for the same place.

Blind site: For the survey of blind site the there will be no data given to rf engineer.He/she will have to go a place and find the two or three hot spots for the site.

SHARING SITE: survey for already established site where we want add our network. These types of sites are basically search for the capacity addition.

5.2 SITE REQUIREMENTSThe proposed network design shows only approximate site locations. The exact site position depends on the possibilities to construct a site on the suggested location.Different permits are usually necessary, e.g. a planning permit from the local council planning committee. Masts or towers almost always require planning permits and in many cases they are

subject to permits from civil aviation or military authorities (i.e. obstruction lighting may be needed).



Permission to use the site or a lease contract must be agreed upon with the owner of the site.

Besides the need for the permits, the following must also be taken into account:

Access roads - The site must be accessible to installation personnel and heavy trucks and if there is no road leading to the site, a helicopter might be needed for material transports and for mast or tower installation.

Material transport and storage - The site must have an area suitable for efficient unloading and handling of goods.

Space requirements - For an outdoor site it is necessary that the ground area is large enough for the radio base station and tower or mast foundation. Power cables must be installed and a mains power source must be found in the vicinity of the site if mains power is not available at the site. For an indoor site, the RBS equipment room must fulfill a number of requirements concerning mains power connection such as grounding, power outlet, and space for transport network interface products.

Antenna support structures - These must be provided. They can consist of several short pipes on a roof, a guyed mast, or a self-supporting tower. The term “tower” usually refers to a self-supported structure, while the term “mast” refers to a structure supported with guy wires.

Transmission access - A number of Pulse Coded Modulation(PCM) transmission lines are needed. Two types of transmission network standards may occur. The first case is 2 Mbit/s PCM with 75 ohm unbalanced or 120 ohm balanced lines, the second case is 1.5 Mbit/s PCM using 100ohm balanced lines.

Antenna feeder routes - Indoors, the antenna feeder paths must have proper cable support facilities, preferably a cable ladder. The antenna feeder may also be placed in available cable chutes inside the building. Outdoors, feeder cable paths from an antenna supporting structure fall into two categories. Cables can be installed on cable ladders above ground from the antenna or through underground cable ducts.

5.3BASIC CONSIDERATIONS

It is likely that the system operator has a number of alternative buildings which may be used in the cellular network planning phase. One reason for this is to reduce the initial cost.The following aspects of site selection must be studied:Position relative to nominal gridSpace for antennasAntenna separationsNearby obstaclesSpace for radio equipmentPower supply/battery backupTransmission linkService area study



Contract with the owner

5.3.1 POSITION RELATIVE TO NOMINAL GRIDThe initial study for a cell system often results in a theoretical cell pattern with nominal positions for the site locations. The existing buildings must then be adapted in such a way that thereal positions are established and replace the nominal positions.The visit to the site is to ensure the exact location (address/coordinates and ground level). It is also possible for more than one existing site to be used for a specific nominalposition.5.3.2 SPACE FOR ANTENNASThe radio propagation predictions provide an indication on what type of antennas can be used on the base station and in what direction the antennas should be oriented.The predicted antenna height should be used as a guideline when the on site study starts. If space can be found within a maximum deviation of 15% from the predicted height the original predictions can be used with sufficient accuracy.If it is possible to install the antennas at a higher position than the predicted position, the operator must ensure that there is no risk for co-channel interference. If the antennas are to be installed at a lower position than predicted, new predictions must be carried out based on this position.It is not necessary that all antennas in one particular cell have the same height or direction. That is, it is possible to have cells on the same base station with different antenna heights. This canbe the case if space is limited in some directions. There are also cell planning reasons for placing antennas at different heights. This includes coverage, isolation, diversity and/or interference.

5.3.3 ANTENNA SEPARATIONSThere are two reasons for antennas to be separated from each other and from other antenna systems:To achieve space diversityTo achieve isolationThe horizontal separation distance to obtain sufficient space diversity between antennas is 12-18 or 4-6 m for GSM 900 and 2-3 m for GSM 1800/1900. Typical values of separationdistances between antennas to obtain sufficient isolation (normally 30 dB) are 0.4 m (horizontal) and 0.2 m (vertical) for GSM 900.

5.3.4 NEARBY OBSTACLESOne very important part in the Radio Network Survey is to classify the close surroundings with respect to influence on radio propagation. In traditional point-to-point communication networks, a line-of-sight path is required. A planning criterion is to have the first fresnel zone free from obstacles. (NOTE: The fresnel zone is the area in open space that must be practically free of obstructions for a microwave radio path to function properly, some degree of fresnel consideration is required in the immediate vicinity of the microwave radio RF envelope/field.)

It is not possible to follow this guideline because the path between the base and the mobile subscriber is normally not line-of- sight. In city areas, one cell planning criterion is to provide margins for these types of obstacles.



If optimal coverage is required, it is necessary to have the antennas free for the nearest 50-100 m. The first fresnel zone is approximately five meters at this distance (for 900 MHz). This means the lower part of the antenna system has to be five meters above the surroundings

5.3.5 SPACE FOR RADIO EQUIPMENT

Radio equipment should be placed as close as possible to the antennas in order to reduce the feeder loss and the cost for feeders. However, if these disadvantages can be accepted, other locations for the equipment can be considered. In addition, sufficient space should be allotted for future expansions. The radio network survey includes a brief study with respect to this matter. A more detailed analysis takes place when the location is chosen to be included in the cellular network.

5.3.6 POWER SUPPLY/BATTERY BACKUPThe equipment power supply must be estimated and the possibility of obtaining this power must be checked. Space for battery back-up may be required.

5.3.7 TRANSMISSION LINKThe base station must be physically connected to the BSC. This can be carried out via radio link, fiber cable, or copper cable. Detailed transmission planning is not included in this course.

5.3.8 SERVICE AREA STUDYDuring the network survey it is important to study the intended service areas from the actual and alternate base station locations. Coverage predictions must be checked with respect to critical areas.5.3.9 CONTRACT WITH THE OWNERThe necessary legal documentation must exist between the land owner and the proposed site user, e.g. a contract for site leasing. Even though cost is a major consideration in the site acquisition process, cost is not discussed as a factor in this course.

5.4 RADIO MEASUREMENTS5.4.1 PATH LOSS PARAMETERSA radio survey involves installation of a transportable test transmitter somewhere in the area be measured. For this purpose, Ericsson has designed a computerized measurement system. A locating unit, a measuring receiver with antenna, a control and processing unit, and a tape recorder are among the equipment contained in the unit. Signal level can be measured on a number of channels and, for each channel, samples are taken at an adjustable speed. Normally,samples are taken several times per wavelength traveled.

The data is pre-processed before it is stored on either the hard drive or a diskette and presented off-line after the survey. Results can be presented with respect to median value, standard deviation, and number of “measuring squares” along the test routes. The recorded files can be imported into EET and displayed on the map. The residual values (i.e. the difference between the



prediction and the measurement, can also be displayed. If there is a difference, the path loss parameters in the prediction model can be adjusted according to the measurements.

5.4.2 TIME DISPERSIONMeasurements must be performed to verify the time dispersion predictions. In addition, if there are quality problems, time dispersion measurements must be taken to verify that time dispersion is actually causing the poor quality. The equipment used for time dispersion measurements consists of a transmitter and a receiver. The transmitter sends a short pulse, the signal is received and the pulse response is evaluated in a controller. In this way, the time delay and the carrier to reflection ratio can be found.

Time dispersion measurement equipment

5.4.3 INTERFERING TRANSMITTERSFor sites where a number of other radio transmitters are collocated, RF Engineers recommends that radio spectrum measurements and a subsequent interference analysis be performed. These include a computer controlled spectrum analyzer and computer programs for calculating interference levels at different frequencies. The end result of a radio spectrum measurement is to accept the site from an interference point of view, to accept it with reservations, or to reject the site and find another one.

5.5 PROCEDURES FOR THE SURVEY



Rf survey is done so as to find the best cell site location. Keeping in mind,civil criteria and commercial viability.

5.5.1 Survey pictures:


Preliminary radio network design

Define the search ring for the nominal point

Take photographs of the clutter as asked by the vendor

Enter the building and go to the top roof

Go to the nominal point

Result

Take notes and describe the nominal point


at 30 deg at 60 deg at 90 deg

At 120 deg at 150 deg at 180 deg



5.5.2SURVEY FORMS



5.5.3 SHARING SURVEY STEPS:



5.5.4 STEPS FOR BLIND SURVEY:

5.6 PROCEDURE FOR SITE SELECTION


Nominal data about the site like planned height, latitude,longitude and planned

orientation is given.

Check the microwaves orientation and also on which lack of tower is mounted

Check the shelter space, stability and planned antenna height and planned orientation if there is no

space in shelter outdoor BTS can be purposed

Take the photographs at 360 degree angle of the clutter so that orientation can be finalized.

Go to the latitude longitude and check the presence of the site.

Fill the given form and make the report as per the format.

Go to the lat. long

Find the hot spots in the defined search ring


Maximum height of the building is to be consider so that we can find where we need to mount the GSM antenna. But we should also considered the second highest building so that the coverage can be given to the top floor of the highest building.

All the buildings with the basement has to be taken care of so that tilt can be finalized.

Our site should be near to the +ve clutter so that maximum coverage can be provided. While performing the survey information should be collected like type of area, types

of clutter, major competitor, approximate population. After this orientation of GSM antenna should be estimated. All the information should be gathered and filled properly so as to have no confusion.

Major things to be note:

1) Obstacles2) High tension line3) Power grid4) Water tank5) Railway lines6) Vegetation7) Water bodies

Height Of The Building =G+3N

where G is the height of ground floor and N is the no.of floors in that building

Length Of Feeder Cabel = height of antenna + 5m



6.1 FREQUENCY ALLOCATION Figure shown earlier lists the band allocations for each of the different GSM based networks.



In many countries, the whole frequency band will not be used from the outset.

Following figure show the frequency allocated to each site . theses can be scanned by using mcom tool

6.2 CHANNEL CONCEPTThe carrier separation in GSM is 200 kHz. That yields 124 carriers in the GSM 900 band. Since every carrier can be shared by eight MSs, the number of channels is 124 times eight = 992

Channels. These are called physical channels. The corresponding number of carriers for GSM 800 and GSM 1900 are 374 and 299, respectively.


NETWORK TYPE FREQUENCY BAND UL/DLGSM 900 890 - 915/935 - 960 MHz

GSM 1800 1710 - 1785/1805 -1880 MHz

GSM 1900 1850 - 1910/1930 -1990 MHz


6.3 LOGICAL CHANNELSOn every physical channel, a number of logical channels aremapped. Each logical channel is used for specific purposes, e.g., paging, call set-up signaling or speech. There are eleven logical channels in the GSM system. Two of them are used for traffic and nine for control signaling.Traffic CHannels (TCH): there two types of traffic channel

Full rate channel, Bm

This channel can be used for full rate or enhanced full rate speech (13 kbit/s after speech coder) or data up to 9.6 kbit/s.

Half rate channel, Lm

This channel can be used for half rate speech (6.5kbit/s after speech coder) or data up to 4.8 kbit/s.

Control channels: nine different types of control channels are used Broadcast Channels (BCH):

Frequency Correction Channel (FCCH)Used for frequency correction of the MS, downlink only.

Synchronization Channel (SCH)Carries information about TDMA frame number and Base Station Identity Code (BSIC) of the BTS, downlink only.

Broadcast Control Channel (BCCH)Broadcasts cell specific information to the MS, downlink only

Dedicated Control Channels (DCCH): Stand alone Dedicated Control Channel (SDCCH)

Used for signaling during the call set-up or registration, up and downlink.

Slow Associated Control Channel (SACCH)Control channel associated with a TCH or a SDCCH, up and downlink. On this channel the measurement reports are sent on the uplink, and timing advance and power orders on the downlink.

Fast Associated Control CHannel (FACCH)Control channel associated with a TCH, up and downlink.FACCH works in bit-stealing mode

6.4 FREQUENCY SPECTRUM



Different frequency bands are used for GSM 900, GSM 1800,and GSM 1900. In some countries, operators apply for the available frequencies. In other countries (e.g. the United States),operators purchase frequency bands at auctions.

6.4.1DUPLEX DISTANCEThe distance between the uplink and downlink frequencies is known as duplex distance. The duplex distance is different for the different frequency bands

Standards GSM900 GSM1800 GSM1900Duplex distance 45mhz 85mhz 90mhz

6.4.2CHANNEL SEPARATIONThe distance between adjacent frequencies on the uplink or the downlink is called channel separation. The channel separation is 200 kHz, regardless of the standard chosen from the ones mentioned above. This separation is needed to reduce interference from one carrier to another neighboring frequency.

6.5FREQUENCY PLANNING

The main goal of the frequency-planning task is to increase the efficiency of the spectrum usage, keeping the interference in the network below some predefined level. Therefore it is always related to interference predictions. There are two basic approaches to solve the frequency assignment problem. • Frequency reuse patterns • Automatic frequency allocation

Some software’s are used with automatic frequency allocation algorithms for finding the optimum solutions. The frequency allocation is generally guided by the following information: • Channel requirement on cell basis according to the capacity planning • Channel spacing limitations according to BTS specification • Quality of service requirement which is conserved to acceptable interference probability • Traffic density distribution over the service area • Performance of advanced system features (frequency hopping, IUO, etc….)

The frequency allocation is based on cell-to-cell interference probability estimation according to the network topology, field strength distribution and traffic load.

This results in customized frequency performance of the selected radio network elementsThe starting point of automatic frequency allocation is much better, since the exact site

coordinates and BTS characteristics are available. Usage of propagation model based on digital maps, we are able to obtain interference predictions very near to reality.



6.5.1 Frequency ReuseA frequency used in one cell can be reused in another cell at a certain distance. This distance is called reuse distance. The advantage of digital system is that they can reuse frequencies more efficiently than the analogue ones, i.e. the reuse distance can be shorter, and the capacity increased. A cellular system is based in reuse of frequencies. All the available frequencies are divided into different frequency groups so that a certain frequency always belongs to a certain frequency group. The frequency groups together form a cluster. “A cluster is an area in which all frequency groups are used once, but not reused.” The frequencies can be divided into different frequency groups. This introduces the terms reuse patterns and reuse grids. The most common reuse patterns in GSM is “4/12” and “3/9”. 4/12 means that the available frequencies are divided into 12 frequency groups, which in turn are located at 4 base stations sites. This assumes that the base station has three cells connected to it. The frequency groups are often assigned a number or name such as A1, B1, C1, D1, A2,…….. D3. 3/9 means that the available frequencies are divided into 9 frequency groups located at 3 sites. Problem with C/A might appear in certain parts of a cell, arising from adjacent frequencies in neighboring cells. Example: channel assignment of 24 frequencies in a 3/9-cell plan.

Frequency groups

A1 B1 C1 A2 B2 C2 A3 B3 C3

channels 1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 1819 20 21 22 23 24

3/9 frequancy re use patteren



3/9FREQUANCY REUSE PATTERN

Example of 4/12 patternIn 4/12 ,4 sites, each tri-sectored to give a 12 cell Cluster. Numbering of D cells allows carriers to be allocated so that no adjacent carriers are used in physically adjacent cells.

4/12 frequency group asset6.5.2 INTERFERENCEThere are three types of interference:-a) co-channel interferenceb) adjacent channel interferencec) intermodulation/noise interference

The carrier to interference ratios for co- and adjacent channels are specified as :



C/I = 9dB minimum (co-channel)C/I = -9dB minimum (adjacent channel)The definition for co-channel interference in GSM system is that a cell on the same channelcan cause interference, if the serving cells signal level is only 9dB higher than the interferingsignal. For adjacent channels, interference can be caused if the neighbouring cells signal levelis 9dB higher than the serving cell.Due to fading an additional 12 dB margin has been added to support good quality call:- C/I = 21 dB (co-channel) C/I = 3 dB (adjacent channel)

There are various methods of combating interference :-a) Down tilting Antennab) Reducing Antenna heightc) Reducing power of BTS/MSd) Using uplink/downlink adaptive power controle) Using uplink/downlink DTX (Discontinuous transmit)f) Frequency hoppingg) Sectorising sitesh) Using smaller beamwidth antennai) Improving on the frequency planj) Optimising the various handover parameters

k) Microcells

Interference calculations The reference interference ratio is defined in GSM as the interference ratio for which the required performance in terms of frame erasure, bit error rate or residual bit error rate is met. The reference interference ratios for BS and all types MSs are the following: • Co channel interference: C/Ic <= 9 dB • First adjacent channel interference: C/Ia1 <= -9 dB • Second adjacent channel interference: C/Ia2 <= -41 dB

Co channel interference The carrier to interference (C/I) ratio at a given mobile receiver can be calculated as follows: C/I = C / (I1 + I2 + …….. +Ik) Where k is the number of co channel interfering cells. For regular grid case it is possible to simplify the calculations by using the popular path loss expressions.

6.6 Time dispersion Some interference effects may be caused from the reflected signals if received outside the equalizer window. This happens only when the difference between direct path and the reflection path is larger than the equalizer window (about 4.5 km) and the reflected signal is strong enough. The reflection outside the equalizer window should be regarded as an independent co channel interferer, therefore the same reference C/I <= 9 dB should be used.



6.7 Digital maps based co channel interface

From the coverage areas calculated by the help of digital maps it is quite easy to obtain the expected interference areas. Since the frequency plan is still to be done, the multiple interferences cannot be calculated. Thus the process works for every pair of BS checking the ratio between the two-signal pixels. The probability of future multiple interference can be reduced by adding some margin, say 6 dB to the reference interference ratio. If the percent of the interfered area is larger than a given predefined level (depending on the required service quality), the pair cannot operate in the same channel. The results are presented as a matrix with elements giving the minimum slowed channel difference (in this case only 0 and 1) for every pair of BSs.



6.8 Frequency hopping Frequency hopping (FH) is changing the frequency of information signal according to a certain sequence. The transmission frequency may change at each time slot or burst and remains constant during the transmission of a burst.

FH can also decrease the overall C/I value in the network anf thus improve QOS

6.8.1 Frequency hopping behavior:

Lognormal fading and Rayleigh distributed fast fading can decrease the speech quality. Rayleigh fades are the sum of a lot of reflected and phase shifted signals. The fading at different frequencies is not the same and become more and more independent when the difference in frequency increases. With frequencies spaced sufficiently apart they can be considered completely independent (no correlation). Thus Rayleigh fading does then not damage all the bursts containing the parts of one code word in the same way. When the ms moves of high speed the difference between its positions during the reception of two successive bursts of the same channel (i.e. at least 4,615 ms) is sufficient to decorrelate Rayleigh fading variations on the signal. In this case FH does not help except if there is interference. The worst case is when ms is stationary or moves at slow speeds because the interleaved coding does not bring any benefit to reception. In this case FH “simulates ms movement” and thus the reception quality. This phenomenon is called frequency diversity.

In the other hand frequency hopping averages the interference directed towards each base station. Instead of a continuous interferer there are several interferers that affect only a short time each and with different intensity. Methods like power control and DTX (discontinuous transmission) affect only a single interference source and benefits can be distributed to the whole network by using FH. The gain, which comes from interference averaging, is called interference diversity.

6.8.2 Baseband hopping Baseband hopping occurs between TRXs in BTS. The number of frequencies used in the hopping sequence is the same as the number of TRXs in the sector. Both random and cyclic hopping can be used. The digital (baseband) and analogue (RF) parts of the TRX are separated from each other. The switching of TRXs is on a per timeslot basis ands enables a particular TCH to hop from one carrier to another.

6.8.3Synthesized hopping Synthesized hopping is available in configurations, which have at least 2 TRX per sector. It enables each TRX to change frequency on successive time slots, so that given carrier can hop quickly onto many different frequencies. The carrier on which the BCCH IS transmitted must remain at fixed frequency to enable the MS to measure correct signal strength. Both random and cyclic hopping can be used.



6.9 Discontinuous transmission (DTX) The transmission is disconnected when no information flow happens in signal. This is done by lower speech encoding bit rate than when the user is effectively speaking. This low rate flow is sufficient to encode the background noise, which is generated for the listener to avoid him thinking that the connection is broken. The low rate encoding corresponds to a decreased effective radio transmission of one frame each 20 ms to one such frame each 480 ms. Typically transmission is effective 60% of the time, which decreases the interference. In order to implement such a mechanism, the source must be able to indicate when transmission is required or not. In the case of speech, the coder must detect weather or not there is some vocal activity. This function is called Voice Activity Detection (VAD). At the reception side, the listener’s ear must not be disturbed by the sudden disappearance of noise and the decoder must therefore be able generate some Comfort noise when no signal is received. DTX is an option controlled by the operator, and which may be used independently in the MS to BTS and in BTS to MS.



6.10 PARAMETER PLANNINGWhen a new system is built or when new cells are added or changed in an existing system, the cell planner provides the operator with a document for each cell containing data for insertion of the cell in the radio network. This document is called Cell Design Data (CDD). The data from all such documents is then converted into Data transcript Tape (DT) and loaded into the corresponding BSC. A DT tape contains not only CDD information but also other data needed for the complete configuration of the BSC.The reason for having so many parameters is so the operator can adjust and tune the network to fit their specific requirements. All parameters are permitted to be set within a certain range andusually have a default value. The default values provide a good basis to start with. Parameterscan be changed later if, e.g. measurements indicate that adjustments are necessary. Several parameters should not be changed at the same time because it is more complicated to know which parameter setting change effected the system. Some of the parameters are system specific and some are set per site, cell, or subcell.

OffsetAn offset is used to make a cell appear better (or worse) than it really is by increasing/decreasing measured signal strength. The offset is a cell-to-cell relation and is always unsymmetrical.

HysteresisA hysteresis is used to prevent the ping-pong effect, meaning several consecutive handovers between two cells. The ping-pong effect can be caused by fading, the MS zigzagging between the cells, or by non-linearities in the receiver. The hysteresis is a cell-to-cell relation and is always symmetrical.

Control of Radio Network FeaturesOther parameters are used to control radio network features like Discontinuous Transmission (DTX), frequency hopping, and power control.

Timers and FiltersThere are some timers and filters which can be set by parameters. Depending on the timer settings or length of filters, the system responds faster or slower to the change. A fast system is less stable than a slower system. A fast system is necessary if micro cells are used because handovers are frequent in this case.IdentificationParameters used to identify, for example, a cell or a location area in the network.PenaltiesThe penalties are used to punish a cell in the locating algorithm. When a cell is punished, it appears worse then it really is. This is to avoid handback in case of an urgent handover or to avoid several repeated handover attempts in case of signaling failure.



Thresholds Thresholds for cell ranking, call release, and access can be set.

GSM radio pathGSM is system using time division multiple access (TDMA) frame structure. The TDMA frame has duration of 4.615 ms and consists of 8 timeslots. There is two types of logical channels carried over the timeslots: Common channels and dedicated channels

Common channelsThe common channels are used for signaling and ca be divided into broadcast channels (BCH), continuously sending information from BTS to MS, and common control channels (CCCH). The Broadcast channels send information on the cell properties such as synchronization, frequency correction, used frequencies and power levels, neighboring cells. There are three different broadcast control channels (BCCH).

The common control channels are used when establishing a signaling connection between the MS and BTS. The paging channel (PCH) is used when BTS wants to contact the MS. The MS requests a signaling channel on a random access channel (RACH). The signaling channel is allocated to the MS by using Access grant channel (AGCH)

Dedicated channelsThe dedicated channels are divided into dedicated control channels and traffic channels. Call set up signaling and location updating procedures are performed on stand-alone dedicated control channel (SDCCH). In case of a call setup the connection is transferred into a traffic channel (TCH). Both SDCCH and TCH have a parallel slow associated control channel (SACCH) which is used for transfer of measurement results from MS to BTS and power control commands from BTS to MS. During the short messages are transmitted over SACCH channel, while the fast associated control channel (FACCH) is used to transmit the handover commands to the MS.

Radio path measurements

The radio path measurements are used to keep the connection in good quality and therefore to trigger power changes and handover if needed. Both MS and BTS measure signal level and quality (bit error ratio). In addition to that MS measures the signal levels of all adjacent BCCH frequencies even though it is able to report only six best measurements.

Power control and handoverThe BTS sends the raw measurement results received from the MS (downlink) and the results of its own measurements (uplink) to the BSC every SACCH multiframe period. The BSC does not support the measurement preprocessing in the BTS.



The BSC does the preprocessing of the measurement samples namely the book keeping and the averaging. The BSC is able to maintain a table of maximum 32 measurements results for up to 32 adjacent cells per call. After the averaging the BSC makes comparisons with the thresholds related to both power control (PC) and hand over (HO) algorithms. The BSC determines the RF output power of the MS and the BTS on the basis of the results received from the pc threshold comparison process. The HO decision is based in signal strength (RXLEV), quality (RXQUAL) and distance measurements. Another possible criterion is the power budget (PBGT) or umbrella condition fulfillment from an adjacent cell. The HO command is given over FACCH, which uses TCH temporally. Handovers can be done to TCH and SDCCH. The intra BTS handover can occur either to a timeslot in a new carrier or to a different timeslot in the same carrier. The intra-BSC handover to performed autonomously by the BSC. If there is an inter-BSC handover to be performed, the BSC sends the list of performed cells to the MSC and MSC performs the handover according to that list.

Handover strategies and parameters

The HO decision process may be triggered in different situations. Similarly to the pc it is controlled by the level (RXLEV) and quality (RXQUAL) in both UL and DL. In addition to these it depends in the distance and some periodic checks (PGBT, UMBRELLA). Only one type of periodic can be used per cell. The main principle when making HO caused by radio criteria is that the new server should be better than the current one. The parameters, averaging and threshold comparison for level, quality and distance are similar to PC but only one threshold associated. The periodic checks occur every power budget (HO period PGBT) or umbrella (HO period Umbrella) period. In order to be performed the periodic checks require some data for the neighboring cells: the comparison process uses the calculated PGBT (n) or AV_RXLEV_NCELL (n) for neighboring cells instead of fixed thresholds. Like with PC it is possible by changing the HO related cell parameters to affect the HO algorithm at all stages: preprocessing, threshold comparison, decision making.

BSS Parameters

The following figure showing the example of general parameters on how the structure of the network is defined

BTS BS identity code (ncc&boc) 0…..7s BTS ID 1…...128 Cell ID 1……65535 Location Area ID mcc 0…999 lac0…65535

Number Of Blocks For Access Grant 0……7 No Of Multiframes Between Paging 2…….9



Number Of Retransmission 1,2,4,7 No Of Slot Spread Trans 3-12,14,16,20,25,32,50

Max Queue Length 0……100% Time Limit Call 1……30s Time Limit Handover 1……30s Queuing priority call 1……14 Queuing priority handover 1……14 Ms Priority Used In Queuing Y/N Queue Priority Used Y/N

Radio Link Timeout 4……64 IMSI Attach Detach Y/N

6.11 LAC DesignThe basic function of Location Area Code (LAC) is to indicate to MSC which area aparticular mobile is in. The system need to know this for paging purposes especially forincoming calls for the mobile. If the whereabouts of the mobile was unknown then systemwide paging would have to take place which is inefficient. LAC design should be based ontwo criteria.

a)The LAC design should be done in such a way that MSC would be able to locate a MS a quickly and with as little processing as possible. This is dependent on the geographicalarea. As remote area have less traffic, its LAC area should be bigger in comparison withurban area. The main aim should be to have an approximate equal distribution of trafficbetween the different LAC.B) There should be as few LAC updates as possible. Since LAC updates is done on SDCCHchannel in idle mode and is processed in MSC, too many LAC updates would causecongestion on SDCCH channel and take up the processing capacity of MSC. LAC designon a single high traffic highway as shown below where many LAC updates would occur,should be avoided.



7.1 DETAILED NETWORK DESIGN:

Detailed network design begins after the survey. The data collected during the survey is used in detailed planning of the network. The tool used for the detailed planning is ASSET tool of planning. This tool will gives the final design to the BSS department for the construction. Here is the procedure of the detailed site design.

1. Adding sites-:For a new project user will need to firstly lay down MSC and BSC in hierarchical order. the panel at the left side of the ASSET window.

Fig.7.1The above window shows the addition of MSC, BSC to the particular site.


3add site

2add bsc

1add msc


After site creation following window will appear. It has all the details of the sites under BSC.

Fig 7.2 site data base of bsc

2. In every site there are three cells normally. Following window will add cell to the site.

Fig7.3 cells creation under a site.



3. After cell creation we will add the data which is to be implemented. Then we wil add cel configuration, neighbors of that particular cell. In cel configuration we wil add the type of antenna used, type of feeder used, azimuth required for the particular cell . feeder length etc.

Fig 7.4 cell configuration

4. Next we will add the hoping, carriers and antenna /trx.

Fig 7.4 adding general information to a sector of a cell



5. After adding all the data to cell we will analysis it and if required we will change or modify it . the analysis part is done by array creation this is done by using ASSET tool.

Fig 7.5 array creation for analysis

In analysis part we will analysis the frequency hoping, minimum signal level at which a cell is considered to be serving cell, prediction models.

6. For any modification click on setting ->option Eg. we want to change the carriers the following window will appear.

Fig. 7.6 change carriers



8.1 SYSTEM TUNNING

After an initial cell plan has been compiled and approved, it is time to begin the installation of the network equipment. As a time-saving measure, we can begin to optimize the performanceof the radio network as it is being built up. Here we will use these tools. The major benefit of using these tools comes not only from their initial use but through their continued use to monitor and improve network performance.

8.2 ERICSSON ENGINEERING TOOL (EET)During the initial phases of the network design process, a reliable radio wave propagation tool is necessary. This need continues to exist even for the most mature radio networks. One of the primary responsibilities of an RF engineer is to improve the radio network when required to do so. This could be the result of growth or decreased performance. Ericsson Engineering Tool (EET) is based on experience and continual development adapted to a rapidly changing technology.EET is based on Planet by Mobile Systems International Ltd. (MSI). It is a UNIX open windows-based software package designed to simplify the process of planning and optimizing acellular network. Some of the more important features of EET are discussed in the following sections

8.2.1NETWORK DIMENSIONINGIn the software , it is easy to create new sites or move old ones. All information about the sites is stored in the site database. It is possible to make changes to one site, a group of sites, or allsites. A height path profile can be displayed between any two points on the map. This is very useful for microwave link planning.

8.2.2 FREQUENCY PLANNINGEET allows the allocation of channels or frequency groups to a cell. It is possible to do this manually or automatically. The frequency assignments are stored in the carrier database. Thefrequencies can be displayed by labeling the cell with the Absolute Radio Frequency Channel Number (ARFCN), the group name, or by color coding the coverage areas according to the frequency groups.

8.2.3 PREDICTINGWhen the sites are created it is time to initiate a prediction. It is possible to predict one site, a group of sites, or all sites. The result of the prediction is the pathloss from the sites. After predicting, arrays for coverage and interferences (C/I and C/A) can be created. The signal strength and interference levels are calculated for each pixel. The advantage of having bothprediction and array steps in this procedure is that it speeds up the calculations.



If the user would like to change, e.g. the output power at one site, there is no need for a new prediction because the change does not affect the pathloss. The user only has to create a new array. Creating arrays is just a matter of adding dB, so it is not very time-consuming. On the other hand, predictionsare more complicated.

8.2.4 TOOLSUsing EET, the user can spread traffic on the map to plan for capacity. The traffic can be displayed with different colors for different amounts of Erlangs/km or the user can highlight thecells that do not meet the specified GoS. It is possible to import data from a test mobile and display the information on the map.EET can import radio survey files which can be used to tune the prediction model for the area where the network is to be planned.Data can be imported and exported to OSS.

8.3 TEST MOBILE SYSTEM (TEMS)The TEst Mobile System (TEMS) is a test tool used to read and control the information sent over the air interface between the base station and the mobile station in a GSM system. It can also be used for radio coverage measurements. Furthermore, TEMS can be used both for field measurements and post processing. TEMS consists of a mobile station with special software, aportable PC, and optionally a GPS receiver .The mobile can be used both in active state and idle mode, additionally, it can be use in any GSM network, depending on the SIM card. Both layer two and layer three messages can be monitored and recorded.



The MS can simulate GSM 900 power class 2 to 4. It is possible to lock on a single frequency. The MS can test each time slot on a selected frequency to verify that allTCHs are available and functioning. The PC is used for presentation, control, and storage of themeasurements. For the serving cell, it is possible to display, e.g. RxLev, Rxqual, TX power, TA, Base Station Identity Code (BSIC), and ARFCN. For the six strongest neighboring cells, it is possible to display RxLev, BSIC, and ARFCN. The information can be displayed in real-time or recorded and replayed.

The GPS receiver gives the position of the measurements. When the satellite signals are shadowed by obstacles, the GPS system may be used for dead reckoning. The TEMS measurements can be imported to EET with the use of File and Information Converting System (FICS). This means that the measurements can be displayed on the map so that, e.g. the measured handovers can be compared with the predicted cell boundaries. FICS can also convert to EXCEL and word processing packages.



8.3.1TEMS TRANSMITTERFor the generation of test signals, it is suitable (however not mandatory) to use one or several TEMS Transmitters. The TEMS Transmitter is a small unit that transmits in the GSM downlink band. The output power is adjustable between 17 and 27 dBm. A complete editable BCCH is transmitted while the other 7 time slots contain an unmodulated carrier. In absence of TEMS Transmitters, a Test TransMitter (TTM) can also be used. This is a narrow band Continuous Wave (CW) transmitter with a maximum output power of 43 dBm. Additionally, the regular transmitter can be used for this function.

8.3.2 TEMS RECEIVERThe recommended receiver is TEMS Light equipment. This is a TEMS mobile station connected to a small Fujitsu PC operated with a pen. The TEMS Light program is a reduced version of normal TEMS but with the possibility to log fixpoints by marking them with the pen on a scanned map. The information in the log files is displayed on the scanned map as color marks associated with a window containing more information about each mark. If TEMS Light is not available, the standard TEMS equipment or a Test Measurement Receiver (TMR) can be used. An even faster coverage verification can be made by using TEMS Pocket. This is a test mobile station with some TEMS functions available on the mobile display. TEMS Pocket cannot be operated from a computer. Areas where the signal may be weak are checked by locking TEMS Pocket to the used Absolute Radio Frequency Channel Number (ARFCN) and Base Station Identity Code (BSIC) and reading the signal from the display. There is also an audible warning to indicate a low signal.

8.4 HOT SPOT FINDERIt is important to deploy microcells where the heaviest traffic is located (also known as “hot spots”). One way to find suitable locations for microcells is Hot Spot Finder. The Hot Spot Finder is a GH388 mobile modified to transmit a BCCH/BSIC combination signal.

Basically, it acts as a dummy cell. The mobiles in the surrounding cells will treat the Finder as a neighbor and include BCCH/BSIC combination signals in the measurement reports. Different locations and antenna types and positions can be tested prior to the implementation of the microcell. The potential traffic is estimated by looking at the measurement reports for the mobiles in the surrounding cells.8.5 OPERATIONS SUPPORT SYSTEM (OSS)

The GSM Operations Support System (OSS) is a UNIX based tool that enables the supervision, planning, and engineering of a network from one central location.



Oss main window

8.5 CELLULAR NETWORK ADMINISTRATION (CNA)One of the most important aspects of managing a cellular radio network is that of managing the individual cells. The cells represent the infrastructure from which the mobile subscriber accesses the network. Hence, a poorly managed infrastructure will most likely be reflected by dissatisfied customers and a subsequent loss of revenue. The purpose of the Cellular Network Administration (CNA) feature is to provide a user-friendly interface from which a user can manage the cells in an efficient and controlled manner.Normally, there is a multitude of radio related parameters that need to be set in several different network elements in a consistent manner in order to achieve a well-balanced, properly functioning radio network. Default parameters are used when the operator does not enter a parameter value. Parameters can be copied from one cell and pasted into another. It is also possible to create profile areas collecting all cell parameters commonly used for different types of cells. Cell parameters are validated at the time of the entry.



This particular feature helps to reduce the possibility of incorrect cell parameters and increases the efficiency of personnel as the number of cells in the network increases as shown in figure.

8.5.1 CELLULAR NETWORK ADMINISTRATION INTERFACE (CNAI)The Cellular Network Administration Interface (CNAI) is an external interface to Cellular Network Administration. The CNAI allows for an external cell planning tool, e.g. EET, to exchange information with the CNA database. The data is exchanged between the two via ASCII coded text files. The essence of this interface is to provide simplified data import and export capabilities to CNA for ease of user handling of the data transfer mechanism. Cell planning data can be used as an example. The OSS interacts with the Ericsson Engineering Tool (EET). Such external systems can retrieve data from the actual radio network, reengineer the new cell data, and transfer back the new cell data in a simple manner. This avoids time-consuming manual entry.



8.6 SYSTEM GROWTH

If the number of subscribers in a system continues to increase, at some point it becomes necessary to increase the capacity of the system. There are several ways to do this:

1. Increase the frequency band (e.g. a GSM 900 operator might buy GSM 1800 licenses)2. Implement half-rate3. Make frequency re-use tighter (e.g. going from a 4/12 re-use pattern to a 3/9 re-use

pattern by implementing frequency hopping)4. Make the cells smaller and smaller

After a description of the regular procedure for adding new sites (cell split), tightening of the re-use pattern by means of Multiple.

Re-use Pattern (MRP) is briefly discussed.These methods of adapting to system growth will directly affect the cell planning process.

8.7 THE WAY FORWARDFor increased capacity in GSM radio networks is also known as “The Way Forward”. The Way Forward is a that combines a number of techniques, features, and service products. Together they provide substantial capacity gain in GSM mobile telephone networks without the need for additional radio frequency spectrum. The focus of The Way Forward lies on tight frequency reuse and the implementation of micro cells which together provide almost unlimited possibilities of capacity expansion. The Way Forward solution concept has been developed in cooperation with GSM operators to ensure the fulfillment of customer needs and requirements. Each time The Way Forward is implemented, it is adapted to the local environment and the customer’s individual requirements. The following procedures (cell split and multiple re-use patterns) are directly involved in The Way Forward method

8.7.1CELL SPLITIt is clear that a smaller cell size increases the traffic capacity. However, a smaller cell size means more sites and a higher cost for the infrastructure. Obviously, it is preferable not to workwith an unnecessarily small cell size. What is needed is a method that matches cell sizes to the capacity requirements. The system is started using a large cell size, however, when the system capacity needs to be expanded, the cell size is decreased in order to meet the new requirements. This normally also calls for using different cell sizes in different areas. This method is called cell split, and is illustrated in Figure 1 through Figure 4.Initially, the largest possible cell size is used considering coverage range (Figure -1). Next step is to introduce three cells per site (Figure -2), using the original sites and feeding the cells from the corners. This represents a cell split of 1 to 3, (Figure-3). Now the number of sites is still the same, but the number of cells are three times as many as before.



The following step is to do a cell split of, e.g. 1 to 4 (Figure -4). As seen from the figure, the old sites are still used in the new cell plan, but additional sites are now required.

Figure-1 cell split phase 0

FIGURE -2 cell split phase1



Fig:3 cell split 1:3 (phase 2)

Cell split 1 to 3 (Figure-3) requires three times as many cells. After the split, the capacity is three times higher per area unit, and the cell area is three times smaller. The antenna directions on the site that existed before the split must be changed by 30 degrees

Fig-4 cell split 1:4(phase-3)

Cell split 1 to 4 (Figure-4) requires four times as many sites. After the split, the capacity is four times higher per area unit, and the cell area is four times smaller. There is no need to change the antenna directions in a 1:4 cell split.



NETWORK ROLLOUT FOR 3G

9.1 About 3G3G Systems are intended to provide a global mobility with wide range of services including telephony, paging, messaging, Internet and broadband data. International Telecommunication union (ITU) started the process of defining the standard for third generation systems, referred to as International Mobile Telecommunications 2000 (IMT-2000). In Europe

European Telecommunications Standard Institute(ETSI) was responsible of UMTS standardisation process. In 1998 Third Generation Partnership Project (3GPP) was formed to continue the technical specification work. 3GPP has five main UMTS standardisation areas: Radio Access Network, Core Network, Terminals, Services and System Aspects and GERAN.

3GPP Radio Access group is responsible of:

Radio Layer 1, 2 and 3 RR specification Iub, Iur and Iu Interfaces UTRAN Operation and Maintenance requirements BTS radio performance specification Conformance test specification for testing of radio aspects of base stations Specifications for radio performance aspects from the system point of view

3GPP Core Network group is responsible of:

Mobility management, call connection control signalling between the user equipment and the core network. Core network signaling between the core network nodes. Definition of interworking functions between the core network and external networks. Packet related issues. Core network aspects of the lu interface and Operation and Maintenance requirements

3GPP Terminal group is responsible of:

Service capability protocols Messaging Services end-to-end interworking USIM to Mobile Terminal interface Model/framework for terminal interfaces and services (application) execution Conformance test specifications of terminals, including radio aspects


http://www.3gpp.org/


3GPP Services and System Aspects group is responsible of:

Definition of services and feature requirements. Development of service capabilities and service architecture for cellular, fixed and cordless applications. Charging and Accounting Network Management and Security Aspects Definition, evolution, and maintenance of overall architecture.

9.2 UMTS ServicesUMTS offers teleservices (like speech or SMS) and bearer services, which provide the capability for information transfer between access points. It is possible to negotiate and renegotiate the characteristics of a bearer service at session or connection establishment and during ongoing session or connection. Both connection oriented and connectionless services are offered for Point-to-Point and Point-to-Multipoint communication.

Bearer services have different QoS parameters for maximum transfer delay, delay variation and bit error rate. Offered data rate targets are:

144 kbits/s satellite and rural outdoor 384 kbits/s urban outdoor 2048 kbits/s indoor and low range outdoor

UMTS network services have different QoS classes for four types of traffic:

Conversational class (voice, video telephony, video gaming) Streaming class (multimedia, video on demand, webcast) Interactive class (web browsing, network gaming, database access) Background class (email, SMS, downloading)

UMTS will also have a Virtual Home Environment (VHE). It is a concept for personal service environment portability across network boundaries and between terminals. Personal service environment means that users are consistently presented with the same personalised features, User Interface customisation and services in whatever network or terminal, wherever the user may be located. UMTS also has improved network security and location based services.

9.3 UMTS ArchitectureA UMTS network consist of three interacting domains; Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core network is to provide switching, routing and transit for user traffic. Core network also contains the databases and network management functions.


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The basic Core Network architecture for UMTS is based on GSM network with GPRS. All equipment has to be modified for UMTS operation and services. The UTRAN provides the air interface access method for User Equipment. Base Station is referred as Node-B and control equipment for Node-B's is called Radio Network Controller (RNC).

It is necessary for a network to know the approximate location in order to be able to page user equipment. Here is the list of system areas from largest to smallest.

UMTS systems (including satellite) Public Land Mobile Network (PLMN) MSC/VLR or SGSN Location Area Routing Area (PS domain) UTRAN Registration Area (PS domain) Cell Sub cell


http://www.umtsworld.com/technology/ran/ran.htm


9.3.1User Equipment

The UMTS standard does not restrict the functionality of the User Equipment in any way. Terminals work as an air interface counter part for Node-B and have many different types of identities. Most of these UMTS identity types are taken directly from GSM specifications.

1) International Mobile Subscriber Identity (IMSI)2) temporary Mobile Subscriber Identity (TMSI)3) Packet Temporary Mobile Subscriber Identity (P-TMSI)4) Temporary Logical Link Identity (TLLI)5) Mobile station ISDN (MSISDN)6) International Mobile Station Equipment Identity (IMEI)7) International Mobile Station Equipment Identity and Software Number (IMEISV)

UMTS mobile station can operate in one of three modes of operation:PS/CS mode of operation: The MS is attached to both the PS domain and CS domain, and the MS is capable of simultaneously operating PS services and CS services.

PS mode of operation: The MS is attached to the PS domain only and may only operate services of the PS domain. However, this does not prevent CS-like services to be offered over the PS domain (like VoIP).

CS mode of operation: The MS is attached to the CS domain only and may only operate services of the CS domain.

9.3.2 Radio Access Network

Wide band CDMA technology was selected to for UTRAN air interface. UMTS WCDMA is a Direct Sequence CDMA system where user data is multiplied with quasi-random bits derived from WCDMA Spreading codes. In UMTS, in addition to channelisation, Codes are used for synchronisation and scrambling. WCDMA has two basic modes of operation: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). UTRAN interfaces are shown on UMTS Network page.

The functions of Node-B are:

Air interface Transmission / Reception Modulation / Demodulation CDMA Physical Channel coding Micro Diversity Error Handing Closed loop power control



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9.3.3Core NetworkThe Core Network is divided in circuit switched and packet switched domains. Some of the circuit switched elements are Mobile services Switching Centre (MSC), Visitor location register (VLR) and Gateway MSC. Packet switched elements are Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN). Some network elements, like EIR, HLR, VLR and AUC are shared by both domains.The Asynchronous Transfer Mode (ATM) is defined for UMTS core transmission. ATM Adaptation Layer type 2 (AAL2) handles circuit switched connection and packet connection protocol AAL5 is designed for data delivery.

The architecture of the Core Network may change when new services and features are introduced. Number Portability DataBase (NPDB) will be used to enable user to change the network while keeping their old phone number. Gateway Location Register (GLR) may be used to optimise the subscriber handling between network boundaries. MSC, VLR and SGSN can merge to become a UMTS MSC.

9.5 NETWORK PLANNING METHODSThis section includes a comparison of the different methods of analysis that could be carried out to analyze a UMTS network. It is important the we understand the differences betweenthese methods to understand:

their merits and demerits likely advantages of tools employing them

The aim of this section is to understand the alternatives and how/when they might be used.

There are basically two possible types of 3rd Generation planning methods Static Calculation

A deterministic algorithm is used to analyse the performance of the network configured within the planning tool.Repeating an analysis gives the same result.

Simulation Statistical processes and an iterative system status calculation used to analyse the performance of the network configured within the planning tool.Repeating an analysis may give different results.

9.5.1 Static CalculationStatic Calculation is a similar approach to that taken in ASSET for GSM planning. A statistical analysis of the network is used to derive design thresholds.



In UMTS the following mechanisms must be accounted for: Soft handover gain (typically ~5dB at the cell edge) Interference Margins (both intra cell and inter cell) Control and signaling overheads Fade Margins (to design to a given coverage probability) Special technique margins (Adaptive antennas, Transmit diversity, Smart Radio…)

9.5.2 SimulationThere are two types of simulation that might be used for radio planning

Static Simulations Static simulations analyse the performance of a ‘snapshot’ of the network. A snapshot is an instance in time, with UEs in statistically determined places. One or more snapshots of the network are taken. In each snapshot a mobile or terminal list is generated. The ability of each terminal to make its connection to the network is calculated through an iterative process. Various failure mechanisms will typically be considered (maximum mobile power, maximum Node B power reached, no available channels, low pilot Ec/Io, uplink/downlink interference). The performance of the network is then analysed from the results of the snapshots carried out.

Dynamic SimulationsDynamic simulations simulate UEs moving through the network in successive timeslots.Dynamic simulations look at mobiles moving through the network. A mobile list is generated and solved for the first timeslot. The simulation may consider time to be split into:

chip periods bit periods timeslots (SNR considered) Successive timeslots are then simulated dependant upon the results of the

previous timeslot. New mobiles are simulated coming into the network and terminating their calls.

9.6COMPARISON OF METHODS



STATIC ANALYSIS

STATIC SIMULATIONS

DYNAMIC SIMULATIONS

Not very – particularlywith global margins(IS-95 experience)

Reasonable – butdoesn’t deal with thedynamic networkperformance

Probably quite high -assuming no badassumptions aremade to speed it up

Accuracy

Relativelystraightforward to useonce configured

More difficult toconfigure and morecomplicated results.

Difficult to judgeResults.

Complexity

Shortest – as ‘quick’as for GSM.

Moderate –depending on numberof terminals .

Extremely long ifmultiple runsperformed forstatistical validity

TimeTaken

9.4 NETWORK ROLL OUT PROCESS For 3G



At the best of times, designing a cellular network is like doing a puzzle without any instructions. With 3G, you have the added complication of both the operator and customers holding back some of the pieces and planners having to force pieces to fit together because the edges are a bit rough!

Flow chart for the process


Create nominal plan

Site acquisition

Detailed site design

Site selection

Initial network dimensioning

Define search areas

Identify site option

Site construction


STEP 1: INITIAL NETWORK DIMENSIONING

This will be in most parts similar to previous cellular networks, but the difference will be that the main traffic type for the next five years is estimated to be medium to high speed data, not low speed (8-16 kbit/s) speech. Hence, new packet switched services conveyed by the GPRS/packet core network will have an effect on dimensioning.This step includes Spreadsheet sheet based analysis Identifies the maximum Number of sites required Identifies the approximate site radii required

Initial network dimensioning used as major input to the Nominal plan.

STEP 2: CREATE NOMINAL PLAN

The creation of a nominal plan involves the positioning of a hexagonal gridover the desired coverage area . When the radius of each hexagon can be determined, then it will be possible to attain an idea of the predicted capacity of the planned network. Following this, it will then be possible to detect any ‘hot-spots’ that may require cell splits and any under-utilized cells that may not be required and could possibly be removed. Cell splits can be particularly advantageous and can be a replacement for the omni-directional cell which has an antenna radiating equally in all directions with several directional antennas on the same mast.

STEP 3: DEFINING SEARCH AREASDue to the requirements of the system it is likely that for UMTS (3G)networks a larger number of sites will be required than with previous cellular networks. This has the effect of increasing the constant pressures of identifying smaller search areas, and consequently a reduction in the availability of suitable buildings within that area. In particular, council planners and property owners are far more concerned with the aesthetic issues for future developments than with the previous GSM cellular sites.

STEP 4: IDENTIFY SITE OPTIONS

Evaluation of both the radio coverage and the transmission back haulenabling the traffic to be relayed through the network should be performed, along with the selection of both a preferred and a back-up site choice, known as a site option. After these site options have been agreed, the site design elements must be considered; following this the site acquisition process can be started. It is highly advantageous in both time and cost if the acquisition agent and the site designer work in parallel as this can rule out any unfeasible sites with regard to structural suitability. This then means that when the options are presented they consist of three practical alternatives.



STEP5: SITE SELECTION

Site selection is basically a desk study. When performing the site selection various factors must be considered such acquisition, logistical issues, power availability, structural design and integrity, accessibility and aesthetics all the way to determine whether potential sources of high level radio frequency signal interference exist.

STEP6: SITE ACQUISITION Site acquisition services to telecom operators as a part of its services portfolio. Site acquisition service includes the following salient activities:Identify suitable land / roof top for locating the telecom infrastructure based on search rings provided.Collect ownership documents from land / site owners and verify with revenue authorities for ownership / encumbrance.Verify title and mother deed, tax dues and other liabilities on the land / site being acquired. Conduct legal verification of the Site with a legal counsel.Conduct lease rent and other terms negotiations on behalf of the Customer with the landlord.Assist the Customer in signing the leased deed including providing registration assistance, where required.

STEP7: DETAILED SITE DESIGN

Before construction of the site detailed site design is required. It includes the antenna and feeder requirements, equipment capacity requirements, antenna orientation and tilt requirements.



10.1COVERAGE PLANNINGThe link budget calculation for the WCDMA system and coverage planning for the GSM system have already been discussed. The fundamental process for coverage planning in the WCDMA system is quite similar to that of the GSM system. However, propagation models need to be adjusted to take into consideration the WCDMA technology. The cell range R can be calculated using the Okumara–Hata or the Walfish–Ikegami models. After this, the site are a can be calculated, which is 2.6R2. However, in the WCDMA networks, some additional measurements and adjustments were done in the framework of European Cooperation in the Field of Scientific and Technical Research, also called COST. The validity for this extended Okumara–Hata model is Frequency f: 150–2000 MHz Distance R: 1–20 km UE height : 10–200m MS height: 1–10mThis correction factor is added to obtain the actual losses in the WCDMA environment. Similarly for the Walfish–Ikegami model, the COST model is applied, which is based on the typical antenna placements and has the validity range

Frequency f : 800–2000 MHzBS height hbs: 4–50 mUE height hms: 1–3 mDistance d: 0.02–5 km

10.2 CAPACITY PLANNINGCapacity planning in WCDMA networks is much more complicated than in GSM/EGPRS. Factors that affect the coverage calculations are load, interference, traffic behaviour, speed of subscribers, etc.

10.2.1UplinkWCDMA is an interference system limited by the air interface. Hence, capacity planning would need to calculate the interference and the cell capacity, i.e. the amount of traffic that is supported by a base station. The amount of uplink interference has a great impact on the cell capacity and radius. The interference margin (η) indicates the total amount of interference (including thermal noise power) in comparison to the thermal noise: ηu = EbRN/WN0 (1 + i)νjwhereEb/N0 = signal energy per bit/noise spectral densityN = total number of users/cellR = bit rateW = chip ratei = other cell-to-own cell interferenceυj = activity factor of user j



10.2.2 DownlinkIn the downlink, the power transmitted by the BS is shared between all users. The capacity is determined by the power transmitted by the BS, locations of UE and interference. Thus, the parameters needed for downlink calculations include the power transmitted by BS and power allocation to the Common ControlChannel (CCCH). Thus, in downlink the capacity is determined by the power transmitted by the BS, locations of UE and interference. This makes the calculations in downlink more complicated than the uplink directions, for in the uplink each user has its own amplifier to transmit the power. Thus, coverage becomes a function of the number of users. In DL the own cell interference is reduced by the factor (1 − α). This is due to the synchronised orthogonal channellisation codes, which are used in DL. In the WCDMA system, the traffic can be asymmetric in the uplink and downlink directions and thus the load can also be different in either direction. The DL load is, however, higher than the UL load. The link performance also differs in either direction (the noise figure is higher for the UE than the BS). Soft handover heads are only in the DL direction. The load factor for different services has to be calculated separately. The total load is then the sum of different services in the cell area.

10.3 SOFT CAPACITY

The principle of soft capacity is that a cell can be more loaded when surrounding cells are unloaded. The less interference there is coming from all the neighbouring cells, the more users can be admitted before the load (interference or transmitted power) of a cell reaches the load target. If the average loading is low, there is extra capacity available in the neighbouring cells. As this capacity can be borrowed from the neighbouring cells, the interference sharing gives soft capacity. The soft capacity has more inpact on high bit rate real time users because of a larger relative change for higher bit rates.The soft capacity can be approximated based on the total interference at the BTS. The total interference includes that of both the own cells and other cells. Therefore, the total channel pool can be obtained by taking the number of channels per cell in the equally loaded case and multiplying that by 1 + i, which then gives the single isolated cell capacity.The basic Erlang B formula is then applied to this larger channel pool. This obtained Erlang capacity is then equally shared between neighbouring (interfering) cells by dividing the maximum offered traffic by 1 + i (in UL the power rise is also taken into account).From the planned load, the number of channels available in the resource pool (an average condition) can be calculated: NUL =ηUL(1 + i)(1 +W/R /Eb/N01/ν)

The soft blocking capacity (in Erlang) for RT services can be calculated using the Erlang B table and the equationSoft capacity/cell = Erlang B [N(1 + i) blocking %]/1 + I *[Erl]The DL soft capacity is calculated using a similar method.



10.4 FREQUENCY PLANNINGThe dilemma behind frequency planning is to provide needed capacity and coverage within a given frequency band. The frequency channels therefore need to be re-used, but it is wise not to increase the interference level. Interference is caused when two network cells use the same channel too close to each other; more precisely this is a co-channel interference situation. When the interfering channels are consecutive there is some neighbour channel interference, but this is less serious. The interference level cannot be high when building a functional network. The interference level increases with high transmission power in a close location. The frequency re-use rate is simplest to explain using a hexagonal model. Frequency re-use patterns are not used in practice because the cells are not hexagons, as already explained in the coverage planning section. The cell shapes are different and cells do not have equal sizes. Therefore the frequency re-use rate is not a constant throughout the network, but varies from one place to another and can also vary between BCCH and TCH layers. The available frequency band and the capacity plan give boundary conditions for the largest possible frequency re-use rate. Figure 2.27 shows two examples of the frequency re-use rate for hexagons. The first describes the re-use pattern for 7 cells and the second one the pattern for 12 cells.The following is an example of the connection between frequency and capacity planning. If the operator bandwidth is 6 MHz, the number of channels is 30. In general, frequency re-use affects the number of carriers that can be used for one sector. The number of carriers per sector can be calculated by dividing the available bandwidth by the product of the re-use rate and bandwidth for a single carrier, i.e. dividing the number of channels by the frequency re-use rate.

frequency reuse pattern



11.1 NOMINAL CELL PLANNINGAt the start of the rollout process nominal planning is just the rough outline of the network. The nominal plan builds on the dimensioning exercise. It is a hypothetical network with carriers and cell locations detailed. It involves using propagation models and terrain data. UMTS nominal plans require simulation to validate them. Nominal plan can be analyzed by ASSET TOOL.

SETTING UP ASSET FOR NOMINAL PLAN

11.2 CREATE A PROPAGATION MODEL

Propagation model : What is a propagation model?A mathematical model used by computerplanning tools to predict coverage from a radio transmitter.

Typical inputs 3D terrain data Land use data (Clutter) Building outlines Building heights

There are basically following types of propagation models : Statistical Deterministic Macrocell model

Statistical models:


Create UMTS propagation model

Import suitable antenna pateren

Create a nominal plan

Create UMTS cell layer


Carrier wave measurements are made from test transmitters.The measurements are plotted vs.log(distance).A straight line is fitted through the data.A basic y=mx +c formula can be used to estimate path loss.

The formula can be modified to account for other factors eg. Tx height, Rx height & terrain effects

Fig 11.1 DETERMINISTIC MODEL:

The planning tool traces rays from each site through an accurate 3D representation of an urban area. Typically a major component of the calculated path loss is free space loss.The effect of reflections diffraction and absorption due to buildings can be incorporated into the model.POPULAR MACROCELL MODELS:

Okumura -Hata

Industry standard. Not well suited for ranges under 1km.

Upper frequency limit 2GHz



Wave call

Not so well accepted. Fully deterministic no calibration required. Suitable for urban macro and microcells. Available for many common planning systems.

ADD A NEW PROPAGATION MODEL. Type - Standard macrocell Name 900MHz

‡Set up a propagation model with the default parameters.

Parameter Settings

Model type Standard microcell

Frequency cell 900

Mobile RX height 1.5

Effective earth height 8491.2

K1 135

K2 38

K3 -2.55

K4 0

K5 -13.82

K6 -6.55

K7 0.7

Effective antenna height Relative

Diffraction Epstein peterson

Merge knife edge 0

11.3 IMPORT THE ANTENNA PATTERNSsupplied by the manufacturers. For the purpose of this exercise several antenna patterns have been supplied.

An Omni



An 85º Sector

Fig 11.2 antenna pattern

11.4 CREATE COVERAGE SCHEMA & CELL LAYER

The only parameters that are necessary to set on the cell layer are the signal thresholds and thecoverage schema. These are derived from the link budgets used in the network dimensioning.

Fig11.3

11.5 CREATING A NOMINAL PLANFrom the link budgets, identify the cell radius for each environment to be planned.Create a UMTS site template



For each environment, position a hexagonal grid of sites with the appropriate cell radii over the target coverage area.

11.6 LOCATING URBAN NOMINAL SITESDefine mid hexagon radius as 1400m and select in the site template.

Fig 11.4 radius setting

Position a grid of sufficient sites to cover the urban areas



fig 11.5

11.7 LOCATING RURAL NOMINAL SITESDefine mid hexagon radius as 4000m and select in the site template.

Fig11.6

Position a grid of sufficient sites to cover the rural areas.



Fig 11.7

11.8 SPREAD VOICE TRAFFIC IN OVER THE AREA Spread the traffic on the voice terminal type.

Fig 11.8 traffic wizard



fig 11.8 graphical representation of voice traffic

11.9 SPREAD DATA TRAFFIC Spread the traffic on the data terminal type over the island.

Fig11.9 data traffic



12.1 PARAMETER PLANNING

Parameter planning is the task of optimising the parameters that control the behaviour of the network. Parameter planning does not usually involve modifying the physical equipment of the

network. The parameters with which we can modify the performance of the network in UMTS are mainly held within the RNC. As with GSM the user interfaces to the RNC are not defined within the 3GPP standards. This means that different vendors may have slightly different parameter sets, although there may be a lot of overlap. Many of those parameters detailed here are those suggested by the FRAMES project, 3GPP standards.

12.2 PHYSICAL LAYER PLANNING:

12.2.1 LOGICAL CHANNELSLogical channels were created to transmit a specific content. There are, for instance, logical channels to transmit the cell system information paging information or user data. Logical channels are offered as a data transfer service by the Medium Access Control (MAC) layer to the next higher layer. Consequently, logical channels are in use between the mobile phone and the RNC. Logical channels are characterized by the specific content to be transmitted: user data (DTCH), control messages (DCCH, CCCH), broadcast data (CTCH) and cell system information (BCCH).Control Channels (CCH)Broadcast Control Channel (BCCH)System information is made available on this channel. The system information informs the UE about the serving PLMN, the serving cell, neighbourhood lists, measurement parameters, etc.This information is permanently broadcast in the downlink.

Paging Control Channel (PCCH)Given the BCCH information, the UE can determine at what times it may be paged. Paging is required when the RNC has no dedicated connection to the UE. The PCCH is a downlink channel.

Common Control Channel (CCCH)Control information is transmitted on this channel. It is in use when there is no dedicated connection between the UE and the network. It is a bidirectional channel, i.e. it exists both in the uplink and downlink directions.

Dedicated Control Channel (DCCH)Dedicated resources were allocated to a UE. These resources require radio link management, and the control information is transmitted both uplink and downlink on DCCHs.



12.2.2 TRAFFIC CHANNELS (TCH)Dedicated Traffic Channel (DTCH)User data has to be transferred between the UE and the network. Therefore dedicated resources can be allocated to the UE for the uplink and downlink user data transmission.

Common Traffic Channel (CTCH)Dedicated user data can be transmitted point-to-multipoint to a group of UEs.

Common Packet Channel (CPCH)Similar to the RACH, it is a contention based uplink channel. In contrast to the RACH, it can be used to transmit larger amounts of (bursty) traffic.

Transport Channels (TrCH)The transport channels determine how the content is organised to be transmitted. The MAC layer uses the transport channels as service for the lower physical layer. The MAC layer is responsible for organizing the logical channel data on transport channels. This process is called mapping. The MAC layer determines the used transport format, the used cyclic redundancy check (CRC) length, channel coding (convolutional/turbo, coding rate), etc.

User Dedicated Channel (DCH), common (FACH/RACH)The MAC layer uses the transport service of the lower layer, the physical layer. The MAC layer is responsible for organising the logical channel data on transport channels. This process is called mapping. In this context, theMAC layer is also responsible for determining the used transport format. The transport of logical channel data takes place between the UE and the RNC.

12.2.3 DEDICATED TRANSPORT CHANNELSDedicated Channel (DCH)Dedicated resources can be allocated both uplink and downlink to a UE. Dedicated resources are exclusively in use for the subscriber.

Physical Channels (PhyCH)The physical layer offers the transport of data to the higher layer. The characteristics of the physical transport need to be described. When information is transmitted between the RNC and the UE, the physical medium changes. Between the RNC and Node B, where the interface Iub is discussed, the transport of information is physically organised in so-called frames. Between Node B and the UE, where the WCDMA radio interface Uu is found, the physical transmission is described by physical channels. A physical channel is defined by the carrier frequency number (UARFCN) and the spreading code (SC) in the FDD mode.

Primary Synchronisation Channel (P-SCH)The P-SCH uses the first 256 chips of every timeslot. In a P-SCH a primary synchronisation code is transmitted. This is done in every UMTS cell in every timeslot. If the UE detects the P-SCH it has performed chip synchronisation. The P-SCH (as well as the



secondary (S)-SCH) is not transmitted under the cell scrambling code, but uses its own predefined code, which is the same for all cells in the UMTS network.

Secondary Synchronisation Channel (S-SCH)The S-SCH also uses only the first 256 chips of a timeslot. In an S-SCH the secondary synchronization code is transmitted. There are 16 different secondary synchronisation codes that are organised into 64 different combinations. The 64 combinations are grouped with 64 scrambling code groups, each consisting of 8 scrambling codes.

Common Pilot Indication Channel (CPICH)CPICH carries a predefined bit/symbol sequence at a fixed rate (15 kbps, SF=256). It is used for channel estimation and for measurement of the neighbour cells. It is also used in an initial cell search to find the correct scrambling code of a cell. It is also used as the phase reference for most physical channels.

Primary Common Control Physical Channel (PCCPCH)PCCPCH is the physical channel that carries broadcast channel (BCH) information. It is a fixed rate channel without power control because it must be decoded by all the mobiles in the cell. The channelization code is fixed by specification and has SF = 256. The channel bit rate is 30 kbps but in order to reduce the total interference it is sent alternatives with the SCH giving a ‘net’ bit rate of 27 kbps. The PCCPCH does not have any pilot bits in the frame because the channel estimation is done using the CPICH.

Secondary Common Control Physical Channel (SCCPCH)SCCPCH carries two different common transport channels, the FACH (Forward Access Channel) and the PCH (Paging Channel). It is on air only when it has something to transmit. There can be up to three secondary CCPCHs configured. FACH and PCH can be mapped in two different physical channels. In addition, if the Service Area Broadcast (SAB) service is implemented it requires an additional SCCPCH.

Paging Indicator Channel (PICH)The Paging Indicator Channel (PICH) operates together with the Paging Channel (the transport channel is sent on the physical channel: SCCPCH). The paging indicator is sent on PICH, and the corresponding paging message is sent on the associated SCCPCH. Having one channel for indicators and one for messages provides terminals for an efficient sleep mode operation. The paging indicator (PI) uses a channelisation with SF = 256. Depending on the paging indicator ratio there can be 18, 36, 72 or 144 paging indicators per PICH frame. To each terminal registered to the network is allocated a paging group that corresponds to a PI. When the mobile detects the PI it decodes the next PCH frame transmitted on the secondary CCPCH. If the PICH is received with low reliability then the PCH is decoded. The less the mobile needs to listen to the PICH, the longer the battery life. The drawback is a longer response time for a mobile terminated call.

Acquisition Indication Channel (AICH)The AICH is a downlink physical channel with SF 256 in which an echo of the preamble RACH is sent from the WBTS (WCDMA BTS). The WBTS knows that there will be a message part



coming and starts to listen to the channellisation code indicated by the signature. At this point the WBTS does not have any information regarding the user.

Dedicated Physical Control Channel (DPCCH)The DPCCH has a constant bit rate and carries all information needed to keep a physical connection running. On the DPCCH the reference symbols (pilots) are sent for a channel estimation in coherent detection and for signal-to-interference ratio (SIR) estimation in fast power control. The power control signalling bits (transmission power control, or TPC) are also sent. The information of how data are coded is carried on the DPCCH and the Transport Format Combination Information (TFCI) is also sent as it contains information, for example, about bit rate and interleaving.

12.3 CONNECTION SETUP

Random Access ProcedureThe random access procedure is used to establish the RRC connection setup when the mobile wants to move from idle mode to connected mode or if the mobile is in connected mode (Cell FACH, Cell PCH, URA PCH) and it is to transmit information on uplink. The PRACH and AICH channels are involved in the PRACH procedure.In the random access procedure the UE sends a trial transmission burst called preamble. The transmission power of a preamble is estimated using open loop power control. If the mobile does not receive an indication from the BTS that it has received the preamble, the mobile will ramp up the transmission power and send another preamble. The power ramp-up step size is configuredby a parameter. Only after receiving confirmation on the AICH that the BTS has received the preamble does the mobile send the RACH message part. These is also an offset given in between the last preamblesent and the message part to guarantee reception of the message. As the RACH message is short no power control is used. The mobile sends a predefined number of preambles, ramping up power in between everystep. If the mobile has ramped up the power a predefined number of times and receives no confirmation from the base station, if starts the sequence from the begining and repeats it, but the sequence of ramping up the TX power is repeated only a predefined number of times. The UE will exit the random access procedure if it does not receive a response from the base station before it runs out the maximum number of times it is allowed to repeat the power ramp-up procedure. PRACH and AICH channels are structured to a 20 ms frame with 15 access slots. The PRACH frame is divided into two access slot sets: access slot set 1 (access slots 0 to 7) and access slot set 2 (access slots 8 to 14).



Random Access Procedure: Preamble and MessageThe preamble is 4096 chips long. It consists of 256×16 chip signatures. There are 16 possible signatures in each cell. The uplink scrambling code of a cell is selected from 16 dedicated UL scrambling codes. The RACH message consists of one or two radio frames (10–20 ms). The scrambling code number is the same as that used for the preamble. The message part can have different spreading factors. The spreading factor is based on a selected signature and spreading factors between 256 and 32 can be used.

Random Access Procedure: AICHEach acquisition indication channel (AICH) slot carries a separate acquisition indication for each signature (total 16). The acquisition indication has three different values:

0, no indication →the BTS has not received this signature; 1, positive indication →the UE is allowed to transmit a message; 1, negative indication →the UE must exit the RACH procedure.

Each slot contains a 32 symbol waveform, which is scrambled with the cell primary scrambling code.

Random Access Procedure: UE Required InformationThe preamble scrambling code is transmitted on the BCCH (SIB5), based on the parameter. The allowed signatures are based on theBCCH(SIB5) and the UE Access Service Class (ASC). For each preamble one of the allowed signatures is randomly selected. The UE is allowed to transmit the preamble on PRACH access slots based on the BCCH (SIB5) and the UE ASC. For the first preamble one of the allowed access slots in the next full access slot set (1 or 2) is randomly selected. For re-transmission the first allowed access slot is selected.

12.4 PAGING PROCEDURES

The paging procedure uses two physical channels. The paging indication (PI) is sent over the paging indication channel (PICH). The paging indication shows that the UE should read the corresponding message on the secondary common control physical channel (SCCPCH).



OverviewThe paging procedure is required to enable the network to contact the UE in idle mode or when in connected mode the Cell PCH and URA PCH states. In idle mode the UE is paged over the whole location area (LA) in the case of CS paging or the routing area (RA) in the case of PS paging. This means that in idle mode the paging indication and message is sent on all cells belonging to the LA or RA. In connected mode the UE is paged over one individual cell if the UE is in the Cell PCH state or over the UTRAN registration area if the UE is in the URA PCH state.There are three sources that might start a paging procedure:

the circuit switched core, if the UE is registered but not connected; the packet switched core, if the UE is registered but not connected; the RNC in the case where the UE is in the CELL PCH and URA PCH states.

The paging procedure has two phases: the UE detects an indication on the PICH and the UE decodes the paging message from the SCCPCH and checks whether is for that UE. Cells can have one or more SCCPCHs configured. There can be one SCCPCH dedicated to carry paging.

12.5 HANDOVER CONTROLWCDMA networks have large numbers of different types of handovers taking place compared to GSM networks. A distinctive feature of a WCDMA system is the introduction of a soft handover (SHO) – a situation where the UE is connected to two or more sectors simultaneously. A special case of a soft handover is a softer handover, where the UE is connected to two or more sectors from the same Node B. An intrafrequency hard handover is also possible in the case where an SHO is not possible. Usually an intrafrequency handover is used as the ‘last chance’ in the case where an SHO is not possible. If neither an SHO nor an intrasystem hard handover is possible, but there are measurement reports confirming that a neighbour cell Ec/I0 is stronger than a serving cell, a forced RRC connection release takes place. In the case of a lack ofWCDMAcoverage, poor Ec/I0, quality deterioration reports from the outer loop power control function or high transmit power from either theUEor WBTS, interfrequency or intersystem handover is triggered. The interfrequency and intersystem handovers require measurements on another frequency band. If the UE is not designed with a dual receiver the needed performing measurements require compressed mode. In compressed mode the continuous transmission of theWCDMAis interrupted and transmission gaps are used to perform measurements on another frequency band. If a neighbouring cell is found and decision criteria are fulfilled the interfrequency or intersystem handover is performed.

Different Types of WCDMA Handovers FDD soft/softer handover (intrasystem intrafrequency HO) FDD interfrequency (intrasystem interfrequency HO) FDD/TDD handover (intersystem HO) TDD/FDD handover TDD/TDD handover Handover WCDMA–GSM (intersystem HO) Handover GSM–WCDMA (intersystem HO)



A specific (soft) handover situation is a crossing of an RNC border, when serving RNC resources need to be relocated.Measurement TriggeringImplementation of different measurement triggering criteria in the network is vendor specific. Possiblemeasurement triggering criteria include:

Best active set cell RSCP (UE measurement report) Best active set cell Ec/N0 (UE measurement report) Uplink DCH quality (RNC measurement) Downlink DCH quality (UE measurement report) Cell load (RNC measurement) Distance UL TX power (UE measurement report) DL TX power (BTS measurement)

12.6 MEASUREMENT CONTROLIn a measurement control the RNC sends measurement parameters to the UE to command how measurementsare done. The UE then performs measurements and reports according to measurement reporting criteria. The measurement control for the interfrequency and intrasystem handover triggering mechanism is similar. There are different parameters for each type of handover, but the measurement triggering and measurement control functionality works in a similar manner. The interfrequency and intrasystem measurements require the compressed mode. The measurements on an adjacent carrier are done during the transmission gaps. The possible control parameters include the reporting interval, the number of measurements the mobile is allowed to make and penalty timers after an unsuccessful interfrequency handover (IFHO) or intrasystem handover (ISHO) attempt.

12.7 HANDOVER DECISION CRITERIAThe RNC commands handover when the handover criteria are fulfilled, but there can be different decision procedures depending on the triggering criteria. For example, if the triggering condition Ec/I0 of the serving cell is poor the target cell Ec/I0 is ranked against the serving cell, but if the target cell is better the RNC commands IFHO to take place. In the case where the source cell RSCP falls below the triggering condition the handover decision algorithm compares the source and target cell RSCPs. The RNC commands handover when the handover criteria is fulfilled.

12.8 CONNECTED MODE12.8.1 Power ControlTransmission power is one of limiting resources of the WCDMA system. Common channels (CCHs) are transmitted with fixed output power and the power control algorithm minimizes the transmission power for dedicated channels. The common channels are transmitted with fixed output power. They consume a fixed amount of transmission power resources. It can be seen in the example in Figure 2.43 that the used transmission power recourses for common channels can only take 6Wout of the 20Wtotal transmission power available in the WBTS.



12.8.2 Power Control AlgorithmsPower control algorithms minimise the transmission power used for dedicated channels. The closed loop power control adjusts the transmission power.

12.8.3 Fast Closed Loop Power ControlThe closed loop power control adjusts the transmission power 1500 times a second to keep the power at the minimum required level. The closed loop power control uses the signal-to-interference ratio (SIR) to adjust the transmission power. It measures the SIR independently for each connection and adjusts the transmission power an every timeslot basis. The measured SIR is compared with the SIR target. If the target is not reached the transmission power is increased; otherwise the transmission power is decreased. In the downlink direction all the NodeBs participating with the SHO connection measure their SIR and determine their power control command. They independently adjust their transmission power according to the power control commands (TPC) received from the UE.

To determine the power control command in the uplink direction there is an SIR target set for each cell in the active set. The UE lowers its transmission power when all the SHO connections fail to reach the SIR target. This means that transmission power is increased only if all connections are below the set SIR target.

12.9 OUTER LOOP POWER CONTROLThe outer loop power control algorithm adjusts the signal-to-interference ratio (SIR) target. The SIR target is used by the closed loop power control as a reference value for transmission power adjustments. The outer loop power control measures the block error rate (BLER), indicating the transport channel quality. There are individual BLER targets set for each transport channel; if the BLER target is not reached, at least for one of the transport channels, the outer loop power control increases the SIR target for the dedicated physical channels. Adjustment of the SIR target would make the closed loop power control algorithm adjust the transmission power of the dedicated physical channels. There are independent outer loop power control entities in both the uplink and downlink directions. The outer loop power control entity in the UE receives the BLER target, the initial SIR target and the minimum and maximum values for the SIR target in the radio bearer configuration message.

12.10 PACKET DATA CONNECTIONPacket data is one example of non-real-time service. As currently the applications using packet data vary from email client, Internet surfing to music download the services use the packet data connection. Depending on the service requirements (QoS), the corresponding physical resources are allocated. In contrast to the real time services, the packet data as non-real-time services can momentarily lower their bit rate. Also in a case of inactivity the service can use common channels (Cell FACH) to transmit small amounts of data or can, in the case of inactivity, use the idle mode, as in packet transfer states (Cell PCH or URA PCH) where no data are transferred.Downgrading the bit rate for a packet data connection takes place when the network is having a high load, and resources used by non-real-time services are needed for real time users or higher priority non-real-time services. The target and overload thresholds define the operating space of



the packet scheduler – the RRM functionality that controls allocated packet data bit rates. In the case of an overload situation packet data services are downgraded until the measured load reaches the load target. If the load is on a marginal load area no action is taken as the non-real-time services are not allowed to be upgraded and no downgrading takes place. On a feasible load area packet data services are upgraded if there is a capacity request indicating that one or more non-real-time services requires more capacity.

12.11 HANDOVER PARAMETERSThis type of parameter, also called handover control (HOC) parameters, is tuned on a cell basis. It means that cell by cell a different value can be set for a given parameter. Those parameters have the specificity to be cell dependent (e.g. a parameter that sets the level threshold in the downlink in order to perform an outgoing handover with a level cause). According to the handover algorithm, each parameter and its usability can be described explicitly.

ENABLABILITYMost of the handover types described above are triggered only if they are enabled by setting the ‘enable HO’ parameter to ‘yes’. Otherwise they do not occur.PERIODICITYSome parameters drive in terms of SACCH intervals the time difference between two successive similar handover events, such as handover attempts, handover failures, power budget and umbrella handovers.PRIORITYIn a lot of handover mechanisms, prioritisation is important in the selection of a target cell for handover. It is based on giving more priority to cells experiencing less traffic load. This issue is driven by threemain parameters:

a threshold in percentage starting from what a cell is considered as loaded; a load factor that gives in units the offset to apply to overloaded cells; a priority level that ranks primarily all of the adjacent cells.

The algorithm is simple. The final priority to rank adjacent cells is equal to the primary priority decreased by the load factor for cells loaded with more than the load threshold. At the end, cells with a high traffic load have the lowest priority and handover is then commanded to cells with no load.AveragingAveraging is important to prevent repetitive handover attempts between two cells. Four parameters drive the process:

Window size gives the number of measurements that should be averaged. Weight indicates the importance given to the last measurement in the averaging formula. Nx is the total number of averaged samples that are to be considered. Px is the required number among the Nx samples that should fulfil the criterion before a

handover can be triggered.

Thresholds



Once the network performs averaging, it compares the Nx samples to a given threshold. Depending on the type of handover (quality, level or interference, for example), there is a special criterion that Px samples should meet before the handover is initiated. Level and interference thresholds are in the ‘RXLEV’ terms whereas the quality threshold is given as ‘RXQUAL’ values.

12.12 LAYER PARAMETERSLayerThis defines the nature of the layer relationship from the source cell to the target cell. It can take one of four values (same, lower, upper, not used).Power Budget MarginThis gives in dB how much the signal level of the target cell should exceed that of the source cell to perform a PBGT handover.Fast Moving ThresholdThis indicates the time (in SACCH frames) that a mobile should stay in a cell’s coverage before deciding to hand it over to this lower layer cell.Umbrella LevelThis is the minimum acceptable level threshold that a mobile should measure to decide whether it is still in the cell’s coverage area. At the end, hundreds of parameters exist that handle handover and adjacency. Each one can be tuned separately according to the optimisation need. The parameter tuning section deals with some examples of handover control parameter tuning.

12.13 POWER CONTROL PARAMETER:There are two different levels of power control in UMTS

Outer Loop Power Control Inner Loop Power Control

Outer Loop The purpose of the Outer Loop power control is to set and adjust the Eb/No target for the service dependant upon the achieved BER/FER. The BER/FER target will be associated with the serviceItself. However it may be possible to set.

The Measurement Frequency. The Sampling Period

Inner LoopThe purpose of the Inner Loop power control is to achieve the target Eb/No over the air interface.The inner loop power control is dependant upon which of two algorithms are used.

Algorithm 1A single power control bit is used to indicate a power rise/lower

Algorithm 2 A set of five power control bits are used, preceded by a series of 4 zero valued bits. Only if all bits indicate a power rise/lower is the power modified.



INNER LOOP PARAMETERS:

12.14 PILOT POWER PLANNING

By Pilot Planning we are referring to planning the power ofthe Pilot Channel.Other control and signaling channels will typically betransmitted at a fixed offset from the pilot.The Pilot itself is used:

To add cells to the active set in handover. To set the maximum extent of the cell. To allow for channel estimation at the receiver.

12.15 CODE PLANNING

Code Planning is required for the downlink scrambling codes and downlink secondary synchronization codes. The objective of code planning is to ensure:

that code reuse is as efficient as possible that we can maximize the minimum reuse distance between sites sharing the same

scrambling codeThere are 512 downlink scrambling codes that we can use. At an average of 3 codes used per site this implies a reuse of 170!



BIBLIOGRAPHY:

1.) NETWORK AND RF PLANNING BY ERICSSON2.) SITE DESIGN BY AIRCOM3.) NOMINAL PLANNING BY AIRCOM.4.) CELL PLANNING PRINCIPLES BY ERICSSON5.) WWW.SCRIBD.COM 6.) UMTS NETWORK PLANNING AND DEVELOPMENT


http://WWW.SCRIBD.COM/

kapil....network rollout for 2g & 3g

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