Omni Antenna Signal Pattern (Signal Propagation Shape)

Sectorize Antenna Signal Pattern (Signal Propagation Shape)

3 Dimension Sectorize Antenna Signal Pattern

Sector Antenna Signal Pattern

Antenna Specification

UMTS RRU

UMTS BBU

Fiber Optic

RRU Board Coonection

Outdoor NodeB

UMTS and Radio Access Bearer Services

Stand-alone RABs RAB combinations

Traffic Class RAB Configuration

Signaling Radio Bearer

SRB for BCCH

SRB for PCCH

SRBs fo BCCH, CCCH and DCCH (FACH)

SRBs for CCCH and DCCH (RACH)

13.6/13.6kbps SRB for DCCHConversational Speech 12.2 kbps RAB

64 kbps CS RAB

Interactive64/64 kbps PS RAB64/128 kbps PS RAB64/384 kbps PS RAB

Streaming 57.6 kbps CS RAB8/54 kbps PS RAB + Interactive 8/8 kbps PS RAB

Mixed Conversational/Speech 12.2 kbps RAB + Interactive 64/64 kbps PS RAB

Mapping of UMTS services to RABS

The CN will map the UMTS service to the RABs as shown in Table 2-1 below.

For dimensioning purposes we only consider the services listed in Table 2-2 below.

Service Type

Speech 12.2 kbps RB + 3.4 kbps SRB

64 kbps CS RB + 3.4 kbps SRB

64 kbps PS RB + 3.4 kbps SRB

Streaming 57.6 kbps CS RB + 3.4 kbps SRB

Streaming 16 kbps PS RB + 8 kbps PS RB + 3.4 kbps SRBPS Streaming rate restricted to 16 kbps

PS 1 rate is restricted to 64 kbps

It should be noted that the PS streaming RAB cannot exist as a standalone RAB but must be combined with an interactive bearer. Since we only dimension the Radio Network for the BH two assumptions may be made:1) PS Streaming rate restricted to 16 kbps2) The maximum PS rate is restricted to 64 kbps

BH

Assum

ptions

Logical Channel

The MAC layer provides data transfer services on logical channels, Logical channels are classified into two groups:

• Control channels for the transfer of control plane information • Traffic channels for the transfer of user plane information

Transport Channels

A transport channel is defined by how and with what characteristics data is transferred over the air interface. There exist two types of transport channels

• Dedicated channels;• Common channels,

There is one dedicated transport channel, the dedicated channel (DCH), which is a downlink or uplink transport channel. The DCH is transmitted over the entire cell or over only a part of the cell using beam-forming antennas. The DCH is characterized by the possibility of fast rate change (every 10 ms), fast power control, and inherent addressing of mobile stations.

Mapping Between Logical Channels and Transport Channels

PHYSICAL CHANNELS

The transport channels are channel coded and matched to the data rate offered by physical channels. Thereafter, the transport channels are mapped on the physical channels. Physical channels consist of radio frames and time slots. The length of a radioframe is 10 ms and one frame consists of 15 time slots.

Uplink Physical Channels

There are two uplink dedicated physical and two common physical channels:• The uplink dedicated physical data channel (uplink DPDCH) and the uplink dedicated physical control channel (uplink DPCCH);• The physical random access channel (PRACH) and physical common packet channel (PCPCH).

Downlink Physical Channels

There is one downlink dedicated physical channel, one shared and five common control channels:• Downlink dedicated physical channel (DPCH);• Physical downlink shared channel (DSCH);• Primary and secondary common pilot channels (CPICH);• Primary and secondary common control physical channels (CCPCH);• Synchronization channel (SCH).

PACKET SESSION

A packet session begins when a user is actively transmitting or receiving data in such volume that it requires a dedicated channel. The session ends when there is no more data to transmit and the connection is transferred to a common channel. During the session the user may be switched up or down in data rate due to channel switching, as illustrated in below Figure.

There are periods of silence in between transmission where the dedicated channel is still allocated, but only the control channel is active. This may be due to either the protocol waiting for an acknowledgement or if there is no data to send. This bursty behavior is typical of a packet application

The session length is defined from the time a dedicated channel is allocated to the time where the channel is released and the user is disconnected or moved to a common channel.

Packet Call showing Session throughput and THold

Packet Traffic Assumptions

End user application RAB mapping

Call per 24h Sessions per packet call

KB per request UL

KB per request DL

Web traffic with image BE 64/64 3 10 2 40

Web traffic without image BE 64/384 3 10 1 20

Web traffic, minibrowser BE 64/384 3 10 .2 1

Sending mail with attachment BE 64/384 5 1 200 20

Sending mail without attachment BE 64/384 5 1 5 .5

Receiving mail with attachment BE 64/384 5 1 20 200

Receiving mail without attachment BE 64/384 5 4 .5 5

Point of sale (Telemetry) BE 64/384 120 1 1.2 1.2

ENERGY PER BIT TO NOISE RATIO (EB/NO)

Air Interface noise producing bit errors

The bit error rate is proportional to ratio of energy per bit (Eb) to noise power density (No). This ratio is realistically and conceptually illustrated in Figure 3-2 below.

Realistic and conceptual illustration of Eb/No

Figure 3-1 below illustrates how noise introduced by the air interface produces bit errors in the received data stream.

New Additional Slide

CAPACITY REQUIREMENTS

As with the coverage requirements, the capacity requirements will grow in phases. Table below, shows a typical example of the number of subscribers attached to an operator’s 3G network in the busy hour (BH).

Example Network Subscriber numbers

The subscriber BH traffic profile for Circuit Switched (CS) must be calculated from the given requirements in terms of:• Average data rate per user (kbps)• Blocking rate/probability (Grade Of Service –GOS)• Busy Hour Call Attempts (BHCA)• Average Call duration in minutes

CS Traffic Profile Example

CS Traffic Profile

The subscriber BH traffic profile for Packet Switched (PS) should be given in terms of:• BH UL+DL data volume per subs (kbit)• Ratio uplink/total traffic• Average BH number of active Packet Data Protocol (PDP) contexts per user

PS Traffic Profile Example

PS traffic profile

SERVICE REQUIREMENTS

The types of service offered must be given. For each area, the estimated usage of each service should also be given. The services are characterized by the QoS (Quality of Service) parameter related to different radio access bearer attributes. The main attributes to define a service are bit rate, transfer delay, Bit Error Rate (BER) and BLock Error Rate (BLER). The areas with different coverage reliability should be distinguished todetermine which service could be guaranteed.

The services that are available in the P3 radio network are listed below:• Speech• CS 64• CS 57.6 Streaming• Interactive PS 64/64• Interactive PS 64/128• Interactive PS 64/384• PS Streaming (combination of streaming and interactive)• Multi-RAB (combination of speech and interactive)

NOMINAL CELL PLAN

Cell Classification table

Cell illustration

WCDMA Traffic

ObjectivesUpon completion of this module, the student will be able to:• Explain the UMTS and Radio Access Bearer (RAB) Concept• Explain the four different Traffic classes• List the RABs supported by the P3 WCDMA RAN• Explain how UMTS Bearer Services are mapped onto RABs• Explain the principle of Circuit Switched (CS) and Packet Switched (PS) dimensioning• Explain how best effort applications can be included in traffic calculations

For the purpose of network dimensioning, it is necessary to estimate the amount of traffic that is carried in the Busy Hour (BH) of a system.

The purpose of a Radio Access Bearer (RAB) is to provide a connection segment using the UMTS Terrestrial Radio Access Network (UTRAN) for support of a UMTS bearer service. The UTRAN can provide Radio Access Bearer connections with different characteristics in order to match requirements for different UMTS bearers.

RADIO ACCESS BEARERS (RABS)

UMTS and Radio Access Bearer Services

For the purpose of network dimensioning, it is necessary to estimate the amount of traffic that is carried in the Busy Hour (BH) of a system.

The purpose of a Radio Access Bearer (RAB) is to provide a connection segment using the UMTS Terrestrial Radio Access Network (UTRAN) for support of a UMTS bearer service. The UTRAN can provide Radio Access Bearer connections with different characteristics in order to match requirements for different UMTS bearers.

Stand-alone RABs RAB combinations

RABS SUPPORTED BY RAN

Traffic Class RAB Configuration

Signaling Radio Bearer

SRB for BCCH

SRB for PCCH

SRBs fo BCCH, CCCH and DCCH (FACH)

SRBs for CCCH and DCCH (RACH)

13.6/13.6kbps SRB for DCCHConversational Speech 12.2 kbps RAB

64 kbps CS RAB

Interactive64/64 kbps PS RAB64/128 kbps PS RAB64/384 kbps PS RAB

Streaming 57.6 kbps CS RAB8/54 kbps PS RAB + Interactive 8/8 kbps PS RAB

Mixed Conversational/Speech 12.2 kbps RAB + Interactive 64/64 kbps PS RAB

Mapping of UMTS services to RABS

The CN will map the UMTS service to the RABs as shown in Table 2-1 below.

CIRCUIT SWITCHED DIMENSIONING

Cellular system capacity depends on a number of different factors. These include:• Number of channels available for voice and/or data• GoS the subscribers encounter in the system

Traffic theory attempts to obtain useful estimates, for example, the number of channels needed in a cell. These estimates depend on the selected system and the assumed or real behavior of the subscribers.

Traffic (A) = BHCA X MHT Where: BHCH = Busy Hour Call Attempts MHT = Mean Hold Time (in hours)

CS Traffic Calculation Example

AVERAGE CS TRAFFIC PROFILE

The Average traffic profile must be calculated for dimensioning purposes. The BH traffic per sub for the CS services is given in Equation below:

BH Traffic per sub (mE) = A X Weighting factor

The weighting factor is required in cases where the number of subscribers using the different services is not the same.Weighting factor = No. of subs for service/No. of UMTS subscribers

Average CS Traffic Profile Example

Calculate the BH traffic per sub for the services in Table 2-4 below

No of UMTS Subscribers 15000

No of Speech Subscribers 15000

No of CS Data Subscribers 1500

BS Speech Traffic 19.6

BH CS Traffic 10.8

OFFERED TRAFFIC AND GOS

This leads to the definition of ‘Offered Traffic’, which is defined as the number of subscribers multiplied by the traffic per subscriber as shown in Equation below:

Offered Traffic = number of subs X traffic per sub

Offered Traffic

If the ‘Offered Traffic’ for a system (or sector) is known, once the ‘Actual Traffic’ is measured the Grade of Service can be calculated using Equation below:

PACKET SWITCHED DIMENSIONING

A packet call starts when a connection switches from the idle mode to one of the active states, and ends when the connection is switched back to the idle mode or when the UE is turned off. A packet call can consist of several sessions. In many cases traffic and average data rates are given based on a packet call. It is useful to convert this type of data to traffic based on sessions, since that is what will determine the interference as well as the hardware requirements for the radio access network.

There are periods of silence in between transmission where the dedicated channel is still allocated, but only the control channel is active. This may be due to either the protocol waiting for an acknowledgement or if there is nodata to send. This bursty behavior is typical of a packet application.

PACKET SESSION

A packet session begins when a user is actively transmitting or receiving data in such volume that it requires a dedicated channel. The session ends when there is no more data to transmit and the connection is transferred to a common channel. During the session the user may be switched up or down in data rate due to channel switching, as illustrated in Figure below.

The session length is defined from the time a dedicated channel is allocated to the time where the channel is released and the user is disconnected or moved to a common channel.

Session throughput and Thold are illustrated in Figure below.

SESSION LENGTH (HOLDING TIME THOLD)

PACKET THROUGHPUT

Throughput is defined as the perceived user data rate from the application layer. This means that the throughput will never reach the peak rate, since the TCP and IP overhead, plus retransmissions, have to be taken into account. The throughput can be expressed per session, per bearer or per cell

Packet Call showing Session throughput and THold

PACKET TRAFFIC ASSUMPTIONS

End user application RAB mapping

Call per 24h Sessions per packet call

KB per request UL

KB per request DL

Web traffic with image BE 64/64 3 10 2 40

Web traffic without image BE 64/384 3 10 1 20

Web traffic, minibrowser BE 64/384 3 10 .2 1

Sending mail with attachment BE 64/384 5 1 200 20

Sending mail without attachment BE 64/384 5 1 5 .5

Receiving mail with attachment BE 64/384 5 1 20 200

Receiving mail without attachment BE 64/384 5 4 .5 5

Point of sale (Telemetry) BE 64/384 120 1 1.2 1.2

AVERAGE PS TRAFFIC PROFILE

Average PS Kbyte in BH = Kbyte in BH X Weighting factor

For dimensioning purposes it is necessary to calculate the average PS traffic profile per sub, for the BH.The BH average KB per sub is given in Equation below:

The Weighting factor is required in cases where the number of subscribers using the PS services is different from the total UMTS subscribers

Weighting factor = No. of subs for service/No. of UMTS subscribers.

REQUIRED PACKET SESSIONS

Once the required subscriber data rate is known, the number of packet sessions (Mdata) needed to achieve this rate can be calculated using Equation below.

Where:Req rate = required sub data rate [bps] bit_rate = Packet Session bit rate [bps] (In the BH this can be assumed to be 64 kbps)

PEAK FACTOR

For the purposes of Radio Network dimensioning we could assume that each packet channel will only carry 0.7

packet sessions due to the peak factor. If however, we are calculating the number of packet channels (Mdata) needed to carry a

requested number of packet sessions (Mdata) we should increase the number of channels required by 1/0.7 = 1.4.

The number of packet channels (Mdata) needed to support the required packet sessions given by Equation below:

Required packet channels

Where:Peak_Factor = Factor to account for channel sharing (1.4 is assumed for calculation purposes)Mdata = required packet sessions

3GPP CHANNEL MODELS

The 3GPP specify a number of different channel models to be used for radio network design. These specify the environment and speed of the UE.

These models are designed to cover the scenarios shown in Figure below.

The uplink pole capacity, Mpole, is the theoretical limit for the number of UEs that a cell can support. It is service (RAB) dependent. At this limit the interference level in the system is infinite and thus the coverage reduced tozero. .

UPLINK MAXIMUM NUMBER OF CHANNELS (MPOLE)

Service Type Dense Urban / Urban

Suburban Rural

Conversational/Speech 12.2 Kbps RB + 3.4 Kbps SRB 78 66 65Conversational 64 Kbps CS RB + 3.4 kbps SRB 18 15 14Interactive 64 kbps PS RB + 3.4 kbps SRB 19 16 15Streaming 57.6 Kbps CS RB + 3.4 Kbps SRB 22 19 20Streaming 16 kbps PS RB + 8 kbps PS RB + 3.4 Kbps SRB 36 27 30

Uplink max Subscriber per cell per service (Mpole)

Uplink Limited Capacity : (Uplink Mpole Values)

Service Type Dense Urban / Urban (TU- 3)

Suburban(TU-50)

Rural (RA)

Conversational/Speech 12.2 Kbps RB + 3.4 Kbps SRB 59 54 53

Conversational 64 Kbps CS RB + 3.4 kbps SRB 7.3 6.6 6

Interactive 64 kbps PS RB + 3.4 kbps SRB 8.5 7 7.2

Interactive 128 kbps PS RB + 3.4 kbps SRB 5 4.4 4.2Interactive 384 kbps PS RB + 3.4 kbps SRB 1.4 1 1.3Streaming 57.6 Kbps CS RB + 3.4 Kbps SRB 10 10 10

Streaming 64 kbps PS RB + 8 kbps PS RB + 3.4 Kbps SRB 9.9 8.2 8.3

Downlink max Subscriber per cell per service (Mpole)

Downlink Limited Capacity : (downlink Mpole Values)

Conversational traffic has priority over packet (best effort) traffic. Therefore the best effort load is the remaining system load available on top of the conversational load, as illustrated in Figure below.

TRAFFIC Load CALCULATIONS of WCDMA Cell

The maximum load (Qmax) is defined as the conversational load (QC) plus the best effort load (QBE) as shown in Equation below.

To calculate the BE (Best Effort) required channels for PS using below equation

Where the load per subscriber is:

Conversational load (Qc) = traffic_per_sub_CS/max possible conversational channelsBest Effort load (QBE) = BE_CH_Req/max possible packet channels

ExampleA cell is required to provide service to 1000 subscribers with the traffic requirement in table below:

Assuming a peak factor of 1.4 and that only the PS64 bearer is available, what is the maximum uplink load if the maximum possible number of conversational and packet channels is 78 and 19 respectively

UPLINK LOAD SOLUTION

Step 1: Calculate the BE required channels using

BE_CH_Req = (40 X 1024 X 8 X 1.4)/(3600 X 64 X 103 ) = 0.001991

Step 2. Calculate the Best Effort load (QBE ) QBE = 0.001991 / 19 = 0.00010479

Step 3. Calculate the Conversational load (QC) QC = 25 x 10 -3 / 78 = 0.0003205

Step 4. Calculate the Maximum load (Qmax) using equation 10:

Qmax = 1000 ( QC + QBE ) = 0.4253

Answer : The uplink load is 42.53 %

Cell breathing

Coverage/capacity versus distance (1)

- High bitrates = high power,- High transmission bitrates only available close to the base station.

NETWORK ELEMENTS CAPACITY OVERVIEW

Dedicated Channel

Node-B RNC CN

UE

Uu

Common Channel

Traffic Channel

Traffic Channel

Control Channel

Control Channel

MAC

Iub Iu

Logical ChannelLogical Channel

Physical Channel

Radio Channel Layers In UMTS