Mobile Wimax- RF planning

A good RF plan should address the coverage and capacity requirement ofthe area considered, but also be sufficiently flexible to allow network expansion without major change of the existing sites.

As with any communication network, the cornerstones of the RF planning process are:

Balancing coverage, quality, and capacity Minimizing costs and complexity

To design a network that successfully addresses these basic tenets of network planning, we need to create an accurate model of the radio propagation and of the subscriber traffic. The accuracy of the network model is highly dependent on the accuracy of the data we use as the foundation of the project are given below.

Up-to-date geodata (Clutters, Heights & Vectors files) Accurate and up-to-date survey data (BTS latitude & Longitude,

heights and etc)

Tuned propagation models that are appropriate for the environment and data

Accurate and up-to-date site configuration information( Orientations ,tilt, Power, CPE and etc

Model tuning (CWR Test analysis)

Mobile Wimax RF Optimization

Network optimization can initially be seen as a very involving task as a largenumber of variable are available for tuning impacting different aspect of thenetwork performance

Even after careful RF planning, the first step of optimization should concentrate on RF. This is necessary as RF propagation is affected by so many factors (e.g., buildings, terrain, vegetation…) that propagation models are never fully accurate.

RF optimization thus takes into account any difference between predicted and actual coverage, both in terms of received signal (RSCP) and quality of the received signal (Ec/No). In addition, the same qualitative metrics defined for planning should be considered: cell overlap, cell transition, and coverage containment of each cell. At the same time, assuming that a UE(User equipment) is used to measure the RF condition in parallel with a pilot scanner, reselection parameters can be estimated considering the dynamics introduced by the mobility testing.

• During network planning dynamics cannot be considered, as network planning tools are static by nature, only simulating at one given location at a time, irrespectively of the surrounding. In addition, once the RF conditions are known, dynamic simulation can be used to estimate the handover parameters, even before placing any calls on the network.

Service optimization is needed to refine the parameter settings (reselection,access, and handover). Because the same basic processes are used for alltypes of services, it is best to set the parameters while performing the simplerand best understood of all services.

This is fully justified when the call flow difference for the different services are considered. Either for access or for handover, the main differencebetween data and other service is the resource availability.

Different set of parameters are likely to be tried to achieve the best possible trade-offs:

• Coverage vs. capacity,• Data access (Mobile Originated and Mobile Terminated)• Reliability vs. call setup latency,• Data retention vs. Active Set size... to name only a few.

The selection of the set of parameter to leave on the network will directly dependon the achieved performance and the operator priority (coverage, capacity,access performance, call retention performance…)

RF planning and optimization:

• By focusing on both qualitative and quantitative metrics, the main RF issues (cell overshoot, lack of dominant server, frequent change of best server) are minimized.

• Parameter setting: by isolated parameters in groups (reselection, access, handover …) that can be isolated, the tuning process is simplified.

Mobile Wimax drive test

This is the way to confirm mobile WiMAX coverage and provide basic troubleshooting tasks to assess signal quality.

Tools that help them quickly establish and maintain the planned coverage and quality of your network. Multiple technology and multi-band measurement support in a single receiver unit.

The purpose of the drive test activity is to capture actual data of the current wireless network and to show the condition of the RF environment thereby improving the performance of the wireless system to the optimal level

Every wireless system (CDMA, GSM & Wimax) has its own parameters to determine its performance. Drive test will record all the parameters by going around the intended RF environment and logged data will be analyzed in the “post processing” (In house) using tools like Agilant, Actix and ZXPOS-CNA1 and necessary optimization proposals will be made. Normally these proposals related to but not limited to Antenna height, tilting & orientation of antenna.

Generally the receiving power and transmitting power are the indicators of the coverage signal. Other system specific parameters will be used to reduce interference from other RF sources.

The drive test is also used to record call statistics like call success, call fail and call drops so that after the rectification the end user will enjoy continuous conversation without any interference or interruption. The logs will be made for both continuous call (Long call) and short call.

Since all the wireless system now used for data transfer apart from voice call throughput of data service on forward and reverse link also logged using drive test.