RF design strategies for cellular technologies

RF design strategies for cellular technologies

1. RF Design Strategy Use optimized design. Influence the anchor network. Enforce design rules. Check against performance commitments in attachment H. Cooperate with the RF Designer and Cingular proactively.

2. Design Considerations In UMTS networks coverage and capacity are interchange-able. The network is designed for both coverage and capacity. Some difference as compared to GSM. GSM UMTS TDMA AMPS GSM TDMA AMPS

3. Guaranteeing CPICH RSCP is not enough UE needs to decode the CPICH to get service. Good CPICH RSCP (Ec) does not mean that the CPICH can be camped on. Good CPICH Ec/Io is needed to camp on the system. Networks should be designed for good CPICH Ec/Io. A B E F C A B E F C Sufficient RSCP Bad Ec/Io

4. Design for Specified Load Interference increases with loading. Coverage decreases with loading. Networks should be designed for specified load, otherwise severe coverage issues will be encountered.

5. Design for Service To get service, both uplink and downlink Eb/No targets for the service should be met. If the UE can camp on a cell, that does not necessarily imply that it can get service. Power is a shared resource.

6. RF Design Process

7. Baseline Design

8. Feeder Changes UMTS 1900 forward link becomes the limiting link for narrower feeders. Plans will be prepared to perform feeder changes on sites where the UMTS 1900 feeder loss is greater than 3 dB. Comscope 1 5/8” Feeder will be used as per Cingular Headquarter direction.

9. Tower Mounted Amplifiers TMAs help improve coverage/indoor coverage in 1900 systems. Sites that do not have TMAs will get 1900 only TMAs. Sites that have 850 TMAs will get dual band TMAs.

10. Remote Electrical Tilts Remote Electrical Tilt (RET) units can be used to change the antenna downtilt remotely without climbing the tower. Availability of RETs speeds up initial tuning. UMTS networks need to be re-configured as traffic grows. RETs can reduce the cost of regular O&M activities.

11. Antenna Selection Dual band antennas with independent electrical downtilts will be used for UMTS 1900 overlay on GSM 850. All other antenna parameters will be preserved. Narrow horizontal beam antennas will be selected if the following conditions can be met. Additional capacity commitments can be met. UMTS performance is improved. GSM composite coverage is not affected. UMTS CPICH coverage is not reduced. UMTS CPICH Ec/Io is not degraded. UMTS system capacity is not reduced.

12. Antenna Sharing UMTS1900 on GSM850 Dual band antenna should have independent electrical downtilts for both bands. All 850 antennas with horizontal beam-width greater than 90 degrees will have to be replaced with 90 degrees antennas. Dual band antennas are generally heavier than single band antennas. Quad-pole and Tri-pole dual band antennas are not available. UMTS GSM X X

13. Antenna Sharing UMTS1900 on GSM1900 100% antenna sharing. RF equipment for sharing antennas is needed. This equipment results in additional loss. UMTS tilts are constrained by GSM tilts. In a 1/1 FLP network, cell plan changes that help UMTS should also help GSM. X X UMTS GSM DDU

14. Link Budgets Separate link budgets are needed for CPICH and for each RAB. Link budgets for the RABs consider coverage as well as capacity. Generally, higher rate RABs have tighter budgets and lesser coverage/capacity.

15. Omni sectorization All omnis will be sectorized.

16. Worst Offenders Worst offenders may be lowered or downtilted aggressively. If possible, worst offenders may be removed from the UMTS plan.

17. Adding sites to Anchor Network Initial design is performed on mostly Cingular sites: like for like antenna. Plots and stats are produced from the Initial design. Problem areas are identified and ranked. Sites are added if the problem area cannot be resolved by antenna system modifications. Simulations are re-run to verify changes. GSM Design UMTS Initial Design UMTS Final Design

18. Problem Areas Loss of GSM coverage Insufficient CPICH RSCP. Insufficient CPICH Ec/Io. Excessive path loss. RAB Eb/No not met. Imbalanced links. Low service probability of indoor coverage. High failure rate. Pilot Pollution. Poor throughput. Poor BLER.

19. Design Priorities Establish sufficient CPICH RSCP. Establish good CPICH Ec/Io under load. Ensure high probability of service coverage under load on both links. Which service? What about HSDPA? CPICH RSCP CPICH Ec/Io Service Coverage Design is built up by covering the basics first.

20. Optimized Design

21. Optimized Tilts No uptilting beyond 0 ° . Optimi ACP will be used if available. For UMTS1900 over GSM850, few downtilts are expected.

22. Why are downtilts more important Power is a shared resource in UMTS. As load increases in a cell, total transmitted power increases also. Max transmit power cannot be used to control interference. A B C D E A B C D E Unloaded Loaded

23. Coverage Overlap Overshooting sites should be lowered, downtilted or removed from the UMTS plan if possible. For neighboring cells, some optimum coverage overlap is needed. Too much overlap results in loss of capacity Too little overlap results in increased interference Optimum Overlap

24. Narrow-beam (65 ° antennas) Usage Cingular’s GSM networks are on 90 ° grids. Replacing 90 ° antenna with a 65 ° antenna means higher capacity commitment. Use 65 ° antenna only if: GSM composite coverage is preserved. Site is in urban or dense urban morphology with <= 1 mile site to site distance. No UMTS coverage (CPICH and all RABs) holes are created. Increased capacity commitments can be fulfilled.

25. Design Targets CPICH RSCP CPICH Ec/Io (loaded)

26. Design Targets – RAB Coverage RAB coverage under committed load. Meet the following four criteria: DL Achieved Eb/No is equal to or better than the target Eb/No everywhere in the cluster. UL Eb/No failure is less than 2% everywhere in the cluster. Probability of Coverage (indoor) is 98% or higher everywhere in the cluster. Path balance is achieved everywhere in the cluster.

27. IRAT will be activated for all the cells pointing out of the UMTS Coverage Area. 64k CS Video calls will not be tested in the cells pointing out of the UMTS Coverage Area. Target Design Area

28. Tune and verify propagation model Suggested Steps Design Kick-off Obtain design inputs – site database, site walk downs etc. Sanitize databases Prepare a list of all site that will have tower work Send the list to Site Development Vendor for approval Populate the Planning Tool. Prepare Initial Plots/Stats Prepare a list of changes to improve system performance in agreement with the local market. This list includes automatic changes to the network Modify design from Site Development Vendor Input Consolidate a list of sites where no changes will be possible Make changes in the planning tool after filtering the no-change list and run simulations on the modified design Prepare a list of changes to improve system performance in agreement with the local market. This new list will not include sites where tower work cannot be performed Fine tune the design Prepare deliverables Finalize clusters

29. The RF Designer pays for any changes over the first 20% of the changes after the delivery of the initial design. Limits on Design Changes

30. UMTS Link Budgets ASSET 3G for RF design. Optimi Automatic Cell Planning (ACP). Volcano Ray Tracing. Design Tools

31. Questions?