e number of mobile subscribers and their transmission rates. To achieve a service rate of 144 kbps, more sites are required than to achieve a service rate of 12.2 kbps. Moreover, as the number of users increases, the cell coverage area decreases. As downloading is more prevalent than uploading, the downlink capacity will be a critical factor for size of area covered by the cell. Once this has been dealt with, cell configurations can be decided upon in terms of sectors and carriers (TRXs). Coverage and capacity plans are made and the process reiterated many times by using radio network planning tools (refer to Appendix A). Then the planning process moves forward to the site survey and site acquisition phase, as explained in Part 1. At this point it is helpful to understand a concept known as AMR (adaptive multi-rate), as an aid to choosing the right parameters to analyse when optimising the quality of the network. 7.5.10 Adaptive Multi-rate Unlike in GSM, where speech codecs are fixed - e.g. FR (full rate) or HR (half rate) - and their channel protection is also fixed rate, in WCDMA radio networks the process of AMR is used to make it possible to adapt speech and channel coding rates according to the quality of the radio channel. This improves the error protection and channel quality. The codec basically has one single integrated speech codec with eight source rates. This is controlled by the radio resource management functions of the RAN. These eight source rates are 12.2, 10.20, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kbps. The process of Table 7.5 Link budget calculation in WCDMA radio network Link Budgets: Voice Data rate (kb/s): Load: Uplink Downlink Uplink Downlink Uplink Downlink Uplink Downlink Uplink Downlink RECEIVING END Node B Node B Node B Node B Node B Thermal Noise Density dBm/Hz BTS Receiver Noise Figure BTS Receiver Noise Density dBm/Hz -171.00 -166.00 -171.00 -166.00 -171.00 -166.00 171.00 -166.00 171.00 166.00 BTS Noise Power [NoW] -105.16 -100.16 -105.16 -100.16 -105.16 -100.16 -105.16 -100.16 -1