lowing example. There are six calls MCS-3, MCS-9, MCS-7, MCS-5 and 2 X MCS-6. This means that the total number of requests for the Abis slave channels is 13. The pool size is three timeslots, i.e. 3 X 4 = 12 Abis channels. This means that the resources in the pool are not sufficient to handle the calls as they are. Thus, there will be some reductions in call rates in order to make sure that all calls go through but with a lesser data rate than requested. Thus, in this case, MCS-9 and MCS-8 calls reduce to the MCS-7 coding scheme, while the MCS-7 call is reduced to the MCS-6. Thus, by reducing the coding schemes of the calls, i.e. by reducing the requested throughput, the requested calls are able to go through. MCS-3 MCS-5 MCS-6 MCS-6 MCS-7 MCS-7 MCS-6 MCS-6 MCS-9 MCS-9 MCS-9 MCS-9 Observation From the above two cases, it can be seen that the size of the DAP pool plays a very important role. If the DAP pool is not sufficiently large, then the coding schemes of the calls would be downgraded. This means that the effective throughput goes down. Thus, when designing the DAP, the average throughput Transmission Network Planning and Optimisation lu-CS lu-PS lu-CS lu-PS Figure 3.56 Transmission interfaces in WCDMA reduction basically signifies that the coding scheme of the calls would be reduced, thereby reducing the effective throughput. 3.6.3 Interface Planning in the UMTS Access Transmission Network Interface dimensioning in WCDMA networks is a key aspect of transmission network planning. It is much more complicated than the interface dimensioning that was seen in the GSM/EDGE networks. The following interfaces are needed to be dimensioned by access engineers (see Figure 3.56): Lub: interface between the BTS and RNC I-cs: interface between the RNC and MGW (media gateway) Iu-ps interface between the RNC and SGSN Iur: interface between the RNC and RNC In dimensioning, the capacity required is calculated in order to decide what equipment is required. Capacity calculations in WCDMA networks requires an understanding of so