y (the assumption is that the 1E1 is able to handle 12 TRXs). In few months time, the operator realises that a shopping mall in the vicinity of the two sites is to be built. This would mean that these two sites would need upgrades leading to a requirement for extra PCMs. If in the very beginning each site had been assigned one PCM each, there would be less problems at a later stage. However, such decisions (i.e. assigning one PCM to each site) are not easy in the beginning as the revenues may not have started to flow and obtaining leased lines may be costly in some countries. Transmission Network Planning and Optimisation DL Time Inadeq EDAP / DL Payload 27-Aug 10-Sep 24-Sep 8-Oct 22-0c 5-Nov 19-Nov Zone 1 Zone2 Zone3 Zone4 Figure 3.77 DAP performance in various regions of the network Upgrading the GSM network to the EDGE network definitely leads to capacity problems. This is mainly due to the dynamic Abis pool. As seen previously, the dynamic Abis pool would need some reserved timeslots for itself. There may be some problems with the dimensioning for the DAP, which would need to rectified during the optimisation phase. The performance can be monitored using the network management system and the sites/regions with problems can be identified. Figure 3.77 shows the performance of the network in various regions. It shows that the DAP in zone 2 is the most congested. This means that the utilisation rate is more than 100%, thereby indicating that users are not able to access the data at the maximum rate, e.g. the MCS-9 coding scheme. The reason lies in the dimensioning and hence one solution could lead to correction of the DAP size. The congestion (as shown in Figure 3.77, zone 2) may also be due to some other factors, such as the availability of the PCUs and/or reservation of the signal processing resources. In a network upgraded from the GSM to EDGE capable, the problems may lie in the PCM lines. Due to nonavailability (or higher costs) of PCM lines, the pool size may be kept small (e.g. one or two timeslots) as the