 into standard blocks and each of these blocks is then assigned to the respective TRX. This scheme of allocation is easy to upgrade. As the spare capacity is distributed along the whole 2 Mbps signal, it is difficult to add a whole new base station. One way of doing time-slot allocation was shown in Figure 3.5, where all the traffic chan- nels are allocated time slots 1-24 while all the signalling is confined to the lower part of the 2 Mbps signal. Another way of doing time-slot allocation planning is shown in Figure 3.20, 1st BTS Expnsn 2ND BTS Expnsni MCB LCB Q1-bus for TRXnr TRX Traffic TRX1sig BCF1 sig TRX2sig WH!!! TRX Traffic TRX Traffic TRX3sig XXXXXX/ TRX4sig BCF4 sig TRX Traffic 1+1+1b TRX Traffic TRX5sig XXXXXXX TRX6sig TRX Traffic 3+3+3a 4+4+4 TRX Traffic TRX7sig BCF7 sig TRX8sig 1+1+1c TRX Traffic TRX Traffic TRX9sig XXXXXXX TRX10sig BCF10 sig 2+2+2b TRX Traffic 1+1+1d TRX Traffic TRX11sig (XXXXX) TRX12sig TRX Traffic MCB LCB Q1-bus Figure 3.20 Example of time-slot allocation DETAILED TRANSMISSION NETWORK PLANNING which shows a 1 + 1 configuration. The time slots for traffic and signalling for each TRX are allocated together. Time slots 1-3 contain the traffic for TRX1 and signalling for TRX1 and TRX2. Subsequent time slots 4-7 are empty, because of an assumption that the capacity for cells will increase from one TRX to three TRXs. And same pattern is followed for other cells. This scheme can also be used for a condition where four base stations are using the same 2 Mbps signal. The synchronisation bits and management bits can be placed in either TSO or TS31. These bits can also be placed in other time slots as well. 3.4.3 2 Mbps Planning The routing of the 2 Mbps is part of time-slot allocation and detailed planning. This involves the planning of routes from where the 2 Mbps line will pass and where it will terminate. Planning engineers have to pass on these plans to the commissioning engineers, SO they should be very carefully and clearly made. Apart from this, planning engineers during the course o