RS data throughput depends on a number of factors. GPRS has four coding schemes while EGPRS has nine modulation coding schemes, each offering different theoretical data rates. The actual performance of each of these is dependent on the C/I conditions, as shown in Figures 2.26(a) and (b). In the GPRS example, an ideal link adaptation would ensure that the coding scheme changes from CS-1 to CS-2 as the C/I increases from approximately 6 dB to 7 dB, thus maximising the user data rate. It should be realized, however, that at the crossover point high retransmission rates could be expected with the higher rate scheme. Allthough this is taken into account in the user bit rate calculation, it does result in inefficiency on the channel. Therefore, a system designed for a C/I of 10 dB will offer higher CS-2 throughput than one designed for 7 dB. In practice, many systems will already be designed for C/I levels Capacity Planning Table 2.16 Number of free timeslots in the circuit switched territory Free TSLs Free TSLs Mean free Number of carrier (after downgrade) (after upgrade) TSL in CSW significantly higher than this, and hence the regions of interest would be more likely to be the CS-2 and CS-3 boundary and the CS-3 and CS-4 boundary. The C/I for a given user will depend on the location within the cell. The link adaptation will aim to ensure that the correct coding scheme is used to allow the highest data throughput per user, typically based on measured C/I or BLER, as stated above. In a given cell, therefore, there will be a number of users achieving differing data rates and using different coding schemes. In addition, there will be different types of users - some being capable of single-slot only operation, others capable of multislot operation. The overall data throughput will be a function of these, and other, factors. Load Effects on Types of Active Users Since a limited number of timeslots are available, the average chance of a user having access to the desired number of traffic timeslots will decrease as the numbe