r of users increases. With busy conditions, several users may share a single timeslot, and hence the net data rate per user will be reduced proportionally, while the overall message transmission time will increase. Although the system throughput may not be compromised under busy conditions, the grade of service experienced by the users will be a result of the reduced data rates/increased transmission delay times. Efficient multislot operation is obviously very dependent upon the number of available timeslots. Under high load conditions, it becomes increasingly unlikely that a user will have full access to, for example, three consecutive timeslots. Therefore, it will be found that the mean data rate for a three-timeslot user will rarely meet those that are theoretically available (i.e. three times the single slot rate), except on systems operating at low loading levels. Based on the above, it might be anticipated that the data rates achieved with multislot operation will often fall short of those theoretically offered. The high rates will be available during low load conditions, but often reduced at medium-high load levels. Quality of Service and Rate Reduction In terms of dimensioning a network, it is necessary to consider the quality of service (QoS) that is offered to EGPRS users. For applications involving the transfer of relatively large files (email, web browsing, etc.), the overall data rate and message delay will be the best measure of QoS. While dimensioning for Radio Network Planning and Optimisation C/I (dB) MCS-9 MCS-8 MCS-7 MCS-6 MCS-5 MCS-4 MCS-3 MCS-2 MCS-1 Ideal LA C/l dB Figure 2.26 (a) Data throughput versus C/I for GPRS coding schemes. (b) EGPRS timeslot throughput versus C/I a given set of QoS requirements, the rate reduction factor can be applied since this provides an estimate of how heavily the EGPRS timeslots can be loaded before the offered QoS falls to unacceptable levels (The user data rates decrease as the EGPRS load increases). High occupancy (caused by multiple simul- taneous EGPRS us