dth and CQI_avg represents the average wideband CQI value in the past. The relative CQI metric reflects the user's instantaneous channel condition compared to the average and therefore can indicate a favorable moment for scheduling the user. Of course, the time domain scheduling gains are in the end somewhat limited because of the tight delay budget. © 2009 by Taylor & Francis Group, LLC Radio Access Network VolP Optimization Table 10.1 Packet Scheduling and Resource Allocation Algorithm Alternatives Scheduler Description RR scheduling with even-share resource allocation Proportional fair scheduling with even-share resource allocation PF + SCS SCS-based VolP optimized scheduling algorithm using PF metric to order the users in the SCS. Even-share resource allocation PF I SCS RA As PF SCS, but with dynamic resource allocation As a further improvement, compared with sending one packet per TTI, bun- dling multiple packets together in one transmission can reduce related control channel signaling overhead and thus improve air interface efficiency (see Section 10.6.2.1 for further details). Therefore, in the user selection within each group, priority is given to users who can support bundling. Further, in Table 10.1 the abbreviations of considered scheduler alternatives are listed and explained. Table 10.2 illustrates the relative HSDPA capacity improvements that can be obtained with a packet scheduler specifically designed for VoIP service over the blind RR scheduling method without any VoIP specific user prioritization. The table shows capacities for an 80-ms delay budget assumption. The selected set of scheduler alternatives compares the enhancements incrementally. These numbers verify that packet scheduling and allocation of transmission resources play a key role in achieving good VoIP capacity. There is a large difference between the best and the worst scheduler option. PF gives the gain over RR, as it is, on average, able to schedule users at better channel conditions. Introducing SCS is an important improve-ment,