of PA Specifications 8-PSK Figure 2.80 8-PSK operating beyond nonlinear compression Figure 2.81 8-PSK operating with 2 dB average power decrease and backoff required to ensure a smooth/continuous transition between phase states (as shown by the sample black trace). Figure 2.83 illustrates the power 'envelope' in the phase-state domain. Note how the +1 dB power variation tolerance in the GMSK falls within the +4 dB tolerance for 8-PSK peak-to-average value. This illustrates that the tighter the peak-to-average 8-PSK power required for 'overshoot', the closer the average 8-PSK power approaches the average GMSK power. However, at the maximum power, 8- PSK will always require additional APD compared to GMSK due to the requirement for linear 8-PSK overshoot. Cell Reselection With the increased availability of higher multislot class EGPRS capable mobiles, it is important to understand the performance impact this has on the ability for the mobile to select efficiently, reliably and accurately the best serving cells in a network. At the time of writing, mobiles and networks are restricted to standard GSM idle mode measurements and much of the performance is dependent on advanced measurement algorithm techniques in each particular mobile. In the near future, Network Assisted Cell Radio Network Planning and Optimisation Start Finish Figure 2.82 8-PSK vector state transition diagram PA Spec Figure 2.83 GMSK and 8-PSK power envelope Change (NACC) and Network Controlled Cell Reselection (NCCR) capabilities will be added to the network and mobiles that support these features and enhanced measurements will become available. These enhanced features will significantly improve the cell reselection performance by reducing latency and interruptions in throughput during EGPRS cell changes. Figure 2.84 illustrates the difference between existing GSM voice and EGPRS capable mobiles in how they evaluate neighbours for performing handover and cell reselections. During a circuit switched (CSW) call, the mobile is able to evaluate neighbou