ogonality and soft handovers are further factors associated with the load factor in the downlink direction. The best way to improve capacity is always to increase the number of cells/carriers. The increased number of sectors proportionately increases the capacity of the network. Additionally, orthogonal codes should ideally be truly orthogonal, but owing to multipaths some orthogonality is lost, thereby increasing interference. Multipath diversity improves the coverage but also reduces the orthogonality. Multipath diversity is more important at the cell edges as it improves the performance. Another way of improving capacity is by 'transmit diversity'. If multipath diversity is less, then the downlink transmit diversity increases the capacity to quite an extent. Lower bit rates would also increase the capacity. This is possible by using the adaptive mean rate (AMR) codes, AMR being the speech codec scheme that is used in UMTS. Quality Enhancements End-to-end QoS has to be considered in third-generation networks, but here we focus on the delay at the air-interface, which will have a direct impact on quality. As noted in earlier chapters, QoS is application-dependent, but the immediate concern is to reduce the delay at the air interface for PS services. Unlike in GSM where voice quality is the only 'big' concern, in WCDMA attention turns to PS service requirements and performance. Delay may or may not take place at the air interface (it may be due to transmission or the core network), yet the first step for end-to-end (E2E) quality is the performance of the application at the air interface. The example shown in Table 7.7 specifies the conditions and required performance for PS services. This is based on parameters such as BLER, DCR, application failure rate, delay and the throughput for 64, 128 and 384 kbps data rates. Drive tests results give the monitored results for these five parameters. 7.7.4 Parameter Tuning As noted earlier, WCDMA networks have a huge number of parameters, and some of the key ones are chosen,