The benefits of advanced receivers for high speed data communications in WCDMA

The benefits of using an advanced receiver, the generalized RAKE (G-RAKE) (see Bottomley, G.E. et al., IEEE J. Select. Areas Commun., vol.18, p.1536-45, 2000; Wang, Y.-P. E. and Bottomley, G.E., Proc. IEEE Veh. Technol. Conf., 2000), for high speed mobile Internet applications over wideband CDMA (WCDMA) are studied. Like the conventional RAKE receiver, G-RAKE is a linear receiver that combines the outputs of correlators (fingers) at different time lags. However, unlike RAKE, the finger placements and combining weights for G-RAKE can be optimized to suppress interference, which is achieved by accounting for the interference coloration introduced by dispersive channels. We show that, even for mildly dispersive channels, G-RAKE can increase the achievable peak data rates significantly. It is also shown that the enhanced link performance translates into system capacity gains of around 30-35%. Moreover, for file transfer applications, G-RAKE reduces the download time of a 200 KB file by approximately a half under moderate to high system loads (effects of TCP and Internet delays are accounted for). Therefore, advanced receivers provide significant perceivable benefits to both service operators (higher system capacity) and end users (higher effective data rates, shorter download time).