Combined effect of site diversity and fast transmit power control in W-CDMA mobile radio

This paper presents the combined effect of inter-cell site diversity and fast transmit power control (TPC) in the wideband direct sequence code division multiple access (W-CDMA) forward and reverse links based on laboratory and field experiments. In forward link inter-cell site diversity, we propose a two-step scheme that compensates for the transmit power of base stations (BSs) when forward link fast TPC is used to prevent a transmit power difference between the BSs that is caused by TPC bit errors from becoming larger. We also present a reverse link inter-cell site diversity scheme based on the two-step selection combining at a radio network controller (RNC) using the following reliability information: cyclic redundancy check (CRC) results calculated per selection period and signal-to-interference plus background noise power ratio (SIR) averaged over the interleaving length. Field experimental results at the average vehicular speed of approximately 30 km/h showed that the required transmit power of a mobile station (total transmit power of BSs) at the average bit error rate of 10(-3) in the reverse (forward) link, when the inter-cell site diversity associated with two-cell sites was performed, was decreased by approximately 2.0 (0.3) dB compared to the case without site diversity.