Performance study of space-time transmit diversity and sectorisation in WCDMA radio networks

This paper investigates the network-level improvements by using space-time transmit diversity (STTD) and sectorisation in the WCDMA radio access networks (RAN). By using a dynamic WCDMA simulator, the performance improvements by applying STTD in two different cell-layouts under two different channel models were analyzed. Three main effects of STTD on capacity and coverage were concluded. They are summarized as: (1) the channel diversity gains contribute to some capacity improvement; the gain is likely reduced by the effect of SHO and also due to the shortage of the RAKE fingers; (2) significant capacity improvement lies in the increase of the downlink power due to the additional antenna (e.g., twice the power); a net gain of at least twice the capacity of the non-diversity case is achievable; (3) for coverage improvement, the achievable gain was 2-4 dB as a result of lower received Eb/No at 90-95 percentile targets. Besides, sectorisation gain by splitting 3-sector to 6-sector is also verified in the simulations.