Performance comparisons of power allocation mechanisms for downlink handoff in the WCDMA system with microcellular environments

This paper investigates different power allocation algorithms for downlink handoff in the wideband code division multiple access system from both outage performance and power efficiency perspectives. Traditionally, the site selection diversity transmission (SSDT) scheme has been viewed as the optimal solution for downlink handoff from the standpoint of power efficiency, which selects the best base station to transmit downlink signals to the user. However, from the outage performance perspective, the user at the cell boundary may have poor quality if there is only one serving base station. Thus, we are motivated to develop an improved SSDT scheme that can take both power efficiency and outage performances in account. In this paper, we propose a joint link proportional power allocation (LPPA) and SSDT scheme. Through analysis and simulation, we demonstrate that the proposed joint LPPA and SSDT scheme is the optimal power allocation solution for downlink handoff in the WCDMA system, which not only can improve the outage performance over the SSDT scheme when the traffic intensity is low, but can be very power efficient as the SSDT scheme in the heavy traffic situation.