Optimum cell boundary for uplink and downlink in CDMA systems

In order to maintain the communications quality at a target level, signal-to-interference ratio (SIR)-based transmission power control methods have been developed in CDMA cellular systems. These power control methods: however, do not necessarily improve system efficiency when there is a large geographic deviation in traffic because they only control power levels. A shift in the cell boundary can control traffic balance between cells. In this paper, we evaluate the optimum location of the cell boundary and the power levels when a mobile station adaptively selects a base station (BS) for each of uplink and downlink under non-uniform traffic. Because of the asymmetry in system structure between uplink and downlink, the optimum cell boundaries are not always coincident for both the two links: the location of the cell boundary is found to migrate according to the loss in orthogonality in the downlink.