Uplink capacity investigations of TDD/CDMA

In this contribution we analyze the uplink capacity of a TDD/CDMA system. In TDD/CDMA the mobiles suffer from interference inflicted by the other mobile stations (MSs) both in the reference cell the MS is roaming in (intracell interference) as well as due to those in the neighbouring cells (intercell interference). Furthermore, in contrast to FDD/CDMA, where the base stations (BSs) transmit in an orthogonal frequency band, in TDD/CDMA there is additional interference imposed by other BSs of the adjacent cells. In return for this disadvantage TDD/CDMA guarantees the flexible utilization of all the available bandwidth, which meets the demand for the support of asymmetric uplink and downlink services, such as high speed data rate download in mobile Internet services, etc. This study quantifies the amount of uplink interference inflicted by the MSs and BSs. With the aid of characterising the interference, a detailed discussion of the uplink capacity of TDD/CDMA is provided and two extreme teletraffic loading scenarios of the UTRA TDD/CDMA system are considered. Our numerical results show that the capacity of TDD/CDMA is significantly poorer, than that of FDD/CDMA.