Downlink performance of IS-95 DS-CDMA under multipath propagation conditions

For PCS applications in the USA the direct-sequence code division multiple access system (DS-CDMA) IS-95 has been standardized and will be deployed in parallel to time division multiple access based systems like PCS 1900 (GSM derivative) and D-AMPS. In a DS-CDMA system intracell co-channel interference has to be taken into account in addition to intercell interference. The available system capacity, which is one of the main important parameters for the system selection from the network operators point of view, is determined by the carrier/interference-ratio and the co-channel interference resistance of an air interface. The main objective of this paper is to investigate the impact of multipath propagation on the downlink capacity based on the transmitter and receiver signal processing. The wideband radio channel is characterized by a time-variant tapped delay line including adjacent cell interference. For well defined conditions the downlink system capacity is evaluated with respect to a quality of service criterion. With increasing number of significant multipath components and decreasing mobile speed the capacity is decreasing considerably.