The effect of power control on the downlink capacity of a direct sequence CDMA system for mobile radio

The capacity of code division multiple access (CDMA) systems for cellular mobile radio is currently an area of considerable debate. Much of this interest has concentrated on the system capacity when viewed in terms of the transmission path between the mobile and the base station, or system uplink. It is argued that system non-idealities such as severe propagation conditions, power control errors and realistic antenna patterns may significantly degrade the capacity of the system. The effect of practical limitations on the system downlink capacity is investigated. The paper shows that downlink power control is essential in order to obtain similar capacity to that achieved on the system uplink, and that in the absence of power control downlink capacity is approximately halved. However, if power control is employed then, provided that both system uplink and downlink require similar signal to noise ratios (SNR) for acceptable performance, the capacity of each link is similar.<>