Effect of macrodiversity on CDMA forward-link capacity

Macrodiversity is an effective means to overcome large-scale fading effects. Much previous work focused on its benefits to the reverse link in CDMA systems. However, its effect on the forward link is less well understood. We analyze the CDMA forward-link capacity with macrodiversity and the results show that macrodiversity causes forward-link capacity loss whatever power allocation scheme is adopted. Based on the analysis of the cause of capacity loss, we further present a new transmission scheme, in which some joint control among the involved base stations is made to assure that the signals arrive at the desired mobile in phase and simultaneously. The simulation results show that in the new transmission scheme much higher capacity can be achieved with macrodiversity and the capacity increases rapidly with the number of involved base stations