Impacts of imperfect channel estimation and multipath fading on forward-link performance in CDMA distributed antenna systems

The study of performance in distributed antenna (DA) systems has recently received considerable attention and some conclusions have been drawn. However, most of them are based on the ideal channel estimation assumption and analyzed in flat fading channels. In this paper, we investigate the impact of imperfect channel estimation on the forward-link outage performance in CDMA DA systems in a multipath fading environment. A detailed analytical model, based on a hybrid signal combining method, is presented and an exact outage probability expression is derived. Our investigation shows that the effect of imperfect channel estimates varies with system load. Furthermore, we find that for the forward-link of DA systems, if simulcasting is employed, macrodiversity can decrease both the sensitivity of performance to channel estimation errors and the outage probability, which is contrary to the conclusion drawn based on the ideal channel estimation assumption.