On the Capacity Enhancement of a Cellular CDMA Channel with Asymmetrical Bandwidth Allocation

Abstract

Capacity enhancement of cellular CDMA is analyzed using an asymmetrical-bandwidth-allocation approach. Cellular CDMA systems with and without successive interference cancellation are considered. The main source of interference is interuser interference and, in particular, a 9-cell configuration is employed to account for interference from surrounding cells. By transferring more bandwidth or, equivalently, processing gain from the forward link to the reverse link, we have effectively balanced their performance and raised the overall capacity of the cellular system. The optimum bandwidth allocation is easily obtained from the performance curves of both links. For a typical cellular CDMA with a bit error rate of 10-3, the capacity gain of this approach is about 40%. If successive interference cancellation is employed and both links have the same quality, then both links should have equal bandwidth. However, in a situation where imperfect power control occurs, our studies indicate that using interference cancellation alone achieves a 25% increase in capacity, while enhancement with an asymmetrical bandwidth allocation overlay raises this gain to 68%.