Uplink user capacity of a multi-cell CDMA system with hotspot microcells

This paper studies the number of simultaneous voice users (or user capacity) supportable on the uplink of a multiple macrocell CDMA system with multiple "hotspot" microcells embedded within. These microcells operate over the same bandwidth as the macrocells and are assumed to be installed in regions of high user demand. First, conditions for optimal performance of such a system are established. This analysis shows that the total user capacity is maximum when there are equal numbers of active users in each cell. Along with these conditions, analytical approximations are presented for computing maximum user capacity as a function of the number of microcell bases in the system. In particular, the approximations show the total user capacity as growing linearly with the number of hotspot microcells. Simulation results verify this trend when the number of microcells in the system is not large. The numerical constants for this linear trend are related to basic system and propagation parameters. When the number of microcells gets large, it is shown that the same linear growth in capacity can be sustained by desensitizing the macrocells, i.e., raising the received power requirements at the macrocell bases.