Reverse link capacity of SIR-based power-controlled CDMA systems with antenna arrays

In this paper, reverse link capacity, in terms of user capacity, of a code-division multiple access (CDMA) system with both beamforming and antenna diversity under a multipath environment is analyzed and compared. Signal-to-interference ratio (SIR) based power control is assumed in the system. Antenna elements are divided into several groups to achieve antenna diversity gain. Antenna elements in a group are closely spaced to perform beamforming in order to suppress the own-cell and other-cell interference, while those groups are widely spaced to achieve the diversity gain. Based on the comparison, a most efficient use of the antenna array according to the distribution of antenna elements among the groups is obtained. Instead of using tedious iterative methods to evaluate user capacity, a simple closed-form capacity expression with respect to antenna diversity and beamforming gains, a target SIR and the CDMA processing gain is derived. Numerical results indicate significant capacity improvement with the antenna array.