A simplified generic optimum power control scheme for CDMA cellular systems

Abstract

Power control is of great importance in reducing cochannel interference and increasing the capacity of mobile telecommunications systems. The aim of optimum power control procedure is to achieve a maximum carrier-to-interference ratios (CIR) in all active communication links (i.e. CIR balancing). Optimum power control with CIR balancing has been widely studied for frequency-division/time-division multiple access (FDMA/TDMA) cellular systems. In these systems, the CIR-balanced optimum power control was transformed to an eigenvalue problem using link-gain matrix. The same method was proposed to CDMA systems. However, the size of the link-gain matrix is proportional to the square of the number of communication links in the system. Thus, the computation of the eigenvalue may be infeasible in CDMA systems with high load. Moreover, optimum power control has never been studied in crossed slots where some mobiles are active in downlink and other in uplink. A simplified optimum power control scheme has been proposed to reduce the link-gain matrix only in the forward link. In this paper, we introduce a simplified generic optimum power control scheme for uplink, downlink and crossed slots. This scheme is based on a link-gain matrix whose size is proportional to the square of the number of cells. Simulation results have justified that the proposed scheme achieves the same upper bound of CIR as the complex scheme.