Power control for successive interference cancellation with imperfect cancellation

Abstract

This paper proposes and analyzes an iterative power control scheme for use with successive interference cancellation (SIC) in the presence of cancellation errors. SIC is shown by Andrews and Meng (see IEEE Transactions On Wireless Communications, Oct. 2001), to increase the capacity of cellular CDMA systems significantly, even if the signal cancellation is imperfect due to estimation errors. However, an important complication of SIC relative to conventional CDMA receivers is that a specific non-uniform distribution of powers must be assigned to the users in order for the system to function robustly. This paper proposes a simple up/down distributed iterative power control scheme for DS-CDMA systems employing SIC. We analyze its feasibility region and prove that it converges to close to the optimum solution even in the presence of estimation errors. The total received power is shown to be a reliable metric for admission control. This analysis considers both multi-rate CDMA where each user has a different target signal-to-interference-and-noise ratio (SINR), and asynchronous power control where user power updates occur asynchronously.