A Unified Approach to Energy-Efficient Power Control in Large CDMA Systems

TL;DR

This paper introduces a unified energy-efficient power control method for large CDMA systems applicable to various multiuser receivers, ensuring convergence to a Nash equilibrium where users optimize their energy efficiency.

Contribution

It develops a universal power control algorithm based on large-system analysis that guarantees convergence and applies to multiple receiver types in CDMA networks.

Findings

The Nash equilibrium is SIR-balanced for the considered receivers.

The proposed algorithm converges in large-system limits.

Performance is comparable or superior to conventional schemes in finite systems.

Abstract

A unified approach to energy-efficient power control is proposed for code-division multiple access (CDMA) networks. The approach is applicable to a large family of multiuser receivers including the matched filter, the decorrelator, the linear minimum mean-square error (MMSE) receiver, and the (nonlinear) optimal detectors. It exploits the linear relationship that has been shown to exist between the transmit power and the output signal-to-interference-plus-noise ratio (SIR) in the large-system limit. It is shown that, for this family of receivers, when users seek to selfishly maximize their own energy efficiency, the Nash equilibrium is SIR-balanced. In addition, a unified power control (UPC) algorithm for reaching the Nash equilibrium is proposed. The algorithm adjusts the user's transmit powers by iteratively computing the large-system multiuser efficiency, which is independent of instantaneous spreading sequences. The convergence of the algorithm is proved for the matched filter, the decorrelator, and the MMSE receiver, and is demonstrated by means of simulation for an optimal detector. Moreover, the performance of the algorithm in finite-size systems is studied and compared with that of a conventional power control scheme, in which user powers depend on the instantaneous spreading sequences.