Optimality of binary power-control in a single cell via majorization

TL;DR

This paper proves that the optimal power control in a single cell uplink scenario with peak power constraints is binary, and introduces efficient algorithms and conditions for maximizing aggregate communication rate.

Contribution

It establishes the binary nature of optimal power allocation using majorization theory and provides polynomial-time algorithms and conditions for optimal and near-optimal solutions.

Findings

Optimal power control is binary, links are either on or off.

A polynomial-time algorithm for optimal power allocation is proposed.

Successive decoding outperforms in sum-rate only with near-perfect interference cancellation.

Abstract

This paper considers the optimum single cell power-control maximizing the aggregate (uplink) communication rate of the cell when there are peak power constraints at mobile users, and a low-complexity data decoder (without successive decoding) at the base station. It is shown, via the theory of majorization, that the optimum power allocation is binary, which means links are either "on" or "off". By exploiting further structure of the optimum binary power allocation, a simple polynomial-time algorithm for finding the optimum transmission power allocation is proposed, together with a reduced complexity near-optimal heuristic algorithm. Sufficient conditions under which channel-state aware time-division-multiple-access (TDMA) maximizes the aggregate communication rate are established. Finally, a numerical study is performed to compare and contrast the performance achieved by the optimum binary power-control policy with other sub-optimum policies and the throughput capacity achievable via successive decoding. It is observed that two dominant modes of communication arise, wideband or TDMA, and that successive decoding achieves better sum-rates only under near-perfect interference cancellation efficiency.