Resource Allocation for Downlink Cellular OFDMA Systems: Part II - Practical Algorithms and Optimal Reuse Factor

TL;DR

This paper presents a low-complexity, distributed resource allocation algorithm for downlink OFDMA systems, demonstrating its asymptotic optimality and characterizing the optimal reuse factor in large user scenarios.

Contribution

It introduces a practical, distributed resource allocation algorithm for OFDMA systems that is proven to be asymptotically optimal, and characterizes the optimal reuse factor.

Findings

The simplified algorithm is asymptotically optimal as user count grows.

The optimal reuse factor is characterized analytically.

The proposed method reduces computational complexity significantly.

Abstract

In a companion paper, we characterized the optimal resource allocation in terms of power control and subcarrier assignment, for a downlink sectorized OFDMA system. In our model, the network is assumed to be one dimensional for the sake of analysis. We also assume that a certain part of the available bandwidth is likely to be reused by different base stations while that the other part of the bandwidth is shared in an orthogonal way between these base stations. The optimal resource allocation characterized in Part I is obtained by minimizing the total power spent by the network under the constraint that all users rate requirements are satisfied. When optimal resource allocation is used, any user receives data either in the reused bandwidth or in the protected bandwidth, but not in both (except for at most one pivot-user in each cell). We also proposed an algorithm that determines the optimal values of users resource allocation parameters. The optimal allocation algorithm proposed in Part I requires a large number of operations. In the present paper, we propose a distributed practical resource allocation algorithm with low complexity. We study the asymptotic behavior of both this simplified resource allocation algorithm and the optimal resource allocation algorithm of Part I as the number of users in each cell tends to infinity. Our analysis allows to prove that the proposed simplified algorithm is asymptotically optimal. As a byproduct of our analysis, we characterize the optimal value of the frequency reuse factor.