Power Controlled Random Access in Multi-Cell OFDMA Uplink

This paper targets the problem of optimum power allocation and link scheduling in cellular systems. In particular, the uplink performance of OFDMA (orthogonal frequency division multiple access) is investigated. By means of heuristic relaxation, the NP-hard problem of joint power control and scheduling is transformed into one of power controlled random access (PCRA), which is formulated as a convex optimization problem. The PCRA problem formulation in this paper clearly reveals the power v/s delay dilemma associated with wireless multiple access networks. A relative increase in the SINR (signal- to-interference-plus-noise) target of 2dB (from 12dB to 14dB) results in a 100%-130% increase in the Pareto optimum power assuming a cellular full frequency reuse system. In contrast, this increase is only 30%-55% in a single cell scenario. Therefore CCI (co-channel interference) mitigation techniques should be implemented to alleviate the problem of high CCI.