Comparison of Pareto Optimum Transmit Power between CDMA and OFDMA Uplink

In this paper, two multiple access techniques for the uplink of next generation cellular mobile communication systems are investigated. The paper targets the optimum power allocation and link scheduling of the orthogonal frequency division multiple access (OFDMA) and code division multiple access (CDMA) schemes. A heuristic relaxation is used to simplify the NP-hard problem of the joint optimization between power control and link scheduling into the power controlled random access (PCRA) problem. PCRA problem is transformed to convex optimization problem through the geometric programming. For a single cell uplink system with imperfect frequency synchronization, OFDMA outperforms CDMA significantly. OFDMA uplink system requires 22% less transmit power than CDMA for the proposed scheme. Furthermore it has been found that a high subcarrier granularity is advantageous and results in less Pareto optimum transmit power.