Random Access OFDMA Network with Dynamic Resource Allocation

In this paper we investigate the optimum power allocation in a random access wireless orthogonal frequency division multiple access (OFDMA) communication system with multiple source and multiple destination nodes. The multiple sources in the system each transmits information to multiple destinations at a fixed signal to noise ratio (SNR) target and cooperates via an orthogonal amplify and forward protocol with different frequency slots. We develop a framework for power allocation in this scenario around the concept of OFDMA and derive the expressions for the transmit power received by each source to achieve their SNR targets as a function of the cooperation ratio between sources. We also observe that relay node employing orthogonal amplifying and forwarding strategy solves the problem of optimally allocating the total power of each relay node between the transmissions it is assisting. We investigate the effect of interference when all sources transmit with equal frequency allocation and the impact of orthogonal frequency division among the sources.