Resource allocation for the AF Multiple Access Relay Channel with OFDMA

This paper considers the resource allocation problem for a Multiple Access Relay Channel (MARC). A transmission scheme with OFDMA and Amplify-and-Forward (AF) relaying is assumed. To maximise the sum rate a joint allocation of transmit power and subcarriers has to be done. This problem is known to be NP-hard and can only be solved by an exhaustive search which is not feasible for practical problem sizes. Different near-optimum algorithms for solving this problem are proposed. The problem of carrier and power allocation can either be done separately or jointly. For example a straight forward gradient method can be applied if the constraints of the allocation problem are relaxed. The obtained solution tends to fulfil the original constraints and it is also shown to be nearly optimum. The performance of all algorithms is evaluated by numerical simulations. Furthermore, their complexities are analysed and compared.