Power and Channel Resource Allocation in Cooperative Multiple Access Schemes

In this thesis, we develop efficient algorithms for the jointly optimal power and chan­ nel resource allocation in different wireless cooperative multiple access systems. In addition, in some cases insight into the structure of the optimal allocation enables the development of modified cooperation schemes with better performance, and efficient algorithms are developed for jointly optimal power and channel resource allocation for these modified schemes too. The goal of the jointly optimal allocation algorithms developed in this thesis is to maximize the achievable rate regions of the schemes under consideration. Two cooperative channel models are considered; namely, the cooperative multiple access channel, and the multiple access relay channel. For the cooperative multiple access channel, two relaying strategies are considered; namely decode-and-forward (DF), and amplify-and-forward (AF). For the coopera­ tive multiple access channel with DF relaying, systems with full-duplex nodes and systems with half-duplex nodes are considered. In the case of full-duplex nodes, it is shown that the non-convex formulation of the power allocation problem can be sim­ plified and re-cast in a convex form. In fact, closed-form expressions for the optimal power allocation for each point on the boundary of an achievable rate region are ob­ tained. In the case of half-duplex nodes, we propose a modified version of an existing cooperation scheme that, with jointly optimal power and channel resource allocation, can achieve a large fraction of the achievable rate region of the full-duplex case. An v efficient algorithm for the jointly optimal power and channel resource allocation is also developed for that scheme. For the cooperative multiple access channel with AF relaying, we consider optimal power and channel resource allocation for a system of two half-duplex source nodes that transmit orthogonal signals, and an efficient algorithm for the optimal power and channel resource allocation is developed. This efficient algorithm is based on a closed-form solution for the optimal power allocation for a given channel resource al­ location and on showing that the channel resource allocation problem is quasi-convex. The analysis of the optimal power allocation for a given channel resource allocation shows that the existing scheme that we consider does not use the channel resource efficiently. Therefore, we propose a modified cooperation scheme that maintains the orthogonality property of the original scheme, but provides larger achievable rate regions than those provided by the original scheme. For the multiple access relay channel, the optimal allocation of the relay power and the channel resource between different source nodes is considered in order to maximize the achievable rate region. Four relaying strategies are used; namely, regenerative decode-and-forward, non-regenerative decode-and-forward, amplify-and-forward, and compress-and-forward. For each of these strategies, an efficient algorithm is developed for the jointly optimal power and channel resource allocation. These algorithms are based on closed-form solutions for the optimal power allocation for a given resource allocation and on proving and exploiting the quasi-convexity of the joint allocation problem. The algorithms developed for the multiple access relay channel can be used for homogeneous (using the same relaying strategy for all users) or heterogeneous (using different relaying strategies with different users) relaying and for any number of users.