Abstract
We study the problem of joint power and channel resource allocation for orthogonal multiple access relay (MAR) systems in order to maximize the achievable rate region. Four relaying strategies are considered; namely, regenerative decode-and-forward (RDF), nonregenerative decode-and-forward (NDF), amplify-and-forward (AF), and compress-and-forward (CF). For RDF and NDF we show that the problem can be formulated as a quasiconvex problem, while for AF and CF we show that the problem can be made quasiconvex if the signal-to-noise ratios of the direct channels are at least -3dB. Therefore, efficient algorithms can be used to obtain the jointly optimal power and channel resource allocation. Furthermore, we show that the convex subproblems in those algorithms admit a closed-form solution. Our numerical results show that the joint allocation of power and the channel resource achieves significantly larger achievable rate regions than those achieved by power allocation alone with fixed channel resource allocation. We also demonstrate that assigning different relaying strategies to different users together with the joint allocation of power and the channel resources can further enlarge the achievable rate region.
Highlights
In multiple access relay (MAR) systems, several source nodes send independent messages to a destination node with the assistance of a relay node [1,2,3,4]
We provide comparisons between the achievable rate regions obtained with jointly optimal power and channel resource allocation and those obtained using optimal power allocation alone, with equal channel resource allocation, r = 0.5
For small values of R1 one would expect the values of R2 that can be achieved by the CF and AF relaying strategies to be greater than those obtained by Regenerative decode-and-forward (RDF) and Nonregenerative decode-and-forward (NDF), since the values of R2 that can be achieved by RDF and NDF will be limited by the source-relay link, which is weak for node 2
Summary
In multiple access relay (MAR) systems, several source nodes send independent messages to a destination node with the assistance of a relay node [1,2,3,4]. The practical importance of solving the problem of the joint allocation of power and channel resources is that it typically provides a substantially larger achievable rate region than that provided by allocating only the power for equal (or fixed) channel resource allocation, as will be demonstrated in the numerical results. Those results will demonstrate the superiority of the NDF and CF relaying strategies over the RDF and AF strategies, respectively, which is an observation that is consistent with an observation in [13] for the case of power allocation with equal resource allocation. We will demonstrate that joint allocation of the relaying strategy together with the power and channel resources, rather assigning the same relaying strategy to all users, can further enlarge the achievable rate region
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