Optimized Power Allocation for Pairwise Cooperative Multiple Access
Wessam Mesbah, Timothy N. Davidson · IEEE Transactions on Signal Processing · 2008
Multiple access schemes in which the transmitting nodes are allowed to cooperate have the potential to provide higher quality of service than conventional schemes. In the class of pair-wise cooperative multiple access schemes in which channel state information is available at the transmitters, the allocation of transmission power plays a key role in the realization of these quality of service gains. Unfortunately, the natural formulation of the power allocation problem for full-duplex cooperative schemes is not convex. It is shown herein that this non-convex formulation can be simplified and recast 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 obtained. In practice, a half-duplex cooperative scheme, in which the channel resource is partitioned in such a way that interference is avoided, may be preferred over a full-duplex scheme. The channel resource is often partitioned equally, but we develop an efficient algorithm for the joint allocation of power and the channel resource for a modified version of an existing half-duplex cooperative scheme. We demonstrate that this algorithm enables the resulting scheme to attain a significantly larger fraction of the achievable rate region for the full duplex case than the underlying scheme that employs a fixed resource allocation.