Minimum Sum Expected Distortion in Cooperative Networks

In this paper, we consider a wireless cooperative multimedia decode-and-forward network wherein one relay may assist multiple source-destination pairs. By exploiting the global channel state information at the relay, we propose a power allocation, a time allocation and an iterative joint power-time allocation algorithm to minimize the sum expected distortion. Firstly, we separately optimize the relay´s transmission power and the system transmission time allocated to each source-destination pair such that the sum expected distortion can be minimized. Then, we propose an iterative joint power-time allocation algorithm subject to the relay´s total power constraint to further improve the distortion performance. The proposed iterative algorithm is guaranteed to converge to an optimal, despite not necessarily globally optimal, point and can achieve the minimum sum expected distortion among all the schemes.