Optimum Resource Allocation for Amplify-and-Forward Relay Networks With Differential Modulation

The optimum resource allocation is an important method to improve the error performance and energy efficiency of wireless relay networks. In this paper, we consider the resource allocation as a two-dimensional optimization problem; that is, the energy optimization and the location optimization. Differential modulation which bypasses the channel estimation at the receiver is investigated using the amplify-and-forward protocol for a relay system with arbitrary number of relays. At high signal-to-noise ratio (SNR), we first derive the average symbol error rate for systems with and without a direct link. Then, the optimum resource allocation schemes which minimize the system error are developed. The comparisons based on analytical and simulated results confirm that the optimized systems provide considerable improvement over unoptimized ones, and that the minimum error can be achieved via the joint energy-location optimization.