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.
Bibliographical noteFunding Information:
Manuscript received June 15, 2007; revised May 2, 2008. First published June 10, 2008; current version published October 15, 2008. The associate editor co-ordinating the review of this manuscript and approving it for publication was Dr. Geert Leus. Part of the results in this paper were presented at the IEEE Military Communications Conference, Orlando, FL, 2007, and at the IEEE Global Communications Conference, Washington, DC, 2007. This work is supported in part by the Office of Naval Research by Grants #N00014-07-1-0868 and #N00014-07-1-0193.
- Differential modulation
- Relay networks
- Resource optimization
- Symbol error rate