A Differential Modulation Scheme for Multihop Amplify-and-Forward Relaying Systems

In this paper, we propose a new differential modulation scheme for multihop communication systems with amplify-and-forward relaying. In the proposed scheme, each transmitted frame is divided into several blocks, and each block consists of one reference symbol and several normal symbols. The reference symbol in each block is differentially encoded based on the previous reference symbol, while the normal symbols are differentially encoded based on the reference symbol in the same block. The main advantage of the proposed scheme is allowing power allocation among the reference symbol and normal symbols to improve the system performance. Numeric results show that the gap between the proposed differential modulation scheme with a block length of 256 and the coherent receiver with perfect channel state information (CSI) is within 0.5dB in slow fading channels. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011]