摘要：In wireless communications, one of the major active research areas is cooperative communications, which has been recognized as one of the promising techniques for future high speed networks. As we recall in the past modem designs and high speed wired communications systems, coding and modulation had played one of the major roles for their advancements, such as trellis coded modulation (TCM) and OFDM (or DMT) systems, we believe that coding and modulation for cooperative communications will play a similar role for high speed wireless communications systems. The main goal of this special issue is to publish the research advances in this important area and to bring together the state-of-art research contributions that address the major opportunities and challenges of coding and modulation for cooperative communications. This special issue includes eight papers that cover a broad range of interesting topics related to coding and modulation for cooperative communications as follows. The first two papers are invited papers that have the tutorial nature. In the invited paper "DMT of wireless networks: an overview," Vinodh, Prakash, Lalitha, and Kumar gave a comprehensive overview on the DMT of half-duplex multi-hop wireless networks. For some specific scenarios, codes that are able to achieve the DMT are also identified and discussed. In the invited paper "Distributed space-time block codes for two-hop wireless relay networks," Harshan and Rajan presented a nice survey of distributed space-time block code designs, which covers different classes of DSTBC depending on whether relays are synchronized or not, and whether amplify-and-forward protocol or decode-and-forward protocol is employed. The next six papers are contributed papers. In the paper “Performance bounds for bit-interleaved space-time coded modulation with iterative decoding based cooperative network,” Khan, Tanoli, and Rajatheva analyzed the performance of the BICM-ID based cooperative relay networks over Nakagami-m and Rayleigh fading channels. They proposed to use STC and OSTBC in the cooperative transmission and derived the MGF of the proposed system. In the paper “Performance analysis of wireless dynamic cooperative relay networks using fountain codes,” Lei, Xie, and Li analyzed the performance of a wireless relay network employing fountain codes. They compared the performance with the normal relay network without using fountain codes. In the paper "On the full diversity property of a space-frequency code family with multiple carrier frequency offsets in cooperative communication systems," Tian, Xia, Ma and Ching presented a class of robust space-frequency codes that are able to achieve full diversity even when there are multiple carrier frequency offsets from relay nodes. Suboptimal detection methods which preserve the full diversity were also proposed. In the paper "Downlink cooperative transmission by superposition modulation: performance analysis and power allocation strategy," Jia, Wu, Lin and Li analyzed two downlink cooperative transmission strategies based on superposition modulations. Their results showed that the superposition schemes can achieve up to 5dB in performance gain compared to classical downlink cooperative schemes. In the paper “Cooperative communications for reliable data transport with fountain codes,” Qin, Feng, and Zhang proposed to combine fountain codes at transport layer with cooperative relay communications to provide reliability and robustness for data transmission in wireless networks. The method proposed in this paper can achieve significant improvement in terms of data transport efficiency. Also the method has strong robustness to packet losses on wireless links for data transfer. In the paper "A simple amplify-and-forward relaying scheme based on clipping and forwarding for dual-hop transmissions," Zhang and Gong proposed a simple amplify-and-forward relaying scheme, referred to as clip-amplify-forward, which requires no channel estimation at the relay node and admits simple design of relay with a fixed amplification gain. The performance was shown to be almost identical to the one of amplify-and-forward protocol.
