Co-efficient Vector Based Differential Distributed Quasi-Orthogonal Space Time Frequency Coding

Distributed space time frequency coding (DSTFC) schemes address problems of performance degradation encountered by cooperative broadband networks operating in highly mobile envi-ronments. Channel state information (CSI) acquisition is however impractical in such highly mobile environments. Therefore, to address this problem, designers focus on incorporating dif-ferential designs with DSTFC for signal recovery in environments where neither the relay nodes nor destination have CSI. Traditionally, unitary matrix based differential designs have been used to generate the differentially encoded symbols and codeword matrices. Unitary based de-signs are suitable for cooperative networks that utilize the amplify-and-forward protocol where the relay nodes are typically required to forego differential decoding. In considering other sce-narios where relay nodes are compelled to differentially decode and re-transmit information signals, we propose a novel co-efficient vector differential distributed quasi-orthogonal space time frequency coding (DQSTFC) scheme for decode-and-forward cooperative networks. Our proposed space time frequency coding scheme relaxes the need for constant channel gain in the temporal and frequency dimensions over long symbol periods, thus performance degradation is reduced in frequency-selective and time-selective fading environments. Simulation results illus-trate the performance of our proposed co-efficient vector differential DQSTFC scheme under different channel conditions. Through pair-wise error probability analysis, we derive the full diversity design criteria for our code.