Cooperative scheme using STNC for uplink SC-FDMA and downlink OFDMA system

Orthogonal frequency-division multiplexing (OFDM) has recently developed as one of the most popular schemes to overcome multipath fading. Single carrier frequency division multiple access (SC-FDMA) has also been adopted as an alternative of OFDMA for uplink transmission in UTRA LTE. To improve the performance of OFDMA and SC-FDMA, cooperative communication can be used. However, traditional cooperative protocol for multi-carrier system suffers with the issue of imperfect synchronization. TDMA scheme in which each node in the network transmits symbols in its dedicated time slot can solve the asynchronous problem but gives rise to large time delay. In this paper, a novel cooperative scheme by using spacetime network coding (STNC) for uplink SC-FDMA and downlink OFDMA system is proposed. For a SC-FDAM/OFDMA system consists of N users and R relay nodes, a full diversity order of R +1 can be achieved while keeping the delay low and the issue of asynchronization is eliminated. Compare with the TDMA scheme where N(R +1) time slots is required to complete the transmission of a symbol frame, only N + R time slots is needed in our proposed scheme by using STNC at relay nodes.