An SCMA-based uplink inter-cell interference cancellation technique for 5G wireless systems

In future 5G wireless networks, inter-cell interference (ICI) is perceived as one of the most critical performance bottlenecks. Traditionally, the interference is treated as an additional source of noise, recent advances in information theory show that interference is not necessarily an opponent, but might be decoded and cancelled to obtain a larger capacity region. In this paper, a sparse code multiple access (SCMA) based uplink ICI cancellation technique is proposed to enhance the performance of the cell-edge users by jointly decoding the desired signal and the interference signal at the base stations. Unlike the orthogonal transmission schemes such as fractional frequency reuse in 4G, the proposed non-orthogonal SCMA-based scheme allows several cell-edge users to share the same time-frequency resource blocks (RBs). The sparse codewords are designed to make each user spread its data on a small set of RBs to achieve frequency and interference diversity, and make the near-optimal detection feasible with moderate complexity through iterative message passing algorithm (MPA). Then an open-loop MIMO transmission scheme which combines SCMA with Alamouti code is proposed to achieve full space-time-frequency diversity. Simulation results show that when there is no correlation among resource blocks and the antenna configuration is 1×1, the proposed SCMA-based scheme has about 2dB gain for uplink cell-edge users in multi-cell scenario compared with the FFR-based ICI coordination scheme in LTE networks. The gain becomes larger when combined with the existing MIMO technique. In addition, the SCMA-based scheme is also proved to be more robust to the burst interference.