This paper investigates an uplink coordinated multi-point (CoMP) coverage scenario, in which multiple mobile users are grouped for sparse code multiple access (SCMA), and served by the remote radio head (RRH) in front of them and the RRH behind them simultaneously. We apply orthogonal time frequency space (OTFS) modulation for each user to exploit the degrees of freedom arising from both the delay and Doppler domains. As the signals received by the RRHs in front of and behind the users experience respectively positive and negative Doppler frequency shifts, our proposed OTFS-based SCMA (OBSCMA) with CoMP system can effectively harvest extra Doppler and spatial diversity for better performance. Based on maximum likelihood (ML) detector, we analyze the single-user average bit error rate (ABER) bound as the benchmark of the ABER performance for our proposed OBSCMA with CoMP system. We also develop a customized Gaussian approximation with expectation propagation (GAEP) algorithm for multi-user detection and propose efficient algorithm structures for centralized and decentralized detectors. Our proposed OBSCMA with CoMP system leads to stronger performance than the existing solutions. The proposed centralized and decentralized detectors exhibit effective reception and robustness under channel state information uncertainty.

翻译：本文研究了一种上行协调多点（CoMP）覆盖场景，其中多个移动用户被分组用于稀疏码多址接入（SCMA），并由其前方和后方的远程无线电头端（RRH）同时提供服务。我们为每个用户应用正交时频空间（OTFS）调制，以利用延迟和多普勒域带来的自由度。由于用户前方和后方的RRH接收到的信号分别经历正负多普勒频移，我们提出的基于OTFS的SCMA（OBSCMA）与CoMP系统可以有效获取额外的多普勒和空间分集，以提升性能。基于最大似然（ML）检测器，我们分析了单用户平均误比特率（ABER）界，作为所提OBSCMA与CoMP系统ABER性能的基准。我们还开发了一种定制化的高斯近似与期望传播（GAEP）算法用于多用户检测，并提出了集中式和分布式检测器的高效算法结构。我们所提出的OBSCMA与CoMP系统比现有解决方案表现出更强的性能。所提出的集中式和分布式检测器在信道状态信息不确定的情况下展现出有效的接收能力和鲁棒性。