Space-time shift keying-aided orthogonal time frequency space modulation-based multiple access (STSK-OTFS-MA) is proposed for reliable uplink transmission in high-Doppler scenarios. As a beneficial feature of our STSK-OTFS-MA system, extra information bits are mapped onto the indices of the active dispersion matrices, which allows the system to enjoy the joint benefits of both STSK and OTFS signalling. Due to the fact that both the time-, space- and DD-domain degrees of freedom are jointly exploited, our STSK-OTFS-MA achieves increased diversity and coding gains. To mitigate the potentially excessive detection complexity, the sparse structure of the equivalent transmitted symbol vector is exploited, resulting in a pair of low-complexity near-maximum likelihood (ML) multiuser detection algorithms. Explicitly, we conceive a progressive residual check-based greedy detector (PRCGD) and an iterative reduced-space check-based detector (IRCD). Then, we derive both the unconditional single-user pairwise error probability (SU-UPEP) and a tight bit error ratio (BER) union-bound for our single-user STSK-OTFS-MA system employing the ML detector. Furthermore, the discrete-input continuous-output memoryless channel (DCMC) capacity of the proposed system is derived. The optimal dispersion matrices (DMs) are designed based on the maximum attainable diversity and coding gain metrics. Finally, it is demonstrated that our STSK-OTFS-MA system achieves both a lower BER and a higher DCMC capacity than its conventional spatial modulation (SM) {and its orthogonal frequency-division multiplexing (OFDM) counterparts. As a benefit, the proposed system strikes a compelling BER vs. system complexity as well as BER vs. detection complexity trade-offs.

翻译：本文提出了基于时空移位键控辅助的正交时频空间调制的多址接入（STSK-OTFS-MA）方案，用于高多普勒场景下的可靠上行链路传输。作为STSK-OTFS-MA系统的一个有益特性，额外信息比特被映射到激活色散矩阵的索引上，这使得系统能够同时享受STSK和OTFS信号处理带来的联合优势。由于联合利用了时域、空域和DD域的自由度，所提出的STSK-OTFS-MA实现了更高的分集增益和编码增益。为了缓解潜在的高检测复杂度，利用等效传输符号向量的稀疏结构，提出了两种低复杂度的近最大似然（ML）多用户检测算法。具体而言，我们设计了一种渐进残差检测的贪婪检测器（PRCGD）和一种迭代降维检测器（IRCD）。随后，我们推导了采用ML检测器的单用户STSK-OTFS-MA系统的无条件单用户成对错误概率（SU-UPEP）以及严格的误比特率（BER）联合上界。此外，还推导了所提出系统的离散输入连续输出无记忆信道（DCMC）容量。基于最大可达分集与编码增益度量，设计了最优色散矩阵（DMs）。最后，仿真结果表明，与传统空间调制（SM）及其对应的正交频分复用（OFDM）方案相比，所提出的STSK-OTFS-MA系统实现了更低的BER和更高的DCMC容量。因此，该系统在BER与系统复杂度之间以及BER与检测复杂度之间达成了有吸引力的权衡。