Finite-Cardinality Single-RF Differential Space-Time Modulation for Improving the Diversity-Throughput Tradeoff

The matrix-based differential encoding invoked by Differential Space-Time Modulation (DSTM) typically results in an infinite-cardinality of arbitrary signals, despite the fact that the transmit antennas (TAs) can only radiate a limited number of patterns. As a remedy, the recently developed differential spatial modulation (DSM) is capable of avoiding this problem by conceiving a beneficial sparse signal matrix design, which also facilitates low-complexity single-RF signal transmission. Inspired by this development, the differential space-time block code using index shift keying (DSTBC-ISK) further introduces a beneficial diversity gain without compromising the DSM’s appealingly low transceiver complexity. However, the DSTBC-ISK’s performance advantage tends to diminish as the throughput increases, especially when an increased number of Receive Antennas (RAs) is used. By contrast, the classic Differential Group Code (DGC) that actively maximizes its diversity gain for different multiple-input-multiple-output (MIMO) system setups is capable of achieving a superior performance, but its detection complexity grows exponentially with the throughput. Against this background, we propose the differential space-time shift keying using Diagonal Algebraic Space-Time scheme, which is the first DSTM that is capable of achieving the DGC’s superior diversity gain at high throughputs without compromising the DSM’s low transceiver complexity. As a further advance, we also conceive a new differential space-time shift keying using Threaded Algebraic Space-Time arrangement, which is capable of achieving an even further improved diversity gain at a substantially reduced signal detection complexity compared to the best DGCs. Furthermore, in order to strike a practical tradeoff, we develop a generic multi-element and multi-level-ring Amplitude Phase Shift Keying design, and we also arrange for multiple reduced-size DSTM sub-blocks to be transmitted in a permuted manner, which exhibits an improved diversity-throughput tradeoff.

差分空时调制（DSTM）所采用的基于矩阵的差分编码通常会导致任意信号具有无限基数，尽管发射天线（TAs）只能辐射有限数量的模式。作为一种补救措施，近期发展的差分空间调制（DSM）能够通过设计一种有益的稀疏信号矩阵来避免这一问题，这也有利于低复杂度的单射频信号传输。受此发展的启发，采用索引移位键控的差分空时分组码（DSTBC - ISK）在不损害DSM极具吸引力的低收发器复杂度的情况下，进一步引入了有益的分集增益。然而，随着吞吐量的增加，DSTBC - ISK的性能优势往往会减弱，特别是当使用更多数量的接收天线（RAs）时。相比之下，经典的差分分组码（DGC）针对不同的多输入多输出（MIMO）系统设置积极最大化其分集增益，能够实现卓越的性能，但其检测复杂度随着吞吐量呈指数增长。在此背景下，我们提出了采用对角代数空时方案的差分空时移位键控，这是第一种能够在高吞吐量下实现DGC卓越的分集增益且不损害DSM低收发器复杂度的DSTM。作为进一步的进展，我们还构思了一种采用线程代数空时排列的新的差分空时移位键控，与最佳的DGC相比，它能够以大幅降低的信号检测复杂度实现进一步提高的分集增益。此外，为了达成实际的权衡，我们开发了一种通用的多元素和多级环幅相移键控设计，并且我们还安排以置换的方式传输多个尺寸减小的DSTM子块，这展现出了一种改进的分集 - 吞吐量权衡。