Quadrature spatial modulation (QSM) was recently proposed to increase the spectral efficiency of spatial modulation. In QSM, the real and imaginary parts of a symbol are transmitted independently from different antennas. A new spatial modulation technique, termed signed quadrature spatial modulation (SQSM), is introduced in this paper. Unlike QSM, SQSM creates four-dimensional spatial constellation, and hence results in higher system throughput. This technique extends the traditional spatial-constellation dimension into ±\pm in-phase and quadrature-phase dimensions. The ensuing constellation consists of four antenna indices, which are chosen independently in order to transmit the real and imaginary parts of the modulated symbols and their inverse. The performance of the proposed technique is compared to the most-recent SM techniques, namely, QSM, double SM, and improved QSM (IQSM). Numerical results demonstrate that SQSM provides significant performance gains (3–7 dB), particularly when a large number of transmit antennas is used. This comes with a marginal increase in computational complexity compared to QSM and SM. Also, while IQSM can be competitive with SQSM in some cases, SQSM has a much lower computational complexity, e.g., 46% reduction in complexity in case of 16 transmit antennas and 16 bps/Hz.

中文翻译：

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MIMO 系统的有符号正交空间调制


最近提出了正交空间调制（QSM）来提高空间调制的频谱效率。在 QSM 中，符号的实部和虚部是从不同的天线独立传输的。本文介绍了一种新的空间调制技术，称为有符号正交空间调制（SQSM）。与 QSM 不同，SQSM 创建四维空间星座，因此可以提高系统吞吐量。该技术将传统的空间星座维度扩展到±μm同相和正交相位维度。随后的星座由四个天线索引组成，这些天线索引是独立选择的，以便传输调制符号的实部和虚部及其逆。所提出技术的性能与最新的 SM 技术（即 QSM、双 SM 和改进的 QSM (IQSM)）进行了比较。数值结果表明，SQSM 提供了显着的性能增益 (3-7 dB)，特别是在使用大量发射天线时。与 QSM 和 SM 相比，计算复杂度略有增加。此外，虽然IQSM在某些情况下可以与SQSM竞争，但SQSM具有低得多的计算复杂性，例如，在16个发射天线和16 bps/Hz的情况下，复杂性降低了46%。