Modulation Set Optimization for the Improved Complex Quadrature SM

Abstract

At each channel use, the complex quadrature spatial modulation (CQSM) transmits two signal symbols drawn from two disjoint modulation sets. The indices of the antennas from which symbols are transmitted also carry information. In the improved CQSM (ICQSM), an additional antenna is used to transmit the second signal symbol only when the indices of the antennas to be used for transmission are equal. Conventionally, the second modulation set is a rotated version of the first, where the rotation angle is optimized such that the average unconditional error probability (AUP) is reduced. In this paper, we propose a low-complexity method to design the PSK modulation sets based on reducing the AUP. After introducing min-BER and max-min , two exhaustive search methods, we analytically show that the AUP depends on Euclidean distance between transmitted vectors, which in turn depends on the power of signal symbols, the Euclidean distance between the symbols of each modulation set, and the Euclidean distance between the symbols of the two sets. The optimal rotation angle is analytically derived for any modulation order and the radii of the modulation sets are optimized such that AUP is reduced for a wide range of system configurations. The simulation results show that more than 3 dB of power gain is achieved in the case of 16PSK, where higher gains are achieved for higher modulation orders. These gains are achieved at no computational cost because the optimization does not depend on the channel realization.

Signal Shaping for Generalized Spatial Modulation and Generalized Quadrature Spatial Modulation

“…However, the arXiv:1901.09318v1 [eess.SP] 27 Jan 2019 design for more spectral-efficient multiple-data-stream GenSM was left unconsidered. Besides, little work is known on the constellation design for GenQSM other than [16] proposed a heuristic signal constellation optimization for QSM and [17] studied a lattice-code-based constellation optimization strategy for GenQSM. These are based on predefined codebooks and can be viewed as an optimization strategy in the discrete space.…”

Generalized Complex Quadrature Spatial Modulation

“…The proposed modification is named improved CQSM (ICQSM) in [18]. The modulation set design of the ICQSM was addressed in [19]. Notice that the CQSM can be conceptualized based on the conventional SM or the GSM, and not as an extension of the QSM.…”

“…where the maximum value of equals 2 6 as shown in [19]. The term Ω is a function of the signal symbols ( 1 , 2 ,̃1,̃2) and , and is the frequency of Ω , where…”

Constellation design and performance analysis of the parallel spatial modulation

“…The conventional GSM was extended to multiple active antennas, where the number of independent signal symbols transmitted at each channel use is equivalent to the number of activated antennas . Similar extensions of SM that achieve higher spectral efficiency through transmitting two signal symbols at each channel use were also introduced . The first signal symbol is drawn from a conventional constellation while the second is drawn from a rotated constellation, where the rotation angle is optimized such that the error probability is reduced.…”

“…19 Similar extensions of SM that achieve higher spectral efficiency through transmitting two signal symbols at each channel use were also introduced. [20][21][22][23] The first signal symbol is drawn from a conventional constellation while the second is drawn from a rotated constellation, where the rotation angle is optimized such that the error probability is reduced.…”