Adaptive Spatial Modulation Scheme Research Articles

Flexible Generalized Spatial Modulation for Visible Light Communications

Adaptive spatial modulation (ASM) varies the modulation size across the transmit light-emitting diodes (LEDs) to improve the overall spectral efficiency of visible light communication (VLC) systems. This article proposes a novel ASM scheme, referred to as flexible generalized spatial modulation (FGSM), for VLC systems. The proposed FGSM system changes the modulation sizes over the LEDs and the number of active LEDs, to improve the average symbol error rate (SER) and spectral efficiency compared to ASM with a fixed overall number of LEDs. The modulation sizes are selected in order to optimize the average SER under a predefined spectral efficiency value. A closed-form expression of approximate SER is derived along with decoding complexity calculations for the proposed system. Numerical results are provided to confirm the superiority of the proposed system and to support theoretical derivations.

Adaptive Spatial Modulation over MmWave Channel with UPA

Spatial modulation (SM) utilizes the transmit antenna index and a quadrature amplitude modulation (QAM) symbol chosen from a constellation diagram to improve spectral efficiency (SE) comparing to conventional modulation scheme. However, in the conventional SM system, the modulation mode applied to the active antenna is fixed, which degrades the bits error rates (BER) and spectral efficiency (SE) performance. Moreover, a large number of researches on SM systems focus on the utilization of the uniform linear array (ULA) for transmission, which only considers the transmission on the horizontal domain while ignoring that on the vertical domain. Therefore, in this paper, we propose an adaptive spatial modulation (ASM) scheme with uniform planar array (UPA) over millimeter wave (mmWave) channels, which combines SM with adaptive modulation (AM) to enhance the performance of SE. To further improve the bits error rates (BER) performance, we develop an UPA-based ASM scheme with transmit antenna selection (TAS). We then analyse the BER and SE performance of both the two ASM scheme and obtain the closed-form expression for SE of the UPA-based ASM scheme with TAS algorithm. The simulations demonstrate that the proposed ASM schemes can achieve a considerable SE and a relatively low BER.

Instantaneous Bit Error Rate Based ASM Scheme for MPSK Spatial Modulation

In this paper, we propose an instantaneous bit error rate (IBER) based adaptive spatial modulation (ASM) scheme for the M-ary phase shift keying (MPSK) constellation (ASM-MPSK). In the proposed ASM-MPSK system, the combination of MPSK modulation order and number of transmit antennas is chosen based on the one that yields the smallest IBER while keeping the average transmission bit rate (TBR) constant. Furthermore, a low complexity maximum likelihood (ML) detection scheme for MPSK SM is employed which significantly reduces the complexity of the proposed system compared with other adaptive modulation schemes that use the high complexity ML detector for detection. Additionally, in this paper, we also analyse the computational complexity for the proposed ASM-MPSK. The simulation results indicate that the proposed scheme provides a significant improvement in terms of the error performance compared to conventional MPSK SM systems under a particular TBR; for TBR = 5 bits/s/Hz, a performance gain of approximately 4 dB had been achieved at a BER of 1 × 10−6.