An improved generalized spatial modulation scheme for indoor visible light communications

This paper proposes an improved generalized spatial modulation (iGSM) scheme for indoor visible light communication (VLC), which can significantly improve the spectral efficiency (SE) of traditional generalized spatial modulation. The iGSM uses N_t transmitters, i.e., light emitting diodes (LEDs), and activates N_a (0 < N_a ≤ N_t) LEDs to transmit the signal. The proposed iGSM can achieve 2^Nt LED groups by activating all LEDs for twice, and these two LED groups are distinguished by setting different intensity levels. This paper also compares the SE between iGSM and other modulation techniques, such as spatial modulation (SM), quadrature spatial modulation (QSM), enhanced spatial modulation (ESM), and traditional generalized spatial modulation. We get the conclusion that the SE of iGSM can achieve more than 60% increase compared with the generalized spatial modulation. At last, we compare the bit error rate (BER) performance between iGSM and generalized spatial modulation when the SE is 5 bpcu and 6 bpcu (the bpcu is the term of SE and it means bits per channel use), and the proposed iGSM scheme can achieve about 3 dB gain than the generalized spatial modulation when the BER is about 10'⁴.