Performance of Optical Spatial Modulation in Indoor Multipath Channel

Abstract

In this paper, the performance of optical spatial modulation (OSM) in the indoor multipath optical wireless channel is investigated. Multipath propagation of the transmitted signal results in the temporal dispersion which causes intersymbol interference (ISI) especially in high-speed communications. OSM schemes have been investigated in line-of-sight (LOS) channels. However, given the recent trend in Gigabits per second communication, there is need to investigate the impact of the neglected higher-order reflections. Two variants of OSM are explored as case studies: optical space shift keying (OSSK) and spatial pulse position modulation (SPPM). The multipath-induced ISI is modelled to account for the spreading of the transmitted signal, and the analytical upper bound on the symbol error rate of both OSM schemes in multipath channel is derived. The derived analytical bounds are validated by closely matching simulation results. Furthermore, using the spatial distributions of the multipath-induced power penalty, the LOS channel response and the delay spread across the room, we demonstrate how the interaction between these parameters impacts error performance. Multipath-induced ISI has a significant adverse impact on the performance of OSM schemes, particularly on the detection of the activated transmitter as the incurred ISI can alter the channel gain of the received symbol.

Pairwise Coding for MIMO-OFDM Visible Light Communication

“…The vectors s k and x k are the k-th columns (i.e., the k-th SC) of S and X respectively. From (9) and (11), it can seen that the encoding process for the DPWC scheme can be defined completely in terms of the rotation angles. Hence, the design of the PWC technique is essentially dependent on using the optimal angles that maximize the minimum distance between the paired symbols constellations, which in turn minimizes the average error probability.…”

“…Also, by setting w k = s k , ∀ k, we derive the SCH-PWC scheme in which PWC is applied across the transmitter SCHs only. Furthermore, (9) and (11) indicate that DPWC encoding can be expressed in terms of multiplication with orthogonal matrices Ψ opt j,p = arg max…”

“…As a result, spectrally efficient modulation techniques such as pulse-amplitude modulation (PAM) [6] and optical Orthogonal frequency division multiplexing (OFDM) [7] have been explored to increase throughput. Moreover, Multiple-input multiple-output (MIMO) schemes using multiple LEDs and PDs to exploit additional degree of freedom, such as space and emitted colour of the optical sources and field of view of detectors are also prime candidates for improving the capacity and/or reliability of VLC systems [8], [9].…”

Performance Analysis of Optical Spatial Modulation in Atmospheric Turbulence Channel †

“…Typical of communication systems, especially in MIMO systems where knowledge of the channel state is required, the channel coefficients are assumed to be known at the RX. Based on the channel coefficients, the demodulator performs a maximum likelihood detection and makes a decision in favour of the TX index and PPM pulse position combination with the lowest Euclidean distance from the received signal [17,19].…”

Enhanced Multi-Level Multi-Pulse Modulation for MIMO Visible Light Communication

“…In other words, this scheme conveys a binary sequence through the index of the active LED and the pulse position of the transmitted signal. Furthermore, performance of SPPM with synchronization error and indoor multipath channel were analyzed in [14] and [15], respectively. Lately, spatial multiple pulse position modulation (SMPPM) has been proposed by allowing multiple active pulse slots [16], [17].…”