Space-Time Block Coded Spatial Modulation for Indoor Visible Light Communications

TL;DR

This paper proposes a novel space-time block coded spatial modulation scheme for indoor visible light communication, improving reliability and data rate by integrating quasi-orthogonal STBC with spatial modulation and analyzing its performance.

Contribution

It introduces a combined QOSTBC and SM scheme for VLC, generalizes the results for any number of LEDs and modulation size, and provides a tight BER bound with performance comparisons.

Findings

QOSTBC with SM improves BER over RC-SM.

The scheme enhances data rate and reliability in indoor VLC.

Performance analysis confirms the advantages over existing methods.

Abstract

Visible light communication (VLC) has been recognized as a promising technology for handling the continuously increasing quality of service and connectivity requirements in modern wireless communications, particularly in indoor scenarios. In this context, the present work considers the integration of two distinct modulation schemes, namely spatial modulation (SM) with space time block codes (STBCs), aiming at improving the overall VLC system reliability. Based on this and in order to further enhance the achievable transmission data rate, we integrate quasi-orthogonal STBC (QOSTBC) with SM, since relaxing the orthogonality condition of OSTBC ultimately provides a higher coding rate. Then, we generalize the developed results to any number of active light-emitting diodes (LEDs) and any M-ary pulse amplitude modulation size. Furthermore, we derive a tight and tractable upper bound for the corresponding bit error rate (BER) by considering a simple two-step decoding procedure to detect the indices of the transmitting LEDs and then decode the signal domain symbols. Notably, the obtained results demonstrate that QOSTBC with SM enhances the achievable BER compared to SM with repetition coding (RC-SM). Finally, we compare STBC-SM with both multiple active SM (MASM) and RC-SM in terms of the achievable BER and overall data rate, which further justifies the usefulness of the proposed scheme.