Multi‐colour LED specified bipolar colour shift keying scheme for visible light communications

Colour shift keying (CSK) can achieve significant performance gains in multi‐colour visible light communications (VLCs). Existing CSK constellations are designed within the positive domain which satisfies the requirement of non‐negative optical intensity modulations. A scheme is proposed to incorporate spatial modulation with a CSK design by grouping LEDs. In this way, the CSK constellation is optimised within the entire real domain and hence achieves a larger minimum Euclidean distance so as to enhance the bit error rate (BER) performance. Simulation results show a noticeable performance gain by the proposed scheme compared with traditional CSK under ideal light‐of‐sight optical channels. Further, by experimental tests, an even more pronounced BER gain is achieved by the proposed scheme over real VLC channels.