Demonstration of the Merit and Limitation of Generalised Space Shift Keying for Indoor Visible Light Communications

This paper demonstrates the merit and de-merit of a low complexity, multiple transmitter generalised space shift keying (GSSK) signalling technique for short range indoor visible light communications. To illustrate the high spectral efficiency credential of GSSK, an array of Nt white light emitting diodes (LEDs) is used to demonstrate Nt bits/symbol transmission by exploiting the natural differences in the channel gains of the spatially separated LED array. With two low power white LEDs each having a 3 dB modulation bandwidth of 8 MHz, data transmission of up to 40 Mbits/s ( 20 Mbaud) is demonstrated. For an average received electrical signal power of -12.5 dBm and 2×10⁴ data symbols, the measured symbol error rate at 20 Mbaud is 7 ×10^-2 and 5 ×10^-5 at 10 Mbaud ( 20 Mbits/s) without any error control coding. The GSSK technique is experimentally shown to be most suitable for a fixed configuration as its performance is quite sensitive to receiver mobility.