High Efficient Modulation Techniques for In-Door Visible Light Communication

This paper describes state-of-the-art modulation techniques for visible-light-communications (VLCs) and proposes a new modulation technique, which is so-called generalized spatial pulse position modulation (GSPPM). Several modulation techniques, i.e., on-off-keying, pulse position modulation, pulse amplitude modulation and spatial modulation, are explained as background information for understanding proposed GSPPM technique. Combination of several modulation techniques used in GSPPM allows us to achieve relatively high data bit rates as compared to pulse position modulation (PPM), space-shift-keying (SSK) and spatial pulse position modulation (SPPM). The maximum obtainable rate of an in-door communication system depends on several parameters, which are considered and explained in this work. The symbol error probability of GSPPM and conventional techniques are evaluated using Monte Carlo simulation. It is shown that the error performance of GSPPM outperforms that of SSK and PPM. At symbol error rate of 10, SSK and SPPM require signal-to-noise ratio of about 134 and 127 dB, respectively, while 3 active pulses GSPPM and 7 active pulses GSPPM require only about 122 to 124 dB, respectively.