Performance Evaluation of Multiuser Digital Color Shift Keying Using Pseudo-Noise Code with On-Off Signaling

In this paper, a digital color shift keying with code division multiplexing (DCSK/CDM) is proposed as a multiple access technique in visible light communications. Multiple multicolor LEDs were used in DCSK/CDM where only one color is activated in each multicolor LED at a single time. Therefore the information is encoded in the combinations of activated colors. The main advantage of DCSK/CDM over conventional CSK/CDM is avoiding the need of any digital-to-analog converters. Moreover, two type of pseudo noise codes for DCSK/CDM were considered; generalized modified prime sequence code (GMPSC) and Hadamard code with on-off signaling (HC). In particular, DCSK/CDM with HC improves the data transmission rate by employing sequence inversion keying (SIK) technique. In this paper, the symbol error rate (SER) and bit error rate (BER) performance of the DCSK/CDM systems using multiple RGB-LEDs (i.e., TLED: trichromatic LED) are evaluated through theoretical analysis in the multi-user case. It is shown that BER of DCSK/SIK can be improved by about 1 dBm compared with the DCSK/DS systems when the spectral efficiency over VLC network is 1.3 bit/sec/Hz. In addition, when the spectral efficiency per TLED is the same as 0.063 bit/sec/Hz/LED.