Optical Wireless Bandwidth Efficiency Enhancement Using Interval Shift Key

Abstract

Optical wireless communication is an emerging technology that has generated a vast number of interesting solutions to very complicated communication challenges. For example high data rate, high capacity, unlicensed spectrum, high security and minimum interference links. The optical systems are significantly different from radio frequency channels where amplitude, frequency and carrier phase are modulated, in optical signal the intensity is modulated. Unfortunately, optical sources suffer from long rise/fall times such as in light emitting diodes. This leads to inefficient utilization of optical communication bandwidth. Consequently, the modulation bandwidth is restricted to only few megahertz’s. Additionally, optical detectors exhibit large capacitance that prohibits high data rate. Moreover, the optical transmission power is limited by factors such as human eye safety and power consumption limits. In this paper, a modulation technique named Interval Shift Key (ISK) is used to modulate subcarriers of optical orthogonal frequency-division multiplexing (OFDM). This technique improves the bandwidth utilization and power efficiencies and reduce bit error rate (BER). The MATLAB software is used in this study to simulate BER and power efficiency in an adaptive white Gaussian noise channel. The technique is validated by comparing simulated and published results where good agreement is achieved.