A robust demodulation method based on signal intensity in wireless laser communications

Laser communication is widely used in modern communication systems because its advantages of high secrecy, large capacity and strong anti-interference ability. Pulse Position Modulation (PPM) is used as an excellent modulation method in laser communications. However, in practical applications, the received signal intensity changes with the communication alignment beam area, which is roughly a trapezoidal or triangular envelope. So there is a lower intensity at the both ends which can reduce the demodulation probability, and that may cause a high bit error rate (BER). In this paper, we propose a robust demodulation method based on signal intensity, and based on an efficient frame format, the adaptive demodulation threshold is derived. Numerical results validate the effectiveness of the proposed frame recombination demodulation method. Compared with the traditional demodulation, the proposed scheme could ensure the demodulation accuracy, and has better BER performance.