Adaptive Modulation for FSO IM/DD Systems With Multiple Transmitters and Receivers

Atmospheric turbulence is a major impairment in free space optical (FSO) communication systems. Since turbulence induced fading exhibits quasi-static characteristics, reliable feedback of channel state information is possible allowing the implementation of adaptive transmission. In this letter, we consider multiple-input single-output (MISO) and single-input multiple-output (SIMO) FSO systems with pulse position modulation (PPM) and pulse amplitude modulation (PAM). We propose an adaptive algorithm where the modulation size/type is adjusted according to the channel fading conditions. We formulate the design of adaptive algorithm to maximize the spectral efficiency under peak and average power constraints while maintaining a targeted value of outage probability. We present extensive Monte Carlo simulations to demonstrate the performance of proposed adaptive scheme over turbulence channels.

Automated summary

This letter proposes an adaptive algorithm for free space optical communication systems to address the impact of atmospheric turbulence. By reliable feedback of channel state information, adaptive transmission is implemented to adapt to turbulence-induced fading. The algorithm adjusts the modulation size/type according to the channel fading conditions to maximize spectral efficiency under peak and average power constraints, while maintaining a targeted value of outage probability. Extensive Monte Carlo simulations are presented to demonstrate the performance of the proposed adaptive scheme over turbulence channels.