Reduction of the beam pointing error for improved free-space optical communication link performance

Abstract

Free-space optical communication is emerging as a low-power, low-cost, and high data rate alternative to radio-frequency communication in short-to medium-range applications. However, it requires a close-to-line-of-sight link between the transmitter and the receiver. This paper proposes a robust H ∞ control law for free-space optical (FSO) beam pointing error systems under controlled weak turbulence conditions. The objective is to maintain the transmitter-receiver line, which means the center of the optical beam as close as possible to the center of the receiving aperture within a prescribed disturbance attenuation level. First, we derive an augmented nonlinear discrete-time model for pointing error loss due to misalignment caused by weak atmospheric turbulence. We then investigate the H ∞ -norm optimization problem that guarantees the closed-loop pointing error is stable and ensures the prescribed weak disturbance attenuation. Furthermore, we evaluate the closed-loop outage probability error and bit error rate (BER) that quantify the free-space optical communication performance in fading channels. Finally, the paper concludes with a numerical simulation of the proposed approach to the FSO link's error performance.Keywords Free-space optical (FSO) communications • H ∞ pointing error control • Weak turbulence • Lognormal distribution • Linear Matrix Inequality (LMI).

Kalman Filter Design for Intermittent Optical Wireless Communication Systems on Time Scales

“…However, it is apparent that the LOS configuration depends on the precise alignment between the optical signal transmitter and the optical sensing receiver, which is even more challenging to achieve for slightly longer distance communication links [3]. Researchers have proposed some solutions to this problem, including H ∞ pointing error control [4], extremum seeking control [5], etc., in an attempt to solve the alignment problem of OWC systems. However, the control algorithms proposed in these works are only applicable to low-interference OWC Wenqi Cai, Bacem Ben Nasser, Taous Meriem Laleg-Kirati are with the Electrical and Computer Engineering Program, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia (e-mail: wenqi.cai@kaust.edu.sa; bacem.bennasser@kaust.edu.sa; taousmeriem.laleg@kaust.edu.sa).…”