RZ‐PPM impulse tone‐based CSI estimation for adaptive threshold decision in FSO communications

Abstract

AbstractThis paper proposes a return‐to‐zero pulse position modulation (RZ‐PPM) impulse tone‐based channel state information (CSI) estimation for adaptive threshold decision (ATD) in free‐space optical (FSO) communications. RZ‐PPM is characterized by impulse tones in the spectrum. Therefore, CSI can be extracted by applying a local oscillator (LO) with the frequencies of impulse tones and low pass filter, which is then used to realize ATD. The proposed method was studied in simulation under RZ‐PPM signals with various number of pulse positions and frequencies of LO. The simulation results show that in FSO communication systems, the use of optimized weighting factor for impulse tone CSI estimation method significantly improves the performance in the absence of accurate CSI, approaching the performance of the traditional ATD with precise CSI knowledge. It proves that the proposed technique was feasible for adaptation in FSO communication systems.