Performance Evaluation of TQAM in Free-Space Optical (FSO) Communication

Abstract

In recent years, free-space optical technology has gained fame in communication systems due to its high data rates and license-free feature. Triangular quadrature amplitude modulation (TQAM) is an efficient modulation scheme that uses even bits per symbol and has low average symbol error probability than square quadrature amplitude modulation (SQAM). In this thesis, we analytically investigate the performance of subcarrier triangular quadrature amplitude modulation (SC-TQAM) corrupted by atmospheric turbulence in the presence of pointing errors in FSO communication. We have considered boresight displacement, P.E effect, and atmospheric turbulence. To represent the atmospheric turbulence we consider Log-normal, Rayleigh and Rician distributions which exhibit weak, moderate and strong weather effects. The P.E is employed using Rayleigh and Rician distribution that incorporates zero and non-zero boresight displacement respectively. The moment generating functions of these models have been used to reach final results. P.E is modeled using an optical beam radius and receiver aperture radius. Analytical expressions are used to develop numerical results. The ASEP performance is observed against average received irradiance, optical beam radius, P.E standard deviation and receiver aperture radius. In the end, the ASEP performance is evaluated against SNR and Monte Carlo simulations are performed which validates the theoretical results.