Performance Evaluation of LDPC-Coded Power Series Based Málaga (Ḿ) Distributed MIMO/FSO Link With M-QAM and Pointing Error

In this work, the performance evaluation of Low-Density-Parity-Check (LDPC) based Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) based Free Space Optical (FSO) link with Málaga (Ḿ) channel model is analyzed. The performance in terms of Gain (diversity and combining) analysis
$\delta \text{G}$
(N, M) and Bit Error Rate (BER), outage probability, ergodic capacity, spectral efficiency and Link distance (L) concerning Signal to Noise Ratio (SNR) is evaluated. The Meijer-G function gives complexity in MIMO mathematical analysis. As a solution, a new Probability Density Function (PDF) based on power series representation has been proposed with M-Quadrature Amplitude Modulation
$(M-ary\,\,QAM)$
. With the proposed PDF, the closed-form Bit Error Rate (BER) derivation, Asymptotic BER derivation, Outage probability expression are derived, and the enhancement is observed for the MIMO/OFDM link in terms of Bit Error Rate (BER) and Signal to Noise Ratio (SNR) with pointing error (PE) and atmospheric turbulence (AT). The Maximal Ratio Combining (MRC) achieves a gain of 3.5dB and 7.8dB SNR gain over Equal Gain Combining (EGC) and Selection Combining (SC) scheme for negligible Pointing Error (PE), i.e.,
$\xi =10.15$
at BER 10
⁻⁶
. The proposed PDF, along with M-QAM and Málaga (Ḿ) distribution offers power efficiency, reduction in BER, and high SNR gain compared to Single Input Single Output (SISO) and Single Input Multiple Output (SIMO) Free Space Optical (FSO) link. The regular LDPC coding techniques are adopted with a 1/2 code rate and applied to simulation results to obtain high coding gain. The proposed MIMO/FSO link provides high SNR gain of 5dB and transmission link distance of 12km over SIMO and SISO FSO link. This work gives the in-depth analysis of vital factors affecting the FSO link performance and helps in mitigating them to analyze and design an effective system and opens widely for digital applications like smart city application, 5G and beyond 5G, Internet of Things (IoT), railway and defense applications, etc.,