MIMO Based GFDM with Channel Coding and Adaptive Decision Feedback Equalizer in Underwater Wireless Optical communication

Abstract

Underwater wireless optical communication (UWOC) technology was adopted recently to address the underwater communications' need for fast throughput and huge data transmission. In this system, Multiple Input Multiple Output (MIMO) transmission with the Generalized Frequency Division Multiplexing (GFDM) is implemented in UWOC System. Recently, the next-generation technology is made possible by using GFDM in MIMO systems. It combines the advantages of faster data rates with little out-of-band (OOB) emission and strong incoherent demodulation capacity. By employing Forward Error Correction (FEC) codes for channel encoding and decoding, including BCH and RS codes, to enhance system performance. Also, in order to provide efficient channel estimation, various equalizer methods such as Minimum Mean Square Error (MMSE), Zero Forcing (ZF) and NLMS decision feedback equalizers has been adopted at receiver side. Since the UWOC channel is mostly affected by turbulence, the channel’s temporal and geographical dispersion under various conditions have been investigated. In this work, Channel impulse response is obtained via Monte Carlo (MC) simulation while accounting for the absorption and scattering effects. The simulation results shows that BER performance of NLMS equalizer technique attain better performance in different code rates and the RS coding achieved the best BER of ~10-5 at less than 20dB itself. The pointing errors in UOC may occur due to uncertainties and environmental disturbances which could not be accurately assessed and controlled by optical alignment techniques. Hence, the BER performance of BCH coded and RS coded GFDM method with different pointing error have been analyzed and spatial diversity significantly reduces fading impairments. Additionally, the effect of turbulence is evaluated under various turbulence conditions.