Design and RTL-Level FPGA Realization of a MIMO-GFDM Digital Baseband Modem for Underwater Optical Wireless Communication

Underwater Wireless Communication (UWC) has emerged as an important enabling technology for applications including ocean observation, offshore monitoring, underwater sensor networks, assisted navigation, and Internet of Underwater Things (IoUTs). Among the available communication techniques, Underwater Optical Wireless Communication (UOWC) offers high data rates, low transmission latency, and improved bandwidth utilization for short- to medium-range communication scenarios. However, underwater optical channels remain affected by attenuation, scattering, and signal degradation, requiring bandwidth efficient transmission techniques. This paper presents the design and RTL-level FPGA realization of a Multiple-Input Multiple-Output Generalized Frequency Division Multiplexing (MIMO-GFDM) digital baseband modem for underwater optical wireless communication. The proposed architecture combines GFDM-based multicarrier transmission with MIMO processing to support flexible time–frequency allocation and reduced interference effects in underwater communication environments. The complete modem architecture is developed and evaluated using MATLAB/Simulink under simulated underwater channel conditions. To demonstrate implementation feasibility, the designed communication blocks are translated into synthesizable VHDL through an HDL-based workflow and analysed through RTL-level realization for FPGA-oriented implementation. Simulation outputs including transmitted and received signal behaviour, error characteristics, spectral response, and implementation resource observations are presented for performance assessment. The obtained results indicate that the proposed architecture provides an effective framework for investigating spectrally efficient underwater optical communication systems and demonstrates the feasibility of RTL-level realization for future hardware deployment.