MIMO-OFDM systems

This research theme focuses on the empirical and theoretical characterization of wireless fading channels affecting MIMO-OFDM systems, including large-scale and small-scale fading, shadowing, path loss, and Doppler effects. Accurate channel models are essential for link budget calculations, evaluating bit error rates (BER), capacity, and reliability of MIMO-OFDM systems under multipath and mobile environments. Understanding channel behavior helps design robust modulation and coding techniques and informs simulation and prototyping efforts with software tools like MATLAB.

Peak-to-Average Power Ratio (PAPR) is a critical challenge in OFDM and MIMO-OFDM systems that causes nonlinear distortions, reduced power amplifier efficiency, and increased BER. This theme encompasses strategies to reduce PAPR while maintaining or improving BER performance. Techniques studied include hybrid methods combining clipping, selective mapping (SLM), partial transmit sequence (PTS), and filtering. The studies examine trade-offs between complexity, spectral efficiency, and error performance, providing actionable insights into practical MIMO-OFDM system implementations.

Research focused on improving theoretical understanding and practical security of MIMO-OFDM systems explores mathematical modeling based on Hilbert spaces and linear operators to represent the complex signal and channel interactions precisely. Moreover, integration of non-coherent differential modulation and advanced multiple access schemes (NOMA with physical layer security) are studied to optimize capacity, latency, and security for forthcoming wireless standards, including 5G and 6G. These approaches address challenges like channel estimation overhead, pilot contamination, interference management, and eavesdropping risk.