Performance improvement of MIMOOFDM communication systems based on non-linear equalization

Abstract

This paper introduces a nonlinear equalizer for Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems based on Discrete Wavelet Transform (DWT). It is referred to as the Joint Non-Linear Combining Zero Forcing-Successive Interference Cancellation (JNLCZF-SIC) equalizer. Unlike traditional equalizers, the JNLCZF-SIC equalizer performs both equalization and Carrier Frequency Offset (CFO) correction simultaneously. The main advantage of the proposed JNLCZF-SIC equalizer over existing methods is its ability to reduce simulation times without compromising performance by minimizing the number of arithmetic operations required. To assess its effectiveness, we evaluate its Bit-Error-Rate (BER) and computational load against standard equalization techniques such as Linear Zero-Forcing (LZF), Linear Minimum Mean Squared Error (LMMSE), and MMSE-Successive Interference Cancellation (MMSE-SIC) equalizers. Simulation results reveal that the JNLCZF-SIC equalizer not only achieves a lower BER but also significantly decreases computational complexity. This improvement in simulation time is particularly beneficial for large-scale MIMO systems, where DWT is employed to accelerate processing by breaking down the signal into multiple frequency bands, optimizing the equalization process. The equalizer's ability to simultaneously handle equalization and CFO compensation with reduced computational demands makes it highly suitable for real-time applications and large-scale implementations. Additionally, a closed-form expression for the count of arithmetic operations for the proposed equalizer in a general 2^σ × 2^σ MIMO configuration is provided.