Optimal BER in MIMO Raleigh Fading Channel from QPSK Modulation: Modified MMSE Versus ML Equalizer Evaluation |
Sabuj Sarkar and Mohammad Shaifur Rahman
This paper proposes an exclusive equalizer alternative to existing optimum maximum likelihood (ML) equalizer that reduces bit error rate (BER) via spatial multiplexing, diversity combining and splits up each user's multiple input multiple output (MIMO) channel into parallel sub-channels. Quadrature phase shift keying (QPSK) modulation is treated here for the simulation purpose. The new equalizer is the modified version of minimum mean square error (MMSE) equalizer termed as Modified MMSE that incorporates channel equalization and noise addition with successive interference cancellation by means of modified matrix order. The process is same as SIC-Sort equalizer but matrix is modified by ordered optimum power of the transmitted symbol. Rayleigh fading channel is used in the simulation as it enables the computation of the expected complexity up to the linear term in the exponent. Simulations are done by MATLAB that shows BER vs. signal-noise ratio (SNR) curve of Modified MMSE equalizer exceeds that of ML equalizer.
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