Channel equalization and symbol detection for single-carrier MIMO systems in the presence of multiple carrier frequency offsets

A new frequency-domain channel equalization and symbol detection scheme is proposed for multiple-inputmultiple-output (MIMO) single-carrier broadband wireless systems in the presence of severely frequency-selective channel fading and multiple unknown carrier-frequency offsets (CFOs). Multiple CFOs cause severe phase distortion in the equalized data for large block lengths and/or constellation sizes, thus yielding poor detection performance. Instead of explicitly estimating the CFOs and then compensating them, the proposed scheme estimates the rotated phases (not frequencies) caused by multiple unknown CFOs and then removes the phase rotations from the equalized data before symbol detection. The estimation accuracy of the phase rotation is improved by utilizing a groupwise method rather than symbol-by-symbol methods. This paper differs from other related work in orthogonal frequency division multiplexing (OFDM) studies in that it can combat multiple CFOs that are time varying within each block. Numerical examples for 4 × 2 and 8 × 4 single-carrier systems with quaternary phase-shift keying (QPSK) and eight-phase-shift keying (8PSK) modulation illustrate the effectiveness of the proposed scheme in terms of scatter plots of constellation, mean square error (MSE), and bit error rate (BER).