Adaptive Frequency-Domain Channel Estimator in 4 x 4 MIMO-OFDM Modems

Abstract

This work presents an adaptive frequency-domain channel estimator (FD-CE) for equalization of space-time block code multiple-input multiple-output ( MIMO) orthogonal frequency-division multiplexing (OFDM) systems in time-varying frequency-selective fading. The proposed adaptive FD-CE ensures the channel estimation accuracy in each set of four MIMO-OFDM symbols. Performance evaluation shows that the proposed method achieved a 10% packet error rate of 64 quadrature amplitude modulation (QAM) at 29.5 dB SNR under 120 km/h ( Doppler shift is 266 Hz) in 4 4 MIMO-OFDM systems. To decrease complexity, the rich feature of Alamouti-like matrix is exploited to derive an efficient very large-scale integration (VLSI) solution. Finally, this adaptive FD-CE using an in-house 0.13-m CMOS library occupies an area of 3 X 3.1 mm(2), and the 4 X 4 MIMO-OFDM modem consumes about 62.8 mW at 1.2 V supply voltage.