MIMO-OFDM for wireless communications: signal detection with enhanced channel estimation

TLDR

MIMO channels increase capacity proportional to the minimum number of transmit and receive antennas. The paper investigates MIMO‑OFDM for wideband transmission to mitigate intersymbol interference and boost capacity. The system employs two independent space‑time codes across two sets of two transmit antennas, with receiver decoding via prewhitening and successive interference cancellation using minimum‑Euclidean‑distance decoding. Simulations show that a 4×4 MIMO‑OFDM system needs 10.5 dB (10% WER) and 13.8 dB (1% WER) at 4 Mb/s over 1.25 MHz, while doubling the receive antennas to eight cuts these to 4 dB and 6 dB, demonstrating MIMO‑OFDM’s potential for highly spectrally efficient wideband transmission.

Abstract

Multiple transmit and receive antennas can be used to form multiple-input multiple-output (MIMO) channels to increase the capacity by a factor of the minimum number of transmit and receive antennas. In this paper, orthogonal frequency division multiplexing (OFDM) for MIMO channels (MIMO-OFDM) is considered for wideband transmission to mitigate intersymbol interference and enhance system capacity. The MIMO-OFDM system uses two independent space-time codes for two sets of two transmit antennas. At the receiver, the independent space-time codes are decoded using prewhitening, followed by minimum-Euclidean-distance decoding based on successive interference cancellation. Computer simulation shows that for four-input and four-output systems transmitting data at 4 Mb/s over a 1.25 MHz channel, the required signal-to-noise ratios (SNRs) for 10% and 1% word error rates (WER) are 10.5 dB and 13.8 dB, respectively, when each codeword contains 500 information bits and the channel's Doppler frequency is 40 Hz (corresponding normalized frequency: 0.9%). Increasing the number of the receive antennas improves the system performance. When the number or receive antennas is increased from four to eight, the required SNRs for 10% and 1% WER are reduced to 4 dB and 6 dB, respectively. Therefore, MIMO-OFDM is a promising technique for highly spectrally efficient wideband transmission.