A frequency domain pre-equalizer for MIMO-OFDM mobile communication systems employing alamouti coding

Orthogonal frequency division multiplexing (OFDM) is a very popular modulation scheme because it requires a very simple receiver in transforming a frequency-selective channel into multiple flat-fading channels. Furthermore, multiple-input-multiple-output (MIMO) OFDM systems employing transmit diversity techniques, such as space-time (ST) and space-frequency (SF) coding, increase robustness and reliability over wireless fading channels. However, time-variation of the channel due to mobility disrupts orthogonality among subcarriers and yields intercarrier interference (ICI), limiting the performance of OFDM. In this paper we first recall a reduced-complexity technique to mitigate ICI in single-input-single-output (SISO) OFDM systems denoted per sub-block equalization (PSE) which operates on sub-blocks of the received OFDM symbol. Next we propose an extension of PSE to MIMO SF-OFDM systems. In particular, the Alamouti scheme is used in conjunction with PSE to combat ICI. Performance of the proposed scheme is evaluated for mobile digital video broadcasting DVB-T2 2 × 1 and 2 × 2 MIMO scenarios that suit with a possible extension to handheld devices in a next generation DVB-H. Numerical results show that the new receiver provides a gain from 21% to 33% with respect to the conventional OFDM receiver in terms of vehicular speed at which a target bit error rate can be maintained.