Blind equalization in SIMO OFDM systems with frequency domain spreading

The problem of bandwidth efficient data transmission in multiple antenna orthogonal frequency division multiplex (OFDM) systems is considered. Contrary to the mono-sensor systems, the effects of frequency-selective fading may be compensated in the multiple antenna systems due to the space diversity without using a wireless overhead. A modulation scheme that improves the reliability of data transmission in fading multipath environments and performs an accurate channel equalization with no excess bandwidth neither substantial training is proposed. The new scheme exploits a frequency domain spreading along with the standard OFDM modulation. This modulation yields an improved error rate; its structure is also exploited to estimate the equalizer. The problem of reliable channel equalization in such systems is shown to be essentially different in single and multiple antenna scenarios. For the multiple antenna scenario, a new approach to robust equalization is proposed, and its performance is analyzed. The numerical study confirms the efficiency of the new method in such bandwidth-expensive applications as wireless networks.