Low-complexity BEM-based Channel Equalization for Transmit Diversity MISO OFDM Systems over Doubly Selective Channels

In highly mobile scenarios, Wireless channels tend to experience both time selective and frequency selective fading, namely so-called rapidly time-varying channels, also called doubly selective fading channels. The initial transmit diversity Alamouti coding scheme was proposed to be applied in time-invariant flat channels, and is unable to directly extend to rapidly time-varying channels. Additionally, the inter-carrier interference (ICI) in OFDM systems should not be neglected due to high mobility. Therefore, it is challenging to economically implement the effective signal recovery for transmit diversity MISO OFDM systems over doubly selective channels. Based on the basis expansion model (BEM) representation of doubly selective channels, an effective hybrid interference cancellation (HIC) with dynamic group channel equalization algorithm is investigated. Simulation results demonstrate that the proposed scheme exhibits significant performance enhancement while its computational complexity dramatically degrades compared with traditional MMSE equalization which implies reduced energy consumption, achieving the goal of energy saving. In comparison with the existing equalization methods regarding transmit diversity, the proposed technique can achieve better tradeoff between performance and complexity. Furthermore, under the hypotheses of perfect channel state information, its BER performance yields no loss with the increase of mobile speed.