双选择性信道下发射分集MISO OFDM系统基于BEM的低复杂度信道均衡

在高速移动环境下，无线信道会同时经历时间选择性和频率选择性衰落，即所谓的快速时变信道，也称之为双选择性信道。最初的发射分集Alamouti编码方案是针对时不变平坦信道提出的，不能直接应用于快速时变信道。此外，OFDM 系统在双选信道下遭受的载波间干扰(ICI)不可忽视。因此，发射分集MISO OFDM系统在双选择性信道下既节能又有效的信号恢复是有挑战的。本文基于双选择性信道的基扩展模型(BEM)表示，研究了一种有效的可动态分组的混合干扰消除(HIC)信道均衡方案。仿真结果表明，提出的方案，与传统的MMSE均衡相比，计算复杂度大大降低的同时性能显著提高，计算量的降低减少了能量消耗，达到节能的目的；与现有的关于发射分集的信道均衡方案相比，表现出性能和复杂度的较好折中；此外，在信道信息完美已知的假设下，随着移动速度的提高，误码性能没有损失。 

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.