The model of the MIMO-OFDM system in doubly-selective channels is derived and a lower bound of mean squared error(MSE) of the channel estimator using frequency domain pilot is presented.

基于双衰信道的频域响应，提出了一类双衰信道下多天线正交频分复用（MIMO-OFDM）系统的最优化频域导频设计方案。

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Second, channel estimation algorithms of two-hop OFDM cooperative communication system with single relay are discussed, which are mainly based on block pilot.

其次，讨论了两跳单中继多载波协同通信系统的信道估计的问题，主要是基于辅助块状导频的方法；

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The scheme USES pilot symbols to estimate the channel and improves the bit error performance of the system.

该方案使用的导频符号来估计信道，并提高了系统的误码性能。

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