BICM-OFDM系统中基于叠加导频的迭代信道估计

Iterative channel estimation based on superimposed pilot for BICM-OFDM

传统叠加导频算法应用在正交频分复用系统中存在信道估计精度差的缺点。针对比特交织编码调制(BICM)联合正交频分复用(OFDM)的系统(BICM-OFDM),提出一种利用叠加导频的迭代信道估计算法。该算法充分利用了均衡器的反馈信息,分两步进行。首先,导频信号叠加在发送信号上,接收端采用一阶统计量进行初始信道估计;然后利用均衡器的硬判决反馈信息,在信道估计与均衡之间进行信息交换,通过迭代的方式提高信道估计精度。在短波宽带信道下的仿真结果表明,与传统叠加导频算法相比,新算法经过二次迭代可有效提高信道估计精度和系统误码率性能。

The conventional superimposed pilot applied in OFDM system has drawback of bad accuracy. According to the system of combination of orthogonal frequency division multiplexing （OFDM） and bitinterleaved coded modulation （ BICM）, an iterative channel estimation algorithm based on superimposed pilot is proposed. This algorithm makes full use of the feedback information provided by equalizer, and has two steps. Firstly, pilots are added to the transmitted signals. The initial estimation employs the first-order statistic. Using the hard-decision feedback information provided by the equalizer , the information between the channel estimator and the equalizer could be exchange. The precision could be improved iteratively by the feedback information that provided by iterative decoder of BICM. Through the wideband HF channel, the simulation results show that, compared with conventional superimposed pilot algorithm, the proposed algorithm efficiently improves the channel estimation accuracy and BER performance after two iterations.