Abstract: In the Ultra-Wide-Band（UWB） wireless communication systems，the receiving structure is usually based on RAKE receiver.The channel estimation is essential to the accuracy of RAKE receiver.In this paper，a gradient-based variable step size LMS algorithm is proposed to track time-varying channels.Compared with the typical LMS algorithm，this improved LMS algorithm produces much smaller MSE and hence provides better channel estimation.The results also show that the LMS algorithm helps improve the performance of RAKE receiver and gets smaller bit error rate.

Key words: Timing Hopping Ultra Wide Band（TH-UWB）, rake receiver, Least Mean Square（LMS） algorithm, simulation

摘要： 跳时超宽带（TH-UWB）无线通信系统通常采用RAKE接收技术。而信道估计的准确度直接影响系统接收性能。提出一种基于梯度的变步长的LMS算法进行信道估计。与传统LMS算法相比，改进的LMS算法可以获得更小的MSE（Mean Square Error）从而为接收机提供更精确的信道估计量。同时，结果也表明该算法提高了整个接收机性能，并获得更小的BER（Bit Error Rate）。

关键词: 跳时超宽带（TH-UWB）, Rake接收机, 最小均方（LMS）算法, 仿真