说明：  在基于脉冲的UWB系统中，采用瑞克接收机合并多径信号能量并进行相干检测，信道估计问题即估计多径信号的到达时间和幅度。在基于OFDM的UWB系统中，接收机根据信道频域响应对每个子信道进行频域均衡后进行相干检测，信道估计问题即估计信道频域响应。
(Pulse-based UWB systems, rake receivers using the combined multipath signal energy and coherent detection, channel estimation problem that is estimated multipath signal arrival time and amplitude. OFDM-based UWB system, the receiver under the channel frequency response of each subchannel to frequency domain equalization after coherent detection, channel estimation problem that is estimated channel frequency response.)