Recently, several detectors based on auxiliary vector (AV) filters are presented to suppress multiaccess interference (MAI) in direct-sequence/code-division-multiple-access (DS-CDMA) systems. Knowing the signature waveform of the desired user, these AV-based detectors are a class of promising candidates for MAI suppression due to their superior performance and low computational complexity. However, it is hard to obtain the desired user's signature waveform, which is the convolution of the user's spreading sequence and the channel impulse response, unless the channel vector is known or unless training signals are sent. In this letter, based on both of the merits of AV detectors and RAKE receivers, an AV-based RAKE-like receiver is proposed for DS-CDMA communication systems in multipath channels. Simulation results indicate that the performance of the new receiver is very close to that of the AV detectors, which know the exact signature waveform of the desired user.

RAKE接收机常被超宽带（UWB）系统用来收集信号的能量和减小信号衰落。本文从缩短信道时延扩展的角度出发，研究RAKE接收机的部分信道均衡能力。本文推导出了RAKE接收机均衡性能与RAKE接收机的复杂度和信道衰减系数之间的关系；分析了信道估计误差对RAKE接收机合并前后多径信道变化的影响。研究表明当存在估计误差时，RAKE接收机仍然能实现缩短信道的作用，但是性能有所下降；由于低复杂度RAKE接收机引入的估计误差较少，在低信噪比条件下其缩短信道性能甚至会优于高复杂度的RAKE接收机。

本文提出一种采用循环前缀和脉冲调制的超宽带无线通信系统（UWB-CP/PM），以及相应的信号处理算法。借鉴采用循环前缀的单载波通信系统（SC-CP）的基本思想，UWB-CP/PM系统通过变换域均衡可以很好地抑制多径干扰。借助脉冲调制，UWB-CP/PM系统可以大大简化收发器件。利用脉冲重复周期大于脉冲宽度的特点，UWB-CP/PM系统不仅可以通过多支路接收和并行处理降低系统对基带处理速度的要求，还可以通过变换域信号处理有效地抑制衰落、多用户干扰和窄带干扰。仿真结果验证了上述性能。

在研究单次频偏累积相偏估计的基础上，本文详细分析了两次独立的频偏累积相偏估计带来的频偏捕获范围的提高。并在此基础上提出一种基于训练序列的载波同步算法。这种算法利用时域两次独立的不同分辨力的相偏估计，解决了单次估计可能存在的相位模糊问题，从而实现了大频偏载波同步。通过理论分析给出了这种算法的性能，并通过仿真进行了验证。由于完全在时域进行估计，和其他大频偏载波同步算法相比，这种算法计算量小，且实现简单

Exploiting the abundant freedom of UWB signals can increase the Euclidean distance among codewords which will lead to an enhancement of the communication quality. In this paper, a coded modulation UWB system combining PPM, PAMand convolutional coding is proposed, which can significantly increase the power efficiency without degrading the data rate. The performance of this coded modulation system primarily depends on the free Euclidean distance and the number of corresponding error bits induced by the error paths. The code generator with maximal minimum free distance and minimum error bits is found to optimize the system. In order to avoid the difficulty of channel estimation and accurate time synchronization in rich multipath environments, a joint multiple symbol detector and decoder for the coded modulation system is presented which is able to approximate the performance of uncoded PPM system in AWGN channel under viable computational burden. Simulation results obtained from Nakagami multipath channel agree with our analysis.