【作者】 董俊花；

【导师】 李一兵；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2009， 硕士

【摘要】 近年来,脉冲超宽带(IR-UWB)由于具有传输速率高、系统容量大、抗多径能力强等优点,受到了各研究机构和标准化组织的广泛关注。但是由密集多径信道产生的信号能量扩展造成的多径干扰,使信号产生严重的失真和波形展宽并导致信息波形重叠,将会引起躁声增强和误码率上升,制约了超宽带无线通信系统的性能。本文从多径干扰给超宽带无线通信系统带来的影响出发,在研究IEEE802.15.3a推荐的修正S-V信道模型的基础上,就直扩超宽带(DS-UWB)系统的多径干扰问题进行了深入全面的研究。首先,从时域均衡角度研究了抗多径干扰技术,提出了一种基于自适应步长LMS算法的DFE/RAKE接收机。该接收机的结构不依赖于传统RAKE接收机增加分支数目的方法来提高系统性能,而是利用均衡技术,在消除ISI的同时也降低了RAKE接收机的分支数目,从而降低了系统复杂度。仿真结果表明该算法能有效抑制多径干扰,改善误码率性能,降低系统复杂度。然后,从改进RAKE接收机算法和降低复杂度的角度研究了抗多径干扰技术。通过研究存在多径干扰时的直扩超宽带系统的信号模型,提出了一种基于改进Kalman滤波算法的RAKE(MKFA-RAKE)接收机。该算法在考虑系统参数时变的情况下,首先利用Kalman滤波算法对各路径信号去相关,然后对各路径信号进行最大比合并。理论推导和仿真结果表明,该接收机有更好的输出信干比和误码率性能,且算法收敛速度快,复杂度低,有较强的抗多径干扰能力。更多还原

【Abstract】 In recent years, Impulse Radio Ultra-wideband (IR-UWB) technology has attracted more and more attention in research institutions and standardization communities, due to its high data rate, large capacity, strong anti-multipath ability and so on. However, the serious distortion of the signal and the waveform broadening caused by multipath interference will lead to the overlapped information profile, which will bring about noise enhancement and the bit error rate rising, and affect the performance of UWB system severely.In this paper, starting from the impacts caused by multipath interferences, based on the modified S-V channel model of IEEE 802.15.3a recommendation, we done some deep and full studies for multipath interferences of direct sequence Ultra-wideband(DS-UWB)system.First, a kind of DFE/RAKE receiver based on adapted step LMS algorithm is put forward by studying the anti-multipath interferences technology from the perspective of time domain equalization. This receiver’s structure does not rely on the traditional RAKE receiver which use the increasing number of the branch to enhance the system performance, instead to use equalization technology which eliminated ISI also reduced the system complexity by reducing the RAKE receiver’s branch number. The simulation results show that this algorithm has suppressed the multipath interferences effectively, improved the bit error rate performance, and reduced the system complexity.Then, a kind of RAKE receiver based on modified Kalman filtering algorithm (MKFA-RAKE)is put forward by studying the signal model of direct sequence Ultra-wideband system with multipath interferences, meanwhile the anti-multipath interferences technology is studied from the perspective of modified the RAKE receiver algorithm and reduced the complexity. By consideration of system parameters time-variable character, this algorithm uses the Kalman filtering algorithm to decor-relate the signals of each path, and then carries the Maximal Ratio Combining on signals of each path. Theoretical derivation and the simulation results show that this receiver has the better output signal to interference ratio and the bit error performance, and has the quick algorithm convergence rate, the low complexity and the strong ability of anti-multipath interferences.更多还原