超宽带系统中基于认知的Rake接收机设计

Design of Rake Receiver for UWB Systems Based on Cognitive Radio

直接序列扩频超宽带(DS-UWB,directed-spread-spectrum ultra wide band)系统采用窄脉冲和扩频技术进行通信,由于带宽很宽,有可能与同频段窄带系统共存。当存在窄带干扰时,最优接收机为采用MMSE准则的Rake接收机,而不存在窄带干扰时,MRC合并算法Rake接收机为最优接收机。由于系统环境是变化的,即窄带干扰并非一直存在,在这种情况下,以上两种接收机都不是最优的。在此基础上结合认知技术提出了一种自适应的Rake接收机抽头选择策略,通过频谱分析得出的判定变量自适应调整Rake接收机抽头权向量。系统仿真实验结果表明,该接收机在系统干扰环境发生变化时,能够得到优于MMSE-Rake接收机和MRC-Rake接收机的性能。

Directed-Spread-Spectrum Ultra Wide Band （DS-UWB） is a technique that may coexistence with other radio systems using very short pulses and spread spectrum. When there is narrow band interfer- ence （NBI）, the optimal receiver is MMSE-Rake receiver, and when there is no NBI, the optimal re- ceiver is Rake receiver with MRC algorithm. With the environment changing, the NBI does not exist all the time. In this case, both above receivers are not optimal. An adaptive finger selection strategy of the Rake receiver with cognitive radio（CR） technique is proposed, and the finger weights vector can be ad- justed by the decision variable obtained from the spectral analysis. The simulation results show that the performance of the system with the proposed receiver is better than the system with MMSE-Rake and MRC-Rake receiver.