频分双工智能天线系统中的一种空时预RAKE算法

Space-Time Pre-RAKE Algorithm for Frequency Division Duplex Smart Antenna Systems

针对频分双工的智能天线系统中因上下行频率差异对下行波束形成所带来的问题,提出了一种基于多约束最小方差无畸变响应(MVDR)波束形成和频率转换的空时预RAKE算法.利用信道估计方法得到方向和时延信息,通过多约束MVDR准则求得同频率下的空时预RAKE权矢量,利用最小二乘法求得频率转换矩阵,再对该预RAKE权矢量进行上下行频率转换,以完成下行预RAKE发射.该方法与传统的基于波达方向(DOA)估计的预RAKE相比,直接利用了上行接收的阵列响应协方差阵,无需DOA估计,在不增加额外运算量的情况下,解决了传统方法在多径环境中抑制干扰能力差的问题.仿真实验结果表明,在多用户和多径环境下,能有效地提高下行接收信噪比,降低多址干扰.

In the smart antenna system, the uplink channel responses and covariance matrix are important for downlink spacetime preRAKE. When different radio frequency between uplink and downlink is chosen in smart antenna system with frequency division duplex, the uplink channel responses and covariance matrix can not be applied directly to the downlink. Therefore, in tradition, it was considered that the downlink preRAKE could only be implemented via directionofarrival (DOA) estimation, which can not efficiently suppress the Multiple Access Interference and achieve antenna gain. To solve this problem, a novel spacetime preRAKE algorithm without DOA estimation is presented. Through multirestrain minimum variance distortionless response (MVDR) method, the spacetime preRAKE in the uplink frequency is obtained, and then translated into the downlink with the aid of frequency translation matrix. In this algorithm, the uplink channel responses and covariance matrix can be used directly in downlink without the increase of complexity. Numerical simulations show that the proposed algorithm can efficiently improve the receiver's SNR of downlink.