非周期扩频的同步CDMA系统下行信道的分数阶间隔信道估计
Fractionally Spaced Channel Estimation for Synchronous DS-CDMA Downlink with Aperiodic Spreading Code
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摘要: 使用正交扩频码的同步CDMA系统具有对抗同信道干扰的能力，但是多径传播导致信号失去正交性，互相关值增加。在这些情况下，需要对信道进行估计以提高接收机检测性能。以往的基于子空间的CDMA信道估计算法都是在chip速率采样的基础上得到的，其条件是接收信号满足Nyquist定理且信道是最小相位系统，这些条件在实际情况中是很难满足的。该文提出一种应用于非周期扩频的同步CDMA系统的下行信道的分数阶间隔信道估计的算法。计算机仿真表明了算法是有效的。Abstract: Synchronous Code-Division Multiple-Access (CDMA) techniques possess intrinsic protection against co-channel interference when orthogonal codes are used. However, in the presence of multipath propagation, the signals lose their orthogonality property, leading to increased cross correlation. In these cases, channel estimation may be needed in order to improve detection. The former algorithms for estimating the channel response of CDMA system are used for signal sampled with chip rate. The received signal sampled in chip rate does not satisfy the Nyquist theory and the channel may be not a minimumphase system that the former algorithms do not work. An algorithm for fractionally spaced channel estimation of a synchronous CDMA system is proposed that uses aperiodic spreading code. Simulations demonstrate the performance of proposed algorithm.
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