【摘要】 Ｒａｋｅ接收机是ＣＤＭＡ系统中实现多径分集接收的核心部件，而信道估计对其接收性能有很大影响。传统连续导频符号的信道估计是采用对固定区间的信道参数估计值进行平均的方法以抑制接收噪声。但这样必然带来的问题是，如果平均长度过小，则不能达到最大限度地抑制噪声的目的，如果平均长度过大，则又更多地引入了由于多普勒频移所造成的估计误差。因此信道估计的长度必然存在一个与接收噪声及最大多普勒频移有关的一个平衡点。本文提出了直接利用搜索单元得出的最强径所估计出的每个导频符号瞬时信道参数的包络估计最大多普勒频移，并应用于自适应调节信道符号估计长度的方法。仿真表明本方法随着信噪比的增加，能够达到对移动速度的较准确估计。它不仅能够应用于信道估计中，也可应用于自适应调节快速功控步长及小区切换中，具有较高的实用性。更多还原

【Abstract】 In this paper, the estimation of maximum Doppler frequency of fading channels will be investigated. In Rake receiver of direct-sequence code division multiple access (DS-CDMA) systems, channel estimation is carried out via a pilot channel (symbols), which is transmitted simultaneously to the data channel (symbols). In the channel estimation, an averaging process is involved, which for long averaging period suppresses the noise influence efficiently. On the other hand, long averaging intervals lead to systematic errors in the estimated channel coefficients due to the time-variant behavior of the channel and this error is closely related to the maximum Doppler frequency f_d. Taking into account these effects, a novel estimation method of f_d is presented which uses the instantaneous channel coefficients of the pilot symbols of the strongest finger in Rake receiver. This helps to adaptively optimize the averaging period and as a result the BER performance of the receiver could be improved.更多还原