第三代移动通信中的一种新型AFC算法

在无线移动通信中 ,接收机的本地振荡频率和载波频率之间往往存在较大的频率偏差 ,AFC用于克服此频偏 .传统的AFC采用了模拟环路滤波器 ,因此只能工作在连续的输入信号模式 ,而不能工作于间断导频的W CDMA系统中 .本文对此提出了新的AFC算法 :用最大似然方法估计衰落信道 ,得到间断导频信道的幅度和相位 ,并在一个时隙中进行最大比合并 ,从而得到一个判决变量 .最后用这些变量调节本地振荡频率 ,以跟踪载波频率 .仿真结果显示这种新的AFC算法是可靠而有效的 .

A Novel AFC in the 3rd Generation Mobile Communication System

In wireless communication system, there is a large frequency bias between carrier frequency and local oscillating frequency. AFC is contributed to eliminate it. A traditional AFC adopts analog loop filter that must work consecutively. However, in W CDMA system, the pilot parts are discontinuous. A novel digital approach of AFC is presented. In this algorithm, we first estimate the fading channel to get the phases and amplitudes of the pilot part symbols, and then combine estimations of multiple paths in one slot length, i.e., obtain one decision variable in each slot. Finally, these judged variables adjust the local oscillating frequency to track the carrier frequency by NCO. The simulation results show that the new AFC algorithm is effective and credible.