WCDMA中变步长功率控制过程

An Adaptive Step-Size Power Control Scheme in WCDMA

本文提出了一种可应用于WCDMA中的变步长功率控制策略 ,这种功控策略根据TPC命令的“历史” ,将功率控制过程划分为Markov状态 ,分析信道衰落步长的概率密度 ,每一状态对应一个确定的步长值 ,从而可以确定功率控制步长集中的步长数 ,我们选用概率密度最大的数值 ,同时考虑硬件可以分辨的最小步长在 0 .5dB左右 ,确定步长集 .再用仿真的方法 ,确定状态和步长的对应关系 .发射机依据当前的TPC命令决定应该增大还是减小发射功率 ,依据当前TPC命令和“历史”上的TPC命令选择合适的功率步长 。

In the wideband code division multiple access (WCDMA) system,fast transmit power control (TPC) should overcome the pathloss caused by fast multipath fading.However,the conventional fixed step size transmit power control (FS TPC) does not compensate the fading well due to the complexity of fast fading in Rayleigh channel.We propose and evaluate a single bit adaptive step size transmit power control (AS TPC) scheme which can be applied in WCDMA.The new scheme divides the power control process into Markov states according to the received TPC command in 'history'.On the basis of analysis of the step size of the channel fading,it chooses step size according to the largest probability density of step size of the multipath Rayleigh fading channel with respect to the period of the transmit power control.Each TPC step size is corresponding to a channel Markov states.Considering the power circuit′s minimum resolving is about 0 5dB,we can decide the step size set.In this paper,the relationship between the Markov state and the TPC step size is made out by computer simulation.The transmitter decides increasing or decreasing the transmit power according to the received TPC command.However,the changing quantity is chosen according to the current TPC command and the historical TPC commands.