可加白高斯信道上软判决序贯译码的码元度量的估计

其中,n(t)为高斯白噪声,具有均值 E_n(t)=0和自相关函数 E_n(s)n(t)=(N_0)/2δ(t—s);N_0称为噪声 n(t)的单边功率谱密度,δ(τ)称为δ函数或单位脉冲函数.r_i(t)通过相干解调后得

ESTIMATING THE CODE SYMBOL METRIC FOR SOFT DECISION SEQUENTIAL DECODING ON AN ADDITIVE WHITE GAUSSIAN NOISE(AWGN)CHANNEL

In practical communications,the metric used for soft decision sequential decoding oftenmismatches with the practial channel.A simple method to remedy this disadvantage is to useautomatic gain control,which however implies an assumption that the signal to noise ratio ofthe practical channel does not offset from the designed value.In order to elimate that assump-tion,this paper proposes a new scheme which is based on estimating the metric with the recei-ved data.Two methods for accurately estimating the metric for AWGN channel are given.