在時變衰減通道下之結合通道估測與信號偵測演算法和低密度同位元檢查碼解碼之遞迴系統的編碼設計

Abstract

在雷利衰減通道下，此研究利用結合通道估測與信號偵測演算法和低密度同位元檢查碼解碼之遞迴系統來幫助我們在沒有任何領航信號和訓練信號的情況下作解碼。然而在衰減通道下，低密度同位元檢查碼之變數節點間的相互關係會依據其通道衰減速度緩慢遞減。為了達成低密度同位元檢查碼的無迴圈條件，其變數節點間的獨立假設是必須的。因此在本研究中，所有連接至相同檢查節點的變數節點必須限制在不同的同調區間來達成上述獨立假設。而有限長度的低密度同位元檢查碼其效能會受到其所經歷的同調區間個數和衰減速度的影響。

Without using any pilot and training symbols, a serially concatenated turbo transceiver is proposed for joint channel estimation, symbol detection and LDPC decoding in Rayleigh fading channels. In fading channels, the dependence of variable nodes in the factor graph lingers slightly according to the fading speeds. However the independence assumption is necessary for the cycle-free condition of LDPC codes. Hence we added the design criterion that the variable nodes connected to the same check node are restricted to be in different coherence intervals to meet the constraint. The performance of finite-length LDPC codes would be affected both by the number of coherence intervals and the fading speed.