Adaptive iterative detection for phase tracking in turbo-coded systems

The problem of performing iterative detection (ID)—a technique originally introduced for the decoding of turbo codes—for systems having parametric uncertainty has received relatively little attention in the open literature. In this paper, the problem of adaptive ID (AID) for serial and parallel concatenated convolutional codes (SCCC’s and PCCC’s or turbo codes) in the presence of carrier-phase uncertainty is examined. Based on the theoretical framework in [1], [2], adaptive soft inverse (ASI) algorithms are developed for two commonly used blocks in turbo codes, leading to the adaptive soft-input soft-output (A-SISO) and the adaptive soft demodulator (A-SODEM) algorithms. Based on these algorithms, practical AID receivers are presented. Several design options are proposed and compared and the impact of parametric uncertainty on previously established results for iterative detection with perfect channel state information (CSI) is assessed.