Constrained Turbo Decoding with Bit Based Early Detection

In this paper, we propose a symbol based early detection method and a constrained turbo decoding algorithm to reduce the turbo decoding complexity, but without performance degradation. By incorporating a trend watch on the extrinsic values of individual bits with a threshold detection, some correctly decoded bits can be observed early. This information is further exploited to constrain the decoding along the trellis so that the decoding of other bits can be improved with reduced complexity. Simulation demonstrates the promising performance of this algorithm. An interesting result is that the trend watch plays a more important role in determining those early decoded bits. Therefore, the complexity in determining the optimal thresholds can be avoided and the load of detection process is very small