A low variance timing recovery in turbo receivers

Abstract

This paper presents a fast converging timing recovery algorithm for digital receivers in low signal to noise ratio. This solves the problem of traditional slow converging phase-locked loop-based timing recovery in low noise environments. In this proposal, the receiver exploits the soft decisions computed at each turbo decoding iteration to provide reliable estimates of soft timing signal which in turn improves the decoding time. The proposed alternative tends convergence in about 10 iterations and derived sequential minimization technique approaches a theoretical Cramer-Rao bound with unbiased estimates. The proposed scheme is adaptive to any modulation and is insensitive to carrier offsets apparent in receivers. We have shown through simulation that the proposed method outperforms conventional timing extraction methods with respect to jitter performance. We therefore note that this timing synchronization method is suited to cellular communication receivers, where delay variation is intolerable.