J.M. Walsh, C.R. Johnson, Jr., and P. Regalia
This paper investigates turbo methods for joint synchronization and decoding in pulse amplitude modulated (PAM) systems. We begin with a brief review of the turbo principle before applying it to the synchronization problem. Specifically, we propose and investigate a baud timing offset synchronization algorithm for error control coded systems. Un-like many previously proposed algorithms, which feed estimates for the coded symbols to the decoder, our algorithm calculates and exchanges extrinsic information values for the coded bits, as is consistent with the turbo principle. Simulations prove the algorithm s utility and verify that it has performance near to that of an ideal synchronizer achieving the Cramer Rao lower bound on timing error estimation variance. We investigate both systems employing regular convolutional error correcting codes as well as serially concatenated convolutional turbo codes.