Superimposed training for conventional and code-aided timing recovery in turbo-coded systems

Initial timing error estimation is a critical issue for the convergence of iterative code-aided (CA) timing recovery algorithms in turbo-coded systems, especially at the low signal-to-noise ratio scenarios that turbo codes are designed to work. The proposed solutions in the literature involve additional frame synchronization processing or sending a short synchronization sequence. In this paper, the use of superimposed training (ST) to initialize iterative code-aided timing recovery algorithms in turbo code systems is proposed. Simulation results show that timing recovery based on ST can achieve a performance close to that of perfect synchronization for both CA and conventional timing recovery schemes. Furthermore, ST used for timing recovery can also be exploited for frame synchronization.