Abstract
An efficient iterative timing recovery via steepest descent of low-density parity-check (LDPC) decoding metrics is presented. In the proposed algorithm, a more accurate symbol timing synchronization is achieved at a low signal-to-noise (SNR) without any pilot symbol by maximizing the sum of the square of all soft metrics in LDPC decoding. The principle of the above-proposed algorithm is analyzed theoretically with the evolution trend of the probability mean of the soft LDPC decoding metrics by the Gaussian approximation. In addition, an efficiently approximate gradient descent algorithm is adopted to obtain excellent timing recovery with rather low complexity and global convergence. Finally, a complete timing recovery is accomplished where the proposed scheme performs fine timing capture, followed by a traditional Mueller–Müller (M&M) timing recovery, which acquires timing track. Using the proposed iterative timing recovery method, the simulation results indicate that the performance of the LDPC coded binary phase shift keying (BPSK) scheme with rather large timing errors is just within 0.1 dB of the ideal code performance at the cost of some rational computation and storage. Therefore, the proposed iterative timing recovery can be efficiently applied on occasions of the weak signal timing synchronization in satellite communications and so on.
Highlights
low-density parity-check (LDPC) codes can approach Shannon’s capacity with moderate decoding complexity at low signal-to-noise rate (SNR) [1,2]
We presented a new iterative timing recovery method using the maximization of the sum of the LDPC decoding metric squares
The relationship between LDPC decoding metrics and timing offsets is analyzed for the purpose of timing recovery
Summary
LDPC codes can approach Shannon’s capacity with moderate decoding complexity at low SNRs [1,2]. The generated information can be applied to assist timing recovery in order to obtain accurate synchronization at very low SNRs. Traditional methods are usually ineffective at low SNRs. Iterative timing recovery uses the metrics from the codewords output of the channel decoding process [3]. A method with LDPC decoding hard decision metrics (i.e., code constraint feedback) to obtain good timing recovery has been proposed in [4]. Turbo-decoding metrics are calculated for obtaining good timing recoveries at low SNRs. turbo code-based methods are highly difficult due to complex turbo decoding. An iterative timing recovery with high precision and low complexity is needed for using in space communications which usually work at low SNRs. In this study, we mainly propose a new iterative timing recovery scheme by using the LDPC decoding metrics to correct timing errors for better timing precision and lower complexity.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
