Joint LDPC decoding and timing recovery using code constraint feedback

Timing recovery and channel decoding are traditionally performed independently. However, we show here that the information generated during the iterative decoding of low-density parity-check (LDPC) coded data can be fed back to the timing recovery circuit to enable accurate estimation of frequency and phase errors without the need for any pilot symbols. We describe a method capable of handling large offsets with complexity that grows linearly with offset size. Combining the LDPC constraint node observations with a properly calibrated phase locked loop allows successful tracking of a constant time delay, a frequency offset and a random phase walk.