Timing Recovery and Carrier Synchronization Using Ldpc Codes: Using Soft Decision Feedback to Aid Timing and Carrier Recovery

This book provides techniques for symbol tracking andcarrier acquisition in a Low-Density Parity-Check(LDPC) coded transmission. In traditional receiverarchitectures, acquisition and tracking are performedusing phase-lock techniques that are independent ofthe channel-code decoding process. In burst receptionscenarios, bandwidth inefficientpiloting must often be embedded in a transmission inorder to accelerate acquisition to aid symbol timetracking at low signal-to-noise ratios. In this bookwe show that outputs from an iterative decoder can beused to improve the estimation of symbol frequencyand phase in either a pilotless environment orcomplementing available pilot information. Wedescribe a method capable of handling very largeoffsets with complexity that grows linearly with themaximum offset size. Combining information from theset of parity-check equations of a LDPC codeobservations with a properlycalibrated phase locked loop allows successfultracking in very high noise scenarios. The problem ofcarrier frequency estimation under these high noiseconditions is also addressed.