Blind Frame Synchronization For LDPC Codes

Blind frame synchronization can effectively reduce the pilot and training overhead,as well as save spectrum resources,hence it may be an efficient signal processing technology for the future resource limited wireless communication.However,the lack of pilot and training sequence in blind frame synchronization results in the loss of bit error rate(BER)performance.Low-density parity-check code(LDPC),a channel coding scheme that has been adopted by the 5th Generation mobile communication(5G),has an excellent error correction performance and it is capable of improving the BER performance of blind frame synchronization by using the redundant information in the code-word.Specifically,there are mainly two LDPC categories: random LDPC and QC-LDPC(Quasi-cyclic Low-density Parity-Check Codes).Random LDPC exhibits a good error-correcting performance with a high storage complexity,while QC-LDPC has the characteristics of stable structure and simple hardware implementation.In this paper,both the random LDPC and QC-LDPC based blind frame synchronization schemes have been studied to explore a blind frame synchronization scheme with low complexity and reliable transmission performance.In order to effectively balance a trade-off between the performance and complexity of blind frame synchronization,this paper proposed a low-complexity LDPC based blind frame synchronization algorithm in chapter 3.To be more specific,a concept of “decoding while synchronizing” is utilized to reduce the high complexity imposed by the traditional iterative decoding.Simulation results are shown that the proposed scheme is capable of effectively reducing the complexity of traditional decoding schemes with a comparable performance.In order to further measure whether a given LDPC is suitable for blind frame synchronization or not,a function based effective measurement mechanism is developed in chapter 4.Specifically,the measurement function which is only related to the check matrix and the delay to be estimated is derived.It is helpful to portray the relationship between the measurement function and time delay.By observing the peak of the curve on check matrix,it is useful to determine whether the given code is suitable for blind frame synchronization or not.Simulation results are shown that the proposed measurement mechanism is efficient for the LDPC selection in blind frame synchronization.For the sake of improving the performance of QC-LDPC based blind frame synchronization,its performance is further investigated in chapter 5.Based on the quasi-cyclic characteristics of the QC-LDPC,a concept of "matrix similarity" is conveyed in this paper.By utilizing the measurement function proposed in chapter 4 and theoretical analysis,it is revealed that the performance of the random LDPC based blind frame synchronization exhibits better than that of QC-LDPC based counterpart,which provides a theoretical basis for future LDPC based blind frame synchronization design.