Research On Constructing Non-binary LDPC Codes To Suppress OFDM Peak-to-average Ratio

As the core technology for high-speed data transmission in wireless communications,orthogonal frequency division multiplexing(OFDM)technology has many advantages such as strong multipath interference resistance and high spectrum utilization.However,the OFDM system has the characteristic of peak-to-average power ratio,and the high-peak transmission signal is prone to non-linear distortion when passing through the power amplifier,resulting in out-of-band spectrum leakage and in-band signal distortion.The invertible subset low density parity-check(IS-LDPC)codes constructed by the random construction method can significantly reduce the PAPR of the OFDM system while having good error-correcting performance.It is a kind of great potential PAPR reduction method.However,the IS-LDPC code is type of LDPC code over (2),compared with it,the LDPC code over high-order finite fields usually has stronger error-correcting capabilities and resistance to burst errors,and is easily combined with high-order modulation schemes to obtain higher transmission rates.Therefore,the focus of this article is to introduce the concept of invertible subsets into non-binary low density parity-check(NB-LDPC)codes,and construct new NB-LDPC codes to suppress PAPR.First of all,this paper describes the basic idea,advantages and disadvantages of OFDM technology,shows the significance of reducing PAPR for OFDM system.Then it briefly introduces the methods proposed to reduce PAPR of OFDM systems at this stage,and clarifies the potential of IS-LDPC codes to reduce PAPR and the advantages of NB-LDPC codes.Secondly,this paper extends the IS-LDPC code from (2)to (),applies the concept of invertible subsets to NB-LDPC code,and proposes a new type of NB-LDPC code,which called IS-NB-LDPC code.After theoretically proving the properties of the check matrix of the IS-NB-LDPC code and its Tanner graph,we take this as a basis to propose an invertible subset progressive edge-growth like(IS-PEG-Like)algorithm to construct the check matrix of IS-NB-LDPC codes,and some precautions of this algorithm are briefly explained.In addition,since the IS-NB-LDPC codes are a kind of LDPC codes over high-order finite fields,the value of its label symbols and the realization of the inversion operation are different from the IS-LDPC codes.This paper analyzes this in detail.Finally,this paper applies IS-NB-LDPC codes to OFDM systems to reduce the PAPR of OFDM systems.Simulations show that it inherits some of the advantages of IS-LDPC codes and NB-LDPC codes,such as the ability to significantly reduce the PAPR of the OFDM system with lower search complexity,and it is suitable for combining with highorder modulation schemes,etc.