Research On Decoding Algorithm Of Polar Code And Its Applications In ARQ System

Polar Code is the only channel coding scheme that can be theoretically proven to achieve the Shannon limit.Because of its low coding and decoding complexity and outstanding performance,Polar Code has drawn attention of researchers dramatically in the past decade.In 2016,Polar Code has been selected by 3GPP to be the control channel coding scheme for the Enhanced Mobile Broadband(e MBB)scenario in 5G technology.How to improve the performance under finite code length and how to combine Polar code with existing systems are the research hotspots for researchers.Based on this,the contributions and innovations of this thesis are summarized as follows:1.Based on the reliability estimation of polarized channels using Density Evolution-Gaussian Approximation,construct an error-prone bit set in which the bits have high probability to go wrong in successive cancellation(SC)decoding process.Simulation shows that most of the errors that caused only by channel noise can be found in this set.2.Based on the error-prone bit set that mentioned above,a decoding scheme based on the check of error-prone bits is proposed.According to the required code rate,form a one-to-one parity check relationship between some of the error-prone bits and the bits in front of them.In the decoding process,if the parity check fails,decoder can correct the error-prone bits that participating the parity check immediately.Simulation results show that there are 0.3d B to 0.8d B performance gains over cyclic redundancy check aided successive cancellation list(CA-SCL)algorithm using the proposed method under different selections of parity-check information bits.Compared to the other bit flipping scheme,the proposed method can provide at least 0.1d B performance gain under low signal-to-noise ratio.3.Based on the characteristics of generator matrix extension of Polar Code,an auxiliary codeword is constructed.If the first decoding fails,a second decoding attempt will be executed under the help of auxiliary codeword.A segmented decoding scheme is used to decode the auxiliary codeword before the original codeword.Simulation results show that the proposed method have evident performance gains over the traditional SC decoding algorithm.When compared to two different ARQ schemes,the proposed method can obtain up to 1d B and 1.9d B performance gains with different widths of auxiliary window,respectively.4.Employing the proposed segmented decoding scheme in incremental redundancy hybrid automatic repeat request(IR-HARQ)scenario.The auxiliary codeword can be used as redundancy bits to retransmit in multiple decoding attempts until the preset number of retransmissions is reached or the decoding succeed.Simulation shows that the proposed scheme can outperform the other IRHARQ scheme with 0.4d B and 0.6d B performance gains under the first retransmission and the second retransmission respectively.