The Research And Design Of Polar Decoder Based On FO-BP Algorithm

Polar codes are error-correcting codes that can provably achieve channel capacity on a memory less channel.It has drawn much attention in recent years,and been adopted as the control channel coding for 5G eMMB.Based on the study of the early stopping criterion and update scheduling of flooding belief propagation(FO-BP)decoding algorithm,this paper proposes the X-tolerance early stopping criterion and multi-flooding BP(MF-BP)algorithm,and designs the hardware architecture of MF-BP(M=4)decoder.The main works is as follows.1.By detecting the change of codeword estimates in the process of iterations,a low complexity early iterative stopping criterion,called X-tolerance,is proposed.By constructing a comparison space,X-tolerance only needs to detect a cluster of codeword estimates rather than to detect all bits of estimation,thereby further reducing the computational complexity.Compared with the fixed-iteration 40 times FO-BP algorithm at 3.5dB,the average number of iterations is reduced by 83.1%after applying the X-tolerance criterion,and there is no performance loss.2.By running multiple flood scheduling simultaneously in the factor graph,MF-BP algorithm is proposed,which improves the efficiency of updating soft information.By analyzing the features of the first-stage calculation in the factor graph,the method of optimizing factor graph segmentation of MF-BP algorithm is proposed to avoid the increasing of memory requirements.The test results show that the decoding latency of MF-BP(M=4)can be reduced by 60.6%compared with the FO-BP algorithm at 3.5 dB.3.An MF-BP(M=4)decoder for(1024,512)polar codes was designed.The quantification scheme is(7,4,2),the scaling factor is 0.9375,the maximum number of iterations is defaulted to 40,and the early iteration stopping criterion adopts the X-tolerance.The MF-BP(M=4)decoder is mainly composed of PEs,RAM blocks,HD modules,and Controller modules.Using Verilog FLDL to implement the decoder on Altera Stratix V 5SGXEA7N2F45C2,the operating frequency can acheive 295MHz.When Eb/NO=3.5dB,the decoding delay is 0.1 Ous.The synthesis results of the X-tolerance criterion show that resource consumption is reduced by more than 90%compared to G-Based criterion.Co1pared with the double-column FO-BP decoder,the decoding latency is reduced by 54.5%.