| Polar code is an encoding scheme which can reach the channel capacity theoretically.In order to solve the problem that the performance of polar code under medium and short code length is still poor,this thesis improves the BLER performance by concatenating external codes and improving decoding algorithm.The following three aspects are studied in this thesis:1.First,this thesis research the PC concatenated polar codes based on polarization weight,then simulate and compare the BLER performance of different single concatenated polar codes.After that,this thesis proposes an improved PC-CRC concatenated polar encoding scheme,in which PC bits are set to two consecutive bits,CRC bits are placed at the end of the codeword vector,the decoding rules are improved according to the encoding scheme.Compared with the original method,the simulation results show that the proposed method has about 0.14 dB gain of BLER performance when the code length is 256.When the code length is 512,it has about0.13 dB gain of BLER performance.The proposed scheme is better than other methods in the whole SNR range.2.The placement position of CRC bits is studied.In this chapter,CRC is placed in the middle of the information vector,and two new cascade schemes(scheme 1 and scheme 2)are proposed.The simulation results show that the BLER performance of scheme 2 is better than scheme 1,and the BLER gain of scheme 2 is about 0.1dB compared with the original method.Although the BLER performance of scheme 2 is slightly worse than the improved PC-CRC cascade scheme,it can terminate the decoding ahead of time and reduce the decoding delay,which has a certain research reference value.3.The BER performance of BP and SCAN decoding algorithm are simulated and compa-red,then the cascaded polarization code based on BP decoding algorithm is studied,which mainly adds CRC as external code.The simulation results show that the CRC-assistedBP decoder can reduce the number of iterations by 84.5% in Eb/N0=4.0dB. |
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