Research On Multilevel Coded Modulation System Based On Concatenated Polar Codes

Coded modulation is an advanced technique in wireless communications, where channelcoding and modulation are jointly designed to improve the spectral efficiency and power efficiency.Concatenated code uses two short codes as the inner code and the outer code individually to havebetter error correction capability. A concatenated scheme with polar codes as inner code is namedconcatenated-polar codes, which make full use of the polarization characteristic of polar codes.They have good correction property without increasing the complexity of encoding and decoding.The research on the mulilevel coded modulation scheme based on concatenated-polar codes isinteresting and has a theoretical siginificance.In this thesis, a LDPC-Polar concatenated scheme using LDPC code as the outer code andPolar code as the inner code was proposed in comparison with RS-Polar concatenated scheme. TheLDPC-Polar concatenated scheme is not only strengthens the advantages of the two codes, but alsomakes up of the deficiency of both codes: LDPC codes with good waterfall characteristics areknown to mostly suffer from the error floor problem, while polar codes show very good error floorperformance. Therefore, The LDPC-Polar concatenated scheme consisting of two error-correctingcode achieves the great error performance meanwhile avoiding the error floor problem. Thesimulation results show that the bit error rate performance of the LDPC-Polar concatenated schemehad a great improvement in comparison with the RS-Polar concatenated scheme under differentcode lengthes and code rates.Based on it, a multilevel coded modulation scheme based on concatenated-polar codes waspresented. Two examples, the multilevel coded modulation system based on the LDPC-Polarconcatenated code and the multilevel coded modulation system based on the RS-Polar concatenatedcode were illustrated. They were elaborated detailedly from the determination of code rate and thechoice of decoding method. The performance of the multilevel coded modulation system based onthe LDPC-Polar concatenated code and the multilevel coded modulation system based on theRS-Polar concatenated code were presented under different code lengthes and code rates and werecompared with the results with single-level coded modulation scheme and multilevel Polar codedmodulation scheme. The result shows that the bit error rate performance of the multilevel codedmodulation system had a significant improvement compared with the the single-level codedmodulation system, meanwhile, the bit error rate performances of the multilevel coded modulation system based on the LDPC-Polar concatenated code and the multilevel coded modulation systembased on the RS-Polar concatenated code also had great improvement in comparison withmultilevel Polar coded modulation system. In addition, the bit error rate performance of themultilevel coded modulation system based on the LDPC-Polar concatenated code was better thanthe multilevel coded modulation system based on the RS-Polar concatenated code.