A Study On Relay Collaborative Transmission Of Rate And Length Adaptive Polar Code

In order to meet the transmission requirements of high quality multimedia services,wireless networks with higher transmission efficiency are urgently needed.In the future,wireless networks should not only have high capacity and reliability,but also have high mobile rate and spectrum utilization.Collaborative transmission is a virtual multiple input multiple output(MIMO)technology that can obtain diversity gain.Polar code is a coding technique that can reach the Shannon limit in theory.Both of them can effectively improve the reliability and effectiveness of the transmission link.Based on these two communication technologies,in this papaer a scheme of punctured pattern selection is proposed to overcome the shortcomings of the existing punctured polar code.And then the rate and length adaptive polar code are used for cooperative transmission.For the cooperative transmission problems of polar codes with different cooperative protocols,the corresponding cooperative scheme of polar code encoding is given.The main contents and innovations are summarized as follows:(1)In this paper,we introduce the theory of relay cooperative transmission and the theoiy of polarization encoding and decoding respectively.Firstly,the relay transmission model,relay selection and power allocation are introduced.The amplification and forwarding(AF)cooperation protocol,decoding and forwarding(DF)cooperation protocol are emphatically analyzed.Then,the channel polarization theory and coding method of polar code are introduced,and decoding methods of successive cancellation(SC)decoding and belief propagation(BP)decoding are analyzed.Finally,Monte Carlo algorithm,density evolution algorithm and Gauss approximation algorithm are analyzed and compared.(2)The length of polarization codes originally obtained from polarization theory is limited to the power of two.In order to obtain the code length adaptive polarization code,in this paper,we proposes a new puncturing pattern selection scheme which is based on feedback cost puncturing to generate shortened polar code.In this scheme,the polarization effect is reserved,the sub-optimal sub-channel is selected as the cost bit?the output bit corresponding to the cost bit is used as the puncturing pattern,and then the value of the cost bit is adjusted by feedback to obtain the shortened polar code.Simulation results show that the performance of the proposed shortened polar code is better than that of the shortened polar code generated by bit-reversal permutation method,and the shortened Polar code generated by direct puncturing method at the end under different channel and code rate conditions.In the AGWN channel,when the block error rate is 10-3,the proposed shortened polar code with a code rate of 0.5 can obtain a gain of 0.5 dB compared with the shortened polar code generated by bit-reversal permutation method,and the coding performance is greatly improved.(3)Rate and length adaptive polar code is applied to cooperative transmission,and the encoding and decoding strategy of rate and length adaptive polar code can be adjusted according to the different cooperative protocols.In order to further improve the spectral efficiency of cooperative systems,a cooperative coding method based on puncturing polar code is proposed in this paper under the condition of coding cooperation(CC).In this method,the information is divided into variable-length code words N1 and N2 by using the theory of puncturing polar code encoding.The code words N1 and N2 are transmitted through the source node S and the relay node R respectively to complete cooperative transnission.Finally,at the destination node D?the information is decoded through complementary information combination.The simulation results show that,compared with non-cooperative,under the same power consumption conditions,the puncturing polar code with CC cooperation can obtain better performance,and the overall power consumption of the system can be lower under the same performance.Compared with AF cooperation and DF cooperation,CC cooperation is better in Gauss channel,and DF cooperation and AF cooperation are better in Rayleigh fading channel.