Research On Design Method Of Precoding Codebook Based On Channel Coding

With the development of the fifth-generation mobile communications(5G)era and the application of large-scale MIMO(Multi Input Multi Output)systems,the base station has an increasing demand for the number of antenna arrays.In a FDD(Frequency Division Duplex)system,because of the different transmission frequencies adopted by the uplink and downlink channel,the uplink and downlink channel matrices no longer possess the characteristics of mutual conjugate transpose like TDD(Time Ddivision Duplex).In order to obtain the downlink channel matrix information,the limited feedback technology has been proposed.However,the capacity of the feedback channel in its technology is limited to a certain range,which makes the transmitter's acquisition of CSI(Channel State Information)incomplete and inaccurate.In this way,in order to make the large-scale MIMO system achieve the system capacity,a precoding technology based on codebook has became one of the effective means.The precoding performance of codebook is closely related to codebook design.The rapid development of 5G requires the base station to provide more antenna arrays,which makes the precoding codebook expand from the traditional lower dimension to the high-dimensional space,and brings high complexity of codeword search.It is very difficult to realize the design.At the same time,there are many reasons for the traditional RF link architecture to require the precoding codewords to satisfy the constant modulus constraint.This thesis puts forward two corresponding solutions to the above problems.First,an important idea in channel coding is applied to design the codebooks.In fact,adding redundant code words makes the minimum distance between code word sequences as large as possible in the coding process,so as to reduce the bit error rate and realize error controllable.Based on this idea,a channel coded codebook is applied to design a precoding codebook.The basic idea is to realize the one-to-one mapping from domain of channel coding to the precoding codebooks.The proposed codebook design method can realize codebook mapping in high dimensional space,at the same time,it improves the availability of codebook construction and reduces the computational complexity of the system.Second,a method to quickly find a precoding codeword that satisfies the current channel characteristics in the high-dimensional precoding codebook constructed above is proposed.In this thesis,a fast decoding method of convolutional codes,such as Viterbi decoding method,is selected as the research object.The greatest feature of the proposed searching method is that when calculating and comparing the distance between branch paths,the component product between codeword sequences replaces the traditional definition of Hamming distance or Euclide distance as a measurement.Finally,the effectiveness of the proposed the codebook's design and the fast algorithm is verified by simulation,which can design high-dimensional and effective precoding codebooks.At the same time,complexity of codeword search is also be reduced.