A Research On Power Allocation Based On LDPC Codes In MIMO Channel

Nowadays,5G communication technology has been commercially launched in 2020.In addition to people's increasingly high requirements for reliable communication,mobile communication is also facing more and more complex application scenarios.And communication terminals are also more diverse to meet the needs of the Internet of Things.The Third Generation Partner Program(3GPP)reconsidered coding gain,rate compatibility,hardware implementation and other factors,and ultimately decided that 5G New Radio(NR)would use Low Density Parity Check(LDPC)codes replacing Turbo codes as channel coding on the scenario of enhanced mobile broadband(eMBB).The use of LDPC codes in 5G re-attracts a lot of interest and attention including the encoding,decoding and their optimization methods.Another key technology in NR called multiple input multiple output(MIMO)can effectively increase channel capacity without additional bandwidth.However,the increasing complexity of the communication system combining multiple technologies makes the mathematical analysis of the system as a whole more and more difficult.The joint optimization of LDPC codes and MIMO technology still remain unsolved.So far,most studies only consider LDPC codes separately from MIMO systems.This thesis mainly studies the closed-loop precoding power optimization scheme for LDPC codes in MIMO channel.We innovatively analyze and optimize them as a whole.By analyzing the LDPC codes based on Gaussian approximation tool in equivalent MIMO channel,we deduces the optimal power optimization scheme for LDPC codes.The simulation results demonstrate the optimization can bring obvious gain.The first chapter of this thesis introduces the background and development of the relevant researches,the development history of LDPC codes and the MIMO technologies and precoding under MIMO channel.In the following,we explain power optimization and the difficulties in this scenario and introduce the power optimization problem of LDPC codes under MIMO channel.In the second chapter,the related research of LDPC code and the related theory of MIMO precoding technology are introduced.The structure of LDPC codes is introduced in detail first,then the encoding and decoding algorithms of LDPC codes are described.Finally,the performance evaluation of LDPC codes based on Gaussian approximation method is described in detail.This method can analyze LDPC code performance quickly and effectively and it will be our basic theory in the following chapters.For MIMO precoding,we mainly study on the equivalent channel after closed-loop precoding of MIMO channel and give the equivalent subchannel models obtained by different precoding methods,which will be used in Chapter 3 and 4.In the third chapter,we mainly study the joint power optimization of regular LDPC codes in equivalent MIMO subchannel.In this chapter,a mathematical model for regular LDPC codes in equivalent MIMO subchannels is derived using Gaussian approximation,and then an optimal power allocation scheme is derived based on this model.The effectiveness of the scheme is finally verified by experimental simulation.In Chapter 4,the joint power optimization of irregular LDPC codes in equivalent MIMO subchannels is discussed.Irregular LDPC codes are more complex than regular LDPC codes so that the results derived in Chapter 3 cannot be directly applied to irregular LDPC codes.Therefore,the Gaussian approximation and power optimization of irregular LDPC codes are re-derived in this chapter.Finally,the fifth chapter summarizes the contents of the thesis and gives the possible research interests.