Research On Coding Technology In Multi-user MIMO System

Due to the rapid development of wireless mobile communication,higher data transmission rate is needed.Multiple-Input Multiple-Output?MIMO?is one of the key technologies for 4G and 5G wireless mobile communications,which greatly increases the speed of wireless communication.At present,the research hotspot of MIMO system has been developed from single user to multi-user.In order to improve the reliability and effectiveness of the system,the coding techniques in multi-user MIMO system are studied.Space-time coding is an effective method for the system to approach the wireless channel capacity.Precoding can reduce the interference between users.the system performance of concatenated code is studied,and the concatenated code is improved.The research contents are as follows:1)Aiming at the problem of performance degradation caused by interference in channel,the performance of multi-user MIMO system using space-time block code and convolution code or Turbo code concatenate is studied.Convolutional code or Turbo code is used as error-correcting codes,and error control coding is first performed to improve the accuracy of signal transmission,and then space time coding is performed.The diversity gain of space-time block code and the coding gain of convolutional code and Turbo code are fully utilized to improve the performance of the system.The concatenate system is simulated and analyzed under different parameters,compared with space-time block code,the concatenated scheme improves the bit error rate performance of the system.2)Aiming at the problem of inter-user interference in multi-user MIMO system,the performance of multi-user MIMO system using linear precoding and space-time block code concatenation is studied.the signal is first pre-processed by zero forcing?ZF?and minimum mean square error?MMSE?precoding to reduce the interference between users,and then coded by space-time block code to achieve the goal of reducing the system error rate.3)Aiming at the problem of signal performance deterioration after deep fading,further improvement has been made on the basis of the above scheme.After the signal constellation diagram is rotated by the rotation matrix,the rotated signal constellation has good fading resistance.A space-time block code precoding scheme with the rotation matrix is proposed.The system is simulated at different rotation angles,and it is verified by simulation that when the system has 8 user rotation angles of 30°,when the bit error rate is 10^-4,the improved multi-user MIMO system gains about 10 dB compared with the system without rotation matrix.