Study On Equal Gain Combining And Transmission Technique For Massive MIMO Systems

Over the last decade,the multiple-input multiple-output(MIMO)technology in wireless communication with small-scale antenna configuration has been greatly devel-oped into mature,which has experienced from single-user to multi-user.However many performance limitations still exist such as energy efficiency>spectrum efficiency?robustness and reliability.To this end,in 2010,Marzetta proposed the massive MIMO technology,which increasing the number of antennas of base stations significantly.Massive MIMO can take good advantage of the radio resources of spatial dimension and improve the performance limitations of MIMO with small-scale antenna configura-tion.Since massive MIMO has a huge advantage in energy efficiency?spectrum effi-ciency?robustness and reliability,it has become the most potential technology of wire-less communication in 5G and one of the most challenging research direction.However massive MIMO is in its infancy in many aspects.For example,the linear precoding and estimation technology does not conduct in-depth discussion about the equal gain com-bining(EGC)of uplink and the equal gain transmission(EGT)of downlink which is widely used.First,the thesis analyzes the achievable rate of equal gain combing under the sce-nario of multi-cell multi-user MIMO with perfect or imperfect CSI and simulates the system performance of EGC,maximum ratio combing(MRC)and zero forcing(ZF).The results show that perfect CSI situation has better performance than imperfect situa-tion;It can appropriately increase the achiexable rate by increasing the transmission power of the user and the number of the base station antennas;When the power scaled factor increases,the system performance can increase firstly.But when it exceeds a cer-tain value,the system performance will drop.Next,we analyze the achievable rate of EGT uder the scenario of massive multi-cell multi-user MIMO system with or without DL pilot and compare with the maximum ratio transmission(MRT)and zero forcing(ZF).The simulation results show that the derived formula is accurate;The EGT sys-tem has a good performance in low SNR region.The EGT system with DL pilot may have advantage over the EGT system without DL pilot under scenarios with small cross-cell interference lever,small pilot overhead with respect to the frame length,and small number of users.In most of the scenarios investigated by comparing the EGT,MRT and ZF,ZF has a better performance than EGT and MRT,because ZF precoding method has a larger ability of interference suppression.However,when the number of antennas increases,the performance of the three precoding method tends to a approxi-mate rate.The performance gap between the maximum rato transmission and equal gain transmission is very small.At last,it is worth that EGT has a lower complexity in the practical implementation.Therefore we should promote the use of them in practical massive MIMO system.