Summary of the concept and advantages of 5g massive MIMO

Concept ： An antenna array of dozens or even hundreds of antennas is arranged at the base station , By beamforming （beam forming） technology , Construct different beams of customers facing multiple targets , And effectively reduce the interference between each beam , The full exploitation of this space resource , It can effectively use valuable and scarce frequency band resources and improve network capacity dozens of times .

advantage ：

（１） Improve spectrum efficiency . According to the law of large numbers , When the number of base station antennas continues to increase to infinity , The channels of different users show asymptotic orthogonality , This characteristic is called favorable channel condition . Theoretically , Interference between users can be completely eliminated , The noise tends to disappear as the antenna increases to infinity . meanwhile , On a large scale MIMO The spatial resolution of is significantly improved , The extremely high degree of spatial freedom can meet the simultaneous communication of multiple users on the same time-frequency resources .

（２） Improve energy efficiency . The use of large-scale antenna arrays , Improved array benefits , Both uplink transmission and downlink transmission can use small transmission power to achieve better communication quality , Thus, the energy efficiency of the system can be improved by several orders of magnitude .

（３） Simplify upper level user scheduling . Random matrix theory shows that , With the rapid increase of the number of base station antennas , It turns out that some random channel characteristics begin to change , For example, the singular value distribution of the channel matrix tends to be determined , The channel matrix tends to be benign , This phenomenon is called large-scale MIMO Channel hardening effect . This makes the number of base station antennas continue to increase , Channel small-scale fading and thermal noise tend to disappear , Thus, users can be prevented from falling into deep decline as far as possible , Reduce the waiting delay of the air interface , Simplify the upper level user scheduling policy .

（４） Reduce system complexity . On a large scale MIMO Simple linear precoder , For example, the maximum ratio is sent , The optimal nonlinear precoding scheme can be achieved （ Such as dirty paper coding ） Approximate performance , Thus greatly simplifying the system complexity .

（５） Reduce system deployment costs . On a large scale MIMO Extremely high spatial freedom , It can be used for beam forming , If a constant envelope modulation signal is used , It can greatly reduce the peak to average ratio of the transmitted signal , Thus, low linear complexity can be adopted in the RF front-end 、 Low cost 、 Low power hardware devices , Significantly reduce deployment costs .