The Research Of Massive MIMO And Its Implementation

With the rapid development of mobile internet,there exists great demand for increasing wireless throughput speed,which calls upon the 5th generation(5G)of mobile technology.As the main candidate of 5G,massive Multi-Input-Multi-Output(MIMO)technology is extensively researched due to its capability to increase power efficiency and system throughput.In order to fully evaluate massive MIMO techonology under real scenarios,it's of great importance to build a prototype system in advance,which can not only verify the theoretical results but also find the potential of the techonology.One major aim of this work is to implement the key modules in massive MIMO techonology,typically in the physical layer.Thus a 128×12 massive MIMO prototype system is designed and implemented.The details of this work is organized as follows:Firstly,the hardware architecture and the data processing procedure of the prototype system are introduced.Hardware architecture includes all the devices used and the wiring between them,as well as a clock distribution system across all the radio devices.The data processing procedure of both uplink and downlink is fully explained,from transmission to reception.Next,a timing synchronization method for massive MIMO is proposed.The uplink multi antenna timing synchronization method is proposed based on the traditional single antenna synchronization method,which is followed by the propose of the downlink timing synchronization method.The validity of both the uplink and downlink method is proved by simulation results.After that,the hardware module of timing synchronization is designed and added to the prototype system.The result of the test in real environment shows that the timing synchronization module works perfectly,which allows real-time video streaming.Then,an optimized uplink frequency synchronization method for massive MIMO is proposed,which includes carrier frequency offset estimation and correction.Simulation results show that the proposed frequency method can not only precisey estimates the frequency offset,but also correct the phase rotation caused by it.After that,the hardware module of frequency synchronization is designed and added to the prototype system.The result of the test in real environment pictires clear and well-positioned constellation diagram,indicating that the frequency synchronization module functions as expected.Last,the massive MIMO prototype system is tested in real environment with the hardware modules of channel encoding/decoding,constellation mapping/demapping and channel reciprocity calibration are designed and implemented.The prototype system supports 128 antennas at the base station and distinguishes 12 users at most.Transmission bandwidth for single user is 20 MHz.Multiple constellation mapping schemes including QPSK 16QAM,64QAM,256QAM are supported The maximum throughput for the prototype system is 1.3 82Gb/s and the power efficiency is 69.lbit/s/Hz.