Study Of The Basic Theory And Applications Of Large Scaled Antenna Array

Massive MIMO system uses lager number of antennas at the base station to break down the spatial resource,solved the inherent problem of broadcasting natural in mobile communication system who wastes spectrum and time resource.By providing every user an independent channel to the base station,every user could access to all the time and frequency resources without creating conflicts,so the spectrum efficiency can be multiplied by the number of users.The alternation from sharing to reusing the spectrum and time resource does not only change the network structure but also simplifies resource management and inter user interference.Furthermore,with excessive number of antennas at the base station,the received SNR could also be increased by the array gain and the fast fading would be vanished.So,massive MIMO system is the key technology in 5th generation celluer network.In this dissertation,we start with discussing the problems in current wireless communication system.Then we introduce the antenna array and analyze its applications.Through the analyzes,we conclude that:first,to better understand the wireless communication and antenna array we need to study the wireless channel,especial the spatial domain function of the channel;second,the massive MIMO system has great potential in celluer network,but its performance is still limited by the pilot contamination;third,the anti-multipath-effect capability of larger scaled antenna array could also be utilized in other applications.Therefore,in this dissertation,we focused on these three fields to study the larger scale antenna system.In chapter two,the existing channel models and their effects to wireless communication systems are discussed.A three-dimensional angle of arrival(AoA)and power of arrival(PoA)joint distribution channel models are proposed.These models use random located scatters to construct the channel to provide more general 3D channel models,the simulation results of these models have high consistency with the measurement results than the exist models.The third chapter of this dissertation analyzes the performance of cellular network adopting massive MIMO.The results show that the main bottleneck of massive MIMO in the cellular network is the pilot contamination.Then,we propose a method which could eliminate inter-cell interference caused by pilot contamination using two stages pilot transmission and two stages channel estimation to realize inter-cell cooperation.The simulation results show that this method can effectively eliminate the problem of inter-cell interference.The system performance could be lead to infinite when the number of antennas tends to infinity,thus removing the bottleneck effect of massive MIMO in cellular network.In the fourth chapter,other applications of large-scale array system are introduced.We first discuss the optimization synthesis of antenna array and propose a multi-objective differential evolution optimization algorithm to improve the performance of the unequally spaced array.The algorithm can reduce the size of the array with lower sidelobes.Then,we propose a blind modulation classification scheme using large-scale antenna array by taking advantage of its anti-multipath-effect.By combining with different signal processing methods,the performance can be further improved.The simulation results indicate that by adopting of large-scale antenna system combined with signal processing algorithms the accuracy of blind modulation classification in multipath environments can be effectively improved.This study further demonstrates the potential of large-scale array system.