Research On Massive MIMO Wireless Transmission And Optimal Design For 5G Mobile Communication Systems

With the rapid development of intelligent terminals and network business,a huge number of connection and video traffic explosive growth,The fifth generation(5G)mobile communication system has become an important direction for the sustainable development of mobile communication and even information industry since it has large bandwidth,low latency,the characteristics of wide connection for high definition video,AR/VR represented the characteristics of business application provides technical ability and vertical industry security.Compared with the 4G mobile communication system,massive multiple-input multiple-output(MIMO)has become the most potential research direction of the 5G mobile communication system,which is expected to improve the SE and meet the demand of high transmission rates.Employing a large number of antennas at the base station(BS),each antenna controls channel(or receiving)phase and amplitude of the signal,massive MIMO is able to enhance wide-area coverage,deep coverage,high-rise coverage and other scenes,so as to improve the peak rate,capacity and spectrum efficiency of 5G mobile communication system.However,massive MIMO technology still has many issues in actual deployment,such as precoding design,throughout analysis,antenna array design,hybrid precoding scheme,channel state information(CSI)acquisition and wireless transmission optimization.Therefore,it is of practical significance to carry out research on massive MIMO wireless communication theory and transmission optimization for 5G mobile communication systems.The specific research contents of this thesis are as follows:Firstly,we study the downlink multiuser precoding of massive MIMO system,where the BS has ideal CSI and adopts three type different linear precoding schemes i.e.,maximum ratio transmission(MRT),zero-forcing(ZF)and minimum mean squared error(MMSE).Under Rayleigh fading channel,we obtain the exact expressions on the achievable rate.Moreover,we provide several insight on the SE and reveal the relation of the number of BS antennas,the number of users,as well as the input signal-tonoise ratio(SNR)with the achievable rates respectively.Results show that achievable rate increase with the number of BS antennas and the input SNR,the MRT precoding scheme is inferior to the ZF and MMSE precoding schemes and tends to fixed rate at the high SNR regimes.On the contrary,the MRT precoding scheme outperforms ZF precoding schemes in the low SNR regime.Moreover,we consider an actual power consumption model and further the EE of system.An iterative optimization algorithm is proposed to maximize the EE under the constraint of meeting the reachability rate in order to find the optimal number of antennas and the number of users.Then,we present a quantitative analysis method for two planar antenna arrays and further investigate the detailed performance of two types antenna array,namely uniform rectangular planar array(URPA)and uniform cylindrical array(UCYA).The channel behavior is presented in full-dimensional mmWave propagation conditions by considering both the azimuth and elevation dimensions.We infer the corresponding vectors,radiation directivity and array gain,as well as studied the squared inner product and singular value spread for URPA and UCYA configurations,since these properties reveal which type of antenna array has the less effective interference and stability of channel.We also evaluate the achievable rate with the equal power allocation and waterpouring power allocation schemes.The results show that the UCYA configuration offers the better performance than URPA configuration,since it returns the smaller sidelobe level and has the higher achievable rate.Simulation results that under the same system configurations,the achievable rate can be improved by adopting water-pouring power allocation schemes,while the achievable rate of UCYA configuration always outperforms than that of URPA configuration.Next,we analyze the downlink achievable SE and EE of multiuser massive MIMO for hybrid architectures with phase shifters,where BS has perfect channel state information and baseband precessing adopts zero-forcing precoding.We derive a novel upper bound on the achievable SE for hybrid architectures with ideal phase shifters.Based on the derived analytical,we find that the total achievable SE increases with the number of BS antennas and users,and the signal-to-noise ratio(SNR).To further reduce the hardware cost and power consumption,we also study hybrid architectures with quantized phase shifters,and propose new algorithm to generate corresponding analog processing matrix.A general bound on the achievable SE is derived by utilizing ordered eigenvalue of matrix.Furthermore,we consider a realistic power consumption model and use it to evaluate the achievable EE.Closed-form expressions for the optimal SNR and the number of antennas by maximizing the achievable EE are derived.Compared to existing full-digital architectures,results show that hybrid architectures enjoy a much higher achievable EE,whereas its achievable SE is inferior to full-digital architectures.Finally,we study multi-cell multi-user massive MIMO systems that includes CSI acquisition and wireless transmission optimization.A transmission optimization scheme based on multi-user grouping is proposed and the corresponding theoretical theorem is given.By considering time division duplexing(TDD)mode,the CSI is derived,which is based on uplink and downlink channel reciprocity,the multi-cell massive MIMO system is extended,and all users are grouped by the similarity of the CSI in the target cell,thereby eliminating interference of users.In order to improve the achievable SE of system,we propose two type power allocations that are the maximum-minimum fairness strategy and the maximum SINR product strategy,which joint the users grouping and estimated CSI.The results show that under the same configuration,the SE of the two power allocation strategies is superior to the equal power allocation scheme,while the SE used maximum SINR product strategy is better than one of the maximum-minimum fairness strategy.The simulation results verify the effectiveness of the proposed power allocation algorithm.