Research On Wireless Transmission Technology Of Distributed Massive MIMO Systems

In order to meet the society's increasing demand for high data transmission rates,largeamount access terminals,and high-reliability and low-latency communications,the 5th Generation Mobile Communication Systems(5G)will bring some new physical layer transmission technologies.Distributed massive multiple-input multiple-output(MIMO),as a highly potential networking technology,can effectively improve the wireless network coverage characteristics by arranging antenna units in different geographic locations,and at the same time,the utilization of spectrum resources has also been significantly improved.This paper mainly focuses on the problem of full-duplex antenna working mode selection and millimeter wave transmission beam tracking in distributed massive MIMO systems.First,the relevant theoretical basis of the distributed massive MIMO system is introduced.It mainly includes the statistical propagation model of wireless signals,the related theories of MIMO channels and distributed MIMO systems,two commonly used precoding schemes in communication systems,etc.Moreover,the simulation verified the superiority of the distributed system compared to the centralized system in terms of signal-to-interference and noise ratio performance.Secondly,the problem of antenna working mode selection in distributed full-duplex massive MIMO system is studied.By setting the antenna selection vector,the model of receiving and transmitting signals under the distributed full-duplex massive MIMO system is derived,and the problem of antenna mode selection is transformed into an optimization problem of minimizing the mean square error of the received signal.Since the optimization problem is a non-convex discrete non-deterministic polynomial(NP)problem,a solution based on a parallel successive convex approximation(PSCA)algorithm is proposed.By using the first-order Taylor expansion and continuous relaxation of the solution space,the non-convex part of the optimization problem is transformed into a solvable convex problem,and an approximate solution of the problem is obtained.The simulation results show that the performance of this algorithm is greatly improved compared with random allocation,and it is closer to the performance of exhaustive method.Then,based on the system model and problem in Chapter 3,the problem of antenna working mode selection in distributed full-duplex massive MIMO system is studied from another perspective,and an antenna working mode selection scheme based on optimal retention genetic algorithm is proposed.By transforming the problem of antenna mode selection into an optimization problem of maximizing system and spectrum efficiency,and adopting a genetic algorithm based on optimal retention,the problem is solved.In the process of population evolution,the optimal retention strategy is selected to ensure that the optimal individual will not be lost due to cross-mutation and other reasons.The simulation results show that the performance of this algorithm is much better than the random allocation algorithm,and it is also improved compared with the PSCA algorithm,which is closer to the performance of exhaustive search.Finally,the beam tracking problem under the distributed millimeter-wave massive MIMO system is studied.By using the monopulse technology in the radar system,the user's angle of arrival(Angle-Of-Arrival,AOA)acquisition scheme under the millimeter wave distributed MIMO system is derived.In addition,a tracking algorithm based on the unscented Kalman filter is proposed to study the AOA tracking problem under the nonlinear observation equation.The simulation results show that the algorithm has better tracking performance than observations at different signal-to-noise ratios and different antenna numbers.