Synchronization And Control Information Transmission For Massive MIMO Systems

With the further development of the information society,the multiple-input multiple-output(MIMO)technique has become a key enabler for the 5th generation(5G)mobile communication systems.With spatially directional signaling formed by the massive antenna array deployed at the base station(BS)side,tens of active users on the same time-frequency resource can be served by the massive MIMO system simultaneously.This feature can cope with the rapidly increasing demands of wireless data services and the challenges brought by new business requirements.On one hand,the studies on the dedicated channels engaged in the exchange of user specific data have been investigated intensively.On the other hand,many essential common messages or services are provided to all the users rather than only certain active users through public channels.The feature of public channel transmission creates the demand of broad coverage precoder design for the massive MIMO system.Meanwhile,the power efficiency is crucial for the synchronization and control messages transmission process.To address the aforementioned issues,this dissertation studies synchronization and control messages transmission for massive MIMO systems with the broad coverage precoder design schemes.Firstly,the precoder design scheme for the massive MIMO system with the uniform linear array(ULA)is proposed,which can satisfy the equal transmit power per-antenna constraint and the semi-unitary constraint simultaneously.The precoder design algorithm is created by the manifold optimization methods and alternating projection theory.In order to guarantee efficient use of power amplifiers and improve the achievable ergodic rate,equal transmit power per-antenna and semi-unitary constraints on the precoding matrices are considered simultaneously.Within the framework of manifold optimization,the precoding matrix design under the above two constraints become an optimization problem over the intersection of the oblique manifold and the Stiefel manifold.We propose to use the steepest descent method on the intersection of these two manifolds to obtain the optimal solution.By using the alternating projections method,the search direction of the steepest descent method is derived.In the meanwhile,the convergence analysis for the proposed approach is also provided.The proposed approach can be used for both omnidirectional and sector-shaped power pattern design.Simulation results show that the power pattern of our designed precoder has less variation in different spatial directions within the cell coverage compared with the existing Zadoff-Chu(ZC)scheme.Then,the precoder design scheme for the massive MIMO system with the uniform rectan-gular array(URA)is proposed,where the design criterion is based on pursuing the fairness of synchronization performance.This performance metric is characterized by the missed detection(MD)probability of all the users in the cell coverage area.Compared with the precoders de-signed by half power beam-width(HPBW),the proposed scheme has a better synchronization performance.The synchronization performance can be characterized by the MD probability.By considering the MD probability fairness in the cell,we formulate a criterion for the precoder design.Moreover,we consider the equal transmit power constraint on each antenna to effi-ciently utilize the power amplifier(PA)capacity of the BS.By using the manifold optimization framework,we design the precoder under the aforementioned criterion and constraint.Simu-lation results show that the fairness among all the users in this cell can be ensured.Compared with the precoders designed by half power beam-width(HPBW),the proposed scheme causes much less inter-cell interference and has a better synchronization performance.Finally,the precoder design scheme for the massive MIMO system for the satellite commu-nication systems equipped with the URA is proposed,where the performance metric is chosen as the benchmark of symbol timing offset and frequency offset estimation problem.Compared with the aforementioned fairness criterion,the newly proposed minimax criterion helps the users to further obtain the gains while the calculation complexity is reduced accordingly.The modi-fied Cramér-Rao vector bounds(MCRVB)are chosen as the benchmark of symbol timing off-set and frequency offset estimation problem,which can be viewed as the time and frequency synchronization performance metric for the broad coverage precoder design.By considering the minimax MCRVB criterion and the equal transmit power constraint on each antenna,the precoder design problem is formulated as the non-convex constrained minimax problem over the discrete radiation power pattern.This optimization problem is solved by the smoothing techniques combined with the manifold optimization method.To reduce the calculation com-plexity,the nonmonotone conjugate gradient method is applied.Simulation results show that the average and the minimum received powers in the coverage area of the proposed scheme is higher than those of the scheme based on fairness criterion.Compared with the existing om-nidirectional and broad coverage schemes,the proposed scheme has the best synchronization performance.