The Channel State Information Acquisition And Transmission Optimization Design Of Massive MIMO

The next generation mobile communication has imposed higher requirements on the performance of latency,transmission rate,connection number,and frequency band utilization.In order to satisfy these requirement via a limited number of space,time and frequency resource,some effective wireless transmission technique are introduced in the new mobile communication systems,which can excavate the potential of increasing spectral efficiency.Among those,massive MIMO based wireless transmission scheme,which are equipped with a large number of antenna array to excavate spatial dimension resource,have been concerned,recently.In addition,the massive MIMO operating in the millimeter wave(mm Wave)frequency can provide more abundant frequency band resource and increase spectral efficiency without the additional time and frequency resource.Nevertheless,in the massive MIMO systems,there are still some burning issues that need to be solved.For example,the massive MIMO array requires lots of pilots and feedback overhead and results in consuming much time and frequency resource in the processing of the CSI acquisition;mm Wave massive MIMO communication need equip with the large number of dedicated RF units to realize the full digital case,which results in high cost RF overhead;the sever path loss of the high frequency signals will increase the system deployment cost so as to meet coverage performance.Therefore,based on these,we conduct the topic “the channel state information acquisition and transmission optimization design of massive MIMO”,the main contributions are listed as following:1.For a massive MIMO downlink frequency division duplex(FDD)system,to reduce the pilot and feedback overhead of channel estimation in FDD systems,a compressive channel estimation and feedback scheme for FDD massive MIMO systems is proposed by utilizing massive MIMO channel beam-blocked sparsity in the beamspace.Particularly,by using the second-order statistic feature,the user of same or similar channel eigenvector can be group into one group,where adopting the DFT matrix realize pilot reuse and transform the spatial MIMO channels into beamspace channels.Meanwhile,since the part of users share the limited scatters at the BS,the users in one group will exhibit the blocked sparsity.By using the sparsity feature,the BS jointly estimate all user's channels via the proposed optimal block orthogonal matching pursuit algorithm.which can reduce the overhead for downlink training.Then,in order to further reduce the feedback overhead,aiming at the feedback sequence,by using the sparsity of pilot sequence,an efficient quantization algorithm is proposed to quantize the amplitude and phase of pilot,respectively.Simulation results demonstrate that the proposed scheme can accurately estimate all user's channels with the few number of pilot than the that of BS antennas.2.To realize the cost-effective large-scale MIMO communications with limited radio frequency(RF)chains,hybrid analog/digital precoding scheme with single-carrier transmission and time delay compensation is proposed.In the scheme,.By leveraging the fact that the mm Wave channels are likely to be sparse in the directions and the signal propagation is usually dominated by the line of sight path(Lo S),the low-complexity single-carrier transmission scheme with time delay pre-compensation applied at the base station(BS)is presented,which can transform the frequency-selective MIMO channels into the flatfading channels.Then,The resulting signal-to-interference-plus-noise ratio(SINR)is derived in terms of the precoding vectors by taking into account both the residual intersymbol interference and inter-user interference.Based on the derived expression,formulating and solving the hybrid digital and analog precoding optimization design problem under the limited number of RF chains.Aiming at the non-convex problem,the original problem can be transformed into the joint codewords selection and precoding problem via the group sparse optimization approach,and propose the bisection based group sparse algorithm.Numerical results are provided to validate the effectiveness of the proposed schemes.3.A lens antenna array with single-carrier transmission and path delay compensation is a promising technique for realizing cost-effective large multiple-input multiple-output communications with limited number of radio frequency chains.Aiming at the frequencyselective channels,by utilizing the angle-dependent energy focusing property of the lens antenna array and the angular sparsity of mm Wave channels,the path delay pre-compensation is applied at the BS.By making the path-delay pre-compensation for the Lo S path between the BS and the MSs,the approximate flat-fading channel is obtained.The resulting SINR is derived by taking into account both the residual inter-symbol interference and inter-user interference.In order to further suppress ISI and IUI,based on the derived SINR expression,formulating and solving joint antenna selective and beaforming design problem to maximize the minimum SINR under the limited number of RF chains case.By utilizing the group sparse optimization,the original non-convex problem can be transformed into the sparse beamforming optimization design problem.Numerical results shows the proposed schemes can obtain the approximate performance with the fully digital case and has a better performance than the conventional orthogonal frequency-division multiplexing mode for the frequency-selectivity channels.4.Aiming at the RF overhead in millimeter wave systems with multiple subarray architecture,the joint subarray selective and precoding design scheme is proposed.By using the fact that the mm Wave channels are likely to be sparse in the directions and the signal propagation is usually dominated by the line of sight path(Lo S),the time delay precompensation technique is applied at the each RF chains connected with one subarray to suppress the ISI.In order to further suppress the ISI caused by the NLo S and IUI from the multi-user transmission,formulating and solving the joint subarray selection and precoding optimization design problem to maximize the minimum SINR under the limited number of RF chain.Aiming at the non-linear mixed integer constraints,the original nonconvex problem can be transformed into the sparse precoding design problem via sparse inspire norm.Then the bisection based convex optimization method is presented to solve the problem.Numerical results validate the effectiveness of the proposed scheme.5.In order to reduce the deliver latency and deployment cost of F-RAN architecture,by utilizing the local cache and signal processing capabilities of the e RRHs,the sequential transmission scheme design base on local cache technique is proposed.In the scheme,according to the files cached or not in the eRRHs,the two-level(caching and network)transmission schemes are proposed,respectively.Aiming at the caching level,formulating the access link precoding design to maximize the minimum SINR under the caching capacity and power of the e RRHs constraints.While,aiming at network level,formulating joint the access and fronthaul link precoding design to maximize the minimum SINR under the caching capacity,fronthaul capacity,and power of the eRRHs constraints.By using the convex optimization method,the original problem can be transformed into the convex semi-definition program problem and solve it.Numerical results validate the effectiveness of the proposed scheme.