On Key Technologies Of Scaled Antenna Array Systems Based On Hybrid Analog/Digital Architecture

With the proliferation of portable mobile terminals and the explosive growth of Internet data traffic,the demand of high rate and high quality wireless communication networks from the users is becoming higher and higher.Multiple-input and multiple-output(MIMO),as a new generation of wireless transmission technology,can exponentially increase the spectrum efficiency and link quality.In recent years,MIMO related theoretical research results have shown that MIMO system can obtain greater spatial freedom with the increasing scale of antenna arrays.Moreover,the data rate and reliability of the system is extremely improved.Thus,to meet the increasing data rate requirements of users,massive MIMO technology,i.e.large scale antenna array MIMO technology,will have a very broad application prospects in the future communication systems.Generally,hybrid analog/digital architecture is utilized in large scale antenna array systems due to the cost and power consumption of radio frequency(RF)chains.In hybrid analog/digital architecture,the conventional full digital precoding procedure is divided into tow parts,noted as analog precoding procedure and digital precoding procedure.The number of needed RF chains is greatly reduced through this split processing.In this paper,optimization problems for scale antenna array systems based on hybrid analog/digital architecture are investigated.Moreover,specific hybrid precoding schemes for single-user and multiple-user systems are proposed.Besides,this paper also considers the practical deployment of scale antenna array systems based on hybrid analog/digital architecture and focuses on the solution of channel quality indicator(CQI)table design and feedback problems after the introduction of higher order modulation schemes.The main contributions and novelty of this paper lie in:Firstly,this paper investigates the optimization of hybrid precoding schemes for single-user hybrid analog/digital systems.The differences in hybrid precoding design between partially connected structure system and fully connected structure system are analyzed.Then,this paper proposes hybrid precoding schemes for high signal-to-noise ratio(SNR)condition and low SNR condition,respectively.Moreover,upper bounds of the achievable data rate for the proposed schemes with closedform expression are derived.Secondly,this paper investigates the optimization of hybrid precoding schemes for multi-user hybrid analog/digital systems,both single-carrier and multi-carrier systems are considered.For single-carrier multi-user systems,the optimization of spectral efficiency is investigated.In the analog domain,the optimization objective is to maximize the sum of each user's equivalent channel gain.The optimal analog precoding matrix is then obtained by transferring the original problem into convex problem.In the digital domain,block diagonalization(BD)algorithm is utilized to eliminate the multi-user interference.It can be seen from the simulation results that significant equivalent channel gain is obtained by the proposed algorithm.Moreover,the system performance under single-path channel is improved.For multi-carrier multi-user systems,max-min signal to interference plus noise ratio(SINR)problem under the total power constraint for hybrid analog/digital millimeter wave system is investigated.This paper improves the conventional iterative optimization scheme and proposes a two-stage hybrid precoding scheme with fixed analog precoding weights.In this way,the complicated iteration procedures between the optimization of analog precoding weights and digital precoding weights are bypassed so as to decrease the complexity of the system.The performance of the proposed scheme is evaluated and compared with that of the conventional iterative algorithm.Channel model defined in 802.11 ad is used in the simulation and line-of-sight scenario is considered.It can be seen from the simulation results that the performance of the proposed algorithm is close to or even higher than that of the iterative algorithm.Thirdly,this paper considers the practical deployment of scale antenna array systems based on hybrid analog/digital architecture and focuses on the solution of channel quality indicator(CQI)table design and feedback problems after the introduction of higher order modulation schemes.This paper proposes a future-proof extendable CQI table design scheme to support higher-order modulation schemes.Meantime,in order to support the proposed extendable CQI table,a two-stage feedback scheme is proposed in this paper.Moreover,an adaptively window-index update method is also proposed in order to decrease the feedback overhead.The performance of the proposed extendable CQI table design scheme is compared with the fixed-size CQI table design in 3 GPP Release-12.Simulation results show that the throughput of cell edge users is obvious enhanced and there is no performance loss on the cell center users by utilizing the extendable CQI table.