In this paper,a beamforming scheme to improve the coverage in high-speed railway commu-nication systems is investigated.A dedicated coverage model,where the coverage cell is an ellipse rather than the traditional circular or linear,is considered.Based on the elliptical coverage cell,an optimization prob-lem for the beamforming design is formulated to max-imize the percentage of railway coverage,subject to the constraints on equal expected designed propaga-tion gain(the gain obtained by a combination of de-signed beam and propagation channel)on the ellipti-cal curve,i.e.,the expectation of designed propaga-tion gain on the elliptical curve are all equal.Consid-ering that the coverage can be improved by increas-ing the minimum designed propagation gain on the railway,the problem can be recast to maximizing the equal expected designed propagation gain on the ellip-tical curve.Subsequently,a beamforming design with an improved β-fairness power allocation,where the optimization problem is formulated to maximize the minimum expected received power over time with the constraints on elliptical cell based beamforming and mobile service amount,is proposed to further improve the coverage.An alternating iteration algorithm is de-veloped to find the optimal beamforming vector and the instantaneous transmit power.Through numerical results,it is found that the beamforming designed on the elliptical curve covers longer railway than beam-forming designed on the railway directly,and the cov-erage of elliptical cell based beamforming can be in-creased with the eccentricity.In addition,beamform-ing with the improved β-fairness power allocation can further improve the railway coverage and mobile ser-vice amount simultaneously.Moreover,it is shown that the larger eccentricity of the ellipse with appro-priately chosen BS location,the larger coverage dis-tance.

Ximei Liu;Deli Qiao

School of Communication and Electronic Engineering,East China Normal University,Shanghai 200241,China

中国通信（英文版）

[1]Ximei Liu;Deli Qiao-.Elliptical Cell Based Beamforming Design with an Improved β-Fairness Power Allocation for HSR Communication Systems)[J].中国通信（英文版）,2022(05):112-128

Elliptical,Fairness,imize,ellipti,Consid,ellip,beamform

Cell,Based,Beamforming,Design,Improved,Power,Allocation,HSR,Communication,Systems,In,this,paper,beamforming,scheme,coverage,high,speed,railway,commu,systems,investigated,dedicated,model,where,cell,ellipse,rather,than,traditional,circular,linear,considered,elliptical,optimization,formulated,percentage,subject,constraints,equal,expected,designed,gain,obtained,by,combination,propagation,channel,curve,expectation,are,ering,that,can,improved,increas,minimum,problem,recast,maximizing,Subsequently,fairness,power,allocation,maximize,received,mobile,service,amount,proposed,further,An,alternating,iteration,algorithm,veloped,find,optimal,vector,instantaneous,transmit,Through,numerical,results,found,covers,longer,directly,creased,eccentricity,addition,simultaneously,Moreover,shown,larger,appro,priately,chosen,BS,dis,tance

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