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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Solution of the multiuser downlink beamforming problem with individual SINR constraints
 IEEE transactions on vehicular technology 53 (2004), No.1, pp.1828 ISSN: 00189545 

 English 
 Journal Article 
 Fraunhofer HHI () 
Abstract
We address the problem of joint downlink beamforming in a powercontrolled network, where independent data streams are to be transmitted from a multiantenna base station to several decentralized singleantenna terminals. The total transmit power is limited and channel information (possibly statistical) is available at the transmitter. The design goal: jointly adjust the beamformers and transmission powers according to individual SINR requirements. In this context, there are two closely related optimization problems. P1: maximize the jointly achievable SINR margin under a total power constraint. P2: minimize the total transmission power while satisfying a set of SINR constraints. In this paper, both problems are solved within a unified analytical framework. Problem P1 is solved by minimizing the maximal eigenvalue of an extended crosstalk matrix. The solution provides a necessary and sufficient condition for the feasibility of the SINR requirements. Problem P2 is a variation of problem P1. An important step in our analysis is to show that the global optimum of the downlink beamforming problem is equivalently obtained from solving a dual uplink problem, which has an easiertohandle analytical structure. Then, we make use of the special structure of the extended crosstalk matrix to develop a rapidly converging iterative algorithm. The optimality and global convergence of the algorithm is proven and stopping criteria are given.