Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Solvability of coupled downlink beamforming problems

: Schubert, M.; Boche, H.


Institute of Electrical and Electronics Engineers -IEEE-:
GLOBECOM '01, IEEE Global Telecommunications Conference. Vol.1 : San Antonio, Texas, USA, 25 - 29 November 2001
Piscataway: IEEE Operations Center, 2001
ISBN: 0-7803-7206-9
ISBN: 0-7803-7207-7
ISBN: 0-7803-7208-5
GLOBECOM <2001, San Antonio/Tex.>
Fraunhofer HHI ()
adaptive signal processing; antenna radiation patterns; array signal processing; cellular radio; cochannel interference; convergence of numerical methods; interference suppression; iterative methods; multiuser channels; optimisation; power control; telecommunication control; coupled downlink beamforming problems; downlink power control; cellular wireless systems; signal-to-interference level; iterative algorithms; nonlinear optimization problem; multiple antennas; spatial signal processing; cochannel interference reduction; radiation patterns; multiuser interference

We address the problem of joint downlink beamforming and power control in interference limited cellular wireless systems. The goal is to support each user with a certain signal-to-interference level at the mobile. Several iterative algorithms have recently been proposed in the literature to solve this non-linear optimization problem. Obviously, no solution exists if the requirements are too demanding. This explains situations where the algorithms do not converge. On the other hand, the observation of convergence is only a necessary condition for the existence of a solution. We investigate the analytical structure of the problem and formulate a unifying framework. In particular, we provide a necessary and sufficient condition which can be used to judge whether or not a solution can be considered as valid. The results give new insights and may prove useful for the design of new fast convergent algorithms.