A new approach to power adjustment for spatial covariance based downlink beamforming

When using downlink beamforming at the base station of a cellular system, care must be taken to assure that all users satisfy the given SINR requirements. Generally, this leads to a computationally prohibitive joint optimization problem, therefore decoupled techniques based on eigenvalue decomposition of the spatial covariance have been proposed. However, these techniques require additional power adjustment of the steering vectors in order to satisfy the given SINR requirements. Conventional power control schemes are not suited for this purpose because the SINRs primarily depend on the shape of the radiation patterns. In this paper we propose a new power adjustment algorithm, which adjusts the beamforming weights, such that all users have the same SINR. Additionally, it is possible to limit the maximum radiated user power.