Showing papers by "Mats Bengtsson published in 2003"
06 Apr 2003
TL;DR: Using ideas from power control and downlink beamforming, a pragmatic approach is suggested for spatial multiplexing in systems with several access points, each serving one or more mobile terminals with equal rate on the spatial channels.
Abstract: Using ideas from power control and downlink beamforming, we suggest a pragmatic approach for spatial multiplexing in systems with several access points, each serving one or more mobile terminals. We assume that all channels are known globally, but in the case of fast fading, it is sufficient to know the second order statistics of the channels. Robustness to channel estimation errors is easily incorporated in the algorithm. Since global channel knowledge is required, the algorithm is mainly intended for system simulations where it provides a benchmark for the performance of any spatial multiplexing scheme with equal rate on the spatial channels.
9 citations
09 Nov 2003
TL;DR: It is shown that the QoS requirements can be formulated as quadratic constraints to a convex optimization problem, and an efficient algorithm for solving the problem, based on semidefinite optimization is presented.
Abstract: This work addresses the problem of joint downlink beamforming and power control with general quality of service (QoS) constraints. Previous work on downlink beamforming does not provide a framework to handle the additional constraints in a straightforward fashion. Herein, it is shown that the QoS requirements can be formulated as quadratic constraints to a convex optimization problem. An efficient algorithm for solving the problem, based on semidefinite optimization is presented. To demonstrate the performance of the proposed approach, we present an example using quadratic constraints to greatly decrease the probability of a low instantaneous signal to interference and noise ratio (SINR) for a receiver equipped with a RAKE combiner.
6 citations