Enhanced multiuser random beamforming : dealing with the not-so-large number of users case

Kountouris, Marios;Gesbert, David;Sälzer, Thomas
IEEE "Journal on Selected Areas in Communications", Special Issue on Exploiting Limited Feedback in Tomorrow’s Wireless Communications Networks, Vol.26, N°8, October 2008

We consider the downlink of a wireless system withM-antenna base station and K single-antenna users. A limitedK regime. Unfortunately,K values,K), at the cost of moderate complexity increase.


feedback-based scheduling and precoding scenario is considered

that builds on the multiuser random beamforming (RBF). Such

a scheme was shown to yield the same capacity scaling, in terms

of multiplexing and multiuser diversity gain, as the optimal full

CSIT-based (channel state information at transmitter) precoding

scheme, in the large number of users

for more practically relevant (low to moderate)

RBF yields degraded performance. In this work, we investigate

solutions to this problem. We introduce a two-stage framework

that decouples the scheduling and beamforming problems. In our

scenario, RBF is exploited to identify good, spatially separable,

users in a first stage. In the second stage, the initial random

beams are refined based on the available feedback to offer

improved performance toward the selected users. Specifically, we

propose beam power control techniques that do not change the

direction of the second-stage beams, offering feedback reduction

and performance tradeoffs. The common feature of these schemes

is to restore robustness of RBF with respect to sparse network

settings (low

Systèmes de Communication
Eurecom Ref:
© 2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

PERMALINK : https://www.eurecom.fr/publication/2821