Multiuser feedback design with multiple receive antennas

Abstract

In a frequency division duplex system with a base station equipped with multiple antennas, the base station relies on feedback of the channel state information of the users in order to perform user selection and transmit beamforming in the downlink. Nonetheless, it is usually assumed that the feedback link is noise-free, i.e. the base station has access to error-free feedback. In practice, however, the feedback link is the uplink of the system and is subject to fading, possible multiuser interference and noise. In this work, with a given amount of resources reserved for the feedback of all the users, we tackle the system feedback design considering feedback errors. We take into account that the base station can detect the feedback of several users simultaneously by employing receive beamforming. In addition, we propose to exploit multiuser diversity in the feedback link in order to minimize the feedback error probability. We also present an orthogonal pilot design which enables the base station to estimate the feedback (uplink) channels of the users.