IEEE Transactions on Communications,vol. 55, no. 5, pp. 1020-1032, May 2007.
A novel multiuser scheduling and feedback strategy
for the multiple-input multiple-output (MIMO) downlink is proposed
in this paper. It achieves multiuser diversity gain without
substantial feedback requirements. The proposed strategy uses
per-antenna scheduling at the base station, which maps each
transmit antenna at the base station (equivalently, a spatial
channel) to a user. Each user has a number of receive antennas
that is greater than or equal to the number of transmit antennas at
the base station. Zero-forcing receivers are deployed by each user
to decode the transmitted data streams. In this system, the base
station requires usersŐ channel quality on each spatial channel
for scheduling. An opportunistic feedback protocol is proposed
to reduce the feedback requirements. The proposed protocol
uses a contention channel that consists of a fixed number of
feedback minislots to convey channel state information. Feedback
control parameters including the channel quality threshold and
the random access feedback probability are jointly adjusted to
maximize the average throughput performance of this system.
Multiple receive antennas at the base station are used on the
feedback channel to allow decoding multiple feedback messages
sent simultaneously by different users. This further reduces the
bandwidth of the feedback channel. Iterative search algorithms
are proposed to solve the optimization for selection of these parameters
under both scenarios that the cumulative distribution
functions of users are known or unknown to the base station.
This paper is available in IEEE Xplore format.