On Limits of Wireless Communications in a Fading Environment when UsingMultiple Antennas
Wireless Personal Communications: An International Journal
A Concise Guide to Complex Hadamard Matrices
Open Systems & Information Dynamics
Limited feedback unitary precoding for orthogonal space-time block codes
IEEE Transactions on Signal Processing
Precoding for Multiple Antenna Gaussian Broadcast Channels With Successive Zero-Forcing
IEEE Transactions on Signal Processing - Part II
Space Division Multiple Access With a Sum Feedback Rate Constraint
IEEE Transactions on Signal Processing - Part II
IEEE Transactions on Signal Processing
Multiple Antenna Broadcast Channels With Shape Feedback and Limited Feedback
IEEE Transactions on Signal Processing - Part I
Zero-forcing methods for downlink spatial multiplexing in multiuser MIMO channels
IEEE Transactions on Signal Processing
A Leakage-Based Precoding Scheme for Downlink Multi-User MIMO Channels
IEEE Transactions on Wireless Communications
Systematic design of unitary space-time constellations
IEEE Transactions on Information Theory
Multiple-antenna signal constellations for fading channels
IEEE Transactions on Information Theory
IEEE Transactions on Information Theory
IEEE Transactions on Information Theory
Bounds on packings of spheres in the Grassmann manifold
IEEE Transactions on Information Theory
On the achievable throughput of a multiantenna Gaussian broadcast channel
IEEE Transactions on Information Theory
On beamforming with finite rate feedback in multiple-antenna systems
IEEE Transactions on Information Theory
Grassmannian beamforming for multiple-input multiple-output wireless systems
IEEE Transactions on Information Theory
On the capacity of MIMO broadcast channels with partial side information
IEEE Transactions on Information Theory
Dirty-paper coding versus TDMA for MIMO Broadcast channels
IEEE Transactions on Information Theory
Limited feedback unitary precoding for spatial multiplexing systems
IEEE Transactions on Information Theory
Sphere-packing bounds in the Grassmann and Stiefel manifolds
IEEE Transactions on Information Theory
MIMO Broadcast Channels With Finite-Rate Feedback
IEEE Transactions on Information Theory
What is the value of limited feedback for MIMO channels?
IEEE Communications Magazine
An introduction to the multi-user MIMO downlink
IEEE Communications Magazine
Joint user pairing and precoding in MU-MIMO broadcast channel with limited feedback
IEEE Communications Letters
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Multiple-input multiple-output (MIMO) systems can be leveraged to increase capacity in fading channels. Especially in multiuser downlink communication systems, it has been shown that knowledge of channel state information at the transmitter (CSIT) is critical to leverage the capacity gain available from multiple antennas. When duplexing is performed using time division, CSIT can often be successfully obtained when channel reciprocity is available. CSIT acquisition, however, is much more difficult in frequency division duplexing. Sending feedback on the uplink has been shown to be a powerful technique to improve downlink performance in single user MIMO systems. The basic idea is to restrict the CSIT to a B bit codebook so that the mobiles can easily transmit these bits on the uplink. In this paper, we consider the multiuser downlink model with unitary precoding when there is a codebook consisting of 2B unitary matrices that the precoder is restricted to lie in. This codebook is designed offline and known to both the basestation and all users. Each user sends back signal-to-interference plus noise ratio (SINR) information along with binary feedback about the unitary precoder. Based on the CSIT received on the uplink, the basestation selects one of the unitary matrices in the codebook to maximize the sum-rate. For this set-up, we first analyze the sum-rate performance of the unitary precoding scheme. We then show that the codebook of unitary precoders represents a collection of points in a special kind of manifold and show how the achievable sum-rate performance relates to the minimum distance of the codebook points in this space. Finally, we present a framework for constructing the codebook to maximize this minimum distance. Monte Carlo simulation results are presented to show the sum-rate performance of the proposed codebook design.