Ahmed Medra and Timothy N. Davidson.
Incremental Grassmannian feedback schemes for multi-user MIMO
systems. IEEE Transactions on Signal Processing,
63(5):1130-1143, 1 March 2015.
Abstract
The communication of side information forms a
key component of several effective strategies for transmitter
adaptation to slowly fading channels. When the relevant side
information is a subspace, the feedback scheme can be viewed as a
lossy source compression scheme on the Grassmannian manifold.
Memoryless vector quantization on each fading block is a viable
compression scheme, but it neglects any temporal correlation
between the blocks. In this paper, we propose an incremental
approach to Grassmannian quantization that takes advantage of
temporal correlation. The approach leverages existing codebooks
for memoryless quantization schemes and employs a quantized
form of geodesic interpolation.
Two schemes that implement the
principles of the proposed approach are presented. In the
first
scheme, the choice of the step size in the incremental update is
adapted to a
first-order GaussMarkov model for the channel,
which enables the use of higher resolution codebooks. In the
second scheme, a single bit is allocated to the step size, which en-
ables adaptation of the step size to the channel realization rather
than the channel statistics. This
provides substantial robustness
against mismatches in the model for the temporal correlation.
A distinguishing feature of the proposed approach is that the
direction of the geodesic interpolation is specified implicitly using
a point in a conventional codebook. As a result, the approach has
an inherent ability to recover autonomously from errors in the
feedback path. Simulation results
demonstrate that these features
result in improved performance over some existing schemes in a
variety of channel environments.
A. Medra and T. N. Davidson. An incremental Grassmannian feedback scheme for linearly precoded spatial multiplexing MIMO systems. In Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing, pages 3053-3056, Kyoto, March 2012.