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S. Schwarz, R. W. Heath, M. Rupp:
"Single-user MIMO versus multi-user MIMO in distributed antenna systems with limited feedback";
EURASIP Journal on Advances in Signal Processing, 2013 (2013), 1; 20 pages.

This article investigates the performance of cellular networks employing distributed antennas in addition to the
central antennas of the base station. Distributed antennas are likely to be implemented using remote radio units,
which is enabled by a low latency and high bandwidth dedicated link to the base station. This facilitates coherent
transmission from potentially all available antennas at the same time. Such distributed antenna system (DAS) is an
effective way to deal with path loss and large-scale fading in cellular systems. DAS can apply precoding across
multiple transmission points to implement single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO)
transmission. The throughput performance of various SU-MIMO and MU-MIMO transmission strategies is investigated
in this article, employing a Long-Term evolution (LTE) standard compliant simulation framework. The previously
theoretically established cell-capacity improvement of MU-MIMO in comparison to SU-MIMO in DASs is confirmed
under the practical constraints imposed by the LTE standard, even under the assumption of imperfect channel state
information (CSI) at the base station. Because practical systems will use quantized feedback, the performance of
different CSI feedback algorithms for DASs is investigated. It is shown that significant gains in the CSI quantization
accuracy and in the throughput of especially MU-MIMO systems can be achieved with relatively simple quantization
codebook constructions that exploit the available temporal correlation and channel gain differences.

Distributed antenna systems, Remote radio units, Channel state information estimation, Limited feedback communication, Quantized feedback, Single-user MIMO, Multi-user MIMO, LTE

http://dx.doi.org/10.1186/1687-6180-2013-54