Title :
On channel quantization and feedback strategies for multiuser MIMO-OFDM downlink systems
Author :
Trivellato, Matteo ; Tomasin, Stefano ; Benvenuto, Nevio
Author_Institution :
Reicom S.R.L., Padova, Italy
fDate :
9/1/2009 12:00:00 AM
Abstract :
We consider a multiuser MIMO-OFDM downlink system with single antenna mobile terminals (MTs) where channel state information at the base station is provided through limited uplink feedback (FB). In order to reduce the FB rate and signal processing complexity, the available bandwidth is divided into resource blocks (RBs) whose number of subcarriers reflects the coherence bandwidth of the channel. This approach is very common in the standardization of 4th generation wireless communication systems and justifies an independent channel quantization per RB. Within this framework the paper contains two main contributions. Firstly we provide joint conditions on the channel coherence bandwidth and the FB rate per RB that allow for a simpler quantization of the RB channel matrix (space-frequency) by a space vector, causing negligible performance loss in terms of system achievable throughput. This is accomplished after deriving a new metric for codebook design in RB channel quantization that exploits spatial and frequency correlation. As a second contribution we investigate the trade-off between accurate channel knowledge and frequency/multiuser diversity. It is seen that even for a moderate number of MTs in the network, concentrating all the available FB bits in characterizing only one RB provides a significant gain in system throughput over a more classical distributed approach and this result is validated both analytically and by simulations.
Keywords :
MIMO communication; OFDM modulation; feedback; mobile radio; multiuser channels; quantisation (signal); wireless channels; 4th generation wireless communication systems; RB channel matrix; antenna mobile terminals; channel bandwidth; channel quantization; channel state information; codebook design; feedback strategies; frequency diversity; independent channel quantization; multiuser MIMO-OFDM downlink systems; multiuser diversity; resource blocks; signal processing complexity; Antenna feeds; Bandwidth; Base stations; Channel state information; Downlink; Mobile antennas; Quantization; Signal processing; State feedback; Throughput; Multiuser MIMO, OFDM, limited feedback, quantization.;
Journal_Title :
Communications, IEEE Transactions on
DOI :
10.1109/TCOMM.2009.09.080098