Smooth beamforming for OFDM

This paper investigates the combination of beamforming and channel state information (CSI) smoothing for OFDM. While both can offer significant performance gains, care must be taken when using both of them at the same time. Two different sets of beamforming weights can produce the same beamforming g...

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Bibliographic Details
Published in:IEEE transactions on wireless communications 2009-03, Vol.8 (3), p.1133-1138
Main Authors: Sandell, M., Ponnampalam, V.
Format: Article
Language:English
Subjects:
Applied sciences
Array signal processing
Beamforming
channel estimation
Channel state information
Detection, estimation, filtering, equalization, prediction
eigenvectors
Exact sciences and technology
Frequency domain analysis
Frequency estimation
Hardware
Information, signal and communications theory
MIMO
Multiplexing
OFDM
Performance gain
Signal and communications theory
Signal, noise
Smoothing methods
SVD
Systems, networks and services of telecommunications
Telecommunications
Telecommunications and information theory
Transmission and modulation (techniques and equipments)
Transmitters
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Summary:This paper investigates the combination of beamforming and channel state information (CSI) smoothing for OFDM. While both can offer significant performance gains, care must be taken when using both of them at the same time. Two different sets of beamforming weights can produce the same beamforming gains but be unsuitable for CSI smoothing due to sudden changes in the frequency domain. By using orthogonal iterations to compute the beamforming weights, it is shown that a smooth beamformer is produced which is suitable for CSI smoothing at the receiver. An additional benefit of this technique is that the beamforming weights are easy to compute by exploiting the frequency correlation of the channel. The performance is evaluated for an OFDM system based on the IEEE 802.11n draft standard for which the gains are quantified. We also present results obtained from a hardware test bed, which verify the performance of the proposed smooth beamforming technique.
ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2008.080312