A-BLAST: a novel approach to adaptive layered space-time processing
Proceedings of the 2006 international conference on Wireless communications and mobile computing
Optimal constellations for the low-SNR noncoherent MIMO block Rayleigh-fading channel
IEEE Transactions on Information Theory
Low-SNR capacity of noncoherent fading channels
IEEE Transactions on Information Theory
Analysis of 1-bit output noncoherent fading channels in the low SNR regime
ISIT'09 Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 2
Switched-mode BLAST technique for MIMO communications
ICACT'09 Proceedings of the 11th international conference on Advanced Communication Technology - Volume 3
Noncoherent MIMO communication: Grassmannian constellations and efficient detection
IEEE Transactions on Information Theory
Low SNR capacity of double-scattering MIMO channels with transmitter channel knowledge
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
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Wireless channels with multiple transmit/receive antennas are known to provide a high spectral efficiency both when the channel is known to the receiver, and when the channel is not known to the receiver if the signal-to-noise ratio (SNR) is high. Here we analyze such systems at low SNR, which may find application in sensor networks and other low-power devices. The key point is that, since channel estimates are not reliable, it is often not reasonable to assume that the channel is known at the receiver at low SNR. In this unknown channel case, we show that for sensible input distributions, in particular all practical modulation schemes, the capacity is asymptotically quadratic in the SNR, ρ, and thus much less than the known channel case where it exhibits a linear growth in ρ. We show that under various signaling constraints, e.g., Gaussian modulation, unitary space-time modulation, and peak constraints, that mutual information is maximized by using a single transmit antenna. We also show that at low SNR, sending training symbols leads to a rate reduction in proportion to the fraction of training duration time so that it is best not to perform training. Furthermore, we show that the per-channel use mutual information is linear in both the number of receive antennas and the channel coherence interval.