multiple-input multiple-output (MIMO) non-coherent fading channels

with memory. We derive an upper bound on the feedback capacity of

regular fading channels, which is shown to coincide with a

previously known upper bound on the capacity without feedback.

Hence, it is concluded that whereas feedback does in general

increase capacity, this increase is relatively small in the sense

that the same upper bound holds for both scenarios. From this bound

we derive an upper bound on the MIMO fading number in the presence

of feedback and show that in the single-input single-output (SISO)

case this bound is tight,

changed by feedback.

Next, we derive an upper bound on the feedback capacity of

spatially independent MIMO Gaussian fading channels. From this bound

we derive a new upper bound on the corresponding fading number and

show that in the multiple-input single-output (MISO) case this bound

is tight.

Finally, in the case of a non-regular SISO Gaussian fading process

we show that feedback does not increase the pre-log,

the ratio of the capacity to the logarithm of the signal-to-noise

ratio log SNR is not changed in the limit when the SNR tends

to infinity.

-||- _|_ _|_ / __|__ Stefan M. Moser

[-] --__|__ /__\ /__ Senior Researcher & Lecturer, ETH Zurich, Switzerland

_|_ -- --|- _ / / Adj. Professor, National Chiao Tung University (NCTU), Taiwan

/ \ [] \| |_| / \/ Web: http://moser-isi.ethz.ch/

Last modified: Wed May 10 13:01:03 2006