21 research outputs found
Capacity and Power Scaling Laws for Finite Antenna MIMO Amplify-and-Forward Relay Networks
In this paper, we present a novel framework that can be used to study the
capacity and power scaling properties of linear multiple-input multiple-output
(MIMO) antenna amplify-and-forward (AF) relay networks. In
particular, we model these networks as random dynamical systems (RDS) and
calculate their Lyapunov exponents. Our analysis can be applied to systems
with any per-hop channel fading distribution, although in this contribution we
focus on Rayleigh fading. Our main results are twofold: 1) the total transmit
power at the th node will follow a deterministic trajectory through the
network governed by the network's maximum Lyapunov exponent, 2) the capacity of
the th eigenchannel at the th node will follow a deterministic trajectory
through the network governed by the network's th Lyapunov exponent. Before
concluding, we concentrate on some applications of our results. In particular,
we show how the Lyapunov exponents are intimately related to the rate at which
the eigenchannel capacities diverge from each other, and how this relates to
the amplification strategy and number of antennas at each relay. We also use
them to determine the extra cost in power associated with each extra
multiplexed data stream.Comment: 16 pages, 9 figures. Accepted for publication in IEEE Transactions on
Information Theor
Secure communication over fully quantum Gel'fand-Pinsker wiretap channel
In this work we study the problem of secure communication over a fully
quantum Gel'fand-Pinsker channel. The best known achievability rate for this
channel model in the classical case was proven by Goldfeld, Cuff and Permuter
in [Goldfeld, Cuff, Permuter, 2016]. We generalize the result of [Goldfeld,
Cuff, Permuter, 2016]. One key feature of the results obtained in this work is
that all the bounds obtained are in terms of error exponent. We obtain our
achievability result via the technique of simultaneous pinching. This in turn
allows us to show the existence of a simultaneous decoder. Further, to obtain
our encoding technique and to prove the security feature of our coding scheme
we prove a bivariate classical-quantum channel resolvability lemma and a
conditional classical-quantum channel resolvability lemma. As a by product of
the achievability result obtained in this work, we also obtain an achievable
rate for a fully quantum Gel'fand-Pinsker channel in the absence of Eve. The
form of this achievable rate matches with its classical counterpart. The
Gel'fand-Pinsker channel model had earlier only been studied for the
classical-quantum case and in the case where Alice (the sender) and Bob (the
receiver) have shared entanglement between them.Comment: version 2, 1 figure, 26 pages, added some extra proof and corrected
few typo
A hypothesis testing approach for communication over entanglement assisted compound quantum channel
We study the problem of communication over a compound quantum channel in the
presence of entanglement. Classically such channels are modeled as a collection
of conditional probability distributions wherein neither the sender nor the
receiver is aware of the channel being used for transmission, except for the
fact that it belongs to this collection. We provide near optimal achievability
and converse bounds for this problem in the one-shot quantum setting in terms
of quantum hypothesis testing divergence. We also consider the case of informed
sender, showing a one-shot achievability result that converges appropriately in
the asymptotic and i.i.d. setting. Our achievability proof is similar in spirit
to its classical counterpart. To arrive at our result, we use the technique of
position-based decoding along with a new approach for constructing a union of
two projectors, which can be of independent interest. We give another
application of the union of projectors to the problem of testing composite
quantum hypotheses.Comment: 21 pages, version 3. Added an application to the composite quantum
hypothesis testing. Expanded introductio