10,929 research outputs found
Capacity Region of the Broadcast Channel with Two Deterministic Channel State Components
This paper establishes the capacity region of a class of broadcast channels
with random state in which each channel component is selected from two possible
functions and each receiver knows its state sequence. This channel model does
not fit into any class of broadcast channels for which the capacity region was
previously known and is useful in studying wireless communication channels when
the fading state is known only at the receivers. The capacity region is shown
to coincide with the UV outer bound and is achieved via Marton coding.Comment: 5 pages, 3 figures. Submitted to ISIT 201
Secrecy Capacity Region of Some Classes of Wiretap Broadcast Channels
This work investigates the secrecy capacity of the Wiretap Broadcast Channel
(WBC) with an external eavesdropper where a source wishes to communicate two
private messages over a Broadcast Channel (BC) while keeping them secret from
the eavesdropper. We derive a non-trivial outer bound on the secrecy capacity
region of this channel which, in absence of security constraints, reduces to
the best known outer bound to the capacity of the standard BC. An inner bound
is also derived which follows the behavior of both the best known inner bound
for the BC and the Wiretap Channel. These bounds are shown to be tight for the
deterministic BC with a general eavesdropper, the semi-deterministic BC with a
more-noisy eavesdropper and the Wiretap BC where users exhibit a less-noisiness
order between them. Finally, by rewriting our outer bound to encompass the
characteristics of parallel channels, we also derive the secrecy capacity
region of the product of two inversely less-noisy BCs with a more-noisy
eavesdropper. We illustrate our results by studying the impact of security
constraints on the capacity of the WBC with binary erasure (BEC) and binary
symmetric (BSC) components.Comment: 19 pages, 8 figures, To appear in IEEE Trans. on Information Theor
The Arbitrarily Varying Broadcast Channel with Degraded Message Sets with Causal Side Information at the Encoder
In this work, we study the arbitrarily varying broadcast channel (AVBC), when
state information is available at the transmitter in a causal manner. We
establish inner and outer bounds on both the random code capacity region and
the deterministic code capacity region with degraded message sets. The capacity
region is then determined for a class of channels satisfying a condition on the
mutual informations between the strategy variables and the channel outputs. As
an example, we consider the arbitrarily varying binary symmetric broadcast
channel with correlated noises. We show cases where the condition holds, hence
the capacity region is determined, and other cases where there is a gap between
the bounds.Comment: arXiv admin note: substantial text overlap with arXiv:1701.0334
Cooperation with an Untrusted Relay: A Secrecy Perspective
We consider the communication scenario where a source-destination pair wishes
to keep the information secret from a relay node despite wanting to enlist its
help. For this scenario, an interesting question is whether the relay node
should be deployed at all. That is, whether cooperation with an untrusted relay
node can ever be beneficial. We first provide an achievable secrecy rate for
the general untrusted relay channel, and proceed to investigate this question
for two types of relay networks with orthogonal components. For the first
model, there is an orthogonal link from the source to the relay. For the second
model, there is an orthogonal link from the relay to the destination. For the
first model, we find the equivocation capacity region and show that answer is
negative. In contrast, for the second model, we find that the answer is
positive. Specifically, we show by means of the achievable secrecy rate based
on compress-and-forward, that, by asking the untrusted relay node to relay
information, we can achieve a higher secrecy rate than just treating the relay
as an eavesdropper. For a special class of the second model, where the relay is
not interfering itself, we derive an upper bound for the secrecy rate using an
argument whose net effect is to separate the eavesdropper from the relay. The
merit of the new upper bound is demonstrated on two channels that belong to
this special class. The Gaussian case of the second model mentioned above
benefits from this approach in that the new upper bound improves the previously
known bounds. For the Cover-Kim deterministic relay channel, the new upper
bound finds the secrecy capacity when the source-destination link is not worse
than the source-relay link, by matching with the achievable rate we present.Comment: IEEE Transactions on Information Theory, submitted October 2008,
revised October 2009. This is the revised versio
On Cooperative Multiple Access Channels with Delayed CSI at Transmitters
We consider a cooperative two-user multiaccess channel in which the
transmission is controlled by a random state. Both encoders transmit a common
message and, one of the encoders also transmits an individual message. We study
the capacity region of this communication model for different degrees of
availability of the states at the encoders, causally or strictly causally. In
the case in which the states are revealed causally to both encoders but not to
the decoder we find an explicit characterization of the capacity region in the
discrete memoryless case. In the case in which the states are revealed only
strictly causally to both encoders, we establish inner and outer bounds on the
capacity region. The outer bound is non-trivial, and has a relatively simple
form. It has the advantage of incorporating only one auxiliary random variable.
We then introduce a class of cooperative multiaccess channels with states known
strictly causally at both encoders for which the inner and outer bounds agree;
and so we characterize the capacity region for this class. In this class of
channels, the state can be obtained as a deterministic function of the channel
inputs and output. We also study the model in which the states are revealed,
strictly causally, in an asymmetric manner, to only one encoder. Throughout the
paper, we discuss a number of examples; and compute the capacity region of some
of these examples. The results shed more light on the utility of delayed
channel state information for increasing the capacity region of state-dependent
cooperative multiaccess channels; and tie with recent progress in this
framework.Comment: 54 pages. To appear in IEEE Transactions on Information Theory. arXiv
admin note: substantial text overlap with arXiv:1201.327
Wiretap and Gelfand-Pinsker Channels Analogy and its Applications
An analogy framework between wiretap channels (WTCs) and state-dependent
point-to-point channels with non-causal encoder channel state information
(referred to as Gelfand-Pinker channels (GPCs)) is proposed. A good sequence of
stealth-wiretap codes is shown to induce a good sequence of codes for a
corresponding GPC. Consequently, the framework enables exploiting existing
results for GPCs to produce converse proofs for their wiretap analogs. The
analogy readily extends to multiuser broadcasting scenarios, encompassing
broadcast channels (BCs) with deterministic components, degradation ordering
between users, and BCs with cooperative receivers. Given a wiretap BC (WTBC)
with two receivers and one eavesdropper, an analogous Gelfand-Pinsker BC (GPBC)
is constructed by converting the eavesdropper's observation sequence into a
state sequence with an appropriate product distribution (induced by the
stealth-wiretap code for the WTBC), and non-causally revealing the states to
the encoder. The transition matrix of the state-dependent GPBC is extracted
from WTBC's transition law, with the eavesdropper's output playing the role of
the channel state. Past capacity results for the semi-deterministic (SD) GPBC
and the physically-degraded (PD) GPBC with an informed receiver are leveraged
to furnish analogy-based converse proofs for the analogous WTBC setups. This
characterizes the secrecy-capacity regions of the SD-WTBC and the PD-WTBC, in
which the stronger receiver also observes the eavesdropper's channel output.
These derivations exemplify how the wiretap-GP analogy enables translating
results on one problem into advances in the study of the other
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