275 research outputs found
Cooperative Binning for Semi-deterministic Channels with Non-causal State Information
The capacity of the semi-deterministic relay channel (SD-RC) with non-causal
channel state information (CSI) only at the encoder and decoder is
characterized. The capacity is achieved by a scheme based on
cooperative-bin-forward. This scheme allows cooperation between the transmitter
and the relay without the need to decode a part of the message by the relay.
The transmission is divided into blocks and each deterministic output of the
channel (observed by the relay) is mapped to a bin. The bin index is used by
the encoder and the relay to choose the cooperation codeword in the next
transmission block. In causal settings the cooperation is independent of the
state. In \emph{non-causal} settings dependency between the relay's
transmission and the state can increase the transmission rates. The encoder
implicitly conveys partial state information to the relay. In particular, it
uses the states of the next block and selects a cooperation codeword
accordingly and the relay transmission depends on the cooperation codeword and
therefore also on the states. We also consider the multiple access channel with
partial cribbing as a semi-deterministic channel. The capacity region of this
channel with non-causal CSI is achieved by the new scheme. Examining the result
in several cases, we introduce a new problem of a point-to-point (PTP) channel
where the state is provided to the transmitter by a state encoder.
Interestingly, even though the CSI is also available at the receiver, we
provide an example which shows that the capacity with non-causal CSI at the
state encoder is strictly larger than the capacity with causal CSI
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
Capacity of a Class of State-Dependent Orthogonal Relay Channels
The class of orthogonal relay channels in which the orthogonal channels
connecting the source terminal to the relay and the destination, and the relay
to the destination, depend on a state sequence, is considered. It is assumed
that the state sequence is fully known at the destination while it is not known
at the source or the relay. The capacity of this class of relay channels is
characterized, and shown to be achieved by the partial
decode-compress-and-forward (pDCF) scheme. Then the capacity of certain binary
and Gaussian state-dependent orthogonal relay channels are studied in detail,
and it is shown that the compress-and-forward (CF) and
partial-decode-and-forward (pDF) schemes are suboptimal in general. To the best
of our knowledge, this is the first single relay channel model for which the
capacity is achieved by pDCF, while pDF and CF schemes are both suboptimal.
Furthermore, it is shown that the capacity of the considered class of
state-dependent orthogonal relay channels is in general below the cut-set
bound. The conditions under which pDF or CF suffices to meet the cut-set bound,
and hence, achieve the capacity, are also derived.Comment: This paper has been accepted by IEEE Transactions on Information
Theor
Channels with Cooperation Links that May Be Absent
It is well known that cooperation between users in a communication network
can lead to significant performance gains. A common assumption in past works is
that all the users are aware of the resources available for cooperation, and
know exactly to what extent these resources can be used. Unfortunately, in many
modern communication networks the availability of cooperation links cannot be
guaranteed a priori, due to the dynamic nature of the network. In this work a
family of models is suggested where the cooperation links may or may not be
present. Coding schemes are devised that exploit the cooperation links if they
are present, and can still operate (although at reduced rates) if cooperation
is not possible.Comment: Accepted for publication in the IEEE transaction on Information
Theory, June 201
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