934 research outputs found
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
Multiple Access Channel with States Known Noncausally at One Encoder and Only Strictly Causally at the Other Encoder
We consider a two-user state-dependent multiaccess channel in which the
states of the channel are known non-causally to one of the encoders and only
strictly causally to the other encoder. Both encoders transmit a common message
and, in addition, the encoder that knows the states non-causally transmits an
individual message. We study the capacity region of this communication model.
In the discrete memoryless case, we establish inner and outer bounds on the
capacity region. Although the encoder that sends both messages knows the states
fully, we show that the strictly causal knowledge of these states at the other
encoder can be beneficial for this encoder, and in general enlarges the
capacity region. Furthermore, we find an explicit characterization of the
capacity in the case in which the two encoders transmit only the common
message. In the Gaussian case, we characterize the capacity region for the
model with individual message as well. Our converse proof in this case shows
that, for this model, strictly causal knowledge of the state at one of the
encoders does not increase capacity if the other is informed non-causally, a
result which sheds more light on the utility of conveying a compressed version
of the state to the decoder in recent results by Lapidoth and Steinberg on a
multiacess model with only strictly causal state at both encoders and
independent messages.Comment: 5 pages, to appear in the 2011 IEEE International Symposium on
Information Theor
Degraded Broadcast Channel with Side Information, Confidential Messages and Noiseless Feedback
In this paper, first, we investigate the model of degraded broadcast channel
with side information and confidential messages. This work is from Steinberg's
work on the degraded broadcast channel with causal and noncausal side
information, and Csiszr-K\"{o}rner's work on broadcast channel with
confidential messages. Inner and outer bounds on the capacity-equivocation
regions are provided for the noncausal and causal cases. Superposition coding
and double-binning technique are used in the corresponding achievability
proofs.
Then, we investigate the degraded broadcast channel with side information,
confidential messages and noiseless feedback. The noiseless feedback is from
the non-degraded receiver to the channel encoder. Inner and outer bounds on the
capacity-equivocation region are provided for the noncausal case, and the
capacity-equivocation region is determined for the causal case. Compared with
the model without feedback, we find that the noiseless feedback helps to
enlarge the inner bounds for both causal and noncausal cases. In the
achievability proof of the feedback model, the noiseless feedback is used as a
secret key shared by the non-degraded receiver and the transmitter, and
therefore, the code construction for the feedback model is a combination of
superposition coding, Gel'fand-Pinsker's binning, block Markov coding and
Ahlswede-Cai's secret key on the feedback system.Comment: Part of this paper has been accepted by ISIT2012, and this paper is
submitted to IEEE Transactions on Information Theor
Quantum Channels with Memory
We present a general model for quantum channels with memory, and show that it
is sufficiently general to encompass all causal automata: any quantum process
in which outputs up to some time t do not depend on inputs at times t' > t can
be decomposed into a concatenated memory channel. We then examine and present
different physical setups in which channels with memory may be operated for the
transfer of (private) classical and quantum information. These include setups
in which either the receiver or a malicious third party have control of the
initializing memory. We introduce classical and quantum channel capacities for
these settings, and give several examples to show that they may or may not
coincide. Entropic upper bounds on the various channel capacities are given.
For forgetful quantum channels, in which the effect of the initializing memory
dies out as time increases, coding theorems are presented to show that these
bounds may be saturated. Forgetful quantum channels are shown to be open and
dense in the set of quantum memory channels.Comment: 21 pages with 5 EPS figures. V2: Presentation clarified, references
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State-Dependent Relay Channel with Private Messages with Partial Causal and Non-Causal Channel State Information
In this paper, we introduce a discrete memoryless State-Dependent Relay
Channel with Private Messages (SD-RCPM) as a generalization of the
state-dependent relay channel. We investigate two main cases: SD-RCPM with
non-causal Channel State Information (CSI), and SD-RCPM with causal CSI. In
each case, it is assumed that partial CSI is available at the source and relay.
For non-causal case, we establish an achievable rate region using
Gel'fand-Pinsker type coding scheme at the nodes informed of CSI, and
Compress-and-Forward (CF) scheme at the relay. Using Shannon's strategy and CF
scheme, an achievable rate region for causal case is obtained. As an example,
the Gaussian version of SD-RCPM is considered, and an achievable rate region
for Gaussian SD-RCPM with non-causal perfect CSI only at the source, is
derived. Providing numerical examples, we illustrate the comparison between
achievable rate regions derived using CF and Decode-and-Forward (DF) schemes.Comment: 5 pages, 2 figures, to be presented at the IEEE International
Symposium on Information Theory (ISIT 2010), Austin, Texas, June 201
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