986 research outputs found
Communication over an Arbitrarily Varying Channel under a State-Myopic Encoder
We study the problem of communication over a discrete arbitrarily varying
channel (AVC) when a noisy version of the state is known non-causally at the
encoder. The state is chosen by an adversary which knows the coding scheme. A
state-myopic encoder observes this state non-causally, though imperfectly,
through a noisy discrete memoryless channel (DMC). We first characterize the
capacity of this state-dependent channel when the encoder-decoder share
randomness unknown to the adversary, i.e., the randomized coding capacity.
Next, we show that when only the encoder is allowed to randomize, the capacity
remains unchanged when positive. Interesting and well-known special cases of
the state-myopic encoder model are also presented.Comment: 16 page
The benefit of a 1-bit jump-start, and the necessity of stochastic encoding, in jamming channels
We consider the problem of communicating a message in the presence of a
malicious jamming adversary (Calvin), who can erase an arbitrary set of up to
bits, out of transmitted bits . The capacity of such
a channel when Calvin is exactly causal, i.e. Calvin's decision of whether or
not to erase bit depends on his observations was
recently characterized to be . In this work we show two (perhaps)
surprising phenomena. Firstly, we demonstrate via a novel code construction
that if Calvin is delayed by even a single bit, i.e. Calvin's decision of
whether or not to erase bit depends only on (and
is independent of the "current bit" ) then the capacity increases to
when the encoder is allowed to be stochastic. Secondly, we show via a novel
jamming strategy for Calvin that, in the single-bit-delay setting, if the
encoding is deterministic (i.e. the transmitted codeword is a deterministic
function of the message ) then no rate asymptotically larger than is
possible with vanishing probability of error, hence stochastic encoding (using
private randomness at the encoder) is essential to achieve the capacity of
against a one-bit-delayed Calvin.Comment: 21 pages, 4 figures, extended draft of submission to ISIT 201
Oblivious channels
Let C = {x_1,...,x_N} \subset {0,1}^n be an [n,N] binary error correcting
code (not necessarily linear). Let e \in {0,1}^n be an error vector. A codeword
x in C is said to be "disturbed" by the error e if the closest codeword to x +
e is no longer x. Let A_e be the subset of codewords in C that are disturbed by
e. In this work we study the size of A_e in random codes C (i.e. codes in which
each codeword x_i is chosen uniformly and independently at random from
{0,1}^n). Using recent results of Vu [Random Structures and Algorithms 20(3)]
on the concentration of non-Lipschitz functions, we show that |A_e| is strongly
concentrated for a wide range of values of N and ||e||.
We apply this result in the study of communication channels we refer to as
"oblivious". Roughly speaking, a channel W(y|x) is said to be oblivious if the
error distribution imposed by the channel is independent of the transmitted
codeword x. For example, the well studied Binary Symmetric Channel is an
oblivious channel.
In this work, we define oblivious and partially oblivious channels and
present lower bounds on their capacity. The oblivious channels we define have
connections to Arbitrarily Varying Channels with state constraints.Comment: Submitted to the IEEE International Symposium on Information Theory
(ISIT) 200
Secret Message Transmission over Quantum Channels under Adversarial Quantum Noise: Secrecy Capacity and Super-Activation
We determine the secrecy capacities of AVQCs (arbitrarily varying quantum
channels). Both secrecy capacity with average error probability and with
maximal error probability are derived. Both derivations are based on one common
code construction. The code we construct fulfills a stringent secrecy
requirement, which is called the strong code concept. We determine when the
secrecy capacity is a continuous function of the system parameters and
completely characterize its discontinuity points both for average error
criterion and for maximal error criterion. Furthermore, we prove the phenomenon
"super-activation" for secrecy capacities of AVQCs, i.e., two quantum channels
both with zero secrecy capacity, which, if used together, allow secure
transmission with positive capacity. We also discuss the relations between the
entanglement distillation capacity, the entanglement generating capacity, and
the strong subspace transmission capacity for AVQCs.Comment: arXiv admin note: text overlap with arXiv:1702.0348
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
The Arbitrarily Varying Relay Channel
We study the arbitrarily varying relay channel, and establish the cutset
bound and partial decode-forward bound on the random code capacity. We further
determine the random code capacity for special cases. Then, we consider
conditions under which the deterministic code capacity is determined as well.Comment: arXiv admin note: text overlap with arXiv:1701.0334
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