3,095 research outputs found
Generalized Degrees of Freedom of the Interference Channel with a Signal Cognitive Relay
We study the interference channel with a signal cognitive relay. A signal
cognitive relay knows the transmit signals (but not the messages) of the
sources non-causally, and tries to help them communicating with their
respective destinations. We derive upper bounds and provide achievable schemes
for this channel. These upper and lower bounds are shown to be tight from
generalized degrees of freedom point of view. As a result, a characterization
of the generalized degrees of freedom of the interference channel with a signal
cognitive relay is given.Comment: Results submitted to ISIT 2010, 19 pages, 3 figure
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
Approximate Sum-Capacity of K-user Cognitive Interference Channels with Cumulative Message Sharing
This paper considers the K user cognitive interference channel with one
primary and K-1 secondary/cognitive transmitters with a cumulative message
sharing structure, i.e cognitive transmitter knows non-causally
all messages of the users with index less than i. We propose a computable outer
bound valid for any memoryless channel. We first evaluate the sum-rate outer
bound for the high- SNR linear deterministic approximation of the Gaussian
noise channel. This is shown to be capacity for the 3-user channel with
arbitrary channel gains and the sum-capacity for the symmetric K-user channel.
Interestingly. for the K user channel having only the K th cognitive know all
the other messages is sufficient to achieve capacity i.e cognition at
transmitter 2 to K-1 is not needed. Next the sum capacity of the symmetric
Gaussian noise channel is characterized to within a constant additive and
multiplicative gap. The proposed achievable scheme for the additive gap is
based on Dirty paper coding and can be thought of as a MIMO-broadcast scheme
where only one encoding order is possible due to the message sharing structure.
As opposed to other multiuser interference channel models, a single scheme
suffices for both the weak and strong interference regimes. With this scheme
the generalized degrees of freedom (gDOF) is shown to be a function of K, in
contrast to the non cognitive case and the broadcast channel case.
Interestingly, it is show that as the number of users grows to infinity the
gDoF of the K-user cognitive interference channel with cumulative message
sharing tends to the gDoF of a broadcast channel with a K-antenna transmitter
and K single-antenna receivers. The analytical additive additive and
multiplicative gaps are a function of the number of users. Numerical
evaluations of inner and outer bounds show that the actual gap is less than the
analytical one.Comment: Journa
A Systematic Approach for Interference Alignment in CSIT-less Relay-Aided X-Networks
The degrees of freedom (DoF) of an X-network with M transmit and N receive
nodes utilizing interference alignment with the support of relays each
equipped with antennas operating in a half-duplex non-regenerative mode
is investigated. Conditions on the feasibility of interference alignment are
derived using a proper transmit strategy and a structured approach based on a
Kronecker-product representation. The advantages of this approach are twofold:
First, it extends existing results on the achievable DoF to generalized antenna
configurations. Second, it unifies the analysis for time-varying and constant
channels and provides valuable insights and interconnections between the two
channel models. It turns out that a DoF of \nicefrac{NM}{M+N-1} is feasible
whenever the sum of the
The Generalized Degrees of Freedom of the Interference Relay Channel with Strong Interference
The interference relay channel (IRC) under strong interference is considered.
A high-signal-to-noise ratio (SNR) generalized degrees of freedom (GDoF)
characterization of the capacity is obtained. To this end, a new GDoF upper
bound is derived based on a genie-aided approach. The achievability of the GDoF
is based on cooperative interference neutralization. It turns out that the
relay increases the GDoF even if the relay-destination link is weak. Moreover,
in contrast to the standard interference channel, the GDoF is not a
monotonically increasing function of the interference strength in the strong
interference regime.Comment: 8 pages, 4 figures, Allerton 201
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