93 research outputs found
State of the cognitive interference channel: a new unified inner bound
The capacity region of the interference channel in which one transmitter
non-causally knows the message of the other, termed the cognitive interference
channel, has remained open since its inception in 2005. A number of subtly
differing achievable rate regions and outer bounds have been derived, some of
which are tight under specific conditions. In this work we present a new
unified inner bound for the discrete memoryless cognitive interference channel.
We show explicitly how it encompasses all known discrete memoryless achievable
rate regions as special cases. The presented achievable region was recently
used in deriving the capacity region of the general deterministic cognitive
interference channel, and thus also the linear high-SNR deterministic
approximation of the Gaussian cognitive interference channel. The high-SNR
deterministic approximation was then used to obtain the capacity of the
Gaussian cognitive interference channel to within 1.87 bits.Comment: Presented at the 2010 International Zurich Seminar on Communications
- an 2nd updated version
Secure GDoF of the Z-channel with Finite Precision CSIT: How Robust are Structured Codes?
Under the assumption of perfect channel state information at the transmitters
(CSIT), it is known that structured codes offer significant advantages for
secure communication in an interference network, e.g., structured jamming
signals based on lattice codes may allow a receiver to decode the sum of the
jamming signal and the signal being jammed, even though they cannot be
separately resolved due to secrecy constraints, subtract the aggregate jammed
signal, and then proceed to decode desired codewords at lower power levels. To
what extent are such benefits of structured codes fundamentally limited by
uncertainty in CSIT? To answer this question, we explore what is perhaps the
simplest setting where the question presents itself -- a Z interference channel
with secure communication. Using sum-set inequalities based on Aligned Images
bounds we prove that the GDoF benefits of structured codes are lost completely
under finite precision CSIT. The secure GDoF region of the Z interference
channel is obtained as a byproduct of the analysis.Comment: 34 pages, 10 figure
Design and performance analysis of optical attocell networks
The exponentially increasing demand for high-speed wireless communications will no longer
be satisfied by the traditional radio frequency (RF) in the near future due to its limited spectrum
and overutilization. To resolve this imminent issue, industrial and research communities have
been looking into alternative technologies for communication. Among them, visible light communication
(VLC) has attracted much attention because it utilizes the unlicensed, free and safe
spectrum, whose bandwidth is thousand times larger than the entire RF spectrum. Moreover,
VLC can be integrated into existing lighting systems to offer a dual-purpose, cost-effective and
energy-efficient solution for next-generation small-cell networks (SCNs), giving birth to the
concept of optical attocell networks.
Most relevant works in the literature rely on system simulations to quantify the performance
of attocell networks, which suffer from high computational complexity and provide limited
insights about the network. Mathematical tools, on the other hand, are more tractable and
scalable and are shown to closely approximate practical systems. The presented work utilizes
stochastic geometry for downlink evaluation of optical attocell networks, where the co-channel
interference (CCI) surpasses noise and becomes the limiting factor of the link throughput. By
studying the moment generating function (MGF) of the aggregate interference, a theoretical
framework for modeling the distribution of signal-to-interference-plus-noise ratio (SINR) is
presented, which allows important performance metrics such as the coverage probability and
link throughput to be derived. Depending on the source of interference, CCI can be classified
into two categories: inter-cell interference (ICI) and intra-cell interference. In this work,
both types of interference are characterized, based on which effective interference mitigation
techniques such as the coordinated multipoint (CoMP), power-domain multiplexing and successive
interference cancellation (SIC) are devised. The proposed mathematical framework is
applicable to attocell networks with and without such interference mitigation techniques.
Compared to RF networks, optical attocell networks are inherently more secure in the physical
layer because visible light does not penetrate through opaque walls. This work analytically
quantifies the physical-layer security of attocell networks from an information-theoretic point of
view. Secrecy enhancement techniques such as AP cooperation and eavesdropper-free protected
zones are also discussed. It is shown that compared to AP cooperation, implementing secrecy
protected zones is more effective and it can contribute significantly to the network security
A Comprehensive Survey of Potential Game Approaches to Wireless Networks
Potential games form a class of non-cooperative games where unilateral
improvement dynamics are guaranteed to converge in many practical cases. The
potential game approach has been applied to a wide range of wireless network
problems, particularly to a variety of channel assignment problems. In this
paper, the properties of potential games are introduced, and games in wireless
networks that have been proven to be potential games are comprehensively
discussed.Comment: 44 pages, 6 figures, to appear in IEICE Transactions on
Communications, vol. E98-B, no. 9, Sept. 201
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