114 research outputs found
Location Spoofing Detection for VANETs by a Single Base Station in Rician Fading Channels
In this work we examine the performance of a Location Spoofing Detection
System (LSDS) for vehicular networks in the realistic setting of Rician fading
channels. In the LSDS, an authorized Base Station (BS) equipped with multiple
antennas utilizes channel observations to identify a malicious vehicle, also
equipped with multiple antennas, that is spoofing its location. After deriving
the optimal transmit power and the optimal directional beamformer of a
potentially malicious vehicle, robust theoretical analysis and detailed
simulations are conducted in order to determine the impact of key system
parameters on the LSDS performance. Our analysis shows how LSDS performance
increases as the Rician K-factor of the channel between the BS and legitimate
vehicles increases, or as the number of antennas at the BS or legitimate
vehicle increases. We also obtain the counter-intuitive result that the
malicious vehicle's optimal number of antennas conditioned on its optimal
directional beamformer is equal to the legitimate vehicle's number of antennas.
The results we provide here are important for the verification of location
information reported in IEEE 1609.2 safety messages.Comment: 6 pages, 5 figures, Added further clarification on constraints
imposed on the detection minimization strategy. Minor typos fixe
Optimal Information-Theoretic Wireless Location Verification
We develop a new Location Verification System (LVS) focussed on network-based
Intelligent Transport Systems and vehicular ad hoc networks. The algorithm we
develop is based on an information-theoretic framework which uses the received
signal strength (RSS) from a network of base-stations and the claimed position.
Based on this information we derive the optimal decision regarding the
verification of the user's location. Our algorithm is optimal in the sense of
maximizing the mutual information between its input and output data. Our
approach is based on the practical scenario in which a non-colluding malicious
user some distance from a highway optimally boosts his transmit power in an
attempt to fool the LVS that he is on the highway. We develop a practical
threat model for this attack scenario, and investigate in detail the
performance of the LVS in terms of its input/output mutual information. We show
how our LVS decision rule can be implemented straightforwardly with a
performance that delivers near-optimality under realistic threat conditions,
with information-theoretic optimality approached as the malicious user moves
further from the highway. The practical advantages our new
information-theoretic scheme delivers relative to more traditional Bayesian
verification frameworks are discussed.Comment: Corrected typos and introduced new threat model
An Information Theoretic Location Verification System for Wireless Networks
As location-based applications become ubiquitous in emerging wireless
networks, Location Verification Systems (LVS) are of growing importance. In
this paper we propose, for the first time, a rigorous information-theoretic
framework for an LVS. The theoretical framework we develop illustrates how the
threshold used in the detection of a spoofed location can be optimized in terms
of the mutual information between the input and output data of the LVS. In
order to verify the legitimacy of our analytical framework we have carried out
detailed numerical simulations. Our simulations mimic the practical scenario
where a system deployed using our framework must make a binary Yes/No
"malicious decision" to each snapshot of the signal strength values obtained by
base stations. The comparison between simulation and analysis shows excellent
agreement. Our optimized LVS framework provides a defence against location
spoofing attacks in emerging wireless networks such as those envisioned for
Intelligent Transport Systems, where verification of location information is of
paramount importance
Bayesian Spatial Field Reconstruction with Unknown Distortions in Sensor Networks
Spatial regression of random fields based on potentially biased sensing
information is proposed in this paper. One major concern in such applications
is that since it is not known a-priori what the accuracy of the collected data
from each sensor is, the performance can be negatively affected if the
collected information is not fused appropriately. For example, the data
collector may measure the phenomenon inappropriately, or alternatively, the
sensors could be out of calibration, thus introducing random gain and bias to
the measurement process. Such readings would be systematically distorted,
leading to incorrect estimation of the spatial field. To combat this
detrimental effect, we develop a robust version of the spatial field model
based on a mixture of Gaussian process experts. We then develop two different
approaches for Bayesian spatial field reconstruction: the first algorithm is
the Spatial Best Linear Unbiased Estimator (S-BLUE), in which one considers the
quadratic loss function and restricts the estimator to the linear family of
transformations; the second algorithm is based on empirical Bayes, which
utilises a two-stage estimation procedure to produce accurate predictive
inference in the presence of "misbehaving" sensors. In addition, we develop the
distributed version of these two approaches to drastically improve the
computational efficiency in large-scale settings. We present extensive
simulation results using both synthetic datasets and semi-synthetic datasets
with real temperature measurements and simulated distortions to draw useful
conclusions regarding the performance of each of the algorithms
Bayesian Symbol Detection in Wireless Relay Networks via Likelihood-Free Inference
This paper presents a general stochastic model developed for a class of
cooperative wireless relay networks, in which imperfect knowledge of the
channel state information at the destination node is assumed. The framework
incorporates multiple relay nodes operating under general known non-linear
processing functions. When a non-linear relay function is considered, the
likelihood function is generally intractable resulting in the maximum
likelihood and the maximum a posteriori detectors not admitting closed form
solutions. We illustrate our methodology to overcome this intractability under
the example of a popular optimal non-linear relay function choice and
demonstrate how our algorithms are capable of solving the previously
intractable detection problem. Overcoming this intractability involves
development of specialised Bayesian models. We develop three novel algorithms
to perform detection for this Bayesian model, these include a Markov chain
Monte Carlo Approximate Bayesian Computation (MCMC-ABC) approach; an Auxiliary
Variable MCMC (MCMC-AV) approach; and a Suboptimal Exhaustive Search Zero
Forcing (SES-ZF) approach. Finally, numerical examples comparing the symbol
error rate (SER) performance versus signal to noise ratio (SNR) of the three
detection algorithms are studied in simulated examples
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