Vahid Dehghanian

GNSS spoofing detection in handheld receivers based on signal spatial correlation

Spoofing and jamming in the form of transmitting counterfeit location information and denying services are an emerging threat to GNSS receivers. In general, spoofing is a deliberate attack that aims to coerce GNSS receivers into generating false navigation solutions. The spoofing attack is potentially more hazardous than jamming since the target receiver is not aware of this threat and it is still providing position/navigation solutions which seem to be reliable. One major limitation of spoofers is that they are required to transmit several highly correlated GNSS signals simultaneously often from a single source in order to present a truthful navigation solution to the receiver. Different GNSS signals sourced from a single transmitter have essentially the same spatial signature, which as shown in this paper, can be utilized to discriminate the spoofing signals. In this paper a moving antenna is investigated to discriminate between the spatial signatures of the authentic and the spoofing signals based on monitoring the amplitude and Doppler correlation of the visible satellite signals. The effectiveness of this detection method is studied and verified based on a set of experiments.

A NEW INTERPOLATION TECHNIQUE FOR THE RECONSTRUCTION OF UNIFORMLY SPACED SAMPLES FROM NON-UNIFORMLY SPACED ONES IN PLANE-RECTANGULAR NEAR-FIELD ANTENNA MEASUREMENTS

A novel fast and accurate interpolation technique for recovering the uniformly distributed samples from the irregularly spaced samples, collected non-uniformly due to the probe position error in planar near-field antenna measurements, is presented. The technique employs Yen’s interpolator and tries to make it as practical as possible for the use in near-field antenna measurements. A comprehensive simulation capability is developed and through out the simulations the speed and precision of this accurate and timely efficient interpolation technique is compared with some other techniques which are also based on Yen’s interpolators. The results well demonstrate the advantages of our technique we termed “The Cross-Rail Technique”. 48 Dehghanian, Okhovvat, and Hakkak

Effectiveness of GNSS Spoofing Countermeasure Based on Receiver CNR Measurements

A perceived emerging threat to GNSS receivers is posed by a spoofing transmitter that emulates authentic signals but with randomized code phase and Doppler over a small range. Such spoofing signals can result in large navigational solution errors that are passed onto the unsuspecting user with potentially dire consequences. In this paper, a simple and readily implementable processing rule based on CNR estimates of the correlation peaks of the despread GNSS signals is developed expressly for reducing the effectiveness of such a spoofer threat. Consequently, a comprehensive statistical analysis is given to evaluate the effectiveness of the proposed technique in various LOS and NLOS environments. It is demonstrated that the proposed receiver processing is highly effective in both line-of-sight and multipath propagation conditions.

GNSS Spoofing Detection Based on Signal Power Measurements: Statistical Analysis

A threat to GNSS receivers is posed by a spoofing transmitter that emulates authentic signals but with randomized code phase and Doppler values over a small range. Such spoofing signals can result in large navigational solution errors that are passed onto the unsuspecting user with potentially dire consequences. An effective spoofing detection technique is developed in this paper, based on signal power measurements and that can be readily applied to present consumer grade GNSS receivers with minimal firmware changes. An extensive statistical analysis is carried out based on formulating a multihypothesis detection problem. Expressions are developed to devise a set of thresholds required for signal detection and identification. The detection processing methods developed are further manipulated to exploit incidental antenna motion arising from user interaction with a GNSS handheld receiver to further enhance the detection performance of the proposed algorithm. The statistical analysis supports the effectiveness of the proposed spoofing detection technique under various multipath conditions.

Combined Spatial-Polarization Correlation Function for Indoor Multipath Environments

The combined spatial-polarization correlation formulation for a multipath environment based on the uniform sphere of scatters model is developed. The closed-form expressions developed are useful for quantifying the potential diversity gain in antenna diversity systems. An extensive set of measurements were carried out at 1947.5 MHz to verify the theoretical results. The proposed model can be utilized for characterizing spatial and polarization diversity systems for indoor multipath environments.

Merger of polarization and spatial diversity by moving a pair of orthogonally polarized dipoles

Size and cost considerations of handheld terminals limit the use of antenna array for combating multipath fading in these applications. Recently, a synthetic array based on moving a single antenna was proposed for handheld terminals. This technique however fails to provide enough diversity gain when the channel is spatially correlated. A combination technique based on merging polarization and spatial diversity and motions of a crossed dipole is proposed here. The diversity performance of the crossed dipole synthetic array (XSA) is then compared to that of a single dipole synthetic array. A closed form expression is also derived for calculating the cumulative distribution function of summation of correlated central chi-squared random variables with four degrees of freedom which arises in the XSA performance analysis. Finally, the proposed technique is put into test through an extensive set of measurements.

Diversity Gain through Antenna Blocking

As part of the typical usage mode, interaction between a handheld receiver antenna and the operators RF absorbing body and nearby objects is known to generate variability in antenna radiation characteristics through blocking and pattern changes. It is counterintuitive that random variations in blocking can result in diversity gain of practical applicability. This diversity gain is quantified from a theoretical and experimental perspective. Measurements carried out at 1947.5 MHz verify the theoretical predictions, and a diversity gain of 3.1 dB was measured through antenna blocking and based on the utilized measurement setup. The diversity gain can be exploited to enhance signal detectability of handheld receivers based on a single antenna in indoor multipath environments.

Dual-polarized synthetic array for indoor GNSS handheld applications

Size and cost considerations of handheld terminals limit the use of antenna array for combating multipath fading in these applications. Recently, a synthetic array based on moving a single antenna was proposed for handheld terminals. This technique however fails to provide enough diversity gain when the channel is spatially correlated. A combination technique based on merging polarization and spatial diversities is proposed herein. The diversity performance of the dual-polarized RHCP/LHCP antennas in the synthetic array mode is then compared to that of a single RHCP synthetic array case for GNSS applications. Finally, the proposed technique is put into test through an extensive set of measurements.

RSS-INS integration for cooperative indoor positioning

Location estimation based on received signal strength (RSS) is an increasingly popular method of low-cost positioning. However, the low accuracy afforded by RSS centric systems dramatically limits suitable applications. Herein we discuss a positioning system utilizing cooperative strategies and integration of RSS observables with inertial navigation system (INS) sensors such as those commonly found in mobile devices, e.g. smart phones, tablets, etc. We analyze the theoretical bounds of the system using the Bayesian Cramer-Rao bound (BCRB). Simulation results and theoretical analysis illustrate that significant improvement in positional accuracy over typical RSS methods can be achieved.

Fusion of security camera and RSS fingerprinting for indoor multi-person tracking

In this paper the fusion of data from a network of security cameras and RSS fingerprint observations are combined to facilitate the simultaneous tracking of multiple persons inside indoor environments. An objective of the developed algorithm is to utilize existing building infrastructure namely the networks of security cameras and WiFi access points. Additionally minimal initial and maintenance calibration is required as crowdsourcing of the fingerprint mapping and self-calibrating camera processing is an integral component of the algorithm. Experimental results are given that demonstrate the accuracy, robustness and adaptability of the developed tracking algorithm.