T. Martelli

Parasitic Exploitation of Wi-Fi Signals for Indoor Radar Surveillance

In this paper, we examine the potentiality of passive coherent location (PCL) for indoor area monitoring. In particular, we show that Wi-Fi transmissions can be successfully exploited as waveforms of opportunity to perform moving target detection and localization based on the passive radar principle. Moreover, we investigate the advanced capability to obtain high-resolution cross-range profiles of the observed targets via inverse-synthetic-aperture-radar (ISAR) techniques. To these purposes, appropriate processing techniques are introduced to cope with the limitations resulting from the indoor applications such as the strong returns from the stationary scene and the high density of potential targets. The proposed system concept has been tested against both simulated and real data sets. The reported results clearly show that using few receiving channels connected to properly dislocated antennas allows an accurate target localization and tracking. In addition, reliable and stable profiles are obtained for the targets moving in the surveyed scene, which might fruitfully feed a classification stage. This contributes to the demonstration of the effective applicability of the passive radar concept for improving internal and external security of private/public premises.

Sliding extensive cancellation algorithm for disturbance removal in passive radar

In this paper an advanced version of the extensive cancellation algorithm (ECA) is proposed for robust disturbance cancellation and target detection in passive radar. Firstly some specific limitations of previous ECA versions are identified when dealing with a highly time-varying disturbance scenario in the presence of slowly moving targets. Specifically, the need to rapidly adapt the filter coefficients is shown to yield undesired effects on low Doppler target echoes, along with the expected partial cancellation. Therefore a sliding version of the ECA is presented which operates on partially overlapped signal batches. The proposed modification to the original ECA is shown to appropriately counteract the limitations above by taking advantage of a smooth estimate of the filter coefficients. An efficient implementation is also discussed to limit the corresponding computational load. The benefits of the proposed approach are demonstrated against real data sets accounting for quite different passive radar applications.

Multi-frequency target detection techniques for DVB-T based passive radar sensors

This paper investigates the possibility to improve target detection capability in a DVB-T- based passive radar sensor by jointly exploiting multiple digital television channels broadcast by the same transmitter of opportunity. Based on the remarkable results obtained by such a multi-frequency approach using other signals of opportunity (i.e., FM radio broadcast transmissions), we propose appropriate modifications to the previously devised signal processing techniques for them to be effective in the newly considered scenarios. The resulting processing schemes are extensively applied against experimental DVB-T-based passive radar data pertaining to different surveillance applications. The obtained results clearly show the effectiveness of the proposed multi-frequency approaches and demonstrate their suitability for application in the considered scenarios.

Enhanced WiFi-based passive ISAR for indoor and outdoor surveillance

In this paper we examine the potentiality of passive coherent location (PCL) exploiting WiFi transmissions for indoor and outdoor area monitoring. Particularly, we investigate the advanced capability to obtain high resolution cross-range profiles of the observed targets via Inverse Synthetic Aperture Radar (ISAR) techniques. To these purposes, appropriate processing techniques are introduced and their effectiveness is tested against real data sets concerning both human and man-made targets. The reported results clearly show that the proposed technique allows to effectively discriminate closely spaced human targets moving in a hall, whereas they could not be resolved by a conventional processing. In addition reliable and stable profiles are obtained for the man-made targets moving in the surveyed scene which might fruitfully feed a classification stage. This contributes to demonstrate the effective applicability of the passive radar concept for improving internal and external security of private/public premises.

WiFi-based PCL for monitoring private airfields

In recent years, a number of studies have looked at the use of passive coherent location (PCL) radar systems for short-range surveillance applications [1]–[8]. In such applications, the transmitters for mobile personal communication and network connection have been successfully exploited as illuminators of opportunity; these include the base stations of the global system for mobile communications, universal mobile telecommunications system, worldwide interoperability for microwave access (WiMAX), and long-term evolution (LTE).

Security enhancement in small private airports through active and passive radar sensors

In this paper we examine the potentialities of an innovative surveillance system composed by passive and active radar sensors for enhancing the security level in small airports and private runways. Specifically we report on the R&D activities carried on within the EU project SOS (Sensors system for detection and tracking Of dangerous materials in order to increase the airport Security in the indoor landside area). These activities included a number of experimental campaigns where both the single sensors and the multi-sensor system have been extensively tested. To this purpose, we employed the WiFi-based Passive Coherent Location (PCL) receiver developed at SAPIENZA University of Rome and a Ku-band frequency modulated continuous wave (FMCW) radar developed by MetaSensing. Both the considered sensors allow a radar coverage suitable for the extent of a small airport area, though providing target measurements with very different accuracies. The experimental results reported in this paper prove the effective applicability of the proposed approach for small airports surveillance.

Maritime surveillance via multi-frequency DVB-T based passive radar

In this paper, we consider the possibility to jointly exploit multiple frequency channels emitted by the same transmitter to improve target detection capability in a DVB-T based passive radar. In particular, appropriate multi-frequency techniques are presented for target detection to be effective in the considered application. The proposed approaches are validated and compared with reference to several experimental data for maritime surveillance applications. The reported results show that the considered multi-frequency techniques yield a significant enhancement in target detection performance with respect to the single frequency operation.

Quasi-Monostatic Versus Near Forward Scatter Geometry in WiFi-Based Passive Radar Sensors

In this paper, the comparison is investigated between quasi-monostatic and near forward scatter configurations for WiFi-based passive radar sensors. To this purpose, a barrier coverage application for vehicular targets is considered as a possible implementation of the conceived green sensor within surface transportation monitoring solutions. The performance of the two alternative sensor geometries are compared by means of theoretical and experimental analysis as well as based on considerations on the practical implementation. The reported results provide a realistic characterization of the performance of a bistatic radar sensor to be exploited in barrier coverage problems and give indications for the design of such a system. The specific demonstration with WiFi-based passive radar aims at extending the use of this emerging technology to perimeter monitoring applications for vehicular targets, exploiting the near forward scatter geometry.