[Show abstract][Hide abstract] ABSTRACT: The broadcast nature of wireless communications imposes the risk of information leakage to adversarial users or unauthorized receivers. Therefore, information security between intended users remains a challenging issue. Most of the current physical layer security techniques exploit channel randomness as a common source between two legitimate nodes to extract a secret key. In this paper, we propose a new simple technique to generate the secret key. Specifically, we exploit the estimated channel to generate a secondary random process (SRP) that is common between the two legitimate nodes. We compare the estimated channel gain and phase to a preset threshold. The moving differences between the locations at which the estimated channel gain and phase exceed the threshold are the realization of our SRP. We simulate an orthogonal frequency division multiplexing (OFDM) system and show that our proposed technique provides a drastic improvement in the key bit mismatch rate (BMR) between the legitimate nodes when compared to the techniques that exploit the estimated channel gain or phase directly. In addition to that, the secret key generated through our technique is longer than that generated by conventional techniques.
[Show abstract][Hide abstract] ABSTRACT: The paper presents an innovative solution for the realization of wireless sensor networks suitable to characterize the microclimatic behavior in agriculture fields. The nodes are equipped with sensing units to measure several physical parameters. They are designed in order to minimize power consumption, being able to work for a whole season without any energy harvester. The network is implemented at two levels. Data from distributed sensing units are initially collected via a single-hop connection and then forwarded to the Internet gateway via a multi-hop transmission scheme. The two levels use interchangeable ISM frequencies, thanks to the design of dual band loop antennas. In this way, flexibility and scalability can be easily reached. The trial that is currently tested in Montepulciano, Italy, has initially evidences problems originated by package permeability to humidity and water. Once the issue has been solved, reliability has reached 99%.
[Show abstract][Hide abstract] ABSTRACT: The paper presents an automatic wireless sensor platform that allows precision soil investigations in order to verify punctual seasonal variations in soil water content. In this way, it is possible to keep the plants nourishment cycle under precise control, correlating it to temperature, humidity and rain variations. The sensing unit is constructed by means of couples of microwave radiators, and the water content percentage is evaluated thanks to a continuous measurement of the received power. The design procedure is carried out by identifying the most suitable solution, in terms of operational frequency, dimensions of radiators and their relative distance, balancing the decreased mismatching effect with the increased propagation attenuation caused by the presence of the water. Experiments carried out in collaboration with the Case Basse winery in Montalcino are presented and discussed.
[Show abstract][Hide abstract] ABSTRACT: In the context of physical layer security, a physical layer characteristic is
used as a common source of randomness to generate the secret key. Therefore an
accurate estimation of this characteristic is the core for reliable secret key
generation. Estimation of almost all the existing physical layer characteristic
suffer dramatically at low signal to noise (SNR) levels. In this paper, we
propose a novel secret key generation algorithm that is based on the estimated
angle of arrival (AoA) between the two legitimate nodes. Our algorithm has an
outstanding performance at very low SNR levels. Our algorithm can exploit
either the Azimuth AoA to generate the secret key or both the Azimuth and
Elevation angles to generate the secret key. Exploiting a second common source
of randomness adds an extra degree of freedom to the performance of our
algorithm. We compare the performance of our algorithm to the algorithm that
uses the most commonly used characteristics of the physical layer which are
channel amplitude and phase. We show that our algorithm has a very low bit
mismatch rate (BMR) at very low SNR when both channel amplitude and phase based
algorithm fail to achieve an acceptable BMR.
[Show abstract][Hide abstract] ABSTRACT: The 'Union of the Comoros' is a volcanic archipelago nation in the Indian Ocean, consisting of three islands. About half the population lives below the international poverty line of US$1.25 a day. The interiors of the islands vary from steep mountains to low hills with mostly damaged or unconstructed roads to interconnect the several islets. This situation represents an extraordinary field test: the geographical isolation from other Countries, among the islands and within the same island, the development level of the population and the lack of infrastructures can be efficiently mitigated if a high capacity ICT infrastructure is realized, in order to provide social services (distance learning, telemedicine, financial administration) to the population, together with the possibility to access basic information on the Internet. In this context, we have put into practice a wireless network based on the use of low cost components, optimized for the transportation of large amount of bandwidths (minimum measured throughput is 65 Mb/s). The infrastructure has been made available at no cost for the people, since an extremely small percentage of them can afford regular Internet subscriptions. The network provides interconnectivity among the islets and local Hot Spot facilities at the islet level, free of cost for the end users. The local population has been recruited during the design and installation phase, in order to develop sufficient know how that allows them to maintain and even extend the infrastructure after its completion. Accessibility is guaranteed over the whole Country. To this aim, technical tests have been made in order to verify the affordability and reliability of the solution in the medium and long terms. The project is now being used to vehicle public finance management among the multitude of islets of the islands, under the endorsement of the World Bank.
[Show abstract][Hide abstract] ABSTRACT: Within the paradigm of physical layer secrecy, typically a physical layer specific characteristic is used as key generator to guarantee information hiding from eavesdroppers. In this paper, we propose a novel secret key generation algorithm based on two reciprocal physical layer parameters; the channel measurements and the distances between the two communicating nodes. The two parameters are estimated experimentally using implementations of our algorithm on three FPGA-based WARP kits emulating the two communicating nodes and the eavesdrop-per. The parameters are used as common sources of randomness to generate the secret key. We evaluate the performance of our algorithm through extensive iterations. We compare the bit mismatch rate as well as the entropy of the generated secret key of our algorithm versus classical channel only and distance only based algorithms. Our results reveal that even in the worst case scenarios, our algorithm outperforms the two other algorithms and overcomes their vulnerabilities.
[Show abstract][Hide abstract] ABSTRACT: The paper illustrates an efficient wireless sensor network platform, suitable for application to assisted agriculture in (but not only in) developing Countries and remote regions. The platform has been conceived in order to minimize power consumption, during all the phases of data acquisition, sampling, and compression, with an efficient and performing communication protocol, with extended transmission range and radio coverage optimization. Sensor nodes have been provided with energy harvesting facilities, to avoid any need for direct power supply or battery replacement. The resulting nodes are consequently autonomous, easy to locate and relocate, and scalable. A further work has been done to minimize dimensions and costs, in order to deploy capillary installations. Furthermore, thanks to the work done from the side of the channel optimization, it has been possible to acquire not only standard environmental parameters, but also high definition pictures. Images of plants, trees, as well as fruits and leaves are taken every hour, and forwarded to a central gateway, interfaced with the Internet. A team of agronomists and biologists checks the state of the cultivation from remote, providing the farmer with continuous assistance at a reasonable cost. This is extremely important in Developing Countries, taking into account that in those locations experts cannot reach the fields and cannot provide the farmer with specialized, continuous consultancy, both for economical and logistic reasons. In a global scenario, where new diseases arise rapidly and continuously, the remote assistance provided by an expert can minimize farmer's risks to loose his harvest and reduce his revenues. The set of environmental parameters, together with the visual collection of cultivation conditions, is useful also to generate a culture database, particularly useful in developing regions, where there is almost never historical recorded trace, in particular about possible associated diseases and infections. Last but not least, the platform allows a significant improvement of the sustainability. Thanks to the assistance of the agronomist, the farmer can minimize the use of pesticides and chemicals, as well as reducing the number of additional treatments, resulting in significant advantages, in terms of production costs and organic quality.
[Show abstract][Hide abstract] ABSTRACT: We propose an intuitive, simple and hardware friendly, yet surprisingly novel
and efficient, received signal's angle of arrival (AoA) estimation scheme. Our
intuitive, two-phases cross-correlation based scheme relies on a switched beam
antenna array, which is used to collect an omni-directional signal using few
elements of the antenna array in the first phase. In the second phase, the
scheme switches the main beam of the antenna array to scan the angular region
of interest. The collected signal from each beam (direction or angle) is cross
correlated with the omni-directional signal. The cross-correlation coefficient
will be the highest at the correct AoA and relatively negligible elsewhere. The
proposed scheme simplicity stems from its low computational complexity (only
cross-correlation and comparison operations are required) and its independence
of the transmitted signal structure (does not require information about the
transmitted signal). The proposed scheme requires a receiver with switched beam
antenna array, which can be attached to a single radio frequency chain through
phase shifters, hence, its hardware friendliness. The high efficiency of our
system can be observed by comparing its performance with the literature's best
performing MUSIC algorithm. The comparison demonstrates that our scheme
outperforms the MUSIC algorithm, specially at low SNR levels. Moreover, the
number of sources that can be detected using our scheme is bound by the number
of switched beams, rather than the number of antenna elements in the case of
the MUSIC algorithm.
[Show abstract][Hide abstract] ABSTRACT: The paper presents an adaptive solution for the realization of ad hoc wireless sensor networks suitable to transport large quantities of data over narrowband channels. The electromagnetic front-end is specifically designed to maintain radiation efficiency even when inserted in media with random dissipative characteristics. The use of narrow band channels, as well as the possibility to decrease the carrier down to 180 MHz (compatibly with regulatory authorizations), provides robustness to interferences, lower signal sensitivity, and non-line-of-sight coverage. For all these reasons, the platform is being applied to cultivations, to construct an effective and low-cost instrument, which facilitates sustainable agriculture.
[Show abstract][Hide abstract] ABSTRACT: In this paper, characterization of an acoustic wireless sensor for leakage detection in underground pipes is presented. The sensor is based on an acoustic sensing element, called a hydrophone, which senses the noise inside the pipe. The sensor sends the sensed signals wirelessly to a gateway which is located on the ground. The gateway, in turn, relays these signals to a backend server for further processing. For concept-proofing, a novel experimental test-bed has been designed and realized in a water supply facility in Turin, Italy. In this paper, this test-bed is used to characterize the capability of the hydrophone of water leakage detection under high water pressure and under various leakage locations and volumes. The test-bed can also be used to test and evaluate the performance of any device that would operate in high pressure water pipes. The results show that the acoustic sensor is able to detect leakages with different magnitudes and at various locations.
[Show abstract][Hide abstract] ABSTRACT: The paper introduces a wireless sensor network platform specifically designed for the protection of workers employed in the building sector, exposed to critical physical agents, typical of their working scenario. The network configuration makes use of either a standard ZigBee communication scheme, or a more versatile ad-hoc set-up, which narrows the necessary transmission bandwidth and lowers the frequency of the carriers. The relevant part of the research activity has been concentrated on the design and realization of a compact, wearable, washable, ergonomic, low cost wireless sensor node, suitable to detect a huge variety of physical phenomena. The sample proposed in the paper has been specifically developed to measure two different kinds of exposure, UltraViolet rays and dust. Both these agents, for different reasons, represent a critical factors and a certified source of possible diseases. The sensor node is embedded on the worker garment: the electronic components are sewed on the cloth, and the antenna is integrated within the fabric, and, together with the fabric, forms a unique structure. Preliminary results, obtained with a non-optimized and non-compact node, testify the validity of the approach and its applicability to real cases.
[Show abstract][Hide abstract] ABSTRACT: The paper introduces an efficient procedure that allows the design of low cost magnetic antennas with arbitrary shape and extremely reduced dimensions. The technique is mainly analytical, with a simple and fast optimization procedure and it can be applied to any magnetic antenna, even with very complex geometry, e.g., with fractal shape. Simulations have been compared to measurements, proving an excellent agreement. The chosen configuration is implemented in planar geometry, where the transceiver and the matching circuit can be inserted within the antenna perimeter, allowing the realization of compact devices. For this reason, the device can be efficiently proposed for the realization of the terminal unit in wireless sensor networks. A first prototype has been constructed and tested and the results showed an excellent range.
[Show abstract][Hide abstract] ABSTRACT: The paper presents an innovative networked solution for a continuous measurement of human exposure to ultraviolet rays and dust. The platform is made up of mobile wireless sensors nodes, designed to be attached on clothes, in order to be simply wore by anybody. Power supply is not needed, thanks to the use of energy harvesting techniques. The physical sensor itself is selected among commercial components available off the shelf, but the antenna and the radio are designed on purpose and integrated on the dress. The whole device is realized by means of a manufacturing technique that allows its washability. Flexibility, light weight and small dimensions guarantee a non-intrusive presence of the component, which does not affect the normal activity of the subject. Several wireless networking solutions are considered and implemented, depending on the needs of the specific application and the connectivity range. The solution can be schematically applied to a huge variety of cases. Among all, we have selected a particular application, dedicated to workers employed in the construction sites, with particular reference to people working in Middle East Countries, where summer temperatures may become higher than 52 degrees and winter strong dust/sand storms may happen on a weekly basis. The general realization scheme is presented, together with an analysis of the performance of a first prototype.
[Show abstract][Hide abstract] ABSTRACT: In the recent days, small magnetic radiators are becoming more and more important, for a large variety of applications involving the use of ultra-small transmission bandwidths. Primary destinations of these radiators are represented by RFID technology, wireless sensor networks, data tracking, environment monitoring, where they can be used not only in free-space conditions, but also inside complex electromagnetic media. As a matter of fact, the antenna is an essential component that impacts the efficiency of the transmission, the size of the device, and the bandwidth operability. In this paper we introduce an analytical procedure, deduced by a typical EMC modeling approach, that allows the design of magnetic antennas with arbitrary shape and extremely reduced dimensions. The technique is based on a multi-conductor transmission lines approach: the matching circuit is configured by constructing, together with the antenna, a curvilinear three-conductors transmission line; hence, the matching impedance is computed analytically, without any optimization procedure, by a multi-conductor model. The procedure can be applied to any antenna geometry, even very complex ones, e.g., with fractal shape. Simulations have been compared to measurements, proving a good agreement. The major characteristic is represented by the capability to realize a 50 ohm radiator, without the insertion of a passive matching circuit. In this way, a relatively high efficiency is obtained, even if for an extremely narrow band, but the obtained (narrow) bandwidth is sufficient, especially for the mentioned applications. Since the design procedure is analytical, it can be efficiently applied to design and synthesize antennas in the free space, but also in general media. For this reason, the configuration can be efficiently proposed for the realization of the terminal unit when it is embedded inside lossy, complex material.
[Show abstract][Hide abstract] ABSTRACT: The paper introduces a compact sensing topology based on a distributed alignment of electromagnetic radiators, applicable to the analysis of water content in snow. A suitable set of sensors, deployed in a predefined space to form an ad-hoc network, reveals the differential variation of humidity inside snowfields, being a precise indicator of dramatic events such as avalanches and landslides. The light energy consumption and the compact dimensions foresee the possibility for an intensive exploitation to high mountain snowfields, as well as skiing areas.
[Show abstract][Hide abstract] ABSTRACT: In the recent days, small magnetic radiators are becoming more and more important, for a large variety of applications involving the use of ultra-small transmission bandwidths. Primary destinations of these radiators are represented by RFID technology, wireless sensor networks, data tracking, environment monitoring, where they can be used not only in free-space conditions, but also inside complex electromagnetic media. In this paper we introduce an analytical procedure that allows the design of magnetic antennas with arbitrary shape and extremely reduced dimensions. The technique is based on a multi-conductor transmission lines approach: the matching circuit is configured by constructing, together with the antenna, a curvilinear three-conductors transmission line; hence, the matching impedance is computed analytically, without any optimization procedure, by a multi-conductor model. Since the design procedure is analytical, it can be efficiently applied to design and synthesize antennas in the free space, but also in general media.
[Show abstract][Hide abstract] ABSTRACT: The paper presents an innovative solution for the realization of an ad-hoc infrastructure that implements remote control facilities for water and gas distribution pipelines. The realization is base on an implementation of mobile wireless sensors able to flow without any restraint in any kind of conduit. A dedicated design procedure allows the minimization of the sensing and transmitting hardware, maintaining a strong transmission efficiency even when pipelines are deployed underground. The wireless device is interfaced with an acoustic sensor suitable inside liquids and it is is waterproofed, so that its insertion within pipes filled of liquid has been made possible. The sensor communicates to fixed stations deployed on the ground. These stations collect the measured data and repeat them towards an Internet gateway, allowing remote post-processing of the information and the classification of the pipeline, in terms of possible leakages, obstructions, or sediments. The introduced technological solution has been experimentally validated in a controlled scenario, where an “ad-hoc” wireless sensor network has been specifically designed and realized. Results show the exploitability and reliability of the proposed platform.
[Show abstract][Hide abstract] ABSTRACT: The paper introduces an efficient procedure that allows the design of low cost magnetic antennas with arbitrary shape and extremely reduced dimensions. The technique does not need any optimization procedure and it can be applied to any antenna geometry, even very complex ones, e.g., with fractal shape. Simulations have been compared to measurements, proving a good agreement and an excellent performance in terms of radiation efficiency, not only in free space, but also when the antenna is collocated inside dissipative media. For this reason, the device can be efficiently proposed for the realization of the terminal unit in wireless sensor networks, especially when the node must be embedded inside lossy material.
[Show abstract][Hide abstract] ABSTRACT: In this paper, the electromagnetic field distribution inside a jet engine is studied through full wave analysis. Results are statistically analyzed by comparisons to the models used for the reverberation chamber with a mechanical mode stirrer. The jet engine is simulated as an open cylinder containing one set of rotating blades by using 'Ansys®HFSS'. A simple Hertzian dipole illuminates the interior structure as an incident wave excitation representing a transmitting antenna radiating continuous wave fields. The field distribution inside the engine, which results from a distinct set of rotating positions of the blades, is primarily studied through the simulation program. In our case, the mechanical stirrer is represented by the rotating set of blades. The field values are extracted at different planes along the cylindrical engine, and the average field is statistically analyzed. We show that the squared magnitude of the field component along the engine's main axis has an exponential distribution compared to the theoretical exponential distribution proved in a reverberation chamber. This approach promises to act as a novel effective method to analyze the engine system without dealing with the complex details inside the engine cavity.
Full-text · Article · Jan 2012 · Progress In Electromagnetics Research M