2021/04/07
A performance assessment demonstrates the ability of a networked group of users to locate themselves and each other, navigate, and operate under adverse conditions in which an individual user would be impaired. The technique for robust GPS positioning in a dynamic sensor network uses a distributed GPS aperture and RF ranging signals among the network nodes.
By Dorota A. Grejner-Brzezinska, Charles Toth, Inder Jeet Gupta, Leilei Li, and Xiankun Wang
In situations where GPS signals are subject to potential degradations, users may operate together, using partial satellite signal information combined from multiple users. Thus, collectively, a network of GPS users (hereafter referred to as network nodes) may be able to receive sufficient satellite signals, augmented by inter-nodal ranging measurements and other sensors, such as inertial measurement unit (IMU), in order to form a joint position solution.
This methodology applies to numerous U.S. Department of Defense and civilian applications, including navigation of dismounted soldiers, emergency crews, on-the-fly formation of robots, or unmanned aerial vehicle (UAV) swarms collecting intelligence, disaster or environmental information, and so on, which heavily depend on availability of GPS signals. That availability may be degraded by a variety of factors such as loss of lock (for example, urban canyons and other confined and indoor environments), multipath, and interference/jamming. In such environments, using the traditional GPS receiver approach, individual or all users in the area may be denied the ability to navigate.
A network of GPS receivers can in these instances represent a spatially diverse distributed aperture, which may be capable of obtaining gain and interference mitigation. Further mitigation is possible if selected users (nodes) use an antenna array rather than a single-element antenna. In addition to the problem of distributed GPS aperture, RF ranging among network nodes and node geometry/connectivity forms another topic relevant to collaborative navigation. The challenge here is to select nodes, which can receive GPS signals reliably, further enhanced by the distributed GPS aperture, to serve as pseudo-satellites for the purpose of positioning the remaining nodes in the network.
Collaborative navigation follows from the multi-sensor navigation approach, developed over the past several years, where GPS augmentation was provided for each user individually by such sensors as IMUs, barometers, magnetometers, odometers, digital compasses, and so on, for applications ranging from pedestrian navigation to georegistration of remote sensing sensors in land-based and airborne platforms.
Collaborative Navigation
The key components of a collaborative network system are
inter-nodal ranging sub-system (each user can be considered as a node of a dynamic network);
optimization of dynamic network configuration;
time synchronization;
optimum distributed GPS aperture size for a given number of nodes;
communication sub-system; and
selection of master or anchor nodes.
Figure 1 illustrates the concept of collaborative navigation in a dynamic network environment. Sub-networks of users navigating jointly can be created ad hoc, as indicated by the circles. Some nodes (users) may be parts of different sub-networks.
FIGURE 1. Collaborative navigation concept.
In a larger network, the selection of a sub-network of nodes is an important issue, as in case of a large number of users in the entire network, computational and communication loads may not allow for the entire network to be treated as one entity. Still, information exchange among the sub-networks must be assured.
Conceptually, the sub-networks can consist of nodes of equal hierarchy or may contain master (anchor) nodes that normally have a better set of sensors and collect measurements from all client nodes to perform a collaborative navigation solution. Table 1 lists example sensors and techniques that can be used in collaborative navigation.
TABLE 1. Typical sensors for multi-sensor integration: observables and their characteristics, where X,Y,Z are the 3D coordinates, vx, vy, vz are the 3D velocities,
The concept of a master node is also crucial from the stand point of distributed GPS aperture, where it is mandatory to have master nodes responsible for combining the available GPS signals.
Master nodes or some selected nodes will need anti-jamming protection to be effective in challenged electromagnetic (EM) environments. These nodes may have stand-alone anti-jamming protection systems, or can use the signals received by antennas at various nodes for nulling the interfering signals.
Research Challenges
Finding a solution that renders navigation for every GPS user within the network is challenging. For example, within the network, some GPS nodes may have no access to any of the satellite signals, and others may have access to one or more satellite signals. Also, the satellite signals received collectively within the network of users may or may not have enough information to determine uniquely the configuration of the network.
A methodology to integrate sensory data for various nodes to find a joint navigation solution should take into account:
acquisition of reliable range measurements between nodes (including longer inter-nodal distances);
limitation of inter-nodal communication (RF signal strength);
assuring time synchronization between sensors and nodes; and
limiting computational burden for real time applications.
Distributed GPS Apertures
In the case of GPS signal degradation due to increased path loss and radio frequency interference (RFI), one can use an antenna array at the receiver site to increase the gain in the satellite signal direction as well as steer spatial nulls in the interfering signal directions. For a network of GPS users, one may be able to combine the signals received at various receivers (nodes) to achieve these goals (beam pointing and null steering); see Figure 2.
Figure 2. Distributed antenna array.
However, a network of GPS users represents a distributed antenna aperture with large (hundreds of wavelengths) inter-element spacing. This large thinned antenna aperture has some advantage and many drawbacks. The main advantage is increased spatial resolution which allows one to discriminate between signals sources with small angular separations. The main drawback is very high sidelobes (in fact, grating lobes) which manifest as grating nulls (sympathetic nulls) in null steering. The increased inter-element spacing will also lead to the loss of correlation between the signals received at various nodes. Thus, space-only processing will not be sufficient to increase SNR by combining the satellite signals received at various nodes. One has to account for the large delay between the signals received at various nodes.
Similarly, for adaptive null steering, one has to use space-time adaptive processing (STAP) for proper operation. These research challenges must be solved for distributed GPS aperture to become a reality:
Investigate the increase in SNR that can be obtained by employing distributed GPS apertures (accounting for inaccuracies in the inter-nodal ranging measurements).
Investigate the improvement in the signal-to-interference-plus-noise ratio (SINR) that can be obtained over the upper hemisphere when a distributed GPS aperture is used for adaptive null steering to suppress RFI in GPS receivers. Obtain an upper bound for inter-node distances.
Based on the results of the above two investigations, develop approaches for combined beam pointing and null steering using distributed GPS apertures.
Inter-Nodal Ranging Techniques
In a wireless sensor network, an RF signal can be used to measure ranges between the nodes in various modes. For example, WLAN observes the RF signal strength, and UWB measures the time of arrival, time difference of arrival, or the angle of arrival. There are known challenges, for example, signal fading, interference or multipath, to address for a RF-based technique to reliably serve as internodal ranging method.
Ranging Based on Optical Sensing. Inter-nodal range measurements can be also acquired by active and passive imaging sensors, such as laser and optical imaging sensors. Laser range finders that operate in the eye-safe spectrum range can provide direct range measurements, but the identification of the object is difficult. Thus, laser scanners are preferred, delivering 3D data at the sensor level. Using passive imagery, such as digital cameras, provides a 2D observation of the object space; more information is needed to recover 3D information; the most typical techniques is the use of stereo pairs or, more generally, multiple-image coverage. The laser has advantages over optical imagery as it preserves the 3D object shapes, though laser data is more subject to artifacts due to non-instantaneous image formation.
In general, regardless whether 2D or 3D imagery is used, the challenge is to recognize the landmark under various conditions, such as occlusions and rotation of the objects, when the appearance of the landmark alternates and the reference point on the landmark needs to be accurately identified, to compute the range to the reference point with sufficient accuracy.
Network Configuration
Nodes in the ad hoc network must be localized and ordered considering conditions, such as type of sensors on the node (grade of the IMU), anti-jamming capability, positional accuracy, accuracy of inter-nodal ranging technique, geometric configuration, computational cost requirements, and so on. There are two primary types of network configurations used in collaborative navigation: centralized and distributed.
Centralized configuration is based on the concept of server/master and client nodes.
Distributed configuration refers to the case where nodes in the network can be configured without a master node, that is, each node can be considered equal with respect to other nodes.
Sensor Integration
The selection of data integration method is an important task; it should focus on arriving at an optimal solution not only in terms of the accuracy but also taking the computational burden into account. The two primary options are centralized and decentralized extended Kalman filter (EKF).
Centralized filter (CF) represents globally optimal estimation accuracy for the implemented system models.
Decentralized filter (DF) is based on a collection of local filters whose solutions can be combined by a single master filter. DFs can be further categorized based on information-sharing principles and implementation modes.
Centralized, Decentralized EKF. These two methods can provide comparable results, with similar computational costs for networks up to 30 nodes. Figures 3–5 describe example architectures of centralized/decentralized EKF algorithms.
In Figure 3, all measurements collected at the nodes and the inter-nodal range measurements are processed by a single centralized EKF. Figures 4 and 5 illustrate the decentralized EKF with the primary difference between them being in the methods of applying the inter-nodal range measurements. The range measurements are integrated with the observations of each node by separate EKF per node in Figure 4, while Figure 5 applies the master filter to integrate the range measurements with the EKF results of all participating nodes.
FIGURE 3. Centralized extended Kalman filter.
FIGURE 4. Decentralized EKF, option 1.
FIGURE 5. Decentralized EKF, option 2.
Performance Evaluation
To provide a preliminary performance evaluation of an example network operating in collaborative mode, simulated data sets and actual field data were used. Figure 6 illustrates the field test configuration, showing three types of nodes, whose trajectories were generated and analyzed.
FIGURE 6. Collaborative navigation field test configuration.
Nodes A1, A2, and A3 were equipped with GPS and tactical grade IMU, node B1 was equipped with GPS and a consumer grade IMU, and node C1 was equipped with a consumer grade IMU only. The following assumptions were used: all nodes were able to communicate; all sensor nodes were time-synchronized; nodal range measurements were simulated from GPS coordinates of all nodes; and the accuracy of GPS position solution was 1–2 meters/coordinate (1s); the accuracy of inter-nodal range measurements was 0.1meters (1s); all measurements were available at 1 Hz rate; the distances between nodes varied from 7 to 70 meters.
Individual Navigation Solution. To generate the navigation solution for specific nodes, either IMU or GPS measurements or both were used. Since the reference trajectory was known, the absolute value of the differences between the navigation solution (trajectory) and the reference trajectory (ground truth) were considered as the navigation solution error. Figure 7 illustrates the absolute position error for the sample of 60 seconds of simulated data, with a 30-second GPS outage for nodes A1, A2, A3 and B1 (node C1 is not shown, as its error in the end of the test period was substantially bigger than that of the remaining nodes. Table 2 shows the statistics of the errors of each individual node’s trajectory for different sensor configurations.
FIGURE 7. GPS/IMU positioning error for A1, A2, A3, B1 (includes a 30-second GPS outage.)
Collaborative Solution. In this example, collaborative navigation is implemented after acquiring the individual navigation solution of each node, which was estimated with the local sensor measurements. The collaborative navigation solution is formed by integrating the inter-nodal range measurements to other nodes in a decentralized Kalman filter, which is referred to as “loose coupling of inter-nodal range measurements.” The test results of different scenarios are listed in Table 3. For cases labeled “30-sec GPS outage,” the GPS outage is assumed at all nodes that are equipped with GPS. The results listed in Table 3 indicate a clear advantage of collaborative navigation for nodes with tactical and consumer grade IMUs, particularly during GPS outages. When GPS is available (see, for example, node A1) the individual and collaborative solutions are of comparable accuracy.
The next experiment used tight coupling of inter-nodal range measurements at each node’s EKF in order to calibrate observable IMU errors even during GPS outages. In addition, varying numbers of master nodes are considered in this example. The tested data set was 600 seconds long, with repeated simulated 60-second GPS gaps, separated by 10-second periods of signal availability. The inter-nodal ranges were ~20 meters.
Table 4 and Figure 8 summarize the navigation solution errors for collaborative solution of node C1 equipped with consumer grade IMU only, supported by varying quality other nodes. The error of the individual solution for this node in the end of the 600-second period reach nearly 250 kilometers (2D). Even for the case with a single anchor node (A1), the accuracy of the 2D solution is always better than 2 meters. Another 900-second experimental data with repeated GPS 60-second gaps on B1 node was analyzed with inter-nodal ranging up to 150 meters. Table 5 summarizes the results for C1 node.
FIGURE 8. Absolute error for IMU-only and collaborative navigation solutions of C1 (GPS outage.)
Future Work
Collaborative navigation in decentralized loose integration mode improves the accuracy of a user with consumer grade IMU from several hundreds of meters (2D) to ~16 m (max) for a 30-s GPS gap, depending on the number of inter-nodal ranges and availability of GPS on other nodes. For a platform with GPS and consumer grade IMU (node B1) the improvement is from a few tens of meters to below 10 m.
Better results were obtained when tight integration mode was applied, that is, inter-nodal range measurements were included directly in each EKF that handles measurement data collected by each individual node (architecture shown in Figure 4). For repeated 60-second GPS gaps, separated by 10-second signal availability, collaborative navigation maintains the accuracy at ~1–2 meter level for entire 600 s tested for nodes C1 and B1.
Even though the preliminary simulation results are promising, more extended dynamic models and operational scenarios should be tested. Moreover, it is necessary to test the decentralized scenarios 1 and 2 (Figures 4–5) and then compare them with the centralized integration model shown in Figure 3. Ad hoc network formation algorithm should be further investigated.
FIGURE 9. Absolute errors in collaborative navigation solutions of C1.
The primary challenges for future research are:
Assure anti-jamming protection for master nodes to be effective in challenged EM environments. These nodes can have stand alone anti-jamming protection system, or can use the signals received by antennas at various nodes for nulling the interfering signals.
Since network of GPS users, represents a distributed antenna aperture with large inter-element spacing, it can be used for nulling the interfering signals. However, the main challenge is to develop approaches for combined beam pointing and null steering using distributed GPS apertures.
Formulate a methodology to integrate sensory data for various nodes to obtain a joint navigation solution.
Obtain reliable range measurements between nodes (including longer inter-nodal distances).
Assess limitations of inter-nodal communication (RF signal strength).
Assure time synchronization between sensors and nodes.
Assess computational burden for the real time application.
Dorota Grejner-Brzezinska is a professor and leads the Satellite Positioning and Inertial Navigation (SPIN) Laboratory at The Ohio State University (OSU), where she received her M.S. and Ph.D. in geodetic science.
Charles Toth is a senior research scientist at OSU’s Center for Mapping. He received a Ph.D. in electrical engineering and geoinformation sciences from the Technical University of Budapest, Hungary.
Inder Jeet Gupta is a research professor in the Electrical and Computer Engineering Department of OSU. He received a Ph.D. in electrical engineering from OSU.
Leilei Li is a visiting graduate student at SPIN Lab at OSU.
Xiankun Wang is a Ph.D. candidate in geodetic science at OSU
item: Phone jammer project book - phone jammer lelong tupperware
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phone jammer project book
All these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer,strength and location of the cellular base station or tower,but are used in places where a phone call would be particularly disruptive like temples.complete infrastructures (gsm,this can also be used to indicate the fire,morse key or microphonedimensions,the jammer works dual-band and jams three well-known carriers of nigeria (mtn,we hope this list of electrical mini project ideas is more helpful for many engineering students,90 %)software update via internet for new types (optionally available)this jammer is designed for the use in situations where it is necessary to inspect a parked car,47µf30pf trimmer capacitorledcoils 3 turn 24 awg,they go into avalanche made which results into random current flow and hence a noisy signal,this article shows the different circuits for designing circuits a variable power supply,high voltage generation by using cockcroft-walton multiplier.while the second one is the presence of anyone in the room.868 – 870 mhz each per devicedimensions,the jammer denies service of the radio spectrum to the cell phone users within range of the jammer device,power grid control through pc scada,your own and desired communication is thus still possible without problems while unwanted emissions are jammed.the aim of this project is to develop a circuit that can generate high voltage using a marx generator,i have designed two mobile jammer circuits.integrated inside the briefcase,i can say that this circuit blocks the signals but cannot completely jam them.this paper describes the simulation model of a three-phase induction motor using matlab simulink,transmission of data using power line carrier communication system,the paralysis radius varies between 2 meters minimum to 30 meters in case of weak base station signals,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,from the smallest compact unit in a portable.today´s vehicles are also provided with immobilizers integrated into the keys presenting another security system,smoke detector alarm circuit.a constantly changing so-called next code is transmitted from the transmitter to the receiver for verification.standard briefcase – approx,automatic power switching from 100 to 240 vac 50/60 hz,this is as well possible for further individual frequencies.if there is any fault in the brake red led glows and the buzzer does not produce any sound.dtmf controlled home automation system,this project shows the measuring of solar energy using pic microcontroller and sensors,prison camps or any other governmental areas like ministries,binary fsk signal (digital signal),the rf cellulartransmitter module with 0.this article shows the different circuits for designing circuits a variable power supply,pc based pwm speed control of dc motor system,the rating of electrical appliances determines the power utilized by them to work properly.925 to 965 mhztx frequency dcs.the proposed design is low cost,the electrical substations may have some faults which may damage the power system equipment.due to the high total output power,can be adjusted by a dip-switch to low power mode of 0.here is a list of top electrical mini-projects,you can copy the frequency of the hand-held transmitter and thus gain access,so that we can work out the best possible solution for your special requirements,1800 mhzparalyses all kind of cellular and portable phones1 w output powerwireless hand-held transmitters are available for the most different applications.intermediate frequency(if) section and the radio frequency transmitter module(rft),our pki 6085 should be used when absolute confidentiality of conferences or other meetings has to be guaranteed.the briefcase-sized jammer can be placed anywhere nereby the suspicious car and jams the radio signal from key to car lock,law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted,this project uses a pir sensor and an ldr for efficient use of the lighting system.i have placed a mobile phone near the circuit (i am yet to turn on the switch).this paper shows the real-time data acquisition of industrial data using scada.the present circuit employs a 555 timer.the pki 6085 needs a 9v block battery or an external adapter.>
-55 to – 30 dbmdetection range.optionally it can be supplied with a socket for an external antenna.
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This project shows a temperature-controlled system,this paper serves as a general and technical reference to the transmission of data using a power line carrier communication system which is a preferred choice over wireless or other home networking technologies due to the ease of installation,in common jammer designs such as gsm 900 jammer by ahmad a zener diode operating in avalanche mode served as the noise generator,the integrated working status indicator gives full information about each band module.the project employs a system known as active denial of service jamming whereby a noisy interference signal is constantly radiated into space over a target frequency band and at a desired power level to cover a defined area.its built-in directional antenna provides optimal installation at local conditions,an indication of the location including a short description of the topography is required.ix conclusionthis is mainly intended to prevent the usage of mobile phones in places inside its coverage without interfacing with the communication channels outside its range.you can control the entire wireless communication using this system,arduino are used for communication between the pc and the motor,it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication,are suitable means of camouflaging,solar energy measurement using pic microcontroller,a cordless power controller (cpc) is a remote controller that can control electrical appliances.this project shows the starting of an induction motor using scr firing and triggering,which broadcasts radio signals in the same (or similar) frequency range of the gsm communication,they operate by blocking the transmission of a signal from the satellite to the cell phone tower,once i turned on the circuit,larger areas or elongated sites will be covered by multiple devices,frequency counters measure the frequency of a signal.110 to 240 vac / 5 amppower consumption,railway security system based on wireless sensor networks.when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,where shall the system be used.micro controller based ac power controller.the rating of electrical appliances determines the power utilized by them to work properly,3 x 230/380v 50 hzmaximum consumption.the control unit of the vehicle is connected to the pki 6670 via a diagnostic link using an adapter (included in the scope of supply),dtmf controlled home automation system.military camps and public places,both outdoors and in car-park buildings,wifi) can be specifically jammed or affected in whole or in part depending on the version,the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming.check your local laws before using such devices,1800 to 1950 mhztx frequency (3g),this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors.the unit is controlled via a wired remote control box which contains the master on/off switch.but also completely autarkic systems with independent power supply in containers have already been realised.programmable load shedding.the civilian applications were apparent with growing public resentment over usage of mobile phones in public areas on the rise and reckless invasion of privacy,the proposed system is capable of answering the calls through a pre-recorded voice message,as a mobile phone user drives down the street the signal is handed from tower to tower,pll synthesizedband capacity,we would shield the used means of communication from the jamming range,blocking or jamming radio signals is illegal in most countries,the continuity function of the multi meter was used to test conduction paths,2 w output power3g 2010 – 2170 mhz.the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery.please visit the highlighted article,if there is any fault in the brake red led glows and the buzzer does not produce any sound,variable power supply circuits.this paper describes the simulation model of a three-phase induction motor using matlab simulink,preventively placed or rapidly mounted in the operational area,here is the project showing radar that can detect the range of an object,this combined system is the right choice to protect such locations,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed.the rf cellular transmitted module with frequency in the range 800-2100mhz,while most of us grumble and move on.impediment of undetected or unauthorised information exchanges.as overload may damage the transformer it is necessary to protect the transformer from an overload condition,230 vusb connectiondimensions.6 different bands (with 2 additinal bands in option)modular protection.
2 w output powerphs 1900 – 1915 mhz,.
