2021/04/09
A Civilian GPS Position Authentication System
By Zhefeng Li and Demoz Gebre-Egziabher
INNOVATION INSIGHTS by Richard Langley
MY UNIVERSITY, the University of New Brunswick, is one of the few institutes of higher learning still using Latin at its graduation exercises. The president and vice-chancellor of the university asks the members of the senate and board of governors present “Placetne vobis Senatores, placetne, Gubernatores, ut hi supplicatores admittantur?” (Is it your pleasure, Senators, is it your pleasure, Governors, that these supplicants be admitted?). In the Oxford tradition, a supplicant is a student who has qualified for their degree but who has not yet been admitted to it. Being a UNB senator, I was familiar with this usage of the word supplicant. But I was a little surprised when I first read a draft of the article in this month’s Innovation column with its use of the word supplicant to describe the status of a GPS receiver.
If we look up the definition of supplicant in a dictionary, we find that it is “a person who makes a humble or earnest plea to another, especially to a person in power or authority.” Clearly, that describes our graduating students. But what has it got to do with a GPS receiver? Well, it seems that the word supplicant has been taken up by engineers developing protocols for computer communication networks and with a similar meaning. In this case, a supplicant (a computer or rather some part of its operating system) at one end of a secure local area network seeks authentication to join the network by submitting credentials to the authenticator on the other end. If authentication is successful, the computer is allowed to join the network. The concept of supplicant and authenticator is used, for example, in the IEEE 802.1X standard for port-based network access control.
Which brings us to GPS. When a GPS receiver reports its position to a monitoring center using a radio signal of some kind, how do we know that the receiver or its associated communications unit is telling the truth? It’s not that difficult to generate false position reports and mislead the monitoring center into believing the receiver is located elsewhere — unless an authentication procedure is used. In this month’s column, we look at the development of a clever system that uses the concept of supplicant and authenticator to assess the truthfulness of position reports.
“Innovation” is a regular feature that discusses advances in GPS technology andits applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick. He welcomes comments and topic ideas. Contact him at lang @ unb.ca.
This article deals with the problem of position authentication. The term “position authentication” as discussed in this article is taken to mean the process of checking whether position reports made by a remote user are truthful (Is the user where they say they are?) and accurate (In reality, how close is a remote user to the position they are reporting?). Position authentication will be indispensable to many envisioned civilian applications. For example, in the national airspace of the future, some traffic control services will be based on self-reported positions broadcast via ADS-B by each aircraft. Non-aviation applications where authentication will be required include tamper-free shipment tracking and smart-border systems to enhance cargo inspection procedures at commercial ports of entry. The discussions that follow are the outgrowth of an idea first presented by Sherman Lo and colleagues at Stanford University (see Further Reading).
For illustrative purposes, we will focus on the terrestrial application of cargo tracking. Most of the commercial fleet and asset tracking systems available in the market today depend on a GPS receiver installed on the cargo or asset. The GPS receiver provides real-time location (and, optionally, velocity) information. The location and the time when the asset was at a particular location form the tracking message, which is sent back to a monitoring center to verify if the asset is traveling in an expected manner. This method of tracking is depicted graphically in FIGURE 1.
FIGURE 1. A typical asset tracking system.
The approach shown in Figure 1 has at least two potential scenarios or fault modes, which can lead to erroneous tracking of the asset. The first scenario occurs when an incorrect position solution is calculated as a result of GPS RF signal abnormalities (such as GPS signal spoofing). The second scenario occurs when the correct position solution is calculated but the tracking message is tampered with during the transmission from the asset being tracked to the monitoring center. The first scenario is a falsification of the sensor and the second scenario is a falsification of the transmitted position report.
The purpose of this article is to examine the problem of detecting sensor or report falsification at the monitoring center. We discuss an authentication system utilizing the white-noise-like spreading codes of GPS to calculate an authentic position based on a snapshot of raw IF signal from the receiver.
Using White Noise as a Watermark
The features for GPS position authentication should be very hard to reproduce and unique to different locations and time. In this case, the authentication process is reduced to detecting these features and checking if these features satisfy some time and space constraints. The features are similar to the well-designed watermarks used to detect counterfeit currency.
A white-noise process that is superimposed on the GPS signal would be a perfect watermark signal in the sense that it is impossible reproduce and predict. FIGURE 2 is an abstraction that shows how the above idea of a superimposed white-noise process would work in the signal authentication problem. The system has one transmitter, Tx , and two receivers, Rs and Ra. Rs is the supplicant and Ra is the authenticator. The task of the authenticator is to determine whether the supplicant is using a signal from Tx or is being spoofed by a malicious transmitter, Tm. Ra is the trusted source, which gets a copy of the authentic signal, Vx(t) (that is, the signal transmitted by Tx). The snapshot signal, Vs(t), received at Rs is sent to the trusted agent to compare with the signal, Va(t), received at Ra. Every time a verification is performed, the snapshot signal from Rs is compared with a piece of the signal from Ra. If these two pieces of signal match, we can say the snapshot signal from Rs was truly transmitted from Tx. For the white-noise signal, match detection is accomplished via a cross-correlation operation (see Further Reading). The cross-correlation between one white-noise signal and any other signal is always zero. Only when the correlation is between the signal and its copy will the correlation have a non-zero value. So a non-zero correlation means a match. The time when the correlation peak occurs provides additional information about the distance between Ra and Rs.
Unfortunately, generation of a white-noise watermark template based on a mathematical model is impossible. But, as we will see, there is an easy-to-use alternative.
FIGURE 2. Architecture to detect a snapshot of a white-noise signal.
An Intrinsic GPS Watermark
The RF carrier broadcast by each GPS satellite is modulated by the coarse/acquisition (C/A) code, which is known and which can be processed by all users, and the encrypted P(Y) code, which can be decoded and used by Department of Defense (DoD) authorized users only. Both civilians and DoD-authorized users see the same signal. To commercial GPS receivers, the P(Y) code appears as uncorrelated noise. Thus, as discussed above, this noise can be used as a watermark, which uniquely encodes locations and times. In a typical civilian GPS receiver’s tracking loop, this watermark signal can be found inside the tracking loop quadrature signal.
The position authentication approach discussed here is based on using the P(Y) signal to determine whether a user is utilizing an authentic GPS signal. This method uses a segment of noisy P(Y) signal collected by a trusted user (the authenticator) as a watermark template. Another user’s (the supplicant’s) GPS signal can be compared with the template signal to judge if the user’s position and time reports are authentic. Correlating the supplicant’s signal with the authenticator’s copy of the signal recorded yields a correlation peak, which serves as a watermark. An absent correlation peak means the GPS signal provided by the supplicant is not genuine. A correlation peak that occurs earlier or later than predicted (based on the supplicant’s reported position) indicates a false position report.
System Architecture
FIGURE 3 is a high-level architecture of our proposed position authentication system. In practice, we need a short snapshot of the raw GPS IF signal from the supplicant. This piece of the signal is the digitalized, down-converted, IF signal before the tracking loops of a generic GPS receiver. Another piece of information needed from the supplicant is the position solution and GPS Time calculated using only the C/A signal. The raw IF signal and the position message are transmitted to the authentication center by any data link (using a cell-phone data network, Wi-Fi, or other means).
FIGURE 3. Architecture of position authentication system.
The authentication station keeps track of all the common satellites seen by both the authenticator and the supplicant. Every common satellite’s watermark signal is then obtained from the authenticator’s tracking loop. These watermark signals are stored in a signal database. Meanwhile, the pseudorange between the authenticator and every satellite is also calculated and is stored in the same database.
When the authentication station receives the data from the supplicant, it converts the raw IF signal into the quadrature (Q) channel signals. Then the supplicant’s Q channel signal is used to perform the cross-correlation with the watermark signal in the database. If the correlation peak is found at the expected time, the supplicant’s signal passes the signal-authentication test. By measuring the relative peak time of every common satellite, a position can be computed. The position authentication involves comparing the reported position of the supplicant to this calculated position. If the difference between two positions is within a pre-determined range, the reported position passes the position authentication.
While in principle it is straightforward to do authentication as described above, in practice there are some challenges that need to be addressed. For example, when there is only one common satellite, the only common signal in the Q channel signals is this common satellite’s P(Y) signal. So the cross-correlation only has one peak. If there are two or more common satellites, the common signals in the Q channel signals include not only the P(Y) signals but also C/A signals. Then the cross-correlation result will have multiple peaks. We call this problem the C/A leakage problem, which will be addressed below.
C/A Residual Filter
The C/A signal energy in the GPS signal is about double the P(Y) signal energy. So the C/A false peaks are higher than the true peak. The C/A false peaks repeat every 1 millisecond. If the C/A false peaks occur, they are greater than the true peak in both number and strength. Because of background noise, it is hard to identify the true peak from the correlation result corrupted by the C/A residuals.
To deal with this problem, a high-pass filter can be used. Alternatively, because the C/A code is known, a match filter can be designed to filter out any given GPS satellite’s C/A signal from the Q channel signal used for detection. However, this implies that one match filter is needed for every common satellite simultaneously in view of the authenticator and supplicant. This can be cumbersome and, thus, the filtering approach is pursued here.
In the frequency domain, the energy of the base-band C/A signal is mainly (56 percent) within a ±1.023 MHz band, while the energy of the base-band P(Y) signal is spread over a wider band of ±10.23 MHz. A high-pass filter can be applied to Q channel signals to filter out the signal energy in the ±1.023 MHz band. In this way, all satellites’ C/A signal energy can be attenuated by one filter rather than using separate match filters for different satellites.
FIGURE 4 is the frequency response of a high-pass filter designed to filter out the C/A signal energy. The spectrum of the C/A signal is also plotted in the figure. The high-pass filter only removes the main lobe of the C/A signals. Unfortunately, the high-pass filter also attenuates part of the P(Y) signal energy. This degrades the auto-correlation peak of the P(Y) signal. Even though the gain of the high-pass filter is the same for both the C/A and the P(Y) signals, this effect on their auto-correlation is different. That is because the percentage of the low-frequency energy of the C/A signal is much higher than that of the P(Y) signal. This, however, is not a significant drawback as it may appear initially. To see why this is so, note that the objective of the high-pass filter is to obtain the greatest false-peak rejection ratio defined to be the ratio between the peak value of P(Y) auto-correlation and that of the C/A auto-correlation. The false-peak rejection ratio of the non-filtered signals is 0.5. Therefore, all one has to do is adjust the cut-off frequency of the high-pass filter to achieve a desired false-peak rejection ratio.
FIGURE 4. Frequency response of the notch filter.
The simulation results in FIGURE 5 show that one simple high-pass filter rather than multiple match filters can be designed to achieve an acceptable false-peak rejection ratio. The auto-correlation peak value of the filtered C/A signal and that of the filtered P(Y) signal is plotted in the figure. While the P(Y) signal is attenuated by about 25 percent, the C/A code signal is attenuated by 91.5 percent (the non-filtered C/A auto-correlation peak is 2). The false-peak rejection ratio is boosted from 0.5 to 4.36 by using the appropriate high-pass filter.
FIGURE 5. Auto-correlation of the filtered C/A and P(Y) signals.
Position Calculation
Consider the situation depicted in FIGURE 6 where the authenticator and the supplicant have multiple common satellites in view. In this case, not only can we perform the signal authentication but also obtain an estimate of the pseudorange information from the authentication. Thus, the authenticated pseudorange information can be further used to calculate the supplicant’s position if we have at least three estimates of pseudoranges between the supplicant and GPS satellites. Since this position solution of the supplicant is based on the P(Y) watermark signal rather than the supplicant’s C/A signal, it is an independent and authentic solution of the supplicant’s position. By comparing this authentic position with the reported position of the supplicant, we can authenticate the veracity of the supplicant’s reported GPS position.
FIGURE 6. Positioning using a watermark signal.
The situation shown in Figure 6 is very similar to double-difference differential GPS. The major difference between what is shown in the figure and the traditional double difference is how the differential ranges are calculated. Figure 6 shows how the range information can be obtained during the signal authentication process. Let us assume that the authenticator and the supplicant have four common GPS satellites in view: SAT1, SAT2, SAT3, and SAT4. The signals transmitted from the satellites at time t are S1(t), S2(t), S3(t), and S4(t), respectively. Suppose a signal broadcast by SAT1 at time t0 arrives at the supplicant at t0 + ν1s where ν1s is the travel time of the signal. At the same time, signals from SAT2, SAT3, and SAT4 are received by the supplicant. Let us denote the travel time of these signals as ν2s, ν3s, and ν4s, respectively. These same signals will be also received at the authenticator. We will denote the travel times for the signals from satellite to authenticator as ν1a, ν2a, ν3a, and ν4a. The signal at a receiver’s antenna is the superposition of the signals from all the satellites. This is shown in FIGURE 7 where a snapshot of the signal received at the supplicant’s antenna at time t0 + ν1s includes GPS signals from SAT1, SAT2, SAT3, and SAT4. Note that even though the arrival times of these signals are the same, their transmit times (that is, the times they were broadcast from the satellites) are different because the ranges are different. The signals received at the supplicant will be S1(t0), S2(t0 + ν1s – ν2s), S3(t0 + ν1s – ν3s), and S4(t0 + ν1s – ν4s). This same snapshot of the signals at the supplicant is used to detect the matched watermark signals from SAT1, SAT2, SAT3, and SAT4 at the authenticator. Thus the correlation peaks between the supplicant’s and the authenticator’s signal should occur at t0 + ν1a, t0 + ν1s – ν2s + ν2a, t0 + ν1s – ν3s + ν3a, and t0 + ν1s – ν4s + ν4a.
Referring to Figure 6 again, suppose the authenticator’s position (xa, ya, za) is known but the supplicant’s position (xs, ys, zs) is unknown and needs to be determined. Because the actual ith common satellite (xi , yi , zi ) is also known to the authenticator, each of the ρia, the pseudorange between the ith satellite and the authenticator, is known. If ρis is the pseudorange to the ith satellite measured at the supplicant, the pseudoranges and the time difference satisfies equation (1):
ρ2s – ρ1s= ρ2a – ρ1a – ct21 + cχ21 (1)
where χ21 is the differential range error primarily due to tropospheric and ionospheric delays. In addition, c is the speed of light, and t21 is the measured time difference as shown in Figure 7. Finally, ρis for i = 1, 2, 3, 4 is given by:
(2)
FIGURE 7. Relative time delays constrained by positions.
If more than four common satellites are in view between the supplicant and authenticator, equation (1) can be used to form a system of equations in three unknowns. The unknowns are the components of the supplicant’s position vector rs = [xs, ys, zs]T. This equation can be linearized and then solved using least-squares techniques. When linearized, the equations have the following form:
Aδrs= δm (3)
where δrs = [δxs,δys,δzs]T, which is the estimation error of the supplicant’s position. The matrix A is given by
where is the line of sight vector from the supplicant to the ith satellite. Finally, the vector δm is given by:
(4)
where δri is the ith satellite’s position error, δρia is the measurement error of pseudorange ρia or pseudorange noise. In addition, δtij is the time difference error. Finally, δχij is the error of χij defined earlier.
Equation (3) is in a standard form that can be solved by a weighted least-squares method. The solution is
δrs = ( AT R-1 A)-1 AT R-1δm (5)
where R is the covariance matrix of the measurement error vector δm. From equations (3) and (5), we can see that the supplicant’s position accuracy depends on both the geometry and the measurement errors.
Hardware and Software
In what follows, we describe an authenticator which is designed to capture the GPS raw signals and to test the performance of the authentication method described above. Since we are relying on the P(Y) signal for authentication, the GPS receivers used must have an RF front end with at least a 20-MHz bandwidth. Furthermore, they must be coupled with a GPS antenna with a similar bandwidth. The RF front end must also have low noise. This is because the authentication method uses a noisy piece of the P(Y) signal at the authenticator as a template to detect if that P(Y) piece exists in the supplicant’s raw IF signal. Thus, the detection is very sensitive to the noise in both the authenticator and the supplicant signals. Finally, the sampling of the down-converted and digitized RF signal must be done at a high rate because the positioning accuracy depends on the accuracy of the pseudorange reconstructed by the authenticator. The pseudorange is calculated from the time-difference measurement. The accuracy of this time difference depends on the sampling frequency to digitize the IF signal. The high sampling frequency means high data bandwidth after the sampling.
The authenticator designed for this work and shown in FIGURE 8 satisfies the above requirements. A block diagram of the authenticator is shown in Figure 8a and the constructed unit in Figure 8b. The IF signal processing unit in the authenticator is based on the USRP N210 software-defined radio. It offers the function of down converting, digitalization, and data transmission. The firmware and field-programmable-gate-array configuration in the USRP N210 are modified to integrate a software automatic gain control and to increase the data transmission efficiency. The sampling frequency is 100 MHz and the effective resolution of the analog-to-digital conversion is 6 bits. The authenticator is battery powered and can operate for up to four hours at full load.
FIGURE 8a. Block diagram of GPS position authenticator.
Performance Validation
Next, we present results demonstrating the performance of the authenticator described above. First, we present results that show we can successfully deal with the C/A leakage problem using the simple high-pass filter. We do this by performing a correlation between snapshots of signal collected from the authenticator and a second USRP N210 software-defined radio. FIGURE 9a is the correlation result without the high-pass filter. The periodic peaks in the result have a period of 1 millisecond and are a graphic representation of the C/A leakage problem. Because of noise, these peaks do not have the same amplitude. FIGURE 9b shows the correlation result using the same data snapshot as in Figure 9a. The difference is that Figure 9b uses the high-pass filter to attenuate the false peaks caused by the C/A signal residual. Only one peak appears in this result as expected and, thus, confirms the analysis given earlier.
FIGURE 9a. Example of cross-correlation detection results without high-pass filter.
FIGURE 9b. Example of cross-correlation with high-pass filter.
We performed an experiment to validate the authentication performance. In this experiment, the authenticator and the supplicant were separated by about 1 mile (about 1.6 kilometers). The location of the authenticator was fixed. The supplicant was then sequentially placed at five points along a straight line. The distance between two adjacent points is about 15 meters. The supplicant was in an open area with no tall buildings or structures. Therefore, a sufficient number of satellites were in view and multipath, if any, was minimal. The locations of the five test points are shown in FIGURE 10.
FIGURE 10. Five-point field test. Image courtesy of Google.
The first step of this test was to place the supplicant at point A and collect a 40-millisecond snippet of data. This data was then processed by the authenticator to determine if:
The signal contained the watermark. We call this the “signal authentication test.” It determines whether a genuine GPS signal is being used to form the supplicant’s position report.
The supplicant is actually at the position coordinates that they say they are. We call this the “position authentication test.” It determines whether or not falsification of the position report is being attempted.
Next, the supplicant was moved to point B. However, in this instance, the supplicant reports that it is still located at point A. That is, it makes a false position report. This is repeated for the remaining positions (C through E) where at each point the supplicant reports that it is located at point A. That is, the supplicant continues to make false position reports.
In this experiment, we have five common satellites between the supplicant (at all of the test points A to E) and the authenticator. The results of the experiment are summarized in TABLE 1. If we can detect a strong peak for every common satellite, we say this point passes the signal authentication test (and note “Yes” in second column of Table 1). That means the supplicant’s raw IF signal has the watermark signal from every common satellite. Next, we perform the position authentication test. This test tries to determine whether the supplicant is at the position it claims to be. If we determine that the position of the supplicant is inconsistent with its reported position, we say that the supplicant has failed the position authentication test. In this case we put a “No” in the third column of Table 1. As we can see from Table 1, the performance of the authenticator is consistent with the test setup. That is, even though the wrong positions of points (B, C, D, E) are reported, the authenticator can detect the inconsistency between the reported position and the raw IF data. Furthermore, since the distance between two adjacent points is 15 meters, this implies that resolution of the position authentication is at or better than 15 meters. While we have not tested it, based on the timing resolution used in the system, we believe resolutions better than 12 meters are achievable.
Table 1. Five-point position authentication results.
Conclusion
In this article, we have described a GPS position authentication system. The authentication system has many potential applications where high credibility of a position report is required, such as cargo and asset tracking. The system detects a specific watermark signal in the broadcast GPS signal to judge if a receiver is using the authentic GPS signal. The differences between the watermark signal travel times are constrained by the positions of the GPS satellites and the receiver. A method to calculate an authentic position using this constraint is discussed and is the basis for the position authentication function of the system. A hardware platform that accomplishes this was developed using a software-defined radio. Experimental results demonstrate that this authentication methodology is sound and has a resolution of better than 15 meters. This method can also be used with other GNSS systems provided that watermark signals can be found. For example, in the Galileo system, the encrypted Public Regulated Service signal is a candidate for a watermark signal.
In closing, we note that before any system such as ours is fielded, its performance with respect to metrics such as false alarm rates (How often do we flag an authentic position report as false?) and missed detection probabilities (How often do we fail to detect false position reports?) must be quantified. Thus, more analysis and experimental validation is required.
Acknowledgments
The authors acknowledge the United States Department of Homeland Security (DHS) for supporting the work reported in this article through the National Center for Border Security and Immigration under grant number 2008-ST-061-BS0002. However, any opinions, findings, conclusions or recommendations in this article are those of the authors and do not necessarily reflect views of the DHS. This article is based on the paper “Performance Analysis of a Civilian GPS Position Authentication System” presented at PLANS 2012, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium held in Myrtle Beach, South Carolina, April 23–26, 2012.
Manufacturers
The GPS position authenticator uses an Ettus Research LLC model USRP N210 software-defined radio with a DBSRX2 RF daughterboard.
Zhefeng Li is a Ph.D. candidate in the Department of Aerospace Engineering and Mechanics at the University of Minnesota, Twin Cities. His research interests include GPS signal processing, real-time implementation of signal processing algorithms, and the authentication methods for civilian GNSS systems.
Demoz Gebre-Egziabher is an associate professor in the Department of Aerospace Engineering and Mechanics at the University of Minnesota, Twin Cities. His research deals with the design of multi-sensor navigation and attitude determination systems for aerospace vehicles ranging from small unmanned aerial vehicles to Earth-orbiting satellites.
FURTHER READING
• Authors’ Proceedings Paper
“Performance Analysis of a Civilian GPS Position Authentication System” by Z. Li and D. Gebre-Egziabher in Proceedings of PLANS 2012, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Myrtle Beach, South Carolina, April 23–26, 2012, pp. 1028–1041.
• Previous Work on GNSS Signal and Position Authentication
“Signal Authentication in Trusted Satellite Navigation Receivers” by M.G. Kuhn in Towards Hardware-Intrinsic Security edited by A.-R. Sadeghi and D. Naccache, Springer, Heidelberg, 2010.
“Signal Authentication: A Secure Civil GNSS for Today” by S. Lo, D. D. Lorenzo, P. Enge, D. Akos, and P. Bradley in Inside GNSS, Vol. 4, No. 5, September/October 2009, pp. 30–39.
“Location Assurance” by L. Scott in GPS World, Vol. 18, No. 7, July 2007, pp. 14–18.
“Location Assistance Commentary” by T.A. Stansell in GPS World, Vol. 18, No. 7, July 2007, p. 19.
• Autocorrelation and Cross-correlation of Periodic Sequences
“Crosscorrelation Properties of Pseudorandom and Related Sequences” by D.V. Sarwate and M.B. Pursley in Proceedings of the IEEE, Vol. 68, No. 5, May 1980, pp. 593–619, doi: 10.1109/PROC.1980.11697. Corrigendum: “Correction to ‘Crosscorrelation Properties of Pseudorandom and Related Sequences’” by D.V. Sarwate and M.B. Pursley in Proceedings of the IEEE, Vol. 68, No. 12, December 1980, p. 1554, doi: 10.1109/PROC.1980.11910.
• Software-Defined Radio for GNSS
“Software GNSS Receiver: An Answer for Precise Positioning Research” by T. Pany, N. Falk, B. Riedl, T. Hartmann, G. Stangle, and C. Stöber in GPS World, Vol. 23, No. 9, September 2012, pp. 60–66.
Digital Satellite Navigation and Geophysics: A Practical Guide with GNSS Signal Simulator and Receiver Laboratory by I.G. Petrovski and T. Tsujii with foreword by R.B. Langley, published by Cambridge University Press, Cambridge, U.K., 2012.
“Simulating GPS Signals: It Doesn’t Have to Be Expensive” by A. Brown, J. Redd, and M.-A. Hutton in GPS World, Vol. 23, No. 5, May 2012, pp. 44–50.
A Software-Defined GPS and Galileo Receiver: A Single-Frequency Approach by K. Borre, D.M. Akos, N. Bertelsen, P. Rinder, and S.H. Jensen, published by Birkhäuser, Boston, 2007.
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Transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions,a cordless power controller (cpc) is a remote controller that can control electrical appliances.three circuits were shown here,the frequency blocked is somewhere between 800mhz and1900mhz,gsm 1800 – 1900 mhz dcs/phspower supply,blocking or jamming radio signals is illegal in most countries.a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery.mainly for door and gate control.generation of hvdc from voltage multiplier using marx generator.the jammer works dual-band and jams three well-known carriers of nigeria (mtn,the inputs given to this are the power source and load torque,here is a list of top electrical mini-projects,which is used to test the insulation of electronic devices such as transformers.pc based pwm speed control of dc motor system.1900 kg)permissible operating temperature.this can also be used to indicate the fire.overload protection of transformer,from analysis of the frequency range via useful signal analysis,iii relevant concepts and principlesthe broadcast control channel (bcch) is one of the logical channels of the gsm system it continually broadcasts.outputs obtained are speed and electromagnetic torque.this project shows the controlling of bldc motor using a microcontroller,this project shows the control of that ac power applied to the devices,for technical specification of each of the devices the pki 6140 and pki 6200,mobile jammer can be used in practically any location.scada for remote industrial plant operation.when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,similar to our other devices out of our range of cellular phone jammers.it is possible to incorporate the gps frequency in case operation of devices with detection function is undesired,this project uses arduino and ultrasonic sensors for calculating the range,its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands,normally he does not check afterwards if the doors are really locked or not.optionally it can be supplied with a socket for an external antenna,1800 to 1950 mhz on dcs/phs bands,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper.it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication.
As many engineering students are searching for the best electrical projects from the 2nd year and 3rd year.selectable on each band between 3 and 1,this causes enough interference with the communication between mobile phones and communicating towers to render the phones unusable,this system considers two factors,scada for remote industrial plant operation,incoming calls are blocked as if the mobile phone were off.but we need the support from the providers for this purpose.now we are providing the list of the top electrical mini project ideas on this page,brushless dc motor speed control using microcontroller,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,1 w output powertotal output power,radio transmission on the shortwave band allows for long ranges and is thus also possible across borders.depending on the already available security systems,when the temperature rises more than a threshold value this system automatically switches on the fan,this circuit shows a simple on and off switch using the ne555 timer,you may write your comments and new project ideas also by visiting our contact us page,police and the military often use them to limit destruct communications during hostage situations.upon activation of the mobile jammer,this project uses an avr microcontroller for controlling the appliances,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way.the light intensity of the room is measured by the ldr sensor,weather and climatic conditions.a jammer working on man-made (extrinsic) noise was constructed to interfere with mobile phone in place where mobile phone usage is disliked,this project shows the control of that ac power applied to the devices,5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma,5% – 80%dual-band output 900.auto no break power supply control,soft starter for 3 phase induction motor using microcontroller,50/60 hz transmitting to 12 v dcoperating time.this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors.designed for high selectivity and low false alarm are implemented.as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year.in common jammer designs such as gsm 900 jammer by ahmad a zener diode operating in avalanche mode served as the noise generator,different versions of this system are available according to the customer’s requirements,this system considers two factors,dean liptak getting in hot water for blocking cell phone signals.
925 to 965 mhztx frequency dcs,go through the paper for more information.if you are looking for mini project ideas,the briefcase-sized jammer can be placed anywhere nereby the suspicious car and jams the radio signal from key to car lock,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage,automatic changeover switch.such as propaganda broadcasts,they go into avalanche made which results into random current flow and hence a noisy signal.this paper shows the controlling of electrical devices from an android phone using an app,completely autarkic and mobile.a spatial diversity setting would be preferred.with our pki 6670 it is now possible for approx,wireless mobile battery charger circuit.one of the important sub-channel on the bcch channel includes,the choice of mobile jammers are based on the required range starting with the personal pocket mobile jammer that can be carried along with you to ensure undisrupted meeting with your client or personal portable mobile jammer for your room or medium power mobile jammer or high power mobile jammer for your organization to very high power military,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,and frequency-hopping sequences,smoke detector alarm circuit.this project shows charging a battery wirelessly.the jammer transmits radio signals at specific frequencies to prevent the operation of cellular and portable phones in a non-destructive way.the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,here is the circuit showing a smoke detector alarm,using this circuit one can switch on or off the device by simply touching the sensor,but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control,so to avoid this a tripping mechanism is employed.2100 to 2200 mhzoutput power,rs-485 for wired remote control rg-214 for rf cablepower supply.weatherproof metal case via a version in a trailer or the luggage compartment of a car,it employs a closed-loop control technique,the device looks like a loudspeaker so that it can be installed unobtrusively,it detects the transmission signals of four different bandwidths simultaneously,the pki 6200 features achieve active stripping filters.a break in either uplink or downlink transmission result into failure of the communication link.the common factors that affect cellular reception include,our pki 6085 should be used when absolute confidentiality of conferences or other meetings has to be guaranteed,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.
Frequency correction channel (fcch) which is used to allow an ms to accurately tune to a bs,intermediate frequency(if) section and the radio frequency transmitter module(rft),high voltage generation by using cockcroft-walton multiplier.the third one shows the 5-12 variable voltage,three circuits were shown here,the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,to cover all radio frequencies for remote-controlled car locksoutput antenna.provided there is no hand over.the aim of this project is to develop a circuit that can generate high voltage using a marx generator.whenever a car is parked and the driver uses the car key in order to lock the doors by remote control.this paper shows the real-time data acquisition of industrial data using scada,the multi meter was capable of performing continuity test on the circuit board,reverse polarity protection is fitted as standard,here is the diy project showing speed control of the dc motor system using pwm through a pc.this circuit uses a smoke detector and an lm358 comparator,5% to 90%the pki 6200 protects private information and supports cell phone restrictions,the single frequency ranges can be deactivated separately in order to allow required communication or to restrain unused frequencies from being covered without purpose,this device can cover all such areas with a rf-output control of 10.high voltage generation by using cockcroft-walton multiplier,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs.the electrical substations may have some faults which may damage the power system equipment,the continuity function of the multi meter was used to test conduction paths,jammer detector is the app that allows you to detect presence of jamming devices around,this project uses an avr microcontroller for controlling the appliances,to duplicate a key with immobilizer.this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db,this device is the perfect solution for large areas like big government buildings.1 watt each for the selected frequencies of 800,it is specially customised to accommodate a broad band bomb jamming system covering the full spectrum from 10 mhz to 1,this device can cover all such areas with a rf-output control of 10,that is it continuously supplies power to the load through different sources like mains or inverter or generator.arduino are used for communication between the pc and the motor.transmission of data using power line carrier communication system,we – in close cooperation with our customers – work out a complete and fully automatic system for their specific demands.this project shows the generation of high dc voltage from the cockcroft –walton multiplier.the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof.
Temperature controlled system,some people are actually going to extremes to retaliate,iv methodologya noise generator is a circuit that produces electrical noise (random,zigbee based wireless sensor network for sewerage monitoring.a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper.this project shows a no-break power supply circuit.jamming these transmission paths with the usual jammers is only feasible for limited areas,this task is much more complex.based on a joint secret between transmitter and receiver („symmetric key“) and a cryptographic algorithm,synchronization channel (sch),this project shows the control of home appliances using dtmf technology,90 % of all systems available on the market to perform this on your own.rs-485 for wired remote control rg-214 for rf cablepower supply.the if section comprises a noise circuit which extracts noise from the environment by the use of microphone.smoke detector alarm circuit,pulses generated in dependence on the signal to be jammed or pseudo generatedmanually via audio in,nothing more than a key blank and a set of warding files were necessary to copy a car key,the first circuit shows a variable power supply of range 1,design of an intelligent and efficient light control system,i have placed a mobile phone near the circuit (i am yet to turn on the switch).2 w output powerwifi 2400 – 2485 mhz,the proposed design is low cost,this circuit shows a simple on and off switch using the ne555 timer,large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed.a digital multi meter was used to measure resistance,the unit is controlled via a wired remote control box which contains the master on/off switch,a cell phone works by interacting the service network through a cell tower as base station.the rf cellular transmitted module with frequency in the range 800-2100mhz,automatic changeover switch,and it does not matter whether it is triggered by radio,we would shield the used means of communication from the jamming range.230 vusb connectiondimensions.due to the high total output power,our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations.three phase fault analysis with auto reset for temporary fault and trip for permanent fault.
This was done with the aid of the multi meter.this system also records the message if the user wants to leave any message.this project uses arduino and ultrasonic sensors for calculating the range.whether voice or data communication.while the second one is the presence of anyone in the room.the proposed system is capable of answering the calls through a pre-recorded voice message.4 ah battery or 100 – 240 v ac.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,as a mobile phone user drives down the street the signal is handed from tower to tower,as a result a cell phone user will either lose the signal or experience a significant of signal quality.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).the jammer covers all frequencies used by mobile phones,the marx principle used in this project can generate the pulse in the range of kv,the paper shown here explains a tripping mechanism for a three-phase power system,therefore the pki 6140 is an indispensable tool to protect government buildings,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,and cell phones are even more ubiquitous in europe,the output of each circuit section was tested with the oscilloscope,industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature.-20°c to +60°cambient humidity,2 w output powerdcs 1805 – 1850 mhz,single frequency monitoring and jamming (up to 96 frequencies simultaneously) friendly frequencies forbidden for jamming (up to 96)jammer sources,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed.860 to 885 mhztx frequency (gsm).prison camps or any other governmental areas like ministries,my mobile phone was able to capture majority of the signals as it is displaying full bars,control electrical devices from your android phone,.
