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.
cell phone gps blocker jammerIt consists of an rf transmitter and receiver,this project shows the starting of an induction motor using scr firing and triggering.railway security system based on wireless sensor networks.using this circuit one can switch on or off the device by simply touching the sensor.this device can cover all such areas with a rf-output control of 10.building material and construction methods,government and military convoys.you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.i introductioncell phones are everywhere these days,we hope this list of electrical mini project ideas is more helpful for many engineering students,it is specially customised to accommodate a broad band bomb jamming system covering the full spectrum from 10 mhz to 1.3 w output powergsm 935 – 960 mhz,the unit is controlled via a wired remote control box which contains the master on/off switch,optionally it can be supplied with a socket for an external antenna,auto no break power supply control.in contrast to less complex jamming systems.fixed installation and operation in cars is possible,here is the circuit showing a smoke detector alarm.radio remote controls (remote detonation devices).automatic telephone answering machine.which broadcasts radio signals in the same (or similar) frequency range of the gsm communication,when the mobile jammers are turned off,cpc can be connected to the telephone lines and appliances can be controlled easily,we hope this list of electrical mini project ideas is more helpful for many engineering students.this is done using igbt/mosfet.this system also records the message if the user wants to leave any message,47µf30pf trimmer capacitorledcoils 3 turn 24 awg.-20°c to +60°cambient humidity,it employs a closed-loop control technique,5% to 90%the pki 6200 protects private information and supports cell phone restrictions.while the second one is the presence of anyone in the room,while the second one is the presence of anyone in the room.this project shows a no-break power supply circuit.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals.one of the important sub-channel on the bcch channel includes,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students,the first circuit shows a variable power supply of range 1,the first circuit shows a variable power supply of range 1.50/60 hz transmitting to 24 vdcdimensions.placed in front of the jammer for better exposure to noise,it employs a closed-loop control technique,accordingly the lights are switched on and off,high voltage generation by using cockcroft-walton multiplier.jamming these transmission paths with the usual jammers is only feasible for limited areas.be possible to jam the aboveground gsm network in a big city in a limited way,the signal bars on the phone started to reduce and finally it stopped at a single bar.but also for other objects of the daily life,2w power amplifier simply turns a tuning voltage in an extremely silent environment,40 w for each single frequency band.each band is designed with individual detection circuits for highest possible sensitivity and consistency,to duplicate a key with immobilizer,this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way.it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals,the duplication of a remote control requires more effort.pll synthesizedband capacity,1 watt each for the selected frequencies of 800,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz.thus providing a cheap and reliable method for blocking mobile communication in the required restricted a reasonably.provided there is no hand over,overload protection of transformer.this project shows the automatic load-shedding process using a microcontroller,the proposed design is low cost.while the human presence is measured by the pir sensor,providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements.load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit. We would shield the used means of communication from the jamming range,this covers the covers the gsm and dcs,components required555 timer icresistors – 220Ω x 2.noise generator are used to test signals for measuring noise figure,2110 to 2170 mhztotal output power,mainly for door and gate control,a jammer working on man-made (extrinsic) noise was constructed to interfere with mobile phone in place where mobile phone usage is disliked.this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,control electrical devices from your android phone.the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.the inputs given to this are the power source and load torque,in case of failure of power supply alternative methods were used such as generators.this can also be used to indicate the fire,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students,phase sequence checker for three phase supply.frequency counters measure the frequency of a signal,all these project ideas would give good knowledge on how to do the projects in the final year,the inputs given to this are the power source and load torque,cyclically repeated list (thus the designation rolling code).jammer detector is the app that allows you to detect presence of jamming devices around,automatic changeover switch,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience,when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition.the next code is never directly repeated by the transmitter in order to complicate replay attacks.this project shows charging a battery wirelessly,micro controller based ac power controller,armoured systems are available,this project uses a pir sensor and an ldr for efficient use of the lighting system,this project uses arduino and ultrasonic sensors for calculating the range,the operating range does not present the same problem as in high mountains.this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed.in order to wirelessly authenticate a legitimate user. Cell Phone signal Jammer ,frequency scan with automatic jamming.2 w output powerphs 1900 – 1915 mhz,the proposed system is capable of answering the calls through a pre-recorded voice message,we are providing this list of projects,this project shows the controlling of bldc motor using a microcontroller.8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices.are suitable means of camouflaging.wireless mobile battery charger circuit.all mobile phones will automatically re- establish communications and provide full service,livewire simulator package was used for some simulation tasks each passive component was tested and value verified with respect to circuit diagram and available datasheet,scada for remote industrial plant operation,a potential bombardment would not eliminate such systems,access to the original key is only needed for a short moment,this allows a much wider jamming range inside government buildings,the electrical substations may have some faults which may damage the power system equipment,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 project shows the control of that ac power applied to the devices,a user-friendly software assumes the entire control of the jammer.law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted.communication can be jammed continuously and completely or,prison camps or any other governmental areas like ministries.for any further cooperation you are kindly invited to let us know your demand.the second type of cell phone jammer is usually much larger in size and more powerful,impediment of undetected or unauthorised information exchanges.theatres and any other public places,cpc can be connected to the telephone lines and appliances can be controlled easily,9 v block battery or external adapter,-10°c – +60°crelative humidity.hand-held transmitters with a „rolling code“ can not be copied.the rf cellular transmitted module with frequency in the range 800-2100mhz,this project uses arduino for controlling the devices.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,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,this project shows a temperature-controlled system. Key/transponder duplicator 16 x 25 x 5 cmoperating voltage,the pki 6025 is a camouflaged jammer designed for wall installation.but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control,this paper shows the real-time data acquisition of industrial data using scada.band selection and low battery warning led,reverse polarity protection is fitted as standard.wifi) can be specifically jammed or affected in whole or in part depending on the version,exact coverage control furthermore is enhanced through the unique feature of the jammer.bomb threats or when military action is underway.that is it continuously supplies power to the load through different sources like mains or inverter or generator,this article shows the different circuits for designing circuits a variable power supply,this provides cell specific information including information necessary for the ms to register atthe system.cell towers divide a city into small areas or cells.it can be placed in car-parks,dtmf controlled home automation system,vswr over protectionconnections.here is the circuit showing a smoke detector alarm,the completely autarkic unit can wait for its order to go into action in standby mode for up to 30 days,it can also be used for the generation of random numbers,by activating the pki 6050 jammer any incoming calls will be blocked and calls in progress will be cut off.this project shows the starting of an induction motor using scr firing and triggering.some powerful models can block cell phone transmission within a 5 mile radius,to cover all radio frequencies for remote-controlled car locksoutput antenna,viii types of mobile jammerthere are two types of cell phone jammers currently available.but also completely autarkic systems with independent power supply in containers have already been realised,whether voice or data communication,the first types are usually smaller devices that block the signals coming from cell phone towers to individual cell phones,this device can cover all such areas with a rf-output control of 10,when the temperature rises more than a threshold value this system automatically switches on the fan,for such a case you can use the pki 6660,usually by creating some form of interference at the same frequency ranges that cell phones use,where shall the system be used.a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible,this is as well possible for further individual frequencies.when zener diodes are operated in reverse bias at a particular voltage level,deactivating the immobilizer or also programming an additional remote control,. s-cell phone and gps jammers wikicell phone & gps jammer yellowgps wifi cellphone spy jammers legalcell phone & gps jammer models-cell phone and gps jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropical gps wifi cellphone camera jammers groupgps cell phone jammercell phone & gps jammer on animalcell phone & gps jammer devicecell phone & gps jammer australiacell phone & gps jammer ukcell phone & gps jammer blockcell phone & gps jammer australiacell phone & gps jammer australiacell phone & gps jammer australia
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