| 1. |
- Axell, Erik, et al.
(författare)
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Jamming Detection in GNSS Receivers: Performance Evaluation of Field Trials
- 2015
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Ingår i: Navigation. - : Institute of Navigation. - 0028-1522 .- 2161-4296. ; 62:1, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate the detection performance of several commercial interference detectors and of a detector that uses the automatic gain control (AGC) level as a test statistic. The evaluations are based on actual measurements of GPS signals and different types of jamming signals, and were performed at the Vidsel test range in northern Sweden.The AGC detector and the Chronos CTL-3500 were shown to work well for all types of jamming signals. The J-alert was able to detect a wideband (20 MHz) signal but not the narrow band (<2 MHz) signals. By contrast, the jamming indicator on a Ublox 6H receiver was only able to detect a slowly varying modulated CW signal, but not signals with larger bandwidth (>2 MHz). We confirmed that C/N0-based Android application detectors could work well in static scenarios but are not suitable in dynamic scenarios, since they cannot distinguish between decreased GPS signal strength and increased interference
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| 2. |
- Mohammed, Abbas, et al.
(författare)
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Novel Signal Processing Techniques for Detecting and Minimizing Skywave Interference in Loran-C Receivers
- 1999
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Ingår i: Navigation. - 0028-1522. ; 46:3, s. 147-159
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Tidskriftsartikel (refereegranskat)abstract
- Adaptive skywave estimation techniques that can monitor the delays and strengths of skywave components in real time are desirable in Loran-C receivers since they allow optimal sampling points to be selected. Such techniques should enable the receiver to minimize the errors due to skywave interference while maximizing signal-to-noise and signal-to-interference ratios. This paper reports on novel signal processing techniques employing classical Fourier analysis and modern high-resolution algorithms for identifying skywaves and measuring their delays. The benefits of these methods are assessed, together with the cost in computing resources of implementing them in receivers. The paper includes theoretical analysis, computer simulations, and the results of tests using off-air signals. A prototype Loran-C system employing the proposed techniques is described
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| 3. |
- Psiaki, M.L, et al.
(författare)
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A comparison of direct radio frequency sampling and conventional GNSS receiver architectures
- 2005
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Ingår i: Navigation. - : Institute of Navigation. - 0028-1522 .- 2161-4296. ; 52:2, s. 71-81
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Tidskriftsartikel (refereegranskat)abstract
- The novel concept of a direct radio frequency (RF) sampling receiver front end was analyzed, experimentally tested, and compared with a traditional superheterodyne front end that uses mixing to downconvert the signal before sampling. This study's goal was to demonstrate that signal power and phase are not adversely influenced by the use of direct RF sampling. The direct RF sampling strategy examined in this work uses sampling rates that are much lower than the carrier frequency but more than twice the signal bandwidth. Such a system employs a bandpass filter in front of the analog-to-digital converter (ADC) to avoid sensitivity loss via aliasing of out-of-band noise and interfering signals. This design approach was evaluated analytically to determine the effects of sample clock jitter, and experimental results using GPS signals were used to confirm the analytical results. The results indicate that direct RF sampling yields performance equivalent to that of superheterodyne mixing
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| 4. |
- Stenberg, Niklas, et al.
(författare)
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Results on GNSS Spoofing Mitigation Using Multiple Receivers
- 2022
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Ingår i: Navigation. - : Inst Navigation - ION. - 0028-1522 .- 2161-4296. ; 69:1
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Tidskriftsartikel (refereegranskat)abstract
- GNSS receivers are vulnerable to spoofing attacks in which false satellite signals deceive receivers to compute false position and/or time estimates. This work derives and evaluates algorithms that perform spoofing mitigation by utilizing double differences of pseudorange or carrier phase measurements from multiple receivers. The algorithms identify pseudorange and carrier-phase measurements originating from spoofing signals, and omit these from the position and time computation. The algorithms are evaluated with simulated and live-sky meaconing attacks. The simulated spoofing attacks show that mitigation using pseudoranges is possible in these tests when the receivers are separated by five meters or more. At 20 meters, the pseudorange algorithm correctly authenticates six out of seven pseudoranges within 30 seconds in the same simulator tests. Using carrier phase allows mitigation with shorter distances between receivers, but requires better time synchronization between the receivers. Evaluations with live-sky meaconing attacks show the validity of the proposed mitigation algorithms.
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