Recent trends in Interference Mitigation and Spoofing Detection ! - PowerPoint PPT Presentation

Recent trends in Interference Mitigation and Spoofing Detection ! Fabio Dovis ! Electronics Dept., Politecnico di Torino, Italy ! !"#$%&''()*++,(-./0121,(3*4*54)*++(

Outline • ! GNSS vulnerabilities • ! Classification of interfering sources • ! Interference monitoring ! ! Quality assessment procedure ! ! Interference effects • ! Interference detection techniques • ! Interference mitigation • ! Conclusions Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Outline • ! GNSS vulnerabilities • ! Classification of interfering sources • ! Interference monitoring ! ! Quality assessment procedure ! ! Interference effects • ! Interference detection techniques • ! Interference mitigation • ! Conclusions Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

GNSS background: signal structure • ! GPS signal structure ! ! two radio frequency (RF) links: L1, 1575.42 MHz, and L2, 1227.60 MHz. ! ! Direct Sequence Spread Spectrum (DSSS) based on PRN codes: ! ! C/A code (1023 bits repeated each ms, chipping rate equal to 1.023 Ranging MHz) code ! ! P code (repeated after one week, chipping rate equal to 10.23 MHz) ! ! Navigation data (50 bps, bit duration of 20 ms) • ! GPS modernization ! ! Innovative M-Code for military applications ! ! New carrier L5 for civil user (SoL) ! ! New civil L2CS code on L2 • ! Galileo signal structure: ! ! Composite BOC (CBOC) modulation on E1 ! ! AltBOC on E5a/E5b Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

GNSS background: the receiver • ! The receivers operations can be grouped in four main functions: ! ! Antenna and front-end processing ! ! Acquisition/Alignment ! ! Tracking • ! code tracking • ! phase tracking ! ! Demodulation and position estimation Acquisition Acquisition Acquisition Acquisition Tracking stage Acquisition stage Tracking stage IF Filters/ stage Tracking stage stage Tracking stage RF stage ADC/AGC stage Tracking stage NAV Unit stage Amp Carrier & Position Digital Local Carrier & Code Code oscillato conversion tracking Velocity r correlator Time Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

GNSS vulnerabilities • ! The performance in terms of position estimation accuracy, reliability and service continuity depend on the ability of the receiver to acquire the GNSS Signal in Space (SIS) and to keep it tracked. 6172.8.9:;(:<(=>1(;.?@7.9:;(A@7;.B( ( ! ! Evil Waveforms ! ! Multipath ! direct reflected signal ! signal ! d ! ! ! Spoofing direct direct reflected signal reflected ! ! ! Interference signal signal ! signal High level spoofing attack classification 1 d Excess path (red) of the reflected signal Potential Interference sources in GPS 1 T. E. Humphreys, B. M. Levina, B. W. O’Hanlon, P. M. Kintner, d Excess path (red) of the reflected signal “Assessing the spoofing threat”, GPS World, January 2009 and Galileo bands Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

GNSS signal power Received signal power extremely low: Min. received power: - ! GPS L1 C/A code: -158.5 dBW - ! Galileo E1: -157dBW - ! No visible signal using conventional antennas and receiving hardware - ! The lobe in the spectrum results from the combined signal power received by all the satellites in view - ! The robustness of GPS signal derives from the spread spectrum nature of the transmitted signal (Direct Sequence Spread Spectrum); - ! Although the DSSS signal structure, navigation receivers are vulnerable to (strong) interfering signals, that might prevent the correct signal processing. Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Code Division Multiple Access RECEIVER INPUT SIGNAL • ! The CDMA is robust to the presence of INTERFERING interfering signals SIGNAL SS SIGNAL No • ! The despreading B s f operation made at the B ss receiver spreads the SIGNAL AFTER THE DESPREADING power of the interfering signal over a wide USEFUL SIGNAL bandwidth INTERFERING SIGNAL No B s f B ss Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Outline • ! GNSS vulnerabilities • ! Classification of interfering sources • ! Interference monitoring ! ! Quality assessment procedure ! ! Interference effects • ! Interference detection techniques • ! Interference mitigation • ! Conclusions Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Interference in GNSS receivers • ! RFI can partially or totally compromise the correct receiver behavior (e. g. They can saturate first stages of the receiver chain or lead to erroneous position estimation); !;=1;9:;.B(CD!( ! ! &:=(:;BE(21B.=18(=:(.(/@B@=.2E( L;@;=1;9:;.B(CD!( F:;=1G=H( ! ! MK=(:<(N.;84@;(N.;8(( ! ! &1I(.J1;9:;(<:2(F://12F@.B( >.2/:;@FAH( .;8(A1FK2@=E(:2@1;=18(%&''( .00B@F.9:;AH(( GNSS Jammer Intentional RFI can be used to inhibit the tracking stage in order to force the receiver status in the re-acquisition mode Spoofing attacks are facilitated Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Interference classification • ! Interference can be further classified according to the spectral and time features w.r.t. the GNSS signal ! ! Continuos wave: pure tone ! ! Narrow Band interference: B << B I GNSS ! ! Wide band Interference B ! B I GNSS ! ! Pulsed Interference Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Unintentional interference Interference Type Telecommunication Systems GNSS Bands Distance Measuring Equipment (DME) Tactical Air Navigation (TACAN) Secondary Surveillance Radar (SSR) Aeronautical Galileo E5a E5b Multifunction Information Distribution System (MIDS) Communication Joint Tactical Information Distribution System (JTDS) GPS L5 Systems Traffic Collision and Avoidance System (TCAS) Identity Friend and Foe (IFF) Automatic Dependent Surveillance-Broadcast (ADS-B) Air Traffic Control radar Galileo E6 Radar GPS L2 Solid State radar Satellite Communication Mobile Satellite Service (MSS) close to GPS L1 Systems TV Channels Galileo E1 Secondary harmonics Digital Video Broadcasting – Terrestrial (DVB-T) GPS L1 Digital Video Broadcasting (DAB) Personal Electronic Device (PED) Others all VHF Omni-direction Range (VOR) and Instrument Landing System (ILS) harmonics Ultra Wide Band (UWB) Systems Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Example: Interference from DVB-T and analog TV Real Case: secondary harmonics from DVB-T might fall in the bands of interest: Torino Eremo : DVB-T Channel 28 and 66; o ! modulation: 16 QAM for Ch 28 and o ! 64 QAM for Ch 66; ERP: 200 W for Ch 28 and 3000 W o ! for Ch (66); Central frequency: 530 MHz for Ch o ! 28 and 834 MHz for Ch 66 In the broadcast TV signal, VHF and UHF bands are used. Both bands, in their sub channels, could represent interferences sources for a GNSS receiver Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Example: Interference from DVB-T and analog TV 6.54 Km ! 6.32 Km ! 3.95 Km ! 1.557 GHz 350 m ! NavSAS Lab Murazzi Pecetto 1.602 GHz 1.3 Km ! 1.557 GHz 1.58 Km ! 1.557 GHz 1.602 GHz 3.88 Km ! GPS L1 GPS L1 GPS L1 Other transmitting antennas Galileo E1 Galileo E1 Galileo E1 on the VHF and UHF bands Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Example: Wideband interference • ! Test conducted in Torino aimed to assess the impact of intentional interference on commercial receivers ! ! PSA/ESA Spectrum Analyzer (E4402B) PSA/ESA Spectrum Analyzer (E4402B) 1 2 Monitoring Vehicle Unit -8,218E+00 -1,209E+01 -1,822E+01 -2,822E+01 (MVU) -3,209E+01 dBm -3,822E+01 dBm -4,822E+01 -5,209E+01 -5,822E+01 -6,822E+01 -7,209E+01 -7,822E+01 -8,822E+01 -9,209E+01 1,54E+ 1,55E+ 1,56E+ 1,57E+ 1,58E+ 1,59E+ 1,60E+ 1,61E+ 1,54E+ 1,55E+ 1,56E+ 1,57E+ 1,58E+ 1,59E+ 1,60E+ 1,61E+ 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 Frequency (Hz) Frequency (Hz) ! ! PSA/ESA Spectrum Analyzer (E4402B) PSA/ESA Spectrum Analyzer (E4402B) 3 4 -1,214E+01 -1,135E+01 -3,135E+01 -3,214E+01 dBm dBm -5,214E+01 -5,135E+01 -7,214E+01 -7,135E+01 -9,214E+01 -9,135E+01 1,54E+ 1,55E+ 1,56E+ 1,57E+ 1,58E+ 1,59E+ 1,60E+ 1,61E+ 1,54E+ 1,55E+ 1,56E+ 1,57E+ 1,58E+ 1,59E+ 1,60E+ 1,61E+ 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 Frequency (Hz) Frequency (Hz) Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Example: Pulsed Interference Distance Measuring Equipment Airborne interrogator Ground beacon Pulse width=3.5 ! s Inter Pulse Period=12 ! s Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !

Intentional interference • ! Jamming’s objective is denial of navigation service by masking GPS signals with noise. Under jamming attack the victim receiver is unable to acquire and process navigation signals. • ! Signal radiation on the GNSS bands is not legal, jamming attacks are detectable, but... low cost jammers can be easily purchased on the web Severe threat for liability-critical mass-market applications, such as GNSS-based road tolling or fleet management Navigation, Signal Analysis and Simulation Group ! ICL-GNSS 2011 !