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2) Uninformed interference: that comprises intentional transmission of signals at or
near the signal frequencies in question, but without the desire to cause harm; and
3) Accidental interference: that includes unintentional transmissions appearing at or
near the signal frequencies in question, typically from malfunctions.
Jamming is defined as the blocking of the reception of radio frequency signals, by
deliberately emitting electromagnetic radiation to disrupt user receivers by reducing
the signal to noise level [49]. In severe cases, jamming can lead to loss of signal tracking
altogether.
Detection of interference signals is typically done by monitoring the received signal
or automatic gain control (AGC) levels, with advanced signal processing in the radio
front‐end, by monitoring signal strengths, cross‐checking against other signals and by
monitoring the digitized signal levels [73]. Localization techniques of interference signals can be divided into four groups, according to the type of technology used [9]:
1) received signal strength techniques;
2) time of arrival techniques;
3) frequency techniques; and
4) phase and interferometry techniques.
Angle of arrival (AOA)‐based geolocation techniques are suitable for all RFI types,
but have high implementation complexity since they require phase/gain calibration
of antenna array elements. AOA‐based localization performance depends on the RFI
bandwidth [9]. Time difference of arrival (TDOA)‐based localization is suitable for
wideband RFI and has low implementation complexity, but requires precise timing
synchronization between sensor nodes [9]. Frequency difference of arrival (FDOA)‐
based techniques are best for narrowband RFI and require either the RFI or the
detecting and locating sensor node to be moving, as well as both precise timing and
frequency synchronization between the sensor nodes. Received signal strength
(RSS)‐based localization is suitable for all types of RFI and has very low complexity.
However, RSS‐based methods work poorly in sparse networks since performance
degrades with distance.
13.8.3 Backup Systems
As now being included in 5G techniques, the digital broadcasting systems are able to be
considered as one of the backup systems to enhance the security in wireless communication or radio navigation systems. Recently, digital broadcasting systems, such as the
Digital Video Broadcasting (DVB), Digital Audio Broadcasting (DAB), and the Advanced
Television Systems Committee (ATSC) standards, have been widely suggested to be
used as an alternative information transmission technique [120]. The transmission
power of digital TV (DTV) is high and the frequency band of DTV signals is wide from
400 MHz to 900 MHz [62], which occupies over 40 channels with one channel having a
bandwidth of 8 MHz. It is common for one city to broadcast the DTV transmissions in
4 to 5 different channels, while the channels are sparsely allocated within all the DTV
channels. Considering the security aspect, such properties of the DTV signals make
the system more robust due to a wide bandwidth and multiple channels available in
one local area. Since DTV facilities are already in use and no more infrastructure
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2) Uninformed interference: that comprises intentional transmission of signals at or
near the signal frequencies in question, but without the desire to cause harm; and
3) Accidental interference: that includes unintentional transmissions appearing at or
near the signal frequencies in question, typically from malfunctions.
Jamming is defined as the blocking of the reception of radio frequency signals, by
deliberately emitting electromagnetic radiation to disrupt user receivers by reducing
the signal to noise level [49]. In severe cases, jamming can lead to loss of signal tracking
altogether.
Detection of interference signals is typically done by monitoring the received signal
or automatic gain control (AGC) levels, with advanced signal processing in the radio
front‐end, by monitoring signal strengths, cross‐checking against other signals and by
monitoring the digitized signal levels [73]. Localization techniques of interference signals can be divided into four groups, according to the type of technology used [9]:
1) received signal strength techniques;
2) time of arrival techniques;
3) frequency techniques; and
4) phase and interferometry techniques.
Angle of arrival (AOA)‐based geolocation techniques are suitable for all RFI types,
but have high implementation complexity since they require phase/gain calibration
of antenna array elements. AOA‐based localization performance depends on the RFI
bandwidth [9]. Time difference of arrival (TDOA)‐based localization is suitable for
wideband RFI and has low implementation complexity, but requires precise timing
synchronization between sensor nodes [9]. Frequency difference of arrival (FDOA)‐
based techniques are best for narrowband RFI and require either the RFI or the
detecting and locating sensor node to be moving, as well as both precise timing and
frequency synchronization between the sensor nodes. Received signal strength
(RSS)‐based localization is suitable for all types of RFI and has very low complexity.
However, RSS‐based methods work poorly in sparse networks since performance
degrades with distance.
13.8.3 Backup Systems
As now being included in 5G techniques, the digital broadcasting systems are able to be
considered as one of the backup systems to enhance the security in wireless communication or radio navigation systems. Recently, digital broadcasting systems, such as the
Digital Video Broadcasting (DVB), Digital Audio Broadcasting (DAB), and the Advanced
Television Systems Committee (ATSC) standards, have been widely suggested to be
used as an alternative information transmission technique [120]. The transmission
power of digital TV (DTV) is high and the frequency band of DTV signals is wide from
400 MHz to 900 MHz [62], which occupies over 40 channels with one channel having a
bandwidth of 8 MHz. It is common for one city to broadcast the DTV transmissions in
4 to 5 different channels, while the channels are sparsely allocated within all the DTV
channels. Considering the security aspect, such properties of the DTV signals make
the system more robust due to a wide bandwidth and multiple channels available in
one local area. Since DTV facilities are already in use and no more infrastructure