Communication intelligence COMINT
The interception and analysis of the radio communications is the main application of COMINT systems.
COMINT (Communication Intelligence) is the interception and analysis of all electromagnetic signals used to send information from point A to point B (B may be multiple).
The study and analysis of communication signals break down into several levels of study:
- The study of the carrier signal with the objective of decoding the signal that means to transform an electromagnetic signal into an actionable information (sound, image, data etc.).
The result of the signal study is described in a database in order to capitalize on the knowledge gained. This database will be very important for electronic warfare to allow it to identify the frequencies and types of modulation used by communication networks.
The vast majority of analyses do not go beyond this stage, either because the content is of no interest, or because it is encrypted and deciphering is not a priority, or because the signal is already identified.
Even if the content is not exploited, the type of transmission already gives a certain amount of information (origin and recipient, volume of data, etc.) of interest to the intelligence.
For example, a significant increase in transmissions can give an indication of a particular military activity and allows anticipating events.
- The study of the binary trains for digital transmissions with the aim being to determine data packets, codes, addresses. While data themselves can be encrypted, it is not always the case for headers or addresses that can provide the identity of the transmitter and receiver. This step is a prerequisite before the deciphering of a message.
- The decryption of the data: the huge computing power and the amount of time needed limit the decryption to only a small portion of the encrypted transmissions.
The contents of the transmissions, once available, are passed on to analysts who will extract information from the contents.
The operations are not limited to military ones, as homeland security and police investigations claim the same intelligence gathering. In fact, just as an example, the shipborne COMINT is used for missions like the following:
- Self-defence and/or protection of High Value Units
- Patrolling of enemy coast to prepare the land phase of the forces;
- Protection of commercial naval routes from piracy (Protection of Shipping)
- Support to Police Operations in counter-narcotics operation or against illegal armed groups.
The information gathering addresses the radio communication activities aims to catch both the RF parameters, like the carriers’ frequency, the bandwidths and the modulation types, and the information exchanged between the users or terminals, just relying on the intercepted communications.
Concerning the RF parameters (the physical level of the radio link), the “Signal-In-Space” (SIS) includes the timing and the frequency characteristic of the aerial transmitted signal.
The SIS, at the source, mathematically defines the formal time-depending function representing the theoretical signal an emitter should transmit.
The SIS provides also the emitter with a fingerprint of the transmitted signal.
The evolution of the radio communications pushed the above RF parameters to more complex structures adopting protocol level structures and the relevant networking information, that’s what is currently defined as “waveform”, being it either a wireless communication standard or a legacy radio access technology.
About the information exchanged by the end users, its acquisition cannot be generally performed in real-time, as the waveform’s protocol recognition and mainly the data encryption require a highly intensive digital processing to be performed on post-processing off-line only.
In addition, the encryption algorithm and the related key become generally available just after an intensive intelligence operation. In summary, a conventional COMINT system has to perform the following main functions:
- Surveillance of the electromagnetic spectrum:
- fast warning on known or unknown threatening emitters;
- complete “situation awareness”; detection and localization of all interesting emitters (not only threats)
- Intelligence collection
- Access to the communication content (demodulation, decoding, audio listening for voice signals with analog modulations)
- deep analysis of single emitters to estimate the technical parameters
- extensive data collection capability (recording, for further analysis).
Generally, a COMINT system does not perform the Direction Finding associated to the detected radio emissions with their own primary parameters (carriers’ frequency and the bandwidths). However, the deployment of a COMINT near to tactical condition push the users to require also the DF capability.
This latter capability is integrated with the traditional analysis subsystem, where all the functions associated to monitoring are performed (technical identification, classification, demodulation, decoding, audio listening, WB and NB recording).
Overall, a state-of-art COMINT provides the users with the following capabilities in the frequency range: at least covering VHF and UHF bands, e.g. 30 ÷ 6000 MHz and with some missions, operated with specific platforms like naval ones, extending the frequency coverage down to the HF band (1 ÷30 MHz).
- Detection and DF of communication emissions;
- High accuracy measurement of electromagnetic parameters of intercepted emitters (frequency, bandwidth, DOA, amplitude);
- High sensitivity;
- Full azimuth coverage;
- Automatic track synthesis and picture compilation;
- Localization of selected emitters;
- Generation of automatic alerts;
- Classification (modulation recognition);
- Access to communication signal content (Demodulation & decoding, audio listening);
- Technical identification (communication waveform/protocol recognition) of intercept emitters on the basis of “EW Library”;
- Extensive Data Recording (NB, of selected emitters) and WB (I/Q data of the entire IBW)
- Support for Offline “deep” technical analysis by Playback.
Competitive COMINT products perform the above capabilities also against large IBW signals generated by very short bursts and fast FH emitters. This further requirement encompasses a wide BW dynamic, including military, professional (e.g. narrow band standards like TETRA and APCO P25) and commercial mobile communications.
The off-line analysis is the item that offers an extensive growth capability, as it allows the operator to program it autonomously in order to expand the set of supported waveforms (or new decoders, as sometime they are called).