Military Communications and Information Technology: A Trusted ...
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Military Communications and Information Technology: A Trusted ...

Military Communications and Information Technology: A Trusted ... Military Communications and Information Technology: A Trusted ...

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76 Military Communications and Information Technology... (Electronic Counter-Countermeasures) mechanisms which attempt to reduce or eliminate the effect of electronic jamming. In such case response time of jamming system can be longer, because usually the transmitted information does not directly affect on destroying equipment and killing people. Figure 1. RCIED jamming In order to provide effective protection against RCIED, the response to the emerging radio signals must be immediate and effective. Hence, there is no possibility of using sophisticated methods of signals detection and identification which are time consuming. Precise and fast response is needed. Duration of jamming transmission is dependent on the speed of a vehicle, which in a few dozen seconds could leave dangerous zone. If the jammer starts too late it might not protect against the signal that triggers the explosion. On the other hand a threat of an initiating signal is temporary because a convoy moves and passes possible place of IED installation. Then it is possible to switch off the jammer and continue searching for threats. Due to the fact that technical details and vulnerabilities of public transmission systems are known, it is not necessary to transmit continuously jamming signal. Jammer can disturb at least one third of the jammed signal in time or frequency domain to be effective [4]. It follows that only part of the time could be used for effective jamming, and remaining time can be utilized for target acquisition in different frequency bands. Moreover, military jamming systems are more complex than RCIED protection systems and with the exception of air platforms, mainly designed to work from a static outposts. In contrast, RCIED jamming systems are mounted on vehicles

Chapter 1: Concepts and Solutions for Communications and Information Systems 77 and work in constant motion. This affect on reducing the system power supply and as a result decreases protection zone. Significant impact on the effectiveness of jamming has type of devices used to trigger RCIED. It is easier to neutralize RCIEDs based on commercial solutions because there is knowledge of signals, their frequency, modulation which allows to define range of jamming in advance. A disadvantage is the unpredictability of the trigger method and a great variety of solutions. Easy access to such technology and low cost cause difficulties in monitoring such market to eliminate bomb planters. More sophisticated solutions to trigger RCIED, which use for example spread spectrum or multiband emissions, sometimes on unusual frequency ranges, are more difficult to detect and effectively jam. In article [1] possible transmission systems are mentioned which can be used to initiate ignition of main charge of an RCIED. Every transmission system has its own vulnerability to jamming. From documentation, measurements and experiments it can be assessed two timing parameters: maximum time to start jamming (delay time) and required duration of a jamming transmission to successfully block receiver. Maximum delay time is in the worst case less than 100 ms, what imposes requirements on the speed of threat detection. Required jamming duration to efficiently jam in a synchronized manner, the desired signal is varying from several μs to several dozen ms. Other way, 1÷30% of jammed signal duration is required depending on the transmission system. Analyzing possibilities for RCIED jamming system it is necessary to consider such aspects as: A. Receiver/detector capabilieties: • receiver tuning time (speed of synthesizer) and its accuracy; • dynamic range, required more than 90 dB; • resistance to high voltage on the input of a receiver (levels greater than +30 dBm); • sensitivity, should be close to requirements for a GSM handset at a much wider bandwidth; • tuning/switching/setting time of preselectors; • frequency range for searching a suspected signals; • quality A/D converters, required 16 bit resolution; • using appropriate time-frequency transform with matched resolution in time and frequency; • threat identification algorithm, required FPGA FFT implementation with DSP support; • time for frequency range analysis, shorter than maximum delay time to start jamming.

76 <strong>Military</strong> <strong>Communications</strong> <strong>and</strong> <strong>Information</strong> <strong>Technology</strong>...<br />

(Electronic Counter-Countermeasures) mechanisms which attempt to reduce or<br />

eliminate the effect of electronic jamming. In such case response time of jamming<br />

system can be longer, because usually the transmitted information does not directly<br />

affect on destroying equipment <strong>and</strong> killing people.<br />

Figure 1. RCIED jamming<br />

In order to provide effective protection against RCIED, the response to<br />

the emerging radio signals must be immediate <strong>and</strong> effective. Hence, there is no<br />

possibility of using sophisticated methods of signals detection <strong>and</strong> identification<br />

which are time consuming. Precise <strong>and</strong> fast response is needed. Duration of jamming<br />

transmission is dependent on the speed of a vehicle, which in a few dozen<br />

seconds could leave dangerous zone.<br />

If the jammer starts too late it might not protect against the signal that triggers<br />

the explosion. On the other h<strong>and</strong> a threat of an initiating signal is temporary<br />

because a convoy moves <strong>and</strong> passes possible place of IED installation. Then it is<br />

possible to switch off the jammer <strong>and</strong> continue searching for threats. Due to<br />

the fact that technical details <strong>and</strong> vulnerabilities of public transmission systems<br />

are known, it is not necessary to transmit continuously jamming signal. Jammer<br />

can disturb at least one third of the jammed signal in time or frequency domain to<br />

be effective [4]. It follows that only part of the time could be used for effective<br />

jamming, <strong>and</strong> remaining time can be utilized for target acquisition in different<br />

frequency b<strong>and</strong>s.<br />

Moreover, military jamming systems are more complex than RCIED protection<br />

systems <strong>and</strong> with the exception of air platforms, mainly designed to work from<br />

a static outposts. In contrast, RCIED jamming systems are mounted on vehicles

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