Time-hopping (TH) is a communications signal technique which can be used to achieve
anti-jamming
Electronic counter-countermeasures (ECCM) is a part of electronic warfare which includes a variety of practices which attempt to reduce or eliminate the effect of electronic countermeasures (ECM) on electronic sensors aboard vehicles, ships and ...
(AJ) or
low probability of intercept
A low-probability-of-intercept radar (LPIR) is a radar employing measures to avoid detection by passive radar detection equipment (such as a radar warning receiver (RWR), or electronic support receiver) while it is searching for a target or engag ...
(LPI). It can also refer to
pulse-position modulation, which in its simplest form employs 2
k discrete pulses (referring to the unique positions of the pulse within the transmission window) to transmit k bit(s) per pulse.
Details
To achieve LPI, the transmission time is changed randomly by varying the period and duty cycle of the pulse (carrier) using a pseudo-random sequence. The transmitted signal will then have intermittent start and stop times. Although often used to form hybrid
spread-spectrum
In telecommunication and radio communication, spread-spectrum techniques are methods by which a signal (e.g., an electrical, electromagnetic, or acoustic signal) generated with a particular bandwidth is deliberately spread in the frequency doma ...
(SS) systems, TH is strictly speaking a non-SS technique. Spreading of the spectrum is caused by other factors associated with TH, such as using pulses with low duty cycle having a wide frequency response. An example of hybrid SS is TH-FHSS or hybrid TDMA (time division multiple access).
See also
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Spread spectrum
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Frequency-hopping spread spectrum
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Direct-sequence spread spectrum
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Ultra-wideband
References
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External links
"Time hopping and frequency hopping in ultrawideband systems"
Channel access methods
Wireless locating
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