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 (LPI). It can also refer to
pulse-position modulation
Pulse-position modulation (PPM) is a form of signal modulation in which ''M'' message bits are encoded by transmitting a single pulse in one of 2^M possible required time shifts. This is repeated every ''T'' seconds, such that the transmitted bi ...
, 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 dom ...
(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
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 dom ...
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Frequency-hopping spread spectrum
Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. The changes are controlled by a code known to both tr ...
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Direct-sequence spread spectrum
In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. The direct-sequence modulation makes the transmitted signal wider in bandwidth than t ...
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Ultra-wideband
Ultra-wideband (UWB, ultra wideband, ultra-wide band and ultraband) is a radio technology that can use a very low energy level for short-range, high-bandwidth communications over a large portion of the radio spectrum. UWB has traditional applicati ...
References
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External links
"Time hopping and frequency hopping in ultrawideband systems"
Channel access methods
Wireless locating
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