Time-hopping (TH) is a communications signal technique which can be used to achieve
anti-jamming (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 enga ...
(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 do ...
(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
*
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 d ...
*
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 ...
*
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 ...
*
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
*
External links
"Time hopping and frequency hopping in ultrawideband systems"
Channel access methods
Wireless locating
{{tech-stub