Time-hopping

Time-hopping is a communications signal technique which can be used to achieve anti-jamming or low-probability-of-intercept. It can also refer to pulse-position modulation, which in its simplest form employs 2^k discrete pulses to transmit k bit per pulse.

Details

To achieve LPI, the transmission time is changed randomly by varying the period and duty cycle of the pulse using a pseudo-random sequence. The transmitted signal will then have intermittent start and stop times. Although often used to form hybrid spread-spectrum 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.