Spread Spectrum
Spread spectrum is the deliberate spreading of energy over a band far wider than the transmitted information requires. The aim is not data rate but robustness: a narrowband interference source affects only a small part of the spread signal and the receiver recovers the information from the rest. Its two basic methods are frequency hopping and direct sequence spreading.
A classic narrowband link sits on a single channel. An interference source that falls on that channel silences the link completely. In spread spectrum the energy is distributed along the time or code axis, so the same interference produces only a partial loss.
- Frequency hopping: the carrier moves within the band in a defined pattern; interference disturbs only a few steps of that pattern.
- Direct sequence: the data is spread by multiplying it with a fast code; as the receiver despreads with the same code, the interference is spread out and weakened.
- Chirp: the carrier frequency is swept; it provides decodability at very low levels.
In industrial remote control this means that several kits can work on the same site and that the link survives despite the varying noise sources in the facility. The XRF protocol used in AXI's HCT400 and HCT402 kits uses a frequency-hopping architecture, and the dump data states that multi-kit operation on the same site is supported.
Context where this term is used: Wireless remote control installation: pairing, relay, safety