Spread Spectrum Technology
| Spread spectrum refers to the manner in which data signals travel through a radio frequency. Spread spectrum requires that data signals either alternate between carrier frequencies or constantly change their data pattern. Although the shortest distance between two points is a straight line (narrowband), spread spectrum is designed to trade-off bandwidth efficiency for reliability, integrity, and security. There are two types of spread spectrum radio: frequency hopping and direct sequence. FHSS requires the use of narrowband signals that change frequencies in a predictable pattern. The term frequency hopping refers to hopping of data signals between narrow channels. Somewhere between 20 and several hundred milliseconds, the signal hops to a new channel following a predetermined cyclic pattern. Because data signals using FHSS switch between RF bands, they have a strong resistance to interference and environmental factors. The constant hopping between channels also increases security as signals are harder to eavesdrop on. DSSS transmissions spread the signal over a full transmission frequency spectrum. For every bit of data that is sent, a redundant bit pattern is also sent. This 32-bit pattern is called a chip. These redundant bits of data provide for both security and delivery assurance. Transmissions are so safe and reliable simply because the system sends so many redundant copies of the data and only a single copy is required to have complete transmission of the data or information. DSSS can minimize the effects of interference and background noise.
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