Pseudorandom noise
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In cryptography, pseudorandom noise (PRN) is a signal similar to noise which satisfies one or more of the standard tests for statistical randomness.
Although it seems to lack any definite pattern, pseudorandom noise consists of a deterministic sequence of pulses that will repeat itself after its period.
Each pulse in this sequence is known as a chip and the inverse of its period as chip rate. Compare bit rate and baud.
In cryptographic devices, the pseudorandom noise pattern is determined by a key and the repetition period can be very long, even millions of years.
Pseudorandom noise is used in some electronic musical instruments, either by itself or as an input to subtractive synthesis, and in many white noise machines.
In spread-spectrum systems, modulated carrier transmissions appear as noise to any receiver that is:
- not locked on the transmitter frequencies; or
- incapable of correlating a locally generated pseudorandom sequence with the received signal.
A pseudonoise code (PN code) is one that has a spectrum similar to a random sequence of bits but is deterministically generated. The most commonly used sequences in direct-sequence spread spectrum systems are maximal length sequences, Gold codes, Kasami codes, and Barker codes. [1]
