Pseudorandom noise

In cryptography, pseudo random 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, pseudo random noise consists of a deterministic sequence of pulses that will repeat itself after its period.

In cryptographic devices, the pseudo random noise pattern is determined by a key and the repetition period can be very long, even millions of digits.

Pseudo random 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, the receiver correlates a locally generated signal with the received signal. Such spread-spectrum systems require a set of one or more "codes" or "sequences" such that

In a direct-sequence spread spectrum system, each bit in the pseudorandom binary sequence is known as a chip and the inverse of its period as chip rate; compare bit rate and symbol rate.

In a frequency-hopping spread spectrum sequence, each value in the pseudo random sequence is known as a channel number and the inverse of its period as the hop rate. FCC Part 15 mandates at least 50 different channels and at least a 2.5 Hz hop rate for narrow band frequency-hopping systems.

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