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''.
In
cryptographic devices, the pseudo-random 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] [2]
See also
★
Pseudorandom number sequence
★
Pseudorandom number generator
★
n-sequence
★
Federal Standard 1037C
★
MIL-STD-188