A bipolar violation, bipolarity violation, or BPV, is a violation of the
bipolar encoding rules where two
pulse
In medicine, the pulse refers to the rhythmic pulsations (expansion and contraction) of an artery in response to the cardiac cycle (heartbeat). The pulse may be felt ( palpated) in any place that allows an artery to be compressed near the surfac ...
s of the same
polarity occur without an intervening pulse of the opposite polarity. This indicates an
error
An error (from the Latin , meaning 'to wander'Oxford English Dictionary, s.v. “error (n.), Etymology,” September 2023, .) is an inaccurate or incorrect action, thought, or judgement.
In statistics, "error" refers to the difference between t ...
in the
transmission of the signal.
and
E-carrier signals are transmitted using a scheme called bipolar encoding, a.k.a.
Alternate Mark Inversion
In telecommunication, bipolar encoding is a type of return-to-zero (RZ) line code, where two nonzero values are used, so that the three values are +, −, and zero. Such a signal is called a duobinary signal. Standard bipolar encodings are designed ...
(AMI), where ONE is represented by a pulse, and a ZERO is represented by no pulse. Pulses (which represent ones) always alternate in polarity, so that if, for example two positive pulses are received in succession, the receiver knows that an error occurred (a violation) in that one or more bits were either added or deleted from the original signal.
Reliable transmission of data using this scheme requires a regular stream of pulses; too many zero bits in succession can cause a loss of synchronization between transmitter and receiver. To ensure that this is always present, there exist a number of
modified AMI code
Modified AMI codes are a digital telecommunications technique to maintain system synchronization. Alternate mark inversion (AMI) line codes are modified by deliberate insertion of bipolar violations. There are several types of modified AMI codes, ...
s which use judiciously placed bipolar violations to encode long
string
String or strings may refer to:
*String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects
Arts, entertainment, and media Films
* ''Strings'' (1991 film), a Canadian anim ...
s of consecutive zeroes.
References
Error detection and correction
Line codes
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