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Glossary & ITU TStandards
CT850 Test Set SDH/PDH, Jitter/Wander
Included in this section along with the glossary of terms is a listing
of ITU T standards for SDH and PDH.
Three sets of terms are arranged at the beginning of this section
because it is important to see that they are not equivalent terms,
which is how they get used in normal discussions. They are:
Add/ Drop
The process where a part of the information carried in a
transmission system is extracted (dropped) at an intermediate
point and different information is inserted (added) for subse-
quent transmission. The remaining traffic passes straight through
the multiplexer without additional processing.
Map/ Demap
A term for multiplexing, implying more visibility inside the
resultant multiplexed bit stream than available with convention-
al asynchronous techniques.
Multiplex/ Demultiplex
Multiplex (MUX) To transmit two or more signals over a
single channel. Demultiplex (DEMUX) To separate two or
more signals previously combined by compatible multiplexing
equipment. Demultiplexing A process applied to a multiplex
signal for recovering signals combined within it and for
restoring the distinct individual channels of the signals.
An alphabetical list of glossary terms follows.
CT850 Test Set SDH/PDH, Jitter/Wander User Manual Glossary 1
Glossary
Add/Drop Multiplexer (ADM)
A multiplexer capable of extracting and inserting lower rate
signals from a higher rate multiplexed signal without complete-
ly demultiplexing the signal.
Administrative Unit (AU)
An Administrative Unit is the information structure which
provides adaptation between the higher order path layer and the
Multiplex Section layer. The Virtual Container (VC) plus the
pointers (H1, H2, H3 bytes) is called the Administrative Unit
(AU).
AIS (Alarm Indicating Signal)
A code sent downstream indicating an upstream failure has
occurred.
AMI
Alternate Mark Inversion. The line coding format in transmis-
sion systems where successive ones (marks) are alternatively
inverted (sent with polarity opposite that of the preceding mark).
Analog Jitter Out
A signal that contains the demodulated jitter from a line or clock
input.
ANSI
American National Standards Institute. A standards setting,
non government organization, which develops and publishes
standards for "voluntary" use in the United States.
Asynchronous
A network where transmission system payloads are not
synchronized and each network terminal runs on its own clock.
Asynchronous Transfer Mode (ATM)
A multiplexing/switching technique in which information is
organized into fixed length cells with each cell consisting of an
identification header field and an information field. The transfer
mode is asynchronous in the sense that the use of the cells
depends on the required or instantaneous bit rate.
Glossary 2 CT850 Test Set SDH/PDH, Jitter/Wander User Manual
Glossary
Attenuation
Reduction of signal magnitude or signal loss, usually expressed
in decibels.
AU-4
Virtual Container (VC) plus the Transport Overhead pointers.
AU N
Administrative Unit N; a discrete unit of the SDH payload
carrying one or more VC N
Automatic Protection Switching (APS)
The ability of a network element to detect a failed working line
and switch the service to a spare (protection ) line. 1+1 APS
pairs a protection line with each working line. 1:N APS provides
one protection line for every N working lines.
Backhauling
Cumbersome traffic management technique used to reduce the
expense of multiplexing/demultiplexing.
Bandwidth
Information carrying capacity of a communication channel.
Analog bandwidth is the range of signal frequencies that can be
transmitted by a communication channel or network.
Bidirectional
Operating in both directions. Bi directional APS allows
protection switching to be initiated by either end of the line.
Binary N Zero Suppression (BNZS)
Line coding system that replaces N number of zeros with a
special code to maintain pulse density required for clock
recovery. N is typically 3, 6, or 8.
BIP 8 (Bit Interleaved Parity 8)
A method of error checking in SDH which allows in service
performance monitoring. For example, a BIP 8 creates eight bit
(one byte) groups, then does a parity check for each of the eight
bit positions in the byte.
CT850 Test Set SDH/PDH, Jitter/Wander User Manual Glossary 3
Glossary
B ISDN (Broadband Integrated Services Digital Network)
A single ISDN network which can handle voice, data, and
eventually video services.
Bit
One binary digit; a pulse of data.
Bit Error vs. Block Error
Error rate statistics play a key role in measuring the perfor-
mance of a network. As errors increase, user payload (especially
data) must be re transmitted, or lost entirely.
Bit Error Rate (BER) The number of bit errors detected in a
unit of time, usually one second. Bit Error rate (BER) is
calculated with this formula:
BER = errored bits received/ total bits sent.
Block Error Rate (BLER) One of the underlying concepts of
error performance is the notion of Errored Blocks, i.e., blocks in
which one or more bits are in error. A block is a set of
consecutive bits associated with the path or section monitored
by means of an Error Detection Code (EDC), such as Bit
Interleaved Parity (BIP). Block Error rate (BLER) is calculated
with this formula:
BLER = errored blocks received/ total blocks sent.
Bit Interleaved Parity (BIP)
A parity check that groups all the bits in a block into units (such
as byte), then performs a parity check for each bit position in the
group.
Bit Stuffing
In asynchronous systems, a technique used to synchronize
asynchronous signals to a common rate before multiplexing.
Bits per second (bit/s)
The number of bits passing a point every second. The transmis-
sion rate for digital information.
Glossary 4 CT850 Test Set SDH/PDH, Jitter/Wander User Manual
Glossary
Broadband
Services requiring over 2 Mbit/s transport capacity.
CCITT
See ITU.
Channel
The smallest subdivision of a circuit that provides a type of
communication service; usually a path with only one direction.
Circuit
A communications path or network; usually a pair of channels
providing bi directional communication.
Circuit Switching
Basic switching process whereby a circuit between two users is
opened on demand and maintained for their exclusive use for the
duration of the transmission.
Coding Violation (CV)
A transmission error detected by the difference between the
transmitted line code and that expected at the receive end by the
logical coding rules.
Concatenation
The linking together of various data structures, for example two
channels joined to form a single channel. In SDH, a number (M)
of TUs can be linked together to produce a concatenated
container, M times the size of the TU. An example of this is the
concatenation of five TU 2s to carry a 32 Mbit/s video signal,
known as VC 2 5c.Once assembled, any concatenated VC
structure is multiplexed, switched and transported through the
network as a single entity.
Conformance Tests
Conformance Tests (also know as Standards Conformance Tests)
are predefined tests that measure the impact of jitter or wander
on networks or network elements. They are defined in the ITU-T
Recommendations.
CT850 Test Set SDH/PDH, Jitter/Wander User Manual Glossary 5
Glossary
Cyclic Redundancy Check (CRC)
A technique for using overhead bits to detect transmission
errors.
Data Communications Channel (DCC)
Data channels in SDH that enable OAM communications
between intelligent controllers and individual network nodes as
well as inter node communications.
dB
The symbol for decibels.
dBm
The symbol for power level in decibels relative to 1 mW.
Defect
A limited interruption in the ability of an item to perform a
required function. Persistence of a defect can cause a failure.
Digital Cross connect (DCS)
An electronic cross connect which has access to lower rate
channels in higher rate multiplexed signals and can electroni-
cally rearrange (cross connect) those channels.
Digital Signal
An electrical or optical signal that varies in discrete steps.
Electrical signals are coded as voltages, optical signals are
coded as pulses of light.
E1, E2, E3, E4
Alternative names for the ITU T 2 Mb/s, 8 Mb/s, 32 Mb/s, and
140 Mb/s tributary signals.
ES
Errored Second; measure of network or equipment performance
ETSI (European Telecommunications Standards Institute)
Organization responsible for defining and maintaining European
standards, including SDH.
Glossary 6 CT850 Test Set SDH/PDH, Jitter/Wander User Manual
Glossary
Failure
A termination of the ability of an item to perform a required
function. A failure is caused by the persistence of a defect.
FEBE (Far End Block Error)
See Remote Error Indication (REI).
FERF (Far End Receive Failure)
See Remote Defect Indication (RDI).
FIFO
First In First Out; a type of data buffer
Fixed Stuff
A bit or byte whose function is reserved. Fixed stuff locations,
sometimes called reserved locations, do not carry overhead or
payload.
Floating mode
A virtual tributary mode that allows the VC synchronous
payload envelope to begin anywhere in the VC.
Framing
Method of distinguishing digital channels that have been
multiplexed together.
Frequency
The number of cycles of periodic activity that occur in a discrete
amount of time.
Frequency Drift Rate
The rate of change of a line or clock frequency, measured in
ppm/sec. A new measure of tining quality.
Fullband
A jitter filter range that includes the wideband range but extends
the low-frequency cutoff to 10 Hz or below. This filter is useful
when analyzing video timing quality.
Grooming
Consolidating or segregating traffic for efficiency.
CT850 Test Set SDH/PDH, Jitter/Wander User Manual Glossary 7
Glossary
HDB3
High Density Bipolar 3. A bipolar coding method that does not
allow more than three consecutive zeros.
Highband
A jitter filter range that measures high-frequency jitter. The
band pass filters are defined in ITU-T standards (where they are
sometimes referred to as HP2 LP1).
Highpass
The lower 3 dB corner frequency of a filter. The filter passes
frequencies higher than this frequency.
HP PLM
High order path, payload label mismatch (or path label
mismatch). This measurement is classifed as a defect. Disable or
Enable this choice at the RX Analysis Configuration, Trace
Mismatch Detection menu.
HP UNEQ
High order path, unequipped. This measurement is classifed as a
defect. Disable or Enable this choice at the RX Analysis
Configuration, Trace Mismatch Detection menu.
Interleave
The ability of SDH to mix together and transport different types
of input signals in an efficient manner, thus allowing higher
transmission rates.
ITU (International Telecommunications Union)
An agency of the United Nations responsible for the regulation,
standardization, co ordination and development of international
telecommunications as well as the harmonization of national
policies. It functions through international committees of
telecommunications administrations, operators, manufacturers
and scientific/industrial organizations.
Glossary 8 CT850 Test Set SDH/PDH, Jitter/Wander User Manual
Glossary
Jitter
The short term variations of the significant instants of a timing
signal from their ideal positions in time (where short term
implies that these variations are of frequency greater than or
equal to 10 Hz).
Jitter Hit
When peak-to-peak jitter crosses a predetermined threshold.
Jitter Tolerance
A conformance test that measures the susceptability of a
network element input to incoming jitter.
Jitter Transfer
A conformance test that measures the transfer of jitter from the
input to the output of a network element.
Jitter Transfer Function
A graph that shows jitter gain as a function of jitter frequency.
Line Alarm Indication Signal (AIS)
A Line AIS is generated by Section Terminating Equipment
upon Loss of Signal or Loss of Frame.
Line Coding Violation (LCV)
The sum of the BIP errors detected at the Line layer. Line CVs
are collected using the BIP codes in the B2 bytes of the Line
Overhead.
Line Errored Second (ES)
A second during which at least one Line CV occurred, or a
second during which the line was in the Line AIS state.
Line Overhead (LOH)
Controls the payload information using the section layer and
provides alarm indications, error monitoring, and message
signalling between two LTEs.
CT850 Test Set SDH/PDH, Jitter/Wander User Manual Glossary 9
Glossary
Line Severely Errored Second (SES)
A second with N or more Line CVs, or a second during which
the line was in the Line AIS state. The value of N varies with
the transmit rate, but corresponds to a 2 ◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo