Jitter
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and
telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics
such as the frequency of successive pulses, the signal amplitude, or phase of periodic signals. Jitter is a
significant, and usually undesired, factor in the design of almost all communications links (e.g., USB, PCI-e,
SATA, OC-48).
Latency
Latency is the time that a data packet in computer networks requires from the transmitter to the receiver. This
arises from the runtime in the transmission medium and the processing time of active components (such as a
switch, in contrast to passive components like a hub). The latency corresponds to approximately one-half of
the round trip time (back and forth path) of a ping.
LLC
Logical Link Control is the name for a network protocol in telecommunications that was standardized as IEEE
802.2 by the Institute of Electrical and Electronics Engineers. It is a protocol whose main purpose is data
security on the connection level and therefore belongs to layer 2 of the OSI module.
Line Loss
Loss of the synchronized connection
LOF (loss of frame)
Loss of Frame (LOF) is a signal indicating that an ATM receiving station has lost the frame description. This
signal is used to monitor the performance of the physical layer in frame-oriented networks.
Modem
A DSL modem, known in technical terminology as an "NTBBA" (Network Termination Broad Band Access), is a
device for transmitting data by way of a subscriber line using DSL technology. It forms the network termination
for the DSL line at the subscriber and thus represents the matching piece to the DSLAM.
ADSL:
The technical
term for an ADSL modem is an ADSL Transceiver Unit – Remote or ATU-R for short.
NT
The Network Termination (NT) in telecommunication describes the point at which access to a communication
network is provided to a terminal.
Noise Margin
Noise margin is the difference between the current line SNR and the SNR that is required for a specific bit rate.
Example:
SNR 1 line
= 45dB
SNR 2 required = 39dB (for 8000 kbps for example)
Noise margin = 6dB
(SNR 1 - SNR 2 = noise margin)
Since the SNR of the line is a fixed value apart from fluctuations and the minimum noise margin, in order to
maintain the noise margin of 6 dB specified in the DSLAM, the transmitted data rate must change when there
are changes in the line from disturbances, length or other factors. If a line that has a very high NM is tested, it
means that a higher data rate is also possible. This is also displayed by the KE3500 under max. data rate.
Ping
Ping is a diagnostic tool used to check whether a specific host can be reached in an IP network. In addition to
this, most implementations of this tool today specify the time between transmitting a packet to this host and the
receipt of an immediately returned response packet (= packet round-trip time or RTT).
Operating Manual
KE3500
xDSL
M
ULTI
T
EST
42
KURTH ELECTRONIC Test & Measurement www.kurthelectronic.de [email protected]
