700-712-100-01, Revision 01
Functional Description
UTU-712 and ETU-762 List 1
May 10, 1999
15
Other applications for single-pair rate selectable HDSL units include those where deployment of additional
subscriber lines is limited by available two-pair HDSL spans. Using two single-pair rate selectable HDSL units
on each two-pair span can double the number of subscribers.
H
OT
S
WAPPING
UTUs can be inserted and removed from any compatible shelf or enclosure with the power turned on. This will
not cause damage to the units nor will it cause interference to any other HDSL circuits that are operating within
the same shelf or enclosure.
P
ERFORMANCE
M
ONITORING
AND
H
ISTORY
The UTU and ETU units provide extensive real time, non-disruptive monitoring of HDSL transmission
performance parameters for all units in a circuit. Performance of the user interface ports is also monitored. Current
cumulative counts of the past 24 hours and historical data in the form of 24-hour history (in 15-minute increments)
and a 7-day history (in 24-hour increments) are available to assist in identifying problem sources during
troubleshooting. See “View Status” on
for information on performance screens.
The monitored parameters are described in
.
A
LARMS
The UTU and ETU units generate alarms for problem conditions on the HDSL transmission facility and at the
local application interface. Alarms can be individually enabled or disabled as well as specified whether the alarm
reports as a Major or Minor alarm. See “System Configuration” on
to configure alarms. See “View Status”
on
to view alarm conditions.
The HDSL transmission and application interface alarms are described in
Table 7.
Monitored HDSL Transmission and Interface Performance Parameters
Monitored Parameter
Description
HDSL Noise Margin
A measure of the ratio of signal power to noise power, in decibels (dB), at a receiver point. A value
of 0 dB means that the predicted transmission BER is equal to 10
–7
, a value of 6 dB means the
predicted transmission BER is equal to 10
–10
. The Main menu status display continuously updates the
margin value.
HDSL CRC-6
A six-bit word in every HDSL frame, representing a calculation based on all the bits in that frame. Any
mismatch at the receiver, between the received CRC-6 and the one calculated, based on the received
data in the frame, indicates that one or more bits were received in error. The units use this parameter
to derive HDSL ES.
HDSL Loss of Sync Word
(LOSW)
The unit has detected an error in one or more bits in six consecutive HDSL sync words. TS 101 135
requires two consecutive sync words to be received without error to clear this condition. A LOSW
condition generally indicates the loop is down, thus data cannot be transmitted.
Based on the monitored parameters, the LTU and NTU units derive the following performance parameters:
HDSL Errored Second (ES)
An interval of one second during which at least one CRC-6 error is detected at the incoming HDSL
port or there is an LOSW condition.
HDSL Unavailable Second
(UAS)
A second during which a loop is down.