Error Monitor on T3/E3 Line
Overview
Monitor T3/E3 line application displays the T3/E3 line conditions on one or more T3/E3 cards. The alarms that can be monitored include LOS, LOF, AIS, IDLE, RAI/X-BIT, and Excessive 0's. With this application, the T3/E3 line frequency, power level, and various errors such as Frame errors, P-Bit Parity, C-Bit Parity, FEBE, BPV, Excessive 0's, and CV can also be monitored.
Monitoring FEAC Messages are applicable only for T3 Systems with C-Bit Parity Framing Format.
Alarms and Errors Monitor for T3 (DS3)/E3 Analyzers
Description
LOS - (Loss of Signal) is a physical layer error, which indicates losses in signal of short duration. The red LED indicates the LOS condition.
Declaration and clearing:
T3 - LOS is declared when the receiver detects 192 consecutive zeros. It will be cleared when there is no Excessive Zero (EXZ) events over a 192-bit window that starts with the first one received.
E3 - LOS is declared when the receiver detects 192 consecutive zeros. It will be cleared when there is no Excessive Zero (EXZ) events over a 192-bit window that starts with the first one received.
LOF - (Loss of Frames) indicating that the receiver is getting too many F bits or M bits in error.
Declaration and clearing:
T3 - LOF is declared when the receiver detects three or more F bits in error out of 16 consecutive F bits, or 2 or more M bits in error out of four consecutive M bits. It will be cleared when frame synchronization occurs. The criteria for selecting F or M bit are done through the T3 Configuration window.
E3 - LOF is declared when the receiver detects four consecutive bad FAS. It will be cleared when receiving three consecutive good FAS.
AIS - (Alarm Indication Signal) alarm is used to indicate a transmission failure within the network. The end terminals in the network generate AIS alarm to indicate the loss of service.
Declaration and clearing:
T3 - AIS is declared when the receiver detects a properly aligned repeating 1010... pattern with less than 4-bit errors in each of the 84-bit information field (out of 84 possible) for 1024 consecutive information bit fields (1.95ms) and all C bits are majority decoded to be zero during this time. It will be cleared when the receiver detects a properly aligned 1010... pattern with 4 or more bit errors (out of 84 possible), in each 84 bit information field, for 1024 consecutive information bit fields (1.95ms).
E3 - AIS is declared when the receiver detects four or fewer zeros in two consecutive 1536- bit frames. It will be cleared when receiving five or more zeros in two consecutive 1536-bit frames.
Idle - this alarm becomes active upon reception of the T3 Idle signal. Idle alarm indicates that the line has not been provisioned for service and stays without triggering network alarms.
T3 - Idle alarm is declared when the receiver detects a properly aligned repeating 1010... pattern in each 84-bit information field, with less than 4-bit errors (out of 84 possible) for 1024 consecutive information bit fields (1.95ms) and the C bits in Subframe 3 are majority decoded to be zero during this time.
E3 - Idle alarm is not defined for E3
RAI/X-Bit - RAI indicates a problem between the loopback's router interface's transmitter and the far end T3/E3 receiver, but it may not be in the segment between the router and the adjacent node.
Declaration and clearing:
T3 - RAI alarm is declared when the receiver detects the bits X1 and X2 = 0 for four consecutive M frames (426µs). It is cleared when the receiver detects bits X1 and X2 = 1 for four consecutive M frames (426µs).
E3 - RAI alarm is declared when the receiver detects Bit 11 = 1 for 4 consecutive frames (6144 bits / 179µs). It is cleared when the receiver detects Bit 11 = 0 for 4 consecutive frames (6144 bits / 179µs).
Legends
Active:
Whenever any alarms are active, the alarm indicator glows in RED informing about the alarms status.
Not Active:
The alarms are said to be not active if none of the alarms are detected on T3/E3 line. This is indicated with a Green LED for the corresponding alarms.
History:
When any of the alarm is detected (becomes active) and then switches to non-active state, the alarm is considered as History and is indicated with Yellow LED.
Signal Inputs
Frequency:
This shows the line frequency T1/E1 in Hertz (Hz)
Level:
This shows the T1/E1 line power in Vp (Peak Voltage)
Error Counters
Frame Errors - Monitors the number of times an incorrect framing bits pattern was detected. The T3 analyzer can be configured to count F or M bits or both using the T3 Configuration window
P-Bit Errors - T3 Only - A parity bit error is defined as an occurrence when the two parity bits do not match one another or when the two Parity Bits do not match the parity calculation made on the information bits.
C-Bit Parity - T3 Only - A C-bit parity bit error is defined as an occurrence when the majority decoded three CP parity bits do not match the parity calculation made on the information bits.
FEBE (Far End Block Errors) - T3 Only - This counter reports the number of times the three FEBE bits do not equal 111.
BPV (BiPolar Violation) - T3 Only - A BPV is defined as consecutive pulses (or marks) of the same polarity that are not part of a HDB3 code word.
Excessive 0's - These bits report the number of Excessive Zero occurrences (EXZ). An EXZ occurrence is defined as three or more consecutive zeros in the T3 mode and four or more consecutive zeros in the E3 mode. As an example, a string of eight consecutive zeros would only increment this counter once.
CV Errors (E3) - E3 Only - A CV is defined in ITU O.161 as consecutive BPVs of the same polarity.
FEAC Message (only for T3 Systems with C-Bit Parity Farming Format)
FEAC messages provide a serial communications channel that contains a repeating 16-bit code word that indicates the state of the far-end and can control the near-end by invoking loopbacks both on the T3 and T1 lines. If no code words are being sent, the FEAC channel contains all ones.
The Monitor window displays the incoming FEAC message. GL's T3 analyzer supports generation of standard FEAC messages and any user-defined arbitrary code.
Monitoring FEAC Messages for T3 (DS3) Analyzers
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