Aviat Networks ECLIPSE EDGE, Руководство пользователя

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16 Aviat Networks
Chapter 2. Eclipse Edge System Description
Transmit Switching Conditions
For a Tx switch to occur, the offline ODU Tx must be available (not-alarmed/ not
blocked).
A Tx protection switch will occur in the following situations:
• Tx transmit failure
• ODU hardware failure
• ODU unplugged
• ODU is in a diagnostic mode
• Remote initiated protection switch (RIPS).
• This applies so that an undetected Tx failure (silent Tx failure) does not cause
indefinite failure of the radio link.
• It occurs when both remote receivers are in Rx alarm, whereupon a switching
command is returned to the local-end transmitter
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Switching Times
When a Tx switch occurs, the total traffic outage from fault detection to traffic
recovery, does not exceed 200ms.
When a remote initiated protection switch (silent Tx switch) occurs, traffic is
recovered within 20 seconds (typically within 5 seconds).
Switching Guard Times
To prevent protection switch oscillation a switch oscillation guard time mechanism
applies to Tx online protection switching. The mechanism is described below.
• A period of guard time begins immediately after each protection switch occurs.
• No protection switches are permitted during the guard time. Protection switching
may resume once the guard time has elapsed.
• To damp possible oscillations in the system the guard time is regularly adjusted,
using the following rules:
• The guard time doubles after each switch (up to the maximum).
• The guard time halves after each period of guard time during which no switching
occurs (down to the minimum).
• When the guard time decays to its minimum, subsequent switch requests are
actioned immediately.
• The switch guard time has a minimum period of 5 seconds and a maximum period of
320 seconds (5 x 26 events).
• The guard time mechanism is disabled in protection diagnostic modes.
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Where a receive path alarm occurs because of a path problem, no signal is received in either direction. In such
situations the ‘silent Tx’ switch command will be prompted by receive path alarms at both ends of the link, but will
not be received at the transmit ends of the link, hence no silent Tx switch will occur on a complete (both-way) path
fade/failure.