Star Microwave SM Cirius LM, User Manual, Page: 73 / 79

Cirius LM User Manual 2016 Page 73
7. 1+1 Protection
7.1. Introduction
The radio in its standard configuration is an unprotected (1+0) IDU with a single N-
type connector interface to connect to a single ODU. An optional hot standby
protected (1+1) mode configuration is available, whereby two identical ODUs, a
primary and a secondary, are connected to a single IDU via two N-type connector
interfaces. The purpose of 1+1 protection is to minimize link outages by protecting
against ODU hardware failure by providing automatic switching to a standby
secondary ODU in the case of fault detection in the primary ODU. Note that this
feature is only available on the IDU.
7.2. 1+1 Switch Protection Operation
In a 1+1 redundant configuration, two identical ODUs, a primary and a secondary,
are connected to a single IDU. The primary ODU carries network traffic while the
secondary ODU remains in hot standby. In the event of fault detection in the
primary ODU, the IDU will automatically switch traffic to the hot standby secondary
ODU. The IDU will switch the transmit path only, the receive path only, or both,
depending on the nature of the failure. (Switching only the failed path avoids link
disruption in the nonfailed direction.) The IDU monitors the following parameters to
make this switch decision:
•
Near-side IDU Rx demodulator lock
•
Far-side IDU Rx demodulator lock
•
Near-side primary and standby ODU Rx RSSI
•
Far-side primary and standby ODU Rx RSSI
•
Presence or absence of IDU-ODU commands and status link
•
Presence or absence of far-side telemetry channel data
During normal operation, the primary ODU will operate normally and the standby
ODU will have its transmitter muted. Both receivers will be operational. Thus, at
each end of the link, both the primary and the standby ODU will receive
transmissions from just the primary ODU transmitter on the opposite end of the
link. The transmitter of the standby ODU is disabled until a failure is detected.
Three general scenarios are addressed by the protected mode operation:
1)
Receive Path Failure : In the event of a receive path failure, the receive path is
switched to the standby ODU. The transmit path is unaffected.