Alcatel-Lucent 9500 MXC User Manual page 868

Hot Standby
Vol. VI-F-12
the Rx/Tx diversity bus:
• Hot Standby on page F-12
• Space Diversity on page F-13
• Frequency Diversity on page F-13
• Ring Protection on page F-15
Figure F-5 shows data routing for a hot standby configuration using RAC 30s.
The originating data source is shown as a DAC, but the process applies to all
DAC, RAC or AUX sources on the TDM bus.
Transmit direction:
• DAC Tx drives to the TDM bus.
• The primary RAC (online Tx) uplifts DAC Tx data from the TDM bus and
delivers it to its ODU.
• The secondary RAC (offline Tx) also uplifts the same DAC Tx data but at its
ODU the PA is muted (no ODU transmit).
Receive direction:
• Both primary and secondary RACs receive data, but only the secondary RAC
(online Rx), drives to the TDM bus (secondary RAC is default Rx online).
• Data from the primary RAC Rx is routed to the Rx diversity bus, where it is
uplifted by the secondary RAC.
• The secondary RAC decides on a frame-by-frame basis, which receive stream
(primary or secondary RAC data) to pass to the TDM bus. The decision favours
the data source for the previous frame if both frames are un-errored. This
selection process is hitless.
• The DAC uplifts received data from the TDM bus.
• The online Rx RAC only switches (secondary RAC to primary RAC) in the
event the secondary RAC is missing/incorrect, or there is a software load
failure. When either occurs, received data is sent directly to the TDM bus by the
primary RAC. This switching from online primary Rx RAC to the secondary
RAC is not hitless; there is a maximum 500 ms detection, acquisition and
recovery period (service restoration time).
The Tx diversity bus is not used for hot-standby.
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