ND SatCom SKYWAN IDU 1070, Manual

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26 Network Design and Engineering Guide 2010-10-26
General Carrier Design
Essential SkyWAN
®
Satellite Link Layer Features
- Time stamps to enable transmission time synchronisation.
- Feedback to slaves concerning their transmission power settings and frequency offsets.
The slave stations use the ranging burst for station registration and initial round trip time (earth
station to satellite to earth station) measurement. Registered slave stations use request bursts
-
for requesting transmission capacity on the satellite link,
- to give feedback to the master concerning the power level of the master’s reference bursts.
Active and Backup Master Role
Figure 2-7 Active and Backup Master
Although at one time there can be only one active master station in a Sky WAN
®
network it is
possible and recommended to configure two stations to be potential master stations. Both sta-
tions have to fulfil the master station requirements mentioned before. The station which enters
the network first will become active master, the other station backup master. If the backup mas-
ter detects an outage of the active master it will take over the master role within 2 seconds.
This ensures a seamless transition which does not interrupt network services. Note that there
is no automatic switchback of the master role even if the original active master comes up again.
In this case the new active master will keep this role whereas the recovered former active mas-
ter will now be the backup master.
To increase the resiliency of a Sky WAN
®
network, it makes sense to locate the two master sta-
tions in different geographical locations. This ensures continued network operation even if one
of the master sites is knocked out due to severe environmental conditions (e.g. hurricanes,
earth quakes, flooding, sun outages).