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This example used the 220-222 MHz frequency band. This is an auctioned band, and
as such, new systems must coexist with existing users. Furthermore, the
boundaries of the geographic block purchased must be respected to avoid
interference from adjacent blocks.
However, once these criteria are met, wireless planning can be done with the
assurance that new systems will be immune from interference from new users in
the band. |
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In the network shown above, a hypothetical SCADA Master
station is shown in Westgate Technology Park at Crane, IN. The Master station is
linked to remote sites in multiple cities throughout Southern Indiana, utilizing
the 220-222 MHz auctioned frequency band. Since the maximum bandwidth available in
this band is 50 KHz, each link will carry data at speeds of about 64 KBPS or
less.
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For Smart Grid applications in rural areas where population densities are low,
and backhaul distances can be large, this band is attractive. With appropriate
tower heights, path lengths of 50 - 60 miles can be readily achieved. |
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In the figure at the top, note how the link from the Master Site at WestGate
Technology Park to Fort Branch is lighter in color than the other links. While
the RX level of 99.2 dbm is higher than the Threshold of -107 dbm, the fade
margin is less than 10 db.
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The illustration showing a marginal link from WestGate Technology Park to Fort
Branch is based on a remote antenna height of 20 meters. Raising that to 32
meters (approximately 100 feet) will provide adequate fade margin.
The implication is the need for a Data Aggregation Point (DAP) on a centralized
tower at 32 meters. The DAP will then communicate with meters or distributed
field devices in the local area. |
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