Canopy 400 Series OFDM AP and SM
User Guide
Version 1, April 2008
Page 13 of 40
service area and using one of the many radio analysis and mapping tools or on-line calculation
tools for calculating downtilt.
3.3
WEATHER RADAR
Spectrum between 5600 and 5650 MHz (sometimes called the “weather notch”) is used by some
weather radar and is not allowed for use by regulations in some regions, including Canada and,
for new equipment, Europe. When the Canopy module is set to one of those regions (configured
on the “Configuration => General” page of the module), it will not allow configuration of the
appropriate frequencies, as shown in Table 2. Even in regions where use of the spectrum
between 5600 and 5650 MHz is allowed, such as the US, the best practice is to not use these
channels if there are any other usable channels available. Only use the channels in this “weather
notch” after performing long-term site surveys (minimum of a week) to ascertain the spectrum is
clear and that there don’t appear to be any weather radar in the area that will cause interference
to your Canopy system.
3.4
RANGE AND THROUGHPUT PLANNING
Canopy 400 Series APs can provide 21 Mbps aggregate throughput at distances of 1.25 mi (~1
km) in RF environments with clear line-of-sight and low background interference levels. Additional
performance details are shown in Table 1 on page 11. RF environments with occluded Fresnel
zones or higher background interference levels may give lower, but still give very good,
performance, depending on the specifics of the environment.
Similar to standard Canopy, at any given instant, any radios not operating at 3X take twice (for
2X) or three times (for 1X) as much “air time” to transmit a given amount of data as if they were
running at 3X. Similar to standard Canopy, Canopy 400 Series modules may see reduced total
throughput when handling traffic with a high percentage of small packets.
The effect of this, again similar to standard Canopy, is that at any given instant total throughput
depends on
•
Mix of links running at 3X, 2X, and 1X
•
Mix of packet sizes
3.5
COLLOCATION WITH STANDARD 5.4 GHZ CANOPY FSK
When locating 5.4 GHz Canopy 400 Series OFDM APs near 5.4 GHz standard Canopy FSK APs
(especially on the same tower, but also in the same geographical area), the following practices
should be followed to avoid interference between the two systems:
•
Plan spacing between OFDM and FSK channels to provide
25 MHz center spacing
,
which gives a 10 MHz guard band between the 10 MHz OFDM channel and the 20
MHz FSK channel.
•
Coordinate
Downlink Data %, Range, and Control Slot settings using both the
OFDM and the FSK
frame calculators
The following paragraphs give more details on these recommended practices.
3.5.1
Channel Spacing
Center spacing of 25 MHz between collocated FSK and OFDM APs provides a 5 MHz guard
band between the 20 MHz and 10 MHz channels, which has proven useful and needed in field
testing. Alternatively, in cases where channel planning is severely restricted and the 5 MHz guard
band (25 MHz spacing) is not possible, using vertical separation of 5 feet or more between the
OFDM and FSK APs may allow collocation with no guard band (20 MHz spacing) in some
deployments.
