Co-Location Of 5.4 Ghz Ofdm With Standard 5.4 Ghz Canopy Fsk; Channel Spacing; Frame Calculations And Configuration Settings - Cambium Networks PMP 400 Series Configuration And User's Manual

PMP 400/430 and PTP 200/230 Series Configuration and User Guide
Co-location of 5.4 GHz OFDM with Standard 5.4 GHz
Canopy FSK
When locating 5.4 GHz PMP 400/430 and PTP 200/230 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.

Channel Spacing

Center spacing of 25 MHz between collocated FSK and OFDM APs provides a 10 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 10 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 (15 MHz spacing) in some deployments.

Frame Calculations and Configuration Settings

Interference between collocated Canopy systems can be avoided by following two practices:
1. Use a CMM with GPS synchronization. This synchronizes frame start, so that all collocated
APs begin transmitting at the same time each 2.5 millisecond frame.
2.
Use the frame calculators in each module, OFDM and FSK (the frame calculators are different,
as frame details are different) to select Downlink Data %, Range, and Control Slots for each
system that produce "Rec SEQ Start" values that are within 300 bit times. This ensures that all
collocated APs end transmission each frame before any collocated AP begins to receive
When collocating only Canopy OFDM APs together, or collocating only Canopy hardware-scheduled FSK
APs together, the simple practice of setting the Downlink Data %, Range, and Control Slots the same on all
APs ensures they won't interfere with each other. (These parameters are set on the "Configuration =>
Radio" page of the AP.) However, due to the different "physical" layer between Canopy OFDM and Canopy
FSK, this doesn't necessarily work when collocating OFDM and FSK together.
You will need to use frame calculators on both the OFDM and FSK modules, as they are different frame
calculators. For the same Downlink Data %, Range, and Control Slots, the frame calculators give different
results. Use of the frame calculators is similar to the previous use when collocating PMP 100 FSK software-
scheduled and hardware-scheduled APs.
pmp-0042 (March 2014)
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