PMP 400 and PTP 200 Series
Canopy User Guide Supplement
Issue 3, January 2009
Page 20 of 45
The default Range, set on the AP’s “Configuration => General” page, is 5 miles, but can be set in
1 mile increments between 1 and 10 miles. The BHM performs its own ranging and so no range
need be set for it.
If the Range is set to greater than 5 miles, then the Downlink Data % can be a maximum of 85%,
else some close-in SMs won’t register due to details of the Canopy scheduler. For example, a
Range of 6 miles and a Downlink Data % of 90% is not allowed. Operationally,
•
if the Downlink Data % is set to greater than 85% and the user enters a range greater
than 5 miles, the module will reset the Downlink Data % to 85%
•
if the range is set to greater than 5 miles and the user enters a Downlink Data % of
greater than 85%, the module will reset the Downlink Data % to 85%.
Suggested Control Slot settings as a function of number of SMs in the sector are shown in Table
5. Generally all APs in a cluster should use the same number of control slots so as to keep the
frame structures, and thereby the send and receive timing, the same.
Table 5: Control Slot Settings
Number of SMs that
Register to the AP
Number of Control
Slots Recommended
1 to 10
0
1
11 to 50
1
51 to 150
2
151 to 200
3
Note 1: Any sector with the
Hi Priority Channel
enabled on any SM should be
configured with at least 1
Control Slot
on the AP.
In some cases, operators may find that sectors with high levels of small packet requests, such as
might be seen in a sector handling several VoIP streams, benefit overall from slightly higher
Control Slot settings. If different sectors require different numbers of Control Slots, the operator
should use the Frame Calculator to find a combination of settings that put “Rec SEQ Start” times
within 300 bit times. See section 3.6.2 on page 15 for details.
Control Slots are reserved for SMs’ bandwidth requests and never handle data. A higher number
of control slots gives higher probability that an SM’s bandwidth request will be heard when the
system is heavily loaded, but with the tradeoff that sector capacity is reduced by about 100 kbps
for each Control Slot configured, so there will be less capacity to handle the request.
Uplink Data Slots are used first for data, but if not needed for data in a given frame can be used
by the SMs for bandwidth requests. So, even with zero control slots configured, the SMs can still
make bandwidth requests, using any unused data slots.
BHMs do not have settings for control slots, as there is no contention on the one-to-one link.
Downlink Data %, Range, and Control Slots should be set consistent with the results of any
collocation planning done using OFDM and FSK frame calculators in section 3.6.2 on page 15.
4.4
DFS AND REGULATORY PARAMETERS FOR 5.4 GHZ RADIOS
Dynamic Frequency Selection (DFS) is a requirement in several countries and regions for 5 GHz
unlicensed systems to detect radar systems and avoid co-channel operation. DFS and other
