User guide
Canopy System User Guide Configuring an AP for the Destination
pmp-0229 (Mar 2013)
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Table 49: Control slot settings for all FSK APs in cluster
Number of High Priority Channel Disabled SMs that
Register to the AP
Number of Control
Slots Recommended
1 to 10 1
11 to 50 2
51 to 150 4
151 to 200 6
Table 50: Control slot settings for all OFDM APs in cluster
Number of High Priority Channel Disabled SMs that
Register to the AP
Number of Control
Slots Recommended
1 to 10 2
11 to 50 4
51 to 150 6
151 to 200 8
This field indicates the number of (reserved) control slots configured by the operator. Control slots
are half the size of data slots. The SM uses reserved control slots and unused data slots for
bandwidth requests. SMs with High Priority Channel use an additional Virtual Circuit, and should
be counted twice when planning Control Slot configuration. For example, a network including 20
SMs with High Priority Channel disabled and 20 SMs with High Priority Channel enabled may be
configured with 4 Control Slots (this is a recommendation based on the number of SMs in the
network – see below for other factors contributing to Control Slot configuration decisions).
If too few reserved control slots are specified, then latency increases in high traffic periods. If too
many are specified, then the maximum capacity is unnecessarily reduced.
In a typical cluster, each AP should be set to the same number of control slots to assure proper
timing in the send and receive cycles. However, where high incidence of small packets exists, as
in a sector that serves several VoIP streams, additional control slots may provide better results. For
APs in a cluster of mismatched control slots settings, or where OFDM and FSK APs of the same
frequency band are co-located, use the frame calculator. See Using the Frame Calculator Tool
(All) for Co-location on Page 542.
Broadcast Repeat Count
The default is 2 repeats (in addition to the original broadcast packet, for a total of 3 packets sent
for every one needed), and is settable to 1 or 0 repeats (2 or 1 packets for every broadcast).
ARQ (Automatic Repeat reQuest) is not present in downlink broadcast packets, since it would
cause unnecessary uplink traffic from every SM for each broadcast packet. For successful
transport without ARQ, the AP repeats downlink broadcast packets. The SMs filter out all
repeated broadcast packets and, thus, do not transport further.