User guide

March 2005 Understanding Canopy Networks
Through Software Release 6.1
Page 60 of 425 Issue 1
Canopy System User Guide
◦ 1 beacon slot, which identifies the
− timing and distribution for the SMs
− ratio of uplink to downlink allocation
− ESN of the AP
− color code
− protocol (point-to-point or point-to-multipoint)
− number of registered SMs
− frame number
− control slot information
When an SM boots, the following sequence occurs:
1. The SM finds this beacon slot from an AP.
2. The SM synchronizes with the AP.
3. If BAM is configured on the AP and the AP is licensed for authentication, then
a. the AP sends a Registration Request message to the BAM server for
authentication.
b. following a successful challenge, the BAM server returns an Authentication
Grant message to the AP.
c. the AP sends a Registration Grant to the SM.
If BAM is not configured on the AP or the AP is not licensed for authentication,
then the AP simply returns the Registration Grant to the SM.
This Registration Grant includes the distance between the AP and SM. The SM uses the
distance to distinguish when to transmit data in the uplink frame. The AP performs
advance scheduling of up to 1024 frames that each SM will be permitted to use in the
uplink frame.
ACK Slots
When the AP Status page is displayed and Expanded Stats has been selected, the
Status page displays the total of ACK slots (1 through 7). In an ACK slot, the AP or SM
sends to the other a bitmap, which tracks packet fragments.
Control Slots
When the AP Status page is displayed and Expanded Stats has been selected, the
Status page displays the total of control slots (default 3, maximum 16). These control
slots are contention slots. If too many SMs contend for these slots, then the number of
control slots may be increased.
7.1.4 Media Access Control and AP Capacity
Regardless of whether the maximum number of SMs (200) all request service at the
same time, the reservation Media Access Control (MAC) system allows the AP to give a
reservation slot to each SM that requests service.
Regardless of the distance between any SM and the AP, the reservation MAC system
ensures that all SM data slots are free of contention. For this reason
◦ all SMs are equally able to compete for uplink and downlink bandwidth.
◦ the capacity of the AP is not degraded by distance from the SMs.