Cisco Cisco Aironet 1522 Lightweight Outdoor Mesh Access Point 디자인 가이드
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Cisco Aironet 1520, 1130, 1240 Series Wireless Mesh Access Points, Design and Deployment Guide, Release 6.0
OL-20213-01
Architecture Overview
Choosing the Best Parent
AWPP follows the following process in selecting parents for a RAP or MAP with a radio backhaul:
•
A list of channels with neighbors is generated by passive scanning in the scan state, which is a subset
of all backhaul channels.
of all backhaul channels.
•
The channels with neighbors are sought by actively scanning in seek state and the backhaul channel
is changed to the channel with the best neighbor.
is changed to the channel with the best neighbor.
•
The parent is set to the best neighbor and the parent-child handshake is completed in seek state.
•
Parent maintenance and optimization occurs in the maintain state.
This algorithm is run at startup and whenever a parent is lost and no other potential parent exists, and is
usually followed by CAPWAP network and controller discovery. All neighbor protocol frames carry the
channel information.
usually followed by CAPWAP network and controller discovery. All neighbor protocol frames carry the
channel information.
Parent maintenance occurs by the child node sending a directed NEIGHBOR_REQUEST to the parent
and the parent responding with a NEIGHBOR_RESPONSE.
and the parent responding with a NEIGHBOR_RESPONSE.
Parent optimization and refresh occurs by the child node sending a NEIGHBOR_REQUEST broadcast
on the same channel on which its parent resides, and by evaluating all responses from neighboring nodes
on the channel.
on the same channel on which its parent resides, and by evaluating all responses from neighboring nodes
on the channel.
A parent mesh access point provides the best path back to a RAP. AWPP uses ease to determine the best
path. Ease can be considered the opposite of cost, and the preferred path is the path with the higher ease.
path. Ease can be considered the opposite of cost, and the preferred path is the path with the higher ease.
Ease Calculation
Ease is calculated using the SNR and hop value of each neighbor, and applying a multiplier based on
various SNR thresholds. The purpose of this multiplier is to apply a spreading function to the SNRs that
reflects various link qualities.
various SNR thresholds. The purpose of this multiplier is to apply a spreading function to the SNRs that
reflects various link qualities.
In
, MAP2 prefers the path through MAP1 because the adjusted ease of (436906) though this
path is greater then the ease value (262144) of the direct path from MAP2 to RAP.
Figure 20
Parent Path Selection
Parent Decision
A parent mesh access point is chosen by using the adjusted ease, which is the ease of each neighbor
divided by the number of hops to the RAP:
divided by the number of hops to the RAP:
adjusted ease = min (ease at each hop)
Hop count
148448
MAP1
RAP
MAP2
Ease
873812
Ease
873812
Ease
262144
20 dB
20 dB
188 dB