Cisco 2100 Series, Руководство по настройке

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8-8
Cisco Wireless LAN Controller Configuration Guide
OL-17037-01
Chapter 8 Controlling Mesh Access Points
Architecture Overview
Note The backhaul bit rate is set on the Wireless > 802.11an > Network page within the 802.11an
global parameters section.
–
The required minimum LinkSNR for backhaul links per data rate is shown in Table 8-1 .
• The required minimum LinkSNR is driven by the data rate and the following formula: Minimum
SNR + fade margin.
Table 8-2 summarizes the calculation by data rate.
–
Minimum SNR refers to an ideal state of non-interference, non-noise and a system packet error
rate (PER) of no more than 10%
– Typical fade margin is approximately 9 to 10 dB
–
We do not recommend using data rates greater than 24 Mbps in municipal mesh deployments as
the SNR requirements do not make the distances practical
Table 8-2 Minimum Required LinkSNR Calculations by Data Rate
•
Number of backhaul hops is limited to eight, but three to four is recommended
The number of hops is recommended to be limited to three–four primarily to maintain sufficient
backhaul throughput, because each mesh AP uses the same radio for transmission and reception of
backhaul traffic. This means that throughput is approximately halved over every hop. For example,
the maximum throughput for 24 Mbps is approximately 14 Mbps for the first hop, 9 Mbps for the
second hop, and 4 Mbps for the third hop.
Table 8-1 Backhaul Data Rates and Minimum LinkSNR Requirements
Data Rate Minimum Required LinkSNR (dB)
54 Mbps 31
48 Mbps 29
36 Mbps 26
24 Mbps 22
18 Mbps 18
12 Mbps 16
9 Mbps 15
6 Mbps 14
Date Rate Minimum SNR (dB) + Fade Margin =
Minimum Required
LinkSNR (dB)
6 5 9 14
9 6 9 15
12 7 9 16
18 9 9 18
24 13 9 22
36 17 9 26