Cisco 2100 Series Configuration Manual page 460

Architecture Overview
Note
–
Table 8-1
Data Rate
54 Mbps
48 Mbps
36 Mbps
24 Mbps
18 Mbps
12 Mbps
9 Mbps
6 Mbps
The required minimum LinkSNR is driven by the data rate and the following formula: Minimum
•
SNR + fade margin.
–
–
–
Table 8-2
Date Rate
6
9
12
18
24
36
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.
Cisco Wireless LAN Controller Configuration Guide
8-8
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
Backhaul Data Rates and Minimum LinkSNR Requirements
Table 8-2
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
Minimum Required LinkSNR Calculations by Data Rate
Minimum SNR (dB) +
5
6
7
9
13
17
Minimum Required LinkSNR (dB)
31
29
26
22
18
16
15
14
summarizes the calculation by data rate.
Fade Margin =
9
9
9
9
9
9
Chapter 8 Controlling Mesh Access Points
Table
Minimum Required
LinkSNR (dB)
14
15
16
18
22
26
OL-17037-01
8-1.