6-10
Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-14209-01
Chapter 6 Configuring Radio Settings
Configuring MCS Rates
Use the
no
form of the
speed
command to remove one or more data rates from the configuration. This
example shows how to remove data rates basic-2.0 and basic-5.5 from the configuration:
ap1200#
configure terminal
ap1200(config)#
interface dot11radio 0
ap1200(config-if)#
no speed basic-2.0 basic-5.5
ap1200(config-if)#
end
Configuring MCS Rates
Modulation Coding Scheme (MCS) is a specification of PHY parameters consisting of modulation order
(BPSK, QPSK, 16-QAM, 64-QAM) and FEC code rate (1/2, 2/3, 3/4, 5/6). MCS is used in the 1250
series 802.11n radios, which define 32 symmetrical settings (8 per spatial stream):
•
MCS 0–7
•
MCS 8–15
•
MCS 16–23
•
MCS 24–31
The 1250 series access point supports MCS 0–15. High throughput clients support at least MCS 0–7.
MCS is an important setting because it provides for potentially greater throughput. High throughput data
rates are a function of
MCS
,
bandwidth
, and
guard interval
. 802.11 a, b, and g radios use 20-MHz
channel widths.
Table 6-2
shows potential data rased based on MCS, guard interval, and channel width.
speed
(contined)
On the 802.11n 2.4-GHz radio, the
default
option sets
rates 1.0, 2.0, 5.5, and 11.0 to enabled.
On the 802.11n 5-GHz radio, the
default
option sets rates
to 6.0, 12.0, and 24.0 to enabled.
The default MCS rate setting for both 802.11n radios is
0–15.
Step 4
end
Return to privileged EXEC mode.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Command
Purpose
Table 6-2
Data Rates Based on MCS Settings, Guard Interval, and Channel Width
MCS Index
Guard Interval = 800ns
Guard Interval = 400ns
20-MHz Channel
Width Data Rate
(Mbps)
40-MHz Channel
Width Data Rate
(Mbps)
20-MHz Channel
Width Data Rate
(Mbps)
40-MHz Channel
Width Data Rate
(Mbps)
0
6.5
13.5
7 2/9
15
1
13
27
14 4/9
30
2
19.5
40.5
21 2/3
45
3
26
54
28 8/9
60
4
39
81
43 1/3
90