Configuring 802.11 Parameters

Configuring the 802.11n Parameters

802.11n Parameters

This section provides instructions for managing 802.11n access points on your network. The 802.11n devices support the 2.4 and 5-GHz bands and offer high throughput data rates.

The 802.11n high throughput rates are available on all the 802.11n access points for the WLANs using WMM with no Layer 2 encryption or with WPA2/AES encryption enabled.


Note
Some Cisco 802.11n APs may intermittently emit incorrect beacon frames, which can trigger false wIPS alarms. We recommend that you ignore these alarms. The issue is observed in the following Cisco 802.11n APs: 1140, 1250, 2600, 3500, and 3600.

Configuring the 802.11n Parameters (GUI)

Procedure

Step 1

Choose Wireless > 802.11a/n or 802.11b/g/n > High Throughput to open the (5 GHz or 2.4 GHz) High Throughput page.

Step 2

Select the 11n Mode check box to enable 802.11n support on the network. The default value is enabled.

Step 3

Select the check boxes of the desired rates to specify the modulation and coding scheme (MCS) rates at which data can be transmitted between the access point and the client. These data rates, which are calculated for a 20-MHz channel width using a short guard interval, are available:

  • 0 (7 Mbps)

  • 1 (14 Mbps)

  • 2 (21 Mbps)

  • 3 (29 Mbps)

  • 4 (43 Mbps)

  • 5 (58 Mbps)

  • 6 (65 Mbps)

  • 7 (72 Mbps)

  • 8 (14 Mbps)

  • 9 (29 Mbps)

  • 10 (43 Mbps)

  • 11 (58 Mbps)

  • 12 (87 Mbps)

  • 13 (116 Mbps)

  • 14 (130 Mbps)

  • 15 (144 Mbps)

    Any associated clients that support the selected rates may communicate with the access point using those rates. However, the clients are not required to be able to use this rate in order to associate. The MCS settings determine the number of spatial streams, the modulation, the coding rate, and the data rate values that are used.

Step 4

Click Apply.

Step 5

Use the 802.11n data rates that you configured by enabling WMM on the WLAN as follows:

  1. Choose WLANs to open the WLANs page.

  2. Click the ID number of the WLAN for which you want to configure WMM mode.

  3. When the WLANs > Edit page appears, choose the QoS tab to open the WLANs > Edit (Qos) page.

  4. From the WMM Policy drop-down list, choose Required or Allowed to require or allow client devices to use WMM. Devices that do not support WMM cannot join the WLAN.

    If you choose Allowed, devices that cannot support WMM can join the WLAN but will not benefit from the 802.11n rates.

  5. Click Apply.

Step 6

Click Save Configuration.

Note 

To determine if an access point supports 802.11n, look at the 11n Supported text box on either the 802.11a/n (or 802.11b/g/n) Cisco APs > Configure page or the 802.11a/n (or 802.11b/g/n) AP Interfaces > Details page.

Configuring the 802.11n Parameters (CLI)

Procedure

  • Enable 802.11n support on the network by entering this command:

    config {802.11a | 802.11b} 11nsupport {enable | disable}

  • Specify the modulation and coding scheme (MCS) rates at which data can be transmitted between the access point and the client by entering this command:

    config {802.11a | 802.11b} 11nsupport mcs tx {0-15} {enable | disable}

  • Use the 802.11n data rates that you configured by enabling WMM on the WLAN as follows:

    config wlan wmm {allow | disable | require} wlan_id

    The require parameter requires client devices to use WMM. Devices that do not support WMM cannot join the WLAN.

    If set to allow , devices that cannot support WMM can join the WLAN but do not benefit from 802.11n rates.

  • Specify the aggregation method used for 802.11n packets as follows:

    1. Disable the network by entering this command:

      config {802.11a | 802.11b} disable network

    2. Specify the aggregation method entering this command:

      config {802.11a | 802.11b} 11nsupport {a-mpdu | a-msdu} tx priority {0-7 | all} {enable | disable}

      Aggregation is the process of grouping packet data frames together rather than transmitting them separately. Two aggregation methods are available: Aggregated MAC Protocol Data Unit (A-MPDU) and Aggregated MAC Service Data Unit (A-MSDU). A-MSDU is performed in hardware and therefore is the default method.

      You can specify the aggregation method for various types of traffic from the access point to the clients. This table defines the priority levels (0-7) assigned per traffic type.

      Table 1. Traffic Type Priority Levels

      User Priority

      Traffic Type

      0

      Best effort

      1

      Background

      2

      Spare

      3

      Excellent effort

      4

      Controlled load

      5

      Video, less than 100-ms latency and jitter

      6

      Voice, less than 10-ms latency and jitter

      7

      Network control

      You can configure each priority level independently, or you can use the all parameter to configure all of the priority levels at once. When you use the enable command, the traffic associated with that priority level uses A-MPDU transmission. When you use the disable command, the traffic associated with that priority level uses A-MSDU transmission. Configure the priority levels to match the aggregation method used by the clients. By default, A-MPDU is enabled for priority level 0, 4 and 5 and the rest are disabled. By default, A-MSDU is enabled for all priorities except 6 and 7.

    3. Reenable the network by entering this command:

      config {802.11a | 802.11b} enable network

  • Configure the 802.11n-5 GHz A-MPDU transmit aggregation scheduler by entering this command:

    config 802.11{a | b} 11nsupport a-mpdu tx scheduler {enable | disable | timeout rt timeout-value}

    The timeout value is in milliseconds. The valid range is between 1 millisecond to 1000 milliseconds.

  • Configure the guard interval for the network by entering this command:

    config 802.11{a | b} 11nsupport guard_interval {any | long}

  • Configure the Reduced Interframe Space (RIFS) for the network by entering this command:

    config 802.11{a | b} 11nsupport rifs rx {enable | disable}

  • Save your changes by entering this command:

    save config

  • View the configuration settings for the 802.11 networks by entering this command:

    show {802.11a | 802.11b}

Configuring 802.11h Parameters

802.11h Parameters

802.11h informs client devices about channel changes and can limit the transmit power of those client devices.

Configuring the 802.11h Parameters (GUI)

Procedure

Step 1

Disable the 802.11 band as follows:

  1. Choose Wireless > 802.11a/n > Network to open the 802.11a Global Parameters page.

  2. Unselect the 802.11a Network Status check box.

  3. Click Apply.

Step 2

Choose Wireless > 802.11a/n > DFS (802.11h) to open the 802.11h Global Parameters page.

Step 3

In the Power Constraint area, enter the local power constraint. The valid range is between 0 dBm and 30 dBm.
Step 4

In the Channel Switch Announcement area, select the Channel Announcement check box if you want the access point to announce when it is switching to a new channel and the new channel number, or unselect this check box to disable the channel announcement. The default value is disabled.

Step 5

If you enabled the channel announcement, the Channel Quiet Mode check box appears. Select this check box if you want the access point to stop transmitting on the current channel, or unselect this check box to disable quiet mode. The default value is disabled.

Step 6

Click Apply.

Step 7

Reenable the 802.11a band as follows:

  1. Choose Wireless > 802.11a/n > Network to open the 802.11a Global Parameters page.

  2. Select the 802.11a Network Status check box.

  3. Click Apply.

Step 8

Click Save Configuration.

Configuring the 802.11h Parameters (CLI)

Procedure

Step 1

Disable the 802.11a network by entering this command:

config 802.11a disable network

Step 2

Enable or disable an access point to announce when it is switching to a new channel, and the new channel number by entering this command:

config 802.11h channelswitch {enable { loud | quiet} | disable}

Enter either quiet or loud for the enable parameter. When the quiet mode is enabled, all the clients who can enable 802.11h channel switch announcements should stop transmitting packets immediately because the AP detects that the radar and client devices should also quit transmitting to reduce interference. By default, the Channel Switch feature is in disabled state.

Step 3

Configure a new channel using the 802.11h channel announcement by entering this command:

config 802.11h setchannel channel channel

Step 4

Configure the 802.11h power constraint value by entering this command:

config 802.11h powerconstraint value

Use increments of 3 dB for the value so that the AP goes down one power level at a time.

Step 5

Reenable the 802.11a network by entering this command:

config 802.11a enable network

Step 6

View the status of the 802.11h parameters by entering this command:

show 802.11h

Information similar to the following appears: 


Power Constraint................................. 0
Channel Switch................................... Disabled
Channel Switch Mode.............................. 0