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Modulations and Data Rates
802.11 Bands
You can configure the 802.11b/g/n (2.4 GHz) and 802.11a/n/ac (5 GHz) bands for the controller to comply with the regulatory requirements in your country. By default, both 802.11b/g/n and 802.11a/n/ac are enabled.
When a controller is configured to allow only 802.11g traffic, 802.11b client devices are able to successfully connect to an access point but cannot pass traffic. When you configure the controller for 802.11g traffic only, you must mark 11g rates as mandatory.
Note | The Block Acks in a Cisco 2800, 3800, 1560 APs are sent at configured mandatory data rates in Cisco WLC for 2.4 GHz radio. |
Step 1 | Disable the 802.11a band by entering this command: config 802.11a disable network
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Step 2 | Disable the 802.11b/g band by entering this command: config 802.11b disable network
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Step 3 | Specify the rate at which the SSID is broadcast by the access point by entering this command: config {802.11a | 802.11b} beaconperiod time_unit where time_unit is the beacon interval in time units (TUs). One TU is 1024 microseconds. You can configure the access point to send a beacon every 20 to 1000 milliseconds. | ||
Step 4 | Specify the size at which packets are fragmented by entering this command: config {802.11a | 802.11b} fragmentation threshold where threshold is a value between 256 and 2346 bytes (inclusive). Specify a low number for areas where communication is poor or where there is a great deal of radio interference. | ||
Step 5 | Make access points advertise their channel and transmit power level in beacons and probe responses by entering this command: config {802.11a | 802.11b } dtpc {enable | disable} The default value is enabled. Client devices using dynamic transmit power control (DTPC) receive the channel and power level information from the access points and adjust their settings automatically. For example, a client device used primarily in Japan could rely on DTPC to adjust its channel and power settings automatically when it travels to Italy and joins a network there.
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Step 6 | Specify the maximum allowed clients that can be configured by entering this command: config {802.11a | 802.11b} max-clients max_allow_clients The valid range is between 1 to 200. | ||
Step 7 | Configure the RSSI Low Check feature by entering this command: config 802.11{a | b} rssi-check {enable | disable} | ||
Step 8 | Configure the RSSI Threshold value by entering this command: config 802.11{a | b} rssi-threshold value-in-dBm
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Step 9 | Specify the rates at which data can be transmitted between the controller and the client by entering this command: config {802.11a | 802.11b} rate {disabled | mandatory | supported} rate
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Step 10 | Enable the 802.11a band by entering this command: | ||
Step 11 | Enable the 802.11b band by entering this command: | ||
Step 12 | Enable or disable 802.11g network support by entering this command: config 802.11b 11gSupport {enable | disable} The default value is enabled. You can use this command only if the 802.11b band is enabled. If you disable this feature, the 802.11b band is enabled without 802.11g support. | ||
Step 13 | Enter the save config command to save your changes. | ||
Step 14 | View the configuration settings for the 802.11a or 802.11b/g band by entering this command:
Information similar to the following appears: 802.11a Network............................... Enabled 11nSupport.................................... Enabled 802.11a Low Band........................... Enabled 802.11a Mid Band........................... Enabled 802.11a High Band.......................... Enabled 802.11a Operational Rates 802.11a 6M Rate.............................. Mandatory 802.11a 9M Rate.............................. Supported 802.11a 12M Rate............................. Mandatory 802.11a 18M Rate............................. Supported 802.11a 24M Rate............................. Mandatory 802.11a 36M Rate............................. Supported 802.11a 48M Rate............................. Supported 802.11a 54M Rate............................. Supported ... Beacon Interval.................................. 100 ... Default Channel............................... 36 Default Tx Power Level........................ 1 DTPC Status................................... Enabled Fragmentation Threshold....................... 2346 Maximum Number of Clients per AP................. 200 |
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 802.11n access points for WLANs using WMM with no Layer 2 encryption or with WPA2/AES encryption enabled.
The 802.11n-only access points can filter out clients without high-throughput information element on the association request. The 802.11n-only access points access points reject association requests from clients without high-throughput information element (11n).
In the 802.11n high-throughput mode, there are no 802.11a/b/g stations using the same channel. The 802.11a/b/g devices cannot communicate with the 802.11n high-throughput mode access point, where as the 802.11n-only mode access point uses 802.11a/g rates for beacons or management frames.
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. |
Step 1 | Choose Wireless > 802.11a/n/ac 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. If you want to disable 802.11n mode when both 802.11n and 802.11ac modes are enabled, you must disable the 802.11ac mode first. | ||
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:
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Step 4 | Click Apply. | ||
Step 5 | Use the 802.11n data rates that you configured by enabling WMM on the WLAN as follows: | ||
Step 6 | Click Save Configuration.
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Enable 802.11n support on the network by entering this command:
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:
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}
View the configuration settings for the 802.11 networks by entering this command:
802.11ac
The 802.11ac radio module for the Cisco Aironet 3600 Series access point and Cisco Aironet 3700 Series access point provides enterprise-class reliability and wired-network-like performance. It supports three spatial streams and up to 160 MHz-wide channels for a maximum data rate of 2.5 Gbps.
The 802.11ac radio in slot 2 is a slave radio for which you can configure specific parameters. Because the 802.11ac is a slave radio, it inherits many properties from the main 802.11a/n radio on slot 1. The parameters that you can configure for the 802.11ac radio are as follows:
Admin status—Interface status of the radio that you can enable or disable. By default, the Admin status is in an enabled state. If you disable 802.11n, the 802.11ac radio is also disabled.
Channel width—You can choose the RF channel width as 20 MHz, 40 MHz, 80 MHz, or 160 MHz. If you choose the channel width as 160 MHz, you must enable the 802.11ac mode on the High Throughput page.
Note | The 11ac Supported field is a nonconfigurable parameter that appears for the 802.11ac slave radio in slot 2. |
Note | When the Cisco Aironet 3600 Series access point with 802.11ac radio module is in unsupported mode such as Monitor and Sniffer, Admin Status and Channel Width will not be configured. |
This section provides instructions to manage 802.11ac devices such as the Cisco Aironet 3600 Series Access Points and Cisco Aironet 3700 Series Access Point on your network.
Note | For the Cisco Aironet 3600 Series APs:
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Changing the 802.11n radio channel also changes the 802.11ac channels.
On the Cisco WLC GUI, the 802.11ac clients that are connected to the 802.11n radio are displayed 802.11an clients, and the 802.11ac clients that are connected to the 802.11ac radio are displayed as 802.11ac clients.
Ensure that your WLAN has WMM enabled and open or WPA2/AES for 802.11ac to be supported. Otherwise, the speed of 802.11ac is not available, even on 802.11ac clients.
For more information about the 802.11ac module on the Cisco Aironet 3600 Series access point, see http://www.cisco.com/c/en/us/products/wireless/aironet-3600-series/relevant-interfaces-and-modules.html.
The 802.11ac Wave 2 introduces additional capabilities beyond what were added with Wave 1. It utilizes MU-MIMO technology and other advancements to help increase wireless performance for applications such as HD video streaming. Wave 2 provides better RF efficiency that Wave 1 provides, in addition to a number of other features that further improve wireless connectivity.
MU-MIMO is short for Multi-User, Multiple-Input, Multiple-Output. MU-MIMO is an enhanced form of the MIMO technology that enables multiple independent radio terminals to access a system.
With 802.11n or 802.11ac Wave 1, an access point can transmit multiple spatial streams at the same time, but only directed to a single wireless client. This means only a single device gets data at a time. This is referred to as single-user MIMO (SU-MIMO).
802.11ac Wave 2 allows for MU-MIMO, which enables multiple users to simultaneously receive data from the AP simultaneously using the same channel. With MU-MIMO a Wave 2 capable access point is able to use its antenna resources to transmit to multiple clients, all at the same time and over the same channel. MU-MIMO is used in the downstream direction and requires the wireless clients to also be Wave 2 capable.
802.11ac Wave 2 allows for up to eight spatial streams. However, initial Wave2 implementations will only increase the number of spatial streams from 3 to 4 as compared to Wave 1 implementations. The support of an additional spatial stream allows for additional increased performance as compared to 3 SS APs.
For more information on these technologies, see the following documents on Cisco.com:
Cisco 802.11ac Wave 2 FAQs at http://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/802-11ac-solution/q-and-a-c67-734152.html
Fundamentals of 802.11ac Wave 2 post on the Cisco Interaction Network at http://blogs.cisco.com/cin/fundamentals-of-802-11ac-wave-2
802.11ac: The Fifth Generation of Wi-Fi technical white paper at http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3600-series/white_paper_c11-713103.html
The AP 1850 supports standards-based Explicit Compressed Beamforming Feedback (ECBF) as defined in the 802.11ac standards. With ECBF the client provides estimates of the wireless channel conditions to the access point. As these are based on explicit channel measurements from the client, both the AP and the client must support it. For 802.11ac, the access point’s ECBF is typically referred to as Transmit Beamforming or TxBF for short.
While both TxBF and ClientLink 3.0 improve the performance of wireless client devices, ClientLink3.0 provides an additional advantage over TxBF. ClientLink3.0 technology does not depend on any client-side hardware or software capabilities and operates seamlessly in mixed-mode environments where 802.11ac and 802.11a/n clients coexist on the same access point. In comparison, TxBF requires client-side support to take advantage of the performance improvements of beamforming and therefore benefits only 802.11ac clients that support TxBF.
The Cisco 1850 AP supports TxBF but not beamforming to legacy client devices. Therefore, Cisco 1850 AP does not support ClientLink 3.0.
Note | ClientLink 3.0 is supported on the Cisco Aironet 2700 and 3700 Series 802.11ac APs. |
Note | You can disable TxBF only on the Cisco Aironet 1140, 1260, 1550, and 3500 APs that support ClientLink 1.0. It cannot be disabled on the APs that supports ClientLink 2.0 and above. |
The 802.11ac module is supported only on the following access points:
1700
1800
2700
2800
3600
3700
3800
The 802.11ac module is turned off if the built-in 5-GHz radio is turned off.
You must ensure that the configuration of the channel, power values, and the mode of the 802.11ac module is the same as those of the built-in 5-GHz radio on the AP. Also, the 802.11ac module serves only 802.11ac clients.
The 802.11ac module main channel cannot be changed individually.
This 802.11ac support is applicable only to the following controller platforms:
Controllers do not support High availability for 802.11ac modules. The 802.11ac configuration (802.11ac Data Rates and 802.11ac Global mode) on the controller is not synchronized with the standby controller. This might result in client throughput fluctuations and reassociations when you explicitly disable those configurations on the active controller.
In addition, the 802.11ac Global mode configuration controls whether the radio module is enabled. If 802.11ac Global mode is enabled on one controller but not on another, the 802.11ac module might be disabled if the access point associates with a controller on which 802.11ac Global mode is disabled.
When changing AP from static to auto channel assignment, by default AP moves to best possible bandwidth supported by the radio and a valid channel. Channel number and width assignment may be suboptimal until next DCA cycle gets started.
SSIDs with TKIP and SSIDs with TKIP+AES are not enabled on the 802.11ac radios. Therefore, all the 5-GHz clients are expected to associate with the 802.11n radios.
Step 1 | Choose . | ||
Step 2 | Check the 11ac mode check box to enable the 802.11ac support on the network.
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Step 3 | Ensure that all of the 0 to 31 MCS data rate indices are enabled (which is the default setting). | ||
Step 4 | Save the configuration. |
This feature is supported on all the Cisco Wave 2 APs.
Enable or disable 802.11ac support by entering this command:
config 802.11a 11acSupport {enable | disable}
Configure MCS transmit rates by entering this command:
config 802.11a 11acSupport mcs tx {rate-8 | rate-9} ss spatial-stream-value {enable | disable}
Note | Ensure that all of the 0 to 31 MCS data rate indices are enabled (which is the default setting). In 8.1 and later releases, RF profiles should include MCS 0-31 instead of MCS 0-23 in earlier releases. |
This feature is supported on all the Cisco Wave 2 APs.