High-Throughput APs

With the implementation of the IEEE 802.11ac standard, very-high-throughput can be configured to operate on the 5 GHz frequency band. High-throughput (802.11n) can be configured on both the 5 GHz and 2.4 GHz frequency bands. High-throughput is enabled by default, and can be enabled or disabled in the 802.11a and 802.11g radio profiles. For details, see 2.4 Ghz and 5 Ghz Radio RF Management

Two different profiles advanced define settings specific to high-throughput APs, the high-throughput radio profile and the high-throughput SSID profile. Use the High-throughput radio profile to configure your APs to advertise intolerance of 40 MHz operation. ( By default, this option is disabled, and 40 MHz operation is allowed.) This profile also allows you to enable the CSD Override feature. When you turn on CSD override, CSD is disabled and only one antenna transmits data, even if they are being sent to high-throughput stations. The High-throughput SSID profile configures the high-throughput SSID settings for 802.11n.

You must create and modify a high-throughput radio or high-throughput SSID profile to change default values for an AP radio, such as activating features not enabled by default, disabling features that are enabled by default, or modifying default values for configuration settings.

 

Stations are not allowed to use high-throughput with TKIP stand-alone encryption, although TKIP can be provided in mixed-mode BSSIDs that support high-throughput. High-throughput is disabled on a BSSID if the encryption mode is stand-alone TKIP or WEP.

Configuring Advanced High-Throughput Radio Settings

Most deployments do not require manual configuration of the high-throughput radio profile, however, you can configure advanced high-throughput radio profile settings using the WebUI or CLI interfaces

In the WebUI

1. In the Managed Network node hierarchy, navigate to the Configuration > System > Profiles tab.
2. From the All Profiles window, expand the RF Management menu, then click High-Throughput Radio.
3. Select the High-Throughput Radio profile you want to edit or click + and enter a name into the Profile Name dialog box to create a new profile.
4. Configure the throughput settings described in Table 1.
5. Click Save.
6. Click Pending Changes.
7. In the Pending Changes window, select the check box and click Deploy Changes.

Table 1: High-Throughput Radio Profile Configuration Parameters

Parameter

Description

honor 40MHz intolerance

When enabled, the radio will stop using the 40 MHz channels if the 40 MHz intolerance indication is received from another AP or station. Uncheck the Honor 40 Mhz intolerance check box to disable this feature.

Default: Enabled

CSD override

Most transmissions to high throughput (HT) stations are sent through multiple antennas using cyclic shift diversity (CSD). When you enable the CSD Override parameter, CSD is disabled and only one antenna transmits data, even if they are being sent to high-throughput stations. This enables interoperability for legacy or high-throughput stations that cannot decode 802.11n CDD data. This option is disabled by default, and should only be enabled under the supervision of Aruba technical support.

Use this feature to turn off antenna diversity when the AP must support legacy clients such as Cisco 7921g VoIP phones, or older 802.11g clients (e.g. Intel Centrino clients). Note, however, that enabling this feature can reduce overall throughput rates.

In the CLI

(host)(config) #rf ht-radio-profile <profile>

(host)(config) #rf dot11a-radio-profile|dot11g-radio-profile <profile> high-throughput-enable

Configuring Advanced High-Throughput SSID settings

Most deployments do not require manual configuration of the high-throughput SSID profile, however, you can configured advanced high-throughput SSID profile settings or modify default SSID profile values using the WebUI or CLI interfaces.

 

De-aggregation of MAC Service Data Units (A-MSDUs) is supported with a maximum frame transmission size of 4k bytes; however, this feature is always enabled and is not configurable. Aggregation is not currently supported.

In the WebUI

1. In the Managed Network node hierarchy, navigate to the Configuration > System > Profiles tab.
2. Expand the Wireless LAN menu.
3. Select High-Throughput SSID.
4. Select the High-Throughput SSID profile you want to edit or click + and enter a name into the Profile Name dialog box to create a new profile.
5. Configure the high-throughput SSID profile settings described in Table 2 .

Table 2: High-Throughput SSID Profile Parameters

Parameter

Description

General

High throughput enable (SSID)

Determines if this high-throughput SSID allows high-throughput (802.11n) stations to associate.

Enabling high-throughput in an WLAN high-throughput SSID profile enables Wi-Fi Multimedia (WMM) base features for the associated SSID.

Default: Enabled.

40 MHz channel usage

Enable or disable the use of 40 MHz channels. This parameter is enabled by default.

Default: Enabled.

Very High throughput enable (SSID)

Enable or disable support for Very High Throughput (802.11ac) on the SSID.

Default: Enabled.

80 MHz channel usage (VHT)

Enable or disable the use of 80 MHz channels on Very High Throughput (VHT) APs.

Default: Enabled.

Multi User Transmit Beamforming

VHT - Multi User Transmit Beamforming

Enable or disable VHT Multi-User Transmit Beamforming. If this parameter is disabled, all other Multi-User Transmit Beamforming configuration parameters have no effect.

Default: Enabled.

Transmit Beamforming

 

VHT - Explicit Transmit Beamforming

Enable or disable VHT Explicit Transmit Beamforming for the 802.11ac-capable APs. When this parameter is enabled, the AP requests information about the Multiple-Input and Multiple-Output (MIMO) channel and uses that information to transmit data over multiple transmit streams using a calculated steering matrix. The result is higher throughput due to improved signal at the beamforming (the receiving client). If this parameter is disabled, all other transmit beamforming settings will not take effect.

Default: Enabled.

Advanced

BA AMSDU Enable

Enable or disable Receive AMSDU in Block ACK (BA) negotiation. If enabled, AP denies clients from sending AMSDU using BA agreement.

Default: Enabled.

Temporal Diversity Enable

When this setting is enabled and the client is not responding to 802.11 packets, the AP will launch two hardware retries; if the hardware retries are not successful then it attempts software retries.

Default: Disabled.

Legacy stations

Control whether or not legacy (non-HT) stations are allowed to associate with this SSID. By default, legacy stations are allowed to associate. This setting has no effect on a BSS in which HT support is not available.

Default: Enabled.

Low-density Parity Check

If enabled, the AP will advertise Low-density Parity Check (LDPC) support. LDPC improves data transmission over radio channels with high levels of background noise.

Default: Enabled.

Maximum number of spatial streams usable for STBC reception

Control the maximum number of spatial streams usable for Space-Time Block Code (STBC) reception. 0 disables STBC reception, 1 uses STBC for MCS 0-7. Higher MCS values are not supported. (Supported on the AP‑105, 130 Series, and 170 Series only. The configured value will be adjusted based on AP capabilities.)

Default: 1.

NOTE: If transmit beamforming is enabled, STBC will be disabled for beamformed frames.

Maximum number of spatial streams usable for STBC transmission.

Control the maximum number of spatial streams usable for STBC transmission. 0 disables STBC transmission, 1 uses STBC for MCS 0-7. Higher MCS values are not supported. (Supported on AP‑105, 130 Series, and 170 Series only. The configured value will be adjusted based on AP capabilities.)

Default: 1.

NOTE: If transmit beamforming is enabled, STBC will be disabled for beamformed frames.

MPDU Aggregation

Enable or disable MAC Protocol Data Unit (MPDU) aggregation.

High-throughput APs are able to send aggregated MAC protocol data units (MDPUs), which allow an AP to receive a single block acknowledgment instead of multiple ACK signals. This option, which is enabled by default, reduces network traffic overhead by effectively eliminating the need to initiate a new transfer for every MPDU.

Default: Enabled.

Max received A-MPDU size

Control the maximum size, in bytes, of an Aggregated-MAC Packet Data Unit (A-MPDU) that can be received on this high-throughput SSID.

Default: 65535 bytes.

Max transmitted A-MPDU size

Control the maximum size, in bytes, of an A-MPDU that can be sent on this high-throughput SSID.

Range: 1576–65535 bytes.

Min MPDU start spacing

Minimum time between the start of adjacent MPDUs within an aggregate MPDU, in microseconds.

Range: 0 (No restriction on MDPU start spacing), .25 µsec, .5 µsec, 1 µsec, 2 µsec, 4 µsec.

Default: 0.

Short guard interval in 20 MHz mode

Enable or disable use of short (400 ns) guard interval in 20 MHz mode.

A guard interval is a period of time between transmissions that allows reflections from the previous data transmission to settle before an AP transmits data again. An AP identifies any signal content received inside this interval as unwanted inter-symbol interference, and rejects that data. The 802.11n standard specifies two guard intervals: 400 ns (short) and 800 ns (long). Enabling a short guard interval can decrease network overhead by reducing unnecessary idle time on each AP. Some outdoor deployments, may, however require a longer guard interval. If the short guard interval does not allow enough time for reflections to settle in your mesh deployment, inter-symbol interference values may increase and degrade throughput.

Default: Enabled.

Short guard interval in 40 MHz mode

Enable or disable use of short guard interval (400 ns) in 40 MHz mode of operation.

Default: Enabled.

Short guard interval in 80 MHz mode

Enable or disable use of short guard interval (400 ns) in 80 MHz mode of operation.

Default: Enabled.

Supported MCS set

A list of Modulation Coding Scheme (MCS) values or ranges of values to be supported on this SSID. The MCS you choose determines the channel width (20 MHz vs. 40 MHz vs. 80 MHz) and the number of spatial streams used by the mesh node.

Range: 0–31.

Default: 0–31.

To specify a smaller range of values, enter a hyphen between the lower and upper values. To specify a series of different values, separate each value with a comma.

Examples:
2–10
1,3,6,9,12

MCS value of 16-23 are supported on 130 Series/RAP-155/11ac APs only.

MCS value of 24-31 are supported on 320 Series APs only.

VHT - Supported MCS Map

Comma separated list of maximum supported MCS for spatial streams 1 through 4. Valid values for maximum MCS are 7, 8, 9, and '-' (if spatial stream is not supported). Maximum MCS of a spatial stream cannot be higher than the previous streams. If an MCS is not valid for a particular combination of bandwidth and number of spatial streams, it will not be used for Tx and Rx.

Default: 9,9,9,9.

VHT - Transmit Beamforming Sounding Interval

Time interval in milliseconds between channel information updates between the AP and the beamformee client.

Default: 25 msec.

NOTE: This is applicable for 802.11ac-capable APs only.

Maximum VHT MPDU size

Maximum size of a VHT MPDU.

Default: 11454 bytes.

Maximum number of MSDUs in an A-MSDU on best-effort AC

Set the maximum number of MSDUs in a TX A-MSDU on best effort AC.

Default: 2.

NOTE: In tunnel and decrypt-tunnel forwarding mode, TX A-MSDU is disabled if the value is set to 0. If the value is set to non-zero, TX A-MSDU is enabled and set to this value.

Maximum number of MSDUs in an A-MSDU on background AC

Set the maximum number of MSDUs in a TX A-MSDU on background AC.

Default: 2.

NOTE: TX A-MSDU is disabled if the value is set to 0. In decrypt-tunnel forwarding mode, TX A-MSDU on background AC is disabled and assigning any value has no effect.

Maximum number of MSDUs in an A-MSDU on video AC

Set the maximum number of MSDUs in a TX A-MSDU on video AC.

Default: 2.

NOTE: TX A-MSDU is disabled if the value is set to 0. In decrypt-tunnel forwarding mode, TX A-MSDU on video AC is disabled and assigning any value has no effect.

Maximum number of MSDUs in an A-MSDU on voice AC

Set the maximum number of MSDUs in a TX A-MSDU on voice AC.

Default: 0.

NOTE: TX A-MSDU is disabled if the value is set to 0. In decrypt-tunnel forwarding mode, TX A-MSDU on voice AC is disabled and assigning any value has no effect.

In the CLI

(host)(config) #wlan ht-ssid-profile <profile-name>