Configuration Client Link

In this post we wills learn about Client Link (Beam forming).

As we all know that 802.11n provides remarkable performance improvements in the areas of throughput, link reliability, and predictability. The transition to 802.11n provides significant benefits, but most organizations will take a phased approach to migration.

In the coming days/month/Year, many installations can be expected to support a mix of older 802.11a/g clients and newer 802.11n clients. The reasons that older clients will continue to operate for some time is that it takes few years for a full refresh cycle of enterprise laptops. And certain industries such as manufacturing and healthcare can take even longer to replace their devices.

In mixed environments, older 802.11a/g clients delay communications for 802.11n clients and reduce system performance. That’s y Cisco has developed a new technology that allows businesses to deliver the performance benefits of 802.11n to 802.11a/g devices, thereby increasing their useful life.

Client-Link is a spatial-filtering mechanism used at a transmitter to improve the received signal power or signal-to-noise (SNR) ratio at an intended receiver (client). Cisco Client-Link ensures our mixed 802.11a/g and 802.11n devices operate at the best possible data rates on our wireless networks.

Cisco Aironet 1140, 1250, 1260, 1600, 2600, 2700, 3500 and 3600 series access points support Client-Link.

To know more:  The New Generation of Cisco Aironet Access Points

ClientLink2

Client-Link uses multiple transmit antennas to focus transmissions in the direction of an 802.11a or 802.11g client, which increases the downlink SNR and the data rate to the client, reduces coverage holes, and enhances overall system performance. Client-Link works with all existing 802.11a and 802.11g clients.

Remembering Points:

  1. Client-Link starts only when the signal from the client falls below these thresholds:
    • 11a clients—RSSI of –60 dBm or weaker
    • 11g clients—RSSI of –50 dBm or weaker
  2. 11b clients do not support Client-Link.
  3. The access point actively maintains Client-Link data for up to 15 clients per radio.
  4. Client-Link is supported only for legacy orthogonal frequency-division multiplexing (OFDM) data rates (6, 9, 12, 18, 24, 36, 48, and 54 Mbps).
  5. Client-Link is not supported for complementary code keying (CCK) data rates (1, 2, 5.5, and 11 Mbps).
  6. Only access points that support 802.11n can use Client-Link.
  7. Two or more antennas must be enabled for transmission.
  8. OFDM data rates must be enabled.
  9. Client-Link must be enabled.

Configure Client-Link

Via GUI:

Login to WLC GUI

Go to Wireless > 802.11a/n or 802.11b/g/n > Network

Select the Client-Link check box to globally enable Client-Link on 802.11a or 802.11g network.

Click Apply to commit changes.

The default value is disabled.

See the screenshot:

ClientLink1

To override the global configuration and enable or disable Client-Link for a specific AP as follows (My AP doesn’t support this so cant paste the screenshot):

Choose Wireless > Access Points > Radios > 802.11a/n or 802.11b/g/n

Under the 11n Parameters section, select the Client-Link check box to enable Client-Link for this AP.

Via CLI:

Globally enable or disable ClientLink on your 802.11a or 802.11g network by entering this command:

config {802.11a | 802.11b} beamforming global {enable | disable}

Override the global configuration and enable or disable ClientLink for a specific access point by entering this command:

config {802.11a | 802.11b} beamforming ap Cisco_AP {enable | disable}

Verification:

(WLAN1) >show 802.11a
 802.11a Network.................................. Enabled
 .
 .
 .
 Beacon Interval.................................. 100
 CF Pollable mandatory............................ Disabled
 CF Poll Request mandatory........................ Disabled
 CFP Period....................................... 4
 CFP Maximum Duration............................. 60
 Default Channel.................................. 36
 Default Tx Power Level........................... 1
 DTPC  Status..................................... Enabled
 Fragmentation Threshold.......................... 2346
 TI Threshold..................................... -50
 Legacy Tx Beamforming setting.................... Enabled
 Traffic Stream Metrics Status.................... Disabled
 Expedited BW Request Status...................... Disabled
 World Mode....................................... Enabled
 EDCA profile type................................ default-wmm
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