Client Link (know as beamforming as well) 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). ClientLink uses multiple transmit antenna to focus transmission in the direction of a 802.11a or 802.11g client ( true for WLC 7.0.116.0 code & later releases with 3600 may support this for n clinets as well- Called ClientLink 2.0) which increases the downlink SNR and the data rate to the client, reduces coverage holes & enhance overall system performance. Below diagram shows graphical representation of effect of client link.
ClientLink starts only when signal from the client falls below these thresholds:
802.11a clients – RSSI of -60 dBm or weaker
802.11g clients – RSSI of -50 dBm or weaker
AP actively maintains ClientLink data for upto 15 clients per radio.
When configuring ClintLink following guideline should followed.
1. ClientLink is supported only for legacy OFDM data rates (6,9,12,18,24,36,48,54 Mbps)
2. Only APs that support 802.11n can use client link
3. Two or more antennas must be enabled for transmission
4. OFDM data rates must be enabled.
Following screen “Wireless -> 802.11b|802.11a ” shows the setting to enable client link.
You can override this and enable or disable it per AP. To do that you have to go to the required AP ” Wireless -> Access Points -> Radios > 802.11a/n or 802.11b/g/n” page. Below shows disabling clinet link for a AP (named LWAP-03)
By using CLI you can enable this as well. see below commands
config 802.11a|802.11b beamforming global enable|disable config 802.11a|802.11b beamforming ap <AP_name> enable|disable
You can verify this by “show 802.11a” or “show ap config 802.11a <ap_name>” CLI commands as shown below.
(WLC1) >show 802.11a . . 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........................... 0 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................................ optimized-video-voice (WLC2) >show ap config 802.11a LWAP-03 . . Phy OFDM parameters Configuration ............................. AUTOMATIC Current Channel ........................... 40 Extension Channel ......................... NONE Channel Width.............................. 20 Mhz Allowed Channel List....................... 36,40,44,48,52,56,60,64,149,153,157,161,165 TI Threshold .............................. -50 Legacy Tx Beamforming Configuration ....... AUTOMATIC Legacy Tx Beamforming ..................... ENABLED Antenna Type............................... INTERNAL_ANTENNA Internal Antenna Gain (in .5 dBi units).... 8
.
Related Posts
1. RRM Basics
2. Configuring RRM
3. Configuring DCA
4. Configuring TPC
5. Configuring CHD
6. Overriding RRM
7.
8. Rogue Access Point Detection
