Beamforming In Clientlink 1.0 And 2.0 - Cisco Aironet 1600 Deployment Manual

Cisco aironet 1600/2600/3600 series access point

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802.11n, Spatial Streams, and Beamforming

Sometimes it can be difficult to reliably maintain a 3SS link, since it is easy for the client to rate-shift

Note

out of the 3SS mode. The ability to maintain a 3SS link varies with the quality of the client and the test

environment.

The AP 3600, with its extra radio per band, can use the extra redundant radio to beamform (thanks to

ClientLink 2.0) and uses this to maintain the advantage of 3SS links. ClientLink 2.0 can also improve

the overall performance of 802.11n clients using one, two, and three spatial streams and legacy .11a/g

clients.

Beamforming in ClientLink 1.0 and 2.0

ClientLink 1.0 was first introduced with the AP 1250 and the AP 1140; it is a method to create a stronger

signal on the downlink side for 802.11a/g clients by hearing the clients on the uplink and then adjusting

the transmitter timing so the signal appears much stronger at the client end.

This feature was previously user configurable. However, starting with 7.2 code stream, it is now on by

default and is not user configurable because there is no benefit to disabling it.

The AP 3600 fully supports ClientLink 1.0 for 802.11a/g clients but has a greater advantage, for it also

supports all 802.11n clients including one, two, and three spatial stream clients. This capability is called

ClientLink 2.0. There is a distinct advantage with ClientLink 2.0 over the 802.11n enhanced

beamforming specification, because ClientLink 2.0 works with all clients today and does not require any

client sounding or support. (See

Figure

55.)

Figure 55

ClientLink 2.0

With beamforming technology, changing the timing of two transmitters creates a stronger signal for the

receiver (for example, a client device). This is referred to as constructive interference. If the opposite

happens, and the signals cancel each other out, it is called destructive interference. (See

Figure

56.)

Cisco Aironet 1600/2600/3600 Series Access Point Deployment Guide

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