Clients That Support 3 Spatial Streams - Cisco Aironet 3700 Series Deployment Manual

Clients that Support 3 Spatial Streams

Clients with 3SS support are starting to become commonplace. Because the new 802.11ac specification
starts to get traction, many newer client adapters will have the newer chipsets and support 3SS as a subset
to 802.11ac. Additionally, unlike many of our competitors the Cisco AP 1600/2600/3600 and 3700 fully
supports all the DFS channels for more usable channels in the 5 GHz range. More clients, especially
802.11ac clients, will start to emerge supporting these newer channels in 802.11n modes as well.
Currently the most popular 3SS client is the Apple 2011 MacBook Pro, because it is based upon the
Broadcom BCM4331 chipset and a small USB adapter by Trendnet, "TEW 684UB", based on the Ralink
chipset.
Additionally, the Intel 5300 and 6300 has supported 3SS for a long time. Perhaps, because of the
different hardware platforms this card is installed in, testers have observed good throughput on many
notebooks (+320 Mbps) and reduced throughput on other notebooks such as 240 Mbps. If you experience
low throughput using the Intel card, one suggestion might be to try a MacBook Pro or Trendnet adapter,
and if they perform well try another notebook with the Intel card or perhaps open a case with Intel or the
laptop manufacturer for a possible remedy. During the AP 3600 beta trials, we observed differences in
performance with different notebooks using the Intel 6300 card.
Sometimes it can be difficult to reliably maintain a 3SS link because it is easy for the client to rate-shift
Note
out of the 3SS mode. The client plays an important role in the ability to maintain a 3SS link, so it can
vary with the quality of the client being used and the test environment.
The AP 3600 with its extra radio per band can use the extra redundant radio to beamform (because of
ClientLink 2.0) and uses this to maintain the advantage of 3SS links. Cisco ClientLink 2.0 can also
improve the overall performance of 802.11n clients using 1, 2, and 3 spatial streams and legacy .11a/g
clients.
Understanding Beamforming – Legacy ClientLink 1.0 and 2.0
ClientLink 1.0 was first introduced with the 1250 and 1140 series APs; it is a method of creating 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 used to be user configurable; however, starting with 7.2 code stream it is now switched on
by default and is not user configurable as 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 because it
also supports all 802.11n clients including 1, 2, and 3 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 (Figure 33).
Cisco Aironet Series 2700/3700 Access Points Deployment Guide
Cisco Aironet Series 3700 Access Point
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