Cisco Blogs
Share

Fundamentals of 802.11ac Wave 2


April 30, 2015 - 1 Comment
Fundamentals of 802.11ac Wave 2 from TechWiseTV

Fundamentals of 802.11ac Wave 2 from TechWiseTV

How well do you understand this Wave 2 release of the 802.11ac specification?  Our latest ‘Fundamentals of’ addresses the technical differentiators and the potential pitfalls you should be aware of.  There is a lot of power in this wave.

Just 5 Minutes to increase your knowledge: WATCH NOW

I put the full script at the bottom of this blog if interested.

Read more:

Watch some of the earlier wireless fundamentals for even more wireless innovation and (IMHO) great background:

Thanks for watching!

Robb
Follow me on Twitter: @robbboyd

Script

Wi-Fi technology is changing fast!  Wave 2 of 802.11ac is now rolling out on new access points.

How time flies. … 802.11b was cool.  Then g, a/g, and oh how ’n’ made all of it seem slow…until ‘ac.’

AC has been way better than N for most of us. It’s actually been rolling out in waves…if you have it right now, you probably have Wave 1.

Wave 2 is a Wi-Fi milestone as it can now out-perform wired ethernet.  It also has a few ripples that should be understood, so lets take a closer look.

Just matching the ‘ac’ specs does not mean matching the promised performance. 

Your unique conditions will make a difference certainly, but even before that…look closely at what you are getting because a sloppy implementation of this spec on the vendor side could be worse than just sticking with older models. 

Both waves of 802.11ac offer improvements by being wider, tighter and cleaner.

Wider with 80 MHz channel widths double that of 11n.  Now, there are even options for 160 MHz and larger frames that can share radio resources between channels of different sizes.

11ac also dramatically increases the data packed into each RF transmission through tighter modulation using 256 QAM.

And thankfully, the mandate for being in the 5 GHz band also results in a much cleaner interference environment.

I think we’ve gotten everything we can out of 2.4 GHz…lets leave it to the cordless phones, microwaves and older clients.

The most interesting technology within 802.11ac Wave 2, is Multi User-MIMO which offers much increased efficiency over Single User MIMO. 

Now multiple client devices can receive data simultaneously through MU-MIMO & beamforming.

Beamforming concentrates and steers the radio towards a specific client, instead of throwing a signal out in all directions hoping that it will hit something.

Beamforming with 802.11ac is “explicit,” which requires more frequent feedback between the AP and Client using an extended version of the channel sounding process to alter signal phasing and get a higher effective power level.

It’s also more efficient with how it comes on and off the air, which can effectively leave the RF open and more available.

This does NOT actually make the network faster.  It feels faster because it so much more efficient.

Cisco engineers have been giving us steady improvements on beamforming since 2008 with ClientLink.  Other vendors even have their own versions…

802.11ac now narrows all these methods to one.

Why is this better?  It helps to first understand Single-User MIMO.

SU-MIMO DEBUTED back with 802.11n using multiple antennas to send and receive more than one data signal on the same radio channel.

This was in response to natural interference from signals bouncing off objects.  These reflections arrive at different times and angles which would forc slower bandwidth.

SU-MIMO was able to provide a more robust link by, ironically, exploiting this multi-path ‘issue’ through the collective signal measured across these antennas.

It also operates in a serial fashion where each client device has to wait its turn, which means that all these mobile devices will sometimes cause a little strain.

A SU-MIMO AP can run out of time trying to sequentially rotate through each client causing them all to get lower bandwidth service.

Multi-user MIMO in 802.11ac Wave 2 offers us parallel service. By transmitting to multiple clients simultaneously, the access point can make full use of its “gigabit” capacity.

MU-MIMO also provides better support for single stream clients…all these mobile devices. 

This reason alone may be why you may put these new models on your shopping list.

There is a tremendous amount of engineering when beamforming to multiple clients at the same time, especially when so many are now moving around…

It is a required element within Multi-User MIMO and far more challenging as it really depends on how well each AP does the math.

It also may be one of the most difficult features for vendors to get right, so it pays to tread carefully.

6.93 Gbps is the published possibility, a 1500% gain over 11n.

Now these may not be the numbers you see when you deploy, but given all these improvements: Wider Channels at 5 GHz, tighter modulation schemes and more efficiency with MU-MIMO… it still adds up.

As you can tell, 802.11ac is only getting better.   

Maximum value from these new capabilities will truly be felt as new wireless endpoints continue to roll out.

Don’t forget to protect your cabling investment.

These access points are getting faster than the wiring they are connected to. 

Follow the work of the NBASE-T Alliance and new multigigabit switches that can preserve your cabling infrastructure and avoid potential bottlenecks.

These waves are looking good. My opinion?  Its time to ride.

In an effort to keep conversations fresh, Cisco Blogs closes comments after 60 days. Please visit the Cisco Blogs hub page for the latest content.

1 Comments

  1. The YouTube version of this 'WAVE 2' Fundamentals is out today too if needed.