December 11, 2012

Wi-Fi Goes Short and Fast-802.11ad

Some important developments in the Wi-Fi arena were highlighted in my last TechNote, following my recent return from the Interop trade show in New York City.  

The CEO of the Wi-Fi Alliance, Edgar Figueroa moderated a panel "Wi-Fi: Gigabit Performance (and a whole lot more!)" The Director for Standards and Business Development at Realtek, Sean Coffey talked about 802.11ac and the Marketing VP at Wilocity, Mark Grodzinksy outlined developments with 802.11ad. We're going to talk about the latter of those two standards in this TechNote.

So Where Does IEEE 802.11ad Fit?

Most of the talk has been about 802.11ac, which fits into the current model of Wi-Fi and will be the successor to the current 802.11n. By combining wider channels (up to 160 MHz versus 20- or 40 MHz in 802.11n), more efficient coding (256QAM versus 64QAM in 802.11n), and additional multiple input-multiple output (MIMO) streams (eight streams versus four in 802.11n) 802.11ac will push the maximum Wi-Fi data rate from 600 Mbps to a potential 6.934 Gbps. That's a 10x increase in capacity.

The 802.11ad is a second gigabit Wi-Fi standard, but it takes Wi-Fi in a different direction and will serve a new and different set of applications. Wilocity's Grodzinksy acknowledged this standard is in a much earlier stage of development and that it's still unclear when the first products will appear.

The big difference is that 802.11ad will operate in the 60 GHz band. There are few applications in the 60 GHz band primarily because the signal loss is so high relative to 2.4 GHz and 5 GHz.  Higher loss translates into a much shorter transmission range. As a result, 802.11ad will not be capable of supporting transmissions between access points and devices dozens of meters apart. Rather, 802.11ad will be used for in-room wireless connections.

One major advantage of moving to 60 GHz is that there's a lot of spectrum to work with in that band. Mr. Grodzinksy says there is roughly 7 to 9 GHz available throughout most of the world, versus about 0.5 GHz in the 5 GHz band and 0.0835 GHz in the 2.4 GHz band. His company, Wilocity currently makes the Wireless PCI Express (wPCIeTM) cable replacement solution that also runs in the 60 GHz band. 

Potential for 802.11ad

The current plans for 802.11ad will have it operating on a 2 GHz channel, meaning a single 802.11ad channel will have more bandwidth than what's available in the entire 2.4 GHz and 5 GHz bands combined. While it will operate in a very wide channel, the initial implementations will use a relatively simple modulation scheme and no MIMO capability. The result is that 802.11ad will deliver data rates up to around 7 Gbps at the outset. Mr. Grodzinksy pointed out that you can do uncompressed 1080P HD video in around 3 Gbps. 

Longer term they expect to increase the efficiency of the modulation scheme much as we saw with the progression from 802.11b, to g, then a, and n. As those more efficient techniques are brought to bear, the data rate could potentially go to 25 Gbps.

To compensate for the high signal loss, 802.11ad will use directional antennas that can focus the radio beam into a six-degree angle. Even with that narrow beam, 802.11ad still can only be used for in-room applications. A six-degree beam means that you may have to aim the devices at one another, though there is an option to incorporate beamforming so the two devices could "find each other" and aim the beam automatically.

Two applications are leading the way in discussions centering on 802.11ad.The first is wireless connections for computer peripherals that would not only clean up the mess of cables we find behind our desks, but also allow more flexible peripheral sharing from mobile devices. Wilocity's Wireless PCI Express fits in that category today. The other application is in consumer electronics for wirelessly connecting stereo equipment, HD televisions, and gaming systems.


Products based on 802.11ad are still a few years away, but it is clearly taking Wi-Fi in a new direction. In terms of range, 802.11ad has more in common with Bluetooth than traditional Wi-Fi, though with way more than the three Mbps transmission rates we get on Bluetooth version 2 interface today. The development of 802.11ad is yet another indication that Wi-Fi is not going away any time soon, but even if this new variant fails to catch on, there will still be billions of traditional Wi-Fi devices out there.


It looks like 802.11ad is focused on both the computer and consumer entertainment markets. Am I reading that right?

Absolutely. Of course when you consider that traditional Wi-Fi is deployed in tens of millions of homes, it's already pretty much a "consumer" technology. However, 802.11ad will expand that consumer focus to include home entertainment as well as home Wi-Fi. For us enterprise users, I'm not sure if it will have much of an impact on the Wi-Fi products we currently buy, but it could be a plus in video teleconferencing rooms.

It means advance version of Bluetooth… right?

Probably not.

Bluetooth seems to be "stuck in time" with a short range (generally 10m) and a relatively low data rate (

So, does this mean that each device incorporating 802.11ad will have an external patch antenna sticking out that will need to be aimed at neighboring devices with which to connect? Speaking of antennas, are we talking just one, or multiple, so as to take advantage of spatial streams? And I guess it's assumed that 802.11ad will be client-to-client (ad hoc), rather than client to AP (like WiFi)? This is reminding me of the old bunny ears antennas that TV's use to have. You adjust the antenna just right to get the best picture. I really hope I won't need to do this so my TV and Blu-ray player can connect to each other successfully.

Great question, joker!
1) A patch antenna (probably not "bunny ears") is one potential option, and yes, you'd have to aim it. There is an option in the standard for beam forming which would allow the two devices to "discover" each other and then aim the beam automatically- but it's an "option" so we'll have to see if we get it. (By the way, this is the very question I asked when I first heard about this).

2) At the outset there would be only one antenna. The first pass at this is not going to include MIMO and will be using a fairly rudimentary signal encoding (i.e. 7 Mbps in a 2 GHz channel is only 3.5 bits/second/Hertz- 802.11n can get 15 bits/second/Hertz). However just like 802.1b led to 802.11g and then to 802.11n, more efficient techniques (including MIMO with a requirement for multiple antennas) can be added to the standard over time.

3) Yes, this will be more in the ad hoc vein with two devices (e.g. a flat screen TV and a cable box) connecting to one another.

4) We're Layer 1/Layer 2 here, buddy! Blu-ray compatibility is someone else's job!

Thanks for the questions!

Is there any talk about 802.11ad hubs that implement antenna arrays (multiple directional antennas) that go out in 360 degrees? With something like this, we wouldn't need to ensure that our set-top box is pointing to the TV - which is highly unlikely to happen. I really don't see people willing to point their larger devices at each other - they go where they go. What good is having devices communicate wirelessly if you can't put them where you want them? If this process isn't made really simple, I don't see 802.11ad gaining very many users.

On a related note, the Wi-Fi Alliance and WiGig Alliance just agreed to merge:

The WiGig Alliance has been working on getting Steve's TV and BluRay player to talk, using the 60 GHz wireless technology that has now evolved into 802.11ad.

As noted in the press release, "WiGig offers short-range multi-gigabit connections for applications ranging from high-definition WiGig Display Extensions (WDE), to peripheral connectivity and I/O cable replacement such as WiGig Serial Extension (WSE), WiGig Bus Extension (WBE) and WiGig SDIO Extension (WDS). Early 60 GHz implementations based on the WiGig specifications are entering the market now and ABI Research forecasts that by 2016, annual shipments of devices with both Wi-Fi and WiGig technology will reach 1.8 billion."

The Wi-Fi Alliance / WiGig Alliance merger is an important step towards seamless unification of 802.11ac and 802.11ad - specifically, these organizations will work on helping to products that speak both 11ac Wi-Fi on a WLAN and 11ad WiGig on a WPAN to move traffic between the two networks and even roam between the two in an interoperable fashion when the situation calls for it. I wrote about this briefly in my TechNote, written right after CES 2012:

Expect a lot more news on this front next week as vendors announce new 11ad and 11ac products at CES 2013.

It will be the greatest wireless movement. This means 802.11ad will replace 802.11 a/b/g/n or just mixed in with all of that technology? How about the spectrum especially in 57 - 66 GHz.; is that available in all countries? Thanks for the explanation.

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