Everything You Need to Know about 802.11ac

Although 802.11ac is still not ratified, WLAN manufactures, cellphone device makers, and network monitoring and analysis companies are already starting to make products that are compatible with this new protocol. 802.11ac promises to deliver greater throughput at reduced power, simultaneous delivery of high-bandwidth data (like video) to multiple users, and better interoperability in the presence of existing commercial wireless devices and neighboring WLANs. In short, a substantial improvement, and that’s why everyone is jumping on the bandwagon.

In many ways 802.11ac is a “lessons learned” from 802.11n, specifying new technologies to deliver some of the more advanced features that 11n has yet to achieve, like 600Mbps (and more with 11ac) and less interference with existing Wi-Fi deployments. 802.11ac will offer better performance at any range, and is extremely well suited for mobile devices (battery life optimization) and multimedia streaming.

How is this technology able to provide all these benefits and when will you see it in your home or at the office? Below is all you need to know.

Progress on the Consumer and Enterprise Side
In the consumer market, Wi-Fi device manufactures are pushing hard to deliver 802.11ac devices, both APs and clients, even though the specification is still only in draft form. This is very similar to the way 802.11n rolled out, and that’s a sign that 11ac will also be big. As an example of this push to deliver, Michael Brown of PCWorld recently wrote a post that discusses his top five 802.11ac routers.

In the enterprise market, the adoption rate has not been as fast, but again, this follows the same pattern as with 802.11n. Although 802.11ac will clearly benefit the enterprise with its increased range, increased throughput, and ability to effectively deliver a whole new range of applications (mostly centered around multimedia), enterprises are also more likely to want the assurance of truly standard hardware (not draft level). Also, many enterprises need a more complete solution with WLAN controllers and management software, and these more complex products are still under development. Network analysis and monitoring are also primary concerns for enterprises, and although many wireless network analysis solutions are beginning to provide support for 11ac, the lack of both client-side and enterprise hardware makes it difficult for these solutions to fully qualify and support 802.11ac enhancements.

Improvements in 802.11n
802.11ac leverages many of the same key technologies as 802.11n, including channel bonding and MIMO (multiple input, multiple output), but it does it a bit smarter – lessons learned – as stated earlier. For example, channel bonding essentially doubles the data rate, regardless of other technologies in use, but it also reduces the available channels for use in your network, or your neighbor’s. This problem is much more severe in the 2.4GHz band than it is in the 5GHz band, since 2.4GHz channels are closer together (5MHz spacing vs. 10MHz), and the overall size of the band is smaller. Since many users are still deploying 11n in only the 2.4GHz band, mostly for backward compatibility with existing b/g clients, they don’t take advantage of channel bonding so as not to interfere with their current channel layout.

802.11ac is specifically designed for the 5GHz band, which offers more channels with wider channel spacing, and is therefore far less sensitive to the impacts of channel bonding. And besides, the 5GHz band has far fewer sources of interference than the 2.4GHz band (like cordless phones, Bluetooth, microwave ovens, etc.) so the choice to limit 11ac operation to just the 5GHz band is a very good one.

Power Consumption Problems and Fixes
Currently, 802.11n is pushing the power limits, especially for mobile/portable devices, to the point where most portable devices cannot come close to taking full advantage of 11n capabilities. Just as an example, the iPhone 5 is capable of at most 150Mbps performance on an 11n wireless network, far short of the 600Mbps maximum for 11n. That’s because to achieve 600Mbps, the device would need to have four active transmitters in the 802.11n “chain,” basically consuming 4x the power. To keep battery life in the acceptable range, the iPhone 5 (and just about every other smart phone on the market) uses only one “transmit chain,” limiting the theoretical data rate to 150Mbps.

Through the use of more efficient data encoding mechanisms, 11ac allows devices to use fewer “transmit chains” while still achieving higher data rates. For example, in 11ac you’ll see a 3x improvement in data rate over 11n for the same number of transmit chains.

Geographic Differences Affecting the 5GHz Band
Not only does 802.11ac allow two channels to be bonded together, it actually allows as many as 4 channels to be bonded together, further increasing the maximum data rates. But geographic differences in the frequency allocations for the 5GHz band will lead to differences in the availability and number of wide-bandwidth channels in different countries. This may increase the manufacturing complexity of devices that are expected to ship worldwide, not to mention the marketing challenges, since equivalent hardware will have different capabilities in different geographic regions.

We should all be excited about 802.11ac. It promises to finally deliver on the promise of a truly wireless multimedia experience, and 802.11ac will likely be built into just about every consumer electronics device over the next few years. And for all those smart phone users – in other words all of us – the Wi-Fi user experience will be significantly improved as our new client devices support 11ac and 11ac networks become more common. It won’t change overnight, but it will likely become pervasive more quickly than we expect.

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