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Most enterprise 802.11n wireless LANs deliver speeds between 450 Mbps and 600 Mbps -- not too shabby. But this is one area where you can't rest on your laurels.
To meet our ever-growing need for speed, the IEEE is working on Enhancements for Very High Throughput for operation in bands below 6 GHz, commonly known as the 802.11ac Wi-Fi standard. Wi-Fi certified products based on a draft of this standard will likely emerge by mid-2013, boosting maximum data rates above 1 Gbps. By late 2014 or early 2015, products aligned with the final 11ac standard will nudge the Wi-Fi speed limit closer to 7 Gbps. For IT, 11ac promises room for growth by focusing on less-cluttered 5-GHz channels, doubling or quadrupling channel widths, using more efficient encoding, doubling maximum spatial streams and eventually letting wireless access points service multiple clients simultaneously.
These benefits are appealing, but IT teams that have barely finished migrating to 802.11n may justifiably wonder why they can't sit back for a year or so. After all, didn't 11n just increase speed an order of magnitude over the 11a/g standard?
Yes, but many 11n WLANs are already suffering growing pains. First off, the small, crowded 2.4-GHz "junk band" has grown far too congested; 11ac kicks migration to 5 GHz into high gear by avoiding 2.4-GHz channels entirely. Second, while many applications operate fine at 11n speeds, some need higher throughput. For example, delivering uncompressed high-definition video to a Wi-Fi display requires 1.5 Gbps to 3 Gbps. Finally, and perhaps most painfully obvious to IT, bring-your-own-device programs have caused an explosion in the number and diversity of Wi-Fi devices access enterprise WLANs. And wireless carriers are encouraging people to off-load smartphone browsing to Wi-Fi to conserve scarce spectrum.
To keep your company's mobile initiatives on track, you'll need 802.11ac. The spec really does make some technological leaps. A biggie is multiuser multiple input, multiple output, or MU-MIMO, an advanced option that lets 11ac access points (APs) simultaneously service as many as four devices at once, using diverse spatial streams to communicate with each other. Today's APs operate similarly to how a single-core CPU handles multiple application processes "at the same time" -- in fact, it's really just rapidly switching among them. With MU-MIMO, an 11ac AP can operate similarly to a multicore CPU -- that is, using different transmit/receive chains to communicate with different users simultaneously.
The new spec also brings incremental improvements in key areas, including modulation, channel width, spatial streams and transmit beamforming. We discuss these in our full report.
Bringing 11ac To Market
As usual, we'll see two distinct Wi-Fi product waves. The first will be based on Draft 4.0 of the emerging IEEE 802.11ac amendment, followed by a second wave aligned with the final IEEE specification, which is expected in the first quarter of 2014. The Wi-Fi Alliance plans to launch a draft AC program in the first half of next year, focused on elements that are in near-final form. "We will avoid areas that we expect might undergo more work in the IEEE," says the group's technical director, Greg Ennis. "However, we're expecting there won't be significant changes to the text of the final standard."
Some consumer "pre-11ac" products are already available from vendors such as Buffalo, D-Link, Netgear and Cisco/Linksys. As for the enterprise, Broadcom product line director Michael Powell says adoption will be driven by the wave of phones, tablets and laptops that employees are bringing to work and that IT teams are scrambling to support. Powell expects to see notebooks with 2x2 11ac by year's end and 3x3 in early 2013. By the third quarter of 2013, 70% of smartphones will ship with 11ac -- mostly single-stream, he says. Still, enterprise WLAN vendors are actively developing 11ac while continuing to sell 11n APs; we break down their plans (see on next page).
The key to reaping business benefits from 802.11ac is a smart plan for if, when and where to deploy. After all, widening a highway from two to four lanes is meaningless if it's traveled by just a few cars. Likewise, 11ac may add 80-MHz channels, but does your workforce really need them?
To prepare, take stock of your current and expected employee devices, your current WLAN setup and the technical particulars of 802.11ac. "Smartphones and tablets may prefer a single stream with wider channels to extend battery life," says Manish Rai, VP of marketing at Meru Networks. "In higher education, seasonal [churn], new devices and the number of devices doubling each year makes client density more important. And that is very different than backhaul, video surveillance or healthcare imaging, where 11ac must be optimized for capacity."
11ac's biggest single benefit is increased capacity, says Matthew Gast, Aerohive Networks' director of product management. "If you have a mix of laptops and tablets, 11ac will drive more time to tablets," says Gast. That's because laptops and tablets share airtime on a channel, and 11ac will let more-capable laptops operate at faster speeds and thus take a lot less time to transmit. That will free up airtime for less-capable devices like tablets, meaning new APs will increase performance even for older devices. "The first wave [of 11ac] might not bring multiuser nirvana, but it will still offer measurable improvements," says Gast. "Even if everyone operated at 48 instead of 36 Mbps, that alone would have a big impact."
Whether you're itching to deploy Wi-Fi Certified draft ac as soon as products hit the shelves or looking for a slow rollout once final 11ac APs with MU-MIMO become available, start planning for an upgrade. Plan around peak capacity rather than coverage, says Chris Spain, VP of marketing for Cisco's wireless business unit. As your mobile workforce and dependence on mobile applications grow, you'll be well-positioned to tap 11ac to increase user density.
This dense deployment technique is already becoming a best practice for large 11n WLANs, at least in locations with lots of devices accessing them. Is the distance covered by 11ac at 5 GHz different enough from 11n at 5 GHz that you'd want to put your new APs in different locations? Yes, if you can start from scratch, because rate over range will improve for 11ac. But in general, redesigning an AP layout for 11ac probably isn't worthwhile.
Begin tracking client density and bandwidth utilization per application to see where your WLAN is hitting a wall. Migrate high-throughput applications to 11n 40-MHz channels now; that will help you learn where 40 MHz is sufficient and pinpoint cases where it isn't. As with 11n, 11ac APs will require more power to fuel additional transmit/receive chains and antennas. Early indications are that 802.3af Power-over-Ethernet won't be adequate, says Gast. Eventually, you'll need 802.3at PoE+ for 11ac, but that shift will probably happen during normal upgrades to Gigabit Ethernet switches anyway.
Speaking of wired network backhaul, 11ac is another reason to perform a wired network audit, assessing existing capacity, identifying potential bottlenecks and budgeting equipment upgrades to meet growing demands. For example, will your WLAN controllers need to be upgraded along with 11ac APs? Also plan ahead for network management, troubleshooting and wireless IPS updates.
Finally, talk to your WLAN infrastructure vendors about their 11ac upgrade paths and options to minimize expense and protect past investments. No matter how bullish you are on 11ac, client migration will occur gradually over several years. So think in terms of mixed 11n/11ac deployments, using equipment refresh to bring your WLAN into the fifth generation of very-high-throughput 802.11ac.
Lisa Phifer is president of IT and security consultancy Core Competence. Write to us at firstname.lastname@example.org.