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11ac's First Wave: What to Expect

Posted by Lisa Phifer
February 27, 2013

The emerging 802.11ac standard promises significant performance enhancements over the current 11n standard, including an eye-popping 7Gbps maximum throughput. But as vendors begin to roll out pre- or draft-standard products, what performance can you realistically expect? You'll get increases in rate over range, individual throughput, and aggregate capacity, but don't bank on 7 Gbps any time soon.

11ac is a grab-bag of incremental refinements that largely build on lessons learned during 11n to eke more out of the same technologies. Like 11n, 11ac uses wider channels to increase throughput. 11n combined 20 MHz-wide channels into 40 MHz pipes. Early draft 11ac products will pick up where 11n left off by combining 40 MHz-wide channels into 80 MHz pipes.

Eventually, final 11ac products will offer the option of 160 MHz channels, although it's not clear whether enterprises will choose to use big chunks of spectrum this way.

11ac also boosts data rates by packing four times the number of bits into each transmission. The standard increases Quadrature Amplitude Modulation (QAM) symbol density from 11n's 64 QAM to 11ac's 256 QAM. But there's a catch: 256 QAM can only be used over short distances--perhaps 20 feet in early draft 11ac products. Otherwise, 11ac products will drop back to 64 QAM.

Like 11n, 11ac uses multiple-input multiple-output (MIMO) and simultaneous streams to boost max data rates and aggregate capacity. But where 11n APs could support up to 4 transmit and 4 receive streams (4x4), 11ac APs will double up to 8x8. However, most vendors expect early draft 11ac APs will stay with 4x4, focusing instead on other 11ac tweaks.

For more on vendor plans for 11ac, and how to prepare for the new standard, see the report "Is Your WLAN Ready for 802.11ac?" Registration is required.

Vendor Outlooks on 11ac
Vendor	Draft 11ac	Released As	Customer Guidance
Aruba Networks	Early 2Q 2013	New APs	Migrate to 5 GHz, deploy 11ac in a targeted fashion to extend 11n WLANs, looking at user behavior to choose mix of rates and widths.
Aerohive Networks	1H 2013	New APs	Get started with 11ac by dropping new APs into existing WLAN to increase user density in hotspots and learn how 11ac performs.
Meru Networks	Mid- to late 2013	New APs	Use $499 investment protection coupon to trade in 11n APs for 11ac, mounted in same brackets to facilitate swap-out.
Motorola Solutions	3Q 2013	New APs	11n has still has long life; majority of customer base will wait for second wave. Use WLAN Planner to evaluate implications.
Xirrus	Mid-2013	New module	Deploy field-upgradable XR-2200 Wireless Array with two open slots for modular 11ac APs (may be pre-purchased at discounted price).
Meraki	1H 2013	New APs	Most customers are not waiting for 11ac; use Cloud Controller predictive analysis to identify where to drop in 11ac APs.
Ruckus Wireless	Mid-2013	New APs	Think about AP density and plan for 5 GHz coverage. Draft 11ac may be underwhelming if goal is max capacity -- focus on second wave.
Cisco Systems	1H 2013	New module	Deploy AP3600 with 4x4 11n radio, field-upgradable to new 11ac module. A new 11ac AP will follow three to six months later.
Data: InformationWeek Reports -- S6151112/2

Shifting Into High Gear

In addition to the above improvements, 11ac deviates from 11n in two significant ways. First, 11ac abandons the overcrowded 2.4 GHz band and will operate only in cleaner 5 GHz airspace. Second, 11ac introduces a new technique dubbed Multi-User (MU) MIMO that will use beamforming to simultaneously transmit/receive independent streams, letting a single AP communicate with up to 4 clients at once.

Reducing interference and competition by moving to the 5 GHz band can increase data rates, even without tossing in 256 QAM or extra antennas. And 5 GHz is a necessity to use 80 or 160 GHz channel widths. So expect to see these benefits emerge in new 11ac products this year – including single-stream smartphones that will enjoy better battery life by transmitting faster, for shorter periods.

However, MU-MIMO won't appear until the second wave of 11ac products in 2014-2015. Until that happens, Gigabit Wi-Fi can't hit that monster 7 Gbps data rate promised by the standard. In the meantime, expect to see Wi-Fi certified draft 11ac single-stream clients reaching 433 Mbps and APs transmitting up to 1.3 Gbps. These rates still blow away the best of today's 11n products. If you set your expectations appropriately, you won't be disappointed.

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Lisa Phifer is president of Core Competence, a consulting firm focused on enterprise adoption of emerging network and security technologies. Lisa has been involved in the design, implementation and evaluation of networking, security and management products for 30 years.

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