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The good, bad and ugly of 802.11ac

By Jay Botelho, director of product marketing, WildPackets, Network World
February 13, 2012 02:10 PM ET

Although vendor-written, this contributed piece does not advocate a position that is particular to the author's employer and has been edited and approved by Network World editors.

Imagine a world where family members can stream their favorite HD content to different rooms, all while your teenage son uploads his latest HD video "project" to YouTube. Well, with new wireless LAN technology based on 802.11ac quickly approaching -- possibly in one or two years -- this digital home network paradise could become a reality.

802.11ac leverages and learns from the advances offered with 802.11n, providing even greater throughput, simultaneous delivery of high-bandwidth data to multiple users, and better interoperability in the presence of existing commercial wireless devices and neighboring WLANs.

MORE: 802.11ac boosts buzz more than bandwidth

Compare that with what we have today with 11n, and we are looking at yet another major capability leap, both in terms of functionality and overall data delivery. Data rates will jump from the 600Mbps maximum with 11n to single client data rates up to 3.47Gbps with 11ac and total aggregate capacity of 6.93Gbps. Yes, we're talking wireless!

The good

WLAN equipment manufacturers are learning a great deal from 802.11n, and these lessons are clearly getting folded into 11ac. Two key features from 11n, MIMO (multiple-input, multiple-output) and channel bonding, form the foundation for 11ac enhancements, with a few more complex optional features.

The first really good thing about 11ac is that it is specifically designed for the 5GHz band. This frequency band provides greater flexibility for one of the key data rate enhancing features, channel bonding, which often goes unused in today's 11n equipment, since so much of that equipment is designed for the 2.4GHz band where channel bonding can cause serious interoperability issues. The 5GHz band offers more channels with wider spacing, and is far less sensitive to interference from other consumer devices, like baby monitors, wireless surveillance video cameras and microwave ovens. [Also see: "Wi-Fi devices crowd 2.4GHz band; IT looks to 5 GHz"]

Additional protocol enhancements are also being specified to make channel bonding less likely to cause interoperability issues. This includes things like the ability for devices to assess whether neighboring channels are clear and available for channel bonding, and for devices to reserve wider bandwidths in advance of data transmissions. This allows channel bonding to increase from 40MHz in 11n to 80 and even 160MHz under certain conditions in 11ac. Making channel bonding less invasive, and therefore used by default by wireless devices, is key to achieving the increased data rates in 11ac.

The second good thing about 11ac is that even though data rates are increasing significantly, power consumption is likely to decrease as compared to similar 11n capability, and this is a huge win.

802.11n is really starting to push 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. Through the use of more efficient data encoding mechanisms, 11ac allows devices to use fewer multiple transmissions paths while still achieving higher data rates, and it's the additional RF transmission chains that really eat up power.

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