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Another milestone for 802.11ac and gigabit wireless LANs

By Matthew Gast and Praveen Mehrotra of Aerohive Networks, special to Network World
November 22, 2011 11:14 AM ET

Network World - This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter's approach.

One-gigabit wireless LAN products should enter the retail channel for the 2012 holiday season thanks to the fact that the 802.11 working group concluded balloting on the proposed 802.11ac standard last summer, meaning enterprise-focused products should follow in 2013.

Interest in 802.11ac is explained simply by the desire for speed. In homes, the complexity and challenges of A/V or other multimedia distribution and streaming is a catalyst for higher-speed networking, as is anything that improves gaming performance. Enterprise networks may not have as glamorous a need for higher speed, but depend on increasing bit rates to improve user experiences in high-density areas such as conference rooms and auditoriums, improve data service to mobile Internet devices, background synchronization between devices, and support more lifelike video systems.

802.11ac is an evolutionary step in the development of wireless networking (see our earlier article on development of the standard). Previous 802.11 technologies have operated in the now-familiar 2.4GHz and 5GHz bands, and the 802.11ac project began with a project authorization at the IEEE that focuses the effort at less than 6GHz.

IN DEPTH: Wi-Fi devices crowd 2.4GHz band; IT looks to 5GHz

Even with a wide project authorization that covers both the 2.4GHz and 5GHz frequency bands, the task group developing 802.11ac has decided to focus the new standard on only the existing 5GHz band because much of the benefit from 802.11ac's underlying technologies is derived from wider channels. We don't expect that dual-band APs will go away any time soon because there are so many devices that are 2.4GHz-only. To continue to build dual-band APs, the industry will build dual-technology APs with 802.11n remaining the capstone technology at 2.4GHz, and 802.11ac offering higher speeds in the 5GHz band.

Like 802.11n, 802.11ac is a complex standard with many features. For example, 802.11ac specifies more than 300 data rates, though not all will be available in early products. As a result, the industry will follow a similar pattern of adoption. Early implementations will offer a basic set of high-value features and as hardware engineers refine and perfect designs more advanced features will follow.

In the initial wave of products, devices will offer speed improvements over existing 802.11n devices by increasing channel width. 802.11ac includes both the familiar 20MHz and 40MHz channels, and adds new options for 80MHz and 160MHz channels.

As the channel width increases, the challenge of clearing the entire band for transmission becomes more difficult. Part of the challenge is technical, due to the need of radio devices to perform more computationally intensive Fourier transforms to cover the wider band, and part of the problem is that the load on the spectrum is much higher.

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