Ieee802.11N

White Paper

802.11n: The Next Generation of Wireless Performance
Executive Summary
The IEEE 802.11 Working Group has now completed 802.11n, the multiyear effort to standardize an upgrade to the 802.11 radio specification. 802.11n provides a new set of capabilities dramatically improving the reliability of communications, the predictability of coverage, and the overall throughput of devices.There were no additional mandatory features introduced between the widely adopted draft 2.0 version of 802.11n and the final version. Therefore, customers who already have chosen the draft 2.0 devices can continue to operate these devices with confidence and without any hardware or software changes. Also, those who have been holding back waiting for the standards to be finally ratified beforemoving over to the 802.11n can start migration now. The 802.11n protocol has several enhancements in the physical layer and the MAC sublayer that provide exceptional benefits to wireless deployments. The four critical features are:
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Multiple-input multiple-output (MIMO). MIMO uses the diversity and duplication of signals using the multiple transmit and receive antennas.

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40-MHz operationbonds adjacent channels, combined with some of the reserved channel space between the two, to more than double the data rate.

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Frame aggregation reduces the overhead of 802.11 by coalescing multiple packets. Backward compatibility, which makes it possible for a/b/g and draft 2.0 802.11n devices to coexist, thereby allowing customers to phase in their access point and/or client migrationsover time.

This white paper describes these new capabilities in detail, explains how the benefits provided by 802.11n are achieved, and examines the compatibility of this new standard with existing deployments. This white paper also describes the issues to address when planning migration of an existing 802.11a/g deployment to 802.11n and the results that can be expected from such a migration.But first, it is important to understand just what 802.11n is, and what it is not.

The Role of the IEEE and the Wi-Fi Alliance
802.11n was a seven-year endeavor at the IEEE, with three major phases: Study Group, Task Group, and Sponsor Ballot. The High Throughput Study Group first met on September 11, 2002, and this led to the 802.11n Task Group a year later. Considerable work ensued to explorethe core set of features that provided the maximum benefit for the broadest set of devices. These features were finalized in draft 2.0. Cisco provided valuable leadership toward robust backward compatibility and the security of the enhanced protocols. The Wi-Fi Alliance, an industry organization that provides interoperability certification for 802.11 devices, first began certifying theinteroperability of draft 2.0 802.11n devices in June 2007. The certification tested the core features of 802.11n. The program was broadly adopted by the Wi-Fi vendors and their equipment enjoyed strong market penetration. To date, several hundred draft 2.0 802.11 products have been certified by the Wi-Fi Alliance, and several tens of millions of devices have been deployed worldwide.

© 2011 Cisco and/orits affiliates. All rights reserved. This document is Cisco Public Information.

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Over time, the IEEE progressed on the other functionality that was incompletely addressed by draft 2.0. At each revision of the draft, optional features, providing incremental customer benefits, were refined. This process continued until June 2009 and draft 11.0. The official version of 802.11n isthe one produced by the 802.11 Working Group and ratified by the IEEE. This version was ratified by the IEEE Standards Board on September 11, 2009. Underpinning discussions on changes to 802.11n after draft 2.0 was the strong goal of the Wi-Fi Alliance and its members to ensure that differences between the final ratified 802.11n standard and 802.11n draft 2.0 were such that any device built to the...