802.11n+Generation

802.11n: The Next Generation of Wireless Performance
**he IEEE 802.11 Working Group has been working for the last few years to standardize an upgrade to the 802.11 radio that provides a new set of capabilities dramatically improving the reliability of 802.11 communications, the predictability of 802.11 coverage, and the overall throughput of 802.11 devices. This white paper describes these new capabilities, provides insight into how the benefits provided by [|802.11n] are achieved, and details how this new standard is compatible with existing 802.11 deployments. This white paper also describes the issues to confront when planning migration of an existing 802.11 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 IEEE Version and Ratification of 802.11n** The official version of 802.11n is the one produced by the 802.11 Working Group and ratified by the IEEE. This version does not exist yet. The 802.11 Working Group is in the process of developing a draft of 802.11n. This draft has been approved by an internal Working Group ballot, but a significant number of technical issues still need to be resolved before this internal draft is complete and ready for its next phase of approval. The Working Group anticipates that this phase of its work will be done in July 2008. Once the 802.11 Working Group completes its work on the 802.11n draft, the draft is sent for a "sponsor ballot." This sponsor ballot is run by the IEEE and consists of a variety of experts who review the draft once again. Based on comments received from the sponsor balloters, the 802.11 Working Group continues to update the draft until the sponsor balloters reach consensus that the draft is ready for final approval. The official 802.11 timeline for concluding this process and achieving IEEE Standards Board approval of 802.11n is March 2009. Only after 802.11n achieves final approval by the IEEE Standards Board is there an actual standard    802.11n Technology The goal of the work on 802.11n is to dramatically increase the effective throughput of 802.11 devices, not to simply build a radio capable of higher bit rates. The difference between these goals is like the difference between the mileage you achieve with your own, personal driving habits and the EPA-rated mileage for your model of car. To increase the effective throughput of an 802.11 device requires more than providing a higher bit rate. There are aspects of the 802.11 standard that are "overhead" for the 802.11 protocol. Many of these overhead aspects can't be reduced or eliminated. The effect is that, without using other methods, there is an absolute upper bound on the effective throughput. 802.11n is much more than just a new radio for 802.11. In addition to providing higher bit rates (as was done in 802.11a, b, and g), 802.11n makes dramatic changes to the basic frame format that is used by 802.11 devices to communicate with each other. This section will describe the changes incorporated in 802.11n, including MIMO, radio enhancements, and MAC enhancements.

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