Doc.: IEEE 802.11-06/1006r0 July 2006 July 2006 Supporting information for eliminating Section 5.7 "OTA Shielded Enclosure Environment" Date: 2006-7-17 Authors: Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. Dr. Michael D. Foegelle, ETS-Lindgren Dr. Michael D. Foegelle, ETS-Lindgren

Doc.: IEEE 802.11-06/1006r0 July 2006 July 2006 Abstract This presentation illustrates the problem with using an unqualified shielded room as an environment for OTA testing. It is provided as supporting evidence for comment 240 in document 11-06/0872r1. bet Dr. Michael D. Foegelle, ETS-Lindgren Dr. Michael D. Foegelle, ETS-Lindgren

Shielded Rooms Comment on section 5.7: July 2006 Shielded Rooms Comment on section 5.7: A pure shielded environment does not give an RF channel suitable for OTA testing. A shielded room is intended to isolate devices/systems within the room from the outside environment, either to protect those devices from outside interference, or to protect the environment outside from interference due to the tests performed in the shield. It is NOT intended for testing of OTA propagation. There will be far too much multipath fading for realistic results. It should not be recommended to use an unqualified shielded environment (i.e. without specifying some level of lossy materials, etc. within that environment). Beyond that, this environment is redundant to the COTA environment. Dr. Michael D. Foegelle, ETS-Lindgren

July 2006 Shielded Rooms Shielded room (screen room) provides isolation but metal walls cause excessive multipath. Far exceeds number of paths found in real world. Dr. Michael D. Foegelle, ETS-Lindgren

July 2006 Shielded Rooms Symmetry causes multiple identical paths for deeper fading than typically found in real world. Signals reinforce each other in or out of phase. Dr. Michael D. Foegelle, ETS-Lindgren

July 2006 Shielded Rooms Energy bounces around until absorbed by other objects in the room or losses in walls. Unpredictable from site to site. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Using a vector network analyzer, a NLOS arrangement was tested in several environments and the results compared. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments The first environment was a conference room showing typical real world physical channel. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Frequency response shows typical multipath fading expected in 802.11 physical channels. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments The second environment was a small shielded control room with considerable loading. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Frequency response shows similar physical channel, but nulls are deeper and average signal level is higher. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments The third environment was a large shielded room (reverb chamber) with little loading. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Physical channel is drastically different, with many more nulls and much higher signal levels. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Time Domain (from 5-6 GHz) shows expected exponential fall-off vs. path length for conference room environment. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Small shielded room with some loading shows higher initial pulse power levels and more linear fall-off. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments Large shielded room with negligible loading (High Q) shows very little decay over long paths. Dr. Michael D. Foegelle, ETS-Lindgren

Example Comparison of Environments July 2006 Example Comparison of Environments It’s evident that a shielded room doesn’t provide real-world physical channel, and therefore results won’t be reproducible without additional requirements. Dr. Michael D. Foegelle, ETS-Lindgren

July 2006 Conclusion COTA environment defines an OTA environment with a reproducible physical channel. Section 5.7 should either be removed from the test plan and related topics harmonized with COTA environment. Dr. Michael D. Foegelle, ETS-Lindgren

July 2006 References 1.       IEEE 802.11-06/0872r1, “Comments from TGT Internal Review ,” C. Wright. Dr. Michael D. Foegelle, ETS-Lindgren