Switch-to-Beamform Power Step January 2005 doc.: IEEE 802.11-05/1581r0 March 2005 Switch-to-Beamform Power Step Date: 2005-03-16 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>. Mark Webster, Conexant Systems Dave Hedberg, Conexant Systems

January 2005 doc.: IEEE 802.11-05/1581r0 Abstract March 2005 This presentation gives a couple of examples where the switch-to-beamform power-step can be more than 10 dB. The power step can be upward or downward. The impact of this behavior on legacy OFDM reception may warrant further analysis and testing. Legacy radios may not be certified to handle this behavior. Unlike 802.11b, OFDM does not have a CRC check on the Signal Field (header). Mark Webster, Conexant Systems Dave Hedberg, Conexant Systems

Outline Introduction Line-of-Sight Scenario Non-Line-of-Sight scenario March 2005 Outline Introduction Line-of-Sight Scenario Non-Line-of-Sight scenario Conclusions Mark Webster, Conexant Systems

Introduction Many possible beamforming scenarios exist March 2005 Introduction Many possible beamforming scenarios exist This presentation looks at only a couple of “quick-to-analyze” scenarios No impairments are included Only one type of beamforming is examined: one spatial stream A small set of channel types are examined All preambles/antenna transmission options are not examined The impact of multiple, small cyclic shifts is not examined The objective is to merely illustrate potential behavior More work will be required to fully scope this issue in terms of legacy radio behavior Mark Webster, Conexant Systems

TGn Sync Packet Structure with Beamforming March 2005 TGn Sync Packet Structure with Beamforming Power Discontinuity L-STF 8 us L-LTF 8 us L-SIG 4 us HT-SIG 8 us H-STF 2.4 us H-STF 7.2 us DATA Omni-Directional Beamformed Mark Webster, Conexant Systems

Line-of-Sight Scenario Described All STA’s are LOS (Multipath ignored) March 2005 Line-of-Sight Scenario Described All STA’s are LOS (Multipath ignored) Antenna Pattern Beamform-Mode LOS Target 11n Client Radio 11n AP 4 Element Linear Array Experiences Upward Power Step Antenna Pattern Omni-Mode LOS Legacy 11n Client Radio Experiences Downward Power Increase Mark Webster, Conexant Systems

LOS, 2 Element, 0.5 l, Beampatterns March 2005 LOS, 2 Element, 0.5 l, Beampatterns Target STA at 0 deg Target STA at 30 deg Target STA at 90 deg Target STA at 60 deg Mark Webster, Conexant Systems

LOS, 4 Element, 0.5 l, Beampatterns, Linear Array March 2005 LOS, 4 Element, 0.5 l, Beampatterns, Linear Array Target STA at 30 deg Target STA at 0 deg Target STA at 90 deg Target STA at 60 deg Mark Webster, Conexant Systems

Power-Step CDF’s Around Azimuth One Spatial Stream March 2005 Power-Step CDF’s Around Azimuth One Spatial Stream Target STA sees 13% of STA’s see greater than 10 dB drop in power 23% of STA’s see greater than 10 dB drop in power +3 dB Point +6 dB Point 2 Tx Antennas 4 Tx Antennas Caused by Sidelobes Mainlobe Jump dB Jump dB -10 dB Point 0 dB Point -10 dB Point 0 dB Point Mark Webster, Conexant Systems

NLOS Scenario Described All STA’s are NLOS March 2005 NLOS Scenario Described All STA’s are NLOS Antenna Pattern Beamform-Mode LOS Target 11n Client Radio Experiences Upward Power Step Multipath Reflectors 11n AP 4 Element Linear Array Antenna Pattern Omni-Mode Multipath Reflectors LOS Legacy 11n Client Radio Experiences Power Step Mark Webster, Conexant Systems

March 2005 Flat Rayleigh Chan A: Total Tx Power Held Constant Individual Element Power Allowed to Vary 2 Tx Antennas 4 Tx Antennas 7% of STA’s see greater than 10 dB drop in power Zoomed Zoomed Mark Webster, Conexant Systems

March 2005 Conclusion This submission has illustrated that more than a 10 dB power jump can occur in switch-to-beamform packets in some cases More work will be required to fully scope the impact on legacy OFDM packet reception Unlike 802.11b, OFDM does not have a CRC check on the Signal Field (header) Legacy OFDM radios may not have been certified for this behavior Mark Webster, Conexant Systems

March 2005 References IEEE 802.11/04-0889-04-000n, “TGnSync Proposal Technical Specification,” Syed Aon Mujtaba, March 4, 2005 IEEE 802.11/05-00150-02-000n, “WWiSE Complete Proposal Presentation,” S. Coffey et al., March 14, 2005 Mark Webster, Conexant Systems