1. Power Variations with WWiSE Cyclic Preamble Structures
January 2005
doc.: IEEE /1581r0
January 2005
Power Variations with WWiSE Cyclic Preamble Structures
Date:
Authors:
Notice: This document has been prepared to assist IEEE 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
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures < 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 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at
Dave Hedberg, Conexant Systems
Dave Hedberg, Conexant Systems

2. January 2005
doc.: IEEE /1581r0
Abstract
January 2005
This presentation shows simulation plots of the power variation statistics (as seen at the receiver antennas) between short training preamble segments, which are used by a receiver to set AGC levels, and long training preamble and payload data segments for the WWiSE cyclic shifted preamble structures. Cases examined include both Greenfield and Mixed-mode preamble modes for 20 MHz and 40 MHz multi-antenna transmission modes. In each case, statistics are shown with TGn B, D, and E NLOS channel models. In each case, the power variation for a single antenna (SISO) signal is compared with that of the multiple antenna WWiSE transmission that includes associated cyclic shifts in the preambles.
The analysis does not include specific AGC algorithm performance, but only basic signal power variation behavior arising from the different channel statistics.
The results show that the relatively long cyclic shifts employed in the WWiSE Greenfield multi-antenna preambles have well-behaved power variations (e.g. on the order of 0.5 dB rms and close to SISO for the 2-antenna modes). Variations are larger in 3 and 4 antenna modes, but not substantial compared with typical AGC error budget factors. For the legacy preamble portion of mixed-mode signals, the variations of legacy LTS and SF segments can be greater because of the shorter cyclic shifts employed. Laboratory testing has shown that legacy devices can reliably detect these mixed mode legacy signal fields.
Dave Hedberg, Conexant Systems
Dave Hedberg, Conexant Systems

3. Outline Introduction 2-Tx Ant 20 MHz Greenfield Modes
January 2005
Outline
Introduction
2-Tx Ant 20 MHz Greenfield Modes
3-Tx and 4-Tx Ant 20 MHz Greenfield Modes
2-Tx Ant 40 MHz Greenfield Modes
Mixed-mode Preamble Modes
Conclusions
Dave Hedberg, Conexant Systems

4. January 2005
Introduction
We examine power variations of the STS power (used for AGC) relative
to LTS power and to average power in 100 random payload data symbols
SISO vs. MIMO (multi-antenna transmission) are compared for each mode
Power variation CDFs plotted for 2000 channel instances
TGn channel models B, D, and E, NLOS
Dave Hedberg, Conexant Systems

5. STS to LTS Power Variation - 2-Tx GF20
January 2005
STS to LTS Power Variation - 2-Tx GF20
Ch B, NLOS
Ch E, NLOS
Ch D, NLOS
Dave Hedberg, Conexant Systems

6. STS to Data Power Variation - 2-Tx GF20
January 2005
STS to Data Power Variation - 2-Tx GF20
Ch B, NLOS
Ch E, NLOS
Data power in 100 random SISO
or 2-stream MIMO symbols
Ch D, NLOS
Dave Hedberg, Conexant Systems

7. January 2005
3-Tx and 4-Tx GF20 Modes
Dave Hedberg, Conexant Systems

8. STS to LTS, Data Power Variations - 3-Tx GF20
January 2005
STS to LTS, Data Power Variations - 3-Tx GF20
Ch B, NLOS
LTS
Data
Ch D, NLOS
Dave Hedberg, Conexant Systems

9. STS to LTS, Data Power Variations - 4-Tx GF20
January 2005
STS to LTS, Data Power Variations - 4-Tx GF20
Ch B, NLOS
LTS
Data
Ch D, NLOS
Dave Hedberg, Conexant Systems

10. STS to LTS Power Variation - 2-Tx GF40
January 2005
STS to LTS Power Variation - 2-Tx GF40
Ch B, NLOS
Ch E, NLOS
Ch D, NLOS
Dave Hedberg, Conexant Systems

11. STS to Data Power Variation - 2-Tx GF40
January 2005
STS to Data Power Variation - 2-Tx GF40
Ch B, NLOS
Ch E, NLOS
Ch D, NLOS
Dave Hedberg, Conexant Systems

12. Mixed Mode 20 MHz Structure
January 2005
Mixed Mode 20 MHz Structure
Legacy portion of the preamble (20 us) is utilized for legacy signal field
decoding only
STS portion of preamble sets the AGC, and is the same in both mixed-mode
and Greenfield mode formats
Dave Hedberg, Conexant Systems

13. STS to L-LTS/SF Power Variation - 2-Tx MM20
January 2005
STS to L-LTS/SF Power Variation - 2-Tx MM20
Ch B, NLOS
Ch E, NLOS
Ch D, NLOS
Dave Hedberg, Conexant Systems

14. January 2005
Summary
The relatively long cyclic shifts employed in the WWiSE Greenfield preambles result in well behaved STS power statistics
Variations for 2-Tx antenna cases (with 400 ns shift in the STS) track closely the variations seen in legacy SISO modes
The power variation statistics for mixed mode receptions of 11n signals are the same as for Greenfield modes -- since the STS portion of the two preamble types is the same
The legacy portion of mixed mode preambles employ shorter cyclic shifts for the legacy LTS/SF portion – and consequently
exhibit larger variations
This part of the preamble is used only for legacy signal field detection
Extensive testing of legacy device detection capability with this format is documented in IEEE /xxxxr0
Dave Hedberg, Conexant Systems

15. January 2005
References
IEEE / n, “WWiSE Proposal: High throughput extension to the Standard,” C. Hansen, B. Edwards et al.
IEEE / n, “WWiSE IEEE n Proposal,” S. Coffey et al., Nov. 16, 2004
IEEE /05-xxxx n, “Short Training Sequence Compatibility with Legacy Devices”, Tushar Moorti, et. al.
Dave Hedberg, Conexant Systems