1. Timing Measurement Date: 2008-07-16 Authors: July2008 November 2007
doc.: IEEE /2752r1
July2008
Timing Measurement
Date:
Authors:
Ganesh Venkatesan, Intel Corporation
Peter Ecclesine, Cisco Systems

2. November 2007
doc.: IEEE /2752r1
July2008
Abstract
This submission summarizes the Timing Measurement feature in v in general and specifically addresses two LB133 comments on Timing Measurement (268, 1280).
Note: There are more LB133 comments on Timing Measurement that are not directly addressed by this submission and will be addressed later.
Ganesh Venkatesan, Intel Corporation
Peter Ecclesine, Cisco Systems

3. Timing Measurement motivations
November 2007
doc.: IEEE /2752r1
July2008
Timing Measurement motivations
Use the measurement data in a higher layer algorithm to:
Synchronize clocks between two STAs or synchronize systems to a common clock
Non-AP STA-based determination of location
Researching the motivations further demonstrated that accuracy requirements on the time measurement data are too tight (resulting in complex implementation(s)) in order to determine location. Hence the ‘non-AP STA-based location determination’ goal is now dropped.
Ganesh Venkatesan, Intel Corporation
Peter Ecclesine, Cisco Systems

4. Timing Measurement Support
July2008
Timing Measurement Support
Ganesh Venkatesan, Intel Corporation

5. Timing Measurement Frame
July2008
Timing Measurement Frame
Category
Action
Dialog Token
Follow Up Dialog Token
Timestamp Difference
(optional)
Timestamp
Timestamp Accuracy
Optional sub-elements
Octets 1
0 or 4
0 or 10
0 or 1
Variable
Ganesh Venkatesan, Intel Corporation

6. Frame Exchanges to Get the Required Data
July2008
Ganesh Venkatesan, Intel Corporation

7. Timestamps Time of Departure
July2008
Timestamps
Time of Departure
Time of Arrival (discussed in this submission)
Ganesh Venkatesan, Intel Corporation

8. Receive PLCP (example Clause 15 PHY)
July2008
Receive PLCP (example Clause 15 PHY)
Ganesh Venkatesan, Intel Corporation

9. What happens in the PLCP?
July2008
What happens in the PLCP?
If the MIB variable dot11MgmtOptionTimingMsmt exists and is set to TRUE, the PLCP shall do the following:
Save the value of the Timestamp counter corresponding to the time when the first PMD_DATA.Indication for the incoming frame was received from the PMD, ta,
Estimate timestamp offset between when the first PMD_DATA.Indication occurred and when the PCLP header will be fully received and determined to be valid, toffset,
Save the value of the Timestamp counter corresponding to the actual time when the PCLP header is received and determined to be valid, tactual
Determine timestamp error = tactual – (ta + toffset), and
Forward tactual, timestamp error values within RXVECTOR
Ganesh Venkatesan, Intel Corporation