1. Doppler Measurements for Mobile Devices
April 2007
doc.: IEEE /0570r0
September 2009
Doppler Measurements for Mobile Devices
Date:
Authors:
Eldad Perahia, Intel Corporation
Eldad Perahia, Intel Corporation

2. April 2007
doc.: IEEE /0570r0
September 2009
Introduction
As described in [1], the n Doppler model applied a Doppler spectrum to every tap in the impulse response
Numerous measurements have been made [1-5] demonstrating that the channel coherence time of stationary devices do not match that of the n Doppler model
New measurements have been made on a slowly moving device to see how the channel coherence time compares to the n Doppler model
Eldad Perahia, Intel Corporation
Eldad Perahia, Intel Corporation

3. New Measurements with Slowly Moving Device
September 2009
New Measurements with Slowly Moving Device
Measurements were captured the same office environment as in [1]
Laptop was placed on a cart and pushed at slow walking speed along the corridor completing an entire circle around the floor
Laptop was the source device
Stationary clients were destination devices, which captured CSI from LTFs (3 Tx antennas, 3 Rx antennas, 3 streams)
TxBF capacity computed from measurements as described in [1]
Channel coherence time computed from measurements as described in [2]
Eldad Perahia, Intel Corporation

4. Floor Plan Circled numbers indicate destination device locations
September 2009
Floor Plan 1 4 3
Circled numbers indicate destination device locations
Eldad Perahia, Intel Corporation

5. Example of Measured Data
September 2009
Example of Measured Data
This is an example of the time progression of a single subcarrier of a single Tx and Rx antenna combination
i.e. H[1,2] for subcarrier 1
Much more rapid variation and deeper nulls than for stationary devices in [2]
Eldad Perahia, Intel Corporation

6. Example Coherence Time
September 2009
Example Coherence Time
Eldad Perahia, Intel Corporation

7. September 2009
Example Capacity
Eldad Perahia, Intel Corporation

8. Summary of Measurements
September 2009
Summary of Measurements
Comparable results at each destination
Substantial degradation to TxBF gain after 20ms and 50ms
Very short coherence time as compared to stationary devices in [2]
Degradation similar to that seen with n channel model with Doppler
Eldad Perahia, Intel Corporation

9. September 2009
Conclusion
Measured coherence time and degradation to TxBF gain are comparable to that of the original n Doppler model
802.11n Doppler model appears to be reasonable for slowly moving devices
TGac simulation scenarios contain handheld devices, which very reasonably would be mobile, e.g. someone walking around with their phone
TGac Doppler model should have a velocity component for both mobile and stationary devices
Original n Doppler model should be applied to the handheld devices in the TGac simulation scenarios
Eldad Perahia, Intel Corporation

10. September 2009
References
[1] Perahia, E., Kenney., T., Stacey, R., et. al., Investigation into the n Doppler Model, IEEE /538r0, May 11, 2009
[2] Perahia, E., Channel Coherence Time, IEEE /784r0, July 2009
[3] Honma, N., Nishimori, K., Kudo, R., Takatori, Y., Effect of SDMA in ac, IEEE /303r1, March 12, 2009
[4] Nishimori, K., Takatori, Y., Yamada, W., Measured Doppler Frequency in Indoor Office Environment, IEEE /537r0, May 2009
[5] Yamada, W., Nishimori, K., Takatori, Y., Coherence Time Measurement in NTT Lab, IEEE /828r0, July 2009
Eldad Perahia, Intel Corporation

11. September 2009
strawpoll
1) include mobility and change doppler spectrum to Jakes for mobile device - 8
2) include mobility and use current 11n for mobile device - 20
3) leave all devices in EM stationary - 1
Eldad Perahia, Intel Corporation