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Doppler Measurements for Mobile Devices

Doppler Measurements for Mobile Devices. Date: 2009-09-21. Authors:. Introduction. As described in [1], the 802.11n Doppler model applied a Doppler spectrum to every tap in the impulse response

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Doppler Measurements for Mobile Devices

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  1. Doppler Measurements for Mobile Devices Date: 2009-09-21 Authors: Eldad Perahia, Intel Corporation

  2. Introduction • As described in [1], the 802.11n 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 802.11n Doppler model • New measurements have been made on a slowly moving device to see how the channel coherence time compares to the 802.11n Doppler model Eldad Perahia, Intel Corporation

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

  5. 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] Example of Measured Data Eldad Perahia, Intel Corporation

  6. Example Coherence Time Eldad Perahia, Intel Corporation

  7. Example Capacity Eldad Perahia, Intel Corporation

  8. 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 802.11n channel model with Doppler Summary of Measurements Eldad Perahia, Intel Corporation

  9. Conclusion • Measured coherence time and degradation to TxBF gain are comparable to that of the original 802.11n 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 802.11n Doppler model should be applied to the handheld devices in the TGac simulation scenarios Eldad Perahia, Intel Corporation

  10. References • [1] Perahia, E., Kenney., T., Stacey, R., et. al., Investigation into the 802.11n Doppler Model, IEEE 802.11-09/538r0, May 11, 2009 • [2] Perahia, E., Channel Coherence Time, IEEE 802.11-09/784r0, July 2009 • [3] Honma, N., Nishimori, K., Kudo, R., Takatori, Y., Effect of SDMA in 802.11ac, IEEE 802.11-09/303r1, March 12, 2009 • [4] Nishimori, K., Takatori, Y., Yamada, W., Measured Doppler Frequency in Indoor Office Environment, IEEE 802.11-09/537r0, May 2009 • [5] Yamada, W., Nishimori, K., Takatori, Y., Coherence Time Measurement in NTT Lab, IEEE 802.11-09/828r0, July 2009 Eldad Perahia, Intel Corporation

  11. 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

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