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Real-World MIMO Channel Measurements with Time-Varying Effects

Gain insights into real-world MIMO measurements, analyze time variability, and quantify capacity enhancements. Discover the impact of time variability effects on MIMO channels using a comprehensive set-up and measurement locations. Understand the significance of fluorescent effects on channel modulation and capacity. Learn about ongoing measurements and future study topics.

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Real-World MIMO Channel Measurements with Time-Varying Effects

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  1. Time Variable HT MIMO Channel MeasurementsNir Tal Metalink(nirt@metalink.co.il) Metalink

  2. Purpose • Provide a snapshot of real-environment MIMO measurements with time variability • Derive HT capacity figures and quantify improvement • Quantify time variability and underlying effects Metalink

  3. Measurement Information • Several hundred of measurements taken at various locations and scenartios within the company. • Measurements were taken at the lower UNII band (~5.2 GHz) • Receive antennas fixed at a height of ~2m (e.g. AP position) • TX setup moves between measurement positions Metalink

  4. Measurement Set Up • Philosophy: • Full simultaneous MIMO measurements • Relatively slow sampling rate (46MHz)– long sampling period (100msec) • Store all samples and post-process offline • Use wideband transmission signals (>20MHz) • Omni reception and transmission antennas Metalink

  5. Set-Up Block Diagram Metalink

  6. Signal Transmission Setup Metalink

  7. Transmission Antennas Metalink

  8. Reception Antennas Metalink

  9. Spectrum Analyzer/ Down Converter Setup Metalink

  10. Sampling Setup Metalink

  11. Indoor Measurement Locations Metalink

  12. Result Snapshot Metalink

  13. Intra-Room (NLOS), Typical Channel (M11-11) Metalink

  14. Impulse Response (M11-11) Metalink

  15. Time Frequency Response (M11-11) Metalink

  16. Frequency Response Time Variability (M11-11) Metalink

  17. RMS Delay Spread (M11-15) Metalink

  18. MIMO Capacity (theoretical) • The theoretical MIMO channel capacity is given by [1]: • Where: C – Capacity [bps/Hz], W- Bandwidth [Hz], P- Power [W], - Noise Variance [W], H- Channel Matrix, - TX Antenna Number Metalink

  19. Real-Environment Calculated Capacity (M11-14) (MIMO Capacity)/2 Metalink

  20. Statistical Findings Metalink

  21. MIMO Capacity Enhancement- NLOS, Dist= 25.6m (M11-XX) Metalink

  22. MIMO Capacity Enhancement- LOS, Dist=25m (M11-XX) Metalink

  23. Periodic Modulation • In nearly all tests, a strong AM-like periodicity is clearly seen. • The period of this modulation was tested to be exactly 100Hz Metalink

  24. Fluorescent Effect Setup Metalink

  25. Fluorescent Effect Setup (cont.) Metalink

  26. Fluorescent Effect Setup (cont.) Metalink

  27. Spectrum at the Various Scenarios Metalink

  28. Time Domain Power Plot of Fluorescent Effect Metalink

  29. The Fluorescent Effect • Fluorescent lights become conductive twice every AC power cycle. • During that period, the electromagnetic environment (reflections) are changed. • The channels in such environment exhibit strong AM modulation in all parameters (frequency response, RMS delay spread, capacity, etc.) • We therefore suggest to incorporate this effect into the MIMO channel models as it is one of the major causes of channel time variability Metalink

  30. Conclusions • In typical enterprise scenario 2 antenna MIMO enhances the median capacity by 1.5-2x (NLOS and LOS) • Channels exhibits “slow” variability changes over 100ms (f<10Hz) • In the vicinity of fluorescence lights the channel is modulated by a strong 100/120Hz AM modulation (up to 5dB) Metalink

  31. Summary • A snap-shot of channel measurements in office environment has been presented • Measurements are ongoing and their study shall include topics such as: antenna polarization, channel reciprocity and LOS behavior . • These results are being integrated into the Channel Modeling Sub-Committee led by Erceg. Metalink

  32. References • [1] – Branka Vucetic, “Space-Time Coding”, Wiley& Sons, 2003 Metalink

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