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Simon Hyun, Brett Douglas, Eldad Perahia, Dave Petsko Cisco Systems, Inc.

Direct Path to Multipath Ratio and RMS Delay Spread Measurements in an Office and a Lab Environment. Simon Hyun, Brett Douglas, Eldad Perahia, Dave Petsko Cisco Systems, Inc. Background Information.

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Simon Hyun, Brett Douglas, Eldad Perahia, Dave Petsko Cisco Systems, Inc.

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  1. Direct Path to Multipath Ratio and RMS Delay Spread Measurements in an Office and a Lab Environment Simon Hyun, Brett Douglas, Eldad Perahia, Dave Petsko Cisco Systems, Inc. Perahia et. al., Cisco Systems, Inc.

  2. Background Information • K-factors are defined in the 802.11N Channel Models. The models for K-factors can be compared to measured data by calculating a Direct Path to Multipath Ratio (DPMPR) – The ratio of energy in the direct path (first tap) to the sum of the energy from all Multipath samples (all other taps). • In 802.11N, the models have the following (DPMPR). • Model B -> 9.16 dB • Model C -> 1.09 dB • Model D -> -6.57 dB Perahia et. al., Cisco Systems, Inc.

  3. Direct Path to Multipath Ratio Calculation Perahia et. al., Cisco Systems, Inc.

  4. RMS Delay Spread • The 802.11N Channel Models have increasing RMS delay spread • Model B: 15nsec • Model C: 30nsec • Model D: 50nsec Perahia et. al., Cisco Systems, Inc.

  5. Office Data Acquisition 2ft 2ft Aisle way RX (Orientation: | ) Dipole antennas Aisle way Pillar Path Obstruction (5-employee cube) Aisle way Path Obstruction (5-employee cube) 25ft Perahia et. al., Cisco Systems, Inc.

  6. Lab Data Acquisition Obstruction Benchtop 2ft RX (Orientation: | ) Dipole antennas 2ft Path Obstruction (test bench / equipment) Path Obstruction (test bench / equipment) 25ft Perahia et. al., Cisco Systems, Inc.

  7. DPMPR Distribution in an Office: LOS • Min: -10.0 dB • Mean: -1.5 dB • Max: 5.7 dB Perahia et. al., Cisco Systems, Inc.

  8. RMS Delay Spread Distribution in an Office:LOS • Min: 19.6 nsec • Mean: 33.7 nsec • Max: 46.9 nsec Perahia et. al., Cisco Systems, Inc.

  9. DPMPR Distribution in a Lab: LOS • Min: -7.7 dB • Mean: .6 dB • Max: 5.4 dB Perahia et. al., Cisco Systems, Inc.

  10. RMS Delay Spread Distribution in a Lab:LOS • Min: 11.8 nsec • Mean: 18.5 nsec • Max: 24.2 nsec Perahia et. al., Cisco Systems, Inc.

  11. DPMPR Distribution in an Office: NLOS • Min: -13.3 dB • Mean: -5.1 dB • Max: 3.3 dB Perahia et. al., Cisco Systems, Inc.

  12. RMS Delay Spread Distribution in an Office:NLOS • Min: 28.7 nsec • Mean: 37.5 nsec • Max: 48.2 nsec Perahia et. al., Cisco Systems, Inc.

  13. DPMPR Distribution in a Lab: NLOS • Min: -12.7 dB • Mean: -6.9 dB • Max: 1.6 dB Perahia et. al., Cisco Systems, Inc.

  14. RMS Delay Spread Distribution in a Lab:NLOS • Min: 17.3 nsec • Mean: 23.2 nsec • Max: 31.8 nsec Perahia et. al., Cisco Systems, Inc.

  15. Conclusions • The measurements reflect propagation conditions in a small office. This corresponds to 802.11n Channel Model C with a DPMPR of 1.09 dB and RMS delay spread of 30nsec. • LOS measurements results: • Mean DPMPR’s: -1.5 and -0.6 dB; close agreement with Model C. • Mean RMS delay spread measurements: 33.7 and 18.5 nsec; similar to model C. • NLOS measurements results: • Mean DPMPR’s: -5.1 and -6.9 dB; very different than Model C. • Mean RMS delay spread measurements: 37.5 and 23.2 nsec; similar to model C. • We could use two Model C’s, Model CL with a K-factor of 2 or 3 dB for LOS channels. Model CN with a K-factor of (–inf) dB for NLOS channels. • The NLOS mean DPMPR measurements match very closely to Model D. An alternative which results in fewer channel models would be to use Model C for LOS small office conditions and Model D for small office NLOS conditions. Though the measured RMS delay spread for NLOS conditions is higher than LOS conditions, it is still smaller than that for Model D. This would need to be resolved. Perahia et. al., Cisco Systems, Inc.

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