Rationale

1. IntelSISO/MIMO WLAN Channel Propagation ResultsVal Rhodes (valentine.j.rhodes@intel.com)Cliff Prettie(clifford.w.prettie@intel.com) Val Rhodes, Cliff Prettie, Intel Corp.

2. Rationale • For high throughput, accurate channel statistics are needed • Expand channel models used by 802.11 and HIPERLAN/2 • Increase statistical significance of assumptions driving the Channel Modeling Interest Group effort Val Rhodes, Cliff Prettie, Intel Corp.

3. Agenda • SISO Results – Val Rhodes • 5 GHz to 6 GHz static channel characterization • Residential and office environments • Path loss and delay spread curves • Channel Model • MIMO Results – Cliff Prettie • Angular spectra Val Rhodes, Cliff Prettie, Intel Corp.

4. SISO Measurement Strategy • Vector Network Analyzer was used to provide the stimulus and measure the response • 1601 samples across 5 GHz to 6 GHz (625 kHz resolution) • Quarter-wave monopole antennas with center frequencies of 5.250 GHz (U-NII 1) Val Rhodes, Cliff Prettie, Intel Corp.

5. Path Loss • Received power vs. distance • A0 is the 1m delta between free space and measured result (often expressed as wall attenuation factor (WAF) in literature) • Free space: n=2, A0=0 Val Rhodes, Cliff Prettie, Intel Corp.

6. Indoor Received Power Residential Measurements Office Measurements Observations: n = 3.14 for all residential measurements but n = 1.66 when wall attenuation removed 4.5 dB attenuation for interior wall penetration, 9 dB attenuation for exterior wall penetration 6 dB of loss due to cross-polarization of antennas (mostly LOS channels) Office desk mount vs. ceiling mount path loss was equivalent Val Rhodes, Cliff Prettie, Intel Corp.

7. Delay Spread Results Legend: 1st Field: Residential/Office 2nd Field: Indoor/Outdoor 3rd Field: Number of walls Observations: Residential indoor LOS channels exhibited shortest rms delay spread of 12 ns Office indoor NLOS channels exhibited longest rms delay spread of 52 ns Val Rhodes, Cliff Prettie, Intel Corp.

8. 802.11 Delay Spread Model The channel is modeled by a Finite Impulse Response (FIR) filter where the taps are independent complex Gaussian random variables with zero mean and average power sk2, for k = 0, 1, …, kmax trms is the rms delay spread Ts is the sampling period Val Rhodes, Cliff Prettie, Intel Corp.

9. 802.11 Delay Spread Comparison Residential Indoor LOS Office Indoor NLOS Measured delay spread results for all environments showed close agreement with 802.11 model. Individual taps followed a Gaussian distribution as expected from Central Limit Theorem. Val Rhodes, Cliff Prettie, Intel Corp.

10. SISO Channel Model Parameters NW: Number of walls penetrated Val Rhodes, Cliff Prettie, Intel Corp.

11. SISO Result Summary • Key result of this work was the classification of channels into residential, office, indoor-to-indoor, indoor-to-outdoor, and wall penetration models. • Model parameters offer path loss and delay spread expectations for a large percentage of typical WLAN deployments. • These propagation results have been used to define model parameters for the Channel Modeling Interest Group Val Rhodes, Cliff Prettie, Intel Corp.

12. MIMO Modeling Val Rhodes, Cliff Prettie, Intel Corp.

13. Importance of Angular Spectra for MIMO • Angular spectra tie physical propagation models to MIMO system performance • Specify from where energy is arriving for determining received power into antenna patterns • Specify arrayed antenna correlation properties • Closely related to ray arrivals and scattering models • Scattering clusters can be observed if they are present. Val Rhodes, Cliff Prettie, Intel Corp.

14. Channel Modeling Interest Group • Developing a model based on clusters of scatterers. • Makes assumptions regarding number, size, and time-of-arrival characteristics both in aggregate and with 10 ns range resolution. • MIMO data is being used to focus the current model efforts, eg. • AP in a large room to BSS in conference room Val Rhodes, Cliff Prettie, Intel Corp.

15. Conference Room Measurements • AP is elevated in a large room with cubicle partitions • STA is desk level in a closed hard wall conference room. • Displayed are the time of arrival spectra, the angular spectra, and the angular spectra at a given time of arrival delay. Val Rhodes, Cliff Prettie, Intel Corp.

16. Angular Spectrum at Zero Delay • Arrival energy at zero delay is localized at AP. • Arrival energy at zero is wide angle in conference room. • Implications for trying to correlate of delay and angle. Val Rhodes, Cliff Prettie, Intel Corp.

17. Further Angular Spectra Results • Spectra from horizontally oriented antennas show a strong collimation of signal energy between the floor and the ceiling. • Waveguide effect • Responsible for pathloss rate less than free space. Val Rhodes, Cliff Prettie, Intel Corp.

18. Scattering Clusters • Number of scattering clusters contributing to the signal energy can depend on the time delay investigated. • Generally more clusters enter into the scattering process as the time of arrival increases. Val Rhodes, Cliff Prettie, Intel Corp.

19. Other Results relevant to the model • Data on channel Doppler under various conditions is available. • Most is single tone results • Multi-tone time resolution does not characterize the fastest channels. • Data on signal depolarization is available. Val Rhodes, Cliff Prettie, Intel Corp.

20. Summary • Extensive experimental results have been obtained for SIMO/MIMO propagation phenomena in SOHO and SME environments. • These results are being integrated into the Channel Modeling Interest Group led by Erceg. Val Rhodes, Cliff Prettie, Intel Corp.

21. References • Chayat, Naftali, “Tentative Criteria for Comparison of Modulation Methods,” doc.: IEEE 802.11-97/96. Sept. 1997 • Chatay, Naftali, “Updated Submission Template for TGa – revision 2,” doc.: IEEE 802.11-98/156r2, March 1998 • Halford, Steve, Halford, Karen, Webster, Mark, “Evaluating the Performance of HRb Proposals in the Presence of Multipath,” doc.: IEEE 802.11-00/282r2, Sept. 2000 • Freeman, Roger L., Radio System Design for Telecommunications, John Wiley & Sons, 1997 Val Rhodes, Cliff Prettie, Intel Corp.