Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [IMST time-angular characteristics analysis] Date Submitted: [March 2006] Source: [Ali Sadri, Alexander Maltsev, Alexei Davydov] Company: [Intel Corporation] Address: [Intel Corporation, 13290 Evening Creek Drive ,San Diego , CA 92128-3419 ,USA] Abstract: [IMST time-angular characteristics analysis] Purpose: [To provide results for angular characteristics of the IMST data] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Ali Sadri (Intel Corporation)

2. Review of Previous Results on IMST Data Analysis • In J. Kunish et al. “MEDIAN 60GHz Wideband Indoor Radio Channel Measurements and Model” [1], VTC 1999, Vol. 4, pp. 2393-2397, Sept. 1999 and A. Sadri et al. “IMST data analysis” IEEE 802.15-06-0022-01-003c” [2], basic analysis of the IMST measured data has been performed. • Omni- and directional antennas were considered • Simple time-domain parameters of the channel were calculated • Exponential parameter of multipath region • K-factor for the strongest path • Distribution of rays amplitudes in multipath region • Based on the results single cluster Saleh-Valenzuela model has been proposed in [1] with rate of multipath ray arrival = 1ns-1 Ali Sadri (Intel Corporation)

3. Goals of this Presentation • Extend analysis of IMST data to characterize time-angular parameters of millimeter wave channel • Evaluate cross polarization discrimination (XPD) for linear polarization • Determine diffraction loss model • Propose enhanced channel model based on measured data Ali Sadri (Intel Corporation)

4. Measurement scenarios plan LOS NLOS Edge Ali Sadri (Intel Corporation)

5. Measurements Scenarios • Library environment with tables, chairs and metal bookshelves with books • 3 main types of measurement scenarios • LOS: unobstructed line of sight conditions • Edge: partially obstructed line of sight by the edge of a metal bookshelf • NLOS: non line of sight obstructed by a densely filled bookshelf • 3 types of RX antennas (horn, wideband dipole array antenna, biconical) • Fixed TX lens antenna position at the suspended ceiling, RX measurements range ~2-5m • Time resolution is 1/960MHz ≈ 1ns Ali Sadri (Intel Corporation)

6. Antennas Used in Experiment Transmitting antenna Receiving antennas Omni directional in horizontal dielectric lens antenna; 8dBi gain @ 76º from vertical Omni directional in horizontal biconical antenna with 9 dBi gain Printed array of 8x8 pentagonal dipoles with 22 dBi gain 20 dBi standard gain horn antenna Ali Sadri (Intel Corporation)

7. Data Processing Methodology • Original measurements were performed in frequency domain using vector network analyzer • The measured frequency response was windowed by Blackman-Harris window and converted to time domain using IFFT • Originally the Channel frequency response was measured over several RX positions. For each position virtual uniform linear array was synthesized by shifting RX antenna along horizontal straight line • For determination of DoA characteristics,Fourier transform with spatial windowing procedures were used Ali Sadri (Intel Corporation)

8. Cross Polarization Discrimination (XPD) Analysis • Polarization may be considered as a way of multipath component rejection • Reflection and diffraction may change polarization orientation and increase cross-polarized component • For IMST experiment only linear vertical polarization was used at transmitter Ali Sadri (Intel Corporation)

9. Some XPD Observations from the Measurements • Significant attenuation of LOS component (~20 dB) for cross polarized antenna • Almost the same attenuation profile for all rays in multipath region (~10 dB) Cross-polarized Rx antenna Co-polarized Rx antenna Ali Sadri (Intel Corporation)

10. Diffraction Loss • Due to diffraction radio waves may propagate in region of shadow • The signal attenuation in shadow region is angle dependent • Diffraction loss was measured for ‘edge’ scenario, when metal bookshelf wall plays a role of “knife” edge • The difference between two signal levels for free space and for shadow region was taken as the diffraction loss Ali Sadri (Intel Corporation)

11. Diffraction Loss Model Ali Sadri (Intel Corporation)

12. Observation of Diffraction Loss LOS component change from experiment Theoretical LOS component change ~6 dB Diffraction loss shows linear decay in dB scale for shadow region; Slope of the curve is distance dependent Ali Sadri (Intel Corporation)

13. DoA Parameters for mmWave Channel • DoA parameters of the channel are important for characterization of multi-antenna systems and systems with directional antennas, since these models may take into account the effects of specific Rx antenna radiation pattern G(φ,θ) • Determination of DoA/ToA parameters is required for accurate description of reflected waves/multipath components in channel model at 60 GHz Ali Sadri (Intel Corporation)

14. Direction of Arrival Diagrams Ali Sadri (Intel Corporation)

15. Direction of Arrival vs. Time of Arrival (LOS scenario, horn/biconical antennas) Magnitude of response is different due to spread angular distribution of the reflected rays Slope is almost the same for all angles in the second part of PDP Pulses in the first part of PDP mostly come from single scattered (reflected) rays Ali Sadri (Intel Corporation)

16. Direction of Arrival vs. Time of Arrival (LOS scenario, horn antenna) Multipath components are largely attenuated by directional antenna Ali Sadri (Intel Corporation)

17. Direction of Arrival vs. Time of Arrival(LOS scenario, biconical antenna) K ~ 7 dB K ~ 15 dB K < -50 dB Several strongly localized rays in time/angular dimensions for delays < 50 ns and angles < +-700 Strong multipath components may have Rician distribution or may be almost deterministic with random phases Ali Sadri (Intel Corporation)

18. Direction of arrival vs. Time of arrival (NLOS scenario, horn antenna) Broadening of direction of arrival angles due to scattering during the propagation of waves through the books Ali Sadri (Intel Corporation)

19. DoA for Different Delays Ali Sadri (Intel Corporation)

20. Main Conclusions • The most useful and valuable are the measurements performed with the help of omni-directional (bi-conical antenna) that allowed, through the synthesis of large antenna array, to resolve the arriving rays and to estimate their parameters (DoA, ToA and power) • Measurements and signals processing performed in such a way showed that the received signal has specific “speckle-structure” which manifests itself as the number of strong single reflected rays in the received signal (“bright speckles” not forming the clusters in time-angle plane) Ali Sadri (Intel Corporation)

21. Summary • The channel response function for indoor environment in mmWave band is the result of three components: the LOS ray, the number of single reflected rays, and the small background diffuse multipath component (-20-30 dB). • Free space propagation and first order reflections are the dominant propagation mechanisms. The detailed analysis in time-angle domain shows that these components may be of almost the same order (see slides 14, 16, 18). • Strong multipath components are results of strong reflectors, such as walls, floor, metallic furniture, and other plane surfaces. Single reflected waves are strongly angle/time localized, have magnitude comparable to the magnitude of LOS component, and have Rician distribution with large K-factor (~7 dB) Note: The similar values of magnitudes of multipath rays and LOS component in the first part of power delay profile may be explained by the difference in heights of the transmit and the receive antennas and dependence of the antenna patternon elevation angle Ali Sadri (Intel Corporation)

22. Summary (continued) • Diffuse multipath component is caused by multiple scattering. Multiple reflected rays are largely attenuated and arrived isotropically from all azimuth angles. The power delay profile of these rays follows the simple exponential law. These rays are substantially Rayleigh distributed • Directional antennas provide good angular resolution of multipath components and significantly attenuate most of multipath rays. At the same time small misalignment of TX/RX antenna pointing may result to significant attenuation of the LOS ray by ~10dB [1] Ali Sadri (Intel Corporation)

23. Suggestions for modeling (to be discussed) • The “speckle” channel model in time-angle domain may be proposed as a basic channel model for indoor mmWave multipath propagation. Models of such a type are known in optics, and it has been discovered that mmWave signals in indoor environment behave more like optic wave rather than radio waves of 2.4-5 GHz bands. • The speckle channel model may be described as two dimensional tapped delay/angle model with specific power profile P(φm,τn) consisting of three components: the LOS ray, the number of single reflected rays, and the small background diffuse multipath component. • Open issue • Need to agree on the statistical characteristics of single reflected rays in typical indoor environment and include them into the speckle channel model Ali Sadri (Intel Corporation)

24. References • J. Kunish et al. “MEDIAN 60GHz Wideband Indoor Radio Channel Measurements and Model”, VTC 1999, Vol. 4, pp. 2393-2397, Sept. 1999 • A. Sadri et al. “IMST data analysis” IEEE 802.15-06-0022-01-003c • C. Loyez et al. “Indoor 60 GHz radio channel sounding and related T/R module considerations for high data rate communications”. Electronics Letters, Vol. 37, No. 10, May 2001, pp. 654-655 Ali Sadri (Intel Corporation)

25. Appendix Ali Sadri (Intel Corporation)

26. Ali Sadri (Intel Corporation)

27. Typical time-domain impulse response structure First part of PDP is composed from LOS component and first-order reflections. Pulses may have Rician distribution and are usually largely attenuated when directional antenna is used. LOS component Second part of PDP is composed from diffuse rays arriving from all directions. The power delay profile of this part can be accurately described by exponential function. The fading of multipath components can be characterized by Raleigh distribution. Ali Sadri (Intel Corporation)

28. Statistics of multipath amplitudes Ali Sadri (Intel Corporation)