#### Transcript doc.: IEEE 802.15-04-0325-00-004a

July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Project: IEEE 802.15 Study Group for Wireless Personal Area Networks (WPANs) Submission Title: [An Ultra-Wideband Channel Model and Coverage for Farm/Open-Area Applications] Date Submitted: [12 July, 2004] Source: [Shahriar Emami, Celestino A. Corral, Gregg Rasor]: Company1 [Freescale Semiconductor], Address [8000 W. Sunrise Blvd., Plantation, FL 33322], Voice:[(954) 723-3854], FAX: [(954) 723-3883], Re: [Channel Model Submission] Abstract: [An ultra-wideband channel model for open area/farm applications is submitted. The channel model is based on ray tracing that captures signal descriptors including frequencies. The rationale behind the channel model is developed and presented in support of the presentation.] Purpose: [An understanding of the open area outdoor environment for ultra-wideband (UWB) signal coverage is needed for 802.15 TG4a. This channel model should assist in predicting UWB range and proper signal design for open area applications.] 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. Contribution Slide 1 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a An Ultra-Wideband Channel Model and Coverage for Farm/Open-Area Applications Shahriar Emami, Celestino A. Corral and Gregg Rasor Freescale Semiconductor Contribution Slide 2 Shahriar Emami, Freescale Semiconductor July 12, 2004 • • • • Preliminaries - Prior Art - Simulated Environment - Approach - Simulation Setup Proposed Channel Models - 2 Ray and 3 Ray Models - Amplitude Statistics - Model Parameters - Ray Locations Simulation Results - Terrain Variations - Ground Conditions - Polarization Diversity - Additional Scatterers Summary and Conclusions Contribution doc.: IEEE 802.15-04-0325-00-004a Outline Slide 3 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Prior Art • Prior Efforts: – Two-ray UWB path loss model: • S. Sato and T. Kobayashi, “Path-loss exponents of ultra wideband signals in line-of-sight environments,” IEEE802.15-04-0111-00-004a, March 2004. – Hybrid deterministic/statistical narrowband approach for roadways: • A. Domazetovic, L.J. Greenstein, N.B. Mandayam, I. Seskar, “A new modeling approach for wireless channels with predictable path geometries,” VTC 2002-Fall Proceedings, Volume 1, pp. 24-28, Sept. 2002.. – Deterministic UWB channel model based on ray tracing approach: • B. Uguen, E. Plouhinec, Y. Lostanlen, and G. Chassay, “A deterministic ultra wideband channel modeling,” 2002 IEEE Conf. Ultra Wideband Syst. Tech. We use approach considered here Contribution Slide 4 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulated Environment • Farm areas feature isolated clusters of scatterers • Scatterers include wooden house, silo and up to three tractors • Ground is not flat • Impact of dry/wet conditions Contribution Slide 5 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Approach • Use narrowband deterministic 3-D ray tracing simulator - Employs – Geometric Optics (GO) – Uniform Theory of Diffraction (UTD) – Generates • Received signal strength • Ray statistics (path length/delay) • Signal descriptors include frequency, polarization, etc. • UWB channel sounding is achieved by superposition of NB channel sounding - FCC emissions mask scaled channel sounding (constrained channel sounding) Contribution Slide 6 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Approach- Cnt’d • Constrained Channel Sounding Energy of band concentrated in high band frequency -12.8 -11.4 -11.2 -13.8 -14.8 3.10 Contribution 4.24 5.34 Slide 7 6.72 8.64 10.6 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulation Set-Up 3-D omni antenna pattern used Omni pattern assumed at all frequencies omni antenna above house omni antenna near ground Farm area consists of two-story wood home and metal grain silo. Ground is not flat; has slight variations in height. Contribution • Receiver grid placed around home, 200m X 200m • Receiver spacing was 4m X 4m • Receiver height was at 1.3m • For omni antenna above house, antenna was at 12.5m height • For omni antenna near ground, antenna was at 1.5m height. Slide 8 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Coverage Results Wet soil • Contribution Slide 9 Highest level -64.4 dBm Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Towards a Channel Model • These are only a small number of rays in each CIR • Majority of energy is contained in 2 or 3 rays . 2 Ray Model h(t ) a1 exp( j1 ) (t t1 ) a2 exp( j 2 ) (t t 2 ) . 3 Ray Model h(t ) a exp( j ) (t t ) a exp( j ) (t t ) a exp( j ) (t t ) 1 1 1 2 2 2 3 3 3 Contribution Slide 10 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Block Diagram Representation • 2 Ray Model t1 a1 t2 a2 t1 • 3 Ray Model a1 t2 a2 t3 a3 Contribution Slide 11 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulation Results—Ray Statistics • Statistics of the two rays are found to be Rayleigh distributed. Histogram of the Largest Ray 150 100 50 0 0 1 2 3 4 5 6 7 8 -6 x 10 Histogram of the Second Largest Ray 200 150 100 50 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -6 x 10 Contribution Slide 12 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Comparison • Figure of Merit: Percentage of locations that a model captures 90% or more of their PDP power. • 2 ray model and 3 ray models work well for about 76% and 91% of locations. 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 65 70 75 80 85 90 95 100 3 ray model is superior to 2 ray model. Contribution Slide 13 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Channel Model Parameters CM1 (5 m) • • • CM2 (15 m) CM3 (75 m) Ray 1 (m, s) (1.8e-5, 1.5e-10) (8e-6, 1.36e-11) (4.8e-6,1.49e-12) Ray 2 (m, s) (1.6e-6, 2.35e-14) (2.2e-6, 1.3e-12) (6.7e-7, 9.16e-15) Ray 3 (m, s) (3.2e-6, 1.32e-12) (1.06e-6,1.82e-13) (5.38e-7,2.68e-15) MED (ns) 113.27 177.46 1257.6 RMS Delay (ns) 100.44 17.78 25.36 d (ns) 496 118 110 Phase angles have uniform distributions over [0 2p]. Amplitude statistics are provided in the table. MED , RMS delay spread and channel length are used to compute the ray locations. Contribution Slide 14 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Ray Locations (2 Ray Model) • Two ray model is h(t ) a1 exp( j1 ) (t t1 ) a2 exp( j 2 ) (t t 2 ) • Second moment of power delay profile can be computed using mean excess delay and rms delay spread 2 2 2 rms ( ) • Two Rayleigh random variables with mean and variance corresponding to mean and variance of the two rays are generated. • Two uniformly distributed random phases over [0, 2p] are generated as well. • We have Contribution (a12t1 a22t 2 ) and (a12 a22 ) Slide 15 (a12t12 a22t 22 ) (a12 a22 ) . 2 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Ray Locations (2 Ray Model) - Cont’d • Ray locations are found by solving the system of equation: t1 and where Contribution a12 k1 a14 k12 (a12 a 22 a14 )( k12 a 22 k 2 ) a12 a 22 a14 k1 a12t1 t2 a22 k1 (a12 a 22 ) and k 2 (a12 a22 ). 2 Slide 16 Shahriar Emami, Freescale Semiconductor t 3 t1 d t 3 t1 d July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Ray Locations (3 Ray Model) • Three ray model is h(t ) a exp( j ) (t t ) a exp( j ) (t t ) a exp( j ) (t t ) 1 1 1 2 2 2 3 3 3 • Second moment of power delay profile can be computed using mean excess delay and rms delay spread 2 2 rms ( ) 2 • and t 3 t1 d. Three Rayleigh random variables with mean and variance corresponding to mean and variance of the two rays are generated. • Three uniformly distributed random phases over [0, 2p] are generated as well. • (a12 t1 a 22 t 2 a32 t 3 ) We have and (a12 a 22 a32 ) Contribution Slide 17 (a12 t12 a 22 t 22 a32 t 32 ) . 2 2 2 (a1 a 2 a3 ) 2 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Ray Locations (3 Ray Model) - Cont’d • The first ray locations are found by solving the following equation: A t12 B t1 C 0 where a12 a32 A (a a )(1 ) a 22 2 1 2 3 , K ( ( ) )(a and Second and third rays are given by K1 (a12 a22 a32 ) • 2( K1 a32 d )( a12 a32 ) B 2a d a 22 2 3 2 2 rms 2 2 1 a22 a32 ) , ( K1 a32 d ) 2 C a d K2 a 22 2 3 2 . ( K1 a32 d (a12 a32 )t1 ) t2 a 22 and Contribution t 3 d t1 . Slide 18 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Terrain variations • High correlation • Low correlation Contribution Environment A Height = 0.1 m & high correlation Environment B Height = 0.1 m & low correlation Environment C Height = 0.3 m & high correlation Environment D Height = 0.3 m & low correlation Environment E Height = 0.5 m & high correlation Environment F Height = 0.5 m & low correlation Slide 19 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Terrain variations- Cont’d Contribution Environment 2 ray model 3 ray model A 68.97 85.55 B 76.09 94.35 C 77.37 91.79 D 75.12 91.57 E 80.21 90.75 F 83.32 93.92 Slide 20 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Received Power, Mean Excess Delay (MED) and RMS Delay Spread • Estimated over a number of environments A B C D E F Rx. Power (dBm) -80.8 -80.8 -80.8 -81 -80 -80.6 MED (ns) 1980 1985 1990 2041 1997 1970 45 45 47 46 46 47.35 RMS Delay (ns) Contribution Slide 21 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulation Results—Ground Conditions • Ground conditions (wet or dry) has very little impact on received signal power or delay spread. Constrained Channel Sounding 1 0.9 Dry Wet 0.8 Probability (X < Xo) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -180 Contribution -160 -140 -120 Power (dBm) Slide 22 -100 -80 -60 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Polarization Diversity 1 Probability (X < Xo) 0.8 0.6 0.4 0.2 0 -250 Vertically Polarized Transmit Antenna Horizontally Polarized Transmit Antenna -200 -150 -100 -50 Power (dBm) • Polarization diversity is not beneficial. Contribution Slide 23 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Additional Scatterers Typical simulation result for 1 tractor Tractor Contribution Slide 24 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Additional Scatterers • Consider a few scenarios where additional scatterers are tossed in the farm environment • Determine the figure of merit for each 2 ray mode 3 ray model Scenario 1 70.79 91.94 Scenario 2 68.40 86.30 Scenario 3 64.82 85.56 • Considerable amount of scattering occurs in some regions in Scenario 3. Even three ray model is insufficient. Contribution Slide 25 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Summary and Conclusions UWB Ray Tracing: • UWB channel sounding is accomplished with the aid of narrow band ray tracing. • Ray tracer utilizes realistic antennas and appropriate material properties. • CIR of UWB channel is found by superposition of CIR of individual narrow bands responses. Channel Modeling Results: • Two ray and three ray channel models were proposed. • Procedures for generating channel models were discussed. • Percentage of locations capturing 90% of PDP energy was selected as the figure of merit. • Three ray channel model is superior to two ray model . • Both models were found to be insensitive to terrain variations. Simulation Results. • RF parameters appear almost insensitive to ground conditions. • Ground conditions (wet or dry) have little impact on coverage and delay spread. • Transmit polarization diversity not helpful in farm environment. Contribution Slide 26 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Back-up Slides Contribution Slide 27 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Material Properties Pellat-Debye Equations for loss at single relaxation time. Real permittivity exhibits lowpass frequency response. Imaginary part exhibits bandpass response. Regions can be separated for different relaxation times. Temperature effects are not modeled, but only affected by change in density of dielectric material. Reference Data for Engineers: Radio, Electronics, Computer & Communications, 8th Ed., Carmel, Indiana: SAMS, Prentice-Hall Computer Pub., 1993. Contribution Slide 28 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulation Results—Channel Sounding Constrained Channel Sounding 1 Dry Wet 0.9 • Channel (uniform) sounding leads to larger received power as compared to constrained channel (FCC-mask compliant) sounding. 0.8 FCC-mask complaint Probability (X < Xo) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -180 -160 -140 -120 Power (dBm) -100 -80 -60 -80 -60 Channel Sounding 1 0.9 Dry Wet 0.8 Probability (X < Xo) 0.7 Uniform sounding 0.6 0.5 0.4 Over 10dB difference 0.3 0.2 0.1 0 -180 Contribution Slide 29 -160 -140 -120 Power (dBm) -100 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulation Results— “High-pass” or “Band-pass” Sounding High-pass Contribution 0.9 High Pass Band Pass 0.8 0.7 Probability (X < Xo) • “Band-pass” sounding results in +1 dB higher received power compared to “highpass” sounding. HP and BP Constrained Channel Sounding 1 0.6 0.5 0.4 0.3 0.2 0.1 0 -160 -140 -120 -100 Power (dBm) -80 -60 -40 Band-pass Slide 30 Shahriar Emami, Freescale Semiconductor July 12, 2004 doc.: IEEE 802.15-04-0325-00-004a Simulation Results— Channel Impulse Response • CIR is similar to two-ray model. -6 x 10 2 Amplitude 1.5 1 0.5 1.01 Contribution 1.02 1.03 time (s) 1.04 Slide 31 1.05 1.06 -6 x 10 Shahriar Emami, Freescale Semiconductor