doc.: ieee 802.15-04-0325-00-004a contribution july 12, 2004 shahriar emami, freescale...

July 12, 2004

Shahriar Emami, Freescale SemiconductorSlide 1

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

Contribution

Project: IEEE 802.15 Study Group for Wireless Personal Area Networks (WPANs)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.

July 12, 2004


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

Contribution

An Ultra-Wideband Channel Modeland Coverage for Farm/Open-Area

Applications

Shahriar Emami, Celestino A. Corral and Gregg Rasor

Freescale Semiconductor

July 12, 2004


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

Contribution

Outline• 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

July 12, 2004


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

Contribution

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

July 12, 2004


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

Contribution

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

July 12, 2004


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

Contribution

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)

July 12, 2004


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

Contribution

Approach- Cnt’d

-14.8-13.8

-12.8-11.4

-11.2Energy of band concentrated in high band frequency

3.10 4.24 5.34 6.72 8.64 10.6

• Constrained Channel Sounding

July 12, 2004


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

Contribution

Simulation Set-Up3-D omni antenna pattern used

Omni pattern assumed at all frequencies

Farm area consists of two-story wood home and metal grain silo. Ground is not flat; has slight variations in height.

omni antenna above house

omni antenna near ground

• 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.

July 12, 2004


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

Contribution

Coverage Results

• Highest level -64.4 dBm

Wet soil

July 12, 2004


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

Contribution

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

. 3 Ray Model

)()exp()()exp()( 222111 ttjattjath

)3()3exp(3)2()2exp(2)1()1exp(1)( ttjattjattjath

July 12, 2004


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

Contribution

• 2 Ray Model

• 3 Ray Model

t1

t2

a1

a2

Block Diagram Representation

t1

t2

t3

a1

a3

a2

July 12, 2004


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

Contribution

Simulation Results—Ray Statistics

• Statistics of the two rays are found to be Rayleigh distributed.

0 1 2 3 4 5 6 7 8

x 10-6

0

50

100

150Histogram of the Largest Ray

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 10-6

0

50

100

150

200Histogram of the Second Largest Ray

July 12, 2004


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

Contribution

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.

3 ray model is superior to 2 ray model.

65 70 75 80 85 90 95 1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

July 12, 2004


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

Contribution

Channel Model Parameters

• Phase angles have uniform distributions over [0 ].• Amplitude statistics are provided in the table.• MED , RMS delay spread and channel length are used to compute the ray locations.

CM1 (5 m) CM2 (15 m) CM3 (75 m)

Ray 1 (m, (1.8e-5, 1.5e-10) (8e-6, 1.36e-11) (4.8e-6,1.49e-12)

Ray 2 (m, (1.6e-6, 2.35e-14) (2.2e-6, 1.3e-12) (6.7e-7, 9.16e-15)

Ray 3 (m, (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

July 12, 2004


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

Contribution

Ray Locations (2 Ray Model)• Two ray model is

• Second moment of power delay profile can be computed using mean excess delay and rms delay spread

• 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, 2] are generated as well.

• We have and .

222 )( rms

)()exp()()exp()( 222111 ttjattjath

)()(

22

21

2221

21

aatata

)(

)(22

21

22

22

21

212

aatata

July 12, 2004


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

Contribution

Ray Locations (2 Ray Model) - Cont’d

• Ray locations are found by solving the system of equation:

and

where and .

41

22

21

222

21

41

22

21

21

411

21

1

))((aaa

kakaaakakat

22

1211

2 atakt

)( 22

211 aak 22

2212 )( aak

July 12, 2004


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

Contribution

Ray Locations (3 Ray Model)

• Three ray model is

• Second moment of power delay profile can be computed using mean excess

delay and rms delay spread

and .• 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, 2] are generated as well.

• We have and .)()(

23

22

21

3232

221

21

aaatatata

)(

)(23

22

21

23

23

22

22

21

212

aaatatata

)3()3exp(3)2()2exp(2)1()1exp(1)( ttjattjattjath

222 )( rms

dtt 13 dtt 13 dtt 13 dtt 13

dtt 13

July 12, 2004


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

Contribution

Ray Locations (3 Ray Model) - Cont’d

• The first ray locations are found by solving the following equation:

where , ,

and .• Second and third rays are given by

and .

0121 CtBtA)1)(( 2

2

23

212

321 a

aaaaA

22

23

21

2312

3))((2

2a

aadaKdaB

2

2

2231

222

3)(

adaK

KdaC

)( 23

22

211 aaaK ))()(( 2

322

21

222 aaaK rms

22

123

21

231

2))((

ataadaK

t

13 tdt

July 12, 2004


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

Contribution

Terrain variations

• High correlation

• Low correlation

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

July 12, 2004


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

Contribution

Terrain variations- Cont’d

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

July 12, 2004


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

Contribution

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

RMS Delay (ns) 45 45 47 46 46 47.35

July 12, 2004


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

Contribution

Simulation Results—Ground Conditions

• Ground conditions (wet or dry) has very little impact on received signal power or delay spread.

-180 -160 -140 -120 -100 -80 -600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Constrained Channel Sounding

Power (dBm)

Prob

abili

ty (X

< X

o)

DryWet

July 12, 2004


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

Contribution

Polarization Diversity

• Polarization diversity is not beneficial.

-250 -200 -150 -100 -500

0.2

0.4

0.6

0.8

1

Power (dBm)

Prob

abili

ty (X

< X

o)

Vertically Polarized Transmit AntennaHorizontally Polarized Transmit Antenna

July 12, 2004


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

Contribution

Additional Scatterers

Tractor

Typical simulation result for 1 tractor

July 12, 2004


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

Contribution

Additional Scatterers

• Consider a few scenarios where additional scatterers are tossed in the farm environment

• Determine the figure of merit for each2 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.

July 12, 2004


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

Contribution

Summary and ConclusionsUWB 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.

July 12, 2004


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

Contribution

Back-up Slides

July 12, 2004


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

Contribution

Material PropertiesPellat-Debye Equations for loss at single relaxation time. Real permittivity exhibits low-

pass frequency response. Imaginary part exhibits band-pass 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.

July 12, 2004


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

Contribution

Simulation Results—Channel Sounding

• Channel (uniform) sounding leads to larger received power as compared to constrained channel (FCC-mask compliant) sounding.

-180 -160 -140 -120 -100 -80 -600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Constrained Channel Sounding

Power (dBm)

Prob

abili

ty (X

< X

o)

DryWet

-180 -160 -140 -120 -100 -80 -600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Prob

abili

ty (X

< X

o)

Power (dBm)

Channel Sounding

DryWet

Over 10dB difference

FCC-mask complaint

Uniform sounding

July 12, 2004


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

Contribution

Simulation Results—“High-pass” or “Band-pass” Sounding

• “Band-pass” sounding results in +1 dB higher received power compared to “high-pass” sounding.

High-pass Band-pass

-160 -140 -120 -100 -80 -60 -400

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1HP and BP Constrained Channel Sounding

Power (dBm)Pr

obab

ility

(X <

Xo)

High PassBand Pass

July 12, 2004


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

Contribution

Simulation Results—Channel Impulse Response

• CIR is similar to two-ray model.

1.01 1.02 1.03 1.04 1.05 1.06

x 10-6

0.5

1

1.5

2

x 10-6

time (s)

Ampl

itude

doc.: ieee 802.15-04-0325-00-004a contribution july 12, 2004 shahriar emami, freescale...

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