project: ieee 802.15 study group for wireless personal area networks (wpans)

May 7, 2004

Shahriar Emami, Freescale SemiconductorSlide 1

doc.: IEEE 802.15-04-0215-00-004a

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: [Ultra-Wideband Channel Model for Farm/Open-Area Applications]Date Submitted: [11 May, 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.

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Ultra-Wideband Channel Modelfor Farm/Open-Area Applications

Understanding UWB Propagation

in Open Areas Subject to

Selected Environmental Factors

The presenters wish to acknowledge the support and contributions of:

• Glafkos Stratis/Motorola

• Salvador Sibecas/Motorola

Shahriar Emami, Celestino A. Corral, Gregg Rasor

Freescale Semiconductor

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Outline

• Ultra-wideband Outdoor Channel Model Status• Special Considerations

– Approach– Frequency Selection– Simulation Setup

• Simulation Results– Ground conditions– Channel Impulse Response and Ray Statistics– Coverage

• Summary and Conclusions • Proposed Continuing Investigations

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Channel Model Status

• 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.

– 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 shall show this in simulation

We use approach considered here

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Special Considerations

• Farm areas feature isolated clusters of scatterers

• Material properties may change with frequency. (For our simulations, we assume material properties constant over frequency.) In addition, the outdoor channel is subject to environmental changes– Seasonal changes (snow, ice, etc. in some

regions)– Rain/wet conditions

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Different Absorption Regions

-6 -4 -2 0 2 4 6 8 10 12 14 16 18

Conduction

Space

Charge

Polarization

Dipole and

Ionic

Relaxation

Atomic Electronic

Absorption

60Hz

Frequency Range

Of Interest

Dielectric practically constant over frequency range of interest.

Log frequency (Hz)

R. C. Dorf (Ed.), The Electrical Engineering Handbook, 2nd Ed., Boca Raton, Florida: CRC Press, 1997.

We assume no dielectric changes

over frequency

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Approach

• Use deterministic 3-D ray tracing simulator - Employs

– geometric optics– 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

- Conventional channel sounding

- FCC emissions mask scaled channel sounding

M. F. Iskander and Z. Yun, “Propagation prediction models for wireless communication systems,” IEEE Trans. Microwave Theory Tech., vol. 50, pp. 662—673, March 2002.

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Frequency Selection

Channel Sounding “High-Pass” Sounding

0 dBm

-14.8-13.8

-12.8 -11.4 -11.2

“Band-Pass” Sounding

-14.8-13.8

-12.8 -11.4 -11.2

Energy of band concentrated in high band frequency

Energy of band concentrated in geometric center frequency

3.10 4.24 5.34 6.72 8.64 10.6 3.10 4.24 5.34 6.72 8.64 10.6

3.62 4.76 5.99 7.62 9.57

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Set-Up3-D omni antenna pattern used

Omni pattern assumed at all frequencies

Provides worst-case delay modeling

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.

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Coverage ResultsLowest Frequency – 4.24 GHz

200 m

200 m

• Highest level -64.4 dBm

• Shadowing due to metal silo evident

• Ripple due to two-ray phenomenon evident

Dry soil Wet soil and wet roof


• Smoother ripple closer to antenna

• Impact of roof more significant

TX power = 0 dBm TX power = 0 dBm

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Coverage ResultsFull Frequencies -- Channel Sounding

Dry soil


• Some deep fades are eliminated, others softened

• Ripple due to two-ray phenomenon still evident, although smooth ripple closer


• Higher signals closer to antenna

• Shadowing due to silo and roof still significant

Wet soil

TX power = 0 dBm TX power = 0 dBm

Dry/wet conditions are fairly similar

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Coverage“High-pass” and “Band-pass” Sounding

Dry soil

• High-pass sounding


• Significant shading by house as well as silo

Dry soil

• Band-pass sounding


• Range for -75 dBm sensitivity is quite low, on the order of 15 m.

High-pass and band-pass sounding are

similar

TX antenna placed at 1.5m height and at the side of the house

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation--Validation

• Powers in the different frequency bands are summed together

• Received power profile in agreement with the work of Sato and Kobayashi

TX antenna placed at 1.5m height and at the side of the house

1 0 1 0 0 1 0 0 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

D i s t a n c e [ m ]

Pat

h lo

ss [

dB]

100

101

102

103

-120

-110

-100

-90

-80

-70

-60

-50

Po

wer

(d

Bm

)

Transmitter-Receiver Separation (m)

UWB Path Loss

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Results—Ground Conditions

-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)

Pro

bab

ilit

y (X

< X

o)

DryWet

• Ground conditions (wet or dry) has almost no impact on received signal power or delay spread.

• Subsequent simulations were assuming dry conditions

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Results—Channel Impulse Response

• CIR is similar to two-ray model.

0 20 40 60 80 100 120 140 160 180-1

0

1

2

3

4

5x 10

-7

t (ns)

Rec

eive

d A

mp

litu

de

(V)

CIR of Real Part of the received signal

0 20 40 60 80 100 120 140 160 180-8

-6

-4

-2

0

2

4

6x 10

-8

Rec

eive

d A

mp

litu

de

(V)

CIR of Imaginary Part of the received signal

t (ns)

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Results—Channel RF Parameters

Scenario

A

Scenario

B

Received Power

(dBm)

-83

-74

Scenario

A

Scenario

B

Mean

Excess

Delay

(ns)

380

365

RMS Delay

(ns)

19 26

- Scenario A: transmit antenna is placed on the top of farm house

- Scenario B: transmit antenna is placed along the side of the house

Table I. 90 percentile received power Table II. 90 percentile delay spread

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Results—Ray Statistics

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

0 0.5 1 1.5

x 10-6

0

100

200

300

400Histogram of I of the Largest Component

0 0.5 1 1.5

x 10-6

0

100

200

300

400Histogram of Q of the Largest Component

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

x 10-7

0

100

200

300

400Histogram of I of the Second Largest Component

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

x 10-7

0

100

200

300

400Histogram of Q of the Second Largest Component

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

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


Power (dBm)

Pro

bab

ilit

y (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

Pro

bab

ilit

y (X

< X

o)

Power (dBm)

Channel Sounding

DryWet

Over 10dB difference

FCC-mask complaint

Uniform sounding

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

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

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

-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

1

Power (dBm)

Pro

bab

ilit

y (X

< X

o)

High Pass Channel SoundingBand Pass Channel Sounding

High-pass and band-pass sounding are

similarHigh-pass Band-pass

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Results—Coverage

100x100 30x30

Coverage

(%)

85 85

Table III. % grid Coverage, if the receiver sensitivity is -90 dBm.

-120 -110 -100 -90 -80 -70 -60 -500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Power (dBm)

Pro

bab

ilit

y (X

< X

o)

Constrained Channel Sounding (30mx30m)

-120 -110 -100 -90 -80 -70 -60 -500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9


Power (dBm)

Pro

bab

ilit

y (X

< X

o)

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Simulation Results—Channel Model

CM1* CM2* CM3* I mean 1.4092e-007 3.1052e-008 -5.8368e-009

Q mean -1.8287e-008 5.9910e-009 -4.2345e-009

MED (ns) 22.654 35.491 251.53

RMS Delay

(ns)

20 3.5565 5.0733

* The transmitter receiver separation distances are 5, 15 and 75 meters in CM1, CM2 and CM3, respectively.

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Summary and Conclusions

UWB Ray Tracing:• Ray tracing with realistic antennas and appropriate material properties was

implemented.• Analyses included all ray statistics/parameters (ray physics).• CIR of UWB channel is found by superposition of CIR of individual bands

with appropriate power weighting.

Channel Modeling Results:• 5-band approach is adequate for predicting outdoor coverage in farm

scenario as verified by prior two-ray modeling.• “High-pass” sounding yields most conservative results.• RF parameters appear almost insensitive to ground material/conditions.• 100m range achievable with -90dBm RX sensitivity.• CIR is similar to that of two-ray model. RMS delay depends on location of

antenna and statistics of the rays.• Two-ray statistics are verified to have Rayleigh distribution.

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Ongoing Investigations

• Incorporate uplink simulations.

• Alternative frequency domain based approach.

• Measurement and verification.

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

Contribution

Back-up Slides

May 7, 2004


doc.: IEEE 802.15-04-0215-00-004a

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.

project: ieee 802.15 study group for wireless personal area networks (wpans)

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