Radio Propagation in Hallways and Streetsfor UHF Communications

Dana PorratAdvisor: Professor Donald Cox

Outline

• Propagation in cellular systems• The over-moded waveguide model• Comparison to measurements• Applications of the model

Propagation Models

• Ray tracing – requires a lot of detail and computation (Bell Labs, Bertoni, Rappaport)

• Power laws – give a very general picture, weakly linked to geometry

• Usage:• Power levels – Coverage and

Interference• Other properties of link

• Street canyon effects in cities have been measured many times

• Guiding by indoor hallways – shown by measurements

Guided Radiation

Motivation

• Insight into the propagation mechanism in hallways and streets

• Average predictions based on geometry, with reasonable detail and low complexity

Outline

• The multi-moded waveguide model• Comparison to measurements• Applications of the model

Key Features

• The wavelength at 1 GHz is 30 cm – much smaller than hallways and streets Multi-moded waveguide

• The walls are not smooth Mode coupling

The Smooth Waveguidex

z

d

-d

1st 2nd

8th

The TEM mode

• Field components: Hy and Ex

• Present for 2D smooth waveguide• Not present for 3D rough

waveguide

The Rough Waveguide

x=f(z)

x=h(z)

D

s

Correlation Length

PerturbationVariance

x

z

d

-d

Dielectric Waveguide: D. Marcuse, 1970’s

Expansion in terms of the waveguide modes

are the amplitudes of the modes

Rough Walls

• The wave equation for the smooth guide:

• For the rough guide:

• After manipulation:

The Perturbation Approach

Fn(z)

The Perturbation Solution

hold the spectrum of f(z), h(z)

The Coupled Modes

The coupling coefficients among modes:

• Air filled waveguide, homogeneous material, rough boundaries

• Two dimensional model• Small roughness, compared to

• Coupling coefficients , has a Gaussian correlation with s, D• Coupling between TE-TM modes

behaves as single polarization coupling

Assumptions

Coupled Power Equations

Loss of the nth mode Coupling from the nth mode into other modes

Coupling from other modes into the nth mode

Power Coupling Coefficients

The coupling coefficients:

Solution of the Coupled Eq

Solution:

The Steady State Solution

The steady state distribution has most of power in lowest order TE mode

Mode (n)

P [d

B]

• Development along hallway / street

• Initial conditions:• Small antenna • Junction

n

zPn

Dynamic Solutions

Junctions

Low order modes of the main hallway couple into high order modes of the side hallway

Side Hallway

Main Hallway

Floor and Ceiling

• Full 3D model is very complicated• Simplification: smooth perfectly

conducting floor and ceiling• Vertical and horizontal are

independent

Indoor Measurements

The Packard BasementPow

er

[dB

]

x [m]

y

[m]

Tx

1234

5

6

Hallway 1 Power

Simulation parameters: = 3, = 0.085 S/m s2 = 0.2 m2, D = 2 m

TE initial conditions

Pow

er

[dB

]

y [m]

The Packard BasementPow

er

[dB

]

x [m]

y

[m]

Tx

1234

5

6

Power Across Hallway 1

x [m]

Pow

er

[dB

]

4.4 m

12 m

The Packard BasementPow

er

[dB

]

x [m]

y

[m]

Tx

1234

5

6

Hallway 6 Power

Simulation parameters: = 3, = 0.085 S/m s2 = 0.2 m2, D = 2 m

Uniform initial conditions

Pow

er

[dB

]

y [m]

The Packard BasementPow

er

[dB

]

x [m]

y

[m]

Tx

1234

5

6

Hallway 6 and Rooms

Simulation parameters: = 3, = 0.085 S/m s2 = 0.2 m2, D = 2 m

Uniform initial conditions

Pow

er

[dB

]

y [m]

The Packard BasementPow

er

[dB

]

x [m]

y

[m]

Tx

1234

5

6

Hallway 5 and RoomsPow

er

[dB

]

x [m]

Simulation parameters: = 3, = 0.085 S/m s2 = 0.2 m2, D = 2 m

Uniform initial conditions

Ray TracingPow

er

[dB

]

x [m]

y

[m]

Ray Tracing – Hallway 3

Simulation parameters: = 3, = 0.085 S/m, s2 = 0.2 m2, D = 2 m,

Uniform initial conditions

Pow

er

[dB

]

y [m]

Ottawa Measurements

J. Whitteker, 1987

Queen St Measurements

Distance along Street [m]

Pow

er

[dB

]

Simulation parameters: = 2.6, = 0.27 S/m s2 = 0.3 m2, D = 30 m

TE initial conditions

Ottawa Measurements

J. Whitteker, 1987

Metcalf St Measurements

Distance along Street [m]

Pow

er

[dB

]

Simulation parameters: = 2.4, = 0.26 S/m, s2 = 0.2 m2, D = 10 m,

Uniform initial conditions

Ottawa Measurements

J. Whitteker, 1987

Wellington St

Measurements

Distance along Street [m]

Pow

er

[dB

]

Simulation parameters: = 2.9, = 0.26 S/m, s2 = 0.2 m2, D = 10 m,

Uniform initial conditions

Applications of the Model

• Channel Capacity

• Delay Spread

Channel CapacityThe channel becomes ‘narrow’ at large distances, all the paths become similar

Distance along Hallway [m]

Capaci

ty [

bps/

Hz]

Max: 84 bps/Hz12 x 15

Antennas

SNR =20 dB

P. Kyritsi, 2001

400 m

The Delay Profile

The group velocity v = c cosn k

n z

[sec]

Pow

er

[dB

]

Contributions• A new waveguide model for hallways and

streets with reasonable geometric input. This low complexity model agrees with indoor and outdoor measurements and provides insight to observed phenomena

• Demonstration of guiding effects in indoor hallways

• A ‘Keyhole’ effect which limits capacity in long hallways and streets

• Insight into delay profiles from the multi-moded waveguide model

Publications• D. Porrat and D. C. Cox, UHF Propagation in Indoor Hallways.

Submitted to the IEEE Transactions on Wireless Communications, June 2002

• D. Porrat, P. Kyritsi and D. C. Cox, MIMO Capacity in Hallways and Adjacent Rooms. IEEE Globecom, November 17-21, 2002

• D. Porrat and D. C. Cox, Microcell Coverage and Delay Spread Prediction Using Waveguide Theory. URSI General Assembly August 17-24 2002

• D. Porrat and D. C. Cox, Delay Spread in Microcells Analysed with Waveguide Theory. IEEE 55th Vehicular Technology Conference 2002 Spring, May 6-9

• D. Porrat and D. C. Cox, A Waveguide Model for UHF Propagation in Streets. The 11th Virginia Tech/MPRG Symposium on Wireless Personal Communications, June 6-8, 2001

Extra Slides

The Over-Moded Waveguide

• A single long waveguide

• A junction of waveguides