Radio Propagation in Hallways and Streets for UHF Communications
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Transcript of Radio Propagation in Hallways and Streets for UHF Communications
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Radio Propagation in Hallways and Streetsfor UHF Communications
Dana PorratAdvisor: Professor Donald Cox
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Outline
• Propagation in cellular systems• The over-moded waveguide model• Comparison to measurements• Applications of the model
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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
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• Street canyon effects in cities have been measured many times
• Guiding by indoor hallways – shown by measurements
Guided Radiation
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Motivation
• Insight into the propagation mechanism in hallways and streets
• Average predictions based on geometry, with reasonable detail and low complexity
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Outline
• The multi-moded waveguide model• Comparison to measurements• Applications of the model
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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
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The Smooth Waveguidex
z
d
-d
1st 2nd
8th
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The TEM mode
• Field components: Hy and Ex
• Present for 2D smooth waveguide• Not present for 3D rough
waveguide
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The Rough Waveguide
x=f(z)
x=h(z)
D
s
Correlation Length
PerturbationVariance
x
z
d
-d
Dielectric Waveguide: D. Marcuse, 1970’s
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Expansion in terms of the waveguide modes
are the amplitudes of the modes
Rough Walls
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• The wave equation for the smooth guide:
• For the rough guide:
• After manipulation:
The Perturbation Approach
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Fn(z)
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The Perturbation Solution
hold the spectrum of f(z), h(z)
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The Coupled Modes
The coupling coefficients among modes:
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• 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
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Coupled Power Equations
Loss of the nth mode Coupling from the nth mode into other modes
Coupling from other modes into the nth mode
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Power Coupling Coefficients
The coupling coefficients:
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Solution of the Coupled Eq
Solution:
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The Steady State Solution
The steady state distribution has most of power in lowest order TE mode
Mode (n)
P [d
B]
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• Development along hallway / street
• Initial conditions:• Small antenna • Junction
n
zPn
Dynamic Solutions
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Junctions
Low order modes of the main hallway couple into high order modes of the side hallway
Side Hallway
Main Hallway
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Floor and Ceiling
• Full 3D model is very complicated• Simplification: smooth perfectly
conducting floor and ceiling• Vertical and horizontal are
independent
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Indoor Measurements
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The Packard BasementPow
er
[dB
]
x [m]
y
[m]
Tx
1234
5
6
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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]
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The Packard BasementPow
er
[dB
]
x [m]
y
[m]
Tx
1234
5
6
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Power Across Hallway 1
x [m]
Pow
er
[dB
]
4.4 m
12 m
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The Packard BasementPow
er
[dB
]
x [m]
y
[m]
Tx
1234
5
6
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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]
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The Packard BasementPow
er
[dB
]
x [m]
y
[m]
Tx
1234
5
6
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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]
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The Packard BasementPow
er
[dB
]
x [m]
y
[m]
Tx
1234
5
6
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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
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Ray TracingPow
er
[dB
]
x [m]
y
[m]
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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]
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Ottawa Measurements
J. Whitteker, 1987
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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
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Ottawa Measurements
J. Whitteker, 1987
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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
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Ottawa Measurements
J. Whitteker, 1987
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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
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Applications of the Model
• Channel Capacity
• Delay Spread
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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
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400 m
The Delay Profile
The group velocity v = c cosn k
n z
[sec]
Pow
er
[dB
]
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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
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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
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Extra Slides
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The Over-Moded Waveguide
• A single long waveguide
• A junction of waveguides