CHANNEL MODEL for INFOSTATIONS

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CHANNEL MODEL for INFOSTATIONS

• ? Can this be the model for outdoors? ?

Andrej Domazetovic, WINLAB February, 23
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• OBJECTIVE

• Assuming that the channel is Ricean and using the
  measurements by Feuerstein, Rappaport et. al. in
  San Francisco (2-ray model) try to develop the
  channel model proposal described as the behavior
  of Ricean K-factor with respect to
  transmitter-receiver distance.

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• INITIAL ASSUMPTIONS

• Low transmitter antenna heights (3, 4 and 5m)
• Receiver antenna height 1.7m
• Clear line of sight path - no shadowing
• Carrier frequency 5.1 GHz
• Channel bandwidth 100 MHz
• Omnidirectional antennas
• No mobility (yet)

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• OUTLINE

• Brief overview of standard 2-ray propagation
  model
• Brief overview of Propagation over the earth
• Closer look into propagation issues
• Modified model
• Link to Ricean K-factor
• Real antenna pattern
• Conclusions/Questions

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• Standard 2-ray propagation model

Friis free space equation
Relation between power and electric field
Where EIRP - effective isotropic radiated power,
E - magnitude of radiating portion of electric
field in the far field, Rfs - free space
intrinsic impedance and Ae - antenna effective
aperture
Source Rappaport - Wireless Communications
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• Standard 2-ray propagation model

The electric field at receiver
assuming large distance from the transmitter,
Taylor series approximations, perfect ground
reflection...
Source Rappaport - Wireless Communications
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• Standard 2-ray propagation model

In measurements performed in San Francisco, it
was shown that 2-ray model is fairly good model
for microcellular urban environment
It was also shown that the path loss within first
Fresnel zone clearance is purely due to spherical
spreading of the wave front decreases as d-2 and
not d-4 (10m being the minimum T-R distance)
Source Feuerstein, Rappaport et. al. - Path
loss, Delay spread and Outage models as Functions
of Antenna Height for Microcellular System Design
- TVEH, Aug, 1994
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• Standard 2-ray propagation model

Source Feuerstein, Rappaport et. al. - Path
loss, Delay spread and Outage models as Functions
of Antenna Height for Microcellular System Design
- TVEH, Aug, 1994
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• Standard 2-ray propagation model

Fresnel zone clearance
Source Feuerstein, Rappaport et. al. - Path
loss, Delay spread and Outage models as Functions
of Antenna Height for Microcellular System Design
- TVEH, Aug, 1994
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• Propagation over a plane earth

Propagation over smooth, conducting, flat earth
Bullington
Where first term - direct wave second term -
reflected wave third term - surface wave rest -
induction field and ground secondary effects ? -
phase difference between reflected and direct
paths
Source W.C. Jakes - Microwave Mobile
Communications
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• ASSUMTIONS

Friis free space equation

• The formula is a valid predictor for Pr for d
  which are in the far-field of the transmitting
  antenna - Fraunhofer region i.e. when inductive
  and electrostatic fields become negligible and
  only radiation field remains
• df2D2/? , dfgtgtD and dfgtgt?
• For fc 5.1GHz and the antenna size D 10cm
• df33.9cm , dfgtgt10cm and dfgtgt5.9cm
• If D (largest linear dimension of antenna) and
  fc increase, so does df - attention must be paid

Source Rappaport - Wireless Communications
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• ASSUMTIONS

First Fresnel zone distance Antenna
height fd for fc5.1GHz 3m 70.47m Mobile
height1.7m 4m 118.29m 5m 179.6m
Since wavelength5.9cm, the Bullington equation
also holds (surface wave can be neglected)
Source Feuerstein, Rappaport et. al. - Path
loss, Delay spread and Outage models as Functions
of Antenna Height for Microcellular System Design
- TVEH, Aug, 1994 W.C. Jakes - Microwave
Mobile Communications
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• Ricean K-factor

Source Rappaport - Wireless Communications
Steele - Mobile Radio Communications
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• Propagation Mechanisms

Source Rappaport - Wireless Communications
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• Propagation Mechanisms

Reflection coefficient (Fresnel) depends on
material properties, frequency, incident angle
It is often related to relative permittivity
value (for lossy dielectric) - some energy
absorbed
Type of surface ? (S/m) ? Poor
ground 0.001 4 Average ground 0.005 15 Good
ground 0.02 25 Sea water 5 81 Fresh
water 0.01 81 Brick 0.01 4.44 Limestone 0.02
8 7.51 Glass at 10 GHz 0.005 4
If material is good conductor (flt?/?r?0) - not
sensitive to f For lossy dielectrics - ?0, ?r -
const. with f but ? may be sensitive
Source Rappaport - Wireless Communications
W.C. Jakes - Microwave Mobile Communications
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• Propagation Mechanisms

From Maxwells equations and Snells Law
When the first medium is free space and
Source Rappaport - Wireless Communications
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• Reflection coefficient

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• Reflection coefficient

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• Reflection coefficient

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• Reflection coefficient

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• Reflection coefficient

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• Ricean K-factor

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• Ricean K-factor

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• Ricean K-factor

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• Ricean K-factor

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• Real antenna issues

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• Ricean K-factor - antenna

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• Ricean K-factor - antenna

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• Close scatters practical issue

Assuming 100MHz bandwidth ? 200Msamples/second ?
1.5m path distance in order to detect another
path wave
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• Some hints that look promising

Source IEEE Communication magazine, Jan 2001.
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• Conclusions/Questions

• What do you think IMW or JFAI?
• What to pursuit?
• - If this idea holds, how to prove it?
• - If not, should COSTs/ITUs/etc. be investigated
  better and picked one of those models?
• If the channel is really that good ? why OFDM?
• - Simplicity for Downlink (no PAPR headache,
  implementable on Winlab hardware)
• - DS-CDMA (no near-far, fully orthogonal code
  set, multiple access)