Method and apparatus for modeling the propagation of wireless signals in buildings

• US 6,678,525 B1
• Filed: 05/30/2000
• Issued: 01/13/2004
• Est. Priority Date: 09/18/1997
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Baranger, Harold Urey, Ullmo, Denis Jacques
• Primary Examiner(s): Banks-Harold, Marsha D.
• Assistant Examiner(s): MOORE, JAMES K
• Application Number:
  US09/580,623
• Time in Patent Office: 1,323 Days
• Field of Search: 455/422, 455/446, 455/507, 455/522, 455/525, 455/524, 455/67.1, 455/67.2, 455/67.3, 455/67.4, 455/67.6, 455/63, 455/65, 455/504, 455/506, 455/FOR.102, 455/67.11, 455/67.12, 455/67.13, 455/67.14, 455/67.16, 324/644, 324/646
• US Class Current: 455/446
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/391 Modelling the propagation channel
• CPC Class Codes: H04B 17/3913 Predictive models, e.g. based on neural network models
• CPC Class Codes: H04W 16/20 for indoor coverage or short range network deployment

Abstract

Techniques for predicting RF signal propagation in indoor environments are disclosed. A typical technique comprises six distinct phases. In one phase, the mean wall separation, {overscore (d)}, of one floor of a building is estimated. In a second phase, a reflection coefficient, s, is estimated for the floor in general. In a third phase, a number of trial RF propagation measurements are made to gather empirical data about the RF propagation characteristics of the floor. In the fourth phase, the mean wall separation, {overscore (d)}, the reflection coefficient, s, and the trial RF propagation measurements are fit, using well-known techniques, into a wireless propagation model, such as $P\left(r\right)=\frac{P_0}{2\pi D}\sqrt{\frac{\pi \xi }{2r}}{}^{-r/\xi },$

where P(r) is the measured or predicted power at a distance, r, from the transmitter, $D={\xi }^2\left[\sqrt{{\left(\frac{s}{\stackrel{\_}{d}}\right)}^2+{\left(\frac{1}{\xi }\right)}^2}-\frac{s}{\stackrel{\_}{d}}\right]$

and ξ is the parameter that is fit to the empirical data. In the fifth phase the wireless propagation model is used to predict the RF signal strength throughout the floor from a base station at a given location, and in the six phase one or more base stations are installed in the building based on the results predicted by the wireless propagation model. The fifth and sixth phases can be thereafter repeated for other building with sufficiently similar characteristics.

Claims

1. A method for placing a wireless base station inside a building, said method comprising the steps of:

estimating a mean wall separation, {overscore (d)}, of a floor of said building;

creating a wireless propagation model based on said mean wall separation, {overscore (d)};

placing said wireless base station in said building at a location based on said wireless propagation model;

radiating a trial signal with a transmit power, P₀, from a transmitter; and

measuring a received power P₁ of said trial signal at a distance, r₁, from said transmitter;

wherein said wireless propagation model is also based on said transmit power, P₀, said received power P₁, and said distance, r₁.

2. The method of claim 1 further comprising the step of estimating a reflection coefficient, s, of said floor, and wherein said wireless propagation model is also based on said reflection coefficient, s.

3. A system for placing at least one wireless base station on a given floor in a building, the number and location of said at least one wireless base station selected such that the signal from said at least one wireless base station has a power level essentially everywhere on said given floor above a threshold, the system CHARACTERIZED BY:

a transmitter for radiating a trial signal with a transmit power, P₀; and

a signal strength detector for measuring a received power P₁ of said trial signal at a distance, r₁, from said transmitter;

wherein the number and location of said wireless base station or stations is based on a wireless propagation model that involves estimation of a mean wall separation, {overscore (d)}, of said given floor,

wherein said wireless propagation model is also based on said transmit power, P₀, said received power P₁, and said distance, r₁.

4. The system of claim 3 further CHARACTERIZED IN THAT

the number and location of said wireless base station or stations is based on a wireless propagation model that involves estimation of a mean reflection coefficient, s, of the given floor.

5. A method for placing a wireless base station inside a building, said method comprising the steps of:

estimating a mean wall separation, {overscore (d)}_x, in a first direction of a floor of said building;

estimating a mean wall separation, {overscore (d)}_y, in a second direction of said floor, wherein said second direction is orthogonal to said first direction;

creating a wireless propagation model based on said mean wall separation, {overscore (d)}_x, in said first direction of said floor and said mean wall separation, {overscore (d)}_y, in said second direction of said floor;

placing said wireless base station in said building at a location based on said wireless propagation model;

radiating a trial signal with a transmit power, P₀, from a transmitter at a first location, x₀, y₀; and

measuring a received power P₁ of said trial signal at a second location, x₁, y₁;

wherein said wireless propagation model is also based on said transmit power, P₀, said first location, x₀, y₀, said received power P₁, and said second location, x₁, y₁.

6. The method of claim 5 further comprising the step of estimating an interior reflection coefficient, s(θ

), of said floor, and wherein said wireless propagation model is also based on said reflection coefficient, s(θ

).

7. A system for placing at least one wireless base station on a given floor in a building, the number and location of said wireless base stations selected such that the signal from said wireless base station or stations has a power level essentially everywhere on said given floor above a threshold, the system CHARACTERIZED BY:

a transmitter at a first location x₀, y₀ for radiating a trial signal with a transmit power, P₀; and

a signal strength detector for measuring a received power P₁ of said trial signal at a second location x₁, y₁;

wherein the number and location of said wireless base station or stations is based on a wireless propagation model that involves estimation of a mean wall separation, {overscore (d)}_x, in a first direction of said given floor and estimation of a mean wall separation, {overscore (d)}_y, in a second direction of said given floor,

wherein said wireless propagation model is also based on said transmit power, P₀, said first location x₀, y₀, said received power P₁, and said second location x₁, y₁.

8. The system of claim 7 further CHARACTERIZED IN THAT the number and location of said at least one wireless base station is based on a wireless propagation model that involves estimation of an interior reflection coefficient, s(θ

), of said given floor.

9. The system of claim 8 CHARACTERIZED IN THAT the number and location of said at least one wireless base station is based on a wireless propagation model that involves estimation of an exterior reflection coefficient, B(θ

), of said given floor.

10. A system for placing at least one wireless base station on a given floor in a building, the number and location of said at least one wireless base station selected such that the signal from said at least one wireless base station has a power level essentially everywhere on said given floor above a threshold;

CHARACTERIZED IN THAT

the number and location of said wireless base station or stations is based on a wireless propagation model that involves estimation of a mean wall separation, {overscore (d)}, of said given floor and the change in power of a trial signal when said trial signal is transmitted between two points separated by a distance r of said given floor, the system comprising;

a transmitter for radiating a trial signal with a transmit power, P₀;

a signal strength detector for measuring a received power P₁ of said trial signal at a distance, r₁, from said transmitter;

wherein said wireless propagation model is also based on said transmit power, P₀, said received power P₁, and said distance, r₁.

11. The system of claim 10 further CHARACTERIZED IN THAT

the number and location of said wireless base station or stations is based on a wireless propagation model that involves estimation of a mean reflection coefficient, s, of the given floor.

12. A system for placing at least one wireless base station on a given floor in a building, the number and location of said at least one wireless base station selected such that the signal from said at least one wireless base station has a power level essentially everywhere on said given floor above a threshold;

CHARACTERIZED IN THAT

the number and location of said wireless base station or stations is based on a wireless propagation model that involves estimation of a mean wall separation, {overscore (d)}_x, in a first direction of said given floor and estimation of a mean wall separation, {overscore (d)}_y, in a second direction of said given floor and the change in power of a trial signal when said trial signal is transmitted between two points separated by a distance r of said given floor, the system comprising;

a transmitter at a first location x₀, y₀ for radiating a trial signal with a transmit power, P₀; and

a signal strength detector for measuring a received power P₁ of said trial signal at a second location x₁, y₁;

wherein said wireless propagation model is also based on said transmit power, P₀, said first location x₀, y₀, said received power P₁, and said second location x₁, y₁.