CHARACTERISATION OF A WIRELESS COMMUNICATIONS LINK

• US 20120225665A1
• Filed: 06/18/2010
• Published: 09/06/2012
• Est. Priority Date: 06/19/2009
• Status: Active Grant

• Current Assignee: Cohda Wireless Pty Ltd.
• Original Assignee: Cohda Wireless Pty Ltd.
• Inventors: Alexander, Paul Dean, Haley, David Victor Lawrie
• Granted Patent: US 9,319,157 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: H04B 17/104 of other parameters, e.g. DC offset, delay or propagation times
• CPC Class Codes: H04B 17/27 for locating or positioning the transmitter
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04B 17/391 Modelling the propagation channel
• CPC Class Codes: H04W 52/242 taking into account path loss

Abstract

A system and method are described for characterising a wireless communications link as line-of-sight (LOS) or non line-of-sight (NLOS). The method comprises receiving data (T) representing a position of a transmitter, receiving data (R) representing a position of a receiver, receiving a measure of transmitted power at an output of the transmitter (PT) and receiving a measure of received power at an input to the receiver (PR). An NLOS detector (400) generates at least one non line-of-sight metric to characterise the wireless link between the transmitter and the receiver based on the position of the receiver, the position of the transmitter, the transmitted power and the received power.

Claims

1. A method for characterising a wireless communications link, comprising:

receiving data representing a position of a transmitter;

receiving data representing a position of a receiver;

receiving a measure of transmitted power at an output of the transmitter;

receiving a measure of received power at an input to the receiver;

generating at least one non line-of-sight metric to characterise the wireless link between the transmitter and the receiver based on the position of the receiver, the position of the transmitter, the transmitted power and the received power; and

outputting the non line-of-sight metric to characterise the wireless communications

2. The method as claimed in claim 1 comprising:

determining a distance between the transmitter and the receiver, using said position of the transmitter and position of the receiver.

3. The, method as claimed in claim 1 comprising:

determining outputs an observed path loss, using said measure of transmitted power and said measure of received power inputs.

4. The method as claimed in claim 3 wherein said observed path loss is calculated as:

L_O=P_T−

P_R

where;

L_O is the observed path loss;

P_T is a measure of transmitted power at the output of a transmit antenna; and

P_R is a measure of received power at the input to a receive antenna;

5. The method as claimed in claim 2 comprising:

determining a modelled path loss based on the distance and a model of path losses.

6. The method as claimed in claim 5 wherein said model of path losses is:

7. The method as claimed in claim 5 comprising adjusting a parameter of the model of path losses according to environmental conditions.

8. The method as claimed in claim 7 wherein the path loss distance exponent is adjusted in the presence of at least one of:

rain;

fog; and

snow.

9. The method as claimed in claim 7 comprising detecting said environmental conditions using at least one of:

a sensor collocated with a non line-of-sight metric generator that generates said non tine-of-sight metric;

a sensor collocated with the transmitter, an output of the sensor being communicated to the non line-of-sight metric generator;

a status of vehicle windscreen wipers where the non line-of-sight metric generator is mounted onboard a vehicle; and

a status of vehicle windscreen wipers where the transmitter is mounted onboard a. vehicle and the status is communicated to the non line-of-sight metric generator.

10. The method as claimed in claim 1 wherein said step of receiving a measure of the position of the transmitter comprises at least one of:

determining a fixed location of the transmitter;

obtaining the measure from a global positioning system (GPS);

retrieving the position from stored data; and

extracting the position of the transmitter from data transmitted to the receiver.

11. The method as claimed in claim 1 wherein said measure of transmitted power input is provided by at least one of:

a fixed level;

a measure relative to some stage of the transmitter prior to a transmit antenna;

stored data; and

inclusion in data transmitted to the receiver.

12. The method as claimed in claim 1 wherein said measure of received power input is provided by at least one of:

output from the receiver;

a measure relative to receiver input or some stage prior to the receiver input;

stored data.

13. The method as claimed in claim 1 comprising receiving at least one parameter used to calculate said measure of transmitted power input or said measure of received power input, the parameter comprising at least one of:

information regarding system losses;

information regarding system gains;

antenna configuration; and

antenna gain.

14. The method as claimed in claim 5 comprising calculating a path loss difference between an observed and modelled path losses as:

Δ

L=L_O−

L_M

where;

Δ

L is the path loss difference;

L_O is the observed path toss; and

L _M is the modelled path toss.

15. The method as claimed in claim 14 comprising mapping said path loss difference to a non line-of-sight metric value prior to output.

16. The method as claimed in claim 15 wherein said mapping comprises at least one of:

said path loss difference mapped onto said non line-of-sight metric according to some predetermined function;

said path loss difference mapped onto a predetermined said non line-of-sight metric assigned to said path loss difference value;

said path loss difference and said transmitter-to-receiver distance mapped onto said non line-of-sight metric according to some predetermined function;

said path loss difference and said transmitter-to-receiver distance mapped onto a. predetermined said non line-of-sight metric assigned to that combination of said path loss difference and said transmitter-to-receiver distance;

a function that quantizes said path loss difference; and

a function that quantizes said transmitter-to-receiver distance.

17. The method as claimed in claim 15 wherein said mapping comprises segmenting input space into bins.

18. The method as claimed in claim 17 wherein each said bin is defined by predetermined lower boundary and upper boundary, and said output metric values are assigned to each bin,

19. The method as claimed in claim 17 wherein said bin segmentation comprises at least one of:

two bins, with a boundary between bins selected such that the boundary demarcates the expected value of said path loss difference input as either line-of-sight (LOS) or non line-of-sight; and

three bins, with a boundary between first and second bins selected such that the boundary demarcates the expected value of said path loss difference input as either line-of-sight or unknown, and a boundary between second and third bins selected such that the boundary demarcates the expected value of said path loss difference input as either unknown or non line-of-sight.

20. The method as claimed in claim 1 comprising calculating an observed path loss for each of a plurality of receive antenna.

21. The method for characterising a wireless communications link, comprising:

receiving data representing a distance between a transmitter and a receiver;

receiving a measure of transmitted power at an output of the transmitter;

receiving a measure of received power at an input to the receiver;

generating at least one non line-of-sight metric to characterise the wireless link between the transmitter and the receiver based on the distance, the transmitted power and the received power; and

outputting the non line-of-sight metric to characterise the wireless communications link.

22. A non-transient computer program product comprising machine readable program code recorded on a machine readable recording medium, for controlling the operation of a data processing apparatus on which the program code executes to perform a method for characterising a wireless communications link, comprising:

receiving data representing a position of a transmitter;

receiving data representing a position of a receiver;

receiving a measure of transmitted power at an output of the transmitter;

receiving a measure of received power at an input to the receiver;

generating at least one non line-of-sight metric to characterise the wireless link between the transmitter and the receiver based on the position of the receiver, the position of the transmitter, the transmitted power and the received power; and

outputting the non line-of-sight metric to characterise the wireless communications link.

23. An apparatus for characterising a wireless communications link, comprising:

means for receiving data representing a position of a transmitter;

means for receiving data representing a position of a receiver;

means for receiving a measure of transmitted power at an output of the transmitter;

means for receiving a measure of received power at an input to the receiver;

means for generating at least one non line-of-sight metric to characterise the wireless link between the transmitter and the receiver based on the position of the receiver, the position of the transmitter, the transmitted power and the received power; and

means for outputting the no tine-of-sight metric to characterise the wireless communications link.