System and method for estimating separation distance between impulse radios using impulse signal amplitude

• US 6,700,538 B1
• Filed: 03/29/2000
• Issued: 03/02/2004
• Est. Priority Date: 03/29/2000
• Status: Expired due to Term

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Richards, James L.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/537,263
• Time in Patent Office: 1,434 Days
• Field of Search: 342/458, 455/266
• US Class Current: 342/458
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: H04B 2001/6908 using time hopping

Abstract

An impulse radio system estimates a separation distance between an impulse radio transmitter and an impulse radio receiver. The system includes an impulse transmitter that transmits an impulse signal having an ultra-wideband frequency characteristic. An impulse receiver spaced from the transmitter receives the transmitted impulse signal and measures a signal strength of the received impulse signal. The receiver estimates the separation distance based on the measured signal strength. The receiver classifies a signal propagational/multipath environment using the received impulse signal, and then selects a radio propagation path loss model corresponding to a classified multipath environment. The receiver translates the measured signal strength to a separation distance based on the selected radio propagation path loss model.

Claims

1. In an impulse radio system, a method of estimating a separation distance between an impulse radio transmitter and an impulse radio receiver, comprising the steps of:

(a) transmitting an impulse signal from the transmitter, the impulse signal having one of an ultra-wideband and medium wideband frequency characteristics;

(b) receiving the transmitted impulse signal at a receiver spaced from the transmitter;

(c) measuring a signal strength of the received impulse signal;

(d) classifying a multipath environment at the receiver using the received impulse signal;

(e) selecting at least one radio propagation path loss model from a plurality of different radio propagation path loss models based on said classifying step; and

(f) estimating the separation distance based on the selected radio propagation path loss model.

2. The method of claim 1, wherein step (f) includes the step of:

estimating the separation distance using a predetermined radio signal propagation loss model.

3. The method of claim 1, wherein said classifying step includes the steps of:

determining a multipath amplitude decay time of the received impulse signal at the receiver;

matching the multipath amplitude decay time to one of a plurality of predetermined multipath amplitude decay time ranges each associated with a respective one of the plurality of different radio propagation path loss models; and

selecting a radio propagation path loss model associated with the matched multipath amplitude decay time range.

4. The method of claim 1, further comprising the step of selecting the radio propagation path loss model from one of

5. The method of claim 1, wherein step (b) includes the step of receiving a plurality of impulse signals at the receiver corresponding to the transmitted impulse signal, the plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of the plurality of received impulse signals having a respective signal strength at the receiver;

and wherein step (f) includes the step of

estimating the separation distance based on a selected one of the plurality of received impulse signals having a greatest signal strength among the plurality of received impulse signals.

6. The method of claim 1, wherein step (b) includes the step of receiving a plurality of impulse signals at the receiver corresponding to the transmitted impulse signal, the plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of the plurality of received impulse signals having a respective signal strength and a respective time of arrival at the receiver;

and wherein step (f) includes the step of estimating the separation distance based on a selected one of the plurality of received impulse signals having an earliest time of arrival at the receiver.

7. The method of claim 1, wherein step (b) includes the step of receiving a plurality of impulse signals at the receiver corresponding to the transmitted impulse signal, the plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of the plurality of received impulse signals having a respective signal strength at the receiver;

and wherein step (f) includes the step of estimating the separation distance based on a selected number N of the plurality of received impulse signals having the greatest respective signal strengths among the plurality of received impulse signals, where N is an integer equal to or less than the number of the plurality of impulse signals.

8. The method of claim 1, wherein step (b) includes the step of receiving a plurality of impulse signals at the receiver corresponding to the transmitted impulse signal, the plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of the plurality of received impulse signals having a respective signal strength and a respective time of arrival at the receiver;

and wherein step (d) includes the step of classifying the multipath environment based on a signal strength decay envelope of the plurality of received impulse signals.

9. The method of claim 1, further comprising the step of indicating when the estimated separation distance corresponds to a predetermined separation distance.

10. An impulse radio system for estimating a separation distance between an impulse radio transmitter and an impulse radio receiver, comprising:

a transmitter for transmitting an impulse signal having one of an ultra-wideband and medium wideband frequency characteristics;

a receiver spaced from said transmitter for receiving said transmitted impulse signal, said receiver including

a signal evaluator that measures a signal strength of said received impulse signal,

a controller that classifies a multipath environment at said receiver using said received impulse signal and selects at least one radio propagation path loss model from a plurality of different radio propagation path loss models based on the multipath environment; and

an estimator, coupled to said evaluator, that estimates the separation distance based on a selected radio propagation path loss model.

11. The system of claim 10, wherein said controller translates said measured signal strength to an estimated separation distance based on a predetermined radio signal propagation loss model.

12. The system of claim 10, wherein the controller:

determines a multipath amplitude decay time of the received impulse signal at the receiver;

matches the multipath amplitude decay time to one of a plurality of predetermined multipath amplitude decay time ranges each associated with a respective one of said plurality of different radio propagation path loss models; and

selects a radio propagation path loss model associated with a matched multipath amplitude decay time range.

13. The system of claim 10, wherein said selected radio propagation path loss model is selected from one of

14. The system of claim 10, wherein a plurality of impulse signals corresponding to said transmitted impulse signal are received at said receiver, said plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of said plurality of received impulse signals having a respective signal strength at said receiver, and wherein said estimator is configured to estimate the separation distance based on a selected one of said plurality of received impulse signals having a greatest signal strength among said plurality of received impulse signals.

15. The system of claim 10, wherein a plurality of impulse signals corresponding to said transmitted impulse signal are received at said receiver, said plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of said plurality of received impulse signals having a respective signal strength at said receiver, and wherein said estimator is configured to estimate the separation distance based on a selected one of said plurality of received impulse signals having an earliest time of arrival at said receiver.

16. The system of claim 10, wherein a plurality of impulse signals corresponding to said transmitted impulse signal are received at said receiver, said plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of said plurality of received impulse signals having a respective signal strength at said receiver, and wherein said estimator is configured to estimate the separation distance based on a selected number N of said plurality of received impulse signals having the greatest respective signal strengths among said plurality of received impulse signals, where N is an integer equal to or less than the number of said plurality of impulse signals.

17. The system of claim 10, wherein a plurality of impulse signals corresponding to said transmitted impulse signal are received at said receiver, said plurality of impulse signals including at least one impulse signal arising from radio propagation multipath effects, each of said plurality of received impulse signals having a respective signal strength at said receiver, and wherein said controller is configured to classify the multipath environment based on a signal strength decay envelope of said plurality of received impulse signals.

18. The system of claim 10, further comprising an indicator coupled to an output of said estimator, wherein said estimator drives the indicator when an estimated separation distance corresponds to a predetermined separation distance.