System and method for radar tracking using communications packets

• US 7,423,576 B2
• Filed: 07/24/2006
• Issued: 09/09/2008
• Est. Priority Date: 07/24/2006
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Sahinoglu, Zafer, Gezici, Sinan
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US11/492,142
• Publication Number:
  US 20080018521A1
• Time in Patent Office: 778 Days
• Field of Search: 342/27, 342/28, 342/52, 342/57, 342/107, 342/108, 342/125, 342/189, 342/195
• US Class Current: 342/27
• CPC Class Codes: G01S 13/26 wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
• CPC Class Codes: G01S 13/30 using more than one pulse per radar period
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 7/28 Details of pulse systems

Abstract

According to the invention, IEEE 802.15.4a packets are used for communications, ranging and passive radar (detecting changes/motions, tracking objects in the environment) functionality. Changes and motions in the environment are detected by exploiting the specific preamble structure of the IEEE 802.15.4a packets. A sequence of packets transmitted through an environment is received. Each packet includes a preamble. The preamble in each packet is despread to update a reference multipath profile and to obtain a current multipath profile for a currently received packet. The reference multipath profile is compared with the current multipath profile to detect an object in the environment.

Claims

1. A method for detecting an object in an environment, comprising the steps of:

receiving a sequence of packets transmitted through an environment, each packet including a preamble;

despreading the preamble in each packet to update a reference multipath profile and to obtain a current multipath profile for a currently received packet; and

comparing the reference multipath profile with the current multipath profile to detect an object in the environment.

2. The method of claim 1, in which a format of the packet is according to an IEEE 802.15.4a standard.

3. The method of claim 1, further comprising:

determining a range between two transceivers from the sequence of pulses.

4. The method of claim 1, in which the preamble includes repetitions of a perfectly balanced ternary sequence.

5. The method of claim 1, further comprising:

receiving data in the sequence of packets.

6. The method of claim 1, in which an overall structure and format of each packet is identical.

7. The method of claim 1, further comprising:

detecting a location of the object.

8. The method of claim 1, further comprising:

determining a speed of the object.

9. The method of claim 1, further determining a direction of travel of the object.

10. The method of claim 1, in which comparing detects a plurality of objects in the environment.

11. The method of claim 1, in which the object is detected passively.

12. The method of claim 1, in which each packet further includes a physical layer header, and a payload.

13. The method of claim 1, in which the packets are transmitted using a radio signal, and the radio signal is sampled coherently.

14. The method of claim 1, in which the packets are transmitted using a radio signal, and the radio signal is sampled non-coherently.

15. The method of claim 1, in which each multipath profile has a form

$z$

( n ) = 1 N sym ⁢

∑

j = 0 N sym - 1 ⁢

⁢

y ⁡

( n + jT s ⁢

R A ) , ⁢

n = 0 , 1 , …

⁢

, T s ⁢

R A - 1 ,

where N_sym a number of sequences of symbols in the preamble, y(n) denotes an output of a despreader, T_s is a symbol time, R_A is a sample rate.

16. The method of claim 1, in which the multipath profiles in the sequence of packets are averaged to obtain the reference multipath profile.

17. The method of claim 1, further comprising:

removing ground clutter from the multipath profiles.

18. The method of claim 1, in which the object reflects the packet.

19. A system for detecting an object in an environment, comprising:

a receiver portion in a transceiver configured to receive a sequence of packets transmitted through an environment, each packet including a preamble;

a despreader configured to despread the preamble in each packet to update a reference multipath profile and to obtain a current multipath profile for a currently received packet; and

a comparator configured to compare the reference multipath profile with the current multipath profile to detect an object in the environment.