System and method for radar tracking using communications packets
View Patent ↗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.
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.