Simple and precise radio frequency locating system and method

• US 9,436,858 B2
• Filed: 01/10/2014
• Issued: 09/06/2016
• Est. Priority Date: 07/11/2011
• Status: Expired due to Fees

• Current Assignee: Westvalley Digital Technologies Incorporated
• Original Assignee: Westvalley Digital Technologies Incorporated
• Inventors: Liao, Jason Y.
• Primary Examiner(s): Syed, Nabil
• Application Number:
  US14/152,466
• Publication Number:
  US 20140125461A1
• Time in Patent Office: 970 Days
• US Class Current: 1/1
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 5/0295 Proximity-based methods, e.g. position inferred from reception of particular signals
• CPC Class Codes: G06K 7/10118 the sensing being preceded by at least one preliminary step
• CPC Class Codes: G06K 7/10366 the interrogation device being adapted for miscellaneous applications

Abstract

Disclosed are a radio frequency locating system and method, which efficiently solve the problem of precise locating a moving target tag in a complex environment by using a method where location information is provided for a mobile tag by using low-cost fixed active RFID tags in place of a plurality of readers requiring network connection, and the location information of the mobile tag is directly transferred to a reader at the center of a locating area from a long distance by using a mobile or fixed location tag. The present invention uses a long-distance coordinator and clock information in a transmission instruction to coordinate and schedule communication time between the mobile tag and the location tag, thereby ensuring a super long battery life of the mobile tag and the location tag.

Claims

1. A simple and precise radio frequency locating system, comprising:

a location tag, a mobile tag, a coordinator, a reader, and a management computer;

wherein;

the location tag is arranged in different fixed positions in a locating area, and is configured to receive, over an F1 channel, a working instruction signal from said coordinator, and exchange information with said mobile tag over an F2 channel in a manner indicated in the working instruction signal to generate information comprising information for determining a location of the mobile tag;

the mobile tag is arranged on a moving target to be positioned or carried by the moving target, and is configured to receive, over the F1 channel, the working instruction signal from the coordinator, and exchanges the information with the location tag over the F2 channel to generate the information comprising the information for determining the location of the mobile tag;

the coordinator is connected to said management computer in a wired or wireless manner or working independently according to a predetermined program, and is configured to capture an instant when the location tag and the mobile tag receive the working instruction signal by uninterruptedly transmitting the working instruction signal to the location tag and the mobile tag over the F1 channel within a period of time, establish communication with the location tag and the mobile tag and deliver a working instruction to the location tag and the mobile tag, arrange a time and a manner to the location tag and the mobile tag to exchange the information, and a time and a manner for the location tag and the mobile tag to exchange the information with said reader;

the reader is configured to wirelessly communicate with the mobile tag or the location tag over an F3 channel, collect the information comprising the information for determining the location of the mobile tag, and transfer the collected information to the management computer in a wired or wireless manner; and

the management computer is configured to;

manage and control the entire locating system, comprising;

delivering the working instruction to the location tag and the mobile tag by the coordinator over the F1 channel, or prewriting the predetermined program for delivering the working instruction to the location tag and the mobile tag into the coordinator, receiving the information comprising the information for determining the location of the mobile tag by the reader over the F3 channel, and determining the location of the mobile tag in a predetermined manner and providing the determined location to an application program, wherein the management computer stores location information corresponding to each location tag ID;

wherein both the location tag and the mobile tag are active radio frequency identification tags that are battery-powered and are set as periodical sleeping, and intermittently monitor the working instruction signal from the coordinator over the F1 channel for an instant sufficient to capture bits for performing DNA check, both the location tag and the mobile tag have a unique ID, and the location tag further carries information of location coordinates thereof; and

a communication distance between the location tag and the mobile tag depends on a requirement on locating precision of the system on the moving target;

wherein the period of time within which the coordinator uninterruptedly transmits the working instruction signal to the location tag and the mobile tag over the F1 channel is not shorter than a sleep period of the location tag and the mobile tag.

2. The system according to claim 1, wherein the location tag and the mobile tag, intermittently monitor the working instruction signal from the coordinator over the F1 channel for an instant sufficient to capture bits to see whether a signal compliant with the DNA check of the coordinator is detected, and the location tag and the mobile tag extend the instant to receive a complete working instruction signal packet from the coordinator after having received a signal complaint with the DNA check.

3. The system according to claim 1, wherein a manner for the location tag and the mobile tag to exchange the information over the F2 channel is that one of the two types of tags is a transmitter tag, and the other is a receiver tag, the transmitter tag transmits a signal including its own ID to the receiver tag, the receiver tag transmits its ID and the received information to the reader over the F3 channel in a manner required by the system upon receiving the signal from the transmitter tag;

and when a plurality of receiver tags transmit information to the reader, communication between the receiver tags and the reader requires anti-signal collision.

4. The system according to claim 3, wherein:

in the working instruction transmitted by the coordinator to the mobile tag and the location tag, time arrangement for transmitting information by a transmitter tag to the receiver tag comprises;

periodically transmitting a signal outside within a period of time by the transmitter tag, and waiting to receive the signal by the receiver tag from the transmitter tag within one or a plurality of time periods, within the period of time, not shorter than a transmission period of the transmitter tag;

or

transmitting a signal by the transmitter tag to the receiver tag based on a specific timeslot allocated by the coordinator and a time sequence, and receiving the signal by the receiver tag from the transmitter tag within the specific timeslot; and

in the working instruction transmitted by the coordinator to the mobile tag and the location tag, the transmitting a signal by the transmitter tag to the receiver tag comprises;

when the transmitter tag is the location tag, transmitting the signal by all location tags using same or different single fixed power determined by a system location precision requirement or transmitting the signal using a plurality of power according to an ascending order of transmit power, or

when the transmitter tag is the mobile tag, transmitting the signal by all mobile tags using single fixed power determined by a system location precision requirement or transmitting the signal using a plurality of power according to an ascending order of transmit power.

5. The system according to claim 4, wherein during determining the specific location of a mobile tag, under the prerequisite a maximum communication distances between related location tags and mobile tags are the same, the location of the mobile tag is determined as follows:

if only one location tag is capable of communicating with a mobile tag, the location of the location tag is the location of the mobile tag;

if two or three location tags are capable of communicating with a mobile tag, the geometric center of the two or three location tags is the location of the mobile tag;

if more than three location tags are capable of communicating with a mobile tag, the geometric center of a location tag with a most robust RSSI signal is the location of the mobile tag, or

the location of the mobile tag is a location that is calculated according to location coordinates of the three location tags, corresponding RSSI values thereof, and physical and geometric relationships between the information;

or

the location of the mobile tag is a location that is calculated using another radio frequency signal locating method according to other information obtained by exchange between the location tag and the mobile tag;

wherein in one-dimensional or three-dimensional space, the number of location tags involved in the method is adaptively adjusted.

6. The system according to claim 5, wherein when Cell-ID-based location is employed, a maximum communication distance between the location tag and the mobile tag is controlled according to ¾

of a spacing of the location tags.

7. The system according to claim 4, wherein when the coordinator requests the location tag and the mobile tag to exchange the information within the specific timeslot by uninterruptedly transmitting the working instruction signal packet to the location tag and the mobile tag, especially when a plurality of transmitter tags enter small timeslots allocated thereto to transmit signals to the receiver tags based on a predetermined time sequence, each of the working instruction signal packets is capable of transferring clock information to the mobile tag and the location tag, comprising:

transferring the clock information to the mobile tag and the location tag by numbering, based on a time sequence, each of the transmitted working instruction signal packets, wherein each mobile tag and each location tag work in a small timeslot assigned thereto according to the clock information.

8. The system according to claim 7, wherein when the transmitter tag is the location tag and the receiver tag is the mobile tag, the mobile tag, after obtaining real-time location information or location-related information thereof by receiving the information transmitted by the location tag, transfers the information through the reader to the management computer in the following ways:

A. the mobile tag immediately transmits the information over the F3 channel to the reader;

B. the mobile tag firstly records the real-time location information, or real-time location information obtained by simply calculating the location-related information in a memory thereof, and transfers recorded path information through the reader to the management computer only after receiving from the management computer an instruction for reading the path information.

9. The system according to claim 8, wherein when the transmitter tags transmit the signals to the receiver tags, in addition to controlling transmit power and transmission manner of the transmitter tags such that the receiver tags are only capable of receiving signals from a limited number of adjacent transmitter tags, the limited number of transmitter tags transmit the signals within different small timeslots in a communication timeslot, comprising:

employing a timeslot Aloha manner;

using differences between least significant bits of a location ID to allocate the small timeslots; and

when the transmitter tag is the location tag, pre-setting different fixed transmission delays corresponding to lengths and locations of the allocated small timeslots, and deploying the location tags having the same fixed transmission delay in a staggered manner during deployment of the location tags.

10. The system according to claim 8, wherein when the receiver tags transmit information to the reader, the small timeslots for transmitting signals are allocated to the receiver tags according to the known ID of each of the receiver tags by using the clock information transferred over the working instruction signal packet from the coordinator.

11. The system according to claim 1, wherein the F1, F2, and F3 channels are different from each other, and the F1 channel and F2 channel are the same only when the coordinator communicates with the location tag and the mobile tag and the mobile tag communicates with the location tag in a time staggered manner;

and analogously, the F2 channel and F3 channel are the same when the location tag communicates with the mobile tag and the mobile tag or the location tag communicates with the reader in a time staggered manner.

12. A simple and precise radio frequency locating method, comprising:

a coordinator, a reader, a management computer, a mobile tag, and a location tag having a fixed location;

wherein the coordinator captures an instant when the location tag and the mobile tag monitor a working instruction signal after waking up by uninterruptedly transmitting, over an F1 channel within a period of time, the working instruction signal to the location tag and the mobile tag that intermittently monitor, over the F1 channel, the working instruction signal for an instant sufficient to capture bits for performing DNA check, establishes communication with the location tag and the mobile tag and delivers a working instruction to the location tag and the mobile tag by using the established communication, and arranges a communication time and a communication manner between the mobile tag and the location tag, and the mobile tag and the location tag, and the reader;

wherein information exchange between the mobile tag and the location tag comprises;

information exchange for locating of the mobile tag;

wherein location information of the mobile tag is generated by information exchange between the location tag having the fixed location and the mobile tag, and is transmitted to the reader connected to the management computer by directly using the mobile tag or the location tag in a wireless manner;

wherein during arrangement of communication between the location tag and the mobile tag, the number of location tags that may communicate with the same mobile tag is controlled within a desired range by controlling power for transmitter tags of the location tag and the mobile tag to transmit the signals;

wherein during communication between the mobile tag and the location tag, and the mobile tag and the location tag, and the reader, when a plurality of tags simultaneously transmit signals to a same receiver tag of the location tag and the mobile tag or reader, anti-signal collision is employed, comprising;

employing a timeslot Aloha manner;

using differences between least significant bits of a location ID to allocate small timeslots;

wherein during transmitting information by the location tag or the mobile tag to the reader, the small timeslots for transmitting signals are allocated to the receiver tags according to the known ID of each location tag or mobile tag in a locating area by using the clock information transferred over the working instruction signal packet from the coordinator.

13. The method according to claim 12, wherein when the arranging by the coordinator the time for communication between the location tag and the mobile tag by carrying clock information in each uninterruptedly transmitted working instruction signal packet comprises:

transferring the clock information to the location tag and the mobile tag by numbering each transmitted working instruction signal based on a time sequence;

communicating by the location tag and the mobile tag within an assigned timeslot according to the clock information;

wherein particularly, when the plurality of transmitter tags transmit information to the same receiver tag or reader, the transmitter tags transmit, by using the clock information and based on a predetermined time sequence, the information within different small timeslots in the assigned timeslot to address signal collision.

14. The method according to claim 12, wherein with respect to signal collision during sending signals by a plurality of adjacent location tags to the mobile tag, different fixed transmission delays are set for the plurality of adjacent location tags to prevent signal collision.

15. The method according to claim 12, wherein during communication between the mobile tag and the location tag, and the mobile tag and the location tag, and the reader, if a larger number of tags transmit signals to the same receiver tag or reader, the receiver tag or reader fails in processing due to large volume of the information;

in this case, the transmitter tags are grouped according to the IDs thereof, and spacing of the location tags is reduced using time division or frequency division, or a governing range of each reader is narrowed, or a combination of such measures is employed, to reduce signal processing volume for each receiver tag or reader within a unit time.

16. The method according to claim 12, wherein in addition to the reader that collects location information of the mobile tag in a wireless manner and is connected to the management computer in a specific locating area, no any other reader is required to generate the location information of the mobile tag;

precision of locating the mobile tag is improved by increasing the number of location tags, shortening spacing between deployed location tags, controlling a maximum communication distance between the location tag and the mobile tag, improving a calculation method of the location precision using the collected related information for determining the location of the mobile tag.