System and method for position awareness for minimizing power consumption in sensor network environment

• US 20070133352A1
• Filed: 12/05/2006
• Published: 06/14/2007
• Est. Priority Date: 12/08/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Tae, Kim, Jin, Lee, Woo, Lee, Won, Park, Seung, Lee, Kwang, Park, II, Eom, Doo
• Granted Patent: US 7,499,376 B2
• Time in Patent Office: Days
• US Class Current: 367/128
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves

Abstract

Provided are a system and method for position awareness that can be used indoors in a large-scale environment and can minimize generation of radio frequency (RF) and ultrasonic waves in a wireless sensor network including low-priced sensor nodes capable of precise position measurement, thus improving energy efficiency by reducing unnecessary power consumption. The method includes the steps of: (a) calculating initial position coordinates using beacon information received from adjacent beacons through a broadcast beacon solicitation signal, sending a synchronization signal to the beacons, and synchronizing the beacons; (b) receiving ultrasonic waves generated from the adjacent beacons activated by a broadcast start message, and calculating position coordinates; and (c) when the calculated position coordinates correspond to a predetermined hand-off threshold position, transmitting a hand-off process message to a newly activated beacon, and executing a hand-off process routine.

Claims

1. A method for position awareness, comprising the steps of:

(a) calculating initial position coordinates using beacon information received from adjacent beacons through a broadcast beacon solicitation signal, sending a synchronization signal to the beacons, and synchronizing the beacons;

(b) receiving ultrasonic waves generated from the adjacent beacons activated by a broadcast start message, and calculating position coordinates; and

(c) when the calculated position coordinates correspond to a predetermined hand-off threshold position, transmitting a hand-off process message to a newly activated beacon, and executing a hand-off process routine.

2. The method for position awareness of claim 1, wherein step (a) comprises the steps of:

(a1) broadcasting the beacon solicitation signal, which is a radio frequency (RF) signal, and transmitting the beacon solicitation signal to the beacons fixed at adjacent positions;

(a2) receiving the beacon information of the beacons receiving the beacon solicitation signal, and calculating the initial position coordinates of a receiver; and

(a3) sending the synchronization signal to the beacons, synchronizing the beacons, and receiving ultrasonic waves emitted from the beacons in response to confirmation of reception.

3. The method for position awareness of claim 1, wherein step (b) comprises the steps of:

(b1) periodically broadcasting the start message, which is an ultrasonic signal, and activating the adjacent beacons;

(b2) receiving the ultrasonic waves generated in time frames assigned in order of numbered identifications (IDs) of beacons after the activated beacons are synchronized by time compensation; and

(b3) updating information on a distance between a receiver and a beacon using the received ultrasonic waves, transmitting the distance information to a user device and a context awareness server, and calculating the position coordinates.

4. The method for position awareness of claim 3, wherein step (b1) further comprises the step of switching a beacon not receiving the start message to a low-power mode.

5. The method for position awareness of claim 3, wherein the position coordinates calculation of step (b3) comprises the steps of:

when there is data from the receiver while watching a serial interface, reading and parsing the data into three distance values; and

inputting each parsed distance value into a position coordinates calculation algorithm, calculating the position coordinates, and displaying the position coordinates on a graphic user interface (GUI).

6. The method for position awareness of claim 1, wherein step (c) comprises the steps of:

(c1) setting the hand-off threshold position considering an ultrasonic range of each beacon;

(c2) when the calculated position coordinates correspond to the set hand-off threshold position, transmitting the hand-off process message to the newly activated beacon; and

(c3) broadcasting a beacon solicitation signal to the beacon over a radio frequency (RF), and executing the hand-off process routine.

7. The method for position awareness of claim 6, wherein the hand-off threshold position of step (c1) is set taking as a reference an ultrasonic area of a beacon having the same numbered identification (ID) as a beacon transmitting received ultrasonic waves but having a different unique ID.

8. The method for position awareness of claim 6, wherein step (c) further comprises step (c4) of responding, at a beacon receiving the beacon solicitation signal, to the beacon solicitation signal and periodically performing synchronization with a system.

9. The method for position awareness of claim 1, wherein when step (a) is finished, the beacons are kept in a standby state.

10. The method for position awareness of claim 1, wherein the signals are transmitted and received using radio frequency (RF) signals or ultrasonic signals.

11. The method for position awareness of claim 1, wherein the beacon information includes position coordinates of a beacon, a unique identification (ID), or a numbered ID.

12. The method for position awareness of claim 1, wherein the start message includes synchronization information, information on time frames T_slotⁿ according to the order of a numbered identification (ID) of each beacon, or activation information.

13. The method for position awareness of claim 12, wherein the activation information includes a unique ID of each beacon.

14. A system for position awareness, comprising:

a plurality of beacons installed at fixed positions at predetermined intervals and transmitting radio frequency (RF) signals and ultrasonic signals; and

a receiver capable of position movement, receiving the RF signals and ultrasonic signals transmitted from the beacons, and generating position measurement information on a moved position using a difference in time taken to receive the signals, reception time information, and the RF signals.

15. The system for position awareness of claim 14, further comprising:

a user device providing a function of position coordinates calculation using the information generated from the receiver and a function of a graphic user interface (GUI) displaying calculated position coordinates; and

a context awareness server recognizing a user'"'"'s position, connecting to the receiver through a serial interface, and providing a ubiquitous service to the outside through a terminal.

16. The system for position awareness of claim 14, wherein the beacons are implemented by sensor nodes each having information on at least two addresses such as a unique identification (ID) and a numbered ID.

17. The system for position awareness of claim 16, wherein the unique ID is changed according to a number of the beacons included in the system, and the numbered ID is assigned using a number from 1 to 4 in sequence regardless of the number of beacons included in the system.

18. The system for position awareness of claim 14, wherein the predetermined intervals between adjacent beacons are less than 5 m.