BEACON SCHEDULING SYSTEM AND METHOD FOR PREVENTING BEACON OVERLAPPING

• US 20080137599A1
• Filed: 11/29/2007
• Published: 06/12/2008
• Est. Priority Date: 12/07/2006
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Pyo, Cheol Sig, Kim, Sun Joong, HAM, Young Hwan
• Granted Patent: US 8,121,080 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

Provided are a beacon scheduling system and method for preventing beacon overlapping in a ZigBee network including routers each with a beacon slot number according to a specific time slot. The system includes: a first router periodically transmitting beacons at a beacon interval according to a specific time slot; and a second router finding the beacon interval by scanning the beacons transmitted by the first router and transmitting beacons within the beacon interval in consideration of a superframe period for transmitting data. When a router in a sensor network operates, the router can efficiently select the beacon transmission time, and a sink node manages beacon overlapping between all the routers. Therefore, stable, low-energy consumption, and excellent performance sensor networking environments can be established in a beacon mode.

Claims

1. A beacon scheduling system for preventing beacon overlapping in a ZigBee network including routers each with a beacon slot number according to a specific time slot, the system comprising:

a first router periodically transmitting beacons at a beacon interval; and

a second router finding the beacon interval by scanning the beacons transmitted by the first router and transmitting beacons within the beacon interval in consideration of a superframe period for transmitting data.

2. The beacon scheduling system of claim 1, wherein the second router transmits beacons within a beacon interval of the second router with an interval equivalent to a predetermined beacon slot period from the beacon transmitted from the second router adjacent to the first router in the ZigBee network.

3. The beacon scheduling system of claim 2, wherein the beacon slot period is set as the sum of a superframe period for transmitting data and a beacon protection period shorter than the superframe period.

4. The beacon scheduling system of claim 2, wherein a beacon slot number of the sink node is set as “

0”

, the quotient of dividing the beacon interval by the beacon slot period is defined as the number of slots, an equal number of beacon slot numbers as the number of slots is allocated, and one of the beacon slot numbers is allocated to the first router.

5. A beacon scheduling method for preventing beacon overlapping in a ZigBee network including routers each with a beacon slot number according to a specific time slot, the method comprising:

(a) identifying beacon slot numbers of routers existing in the ZigBee network by scanning beacons of the routers;

(b) selecting a parent router to be connected among the routers;

(c) distinguishing unused beacon slot numbers, excluding the identified beacon slot numbers, among beacon slot numbers allocated within a beacon interval; and

(d) selecting one of the unused beacon slot numbers and transmitting beacons based on a difference between a beacon slot number of the selected parent router and the selected unused beacon slot number.

6. The beacon scheduling method of claim 5, wherein (a) identifying the beacon slot numbers of the routers is achieved by analyzing beacon payloads included in the scanned beacons.

7. The beacon scheduling method of claim 5, wherein, in (d), a beacon slot number adjacent to the beacon slot number of the selected parent router is selected as one of the unused beacon slot numbers.

8. The beacon scheduling method of claim 5, wherein, in (d), a beacon slot number corresponding to a value obtained as a result of operation with a modular operator is selected using the value obtained by adding the beacon slot number of the selected parent router to the value of dividing a ZigBee network address of a router which will transmit beacons into a predetermined integer.

9. The beacon scheduling method of claim 5, wherein (d) comprises calculating a delay time according to the difference between the beacon slot number of the selected parent router and the selected unused beacon slot number, and beacons are transmitted after the calculated delay time passes from receiving beacons of the parent router.

10. The beacon scheduling method of claim 5, wherein, if one of the unused beacon slot numbers selected in (d) is a beacon slot number selected for another router in the ZigBee network, the selected parent router refuses connection of a router which will transmit beacons or transmits a reset command for system initialization to the router which will transmit.

11. The beacon scheduling method of claim 5, further comprising:

(e) transmitting a message from a router with an allocated beacon slot number among the routers in the ZigBee network to a sink node in the ZigBee network, the message containing the allocated beacon slot number of the router and a scan time; and

(f) if there is a router with the same allocated beacon slot number or the same scan time as in the message, transmitting a reset command to delete the beacon slot number of one of the two routers.

12. The beacon scheduling method of claim 11, wherein (f) comprises:

determining whether an allocated beacon slot number of a router which will transmit beacons is the same as the allocated beacon slot number included in the transmitted message;

if the allocated beacon slot numbers of the two routers are the same, calculating a scan time interval using a difference between the scan times of the two routers; and

if the calculated scan time interval is not greater than the product of multiplying a beacon interval of the routers by a predetermined integer, transmitting a reset command for system initialization to one of the two routers after the time corresponding to the product passes.

13. The beacon scheduling method of claim 11, wherein, in (f), the reset command is not transmitted to any routers out of a radio wave reaching distance in which the sink node exists.