Time synchronization and routing method in wireless sensor network, and apparatus for enabling the method

• US 8,848,584 B2
• Filed: 07/11/2008
• Issued: 09/30/2014
• Est. Priority Date: 07/12/2007
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Shin, Chang Sub, Jin, Gwang Ja, Hwang, So Young, Doh, Yoonmee, Kim, Bong Soo, Pyo, Cheol Sig, Chae, Jong-Suk
• Primary Examiner(s): EBRAHIM, ANEZ C
• Application Number:
  US12/667,298
• Publication Number:
  US 20110002251A1
• Time in Patent Office: 2,272 Days
• Field of Search: None
• US Class Current: 370/311
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04J 3/0679 by determining clock distribution path in a network
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A time synchronization method in a wireless sensor network, a low power routing method using a reservation scheme, and an apparatus for performing the method are provided. The time synchronization method in the wireless sensor network may include: receiving a first synchronization request command packet from a parent node that manages time synchronization for a predetermined synchronization region; receiving, from the parent node, a second synchronization request command packet that has a transmission timestamp value of the first synchronization request command packet; and performing time synchronization for a child node based on a reception time of the first synchronization request command packet, a reception time of the second synchronization request command packet, and the transmission timestamp value of the first synchronization request command packet.

Claims

1. A time synchronization method in a wireless sensor network, the method comprising:

receiving a first synchronization request command packet from a parent node that manages time synchronization for a predetermined synchronization region;

receiving, from the parent node, a second synchronization request command packet that has a transmission timestamp value of the first synchronization request command packet; and

performing time synchronization for a child node based on a reception time of the first synchronization request command packet, a reception time of the second synchronization request command packet, and the transmission timestamp value of the first synchronization request command packet,

wherein the performing of the time synchronization comprises obtaining a difference value between the reception time of the first synchronization request command packet and the reception time of the second synchronization request command packet and adding the difference value to the transmission timestamp value of the first synchronization request command packet to thereby match time information of the child node with time information of the parent node.

2. The method of claim 1, wherein the first synchronization request command packet comprises at least one of a sync interval that denotes a synchronization cycle and a sync boundary that denotes start and end time information of the synchronization cycle.

3. The method of claim 2, wherein when the first synchronization request command packet or the second synchronization request command packet is not received in a synchronization time duration corresponding to the sync interval, the child node receives a third synchronization request command packet and a fourth synchronization request command packet from another node excluding the parent node and transmits a synchronization reply packet to the node that transmits the third synchronization request command packet and the fourth synchronization request command packet.

4. A low power routing method using a reserved scheme in a wireless sensor network, the method comprising:

performing time synchronization for the network;

broadcasting a first reservation request packet for data transfer reservation in a first time duration where all the nodes in the network are activated;

receiving a second reservation request packet corresponding to the first reservation request packet; and

transmitting data to a node having transmitted the second reservation request packet in a second time slot where all the nodes in the network are inactivated,

wherein the performing of the time synchronization comprises transmitting a first synchronization request command to a child node of a predetermined synchronization region and a second synchronization request command that has a transmission timestamp value of the first synchronization request command,

wherein the child node obtains a difference value between a reception time of the first synchronization request command and a reception time of the second synchronization request command and adds the difference value to the transmission timestamp value of the first synchronization request command to thereby match time information of the child node with time information of a parent node.

5. The method of claim 4, wherein the performing of the time synchronization further comprises

receiving a synchronization reply packet corresponding to the first synchronization request command and the second synchronization request command from the child node of the synchronization region.

6. The method of claim 4, wherein the first reservation request packet comprises a previous node address, a next node address, an end node address, and reserved slot information for transmitting the data in the second time duration, and the previous node address is an address of a node that has transmitted the first reservation request packet.

7. The method of claim 4, wherein the second reservation request packet comprises a previous node address, a next node address, an end node address, and reserved slot information for transmitting the data in the second time duration, and the previous node address is an address of a node that has transmitted the first reservation request packet.

8. A low power routing method using a reservation scheme in a wireless sensor network, the method comprising:

performing time synchronization for the network;

receiving a first reservation request packet for data transfer reservation in a first time duration where all the nodes in the network are activated;

transmitting any one of a second reservation request packet and a reservation reply packet by referring to the first reservation request packet; and

receiving data from a node having transmitted the first reservation request packet in a second time slot where all the nodes in the network are inactivated,

wherein the performing of the time synchronization comprises;

receiving a first synchronization request command packet from a parent node that manages time synchronization for a predetermined synchronization region;

receiving, from the parent node, a second synchronization request command packet that has a transmission timestamp value of the first synchronization request command packet; and

obtaining a difference value between a reception time of the first synchronization request command packet and a reception time of the second synchronization request command packet and adding the difference value to the transmission timestamp value of the first synchronization request command packet to thereby match time information of a child node with time information of the parent node.

9. The method of claim 8, wherein the first reservation request packet comprises a previous node address, a next node address, an end node address, and reserved slot information for transmitting the data in the second time duration, and the previous node address is an address of a node that has transmitted the first reservation request packet.

10. The method of claim 9, wherein when the end node address is an address of a node that has received the first reservation request packet, the reservation reply packet is broadcasted by referring to the first reservation request packet.

11. An apparatus for performing time synchronization and low power routing in a wireless sensor network, the apparatus comprising:

a synchronization packet generator to generate a first synchronization request command packet for informing about time synchronization information of the synchronization region, a second synchronization request command packet that has transmission time information of the first synchronization request command packet

a synchronization performing unit to perform time synchronization of the network based on a reception time of the first synchronization request command packet and a reception time of the second synchronization request command packet; and

a reservation packet generator to generate a reservation packet for reservation transfer of data in the network where the time synchronization is performed,

wherein the synchronization performing unit obtains a difference value between the reception time of the first synchronization request command packet and the reception time of the second synchronization request command packet and adding the difference value to the transmission timestamp value of the first synchronization request command packet.

12. The apparatus of claim 11,

wherein the synchronization packet generator further generates a synchronization reply packet corresponding to the second synchronization request command packet, and a synchronization reply packet for error synchronization restoration.

13. The apparatus of claim 11, wherein the reservation packet is any one of a reservation request packet for informing about a reservation transfer time of the data and a reservation reply packet corresponding to the reservation request packet.

14. The apparatus of claim 11, further comprising:

a transceiver to broadcast the reservation packet in a first time duration where all the nodes in the network are activated.

15. The apparatus of claim 11, wherein the transceiver transmits the data in a predetermined slot of a second time duration where all the nodes in the network are inactivated.