Method for reporting and accumulating data in a wireless communication network

• US 20060187866A1
• Filed: 12/20/2005
• Published: 08/24/2006
• Est. Priority Date: 12/20/2004
• Status: Active Grant

• Current Assignee: Honeywell International SARL (Honeywell International Inc.), Yokogawa USA, Inc. (Yokogawa Electric Corporation)
• Original Assignee: Sensicast Systems
• Inventors: Werb, Jay Philip, Berry, Victor A.
• Granted Patent: US 8,023,441 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: G01D 2204/45 Utility meters networked together within a single building
• CPC Class Codes: G01D 4/004 Remote reading of utility meters to a fixed location
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04W 40/32 for defining a routing cluster membership
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading

Abstract

A method and apparatus for coordinating communication in a wireless sensor network may include a plurality of nodes, such as routers, edge nodes, data accumulators and/or gateways. Time management functions, such as determining an elapsed time, may be controlled based on a detected temperature, e.g., a temperature detected at a node, and/or based on a detected clock skew between two or more clocks in two or more different devices. Accurate time management may allow for devices to more accurately coordinate communication instances, e.g., communication that occurs at periodic wake up times. A cluster head, such as a data accumulator, may be associated with a network after its initial formation and cause nodes in the network to alter their hierarchy in the network, thereby making the cluster headaccumulator a parent to nodes in the network. Nodes having a relatively lower hop count may have a higher battery capacity than nodes having a higher hop count.

Claims

1. A method for coordinating communication in a wireless sensor network, comprising:

associating a first node with a wireless sensor network including at least two nodes associated with each other in a parent/child relationship, the first node being associated with the wireless sensor network such that the first node functions as a parent or child to at least one other node; and

determining a wake up time for the first node to wake up and listen for or broadcast a signal regarding communication with a parent or child node, the wake up time being determined based on a detected temperature at the first node.

2. The method of claim 1, wherein the step of determining comprises:

determining a wake up time period;

determining an elapsed time;

comparing the elapsed time to the wake up time period; and

controlling the first node to wake up when the elapsed time equals the wake up time period.

3. The method of claim 2, wherein the elapsed time is adjusted based on the detected temperature.

4. The method of claim 3, wherein the elapsed time is determined based on a temperature-dependent frequency change formula of the form K1*(T−

K2)², where K1 and K2 are constants and T is the detected temperature.

5. The method of claim 1, wherein the wake up time is determined according to a schedule.

6. The method of claim 1, wherein the first node functions as a parent to a second node, and the first node is controlled to wake up and send a beacon based on a pseudorandom schedule.

7. The method of claim 6, wherein the second node wakes up to communicate with the first node according to the pseudorandom schedule.

8. The method of claim 7, wherein the second node determines a wake up time for the second node that is determined based on a detected temperature at the second node.

9. The method of claim 1, wherein the first node has an internal timer that is used to determine an elapsed time.

10. The method of claim 9, wherein elapsed time determined by the internal timer is adjusted based on the detected temperature.

11. The method of claim 1, wherein the step of determining comprises determining an elapsed time that is adjusted based on the detected temperature using a lookup table.

12. The method of claim 11, wherein values in the lookup table are generated based on empirical measurement of a plurality of different timers.

13. The method of claim 11, wherein a lookup table used to determine the elapsed time is selected based on an age of the node.

14. The method of claim 11, wherein a lookup table used to determine the elapsed time is selected based on whether the detected temperature is increasing, decreasing or constant.

15. The method of claim 1, wherein the wake up time is determined based on a clock skew determined between a clock in the first node and a clock in a parent or child node.

16. The method of claim 1, wherein the first node is a router and the second node is an edge node.

17. The method of claim 1, wherein the first and second nodes are routers.

18. A method for coordinating communication in a wireless sensor network, comprising:

associating a first node with a wireless sensor network including at least two nodes associated with each other in a parent/child relationship, the first node being associated with the wireless sensor network such that the first node functions as a parent or child to at least one other node; and

determining a wake up time for the first node to wake up and listen for a signal regarding communication with a second node that has a parent or child relationship with the first node, the wake up time being determined based on a determined clock skew between a clock in the first node and a clock in the second node.

19. The method of claim 18, wherein the clock skew is determined based on at least one comparison of a predicted signal transmission time with an actual signal transmission time for the second node.

20. The method of claim 18, wherein the first node is a child of the second node.

21. The method of claim 18, wherein the signal is a beacon and the second node emits a beacon on a defined schedule.

22. The method of claim 18, further comprising:

controlling the first node to wake up and listen for the signal based on the wake up time, the first node listening for the signal for a first time period; and

controlling the first node to wake up and listen for the signal at a subsequent wake up time for a second time period that is longer than the first time period if the first node does not detect the signal during the first time period.

23. The method of claim 22, wherein the first node is controlled to not listen for the signal at the subsequent wake up time if the second time period exceeds a threshold.

24. The method of claim 22, wherein the second time period is determined based on a lookup table.

25. The method of claim 24, wherein the first node is controlled to not listen for the signal at the subsequent wake up time if values in the lookup table are exhausted.

26. The method of claim 18, wherein the step of determining comprises:

determining a wake up time period to a next wake up time; and

adjusting the wake up time period based on the determined clock skew.

27. The method of claim 26, wherein the step of determining comprises:

determining an elapsed time;

comparing the elapsed time to a wake up time period; and

controlling the first node to wake up at the wake up time when the elapsed time equals the wake up time period.

28. The method of claim 18, wherein the wake up time is determined based on a detected temperature at the first node.

29. The method of claim 18, wherein the first node is an edge node, and the second node is a router.

30. A method for forming a wireless sensor network, comprising:

providing a plurality of nodes at a location, at least two of the nodes being adapted and positioned relative to each other to form a wireless sensor network;

beaconing, from a first one of the nodes, a signal that represents that the first node is not associated with a wireless sensor network and that the first node is adapted to function as a parent node;

associating a second one of the nodes with the first node such that the second node is a child of the first node and the first node is a parent of the second node, thereby forming, at least in part, a wireless sensor network;

associating a third node that is capable of functioning as a cluster head with the wireless sensor network, the third node being associated as a child of an association node in the wireless sensor network; and

commanding the association node to function as a child of the third node such that the third node functions as a parent to the association node.

31. The method of claim 30, wherein the wireless sensor network includes multiple routers arranged in a hierarchical parent/child relationship having at least three levels.

32. The method of claim 30, further comprising adjusting a hop count of nodes that have a parent relationship to the association node to be less than the hop count of the association node.

33. The method of claim 30, wherein the step of associating the cluster head comprises listening at the cluster head for beacons from nodes in the wireless sensor network prior to associating the cluster head as a child of the association node.

34. The method of claim 30, wherein the step of commanding comprises having the cluster head set hop counts for nodes having a child relationship to the cluster head.

35. The method of claim 30, wherein each of the plurality of nodes listen for a network beacon before the step of beaconing is performed or before associating with the wireless sensor network.

36. The method of claim 30, wherein the cluster head is a data accumulator or gateway.

37. A wireless sensor network comprising:

a cluster head;

a shadow cluster head; and

a plurality of nodes in communication with the cluster head and the shadow cluster head, the plurality of nodes including at least one router or at least one edge node;

wherein the cluster head and the shadow cluster head are adapted to receive communications from a same set of nodes, the cluster head and the shadow cluster head using different multipath profiles to communicate with nodes in radio range such that the shadow cluster head provides a redundant link from the set of nodes to the cluster head.

38. The network of claim 37, wherein the cluster head is a gateway or a data accumulator.

39. The network of claim 37, wherein the shadow cluster head serves as a backup for the cluster head.

40. A wireless sensor network comprising:

a data accumulator; and

a plurality of nodes in communication with the cluster head, the plurality of nodes including at least one router or at least one edge node that provide sensor data to the data accumulator;

wherein the data accumulator is adapted to communicate wirelessly with a mobile device to transmit the sensor data to the mobile device.

41. The network of claim 40, wherein the data accumulator sends NACK messages to nodes that do not report sensor data after passage of a timeout interval.

42. The network of claim 40, wherein the nodes and the data accumulator communicate wirelessly at a frequency of about 868 MHz, and the data accumulator and the mobile device communicate at a frequency of about 2.4 GHz.

43. The network of claim 40, wherein the data accumulator and the mobile device use a same radio MAC and PHY.

44. The network of claim 40, wherein the mobile device uses an IEEE 802.15.4 radio to communicate with the data accumulator.

45. A method for forming a wireless sensor network, comprising:

providing a plurality of routers at a location, the routers being configured and arranged to form a wireless sensor network in which routers have a hierarchical parent/child relationship; and

providing a gateway in communication with the wireless sensor network, wherein the gateway is adapted to send and receive signals for the wireless sensor network to at least one device outside of the wireless sensor network;

wherein routers in the wireless sensor network each have a hop count that indicates a number of routers through which communications from the router pass to the gateway, and wherein routers with a lower hop count have a larger battery capacity than routers with a higher hop count.