METHOD AND APPARATUS FOR WIRELESS COMMUNICATION IN A MESH NETWORK WITH TRACKABLE RANDOMIZED SCHEDULE

• US 20080037431A1
• Filed: 07/12/2007
• Published: 02/14/2008
• Est. Priority Date: 07/17/2003
• Status: Abandoned Application

• Current Assignee: Sensicast Systems
• Original Assignee: Sensicast Systems
• Inventors: Berry, Victor, Werb, Jay, Weiss, Howard, Lamb, C.
• Application Number:
  US11/776,960
• Publication Number:
  US 20080037431A1
• Time in Patent Office: Days
• US Class Current: 370/241
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/16 the keys or algorithms being changed during operation
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04W 12/069 using certificates or pre-shared keys
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and apparatus for communication in a wireless sensor network. In one embodiment, one or more routers in a network may be available for communication with one or more star nodes at a randomized time and/or frequency. A connectivity assessment, which may be performed at several different frequencies and/or times, may be performed to evaluate the quality of communications between devices in the network. Primary and secondary communication relationships may be formed between devices to provide for system redundancy. One or more proxies may be maintained where each proxy includes a status of one or more devices in the network, e.g., one or more star nodes or routers. Proxies may be used to handle information requests and/or status change requests, e.g., a proxy may be requested to change a communication relationship between devices in the network and may generate command signals to cause the corresponding devices to make the change.

Claims

1. A wireless mesh network, comprising:

a plurality of star nodes constructed and arranged to transmit and receive wireless signals; and

a plurality of routers each constructed and arranged to transmit and receive wireless signals for communication with at least one star node, and constructed and arranged to transmit and receive wireless signals for communication within at least one other device in the wireless sensor network;

wherein the plurality of star nodes communicates with at least one router using a plurality of different frequencies, and at least one router is available for communication with at least one star node based on a randomized frequency schedule and/or randomized timing schedule that can be forecasted and tracked by other nodes in the network.

2. The network of claim 1, wherein the at least one router is available for communication based on a randomized timing schedule that is determined using a fixed time interval plus or minus a randomized dither.

3. The network of claim 2, wherein the randomized dither is determined based on a congruential generator.

4. The network of claim 2, wherein the randomized dither is determined based on a table that is shared with other nodes in the network and/or calculated using shared parameters for a shared algorithm.

5. The network of claim 1, wherein a time period during which the at least one router is available for communication at a given frequency is variable in length based on a communication load for the frequency.

6. The network of claim 1, wherein devices in the network communication with the at least one router by preferentially using one or more frequencies at which the devices successfully communicated with the router in the past.

7. The network of claim 1, wherein carrier sense multiple access with collision avoidance (CSMA-CA) is used for communication with the at least one router.

8. The network of claim 7, wherein slotted CSMA-CA is used.

9. The network of claim 7, wherein unslotted CSMA-CA is used.

10. The network of claim 1, wherein each of the plurality of routers is available for communication based on a time and frequency schedule that is independent of a schedule for other routers.

11. The network of claim 10, wherein each schedule defines a randomized time and a randomized frequency according to which the corresponding router is available for communication.

12. The network of claim 1, wherein each of the plurality of routers is available for communication based on a schedule that is coordinated with all other routers.

13. The network of claim 15 wherein each of the routers transmits and receives signals for communication with at least one other router using a plurality of frequencies.

14. The network of claim 13, wherein the plurality of the routers are each available for communication with at least one other router for a period that begins at least one of at a randomized time or at a randomized frequency.

15. The network of claim 1, further comprising at least one gateway, and a host computer,

wherein a plurality of routers communicate with the host computer via at least one gateway.

16. The network of claim 15, wherein at least one of the routers communicates with the host computer via at least one other router.

17. The network of claim 1, wherein at least one star node has a sleep cycle that is controlled such that the at least one star node wakes up for communication with a router at a time that approximately coincides with a period when the router is available for communication.

18. The network of claim 1, wherein each router transmits a beacon before at least one period during which the router is available for communication with at least one star node.

19. The network of claim 18, wherein the beacon includes one or more of a PHY header, a MAC header, a network identification number, a session identifier, a router identifier, a current time, a last time that network parameters changed, information for determining a dither, information for determining a currently active communication channel and a list of children with store-and-forward messages in a queue.

20. The network of claim 1, wherein at least one router changes a length of a period during which the router is available for communication with at least one star node based on an amount of network traffic.

21. The network of claim 1, wherein at least one router goes into a low-power sleep mode between multiple periods during with the router is available for communication with at least one star node.

22. The network of claim 1, wherein at least one star node retransmits a signal on a second frequency upon failure to receive a MAC-level acknowledgement after sending the signal on a first frequency.

23. The network of claim 1, wherein a star node resynchronizes its clock with that of a router by acknowledging a beacon sent by the router.

24. The network of claim 1, wherein a star node resynchronizes its clock with that of a router by listening for a beacon sent by the router around a scheduled time when the router is to send the beacon.

25. The network of claim 1, wherein a star node or router is adapted to calibrate its clock based on detecting clock drift of its clock in relation to another clock source.

26. The network of claim 25, wherein a star node or router detects clock drift between two or more time synchronization points with a parent node.