Broadcast-only distributed wireless network

• US 8,159,938 B2
• Filed: 06/23/2008
• Issued: 04/17/2012
• Est. Priority Date: 06/23/2008
• Status: Active Grant

• Current Assignee: Chess Wise BV
• Original Assignee: C.H.S.S. Embedded Technology B.V.
• Inventors: Van Der Wateren, Frits
• Primary Examiner(s): LEVITAN, DMITRY
• Application Number:
  US12/215,040
• Publication Number:
  US 20090316679A1
• Time in Patent Office: 1,394 Days
• Field of Search: 370/229, 370/230, 370/310, 370/400, 370431-432, 370442-445, 709223-229, 709/248
• US Class Current: 370/229
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 72/30 Resource management for broadcast services
• CPC Class Codes: H04W 72/535 based on resource usage policies

Abstract

Communication in a broadcast-only distributed wireless network of nodes is provided. Each of the nodes of the network uses a repeated communication frame with an idle period and a TDMA schedule for active communication. The active TDMA schedule of at least some of the nodes in the network are aligned and synchronized. The distributed network does not require a central node for coordinating the TDMA schedules of another node or for synchronizing the communication frames. TDMA slots of the TDMA schedule are used for broadcasting and receiving messages. A node broadcasts a message without the use of an address of the receiving node. Communication frames having dynamic properties, such as communication frame length and start time, TDMA schedule position and length, and idle period position and length, are provided. Distributed functions for nodes to search for and synchronize with other nodes are also provided.

Claims

1. A communication system in a distributed wireless network, said system comprising:

(a) a plurality of wireless nodes, wherein at least some of said plurality of nodes are communicatively connected, wherein each of said nodes uses repeated communication frames for said communication, wherein each of said communication frames comprises;

(i) a first period which is a time division multiple access (TDMA) schedule for active communication, wherein said TDMA schedule comprises a plurality of TDMA slots; and

(ii) a second period, wherein little or no activity occurs in said second period;

(b) a broadcast function for allowing each of said plurality of nodes to broadcast a message, wherein one of said TDMA slots is used to broadcast said message, and wherein said message broadcasted by each of said nodes does not comprise an address of another of said nodes and includes an identifier of the TDMA slot used to broadcast the message; and

(c) a listen function for allowing each of said plurality of nodes to listen for said broadcasted messages, wherein one or more of said TDMA slots is used to listen for one or more of said broadcasted messages, and wherein said listen function allows a listening node to receive one or more of said broadcasted messages;

wherein a start time of said repeated communication frame for one of said nodes is determined by;

(i) receiving one or more of said broadcasted messages;

(ii) calculating a time shift, wherein said time shift is calculated based at least partially on said TDMA slot identifiers of each of said received messages; and

(iii) determining said start time of said repeated communication frame of said receiving node based on said calculated time shift.

2. The system as set forth in claim 1, wherein none of said plurality of nodes coordinates said TDMA schedule and said TDMA slots of another of said nodes.

3. The system as set forth in claim 1, further comprising an ignore function for allowing each of said plurality of nodes to ignore said broadcasted messages.

4. The system as set forth in claim 1, wherein said communication frame of each of said nodes has a variable length.

5. The system as set forth in claim 1, wherein said communication frame of each of said nodes has a fixed length, and wherein said fixed length of said communication frame ranges between about 0.5 seconds to about 5 seconds.

6. The system as set forth in claim 1, wherein said second period is longer than said TDMA schedule.

7. The system as set forth in claim 1, wherein the length of said TDMA schedule for a selected one of said nodes can be changed by the selected node, and wherein the length of said TDMA schedule is changed based on a number of neighboring nodes for the selected node.

8. The system as set forth in claim 1, wherein each of said TDMA slots of each of said nodes is allocated by the same of said nodes to be a listen slot, a transmit slot, or an idle slot.

9. The system as set forth in claim 8, wherein said allocation of each of said TDMA slots is dynamic, wherein each of said nodes can have one or more neighboring nodes, and wherein said dynamic allocation of each of said TDMA slots of a selected one of said nodes is based on a usage of said TDMA slots by said neighboring nodes of the selected node.

10. The system as set forth in claim 1, wherein each of said TDMA slots has a width, wherein each of said broadcasted messages has a duration, and wherein said width of each of said TDMA slots is longer than said duration of each of said broadcasted messages.

11. The system as set forth in claim 1, wherein said plurality of nodes comprises one or more sensor devices, one or more actuator devices, or any combination thereof.

12. A method for distributed wireless communication between a plurality of nodes, said method comprising:

(a) partitioning a repeated communication frame of each of said plurality of nodes into a first period which is a time division multiple access (TDMA) schedule and a second period wherein little or no activity occurs, wherein said TDMA schedule is for active communication, and wherein said TDMA schedule comprises a plurality of TDMA slots;

(b) providing a broadcast function for allowing each of said plurality of nodes to broadcast a message, wherein one of said TDMA slots is used to broadcast said message, and wherein said message broadcasted by each of said nodes does not comprise an address of another of said nodes and includes an identifier of the TDMA slot used to broadcast the message;

(c) providing a listen function for allowing each of said plurality of nodes to listen for said broadcasted messages, wherein one or more of said TDMA slots is used to listen for one or more of said broadcasted messages, and wherein said listen function allows a listening node to receive one or more of said broadcasted messages; and

(d) determining a start time of said repeated communication frame for one of said nodes, said start time determining comprising;

(i) receiving one or more of said broadcasted messages;

(ii) calculating a time shift, wherein said time shift is calculated based at least partially on said TDMA slot identifiers of each of said received messages; and

(iii) determining said start time of said repeated communication frame of said receiving node based on said calculated time shift.

13. The method as set forth in claim 12, wherein said method comprises a media access control (MAC) protocol.

14. The method as set forth in claim 12, further comprising dynamically determining the length of said TDMA schedule for a selected one of said nodes, wherein the length of said TDMA schedule is determined based on a number of neighboring nodes of the selected node.

15. The method as set forth in claim 12, further comprising dynamically allocating said TDMA slots of each of said nodes, wherein each of said TDMA slots of each of said nodes is allocated to be a listen slot, a transmit slot, or an idle slot.

16. The method as set forth in claim 15, further comprising measuring a usage of said TDMA slots for one of said nodes, wherein said dynamic allocation of said TDMA slots of the same of said nodes is based on said measured usage.

17. The method as set forth in claim 12, wherein each of said TDMA slots has a width, wherein each of said broadcasted messages has a duration, and wherein said width of each of said TDMA slots is longer than said duration of each of said broadcasted messages.

18. The method as set forth in claim 12, wherein said start time determining further comprises measuring an arrival time for each of said received messages, and wherein said time shift is calculated based at least partially on said arrival time of each of said received messages.

19. The method as set forth in claim 12, further comprising providing a search function for a selected one of said nodes, wherein the selected node activates said search function if the selected node has not received any of said broadcasted messages during a predetermined number of said communication frames, and wherein said search function is activated until the selected node receives one of said messages broadcasted by another of said nodes.

20. The method as set forth in claim 19, wherein said search function allows each of said nodes to change one or more properties of said communication frame of the same of said nodes, said one or more properties comprise a start time of said communication frame, the length of said communication frame, the position of said TDMA schedule in said communication frame, the length of said TDMA schedule, the position of said second period in said communication frame, the length of said second period, or any combination thereof.

21. The method as set forth in claim 12, further comprising providing a join function for each of said nodes, wherein said join function allows each of said nodes to transmit a join message, wherein said join message is transmitted from a random position in said second period of said communication frame, and wherein said join message comprises said random position.

22. The method as set forth in claim 21, further comprising one of said nodes:

(i) receiving said join message transmitted by another of said nodes; and

(ii) shifting said TDMA schedule of said node receiving said join message, wherein said shifting approximately synchronizes said communication frame of said node receiving said join message with said communication frame of said node transmitting said join message.

23. A method of synchronizing nodes in a distributed wireless communication network of a plurality of nodes, said method comprising:

(a) providing a repeated communication frame for each of said plurality of nodes, wherein said communication frame comprises a first period which is a time division multiple access (TDMA) schedule and a second period wherein little or no activity occurs, and wherein said TDMA schedule is for active communication;

(b) broadcasting a join message, wherein said join message is broadcasted by one of said plurality of nodes, wherein said join message is broadcasted from a random position in said second period of said communication frame of said broadcasting node, and wherein said join message comprises said random position;

(c) receiving said join message, wherein said join message is received by another of said plurality of nodes, and wherein said join message is received within said TDMA schedule of said receiving node; and

(d) shifting the position of said TDMA schedule in said communication frame of said receiving node, wherein said shifting is based on said random position of said received join message, and wherein said shifting approximately synchronizes said communication frame of said receiving node with said communication frame of said broadcasting node.