Network system, radio communication device, radio communication method, and computer program for the same

• US 20060176842A1
• Filed: 11/30/2005
• Published: 08/10/2006
• Est. Priority Date: 12/02/2004
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tamura, Yosuke
• Granted Patent: US 7,486,633 B2
• Time in Patent Office: Days
• US Class Current: 370/315
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: H04W 84/00 Network topologies

Abstract

A network system, radio communication device, radio communication method, and computer program for same are provided. The present invention enables formation of a network topology with sensor nodes each having a traveling function and operating in the self-directive and dispersive state without using positional information. Each sensor nodes periodically transmits a HELLO message to neighboring nodes to exchange information therewith. In an area where the node density is high, the nodes are set in the Expand state and in the Bridge state. A node in the Expand state shifts to the Stay state when the node can be connected to only one neighboring node to becomes a component of the topology. A node in the Bridge state shifts to the Stay state together with neighboring nodes each having hidden terminals not less than a prespecified number to become a component of the topology.

Claims

1. A network system for forming a network topology with a plurality of nodes each having a radio communication function and a traveling function and operating in a self-directive and dispersive state,

wherein each node has first and second states in which the node travels with said traveling function and searches for information for connectivity with neighboring nodes and a third state in which travel with said traveling function is stopped, and a node in the first state shifts to said third state when a first condition is satisfied and a node in the second state shifts to the third state when a second condition different from said first condition is satisfied, and

each node finally shifts to said third state dynamically switching between said first state and said second state to form a network topology.

2. The network system according to claim 1,

wherein said node has a sensor, and said first state is an Expand state in which the node travels and searches for a position where connectivity with neighboring nodes is obtained to expand a network topology;

said second state is a Bridge state where the node travels and searches for a position where connectivity with neighboring nodes is obtained to connect independent local topologies; and

said third state is a Stay state where the node stops at the current position to become a component of the network topology.

3. The network system according to claim 2,

wherein a node in the Expand state shifts to the Stay state under the first condition under which the node can be connected to an neighboring node in the Stay state.

4. The network system according to claim 2,

wherein a node in the Bridge state shifts to the Stay state under a second condition where the node can be connected to two or more independent nodes not neighboring to each other and not having any common neighboring node.

5. The network system according to claim 2,

wherein all nodes are in the Expand state in the initial stage of a network topology and nodes in the Bridge state are generated according to prespecified probability when the node density is over a prespecified value.

6. The network system according to claim 2,

wherein each node transmits a first signal including a list of nodes neighboring to the node at a prespecified timing, and recognizes connectable neighboring node or a node density by receiving the first signal from the neighboring nodes.

7. The network system according to claims 3,

wherein a node in the Expand state transmits a second signal to said connectable neighboring nodes in the Stay state and shifts to the Stay state upon reception of a third signal.

8. The network system according to claim 4,

wherein a node in the Bridge state transmits a second signal to said nodes independent from each other and shifts to the Stay state upon reception of a third signal.

9. The network system according to claim 7 or claim 8,

wherein a node having received a second signal cancels transition to the Stay state when the third signal is not received within a prespecified period of time, and again transmits a fourth signal.

10. The network system according to claim 9,

wherein a node in a state other than the Stay state shifts to the Stay state when the second signal is received, and cancels transition to the Stay state when the fourth signal is received.

11. The network system according to claim 2,

wherein each node acquires connectivity to neighboring nodes from which electric wave with proper amplitude is received by said radio communication function.

12. The network system according to claim 11,

wherein each node recognizes, as improper,. neighboring nodes from which electric wave with amplitude higher than a prespecified value and neighboring node from which electric wave with amplitude lower than a prespecified node and avoids connection to the nodes.

13. A radio communication device operating as a sensor node in a sensor network and comprising:

a sensor for acquiring desired information at a current position;

a radio communication function unit for executing communication with neighboring sensor nodes;

a traveling function unit for moving a position of said device; and

a control unit for processing information acquired by said sensor and controlling operations of each of said function units,

wherein said control unit dynamically switches an operating state of said sensor node, based on information on connectivity to neighboring nodes acquired by said radio communication function unit, between first and second states in each of which said radio communication device travels and searches for information on connectivity to neighboring nodes, shifts the operating state of said sensor node to a third state in which traveling with said traveling function unit is stopped when a first condition is satisfied in said first state, and further shifts to said third state when a second condition different from said first condition is satisfied in said second state.

14. The radio communication device according to claim 13,

wherein said first state is an Expand state in which each node travels and searches for a position at which connectivity to neighboring node is obtained for expanding a network topology;

said second state is an Bridge state in which each node travels and searches for a position at which connectivity with neighboring nodes is obtained for connecting independent network topologies to each other; and

said third state is a Stay state in which each node stops at a current position and becomes a component of a network topology.

15. The radio communication device according to claim 14,

wherein said control unit shifts an operating state of each node in the Expand state to the Stay state under a first condition under which the node can be connected to one neighboring node in the Stay state.

16. The radio communication device according to claim 14,

wherein said control unit shifts an operating state of each node in the Bridge state to the Stay state under a second condition under which the node can be connected to two or mode independent nodes not neighboring to each other and not having any common neighboring node.

17. The radio communication device according to claim 14,

wherein said control unit sets an operating state of each node to the Expand state in the initial state, and shifts the operating state of each node to the Bridge state according to prespecified probability when it is detected based on information concerning connectivity with neighboring nodes acquired by said radio communication function unit that the node density is over a prespecified value.

18. The radio communication device according to claim 14,

wherein said control unit generates a first signal including a list of nodes neighboring to the unit in the current state and transmits the first signal at a prespecified timing from said radio communication function unit;

and

further said control unit recognizes connectable neighboring node or the node density by processing the first signal received by said radio communication function section.

19. The radio communication device according to claim 15,

wherein said control unit transmits in the Expand state a second signal to said connectable neighboring nodes in the Stay state and shifts an operating state of each connectable neighboring nodes to the Stay state upon reception of a third signal.

20. The radio communication device according to claim 16,

wherein said control section transmits in the Bridge state a second signal to each of the nodes independent from each other and shifts an operating state of each of the nodes to the Stay state upon reception of a third signal.

21. The radio communication device according to claim 19 or claim 20,

wherein said control section cancels shift to the Stay state when the third signal is not received within a prespecified period of time after transmission of the second signal, and again transmits a fourth signal.

22. The radio communication device according to claim 21,

wherein said control unit shifts, in a state other than the Stay state, an operating state of each node to the Stay state upon reception of the second signal, and cancels shifts to the Stay state upon reception of the fourth signal.

23. The radio communication unit according to claim 14,

wherein said control section acquires connectivity with neighboring node from which electric wave with proper amplitude can be obtained by said radio communication function unit.

24. The radio communication device according to claim 23,

wherein said control section recognizes, as improper, neighboring nodes from which electric wave with amplitude higher than a prespecified value by said radio communication function unit and neighboring nodes from which electric wave with amplitude lower than the prespecified value, and avoids connectivity to the nodes.

25. A radio communication method enabling a radio communication device having a sensor, a radio communication function and a traveling function to operate as a sensor node in a sensor network, said method comprising the steps of:

dynamically switching, based on information on connectivity to neighboring nodes acquired by said radio communication function, between the first and second states in each of which each node travels with said traveling function and searches for information on connectivity with neighboring node;

shifting from the first state to the third state in which traveling with said traveling function is stopped when a first condition is satisfied; and

shifting from the second state to the third state in which when the second state different from the first condition is satisfied.

26. A computer program described with a computer-readable format and enabling a radio communication device having a sensor, a radio communication function and a traveling function to operate as a sensor node in a sensor network, said computer program enabling execution of the radio communication method comprising the steps of:

dynamically switching, based on information on connectivity to neighboring nodes acquired by said radio communication function, between the first and second states in each of which each node travels with said traveling function and searches for information on connectivity with neighboring node;

shifting from the first state to the third state in which traveling with said traveling function is stopped when a first condition is satisfied; and

shifting from the second state to the third state in which when the second state different from the first condition is satisfied.