System and method for detecting node mobility based on network topology changes in a wireless communication network

1. A method for determining mobility of a first node in an area of an ad hoc network, comprising:

generating a fixed neighbor node table comprising second nodes in the area which are not mobile;

monitoring changes between the first node and the second nodes; and

determining if the first node is mobile based on the changes,

wherein generating a fixed neighbor node table comprising the second nodes in the area which are not mobile, comprises:

measunng a metric of information received from other nodes in the area;

using the metric to determine neighbor nodes;

determining whether the neighbor nodes are fixed; and

designating the ones of the neighbor nodes determined to be fixed as second nodes and including the second nodes in the fixed neighbor node table.

2. A method for determining mobility of a first node in an area of an ad hoc network, comprising:

generating a fixed neighbor node table comprising second nodes in the area which are not mobile;

monitoring changes between the first node and the second nodes; and

determining if the first node is mobile based on the changes,

wherein monitoring changes between the first node and the second nodes, comprises:

periodically transmitting a message from each of the second nodes;

determining contact times between the first node and each of the second nodes by determining if the messages are being received at the first node from the second nodes;

averaging the contact times to determine an average contact time; and

monitoring changes in the average contact time between the first node and the second nodes.

3. A method according to claim 2 , wherein determining contact times between the first node and each of the second nodes, comprises:

maintaining an entry time for each of the second nodes, wherein the entry time associated with each of the second nodes comprises a first time when the first node first receives a message having signal quality above a threshold from that second node;

maintaining an exit time for at least some of the second nodes, wherein the exit time associated with those second nodes comprises a second time when the first node stops receiving messages, having signal quality above the threshold, from those second nodes; and

determining a contact time associated with the at least some of the second nodes, the contact time comprising the difference between the exit time and the entry time.

4. A method according to claim 3 , wherein the contact time represents the amount of time the first node was in contact with each of the second nodes that the first node stops receiving messages from having signal quality above the threshold, and wherein the average contact time indicates movement of the first node.

5. A method according to claim 3 , wherein determining if the first node is mobile based on the changes, comprises:

determining that the first node is in a mobile state if the average contact time is less than a threshold.

6. A method according to claim 5 , after it has been determined that the first node is in the mobile state, further comprising:

determining that the first node is in a stationary state if the first number is less than the threshold value,

wherein the first node must wait a period of time before changing its status to a stationary state.

7. A method according to claim 3 , wherein determining if the first node is mobile based on the changes, comprises:

determining that the first node is in a stationary state if the average contact time is greater than or equal to a threshold.

8. A method according to claim 7 , after it has been determined that the first node is in the stationary state, fUrther comprising:

determining that the first node is in a mobile state if the first number is greater than or equal to the threshold value,

wherein the first node must wait a period of time before changing its status to a mobile state.

9. A method for assessing the degree of mobility of a particular node in a mobile ad-hoc network, comprising:

monitoring and recording in a neighbor table of the particular node each fixed neighbor node in an operable range of the particular node;

monitoring and recording for each fixed neighbor node the entry time to and exit time from the operable range of the particular node; and

quantifying the average contact period for the fixed neighbor nodes, wherein an average contact period greater than a threshold duration indicates a lack of mobility of the particular node.

10. A first node configured to determine whether it is mobile in an ad hoc network, comprising:

a processor configured to generate a fixed neighbor node table comprising second nodes which are not mobile, monitor changes in contact times between the first node and the second nodes, and determine if the first node is mobile based on the changes in the contact times between the first node and the second nodes,

wherein the processor is configured to measure a metric of information received from other nodes in an area of the first node, use the metric to determine neighbor nodes, determine whether the neighbor nodes are fixed, designate the ones of the neighbor nodes determined to be fixed as second nodes, and include the second nodes in the fixed neighbor node table.

11. A first node configured to determine whether it is mobile in an ad hoc network, comprising:

a processor configured to generate a fixed neighbor node table comprising second nodes which are not mobile, monitor changes in contact times between the first node and the second nodes, and determine if the first node is mobile based on the changes in the contact times between the first node and the second nodes; and

a receiver configured to periodically receive a message from each of the second nodes, and

wherein the processor is further configured to determine contact times between the first node and each of the second nodes by determining if the messages are being received at the first node from the second nodes, average the contact times to determine an average contact time, and monitor changes in the average contact time between the first node and the second nodes.

12. A first node according to claim 11 , further comprising:

a memory configured to store an entry time for each of the second nodes and to store an exit time for at least some of the second nodes, wherein the entry time associated with each of the second nodes comprises a first time when the first node first receives a message having signal quality above a threshold from that second node, and wherein the exit time associated with those second nodes comprises a second time when the first node stops receiving messages, having signal quality above the threshold, from those second nodes, and

wherein the processor is configured to determine a contact time associated with the at least some of the second nodes, the contact time comprising the difference between the exit time and the entry time.

13. A first node according to claim 12 , wherein the contact time represents the amount of time the first node was in contact with each of the second nodes that the first node stops receiving messages from having signal quality above the threshold, and wherein the average contact time indicates movement of the first node.

14. A first node according to claim 12 , wherein the processor is configured to determine that the first node is in a mobile state if the average contact time is less than a threshold.

15. A first node according to claim 14 , wherein the processor is configured to wait a period of time after the processor determines that the first node is in the mobile state before changing its mobility status to a stationary state.

16. A first node according to claim 12 , wherein the processor is configured to determine that the first node is in a stationary state if the average contact time is greater than or equal to a threshold.

17. A first node according to claim 16 , wherein the processor is configured to wait a period of time after the processor determines that the first node is in the stationary state before changing its mobility status to a mobile state.

18. A first node configured to assess its mobility status in an ad hoc network, the first node comprising:

a processor configured to determine which nodes in an operable range of the first node are fixed neighbor nodes, an entry time for each fixed neighbor node, and an exit time for each fixed neighbor node;

a memory configured to store the fixed neighbor nodes in a fixed neighbor node table, the entry time for each fixed neighbor node, and the exit time for each fixed neighbor node,

wherein the processor is configured to determine a contact period between the first node and each of the fixed neighbor nodes, and to determine an average of the contact periods,

wherein the processor determines that the first node is stationary if the average is greater than or equal to a threshold duration.