Method for Estimating and Signalling the Density of Mobile Nodes in a Road Network

• US 20090323549A1
• Filed: 02/01/2008
• Published: 12/31/2009
• Est. Priority Date: 02/09/2007
• Status: Active Grant

• Current Assignee: Orange S.A.
• Original Assignee: Orange S.A.
• Inventors: Senouci, Sidi-Mohammed, Mohamed-Rasheed, Tinku, Jerbi, Moez
• Granted Patent: US 8,208,382 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: G08G 1/0104 Measuring and analyzing of parameters relative to traffic conditions
• CPC Class Codes: G08G 1/065 by counting the vehicles in a section of the road or in a parking area, i.e. comparing incoming count with outgoing count
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 67/04 specially adapted for terminals or networks with limited capabilities; specially adapted for terminal portability
• CPC Class Codes: H04L 67/52 specially adapted for the location of the user terminal
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 40/20 based on geographic position or location
• CPC Class Codes: H04W 40/32 for defining a routing cluster membership
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A method and an associated device for estimating the density of mobile node traffic in an ad-hoc network on the roads of a predetermined geographical network in which mobile nodes move. Each road is divided into coverage cells. For each cell, a principal mobile node located at the center of the cell counts the number of nodes in the cell, and inserts this number into a cell density packet (CDP) transmitted from cell to cell during a first stage.

Claims

1. A method of estimating the density of mobile nodes of an ad hoc network in which mobile nodes move along roads of a particular geographical network, at least some mobile nodes being able to locate themselves in the geographical network and adapted to maintain an up-to-date neighbor table including information relating to the positions of their neighbor nodes, wherein the density of the mobile nodes on a road is determined by the steps of:

said road being subdivided into coverage cells, an intracellular counting step executed at one of said coverage cells during which a mobile node located in a predetermined central area of said coverage cell, called a principal node, determines from its neighbor table local traffic density data; and

an aggregation step, during which said principal node inserts said local traffic density data so determined into a cell density packet.

2. The method according to claim 1, wherein, during said aggregation step, said principal node inserts into said cell density packet the number of mobile nodes of its cell and transmits said cell density packet to a principal node of a neighbor coverage cell.

3. The method according to claim 2, wherein, said roads forming between them intersections:

the cell density packet is generated by a generator mobile node that has traveled the whole of the road connecting a source intersection to a designation intersection and is located near the destination intersection; and

the cell density packet is transmitted cell by cell from the cell adjacent the destination intersection to the source intersection.

4. The method according to claim 3, wherein the generator node is a mobile node that, as a principal node, has previously modified a cell density packet.

5. The method according to claim 1, wherein said coverage cells are predefined on a digital map representing the geographical network in association with anchor points located at the centers of said cells and the coordinates of which are stored, and during the aggregation step the cell density packet is transmitted from cell to cell, according to the anchor points defined on the map representing the geographical network.

6. The method according to claim 3, wherein the generator node calculates the geographical coordinates of anchor points corresponding to the centers of said cells from a length parameter of the road and a transmission range parameter of a mobile node, and during the aggregation step the cell density packet is transmitted from cell to cell, according to the anchor points calculated by said generator mode.

7. The method according to claim 5, further comprising:

a step of analyzing the traffic data contained in the cell density packet received at an intersection, the analysis including calculating at least one parameter characterizing the traffic density on the road selected from;

the local mobile node density;

the mean mobile node density;

the variance of the local mobile node density.

8. The method according to claim 2, wherein said method further includes a signaling stage including:

a generation step in which a mobile node located at an intersection generates a signaling packet from a cell density packet relating to a road if the traffic density on said road is above a predetermined threshold; and

a step of transmitting said signaling packet to the principal nodes of said cell, a principal node broadcasting the signaling packet to its neighbor nodes.

9. The method according to claim 8, wherein the signaling packet is transmitted from cell to cell in an area defined by a predetermined number of intersections to be crossed.

10. A method of routing data packets in an ad hoc network including mobile nodes moving along roads of a particular geographical network, said method including a step of establishing a routing path to at least some of the mobile nodes for the transmission of packets, said routing path being established as a function of mobile node densities on the road determined by the estimation method according to claim 1.

12. A computer program including instructions for executing the steps of the method according to claim 1 when said program is executed by a computer.

13. A computer-readable storage medium storing a computer program according to claim 12.

11. A wireless communications terminal adapted to form a mobile node of an ad hoc network including mobile nodes moving on roads of a particular geographical network, said terminal being associated with means adapted to determine the location of said terminal in the geographical network and means for maintaining an up-to-date neighbor table including information relating to the positions of its neighbor nodes, wherein said terminal further includes:

intracellular counting means, for determining from its neighbor table local traffic density data at a coverage cell of a road divided into a plurality of said coverage cells, said intracellular counting means being used when the terminal is located in a predetermined central area of said coverage cell;

writing means for inserting said local traffic density data into a cell density packet; and

means for receiving and transmitting said cell density packet.

14. A signal adapted to be transmitted in an ad hoe network in which mobile nodes move along roads of a particular geographical network, at least some mobile nodes being able to locate themselves in the geographical network and adapted to maintain an up-to-date neighbor table including information relating to the positions of their neighbor nodes, wherein said signal transports a cell density packet including:

an identifier of a road associated with the cell density packet;

an identifier of coverage cells belonging to said road;

coordinates of anchor points each associated with a coverage cell; and

at least one field for storing traffic density data local to at least one of said coverage cells.