LOCATION SYSTEM FOR STREET LIGHT MONITORING

• US 20120059622A1
• Filed: 08/12/2011
• Published: 03/08/2012
• Est. Priority Date: 08/13/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: CACACE, VINCENZO, RIZZELLO, MARCO
• Granted Patent: US 8,731,866 B2
• Time in Patent Office: Days
• US Class Current: 702/150
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies
• CPC Class Codes: H04W 4/08 User group management
• CPC Class Codes: H05B 47/19 via wireless transmission

Abstract

A street light monitoring system has a small fraction of the street lights in the system being anchor nodes that are configured to detect and store their own actual fixed position, thereby acting as reference points. Further, the other street lights are referred to as blind nodes and do not have their actual fixed position but can derive their position using the coordinates of the anchor nodes and estimating their distance to them. The distance estimation for any blind node can be performed using a received signal strength indication (RSSI) measured at the respective blind node for small distances of up to a threshold value and a link quantization technique takes advantage of the typical placement of the street lights. Inferred distances between the street lights can be assigned to pre-determined categories of distances for a coarse estimation and further position adjustment to a closest possible “real” position.

Claims

1. A computer-implemented method for a street light monitoring system providing automated position estimation capabilities for all street lights being present in the street light system and thereby enabling efficient management of street lamps, the method comprising:

providing each street lamp of a network of numerous street lamps with a node controller and a ballast controller, the node controllers of the street lamps communicating to each other using wireless devices to build up a mesh network;

providing a number of cluster controllers, the cluster controllers controlling a subset of the street lamps in the network and being equipped with a transceiver, the transceiver communicating to the mesh network;

providing a cluster head, the cluster head controlling the network of street light and being coupled to the number of cluster controllers based on an external network;

providing a small fraction of the street lamps in the network and less than 30% of the street lamps in the network as anchor street lamps with their absolute and relative coordinates;

determining the average hop length in any minimum length path between two anchor street lamps;

determining for each street lamp in the network not being provided with their absolute and relative coordinates as blind street lamps the distance of the blind street lamp to the nearest anchor street lamps based on path loss evaluating received signal strength indication, RSSI, between the street lamps in the path to the nearest anchor street lamps, assigning the measured path loss values to pre-determined distance categories, assigning the distance categories to hop link values and multiplying the hop link values with the average hop length in the respective path;

inferring for each blind street lamp in the network a coarse position using multi-lateration based on the determined distances to the nearest anchor street lamps for that blind street lamp; and

adjusting the coarse position by selecting for each blind street lamp coarse position the closest possible real position and if no closest possible real position is present classify the blind street lamp as not positioned.

2. The method according to claim 1, further comprising for the case that no closest possible real position is present;

retrying the estimation; and

sending an error message for a manual position set-up request.

3. The method according to claim 2, wherein the number of distance categories is three, the first relating to two lamps being positioned on the same lamp post, the second being related to two lamps being positioned opposite to each other on either sides of a street, and the third being related to two lamps being positioned as neighbors on the same side of a street.

4. The method according to claim 3, wherein the first distance category is assigned to a hop link value of 0 hop links, the second distance category is assigned to a hop link value of 0.25 hop links, and the third distance category is assigned to a hop link value of 1 hop links.

5. The method according to claim 4, wherein the node controller is a RF-ZigBee device, the mesh network is a WPAN according to the ZigBee standard, and the transceiver is a radio frequency ZigBee transceiver linked to a wired or wireless modem.

6. The method according to claim 5, wherein the small fraction of street lamps is a number of 5-10% of all street light being present in the system.

7. A computer-readable medium having stored thereon computer-readable instructions that, when run on a computer, are configured for performing the steps of any of the methods of:

providing each street lamp of a network of numerous street lamps with a node controller and a ballast controller, the node controllers of the street lamps communicating to each other using wireless devices to build up a mesh network;

providing a number of cluster controllers, the cluster controllers controlling a subset of the street lamps in the network and being equipped with a transceiver, the transceiver communicating to the mesh network;

providing a cluster head, the cluster head controlling the network of street light and being coupled to the number of cluster controllers based on an external network;

providing a small fraction of the street lamps in the network and less than 30% of the street lamps in the network as anchor street lamps with their absolute and relative coordinates;

determining the average hop length in any minimum length path between two anchor street lamps;

determining for each street lamp in the network not being provided with their absolute and relative coordinates as blind street lamps the distance of the blind street lamp to the nearest anchor street lamps based on path loss evaluating received signal strength indication, RSSI, between the street lamps in the path to the nearest anchor street lamps, assigning the measured path loss values to pre-determined distance categories, assigning the distance categories to hop link values and multiplying the hop link values with the average hop length in the respective path;

inferring for each blind street lamp in the network a coarse position using multi-lateration based on the determined distances to the nearest anchor street lamps for that blind street lamp; and

adjusting the coarse position by selecting for each blind street lamp coarse position the closest possible real position and if no closest possible real position is present classify the blind street lamp as not positioned.

8. A computer-implemented street light monitoring system providing automated position estimation capabilities for all street lights being present in the street light system and thereby enabling efficient management of street lamps, the system comprising:

network of numerous street lamps, each street lamp equipped with a node controller and a ballast controller, the node controllers of the street lamps communicating to each other using wireless devices to build up a mesh network;

cluster controllers, each of the number of cluster controllers controlling a subset of the street lamps in the network and being equipped with a transceiver, the transceiver communicating to the mesh network;

cluster head, the cluster head controlling the network of street light and being coupled to the number of cluster controllers based on an external network;

anchor street lamps as a small fraction of the street lamps in the network and less than 30% of the street lamps in the network provided with their absolute and relative coordinates;

means for determining the average hop length in any minimum length path between two anchor street lamps;

blind street lamps as each street lamp in the network not being provided with their absolute and relative coordinates;

means for determining the distance of a blind street lamp to the nearest anchor street lamps based on path loss evaluating received signal strength indication, RSSI, between the street lamps in the path to the nearest anchor street lamps, assigning the measured path loss values to pre-determined distance categories, assigning the distance categories to hop link values and multiplying the hop link values with the average hop length in the respective path;

means for inferring for each blind street lamp in the network a coarse position using multi-lateration based on the determined distances to the nearest anchor street lamps for that blind street lamp; and

means for adjusting the coarse position by selecting for each blind street lamp coarse position the closest possible real position and if no closest possible real position is present classify the blind street lamp as not positioned.

9. The system according to claim 8, further comprising for the case that no closest possible real position is present;

retrying the estimation; and

sending an error message for a manual position set-up request.

10. The system according to claim 9, wherein the number of distance categories is three, the first relating to two lamps being positioned on the same lamp post, the second being related to two lamps being positioned opposite to each other on either sides of a street, and the third being related to two lamps being positioned as neighbors on the same side of a street.

11. The system according to claim 10, wherein the first distance category is assigned to a hop link value of 0 hop links, the second distance category is assigned to a hop link value of 0.25 hop links, and the third distance category is assigned to a hop link value of 1 hop links.

12. The system according to claim 11, wherein the node controller is a RF-ZigBee device, the mesh network is a WPAN according to the ZigBee standard, and the transceiver is a radio frequency ZigBee transceiver linked to a wireless or wired modem.

13. The system according to claim 12, wherein the small fraction of street lamps is a number of 5-10% of all street light being present in the system.

21. The system according to claim 11, wherein the node controller is a RF-ZigBee device, the mesh network is a WPAN according to the ZigBee standard, and the transceiver is a radio frequency ZigBee transceiver linked to a wireless or wired modem.

14. A method for providing position estimation for street lights in a street light system, the method comprising:

for a small fraction of the street lights in the street light system providing absolute and relative coordinates, with each such street being referred to as an anchor street light;

determining an average hop length in any minimum length path between two anchor street lights;

determining for each street light not being provided with absolute and relative coordinates, with each such street light being referred to as a blind street light, the distance of the blind street light to the nearest anchor street light based on a received signal strength indication between the street lights in the path to the nearest anchor street light;

assigning a measured path loss values to pre-determined distance categories;

assigning distance categories to hop link values and multiplying the hop link values with the average hop length in the respective path;

inferring for each blind street light a coarse position using multi-lateration based on the determined distances to the nearest anchor street lamps for that blind street lamp; and

adjusting the coarse position of each blind street light by selecting a nearest possible real position.

15. The method of claim 14 wherein if no closest possible real position is present, classifying the blind street lamp as being not positioned.

16. The method of claim 14 wherein there are three distance categories, the first relating to two street lights being positioned on the same lamp post, the second being related to two street lights being positioned opposite to each other on either sides of a street, and the third being related to two street lights being positioned as neighbors on the same side of a street.

17. The method of claim 16 wherein the first distance category is assigned a hop link value of 0 hop links, the second distance category is assigned a hop link value of 0.25 hop links, and the third distance category is assigned a hop link value of 1 hop links.

18. The method of claim 14 wherein the small fraction of street lamps is between 5-10% of all street lights in the system.

19. A street light monitoring system, comprising:

a network of street lamps, each street lamp including a node controller and the node controllers of the street lamps communicating with each to form a mesh network;

a plurality of cluster controllers, each cluster controller communicating through the mesh network to control a subset of the street lamps in the network;

a cluster head operable to control the network of street lamps and being coupled to the cluster controllers through an external network;

a plurality of anchor street lamps wherein the plurality is a small fraction of the total number of street lamps in the network;

a plurality of blind street lamps corresponding to the remaining street lamps in the network;

control circuitry operable to determine the position of the blind street lamps through link quantization, multi-hop distance estimation, and street lamp position adjustment.

20. The street light monitoring system of claim 19 wherein the control circuitry is further operable to,

determine the average hop length in any minimum length path between two anchor street lamps;

determine the distance of a respective blind street lamp to the nearest anchor street lamps based on a path loss metric between the street lamps in the path to the nearest anchor street lamps,

assign determined path loss values to pre-determined distance categories,

assigning hop link values to the pre-determined distance categories,

multiply the hop link values with the average hop length in the respective path,

determine for each blind street lamp in the network a coarse position using multi-lateration based on the determined distances to the nearest anchor street lamps for that blind street lamp,

adjust the coarse position by selecting for each blind street lamp coarse position the closest possible real position, and if no closest possible real position is present classify the blind street lamp as being not positioned.