Method and apparatus for synchronizing a node within an AD-HOC communication system

• US 20070086424A1
• Filed: 10/13/2005
• Published: 04/19/2007
• Est. Priority Date: 10/13/2005
• Status: Active Grant

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Calcev, George, Michels, James, Bonta, Jeffrey
• Granted Patent: US 7,272,129 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A method and apparatus for synchronizing a node (200) within an ad-hoc communication system (100) is described herein. During operation all nodes periodically broadcast a synchronization beacon for other nodes to utilize for synchronization when a coordinating access point (node) is unavailable. A particular node'"'"'s synchronization beacon will have an associated “tier” number that is incremented from the tier number of the beacon used to synchronize the particular node. In the absence of an access point, a node that joins the ad-hoc communication system will listen for synchronization beacons transmitted by other nodes. If synchronization beacons are heard, the node will synchronize with a beacon having a lowest tier. The node will then broadcast its own beacon having its tier number incremented from the lowest tier beacon heard.

Claims

1. A method for a node to synchronize to an ad-hoc communication system, the method comprising the steps of:

listening for a plurality of synchronization beacons transmitted from a plurality of nodes;

if synchronization beacons are heard, performing the steps of;

determining a tier for each synchronization beacon heard;

synchronizing to a beacon having a lowest tier;

transmitting a beacon having a tier greater than the lowest tier; and

if synchronization beacons are not heard, performing the steps of;

transmitting a beacon having a first tier.

2. The method of claim 1 wherein the step of transmitting the beacon comprises the steps of:

creating the beacon comprising a beacon identification and a tier number; and

transmitting the beacon having the beacon identification and a tier number.

3. The method of claim 1 wherein the step of transmitting the beacon having the beacon identification and the tier number comprises the step of transmitting the beacon having a physical address of the tier #0 node as the beacon identification.

4. The method of claim 1 wherein the step of transmitting the beacon having the beacon identification and the tier number comprises the step of transmitting the beacon having a medium access controller address of the tier #0 node as the beacon identification.

5. The method of claim 1 wherein the step of transmitting the beacon having the first tier comprises the step of transmitting the beacon having a tier equal to zero.

6. The method of claim 1 wherein the step of transmitting the beacon having the tier greater than the lowest tier comprises the step of transmitting the beacon having a tier incremented by one from the lowest tier.

7. The method of claim 1 further comprising the steps of:

determining that a beacon exists having a lower tier than the beacon utilized for synchronization; and

reestablishing synchronization to the beacon having the lower tier.

8. The method of claim 7 further comprising the step of:

transmitting a beacon having a tier greater than the beacon used to synchronize with.

9. A method comprising the steps of:

determining that a synchronization beacon cannot be heard;

creating a beacon having a tier number equal to zero, and a beacon identification field based on a node'"'"'s physical address; and

transmitting the beacon having the tier number and beacon identification field.

10. The method of claim 9 wherein the step of creating a beacon having a beacon identification field based on a node'"'"'s physical address comprises the step of creating a beacon identification field based on the node'"'"'s medium access controller address.

11. An apparatus comprising:

a receiver listening for a plurality of synchronization beacons transmitted from a plurality of nodes;

logic circuitry determining a tier for each synchronization beacon heard and synchronizing to a beacon having a lowest tier; and

a transmitter transmitting a beacon having a tier greater than the lowest tier.

12. The apparatus of claim 11 wherein the beacon additionally comprises a beacon identification field.

15. The apparatus of claim 11 the tier greater than the lowest tier comprises a tier incremented by one from the lowest tier.

16. The apparatus of claim 11 wherein the logic circuitry will reestablish synchronization to a beacon having a lower tier.

13. The apparatus of claim 13 wherein the beacon identification field comprises a physical address of a lowest tier node.

14. The apparatus of claim 13 wherein the beacon identification field comprises a medium access controller address of a tier #0 node.