SYSTEM AND METHODS FOR SYNCHRONIZING EDGE DEVICES ON CHANNELS WITHOUT CARRIER SENSE

• US 20130034086A1
• Filed: 08/03/2012
• Published: 02/07/2013
• Est. Priority Date: 08/03/2011
• Status: Active Grant

• Current Assignee: Dominion Enterprises (Landmark Media Enterprises LLC), TRC Companies Incorporated
• Original Assignee: Power Tagging Technologies, Inc.
• Inventors: BERNHEIM, Henrick F., MARTIN, Marcia R., ABENDSCHEIN, Andrew Louis
• Granted Patent: US 9,380,545 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04L 41/5022 by giving priorities, e.g. assigning classes of service
• CPC Class Codes: H04L 47/6245 Modifications to standard FIFO or LIFO
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence
• CPC Class Codes: H04W 28/065 using assembly or disassembly of packets
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 74/0891 for synchronized access

Abstract

A system and method are disclosed for synchronizing edge devices on a network, wherein the network has limited bandwidth and does not support a practical carrier sense mechanism. The edge devices transmit, using a slotted protocol, to a server located at a central data aggregation point. The server also controls a Central Transmitter, which sends messages to the edge devices to assign transmission slots and provide timing information to the edge devices to ensure that transmissions sent by devices sharing the same communication channel do not collide.

Claims

1. A system for synchronizing edge devices on a communication network, comprising:

a Server;

a Receiver; and

a Central Transmitter (CT) or simulated Central Transmitter;

wherein the Server, Receiver and CT or simulated CT are sited at the central hub of a network; and

a multiplicity of Intelligent Communicating Devices (ICDs) located at various endpoints at or near the edge of said network;

wherein system clocks on said ICDs are precisely synchronized with one another and the central hub; and

wherein said state of synchronization is maintained by broadcasting in a loosely scheduled, unpredictable fashion a Master Frame Announcement message which, when received by the ICDs allows said endpoints to maintain said state of synchronization.

2. The system of claim 1, where the network is an electrical distribution grid.

3. The system of claim 2, where the CT is an on-grid transmitter.

4. The system of claim 1, where the CT is a private radio transmitter.

5. The system of claim 1, where the CT is simulated by a wireless two-way network.

6. The system of claim 1, wherein the ICDs contain receivers appropriate to the type of CT in use at the central hub.

7. The system of claim 1, wherein the CT is controlled by a software system consisting of a Broadcast Queue Server, a Broadcast Transmission Queue and a Broadcast Server.

8. The system of claim 7, wherein broadcast of messages by the CT is simulated by means of ICDs, which periodically poll said Broadcast Server and receive in response all messages presently in the Broadcast Transmission Queue that have not already been transmitted to the polling ICD.

9. The system of claim 1, further comprising a multiplicity of hub Servers with Receivers sharing a remote CT, each Server being connected to the shared CT by a high-speed conventional two-way network.

10. The system of claim 9, wherein the CT is an on-grid transmitter located at a point on the electrical transmission grid that delivers electrical power to the network.

11. The system of claim 9, wherein the CT is a private radio transmitter.

12. The system of claim 9, wherein the CT is a public broadcast transmitter.

13. The system of claim 9, wherein the ICDs contain receivers appropriate to the type of CT shared by the hub Servers.

14. The system of claim 9, wherein one and only one of the multiplicity of hub Servers is designated as the source of Master Frame Announcements, and all of the multiplicity of networks use the same slot size and master frame cycle.

15. The system of claim 9, wherein each hub Server sends Master Frame Announcements, and the ICDs associated with each hub Server can distinguish the Master Frame Announcements from their Server from the Master Frame Announcements of other Servers.

16. The system of claim 15, wherein the shared CT governs the origin and duration of a transmission slot for all ICDs sharing said CT, and all Master Frame Announcements from any Server must originate on a slot boundary.

17. A system for synchronizing edge devices on a communication network, comprising:

a central hub of a network with a central hub Server and a Receiver, and a multiplicity of ICDs located at various points on the network;

wherein the system clocks on said endpoints are precisely synchronized with one another and the central hub Server; and

wherein said state of synchronization is maintained by means of the endpoints polling said central hub Server at a known polling frequency using a TCP/IP network with unpredictable latency.

18. The system of claim 17 wherein network is an electrical distribution grid.

19. The system of claim 17 where the ICDs poll the central hub by means of an independent TCP/IP network.

20. The system of claim 19 where the TCP/IP network is a cellular network.

21. The system of claim 19 wherein the elements of the network, including the endpoints, the Receiver, and the central hub Server, maintain synchronization of their system clocks by means of a third-party protocol.

22. The system of claim 19 wherein the third-party protocol is NTP or PTP (IEEE 1588).

23. The system of claim 19 wherein the third-party protocol is CDMA or GSM.

24. The system of claim 19 wherein an alternative mechanism than the polling protocol is used to provide time clock synchronization but not Master Frame Announcements.

25. The system of claim 24 wherein the alternative mechanism is a broadcast from an on-grid transmitter.

26. The system of claim 24 wherein the alternative mechanism is an RF timing pulse broadcast on the same network medium as provides the TCP/IP substrate.

27. The system of claim 24 wherein the alternative mechanism is an RF timing pulse broadcast on a different network medium or source than provides the TCP/IP substrate.

28. A method for synchronizing edge devices on a communication network, comprising:

a) hosting a Queue Server on a Server;

b) creating a Broadcast Queue stored on said Server, wherein said Queue Server publishes an interface whereby multiple application Agents may place messages in the Broadcast Queue; and

c) reordering, by the Queue Server, the messages in the Broadcast Queue according to a policy expressed in terms of a Maximum Contractual Wait Time associated with each message; and

d) hosting a Framing Agent on said Server, wherein said Framing Agent places Master Frame Announcements into said Broadcast Queue via the interface,

e) hosting a Broadcast Server on said Server, wherein said Broadcast Server removes messages from the Broadcast Queue and causes a Central Transmitter to broadcast the messages to one or more ICDs; and

f) transmitting messages from said ICDs to the Receiver on one or more slotted channels based on a schedule controlled by said Master Frame Announcements and other messages from said Central Transmitter, wherein said ICDs adjust the timing of said transmissions based on information in the Master Frame Announcements.

29. The method of claim 28, wherein the Framing agent, the Queue Server, the Message Queue, and the Broadcast Server are stored and run on a hub Server.

30. The method of claim 28, wherein other applications in addition to a Framing Agent place messages into the Message Queue for transmission by the Broadcast Server.

31. The method of claim 28, wherein the Queue server reprioritizes the messages in the Message Queue to ensure that Master Frame Announcements are broadcast before a Contractual Maximum Wait Time has elapsed.

32. The method of claim 28, wherein the Queue server notifies the sender of a message if it cannot be broadcast before its Contractual Maximum Wait Time has elapsed.

33. The method of claim 28, wherein applications specify the disposition of a message which cannot be broadcast prior to its Contractual Maximum Wait Time, wherein said message is broadcast or wherein said message is removed from the queue without being broadcast.

34. The method of claim 28, wherein the Broadcast server appends the actual transmission time to each message as it is broadcast.

35. The method of claim 28, wherein the ICDs use said appended actual transmission time to synchronize their local system clocks.

36. The method of claim 28, wherein an ICD will cease to transmit if, at the end of a Master Frame, it has not received a Master Frame Announcement announcing the time of the next Master Frame Origin.

37. The method of claim 28, wherein the CT controlled by the Broadcast Server is remote from the hub Server and may be shared by multiple hub Servers.

38. The method of claim 37, wherein the Broadcast Server and the Broadcast Message Queue reside on a separate Server or Controller co-located with remote CT.

39. The method of claim 37, wherein the Queue Server running on the hub Servers communicates with a Remote Queue Server running on a separate Server or Controller co-located with the remote CT, and wherein the Remote Queue Server arranges the messages in the Queue to enforce the Contractual Maximum Wait Times for all messages.

55. The method of claim 28, wherein the message currently being transmitted by the CT is aborted in order that an emergency message can be transmitted immediately.

56. The method of claim 55, wherein the interrupted message, if it is a Master Frame Announcement, is retransmitted as soon as the emergency message is complete, or as soon thereafter as the duty cycle of the CT permits.

57. The method of claim 55, wherein if an emergency transmission has not aborted a Master Frame Announcement but there is a Master Frame Announcement in the Broadcast Transmission Queue, the Broadcast Server will move said Master Frame Announcement to the head of the Broadcast Transmission Queue and requeues the aborted message behind said Master Frame Announcement.

58. The method of claim 55, further comprising the steps of following a reordering of the Broadcast Transmission Queue due to the arrival and processing of an emergency transmission, reviewing the waiting messages in the Broadcast Transmission Queue, revising the disposition of some messages, and notifying the message senders including the Framing Agent of the new dispositions.

59. The method of claim 28 whereby the Queue Server manages the Broadcast Transmission Queue so as to guarantee the timely transmission of Master Frame Announcements.

60. The method of claim 28 whereby the Queue Server notifies the sender of each message of the initial disposition of the message.

70. The method of claim 28, wherein, when an ICD detects, by comparing its system clock and the transmission time in a Master Frame Announcement that clock drift has occurred, said ICD defers making the prescribed clock adjustment until the next time period when the ICD is not transmitting.

40. A method for synchronizing edge devices on a communication network, comprising:

a) hosting a Queue Server software on a Server, wherein said Queue Server creates a Simulated Broadcast Queue stored on said Server, and wherein said Queue Server publishes an interface whereby multiple application Agents may place messages in the queue;

b) running a Framing Agent on said Server wherein said Framing Agent places Master Frame Announcements into the Simulated Broadcast Queue via said interface, wherein said Master Frame Announcements announce the origin time of a next master frame;

c) providing a Simulated Broadcast Server, wherein said Simulated Broadcast Server emulates the behavior of a Central Transmitter capable of true broadcast transmission using an alternative two-way network by responding to polls by ICDs on said alternative two-way network, wherein said Simulated Broadcast Server responds to polls from said ICDs on said alternative two-way network; and

d) wherein said ICDs poll said Simulated Broadcast Server via said alternative two-way network and adjust their transmission schedules based on information in said Master Frame Announcements.

41. The method of claim 40, wherein the interface between the Queue Server and the Framing Agent, and the interface between the Queue server and other applications using the message queue to convey information to the ICDs, is identical with the interfaces employed for a system and method where true broadcast transmission is available.

42. The method of claim 40, wherein the Broadcast Server does not append a timestamp to messages.

43. The method of claim 40, wherein the Queue server assigns each new message a monotonically increasing sequence number unique to the Simulated Broadcast Queue which the message is entering.

44. The method of claim 40, wherein the Simulated Broadcast Server maintains an inventory of all ICDs to which the Simulated Broadcast Server is expected to respond.

45. The method of claim 44, wherein the Simulated Broadcast Server associates with the inventory record of each ICD the highest message sequence number which said ICD has already received.

46. The method of claim 40, where each ICD polls the Simulated Broadcast Server on a periodic basis.

47. The method of claim 46, wherein the Simulated Broadcast Server responds to the poll of an ICD by transmitting to said ICD all the messages in the Simulated Broadcast Queue which have a higher sequence number than that associated with the ICD which has polled.

48. The method of claim 47, wherein, after responding to a poll by an ICD, the Simulated Broadcast Server updates the inventory record of said ICD with the highest sequence number transmitted to said ICD in the latest polling response.

49. The method of claim 48, wherein the Simulated Broadcast Server removes from the Simulated Broadcast Queue any message which has a lower sequence number than every ICD in the inventory.

50. The method of claim 40, wherein messages which have resided in the Simulated Broadcast Queue for longer than a predefined number of polling cycles are removed from the queue, where a polling cycle is the interval of time in which all ICDs associated with this Server are expected to have polled once.

51. The method of claim 40, wherein the polling protocol provides a synchronous central system time to the ICDs when they poll.

52. The method of claim 40, wherein an alternative protocol is used to synchronize the ICDs.

53. The method of claim 40, wherein polling is used for the transport of messages including Master Frame Announcements, and wherein a true broadcast CT is used to provide a timing pulse to synchronize the ICDs.

54. The method of claim 53, wherein the Master Frame Announcement or another priority message type is used to pre-announce the time at which a timing pulse will occur.

61. The method of claim 40, wherein the ICDs poll with a regular frequency less than or equal to a Contractual Maximum Wait Time.

62. The method of claim 40, wherein each ICD initiates its polling cycle with a different offset from the master frame from any other ICD.

63. The method of claim 40, wherein groups of ICDs share the same offset in time from the master frame as the origin of their polling cycle.

64. The method of claim 40, wherein the polling frequency of each ICD is randomly assigned a value lying between a minimum frequency and the Contractual Wait Time.

65. The method of claim 40, wherein the origin of each ICD'"'"'s polling cycle is related to the geospatial location of the endpoint.

66. The method of claim 40, wherein if the ICD has failed to receive a Master Frame Announcement containing the next Master Frame Origin prior to the end of the current Master Frame, an endpoint suspends transmission on all of a multiplicity of on-grid channels provided in the network, but continues to attempt to poll a Data Collection Server.

67. The method of claim 66, wherein said ICD resumes transmissions following receipt of a new Master Frame Announcement beginning with the next scheduled transmission in the current Master Frame.

68. The method of claim 40 wherein, when an ICD detects by means of a third-party synchronization protocol that its clock has drifted, said ICD defers making the prescribed clock adjustment until a time period when the ICD is not transmitting.

69. The method of claim 40, wherein a Master Frame Announcement is always placed in the Simulated Broadcast Queue in advance of the Master Frame Origin by at least twice the polling interval of said ICDs.