Clock synchronization aid device for communication station(s) of a wireless network, and associated clock synchronization device

• US 20080186906A1
• Filed: 01/30/2008
• Published: 08/07/2008
• Est. Priority Date: 02/05/2007
• Status: Active Grant

• Current Assignee: Magnolia Licensing LLC (IP Edge LLC)
• Original Assignee: Thomson Licensing SA (Vantiva SA)
• Inventors: Tapie, Thierry, Jeanne, Ludovic, Defrance, Serge
• Granted Patent: US 8,730,867 B2
• Time in Patent Office: Days
• US Class Current: 370/324
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 84/20 Master-slave selection or change arrangements

Abstract

A device (DA1) is intended to aid a clock synchronization device (DS1) of a master station (SM) of a wireless network in performing time synchronizations, this master station (SM) comprising a master clock (HM) represented by the value of a master counter (CM) and means (MG1) for generating wireless frames of IP packets containing in particular PTP messages of first and second types. The aid device (DA1) comprises detection means (MD1) for, in case of detection by the physical layer of the master station (SM) of a frame pulse received from the network, triggering the sampling of the value of the master counter (CM)

Claims

1. Time synchronization aid device (DA1) for a clock synchronization device (DS1) of a master communication station (SM) of a wireless communication network specifically for transporting IP packet frames, said master station (SM) comprising a master clock (HM) defining a reference time represented by the value of a master counter (CM), said device (DA1) comprising detection means (MD1) arranged, in case of detection by the physical layer of said master station (SM) of a frame pulse received from said network, to trigger a sampling of the value of the master counter (CM), wherein in the presence of a master station (SM) comprising generation means (MG1) arranged to generate in the form of wireless frames of IP packets, addressed to at least one slave communication station (SE) of said network, PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, said detection means (MD1) are arranged to detect, following the triggering of a sampling of the value of said master counter (CM), whether a wireless frame, which is being transmitted by said master station (SM), contains at least a chosen part of a message of the first type, and if it does, to associate with this wireless frame said sampling of the value of the master counter, and, if the wireless frame actually contains a message of the first type, to alert said clock synchronization device (DS1) in order for it to supply the image of this sampling to said generation means (MG1) for them to incorporate it in the message of the second type that follows this message of the first type.

2. Aid device according to claim 1, wherein it comprises i) first storage means (M11) arranged to store the sampling of the value of the master counter (CM) in case of detection of said chosen message part by said detection means (MD1) and ii) second storage means (M12) arranged to store said sampling of the value of the master counter (CM) stored in said first storage means (M11) when a PTP message which has been transmitted in full is actually of the first type, and in that said detection means (MD1) are arranged, in case of detection of a wireless frame containing a message of the first type, to alert said clock synchronization device (DS1) for it to supply the image of the sampling of the value that is stored in said second storage means (M12) to said generation means (MG1) to incorporate it in the message of the second type that follows the message of the first type detected by said detection means (MD1).

3. Aid device according to claim 1, wherein the detection means (MD1) are arranged to detect whether a wireless frame currently being received contains at least a chosen part of a PTP message of a third type, originating from a slave station (SE) and requesting the sending to the latter of a PTP message of a fourth type, and if it does, to associate with this wireless frame the image of the sampling of the value of the master counter (CM) that corresponds to the last frame pulse preceding the moment of detection of this chosen part of the message of the third type, and if the wireless frame actually contains a message of the third type, to alert said clock synchronization device (DS1) for it to supply said image of the sampling of the value to said generation means (MG1) to incorporate it in a message of the fourth type responding to the message of the third type received.

4. Clock synchronization device (DS1, DS1′

) for a master station (SM) of a wireless communication network specifically for transporting IP packet frames, said master station (SM) comprising a master clock (HM) defining a reference time represented by the value of a master counter (CM), and generation means (MG1) arranged to generate in the form of wireless frames of IP packets, addressed to at least one slave station (SE) of said network, PTP messages of a first type and of a second type, wherein it comprises a time synchronization aid device (DA1) according to claim 1.

5. Clock synchronization device (DS1, DS1′

) for a master station (SM) of a wireless communication network specifically for transporting IP packet frames, said master station (SM) comprising a master clock (HM) defining a reference time represented by the value of a master counter (CM), and generation means (MG1) arranged to generate in the form of wireless frames of IP packets, addressed to at least one slave station (SE) of said network, PTP messages of a first type and of a second type, wherein it comprises a time synchronization aid device (DA1) according to claim 2.

6. Clock synchronization device (DS1, DS1′

) for a master station (SM) of a wireless communication network specifically for transporting IP packet frames, said master station (SM) comprising a master clock (HM) defining a reference time represented by the value of a master counter (CM), and generation means (MG1) arranged to generate in the form of wireless frames of IP packets, addressed to at least one slave station (SE) of said network, PTP messages of a first type and of a second type, wherein it comprises a time synchronization aid device (DA1) according to claim 3.

7. Master communication station (SM) for a wireless communication network specifically for transporting IP packet frames, said master station (SM) comprising a master clock (HM) defining a reference time represented by the value of a master counter (CM), and generation means (MG1) arranged to generate in the form of wireless frames of IP packets, addressed to at least one slave station (SE) of said network, PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, wherein it comprises a time synchronization aid device (DA1) according to one of claims 1.

8. Master communication station (SM) for a wireless communication network specifically for transporting IP packet frames, said master station (SM) comprising a master clock (HM) defining a reference time represented by the value of a master counter (CM), and generation means (MG1) arranged to generate in the form of wireless frames of IP packets, addressed to at least one slave station (SE) of said network, PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, wherein it comprises a clock synchronization device (DS1) according to one of claims 4.

9. Time synchronization aid device (D2) for a synchronization device (DS2) of a slave station (SE) of a wireless communication network specifically for transporting IP packet frames, said slave station (SE) comprising a slave clock (HE) defining a local time represented by the value of a slave counter (CE), said device (D2) comprising detection means (MD 2) arranged, in case of detection by the physical layer of said master station (SM) of a frame pulse received from said network, to trigger a sampling of the value of the slave counter (CE), wherein in the presence of a slave station (SE) comprising reception means (RM) arranged to receive wireless frames of IP packets originating in particular from a master station (SM) of said network, having a master clock (HM) defining a reference time represented by the value of a master counter (CM), some of said wireless frames forming PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, said detection means (MD1) are arranged, following the triggering of a sampling of the value of the slave counter (CE), to detect whether a wireless frame, which is currently being received by said slave station (SE), contains at least a chosen part of a message of the first type, and if it does, to associate with this wireless frame said sampling of the value of the slave counter (CE), and if said wireless frame actually contains a message of the first type, to alert the clock synchronization device (DS2) in order for it to use this value to synchronize said slave clock (HE) on said master clock (HM).

10. Aid device according to claim 9, wherein it comprises i) first storage means (M21) arranged to store the sampling of the value of the slave counter (CE) in case of detection of a chosen message part by said detection means (MD2), and ii) second storage means (M22) arranged to store said sampling of the value of the slave counter (CE) stored in said first storage means (M21) when a PTP message which has been received in full is actually of the first type, and in that said detection means (MD2) are arranged, in case of detection of a wireless frame containing a message of the first type, to alert said clock synchronization device (DS1) for it to use the image of the sampling of the value that is stored in said second storage means (M22) to synchronize said slave clock (HE) on said master clock (HM).

11. Aid device according to claim 9, wherein the detection means (MD2) are arranged to detect whether a wireless frame currently being transmitted contains at least a chosen part of a chosen octet of a chosen IP packet of a PTP message of a third type, addressed to said master station (SM) and requesting the sending to the latter of a PTP message of a fourth type, and if it does, to associate with this wireless frame said image of the sampling of the value of the master counter (CM) which corresponds to the last frame pulse preceding the moment of detection of the chosen part of the message of the third type, and if said wireless frame actually contains a message of the third type, to alert said clock synchronization device (DS2) for it to use this value to synchronize said slave clock (HE) on said master clock (HM).

12. Clock synchronization device (DS2, DS2′

) for a slave station (SE) of a wireless communication network specifically for transporting IP packet frames, said slave station (SE) comprising a slave clock (HE) defining a local time represented by the value of a slave counter (CE), and reception means (RM) arranged to receive wireless frames of IP packets originating in particular from a master station (SM) of said network, having a master clock (HM) defining a reference time represented by the value of a master counter (CM), some of said wireless frames forming PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, wherein it comprises a time synchronization aid device (DA2) according to claim 9.

13. Clock synchronization device according to claim 12, wherein it comprises analysis means (MA2) arranged, i) in case of reception by said reception means (RM) of a frame containing a message of the second type following another frame containing a message of the first type, to extract from said message of the second type the image of the sampling of the value of the master counter that it contains, and to determine the image of the sampling of the value associated with said message of the first type by said detection means (MD2), and ii) in case of reception by said reception means (RM) of a frame containing a PTP message of a fourth type following the transmission of a frame containing a message of the third type, to extract from said message of the fourth type the image of the sampling of the value of the master counter that it contains, and to determine the image of the sampling of the value associated with said message of the third type by said detection means (MD2), and to synchronize said slave clock (HE) on said master clock (HM) according to these four value sampling images.

14. Slave communication station (SE) for a wireless communication network specifically for transporting IP packet frames, said slave station (SE) comprising a slave clock (HE) defining a local time represented by the value of a slave counter (CE), and reception means (RM) arranged to receive wireless frames of IP packets originating in particular from a master station (SM) of said network, having a master clock (HM) defining a reference time represented by the value of a master counter (CM), some of said wireless frames forming PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, wherein it comprises a time synchronization aid device (DA2) according to one of claims 9.

15. Slave communication station (SE) for a wireless communication network specifically for transporting IP packet frames, said slave station (SE) comprising a slave clock (HE) defining a local time represented by the value of a slave counter (CE), and reception means (RM) arranged to receive wireless frames of IP packets originating in particular from a master station (SM) of said network, having a master clock (HM) defining a reference time represented by the value of a master counter (CM), some of said wireless frames forming PTP messages of a first type and of a second type, each message of the first type signalling the transmission in the message of the second type that follows it of an image of the sampling of the value that said master counter (CM) presented on its generation, wherein it comprises a clock synchronization device (DS2) according to one of claims 12.