Method for synchronizing nodes of cellular network

Abstract

A method for synchronizing nodes of a cellular network in which a base station transceiver (BTS) as a first node of the cellular network wirelessly transmits clock information according to a first communication protocol to a terminal device connected to the cellular network as a second node of the cellular network; and a computer program product.

Description

[0001] The present invention relates to a method for synchronizing nodes of a cellular network, wherein a base transceiver station (BTS) as a first node of the cellular network wirelessly transmits clock information to a terminal device connected to the cellular network as a second node of the cellular network according to a first communication protocol. The present invention also relates to a computer program product.

[0002] The method allows a terminal device (ie user equipment UE) connected to a cellular network to be synchronized with the cellular network. Synchronization is achieved by distributing clock information (eg UTC timestamps) within the cellular network (ie transmitting clock information between nodes of the cellular network).

[0003] A cellular network generally includes a plurality of BTSs, each of which is a node of the cellular network and establishes a cellular cell of the cellular network. A cellular cell includes a portion of the earth's surface that allows a terminal device having a radio interface to be wirelessly connected to a BTS (i.e., connected to the cellular network "over the air"). A terminal device connected to a BTS of a cellular network is also considered herein to be a node of the cellular network.

[0004] Of course, the BTS needs to know the time in order to distribute the clock information to the connected terminal devices. The BTS can receive the clock information from the Global Navigation Satellite System (GNSS). The BTS can also receive the clock information from a third node of the cellular network, for example, according to the Precision Time Protocol (PTP). The BTS usually executes a PTP client to receive the clock information from the third node.

[0005] Note that the term "protocol" should be understood in a general manner, i.e., a protocol specifies a plurality of rules that allow two or more nodes to transmit information between each other via a varying physical quantity. A protocol may specify the rules, syntax, semantics, and / or synchronization of the transmitted information. Different protocols may involve different network layers and / or different networking planes.

[0006] The BTS may wirelessly transmit the received clock information to the terminal device according to a communication protocol different from PTP (eg, according to a 5G communication protocol specified by the 3rd Generation Partnership Project (3GPP)).

[0007] The BTS may additionally provide clock accuracy information.

[0008] The 3GPP draft "KI#1, Sol#1: Update to remove EN" released on May 6, 2022 discloses a method for transmitting clock information and clock accuracy information to a terminal device via radio resource control (RRC) and precision time protocol ((g)PTP), respectively, wherein the clock accuracy information is forwarded to and utilized by a device attached to the terminal device.

[0009] WO 2021 / 181363 A1 discloses a method for wirelessly transmitting clock accuracy information to a terminal device using at least one of a plurality of different communication protocols.

[0010] However, the 5G communication protocol does not actually allow the BTS to transmit clock accuracy information to the terminal device. Therefore, the terminal device is prevented from considering the accuracy of synchronization.

[0011] Therefore, an object of the present invention is to propose a method for synchronizing nodes of a cellular network which method efficiently allows a BTS to wirelessly transmit clock accuracy information to a terminal device and allows a terminal device to efficiently receive clock accuracy information. Another object of the present invention is to provide a computer program product.

[0012] A first aspect of the present invention is a method for synchronizing nodes of a cellular network, wherein a base transceiver station BTS as a first node of the cellular network wirelessly transmits clock information to a terminal device connected to the cellular network as a second node of the cellular network according to a first communication protocol. The transmitted clock information synchronizes the terminal device with the BTS. The first communication protocol may be a 5G communication protocol specified by 3GPP, in particular an access stratum AS layer of a radio access network RAN.

[0013] According to the present invention, the BTS transmits clock accuracy information to the terminal device according to the first communication protocol, and the clock accuracy information is specified by the second communication protocol different from the first communication protocol. In other words, the first communication protocol is used to additionally transmit the clock accuracy information, although the clock accuracy information is specified by the second communication protocol and provided according to the second communication protocol.

[0014] Thus, the transmission of the clock accuracy information relies on a single communication protocol being available, regardless of the different communication protocols defining the clock accuracy information to be transmitted. On the one hand, no wireless connection is required to support the second communication protocol. On the other hand, no additional communication protocol has to be specified for transmitting the clock accuracy information. Thus, the method can be implemented very efficiently.

[0015] In an embodiment, the network layer of the first communication protocol is different from the network layer of the second communication protocol and / or wherein the networking plane of the first communication protocol is different from the networking plane of the second communication protocol. The network layers are specified by the Open Systems Interconnection (OSI) model. For example, the first communication protocol is applied to layer 3, the so-called network layer, and the second communication protocol is applied to layer 7, the so-called application layer. The networking plane is a component of the cellular network architecture and includes a control plane and a user plane, the latter also referred to as a data plane, forwarding plane, carrying plane or bearer plane. The control plane includes a management plane as a subset.

[0016] In a typical cellular network, the user plane supports the transmission of application data (e.g., Internet data) and requires a protocol data unit (PDU) session established in the control plane that supports signaling traffic. Although the control plane is independent of the user plane, the user plane depends on the control plane. Control plane transmission between BTS and terminal devices is carried out according to the access layer protocol. Control plane transmission between the core server of the cellular network and the terminal device is carried out according to the non-access layer NAS layer protocol.

[0017] Preferably, each of the clock information and the clock accuracy information is transmitted according to a radio resource control (RRC) protocol as a first communication protocol, and the clock accuracy information is specified by a precision time protocol (PTP) as a second communication protocol. Using the PTP clock accuracy information avoids redundant definitions and conversions between different definitions of the clock accuracy information. In addition, both the BTS and the terminal device generally have PTP capabilities.

[0018] The BTS may transmit the PTP clock accuracy information as part of an RRC message and / or RRC information specified by the RRC protocol. The RRC message and RRC information are categories of data entities specified by the RRC protocol. The RRC message and / or RRC information are related to the AS layer.

[0019] Preferably, the BTS transmits the PTP clock accuracy information as part of a master information block (MIB) specified by the RRC protocol or as part of a system information block (SIB) specified by the RRC protocol. The transmission of the PTP clock accuracy information relies on the MIB or SIB specified by the RRC protocol 3GPP TS 38.331 6.2.2 or 3GPP TS 38.331 6.3.1. The SIB is transmitted periodically or in response to a request from a terminal device.

[0020] The BTS may transmit the PTP clock accuracy information as part of SIB1 or as part of SIB9 specified by the RRC protocol. SIB1 is specified by 3GPP TS 38.331, 6.2.2. SIB9 is specified by 3GPP TS 38.331, 6.3.2. Note that the clock information is conveyed in SIB9.

[0021] In one embodiment, the BTS transmits the PTP clock accuracy information via a broadcast channel (BCH) or via a download shared channel (DL-SCH).

[0022] Advantageously, the PTP client of the BTS receives a PTP notification message from a third node of the cellular network and transmits the content of the received PTP notification message as PTP clock accuracy information. The PTP notification message is specified by IEEE 1588 and includes quality information about the clock. The third node can be configured as a core server of the cellular network. Of course, the BTS can receive different clock accuracy information and convert the different clock accuracy information into PTP clock accuracy information.

[0023] A clockClass value, a clockAccuracy value, and / or an offsetScaledLogVariance value may be delivered as content. The clockClass value specifies the state of the local clock. The clockAccuracy value specifies the estimated time error. The offsetScaledLogVariance value specifies the variance of the clock information.

[0024] The PTP master executed by the terminal device can receive the PTP clock accuracy information. The PTP master can consider the accuracy of synchronization or forward the PTP clock accuracy information to the PTP client. Of course, the PTP clock accuracy information can be alternatively forwarded according to another specification different from PTP.

[0025] In an advantageous embodiment, a PTP client of a user application executed by a terminal device receives PTP clock accuracy information from a PTP master device. The user application can take into account the accuracy of synchronization. Alternatively, a PTP client of another device connected to the terminal device or a PTP client of a user application executed by the other device can receive PTP clock accuracy information. The received PTP clock accuracy information can be used to sound an alarm or enable the terminal device or the other device to select the best time source.

[0026] The terminal device or a user application executed by the terminal device may perform a Best Master Clock Algorithm (BMCA) depending on the received PTP clock accuracy information. BMCA is a time source selection algorithm specified by IEEE 1588 and allows the terminal device to select a PTP master clock GM, i.e. a timing reference, depending on the accuracy of the provided clock information.

[0027] The clock accuracy information is preferably transmitted once per second. Once per second is a transmission rate sufficient for the clock accuracy information while not causing a heavy load on the wireless connection.

[0028] In one embodiment, the g B node transmits clock accuracy information as a BTS. The g B node is a 5G base station.

[0029] A second aspect of the invention is a computer program product comprising a computer readable medium storing program code. The computer readable medium comprises a digital storage unit, such as a USB stick, a digital versatile disk (DVD), a hard disk, a random access memory (RAN), a chip, an Internet cloud, etc.

[0030] According to the present invention, the program code, when executed by a processor of a computing device, enables the computing device to participate in the method according to the present invention as a BTS or as a terminal device. The computing device reads the program code stored by a computer-readable medium and executes the read program code. The read program code enables the computing device to perform the method as a BTS or as a terminal device. The computing device can be configured as server hardware or a smart phone, etc.

[0031] A fundamental advantage of the method of the invention is that the method can be implemented very efficiently. On the one hand, no wireless connection is required to support the second communication protocol. On the other hand, no additional communication protocol has to be specified for transmitting the clock accuracy information. In addition, existing clock accuracy definitions can be used and conversion between different definitions of clock accuracy information is avoided.

[0032] Further advantages and configurations of the present invention will become apparent from the following description and accompanying drawings.

[0033] It is understood that the features described previously and hereinafter can be used not only in the combination indicated but also in different combinations or alone, without departing from the scope of the present invention.

[0034] The present invention is described in detail by means of exemplary embodiments and with reference to the accompanying drawings. In the entire drawings, the same components are indicated by the same reference numerals.

[0035] Figure 1 A partial diagram of a cellular network synchronized by the method according to the invention is schematically shown.

[0036] Figure 1 A partial diagram of a cellular network 1 synchronized by the method according to the present invention is schematically shown. The cellular network 1 comprises a base transceiver station BTS 10 as a first node of the cellular network 1. The BTS 10 may be configured as a g B-node specified by the 5G standard. The BTS 10 may comprise a Precision Time Protocol (PTP) client 100.

[0037] The cellular network 1 further includes a terminal device 11 connected to the cellular network 1 as a second node of the cellular network 1. The terminal device 11 may include a PTP master device 111 and a user application 110. The user application 110 may include a PTP client 1100.

[0038] Each of the BTS 10 and the terminal device 11 can be implemented by means of a computing device and a computer program product, respectively. The computer program product comprises a computer readable medium storing program code which, when executed by a processor of a computing device, causes the computing device to participate in the method according to the invention as the BTS 10 and the terminal device 11, respectively.

[0039] The nodes of the cellular network 1 are synchronized by executing the method of the present invention as follows.

[0040] The BTS 10 wirelessly transmits clock information 1200 to the terminal device 11 connected to the cellular network 1 according to the first communication protocol.

[0041] The BTS 10 further transmits clock accuracy information according to the first communication protocol to the terminal device 11. g Node B preferably transmits the clock accuracy information as the BTS 10. The clock accuracy information is preferably transmitted once per second.

[0042] The clock accuracy information is specified by a second communication protocol different from the first communication protocol. In particular, a network layer of the first communication protocol is different from a network layer of the second communication protocol and / or a networking face of the first communication protocol is different from a networking face of the second communication protocol.

[0043] Each of the clock information 1200 and the clock accuracy information may be transmitted according to the radio resource control (RRC) protocol 12 as the first communication protocol. The BTS 10 preferably transmits the clock accuracy information 130 as part of the SIB, RRC message and / or RRC information specified by the RRC protocol 12.

[0044] The clock accuracy information may be specified by the Precision Time Protocol (PTP) 13 as a second communication protocol. The BTS 10 preferably transmits the PTP clock accuracy information 130 as part of a Master Information Block (MIB) 120 specified by the RRC protocol 12 or as part of a System Information Block (SIB) specified by the RRC protocol 12.

[0045] The BTS 10 may transmit the PTP clock accuracy information 130 as part of SIB1 121 or part of SIB9 121 specified by the RRC protocol 12. The BTS 10 may transmit the PTP clock accuracy information 130 via a broadcast channel (BCH) or via a download shared channel (DL-SCH).

[0046] The PTP client 100 of the BTS 10 may receive a PTP announcement message from the third node 14 of the cellular network 1 and transmit the content of the received PTP announcement message as the clock accuracy information. The clockClass value, the clockAccuracy value and / or the offsetScaledLogVariance value are preferably transmitted as the content.

[0047] The PTP master 111 executed by the terminal device 11 may receive the PTP clock accuracy information 130. The PTP client 1100 of the user application 110 executed by the terminal device 11 may receive the PTP clock accuracy information 130 from the PTP master 111. The terminal device 11 or the user application 110 executed by the terminal device 11 preferably executes a best master clock algorithm (BMCA) depending on the received PTP clock accuracy information 130.

[0048] Reference numerals

[0049] 1Cellular network

[0050] 10BTS

[0051] 100 PTP Client

[0052] 11 Terminal Equipment

[0053] 110 User Application

[0054] 1100 PTP Client

[0055] 111 PTP master

[0056] 12 RRC Protocol

[0057] 120MIB

[0058] 1200 clock information

[0059] 121SIB

[0060] 13PTP

[0061] 130 PTP clock accuracy information

[0062] 14 Third Node

Claims

1. A method for synchronizing nodes of a cellular network (1), wherein - a base transceiver station BTS (10) as a first node of the cellular network (1) wirelessly transmits clock information (1200) to a terminal device (11) connected to the cellular network (1) as a second node of the cellular network (1) according to a first communication protocol; - the BTS (10) transmits clock accuracy information to the terminal device (11) according to the first communication protocol, the clock accuracy information being specified by a second communication protocol different from the first communication protocol.

2. The method of claim 1, wherein a network layer of the first communication protocol is different from a network layer of the second communication protocol and / or wherein a networking plane of the first communication protocol is different from a networking plane of the second communication protocol.

3. A method as claimed in claim 1 or 2, wherein each of the clock information (1200) and the clock accuracy information is transmitted according to a radio resource control RRC protocol (12) as the first communication protocol, and the clock accuracy information is specified by a precision time protocol PTP (13) as the second communication protocol.

4. The method of claim 3, wherein the BTS (10) transmits the PTP clock accuracy information (130) as a part of an RRC message and / or RRC information specified by the RRC protocol (12).

5. The method of claim 3 or 4, wherein the BTS (10) transmits the PTP clock accuracy information (130) as part of a master information block (MIB) (120) specified by the RRC protocol (12) or as part of a system information block (SIB) (121) specified by the RRC protocol (12).

6. The method of claim 5, wherein the BTS (10) transmits the PTP clock accuracy information (130) as part of SIB1 (121) or part of SIB9 (121) specified by the RRC protocol (12).

7. The method according to claim 5 or 6, wherein the BTS (10) transmits the PTP clock accuracy information (130) via a broadcast channel (BCH) or via a download shared channel (DL-SCH).

8. The method according to any one of claims 3 to 7, wherein the PTP client (100) of the BTS (10) receives a PTP announcement message from a third node (14) of the cellular network (1), and transmits the content of the received PTP announcement message as the clock accuracy information.

9. The method of claim 8, wherein a clockClass value, a clockAccuracy value and / or an offsetScaledLogVariance value are transmitted as the content.

10. The method according to any one of claims 3 to 9, wherein a PTP master (111) executed by the terminal device (11) receives the PTP clock accuracy information (130).

11. The method of claim 10, wherein a PTP client (1100) of a user application (110) executed by the terminal device (11) receives the PTP clock accuracy information (130) from the PTP master device (111).

12. The method according to any one of claims 3 to 11, wherein the terminal device (11) or a user application (110) executed by the terminal device (11) performs a Best Master Clock Algorithm (BMCA) depending on the received PTP clock accuracy information (130).

13. The method of any one of claims 1 to 12, wherein the clock accuracy information is transmitted once per second.

14. The method according to any one of claims 1 to 13, wherein a g Node B transmits the clock accuracy information as the BTS (10).

15. A computer program product comprising a computer-readable medium storing program code which, when executed by a processor of a computing device, causes the computing device to participate as a BTS (10) in the method according to any one of claims 1 to 14.

16. A computer program product comprising a computer-readable medium storing program code which, when executed by a processor of a computing device, causes the computing device to participate as a terminal device (11) in the method according to any one of claims 1 to 14.

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