WO2019117764A1

WO2019117764A1 - Methods and apparatus for providing synchronization within a subnetwork comprising a plurality of nodes

Info

Publication number: WO2019117764A1
Application number: PCT/SE2017/051248
Authority: WO
Inventors: Mårten WAHLSTRÖM; Junggeun PARK
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2017-12-11
Filing date: 2017-12-11
Publication date: 2019-06-20

Abstract

A method is performed in a master node for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized. The method comprises causing a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only. The method comprises distributing the dummy time reference to the plurality of nodes in the subnetwork.

Description

METHODS AND APPARATUS FOR PROVIDING SYNCHRONIZATION WITHIN A

SUBNETWORK COMPRISING A PLURALITY OF NODES

Technical Field

Embodiments described herein relate to methods and apparatus for providing synchronization within a subnetwork comprising a plurality of nodes, for example, time and phase synchronization without using an absolute time reference.

Background

Within communication networks there is a need to provide phase synchronization between nodes of a subnetwork, for example to avoid interference between nodes in that subnetwork. However, it is not necessarily the case that neighboring subnetworks have a requirement to be phase synchronized to a particular subnetwork.

One method of enabling phase synchronization within a network is to use precision time protocol, PTP, to distribute time synchronization information. PTP requires that a particular node, known as a PTP grand master node, is synchronized to an accurate time reference such as, for example, a Global Navigation Satellite System (GNSS). Installing and maintaining a GNSS receiver can impose both actual and perceived complications and costs for a network operator.

The number of nodes requiring accurate time references is increasing, and it can therefore be expensive to upgrade the whole transport network to support protocols such a PTP. Thus, although a grand master node in a Radio Access Network (RAN) enables a cost efficient way to provide a PTP grand master node at the edge of a transport network, it has a disadvantage of requiring a GNSS receiver connected to it. Summary

According to some embodiments there is provided a method in a master node for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized. The method comprises causing a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only. The method comprises distributing the dummy time reference to the plurality of nodes in the subnetwork.

According to another aspect, there is provided a method in a slave node of a subnetwork of nodes of a communication network. The method comprises receiving a time reference, and using the time reference to perform phase synchronization with one or mode other nodes in the subnetwork. The method comprises determining if the time reference contains a watermark indicating that the time reference is a dummy time reference, and, if so, limiting the use of the time reference to synchronize only with other nodes within the subnetwork.

According top another aspect, there is provided a master node for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized. The master node comprises a processor and a memory, said memory containing instructions executable by said processor. The master node is operative to cause a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only. The master node is operative to distribute the dummy time reference to the plurality of nodes in the subnetwork.

According to another aspect, there is provided a slave node of a subnetwork of nodes of a communication network, the slave node comprising a processor and a memory, said memory containing instructions executable by said processor. The slave node is operative to receive a time reference, and use the time reference to perform phase synchronization with one or mode other nodes in the subnetwork. The slave node is operative to determine if the time reference contains a watermark indicating that the time reference is a dummy time reference, and, if so, limit the use of the time reference to synchronize only with other nodes within the subnetwork.

According to another aspect there is provided a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method as described herein, and as defined in appended claims 1 to 16.

According to another aspect there is provided a computer program product comprising a computer-readable medium with the computer program as described above.

Brief Description of the Drawings

Figure 1 shows an example of a method in a master node according to an embodiment;

Figure 2 shows an example of a method in a slave node according to an embodiment;

Figure 3 shows an example of a subnetwork according to an embodiment;

Figure 4 shows an example of a method according to an embodiment;

Figure 5 shows an example of a message filed in a precision time protocol, PTP;

Figure 6 shows an example of a master node according to an embodiment;

Figure 7 shows an example of a slave node according to an embodiment;

Figure 8 illustrates a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments;

Figure 9 illustrates a host computer communicating via a base station with a user equipment over a partially wireless connection in accordance with some embodiments; Figure 10 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments;

Figure 1 1 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments;

Figure 12 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments; and

Figure 13 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments.

Detailed Description

The following sets forth specific details, such as particular embodiments for purposes of explanation and not limitation. But it will be appreciated by one skilled in the art that other embodiments may be employed apart from these specific details. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers that are specially adapted to carry out the processing disclosed herein, based on the execution of such programs. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understood to comprise one or more processors, one or more processing modules or one or more controllers, and the terms computer, processor, processing module and controller may be employed interchangeably. When provided by a computer, processor, or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, the term“processor” or“controller” also refers to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

Although the description is given for a wireless device, or user equipment (UE), it should be understood by the skilled in the art that“UE” is a non-limiting term comprising any mobile or wireless terminal, device or node equipped with a radio interface allowing for at least one of: transmitting signals in uplink (UL) and receiving and/or measuring signals in downlink (DL). A UE herein may comprise a UE (in its general sense) capable of operating or at least performing measurements in one or more frequencies, carrier frequencies, component carriers or frequency bands. It may be a“UE” operating in single- or multi-radio access technology (RAT) or multi-standard mode. As well as“UE”, the terms“mobile station” (“MS”),“mobile device” and“terminal device” may be used interchangeably in the following description, and it will be appreciated that such a device does not necessarily have to be‘mobile’ in the sense that it is carried by a user. Instead, the term“mobile device” encompasses any device that is capable of communicating with communication networks that operate according to one or more mobile communication standards, such as the Global System for Mobile communications, GSM, UMTS, Long- Term Evolution, LTE, IEEE 802.11 or 802.16, etc.

The description involves communication between a UE and a radio access network, which typically includes multiple radio access nodes. In the specific example given, the radio access nodes take the form of eNodeBs (eNBs), as defined by 3GPP, or gNodeBs (gNBs) as utilised in the future standards expected to meet the 5G requirements. However, it will be appreciated that the concepts described herein may involve any radio access nodes. Moreover, where the following description refers to steps taken in or by a radio access node, this also includes the possibility that some or all of the processing and/or decision making steps may be performed in a device that is physically separate from the radio antenna of the radio access node, but is logically connected thereto. Thus, where processing and/or decision making is carried out“in the cloud”, the relevant processing device is considered to be part of the radio access node for these purposes.

Embodiments disclosed herein relate to methods and apparatus for providing synchronization within a subnetwork comprising a plurality of nodes, for example, time and phase synchronization without using an absolute time reference.

The embodiments described herein are based on providing a subnetwork of nodes of a communications network that are phase synchronized, whereby the subnetwork of nodes may also be referred to as an isolated area or island, such that the subnetwork of network nodes (or island of nodes) only need their relative phase to be synchronized, As such, a node providing time synchronization to the subnetwork (or island), for example a master node (also referred to herein as a grand master node), does not need to be synchronized using an accurate time reference, such as a Global Navigation Satellite System, GNSS.

Figure 1 shows a method according to an embodiment, the method being in a master node for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized. The master node may comprise, for example, a grand master node of the subnetwork.

The method comprises causing a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only, step 101. The method comprises distributing the dummy time reference to the plurality of nodes in the subnetwork, step 103. As will be described in greater detail below, the watermark can be an explicit or implicit watermark for informing other nodes, such as slave nodes, that the time reference is a dummy time reference.

In some examples the step of causing the dummy time reference to be generated comprises the step of generating the dummy time reference locally at the master node. In other examples, the step of causing the dummy time reference to be generated comprises triggering a remote node to generate the dummy time reference, including for example a cloud based node.

According to some embodiments the dummy time reference is different to an absolute time reference corresponding to a current time reference value. That is, the dummy time reference is different to an absolute or accurate time reference that is provided by a time referencing system such as GNSS.

In some embodiments the dummy time reference comprises a future time reference value compared to a current time reference value, the future time reference value acting as the watermark. In such embodiments the mere fact that the dummy time reference is a time reference corresponding to a time in the future is sufficient to act as a watermark for signalling to a receiving node within the subnetwork of nodes that the time reference should only be used within the subnetwork, i.e. the watermark thus being an implicit form of watermark.

To enable a receiver to determine that a received time reference is indeed a dummy time reference, the method performed in the master node may comprise selecting the future time reference value to be a time value beyond a threshold value into the future, e.g. beyond a certain point of time in the future.

For example, in some embodiments the future time reference value comprises a year component which is subsequent to the present year. Thus, upon receiving a time reference signal with a time value that corresponds to a subsequent year, a receiver is able to quickly determine that the time reference is a dummy time reference that should only be used within the subnetwork of nodes. In other words, a slave node can recognize that it is synchronized using an arbitrary time of a grand master node, i.e. because the received year has an abnormal value. The year may be calculated arbitrarily at the master node.

According to one embodiment the method comprises generating the future time reference value by setting a most significant byte of a time reference value. By setting the most significant byte in this way, this ensures that the future time reference value is sufficiently into the future, for example beyond a certain threshold.

The method may set the time transmitted from the master node to a time within the allowed time span according to the IEEE 1588 specification, but choose a point in time far into the future. The IEEE 1588 specification relates to a precision clock synchronization protocol for networked measurement and control systems.

In some embodiments, the dummy time reference comprises a special domain number, the special domain number acting as the watermark for indicating that the dummy time reference is a time reference for use with nodes within the subnetwork only.

It is noted that the step of distributing the dummy time reference may comprise distributing the dummy time reference using a communication protocol which is frequency locked with the master node. For example, in one embodiment the step of distributing comprises using a precision time protocol, PTP, to distribute the dummy time reference. In another embodiment, the step of distributing comprises using a network time protocol, NTP, to distribute the dummy time reference. In other embodiments, the step of distributing comprises using a synchronous ethernet protocol, SyncE, to distribute the dummy time reference.

The dummy time reference may include one or more of dummy clock class information, dummy clock accuracy information, and dummy time traceability information.

In one example the dummy clock class information is set to a value of 6. This means that the time reference is synchronized to a Global Positioning System, GPS. In one example the dummy clock accuracy information is set to a value of 0x21 , relating to a clock accuracy enumeration specified for PTP in the IEEE 1588 standard, version 2. That is, this means that the time is accurate to within 100ns.

In one example, the dummy time traceable information is set to a“true” value.

Therefore, according to such an example as described above, if a slave or receiver node receives a time reference with a clock class of 6 and clock accuracy of 0x21 from the master node, this can be used by a slave or receiver node to provide time synchronization within the subnetwork, and to allow nodes within the subnetwork to be phase synchronized with one another.

It is noted that the master node can be configured to selectively operate in this mode of operation, for example whereby the steps of causing a dummy time reference to be generated, and distributing the dummy time reference, are performed when the master node is activated to operate in a localised time synchronisation mode of operation, in which nodes of the subnetwork are to be synchronized locally with one another.

Figure 2 shows a method according to another embodiment, in a slave node of a subnetwork of nodes of a communication network.

The method comprises receiving a time reference, step 201. The method comprises using the time reference to perform phase synchronization with one or mode other nodes in the subnetwork, step 203.

The method comprises determining if the time reference contains a watermark indicating that the time reference is a dummy time reference, and, if so, limiting the use of the time reference to synchronize only with other nodes within the subnetwork, step 205.

As mentioned above with reference to Figure 1 , in some embodiments the dummy time reference may comprise a watermark in the form of a time value that is a future time value, which is different to a current time. In such embodiments the method in the slave node may comprise determining whether the received time reference comprises a time reference value above a threshold value into the future, and, if so, determining that the time reference is a dummy time reference for use within the subnetwork only.

In another embodiment, the dummy time reference may comprise a watermark in the form of a special domain number. In such embodiments the method in the slave node may comprise determining whether the received time reference comprises a special domain number, and, if so, determining that the time reference is a dummy time reference for use within the subnetwork only.

When the slave node determines that the received time reference is indeed a dummy time reference, the method in the slave node may comprise, for example, restricting the forwarding of messages to other nodes within the subnetwork, i.e. if it is determined that the received time reference is a dummy time reference. In this way an operator is able to ensure that the subnetwork does not grow into another time synchronized network, by configuring the network so that none of the dummy or fake time references slip outside the subnetwork.

Figure 3 shows an example of a subnetwork 301 according to an embodiment, the subnetwork comprising a plurality of nodes, including a master node 307, e.g. a grand master node, and a plurality of slave nodes 305. The master node 307 is coupled with a network 31 1 which provides frequency synchronization, for example a PTP/IP network. The network 31 1 may comprise, for example, various network nodes, including Sync Supply Units and Sync supply equipment (SSU/BITS).

It is noted that the nodes 305, 307 in the subnetwork 301 may comprise any form of network node, including for example networked devices such as UEs as described herein, or loT devices.

Figure 3 shows that the master node 307 is configured to provide island time synchronization 309, ITS, within the subnetwork 301. The master node 307 may be configured to generate dummy time references as mentioned in any of the examples descried earlier with reference to Figure 1. Slave nodes 305, upon receiving a time reference from the master node 307, are configured to automatically detect whether the time reference contain a watermark indicating that the time reference is a dummy time reference for use only within the subnetwork, for providing phase synchronization between the plurality of nodes within the subnetwork. The network 303 illustrates how the grand master node 307 can communicate with the slave node 305i via a PTP network, as well as directly as shown between grand master 307 and slave node 305₂.

Figure 4 shows an example of a system according to an embodiment. Block 401 shows a master node, for example a grant master node, synchronized to frequency within a subnetwork of nodes, i.e. within an island area, and for example synchronized to frequency using GNSS. To be synchronized in frequency the master node may use a communication protocol, such as PTP/IP, NTP or SyncE reference.

Blocks 402, 403 and 404 of Figure 4 summarize the method that may be performed at the master node, to configure a subnetwork such that time synchronization is provided without requiring an exact synchronization with an absolute time reference such as GNSS. This method of synchronization, and that described in the method of Figure 1 above, may be referred to as an“Island Time Synchronization”, ITS, mode of operation, to provide time synchronization to an island that does not need to be synchronized from GNSS.

Thus, in block 402 the system is configured by the master node to be in the ITS mode.

In block 403 the master node is configured to send a dummy or fake time protocol message, such as PTP, NTP or SyncE message, to slave nodes, for example as described in the embodiments above. This comprises the master node sending a dummy time reference to the slave nodes, comprising an arbitrary time.

For an example where a dummy PTP message is sent, according to one embodiment there are first, second and third types of dummy or fake fields in the PTP message. The master node may be configured to change PTP announce messages such that they appears as if the master node (Grand Master) is time locked although frequency locked. For example, the first, second and third fields may comprise Clock Class, Clock Accuracy and Time Traceable fields. As such, the master node sends dummy clock class, dummy clock accuracy, and dummy time traceable information. For example, the dummy clock class may be set to a value of 6, the dummy clock accuracy to a value less than 0x21 (corresponding to less than 100ns), and the dummy time traceable information set to a value“true”. In some examples the distributed“time” is locally created by the master node, while in other embodiments the master node triggers this time to be generated elsewhere, for example in a remote node.

Block 405 shows a slave node locked to a time synchronization message received from the master node.

Block 406 shows the slave node automatically detecting from a watermark that the time reference is locked by an arbitrary time of the master node. As such, although the slave node can use the received time reference for phase synchronization with other nodes within the subnetwork, the slave node can be configured to limit the use of the time reference to within the subnetwork.

Figure 5 shows and example of a message field that may be used, for example, in an announce message of PTP, to indicate whether an island time synchronization, ITS, mode of operation is to be employed. In the example a single bit is used to indicate whether the ITS mode is activated or not. It is noted, however, that other fields or mechanisms may be used to activate or deactivate the ITS mode. Such a field may be used as an explicit watermark for indicating that an ITS mode is being used. In other words, the bit is set to indicate ITS mode.

Figure 6 shows a master node 600 according to an embodiment, for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized. The master node comprises a processor 601 and a memory 603, wherein the memory 603 contains instructions executable by the processor 601.

The master node 600 is operative to cause a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only. The master node 600 is further operative to distribute the dummy time reference to the plurality of nodes in the subnetwork.

The master node 600 may be further operative to perform any of the methods as defined above in relation to a master node.

Figure 7 shows an example of an embodiment relating to a slave node 700 of a subnetwork of nodes of a communication network. The slave node 700 comprises a processor 701 and a memory 703, the memory 703 containing instructions executable by the processor 701.

The slave node 700 is operative to receive a time reference, and use the time reference to perform phase synchronization with one or mode other nodes in the subnetwork. The slave node is further operative to determine if the time reference contains a watermark indicating that the time reference is a dummy time reference, and, if so, limit the use of the time reference to synchronize only with other nodes within the subnetwork.

The slave node 700 may be further operative to perform any of the methods as defined above in relation to the slave node.

According to another embodiment, there is provided a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method as described herein, and as defined in the appended claims.

According to another embodiment, there is provided a computer program product comprising a computer-readable medium with the above computer program.

From the embodiments described herein it can be seen that a subnetwork runs features that enable time synchronization to be deployed so that the subnetwork does not interface with any neighbor networks. The area or island corresponding to the subnetwork does not therefore have to be synchronized to absolute time. It is sufficient to frequency synchronize a local master node, such as a PTP grand master node, which send out or distributes PTP messages with dummy or fake announcements, telling other nodes in the subnetwork that the grand master node is time locked.

The grand master node is locked to frequency clock sources (e.g. PTP over IP, NTP, SyncE) without GNSS. In the case of the ITS mode being activated, the slave nodes locked to time synchronization receive fake PTP messages containing the faked time information. All the nodes located within the subnetwork (or island) are synchronized to the arbitrary time of the grand master node without requiring an absolute time, and can thus be phase synchronized to each other.

A benefit of this is that the need for GNSS receivers can be reduced, thus reducing the expense of purchasing such GNSS receivers, and reducing the expense of installing and maintaining such GNSS receivers. The subnetwork (or island) only requires local phase synchronization.

The embodiments therefore provide a method or algorithm that can distribute a common phase in the island subnetwork, for example by distributing a time reference signal using an arbitrary time, and using a watermark within the time reference to enable nodes to recognize this mode of operation.

A master node, such as a grand master node, as described herein, when used in a random access network, RAN, makes it possible to distribute timing at the edge of the network to neighbor base stations.

As mentioned in the embodiments above, different protocols may be used to distribute the dummy time references. Embodiments using PTP for time synchronization provide an advantage in that, in addition to reducing the need for GNSS receivers, which are expensive to purchase, install and maintain, PTP also provides a solution with convenient interoperability.

It is noted that there is no requirement on intermediate or end nodes to change their behavior due to the island mode of operation, thus making the embodiments suitable for legacy applications. With the function described in the embodiments herein, the slave nodes will be phase synchronized to each other, but they will not necessarily be aware the master node is faking it is locked to an accurate time reference, such as GNSS. In such a scenario the slave nodes would thus not be able to report to a network operation center that they are synchronized in the island mode.

However, the watermark described in the embodiments herein provides a method to distribute information that the master node is operating in an island synchronization mode. This watermark information may also be transmitted to networks that do not have functions to detect the island synchronization mode. As such, a watermark, e.g. provided in the PTP protocol, provides a piece of information that can pass intermediate nodes without being discarded or modified by intermediate nodes.

Figure 8 illustrates a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments.

With reference to Figure 8, in accordance with an embodiment, a communication system includes telecommunication network 1310, such as a 3GPP-type cellular network, which comprises access network 131 1 , such as a radio access network, and core network 1314. Access network 1311 comprises a plurality of base stations 1312a, 1312b, 1312c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 1313a, 1313b, 1313c. Each base station 1312a, 1312b, 1312c is connectable to core network 1314 over a wired or wireless connection 1315. A first UE 1391 located in coverage area 1313c is configured to wirelessly connect to, or be paged by, the corresponding base station 1312c. A second UE 1392 in coverage area 1313a is wirelessly connectable to the corresponding base station 1312a. While a plurality of UEs 1391 , 1392 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 1312.

Telecommunication network 1310 is itself connected to host computer 1330, which may be embodied in the hardware and/or software of a standalone server, a cloud- implemented server, a distributed server or as processing resources in a server farm. Host computer 1330 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections 1321 and 1322 between telecommunication network 1310 and host computer 1330 may extend directly from core network 1314 to host computer 1330 or may go via an optional intermediate network 1320. Intermediate network 1320 may be one of, or a combination of more than one of, a public, private or hosted network; intermediate network 1320, if any, may be a backbone network or the Internet; in particular, intermediate network 1320 may comprise two or more sub-networks (not shown).

The communication system of Figure 8 as a whole enables connectivity between the connected UEs 1391 , 1392 and host computer 1330. The connectivity may be described as an over-the-top (OTT) connection 1350. Host computer 1330 and the connected UEs 1391 , 1392 are configured to communicate data and/or signaling via OTT connection 1350, using access network 131 1 , core network 1314, any intermediate network 1320 and possible further infrastructure (not shown) as intermediaries. OTT connection 1350 may be transparent in the sense that the participating communication devices through which OTT connection 1350 passes are unaware of routing of uplink and downlink communications. For example, base station 1312 may not or need not be informed about the past routing of an incoming downlink communication with data originating from host computer 1330 to be forwarded (e.g., handed over) to a connected UE 1391. Similarly, base station 1312 need not be aware of the future routing of an outgoing uplink communication originating from the UE 1391 towards the host computer 1330.

Figure 9 illustrates a host computer communicating via a base station with a user equipment over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Figure 9. In communication system 1400, host computer 1410 comprises hardware 1415 including communication interface 1416 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of communication system 1400. Host computer 1410 further comprises processing circuitry 1418, which may have storage and/or processing capabilities. In particular, processing circuitry 1418 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. Host computer 1410 further comprises software 1411 , which is stored in or accessible by host computer 1410 and executable by processing circuitry 1418. Software 141 1 includes host application 1412. Host application 1412 may be operable to provide a service to a remote user, such as UE 1430 connecting via OTT connection 1450 terminating at UE 1430 and host computer 1410. In providing the service to the remote user, host application 1412 may provide user data which is transmitted using OTT connection 1450.

Communication system 1400 further includes base station 1420 provided in a telecommunication system and comprising hardware 1425 enabling it to communicate with host computer 1410 and with UE 1430. Hardware 1425 may include communication interface 1426 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of communication system 1400, as well as radio interface 1427 for setting up and maintaining at least wireless connection 1470 with UE 1430 located in a coverage area (not shown in Figure 9) served by base station 1420. Communication interface 1426 may be configured to facilitate connection 1460 to host computer 1410. Connection 1460 may be direct or it may pass through a core network (not shown in Figure 9) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, hardware 1425 of base station 1420 further includes processing circuitry 1428, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. Base station 1420 further has software 1421 stored internally or accessible via an external connection.

Communication system 1400 further includes UE 1430 already referred to. Its hardware 1435 may include radio interface 1437 configured to set up and maintain wireless connection 1470 with a base station serving a coverage area in which UE 1430 is currently located. Hardware 1435 of UE 1430 further includes processing circuitry 1438, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. UE 1430 further comprises software 1431 , which is stored in or accessible by UE 1430 and executable by processing circuitry 1438. Software 1431 includes client application 1432. Client application 1432 may be operable to provide a service to a human or non-human user via UE 1430, with the support of host computer 1410. In host computer 1410, an executing host application 1412 may communicate with the executing client application 1432 via OTT connection 1450 terminating at UE 1430 and host computer 1410. In providing the service to the user, client application 1432 may receive request data from host application 1412 and provide user data in response to the request data. OTT connection 1450 may transfer both the request data and the user data. Client application 1432 may interact with the user to generate the user data that it provides.

It is noted that host computer 1410, base station 1420 and UE 1430 illustrated in Figure 9 may be similar or identical to host computer 1330, one of base stations 1312a, 1312b, 1312c and one of UEs 1391 , 1392 of Figure 8, respectively. This is to say, the inner workings of these entities may be as shown in Figure 9 and independently, the surrounding network topology may be that of Figure 8.

In Figure 9, OTT connection 1450 has been drawn abstractly to illustrate the communication between host computer 1410 and UE 1430 via base station 1420, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from UE 1430 or from the service provider operating host computer 1410, or both. While OTT connection 1450 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

Wireless connection 1470 between UE 1430 and base station 1420 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to UE 1430 using OTT connection 1450, in which wireless connection 1470 forms the last segment. A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring OTT connection 1450 between host computer 1410 and UE 1430, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring OTT connection 1450 may be implemented in software 141 1 and hardware 1415 of host computer 1410 or in software 1431 and hardware 1435 of UE 1430, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which OTT connection 1450 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 141 1 , 1431 may compute or estimate the monitored quantities. The reconfiguring of OTT connection 1450 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect base station 1420, and it may be unknown or imperceptible to base station 1420. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating host computer 1410’s measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that software 141 1 and 1431 causes messages to be transmitted, in particular empty or‘dummy’ messages, using OTT connection 1450 while it monitors propagation times, errors etc.

Figure 10 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments.

Figure 10 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 11 and 12. For simplicity of the present disclosure, only drawing references to Figure 10 will be included in this section. In step 1510, the host computer provides user data. In substep 1511 (which may be optional) of step 1510, the host computer provides the user data by executing a host application. In step 1520, the host computer initiates a transmission carrying the user data to the UE. In step 1530 (which may be optional), the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1540 (which may also be optional), the UE executes a client application associated with the host application executed by the host computer.

Figure 11 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments. Figure 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 11 and 12. For simplicity of the present disclosure, only drawing references to Figure 11 will be included in this section. In step 1610 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In step 1620, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1630 (which may be optional), the UE receives the user data carried in the transmission.

Figure 12 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments.

Figure 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 11 and 12. For simplicity of the present disclosure, only drawing references to Figure 12 will be included in this section. In step 1710 (which may be optional), the UE receives input data provided by the host computer. Additionally or alternatively, in step 1720, the UE provides user data. In substep 1721 (which may be optional) of step 1720, the UE provides the user data by executing a client application. In substep 1711 (which may be optional) of step 1710, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in substep 1730 (which may be optional), transmission of the user data to the host computer. In step 1740 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure. Figure 13 illustrates methods implemented in a communication system including a host computer, a base station and a user equipment in accordance with some embodiments.

Figure 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 11 and 12. For simplicity of the present disclosure, only drawing references to Figure 13 will be included in this section. In step 1810 (which may be optional), in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In step 1820 (which may be optional), the base station initiates transmission of the received user data to the host computer. In step 1830 (which may be optional), the host computer receives the user data carried in the transmission initiated by the base station.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as read-only memory (ROM), random-access memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim,“a” or“an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

1. A method in a master node for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized, the method comprising:

causing a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only; and

distributing the dummy time reference to the plurality of nodes in the subnetwork.

2. A method as claimed in claim 1 , wherein causing the dummy time reference to be generated comprises the step of generating the dummy time reference locally at the master node.

3. A method as claimed in claim 1 or 2, wherein the dummy time reference is different to an absolute time reference corresponding to a current time reference value.

4. A method as claimed in any one of the preceding claims, wherein the dummy time reference comprises a future time reference value compared to a current time reference value, the future time reference value acting as the watermark.

5. A method as claimed in claim 4, wherein the future time reference value is a time value beyond a threshold value into the future.

6. A method as claimed in claim 4 or 5, wherein the future time reference value comprises a year component which is subsequent to the present year.

7. A method as claimed in claim 4 or 5, further comprising generating the future time reference value by setting a most significant byte of a time reference value.

8. A method as claimed in claim 1 or 2, wherein the dummy time reference comprises a special domain number, the special domain number acting as the watermark for indicating that the dummy time reference is a time reference for use with nodes within the subnetwork only.

9. A method as claimed in any one of the preceding claims, wherein the step of distributing comprises distributing the dummy time reference using a communication protocol which is frequency locked with the master node.

10. A method as claimed in claim 9, wherein the step of distributing comprises using: a precision time protocol, PTP, to distribute the dummy time reference; or a network time protocol, NTP, to distribute the dummy time reference; or a synchronous ethernet protocol, SyncE, to distribute the dummy time reference.

11. A method as claimed in any one of the preceding claims, wherein the dummy time reference includes one or more of:

dummy clock class information;

dummy clock accuracy information; and

dummy time traceability information.

12. A method as claimed in claim 11 , wherein:

the dummy clock class information is set to a value 6;

the dummy clock accuracy information is set to a value 0x21 ; and the dummy time traceable information is set to a true value.

13. A method as claimed in any one of the preceding claims, wherein the steps of causing and distributing are performed when the master node is activated to operate in a localised time synchronisation mode of operation, in which nodes of the subnetwork are to be synchronised.

14. A method in a slave node of a subnetwork of nodes of a communication network, the method comprising:

receiving a time reference;

using the time reference to perform phase synchronization with one or mode other nodes in the subnetwork; and

determining if the time reference contains a watermark indicating that the time reference is a dummy time reference, and, if so, limiting the use of the time reference to synchronize only with other nodes within the subnetwork.

15. A method as claimed in claim 14, further comprising:

determining whether the received time reference comprises a time reference value above a threshold value into the future, and, if so, determining that the time reference is a dummy time reference for use within the subnetwork only; or

determining whether the received time reference comprises a special domain number, and, if so, determining that the time reference is a dummy time reference for use within the subnetwork only.

16. A method as claimed in claim 14 or 15, further comprising:

restricting the forwarding of messages to other nodes within the subnetwork, if it is determined that the received time reference is a dummy time reference.

17. A master node for providing time synchronization information in a subnetwork of nodes of a communications network, for enabling nodes of the subnetwork to become phase synchronized, the master node comprising a processor and a memory, said memory containing instructions executable by said processor, whereby said master node is operative to:

cause a dummy time reference to be generated, the dummy time reference comprising a watermark for indicating that the dummy time reference is for use within the subnetwork only; and

distribute the dummy time reference to the plurality of nodes in the subnetwork.

18. A master node as claimed in claim 17, wherein the master node is further operative to perform the method as defined in any one of claims 2 to 13.

19. A slave node of a subnetwork of nodes of a communication network, the slave node comprising a processor and a memory, said memory containing instructions executable by said processor, whereby said slave node is operative to:

receive a time reference;

use the time reference to perform phase synchronization with one or mode other nodes in the subnetwork; and determine if the time reference contains a watermark indicating that the time reference is a dummy time reference, and, if so, limit the use of the time reference to synchronize only with other nodes within the subnetwork.

20. A slave node as claimed in claim 19, wherein the slave node is further operative to perform the method as defined in any one of claims 14 to 16.

21. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 1 to 16.

22. A computer program product comprising a computer-readable medium with the computer program as claimed in claim 21.