Contactless calibration

Abstract

The invention relates to a method and a device for enabling contactless local calibration of a time-dependent device (N1) using a mobile calibration unit (MCD) provided with a local reference clock. The method comprises moving the MCD within a predetermined distance from N1 (S105B), and establishing a temporary time transfer session for transmitting and / or receiving timing signals of the local clocks of N1 and RC (S101A, S101B, S101C), and determining a timing data offset between the local clocks of N1 and RC (S103) for use in calibrating or verifying timing characteristics of N1 (S104).

Description

Technical Field

[0001] The present invention relates to the field of calibration of time-dependent devices and nodes. More particularly, the proposed technology relates to a method and device and is used to provide contactless calibration of timing characteristics of a time-dependent device or node. Background Art

[0002] Network synchronization (i.e., synchronization between nodes in a network) is often critical for functions within the network. For example, a packet-based network may require frequency and time synchronization (phase alignment) between nodes for successful packet delivery, where operators can provide synchronization services to their customers. For long-distance communications, such as in wireless telecommunications networks, network nodes need to be synchronized with each other, after which terminals in the network are synchronized to corresponding network nodes. As an example, in an implementation of the radio access technology New Radio (NR) for implementing 5G communications, the terminal will be connected to several base stations or network nodes to achieve communication. Therefore, the need for network synchronization between different nodes (such as base stations in 5G) in the network (used in many industries including media, finance, automation, power grids and mobile networks, and time-related applications in many other fields) has increased. Synchronization measurements can include phase measurements, phase deviations, and analysis of phase time interval errors, fractional frequency offsets, maximum time interval errors (MTIEs), and time deviations (TDEVs) taking into account reference signals.

[0003] The network synchronization task in the network-based approach consists of distributing a reference signal from a primary reference clock (PRC) to all network elements that need synchronization. The method used to propagate the reference signal in the network is typically a master-slave approach, i.e. a hierarchical model in which a slave clock must be subordinate to a clock of higher (or equal) stability. The synchronization information is transmitted through the network via a synchronization network connection. The synchronization network connection is typically unidirectional and is typically point-to-multipoint. A centralized timing network architecture or a distributed timing network architecture (e.g., GPS) can be used.

[0004] GNSS or Global Navigation Satellite System is a generic name for a group of artificial satellites that transmit position and timing data from their high orbits. GNSS provides the basic technology for time synchronization masters to enable global distribution of a trackable reference to Coordinated Universal Time (UTC). The Global Positioning System (GPS) is just one of many different satellite groups that can provide this data. GPS or other GNSS satellites include three or four atomic clocks that are monitored and controlled to be highly synchronized and traceable to national and international standards (i.e., UTC). For time synchronization, a GPS signal processed by a local master clock, time server, or master reference is received and delivered (distributed) to "slaves" and other devices, systems, or networks so that their "local clocks" are also synchronized with UTC. Typical accuracy ranges from better than 1 microsecond to several milliseconds, depending on the synchronization protocol. The process of synchronizing with GPS can provide the accuracy of an atomic clock without the need for a local atomic clock. Nevertheless, it is sometimes desirable to use a local atomic clock as a long-term backup solution for GPS loss, whether in the case of weather-related outages, GPS interference, or other scenarios.

[0005] Time transfer (relative and absolute) describes the mechanisms used to compare time and frequency measurements from one location to another. Time transfer is a scheme where multiple sites share a precise reference time. Various techniques have been developed to transfer reference clock synchronization from one point to another, often over long distances. Time transfer can be used for time synchronization between different entities or nodes in a network, which is critical to the functionality of the network.

[0006] In a one-way time transfer system, one end transmits its current time to one or more receivers over some communication channel. The advantage of one-way systems is that they can be technically simple and serve many receivers, since the transmitter is unaware of the receivers. The main disadvantage of one-way time transfer systems is that, except in some advanced systems, the propagation delay of the communication channel is still not compensated.

[0007] In a two-way time transfer system, neighboring nodes will not only send but also receive messages from each other, so two one-way time transfers are performed to determine the difference between the remote clock (neighboring clock) and the local clock. The sum of these time differences is the round-trip time (RTT) between the two nodes. It is usually assumed that the delay is evenly distributed between the directions between the peer devices. Under this assumption, half of the RTT is the propagation delay to be compensated when estimating delay compensation. The disadvantage is that the two-way propagation delay must be measured and used to calculate the delay compensation / correction. In order to calculate the correct delay and determine the compensation, information such as timestamps, time difference measurements, correction factors, and various statistical information between the nodes involved in the two-way time transfer is required.

[0008] Typically, network-based distribution is done from one or a few central sites to a large number of destination sites. Communication node to node can be done over the air or by wire. In networks with several paths, redundancy can be implemented. However, as the number of hops between the node and the clock source node increases, the accuracy becomes lower due to the number of hops passed due to jitter (because of other traffic). In addition, asymmetric delays affect the accuracy, and for some applications, the accuracy is not good enough.

[0009] Bidirectional time transfer mechanisms are the basis of all packet time transfer protocols such as the Network Time Protocol (NTP) and IEEE 1588, the Precision Time Protocol (PTP). They generally assume path symmetry and path consistency, although IEEE 1588 has the concept of asymmetry correction. However, the correction values ​​are not measured dynamically - they need to be configured statically, i.e., by calibrating the nodes with respect to the desired timing characteristics (such as asymmetry in this case).

[0010] Figure 1 5 is a schematic diagram of an exemplary prior art network. Network 5 schematically illustrates a typical 5G mobile network here, and includes a radio access network (RAN) with a separated logical architecture. In such a RAN, functions in the RAN domain are managed by a group of radio units (RU) connected to a corresponding distributed unit (DU). The DU is then typically associated with a centralized unit (CP). In the exemplary network 5, two RUs 60 each serving a corresponding cell are associated with the DU 70. The DU 70 can communicate with the CP (not shown). Connected to the RAN 5, the transport network 80 is formed by a plurality of interconnected routers 81, and then forms a transport domain 40. The transport network 80 can support PTP (or some other time transfer protocol). The synchronization method for providing appropriate frequency synchronization and time alignment of a radio network (such as RAN 5) can be implemented in the RAN domain 30, the transport domain 40, or as a combination of technologies in the two domains, which may be required to create a robust and reliable solution. In the prior art, a synchronization method such as using GNSS and air synchronization (OAS) can be implemented in the RAN domain 30. That is, the relative time / timing error between adjacent base stations RU 60 can be compensated using, for example, OAS. Figure 1 Schematically illustrated by arrow 61 in FIG. 1 . The synchronization method implemented in the transport domain 40 generally needs to utilize PTP and other timing support from the network to meet the relevant time synchronization requirements. Preferably, the PTP network is fed from the T-GM functions in geographically redundant telecommunication master equipment (T-GM) 91, 92 or GNSS receivers and one or more base stations (RU 60 or DU 70) or routers 81. Redundancy can be achieved by distributing timing through the same physical redundant topology used for user traffic. Figure 1In the embodiment, the DU 70 is also provided with a local GPS receiver 10b which receives the time from the GPS 10a. Timing distribution via a transmission network may be provided as a supplement to such a local GPS receiver.

[0011] The use of GNSS receivers (such as GPS receivers) physically connected to the site is the most common technique used for site calibration / synchronization today. This common way of providing accurate time and frequency synchronization is by obtaining accurate clocks from GPS and other GNSS systems that are directly input into nodes in the communication network (e.g., by installing GPS receivers at transmitter sites). Although GPS will deliver the required accuracy to GPS receivers, they can be easily jammed, intentionally or accidentally, or fail for other reasons, such as equipment failure, which makes this method unreliable due to its susceptibility to interference or jamming.

[0012] Therefore, using GNSS / GPS systems as the primary and only source of time synchronization or calibration in network nodes poses a major risk to critical infrastructure and is not allowed in many countries.

[0013] In order to maintain time synchronization between nodes, such as base stations in a telecommunication network, e.g. Figure 1 As shown, the base stations can be synchronized with each other or to a common time base, for example, to a GPS system time. Typically, after the base station installation is complete, each base station must be individually calibrated with special test equipment. The result of this calibration process is a time offset of the local time (e.g., relative to the time base) of each base station. These time offsets are stored in a database accessible during the calculation of time-related variables in the network. Any subsequent hardware changes in the base station require recalibration of the base station and updating of the database. Calibration and recalibration of nodes in the network represent an expensive process.

[0014] An important and widespread issue in time and frequency transfer methods is how to handle asymmetry, which means that the transmission delay is different in the receiving and sending directions between the source and the destination. In a time transfer network, the local clocks of the base stations or network nodes can be calibrated link by link by measuring the individual link delays based on the local clocks and the RTT. However, most known protocols for transferring time synchronization assume that the link delay is equal to RTT / 2 and have difficulty handling asymmetric delays, i.e., the case where the delay from a first node A to a second node B is different from the delay from the second node B to the first node A. If this delay is a static delay, this delay can be calibrated and handled thereafter. Asymmetry may also arise dynamically during operation and to some extent undermine many two-way time transfer protocols, and therefore there is a need to at least improve the ability to handle such delay asymmetry.

[0015] Conventional calibration of nodes in, for example, a telecommunications network may involve physical access to a telecommunications company (Telco) site, including access to an out-of-door structure (e.g., the top of a cell tower, or inside a building, cabinet, etc.). Calibration at a Telco site may be expensive and complex due to the large number of geographically distributed Telco sites. On-site calibration using physical cables is even more expensive and time-consuming, for example, because it may require personnel to be equipped with keys and / or other devices to access the equipment.

[0016] Telcos sometimes have the option of using Over-the-Air Synchronization (OAS), where the radio transmitters of corresponding (usually adjacent) Telco sites exchange timing information over the air. OAS typically considers frequency synchronization / calibration, rather than absolute time and phase synchronization / calibration. Since it can be assumed that there is no asymmetry in the air over short distances, an already calibrated Telco site can use OAS to calibrate another Telco site that can be reached. However, this means that any calibration errors will be accumulated when multiple sites are calibrated one after another in the chain. The problem with using OAS is that these systems rely on satellite-based clock signals (GPS / GNSS), which can be jammed and spoofed. In addition, OAS also requires built-in functionality within the Telco equipment. Moreover, even if standards are followed, each vendor is often locked to a proprietary solution.

[0017] In summary, there is a need for enhanced methods for calibrating nodes and network synchronization in communication networks. Summary of the invention

[0018] The object of the present disclosure is to provide methods, nodes and systems that are intended to mitigate, alleviate or eliminate the above-mentioned defects and shortcomings in the art, either individually or in any combination. A further object is to simplify the calibration and / or verification of stand-alone time-related devices that are not connected to a network and nodes in a network (such as nodes in a 5G network) to minimize physical access to the stand-alone time-related devices or nodes in the network, which reduces calibration time, is beneficial to security, and also enables calibration of devices or nodes in situations where physical access is limited or undesirable due to radiation, biohazards, etc. The present invention can also be used in areas where calibration using GNSS is not possible due to congestion, deception, invisibility or due to cost issues.

[0019] The present inventive concept relates to an apparatus and method for enabling calibration or verification of timing characteristics in a device or node in a network, such as a radio communication network. This is achieved by locally providing a temporary, wireless or contactless, trusted reference clock by means of a mobile calibration device (MCD) to be used as a timing reference for a local clock of the device or node. This is advantageous in performing calibration of timing characteristics and optionally providing synchronization between nodes in the network.

[0020] Additionally, providing a site or device with temporary or continuous support for a timing reference from an MCD can be advantageously utilized to provide a time / phase / frequency source to the site itself, a sub-portion of the network, and / or the entire network. This is useful in the event that a master clock site is disconnected, or the clock path to the master clock site is disconnected, or any other possible failure or disturbance makes it advantageous or necessary to flip / reverse the direction of time / phase / clock distribution or move the responsibility of acting as a trusted clock source from one site to another.

[0021] According to a first aspect of the inventive concept, a method for calibrating a time-related device N1 relative to a timing characteristic using a mobile calibration device MCD is provided. The method includes providing a reference clock to the MCD, establishing at least one time transfer session between the MCD and N1 and / or a common time reference (CTR). According to an embodiment, the method may further include comparing timing data of the reference clock with timing data from N1, determining a timing data offset between N1 and the MCD, and calibrating or verifying the timing characteristic of N1 based on the determined timing data offset.

[0022] The reference clock or reference time of the MCD may be transferred to N1 using a temporary time transfer session established with a known asymmetry or negligible asymmetry such that the delay in both directions on the link path established between the MCD and N1 is exactly (or sufficiently close to) RTT / 2. This calibration of N1 enables N1's local time to have a nominal zero offset relative to a trusted source (reference time / clock), or a known offset relative to a trusted source, which N1 may then use to compensate for or calibrate timing characteristics, such as any offset in the time information of data streams received and transmitted by N1 in the network.

[0023] According to an embodiment, the time-related device is a node in a network and may be one of a mobile base station, a time transfer device, a digital TV / radio transmitter, a power station in a smart grid, data communication equipment, data terminal equipment and time-related equipment.

[0024] According to an embodiment, the method further comprises moving the MCD within a predetermined distance D from N1. The predetermined distance may be selected to provide a known or negligible transmission time asymmetry in both directions of data transmission between N1 and the MCD, or may be determined based on a technology used to establish a temporary time transfer session between the MCD and N1 (i.e., a wireless communication link or a measurement device used to communicate with N1).

[0025] According to an embodiment, the time transfer session is a one-way time transfer session or a two-way time transfer session.

[0026] According to an embodiment, the time transfer session is performed using a wireless communication link or a contactless type measuring device of said MCD.

[0027] According to an embodiment, the method further comprises determining the predetermined distance. This may be performed based on the wireless communication link or measuring device used. The predetermined distance may alternatively be pre-configured, received via a central node, determined by measuring the signal strength in a time transfer session or a test signal used when approaching N1, obtained using previous experience, or determined via a lookup table.

[0028] According to a second aspect, there is provided a mobile calibration device MCD for calibrating a time-related device N1 with respect to a timing characteristic. The MCD comprises a wireless communication interface for local data transmission between said MCD and N1, a reference clock, a processing circuit system comprising a memory and a processor, the processing circuit system being configured to implement the steps of establishing a time transfer session between said MCD and N1 via said wireless communication interface and providing timing information to N1 from the reference clock.

[0029] According to an embodiment of the MCD, the processing circuit system is further configured to: compare the timing data of the reference clock with the timing data received from N1, determine any timing data offset between N1 and the MCD, and store the timing data of the time transfer session and / or send the timing data offset to calibrate the timing characteristics of N1 based on the determined timing data offset.

[0030] According to an embodiment of the MCD, the MCD further comprises a Global Navigation Satellite System (GNSS) receiver for providing the reference clock,

[0031] According to an embodiment of the MCD, the wireless communication interface is configured for sending and / or receiving signals containing timing data for local data transmission between said MCD and N1.

[0032] According to an embodiment of the MCD, the wireless communication interface comprises one of an optical receiver, an optical transmitter or an optical transceiver, an audio receiver / transceiver, a radio receiver, a radio transmitter or a radio transceiver.

[0033] According to an embodiment of the MCD, the MCD is a vehicle, an unmanned aerial vehicle, or a carrier.

[0034] According to the present invention, the timing characteristic is preferably one of a time offset, a phase offset, a frequency offset, an absolute time offset and an asymmetric offset.

[0035] The node or device as mentioned in this document is selected to be a 5G base station, a gNode B, a 5G small cell, an eNode B, a Node B, a digital TV transmitter, a power station in a smart grid, data communication equipment, data terminal equipment, time-related equipment, TV media production equipment and / or network, radio media production equipment and / or network, military equipment, a sensor station, a radar station, or one of a group of independent time-related equipment combined into an isolated network.

[0036] In other aspects, a computer program comprising computer program code is provided, which, when executed in a network node or a network device, causes the network node or the network device to perform the above method. In yet another aspect, a carrier containing the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer-readable storage medium.

[0037] Further objectives, features and advantages of the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims.Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described in the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and further objects, features and advantages of the present invention will be better understood from the following illustrative and non-limiting detailed description of preferred embodiments of the present invention with reference to the accompanying drawings, in which like reference numerals are used for similar elements, wherein:

[0039] Figure 1 It is a schematic diagram of a typical network configuration and calibration / synchronization in the prior art.

[0040] Figure 2a and Figure 2b The present invention is a concept for use in an embodiment of the present invention. Figure 1 A mobile calibration device (MCD) implemented in the illustrated example network performs contactless local calibration of time-dependent nodes.

[0041] Figure 3a and Figure 3b The present invention is a concept for use in an embodiment of the present invention. Figure 1The MCD implemented in the example network shown performs contactless local calibration of the nodes.

[0042] Figure 4 The present invention is a concept for use in an embodiment of the present invention. Figure 1 The example network shown implements MCD to calibrate nodes.

[0043] Figure 5 A flowchart of an exemplary method for calibrating a device or node using an MCD according to an embodiment of the inventive concept is shown.

[0044] Figure 6 is a schematic block diagram of an example device of the present inventive concept.

[0045] All the figures are schematic, not necessarily to scale, and generally only show components which are necessary in order to elucidate the invention, wherein other components may be omitted or merely suggested. DETAILED DESCRIPTION

[0046] The various aspects of the present disclosure will be described more fully below with reference to the accompanying drawings. However, the apparatus and methods disclosed herein can be implemented in many different forms and should not be construed as being limited to the aspects set forth herein. Throughout the text, the same reference numerals in the accompanying drawings refer to the same elements. The terms used herein are only for the purpose of describing specific aspects of the present disclosure and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to also include plural forms unless the context clearly indicates otherwise.

[0047] In some embodiments, the non-limiting term "node" or "network node" is used here. It should be understood that the term refers to any type of node that can send and / or receive information (such as data and control information) through the network. Where applicable, the node may also sometimes be referred to as a "station" or "base station". The node may also be referred to as a "site" or exist at a site. A physical node is typically an electronic device attached to a network and is capable of creating, receiving or transmitting information through a communication channel. The node may be a node in a 5G wireless communication network, such as a 5G network node, a 5G macro cell (e.g., gNB) or a 5G small cell. The network node may also be a 4G sector base station (e.g., eNB) for 5G communication. The node may be a node in machine-to-machine (M2M) communication, for example, a machine type communication (MTC) node for implementing large-scale MTC and Internet of Things (IoT) applications, or a node for implementing ultra-reliable low-latency communication (URLLC) in, for example, vehicle-to-everything (V2X) applications. The node may also be a node for enhanced 5G mobile broadband (eMBB) applications, providing significantly faster data speeds and greater capacity than previous mobile broadband applications. New applications will include fixed wireless Internet access for homes, outdoor broadcast applications without a broadcast truck, and greater connectivity for people on the move. The node to be calibrated according to the present invention may also be a TV transmitter, including data communication equipment (DCE), such as a modem, router, hub, bridge, controller or switch; or data terminal equipment (DTE), such as a digital telephone handset, printer or host computer. In another example, the node may be a computer terminal connected to a network such as a local area network (LAN), a wide area network (WAN) or the Internet. In yet another example, the node may be a phasor measurement unit (PMU) in a power system.

[0048] It should be understood that the inventive concept is applicable to calibration and / or verification of independent, stand-alone time-related devices that are not connected to a communication network or other network. Examples of independent time-related devices are lighthouses, independent atomic clocks, nuclear facilities, military equipment (optionally in an air-gapped network), surveillance cameras / equipment, equipment in financial trading systems, or other types of equipment that cannot be connected to a communication network, etc. for practical or security reasons.

[0049] The term "network" refers to any type of network through which network nodes can communicate, such as a radio access network (RAN), a local area network (LAN), a wide area network (WAN), or the Internet. The RAN can be a wireless communication network used to implement 5G, for example, by implementing NR. For example, the network can be referred to as an Internet Protocol (IP) network, that is, a communication network that uses IP to send and receive messages between one or more computers that can be implemented in, for example, an Internet network, a LAN, and an enterprise network. The network can serve 5G or a digital television (DTV) distribution network operating in a single frequency network (SFN) operation. According to an embodiment of the present inventive concept, the term network refers to a power grid network, an isolated network, or any applicable network.

[0050] With respect to a certain node, station or other time-related device, the term "local clock" refers to a clock present in / at the node, station or device. With respect to a certain node, a "remote clock" refers to a clock that does not exist in / at the node but exists at another node / station far away from the node / station. A "high-quality clock" refers to a clock that has a low intrinsic timing error and can keep time without drift, such as an atomic clock. Rubidium atomic clocks are commonly used as high-quality clocks. A clock may show an incorrect time or a correct time. A clock that shows an incorrect time may also be referred to as inaccurate or incorrect, such as an inaccurate or incorrect clock. A clock that shows the correct time may also be referred to as accurate or correct, such as an accurate or correct clock.

[0051] The system of the present invention and the nodes and methods executed therein are primarily intended for robust calibration or verification of time-related devices or nodes in a radio communication network or similar network, and are applicable to any network with nodes that know the time. A 5G network has been exemplified here because 5G networks are generally dependent on exact time, both due to the requirements for timing and latency and due to the use of multiple base stations in the RAN, where multiple base stations are simultaneously connected to a terminal, device, user equipment (UE) or mobile station. A UE can be served by multiple base stations at the same time, which may be both 5G base stations and LTE base stations (such as gNB, eNB or NB) and 5G small cells or nodes for large-scale MTC (smart devices, buildings, meters) or critical MTC (traffic control, industrial control or remote surgery). 5G has different operating modes, of which one of the most demanding operating modes (5GCoPM) is a combination of CoMP and MIMO (multiple input multiple output), that is, multiple access points using several antennas, which requires clock / timing accuracy of 100ns.

[0052] The present invention will now be described with reference to various embodiments implemented in the system of the present invention.

[0053] Reference now Figure 2a to Figure 2band Figure 3a to Figure 3b , the RAN domain 30 of the prior art RAN 5 (which is in Figure 1 ) is used as an example in which an embodiment of the inventive concept described herein is implemented.

[0054] In the example shown here, DU 70 represents node N1 to be calibrated by using MCD (100-102). N1 is physically located at a cell site 20 (Telco user domain) of a telecommunications provider that controls node N1. N1 has a local clock (LC) and a radio modem 71.

[0055] The MCD 100 is a mobile device, such as a vehicle, an unmanned aerial vehicle (e.g., a drone or radio-controlled helicopter), or a carrier. The type of vehicle may be selected based on the telco site and node. When serving a base station as in the example given here, a drone is a suitable vehicle that allows the MCD to be remotely controlled to move to different base stations to provide contactless local calibration or verification of N1. Here the MCD 100 is equipped with a wireless communication interface, a radio modem 101a for providing local data transmission between the MCD and N1, a local reference clock (RC), including a GPS receiver for providing a trusted reference time from GPS10a, and a processing circuit system (not shown) that is configured to implement the following steps: Figure 2a As shown, via RU 60 through modem 101a and modem 71 of DU 70, or as shown Figure 2b As shown, a time transfer session is established between the MCD and N1 via a dedicated radio modem 72 arranged at or connected to N1. The time transfer session initiates the exchange of timing characteristics of the MCD 100 and the DU 70 (e.g., timestamps of the local time LC and the reference time RC of N1). The processing circuit system is further configured to: compare the timing data of the reference clock with the timing data received from N1, determine any timing data offset between N1 and the MCD, and optionally store the timing data of the time transfer session and / or send the timing data offset to the site or the controller of the site for calibrating N1 based on the determined timing data offset. The comparison of the timing data may include, for example, comparing the clock phase of the reference clock RC and the local clock LC on N1. The calibration or update of the LC may be handled via any available management path of the node N1.

[0056] The radio modems 101a, 71, 72 are used to send data over shorter or longer distances on their own frequencies, which may be idle frequencies or frequencies requiring license / approval.A time transfer session may be established on a dedicated channel.

[0057] In an embodiment, the wireless communication interface comprises at least one of an optical receiver, optical transmitter or optical transceiver, an audio receiver, audio transmitter or audio transceiver, a radio receiver, radio transmitter or radio transceiver, or an inductive receiver, inductive transmitter or inductive transceiver.

[0058] According to an embodiment, the wireless communication interface comprises an optical receiver / transmitter / transceiver (not shown). In this scenario, N1 is equipped with an optical transmitter, such as a light source or laser that flashes at a predetermined frequency, such as every second (e.g., pulses per second - known technology), so as to transmit timing characteristics (such as its perceived clock time) by means of an optical signal. The MCD comprises an optical receiver that receives the optical signal. The opposite is also applicable, wherein the MCD is also or alternatively arranged with a light source to provide an optical signal containing timing data / time information, for example, which timing data / time information signals a time reference of the MCD to N1. N1 (also or alternatively) comprises an optical receiver that receives the optical signal containing the time reference from the MCD and is further arranged to calibrate its clock time according to the timing data received in the optical signal. In embodiments where the MCD has an optical receiver, the MCD can further determine an offset between the local times of the MCD and N1, store and / or transmit its offset back from the MCD to N1 for adjustment by N1 via the communication channel described above (i.e., the optical signals sent and received). The MCD preferably stays within a predetermined distance, eg, within the reach of the signal, for as long as it needs to verify that the calibration was successful.

[0059] According to an embodiment, the MCD is arranged to track the geographic location, i.e., longitude / latitude (LON / LAT), of itself and / or N1. The geographic locations of N1 and MCD are tracked and compared using GNSS or other means (such as landscape awareness detection, etc.). The compared geographic locations can then be used to adjust the latency of a one-way communication signal (e.g., a one-way optical signal). Tracking and comparing the geographic locations of the MCD and N1 is advantageous because it enables the use of slower moving communication signals, such as when utilizing an audio receiver / transmitter / transceiver as a wireless communication interface between the MCD and N1.

[0060] In another embodiment, the wireless communication interface between the MCD and N1 is implemented using an inductive receiver / transmitter / transceiver (not shown). The MCD is arranged with a battery and an inductive power transfer device for transmitting power and data signals without (direct or close) mechanical or electrical contact (e.g., near-field wireless transfer). The MCD can be arranged on a vehicle (such as a drone or a land vehicle). Remote control or programming of the MCD enables it to access N1 so as to recharge its battery using near-field wireless power transfer from an inductive charging pad arranged at N1. By further equipping the MCD and N1 (e.g., the inductive charging pad of N1) with a signal generator and / or a receiver for transmitting data by means of an inductive transfer device, verification and / or calibration of N1 using the time reference of the MCD is achieved. Optionally, verification and / or calibration is performed simultaneously with recharging the battery of the MCD.

[0061] According to an embodiment, both the MCD and N1 have a 4 / 5G modem or similar. The station and drone connect and measure their relative time offset, providing information for calibrating the station.

[0062] According to Figure 3a The illustrated embodiment, rather than receiving a time reference via a GPS receiver, provides a newly updated stable clock to the embodiment of the MCD 101. The updating of the clock is preferably performed in a docking station, for example, to which the MCD is returned for recharging / refueling / updating. Further, in Figure 3a In the example shown, the site node N1 distributes its local time via local radio. Here the time transfer session is a one-way communication. The MCD 101 moves to a position at a predetermined distance of the cell site and receives the radio signal via the radio receiver 101b, compares the timing data received from N1 with the reference time RC, from which the offset of the site node compared to the reference time RC can be deducted and transmitted to the controller. The calibration or update of LC can be handled via any available management path of the node N1.

[0063] According to Figure 3b In the illustrated embodiment, both the site node N1 and the MCD 102 are equipped with a two-way radio (such as Wi-Fi). The MCD 102 can therefore measure the time offset of the site node compared to a reference time RC.

[0064] According to an embodiment, the determination of the timing offset / comparison of the timing data is performed in the central node. The MCD communicates with the central node to send the obtained respective timing data of the MC and the uncalibrated device / node.

[0065] Reference now Figure 4According to an embodiment of the inventive concept, the method used herein utilizes that both the MCD 100 and the site node N1 can reach a common time reference (CTR). Figure 1 In the described exemplary example, CTR is one of the T-GM91, but CTR can be any common clock reference reachable by the node N1 and the MCD 100. The MCD 100 establishes a time transfer session to obtain timing data including the timing data of N1, but does not do so by establishing a session directly to the node N1. Instead, a first time transfer session is established between the MCD 100 and the CTR via the RU 60, and a second time transfer session is established between the node N1 and the CTR using the same RU 60. The timing data of N1 is then determined by comparing the timing data offsets between the reference clock RC and the CTR and between the local clocks of N1 and CTR. Calibration using a common timing reference is based on our assumption that both the MCD and N1 can reach the common timing reference CTR via the same path.

[0066] Assume that the time error relative to the master device (T-GM 91) is expressed as follows:

[0067] e1——Absolute time error of N1 (1)

[0068] e m ——Absolute time error of MCD (2)

[0069] e c ——Absolute time error of CTR (3)

[0070] Now assume that MCD establishes a time transfer session to CTR with a systematic error d. Starting from the time transfer session, we have a measure of the total time error of MCD, v m , which is equal to:

[0071] v m =e m -e c +d (4)

[0072] Now, N1 also establishes a time transfer session to CTR. Assuming N1 establishes a time transfer session to CTR, there may be negligible or no difference in the transmission characteristics compared to how the MCD establishes its time transfer session. For example, if the MCD and N1 are close or even in the same location and both use a 4G connection with the same operator, they both use the same radio (e.g., Figure 4 Assuming this is the case, a time transfer session between N1 and CTR with the same systematic error d gives a measure v1 of N1’s total time error:

[0073] v1=e1-e c +d (5)

[0074] Given v m and v1, the absolute time error e1 can now be calculated using equations (4) and (5), which give:

[0075] v1-v m =(e1-e c +d) - (e m -e c +d) = e1 - e m (6)

[0076] Due to the time error of MCD, m is assumed to be zero or negligible (due to a trusted reference clock),

[0077] v1-v m ~= e1 (7)

[0078] Therefore, by using a common time reference, the time error (ie, timing data offset) of N1 can be found using the time transfer session to the common timing reference, and the absolute time error of N1 is eliminated. Furthermore, as long as the time transfer sessions share the same systematic error, the systematic error is also eliminated.

[0079] Now refer to Figure 5 The embodiments of the method proposed according to the present invention are described in more detail. It should be understood that Figure 5 Some operations and modules illustrated with solid line borders and some operations and modules illustrated with dotted line borders are included. The operations and modules illustrated with solid line borders are operations included in the most extensive example embodiments. The operations and modules illustrated with dotted line borders are example embodiments, which may be included in or part of the operations and modules of the more extensive example embodiments, or are further embodiments that may be adopted in addition to the operations and modules of the more extensive example embodiments. It should be understood that the operations do not need to be performed in order, and the method covers different embodiments. In addition, it should be understood that not all operations need to be performed.

[0080] Figure 5 A method for calibrating a time-related device or node N1 with respect to a timing characteristic using a mobile calibration device MCD is illustrated, the method comprising: providing a reference clock for the MCD (S100), establishing a time transfer session (S101), for example between the MCD and N1 (S101A). The reference clock can be implemented in different ways, for example, by using a local clock that has been recently calibrated and is trusted (S100A) or a time received via a GNSS receiver (S100B).

[0081] The time transfer method can be performed in one direction, for example, timing data is sent from the MCD to N1, or from N1 to the MCD, or it can be bidirectional so that timing data is exchanged in both directions. The method further includes comparing the timing data of the reference clock with the timing data from N1 (S102). Depending on the flow of timing data, for example, whether a one-way time transfer session or a two-way time transfer session is initiated and in what direction, this step of analyzing the timing data and comparing it can be performed at different locations of a calibration system formed by the MCD (S102A), the device or node to be calibrated (S102B) and optionally another node (S102C) in the network to which the node is connected (e.g. a centralized node). In the same way, the step of determining the timing data offset (S103) between N1 and the MCD, thereby providing an offset value to be used when calibrating N1, can be performed in the following:

[0082] a) In the MCD (S103A) for subsequent (optional) storage locally or remotely (S106). The offset value may then be transmitted to a central node or directly to N1 to perform calibration of the timing characteristics of N1 based on the timing data offset (S104A).

[0083] b) in the node to be calibrated (S103B), and then (optionally) stored locally or remotely (S106) at a later time. The offset value is used when calibrating N1 (S104B), or

[0084] c) In a centralized node (S103C) for subsequent (optional) storage locally or remotely (S106). The offset value is used when instructing N1 to perform a corresponding calibration (S104C).

[0085] Before establishing the time transfer session, the method may further include the following steps: moving the MCD within a predetermined distance D from N1 (S105B), and optionally determining the distance to N1 (S105A), for example, receiving the distance from a lookup table, setting the predetermined distance according to the hardware used in the wireless communication link / interface or a contactless type measuring device used to establish the time transfer session between the MCD and N1, and adaptively determining the distance, for example, by measuring the signal strength of the time transfer session or a test signal, etc.

[0086] As previously referenced Figure 4As shown, a common time reference CTR is determined for N1 and MCD, and a corresponding time transfer session is established between i) the MCD and CTR (S101B) and ii) N1 and CTR (S101C). When a corresponding time transfer session is established between i) the MCD and the common time reference CTR and ii) N1 and CTR, the timing data of N1 can be determined by comparing the timing data offset between the reference clock and CTR and between N1 and CTR (S102D), see the equation here.

[0087] The calibration is generally described with reference to step S104. N1 is calibrated using a trusted source (i.e., the reference time of the MCD that provides trusted time information to N1). The calibration can be performed directly if the temporary time transfer session involves two-way communication so that the calibration offset can be transmitted directly to N1, or if the MCD transmits the reference time to N1 and the analysis of the offset is performed in N1. The calibration offset can also be transmitted from the MCD via a link to a node controller in a management network to which both node N1 and the MCD are connected, or the calibration offset is transmitted in some other manner, for example, by sending the calibration offset to a user to manually update a stand-alone node that is not connected to a network.

[0088] Figure 6 A block diagram of a mobile node / calibration device 220 of the present invention is illustrated. The mobile node 220 includes a wireless communication interface 221 (e.g., a radio communication interface, a radio circuit system, a network interface, or a wireless / contactless measurement device) that is configured to receive and send data communications and / or control signals to and from a device to be calibrated (optionally within a network), for example, for connecting the mobile node to at least one adjacent node, such as a master node or a slave node, via a transmission link, and / or for sending and receiving data, such as timing data, via a transmission link, or configured to measure, for example, an optical signal. It should be understood that, according to some aspects, the communication interface 221 is included as any number of transceiver, receiving and / or transmitting units or circuit systems. It should be further understood that the communication interface 221 can be in the form of, for example, any input / output communication port known in the art. It can include an RF circuit system and a baseband processing circuit system (not shown).

[0089] The mobile node 220 further includes a processing circuit system 222, which includes a processor 224 and is configured to perform the method of the present invention. According to some aspects, the mobile node 220 further includes at least one memory unit or circuit system 223 in communication with the communication interface 221. The memory 223 can be configured to store received or sent data and / or executable program instructions, for example. The memory 223 can be, for example, a computer-readable memory of any suitable type, and can be, for example, a volatile and / or non-volatile type. The memory can, for example, record a received timestamp or an actual and / or preferred distance to a node to be calibrated. The processing circuit system 222 is configured to cause the network node 220 to perform the method of the present invention.

[0090] The processing circuit system 222 is, for example, a computing unit of any suitable type, such as a microprocessor, a digital signal processor DSP, a field programmable gate array FPGA or an application-specific integrated circuit ASIC or any other form of circuit system. It should be understood that the processing circuit system does not need to be set as a single unit, but is set as any number of units or circuit systems according to some aspects. Therefore, the processing circuit system may include a memory 223 for storing a computer program, and a processor 224 configured to execute a method of the computer program. The computer program is, for example, stored in a memory MEM 23. The memory 223 may be any combination of a random access memory RAM and a read-only memory ROM. In some cases, the memory 223 also includes a permanent storage device, for example, the permanent storage device may be any single or combination of a magnetic memory, an optical memory or a solid-state memory or even a remotely mounted memory.

[0091] According to some aspects, a controller (CTL) (not shown) or processing circuitry 222 is capable of executing computer program code. It should be understood that the processing circuitry need not be arranged as a single unit, but rather as any number of units or circuitry according to some aspects.

[0092] The mobile node 220 may include an internal clock 225 and may be capable of providing and storing timestamps associated with the internal clock and storing timestamps associated with other nodes. The mobile node 220 may include or be connected to a GNSS receiver ( Figure 6 not shown).

[0093] According to some aspects, the disclosure relates to a computer program comprising computer program code, which when executed causes a mobile node or a device or a network node to perform the method described above and below. In other aspects, the disclosure relates to a carrier embodying the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer-readable storage medium.

[0094] In the drawings and specification, disclosed exemplary aspects of the present disclosure have been disclosed. However, many changes and modifications may be made to these aspects without departing substantially from the principles of the present disclosure. Therefore, the present disclosure should be regarded as illustrative rather than restrictive, and is not limited to the specific aspects discussed above. Therefore, although specific terms are employed, these terms are used only in a general and descriptive sense and not for the purpose of limitation.

[0095] The description of the example embodiments provided herein has been presented for the purpose of illustration. The description is not intended to be exhaustive or to limit the example embodiments to the precise form disclosed, and modifications and variations are possible or can be obtained from the practice of various alternatives to the provided embodiments in accordance with the above teachings. The examples discussed herein are selected and described to explain the principles and properties of the various example embodiments and their practical applications, so that those skilled in the art can utilize the example embodiments in various ways and with various modifications suitable for the intended specific use. The features of the embodiments described herein can be combined in all possible combinations of methods, nodes, networks, and systems. It should be understood that the example embodiments presented herein can be practiced in any combination with each other.

[0096] It should be noted that any reference signs do not limit the scope of the claims and that several "means", "units" or "nodes" may be represented by the same item of hardware.

[0097] Although the present invention has been described with respect to embodiments disclosing certain nodes and networks, it will be apparent to those skilled in the art that the calibration of the present invention may be applied to any network based on the present disclosure. Those skilled in the art recognize that the present invention is by no means limited to the above-described embodiments. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, embodiments of the present invention may be based on other network technologies other than 5G RAN.

Claims

1. A method for contactless local calibration of a time-related device N1 using a mobile calibration device MCD having a local reference clock RC, the method comprising: Moving the MCD within a predetermined distance from N1 (S105B); Establishing at least one temporary time transfer session for sending and / or receiving signals containing timing data associated with at least one local clock in N1 and RC (S101A, S101B, S101C); Determine the timing data offset between the local clocks of N1 and RC (S103); and The timing characteristics of N1 are calibrated or verified based on the determined timing data offset (S104).

2. The method according to claim 1, wherein: The temporary time transfer session is a one-way time transfer.

3. The method according to claim 1 or 2, wherein: The temporary time transfer session is performed using a local wireless communication link or a contactless type measuring device.

4. The method according to any preceding claim, further comprising determining the predetermined distance (S105A).

5. A method according to any preceding claim, wherein: The predetermined distance is preconfigured, received via the central node, and selected to be one that provides a known or negligible transmission time asymmetry in both directions of data transmission between N1 and the MCD.

6. The method according to claim 4, wherein: The predetermined distance determined is determined based on one of the wireless communication link or measuring device used, determined by measuring the signal strength in a temporary time transfer session or a test signal used when approaching N1, obtained using previous experience, and determined via a lookup table.

7. A method according to any preceding claim, wherein: The at least one temporary time transfer session (S101A) is established in any direction between the MCD and N1, or the at least one temporary time transfer session is established by establishing corresponding temporary time transfer sessions between i) the MCD and a common time reference CTR (S101B) and ii) N1 and the CTR (S101C).

8. The method of claim 7, when establishing a temporary time transfer session between the MCD and the CTR, wherein: The step of determining the timing data offset between the local clocks of N1 and RC is performed by comparing the timing data offset between RC and the CTR and between N1 and CTR.

9. The method according to any one of claims 1 and 3 to 8, wherein The temporary time transfer session is a two-way time transfer session.

10. A method according to any preceding claim, wherein: N1 is at least one of a node in a network, a mobile base station, a time transfer device, a TV / radio transmitter, a power station in a smart grid, data communication equipment, data terminal equipment, time-related equipment, TV media production equipment and / or network, radio media production equipment and / or network, military equipment, a sensor station, a radar station, a stand-alone device not connected to a communication network or other network, and a group of independent time-related equipment combined into an isolated network.

11. A mobile calibration system (220) for providing contactless calibration of a time-dependent device N1, the system comprising: A mobile calibration device MCD, the mobile calibration device comprising: a wireless communication interface (221) or a contactless measurement device configured to send and / or receive a signal containing timing data for local data transmission between the MCD and N1, and a reference clock (225); and A control unit comprising a processing circuit system (222) including a memory (223) and a processor (224) configured to perform the steps of the method according to any one of claims 1 to 11.

12. The MCD of claim 11, wherein: The MCD further includes a Global Navigation Satellite System (GNSS) receiver for providing the reference clock.

13. The MCD according to any one of claims 11 to 12, wherein: The wireless communication interface or the contactless measuring device comprises at least one of an optical, audio, radio or inductive receiver, an optical, audio, radio or inductive transmitter, an optical, audio, radio or inductive transceiver.

14. The MCD according to any one of claims 11 to 13, wherein: The MCD is a ground vehicle, a watercraft, an air vehicle, or a transportable device.

15. An MCD according to any one of claims 11 to 14, further arranged to track its own and / or N1's geographical location, ie longitude / latitude (LON / LAT).

16. A computer program comprising computer program code which, when executed in a network node or a network device, causes the network node or the network device to perform the method according to any one of claims 1 to 10.

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