Clock synchronization method for communication network and communication node

Abstract

To provide a method for designing a communication network in a form suitable for an installation space.SOLUTION: A method is performed by a first communication node which is not an uppermost communication node, for clock synchronization performed between communication nodes included in a communication network, the method including the steps of: receiving a synchronization source signal; generating a reference clock for clock synchronization from the received synchronization source signal; and transmitting, to at least one second communication node, the generated reference clock through a second path including at least a portion reverse to a first path through which a downlink signal is transmitted to the first communication node in the communication network, and not passing through a base station connected to the communication network.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a clock synchronization method for a communication network and a communication network using the same, and more particularly to a clock synchronization method for a communication network capable of transmitting a reference clock through a first path including at least a portion of a path that reverses a second path through which a downlink signal is transmitted, and a communication network using the same. [Background technology]

[0002] Currently available distributed antenna systems (DAS) have a configuration in which a headend device receives external reference clock information and transmits the reference clock to other nodes (e.g., extension devices or remote devices).

[0003] However, because the headend device is quite large in size and weight and requires a separate power supply, it is generally placed in a separate space within the building where the distributed antenna system is installed. In such a structure, in order to receive external reference clock information, a clock source located far away from the headend device must be connected by a cable, which is structurally inefficient. Summary of the Invention [Problem to be solved by the invention]

[0004] The technical problem to be solved by the present invention is to provide a clock synchronization method for a communication network capable of transmitting a reference clock through a first path including at least a part of a path that reverses a second path along which a downlink signal is transmitted, and a communication network using the same. [Means for solving the problem]

[0005] A method for clock synchronization among communication nodes included in a communication network according to an embodiment of the present invention, performed by a first communication node that is not a top-level communication node, includes the steps of: From the synchronization source receiving a synchronization source signal; generating a reference clock for clock synchronization based on the received synchronization source signal; and From the base station a first communication node connected to the communication network, the first communication node including at least a part of a route that reverses the first route transmitted to the first communication node; The aforementioned The generated reference clock is transmitted at a reduced rate via a second route that does not pass through a base station. and and transmitting the same to another second communication node.

[0006] In some embodiments, the top communications node is a communications node included in the communications network that first receives the downlink signal from the base station.

[0007] In some embodiments, the communication network includes at least one of a headend device, an extension device, and a remote device, and the first communication node and the second communication node are the remote devices.

[0008] In some embodiments, the communications network includes at least one of a headend device, an extension device, and a remote device, and the first communications node is the extension device.

[0009] In some embodiments, the reference clock is at least one clock that is adjacent to the first communication node in the communication network. and from another third communication node to at least one node that is not adjacent to the first communication node. and The signal is also transmitted in the direction of a fourth communication node.

[0010] In some embodiments, the step of transmitting the reference clock comprises: ,before Records andand either one of the at least one third communication node is determined as a synchronization master, and and Another fourth communication node is determined as a synchronization slave, and the reference clock is transmitted from the communication node determined as the synchronization master to the communication node determined as the synchronization slave.

[0011] In some embodiments, the synchronization master and the synchronization slave are dynamically determined based on a Synchronization Status Message (SSM) protocol.

[0012] In some embodiments, the method further includes a step of selecting one communication node to be used for clock synchronization from two or more communication nodes each connected to two or more synchronization sources that provide the synchronization source signal, and in the step of receiving the synchronization source signal, the synchronization source signal is received through the selected one communication node.

[0013] In some embodiments, in the step of selecting one communication node, a communication node in which a failure has occurred is excluded from among the two or more communication nodes and the one communication node is selected.

[0014] In some embodiments, the step of selecting the one communication node comprises selecting the one communication node based on the status of each of the two or more communication nodes and the capabilities of two or more synchronization sources that provide synchronization source signals to each of the two or more communication nodes.

[0015] In some embodiments, the synchronization source signal is a Global Positioning System (GPS) signal.

[0016] In some embodiments, at least a portion of the communications network is located within a building.

[0017] In some embodiments, the first communication node that receives the synchronization source signal is a communication node that is located at the highest altitude among a plurality of communication nodes included in the communication network.

[0018] A communication node according to an embodiment of the present invention performs clock synchronization in a communication network, and in a first communication node that is not a top-level communication node, From the synchronization source receiving a synchronization source signal and generating a reference clock based on the received synchronization source signal; From the base station a first communication node connected to the communication network, the first communication node including at least a part of a route that reverses the first route transmitted to the first communication node; The aforementioned The generated reference clock is transmitted to at least one second communication node via a second route that does not pass through a base station.

[0019] In some embodiments, the at least one second communication node is a higher-level node of the first communication node based on a transmission direction of the downlink signal. [Effects of the Invention]

[0020] The method and apparatus according to the embodiments of the present invention transmit a reference clock through a first path that includes at least a portion of a path that reverses to a second path along which a downlink signal is transmitted, thereby enabling a synchronization source that provides a synchronization signal to be connected in various forms to various locations within a communication network, thereby enabling the communication network to be designed in a form that is suitable for the installation space. [Brief explanation of the drawings]

[0021] To provide a more complete understanding of the drawings referred to in the detailed description of the present invention, a brief description of each of the drawings is provided. [Figure 1] 1 is a conceptual diagram of a communication system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram of one embodiment of the distributed antenna system shown in FIG. 1. [Figure 3]2 is a block diagram of another embodiment of the distributed antenna system shown in FIG. 1. [Figure 4] 2 is a flowchart of a method for clock synchronization in a communication network according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0022] The technical concept of the present invention can be variously modified and can have various embodiments, and therefore, specific embodiments are illustrated in the drawings and will be described in detail. However, this is not intended to limit the technical concept of the present invention to the specific embodiments, and it should be understood that the technical concept of the present invention includes all modifications, equivalents, and alternatives that fall within the scope of the technical concept of the present invention.

[0023] In explaining the technical idea of the present invention, if a detailed description of the related prior art is deemed to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Furthermore, numbers (e.g., 1, 2, etc.) used in the description of this specification are merely identification symbols for distinguishing one component from another.

[0024] Furthermore, in this specification, when a component is referred to as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled to or connected to the other component, but unless otherwise specified, it may also be coupled to or connected via another component in between.

[0025] Furthermore, the terms "unit," "device," "child," "module," etc. used in this specification refer to a unit that processes at least one function or operation, which may be embodied in hardware or software, or a combination of hardware and software, such as a processor, microprocessor, microcontroller, CPU (Central Processing Unit), GPU (Graphics Processing Unit), APU (Accelerate Processor Unit), DSP (Drive Signal Processor), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), etc., and may be embodied in a form combined with a memory that stores data necessary for processing at least one function or operation.

[0026] It should be understood that the division of components in this specification merely represents a division according to the main function of each component. That is, two or more components described below may be combined into one component, or one component may be divided into two or more components according to further subdivided functions. It goes without saying that each component described below may perform some or all of the functions of other components in addition to its own main function, and that some of the main functions of each component may be exclusively performed by other components.

[0027] FIG. 1 is a conceptual diagram of a communication system according to an embodiment of the present invention.

[0028] Referring to FIG. 1, the communication system 10 includes a core network 50, a base transceiver station (BTS) 100, a distributed antenna system (DAS) 200 that relays communication signals of the base station 100, and an NMS (Network Management Server or Network Management System) 300 that manages and monitors the distributed antenna system 200.

[0029] According to an embodiment, the communication system 10 is divided into a core network 50, and base stations 100 and a distributed antenna system 200 that constitute an access network that connects user terminals to the core network 50.

[0030] The distributed antenna system 200 is described as an example of a communication network and can directly perform at least some of the functions of the base station 100 .

[0031] Distributed antenna system 200 includes head-end device 210 communicatively coupled to base station 100 and constituting a head-end node, a plurality of remote devices 220a, 220b, 220c, and 220d constituting remote nodes and coupled to other remote nodes or located at respective remote service locations and communicatively coupled to user terminals, and extension devices 230a and 230b constituting extended nodes.

[0032] In some embodiments, the distributed antenna system 200 is embodied as an analog distributed antenna system.

[0033] In other embodiments, the distributed antenna system 200 may be implemented as a digital distributed antenna system, or in some cases as a mixed type (e.g., some nodes perform analog processing and the remaining nodes perform digital processing).

[0034] Meanwhile, FIG. 1 shows an example of the topology of the distributed antenna system 200, and the distributed antenna system 200 can be modified in various ways in consideration of the particularities of the installation area and application field (e.g., in-building, subway, hospital, stadium, etc.).

[0035] According to an embodiment, the distributed antenna system 200 may be configured to include a duplex structure, which will be described later with reference to FIG.

[0036] In the distributed antenna system 200, the extension devices 230a and 230b are utilized when the number of branches in the head-end device 210 is limited compared to the number of remote devices that need to be installed.

[0037] To further explain each node in the distributed antenna system 200 and its function, the head end device 210 serves as an interface with the base station.

[0038] Depending on the embodiment, the headend device 210 may be coupled to multiple base stations.

[0039] Depending on the embodiment, the headend device 210 may be implemented as a main headend device and a sub-headend device, and may be connected to a base station for each service frequency band or each sector of a particular operator, and in some cases, the main headend device may supplement its coverage with a sub-headend device.

[0040] Generally, RF (Radio Frequency) signals transmitted from base stations are high-power signals, so the head-end device 210 attenuates these high-power RF signals to signals of a power suitable for processing at each node. The head-end device 210 reduces the high-power RF signals for each frequency band or each sector to low power. The head-end device 210 combines the low-power RF signals and distributes the combined signals to the extender device 230a or the remote device 220a.

[0041] Depending on the embodiment, the headend device 210 may receive communication signals in a digital format (e.g., Common Public Radio Interface (CPRI), Open Radio Interface (ORI), Open Baseband Remote Radiohead Interface (OBSAI), or e-CPRI) directly from the base station 100.

[0042] Each of the remote units 220a, 220b, 220c, and 220d separates the transferred and combined signals into frequency bands and performs signal processing such as amplification, etc. Then, each of the remote units 220a, 220b, 220c, and 220d transmits base station signals to user terminals within its service coverage area through a service antenna (not shown).

[0043] The remote device 220a and the remote device 220b are connected via an RF cable or wireless communication, and multiple remote devices are connected in a cascade structure as needed.

[0044] The extender device 230a transmits the transmitted and combined signal to the remote device 220c that is coupled to the extender device 230a.

[0045] The extension device 230b is connected to one end of the remote device 220a and receives signals transmitted from the headend device 210 via the remote device 220a via downlink communication. At this time, the extension device 230b transmits the received signals again to the remote device 220d connected to the rear end of the extension device 230b.

[0046] Meanwhile, the base station 100 and the headend device 210 are connected to each other via RF cables, optical cables, or Ethernet cables (e.g., twisted cables, UTP cables), and at the lower end of the headend device 210, except between the remote devices 220a and 220b, they are connected to each other via optical cables or Ethernet cables (e.g., twisted cables, UTP cables), and the signal transmission media and communication methods between each node can be variously modified. According to an embodiment, when the internal components of the distributed antenna system 200 are connected to each other by optical cables, the head-end device 210, the remote devices 220a, 220b, 220c, and 220d, and the extension devices 230a and 230b may be equipped with optical transceiver modules for transmitting and receiving optical type signals through electrical-to-optical / optical-to-electrical conversion, and may include WDM (Wavelength Division Multiplexing) elements when the nodes are connected by a single optical cable.

[0047] The distributed antenna system 200 is connected to an external management device (not shown), such as an NMS (Network Management Server or Network Management System) 300 or an NOC (Network Operation Center) (not shown), via a network, allowing an administrator to remotely monitor the status and problems of each node in the distributed antenna system and remotely control the operation of each node.

[0048] FIG. 2 is a block diagram of one embodiment of the distributed antenna system shown in FIG.

[0049] 1 and 2, distributed antenna system 200A includes headend unit 210, remote units 220-1 through 220-4, extension units 230-1 and 230-2, smolcell 400, and synchronization source 500.

[0050] A communication network, for example, a distributed antenna system 200A, receives a synchronization source signal through any one of the communication nodes (e.g., 220-1) among the remaining communication nodes (e.g., 220-1 to 220-4 and 230-1 to 230-2) excluding the top communication node (e.g., 210) among the plurality of communication nodes 210, 220-1 to 220-4, 230-1 to 230-2 included in the distributed antenna system 200A.

[0051] Depending on the embodiment, the top communication node (e.g., 210) may refer to the communication node among the communication nodes 210, 220-1 to 220-4, 230-1 to 230-2, 400 included in the communication network, e.g., the distributed antenna system 200A, that first receives the downlink signal from the base station 100.

[0052] Depending on the embodiment, the communication node receiving the synchronization source signal may be remote device 220-1 through 220-4 or extension device 230-1 or 230-2.

[0053] When the first remote device 220-1 receives the synchronization source signal, the first remote device 220-1 is coupled to the synchronization source 500.

[0054] The synchronization source 500 receives or generates a synchronization source signal. In some embodiments, the synchronization source 500 may include a GPS (Global Positioning System) antenna. In this case, the synchronization source 500 receives a GPS signal from outside the distributed antenna system 200A and uses the received GPS signal as the synchronization source signal.

[0055] The first remote device 220-1 extracts or generates a reference clock for clock synchronization from the synchronization source signal received from the synchronization source 500.

[0056] The first remote device 220-1 transmits the extracted or generated reference clock to other communication nodes (e.g., 210, 220-2 to 220-4, and 230-1 to 230-2) via a second path PATH2 that includes at least a portion of a path that reverses the first path PATH1 along which the downlink signal is transmitted in the distributed antenna system 200A.

[0057] The first path PATH1 is a path through which downlink signals are transmitted in the distributed antenna system 200A. Downlink signals transmitted from the base station 100 are transmitted to the extension devices 230-1 and 230-2 via the headend device 210, and the extension devices 230-1 and 230-2 transmit the downlink signals to the remote devices 220-1 through 220-4 connected to the extension devices 230-1 and 230-2, respectively. The remote device (e.g., 220-2) connected to the small cell 400 among the remote devices 220-1 through 220-4 transmits the received downlink signal to the small cell 400 via the first path PATH1.

[0058] The second path PATH2 is a path along which a reference clock is transmitted in the distributed antenna system 200A, and the reference clock extracted or generated by the first remote device 220-1 is transmitted along the second path PATH2.

[0059] The second path PATH2 includes at least a portion of the first path PATH1 that is a reverse path. For example, the path from the first remote device 220-1 to the first extension device 230-1 and the path from the first extension device 230-1 to the headend device 210 in the second path PATH2 are reverse paths of the first path PATH1.

[0060] The second path PATH2 is formed in a direction from a communication node adjacent to the remote device (e.g., 220-1) that receives the synchronization source signal to a communication node far from the remote device (e.g., 220-1). The reference clock is transmitted from the remote device (e.g., 220-1) that receives the synchronization source signal on the second path PATH2 from a communication node adjacent to the remote device (e.g., 220-1) to a communication node far from the remote device (e.g., 220-1).

[0061] For example, the reference clock is transmitted from the first remote device 220-1 to the adjacent first extension device 230-1 on the second path PATH2 to the headend device 210 far from the first remote device 220-1, and from the adjacent first extension device 230-1 on the second path PATH2 to the second remote device 220-2 far from the first remote device 220-1 on the second path PATH2.

[0062] In some embodiments, a communication node (e.g., 230-1) that is relatively close on the second path PATH2 is determined as a synchronization master, and a communication node (e.g., 210 or 220-2) that is relatively far on the second path PATH2 is determined as a synchronization slave. At this time, a reference clock is transmitted from the communication node (e.g., 230-1) determined as the synchronization master to the communication node (e.g., 210 or 220-2) determined as the synchronization slave.

[0063] According to an embodiment, the synchronization master and the synchronization slave may be dynamically determined based on a Synchronization Status Message (SSM) protocol.

[0064] FIG. 3 is a block diagram of another embodiment of the distributed antenna system shown in FIG.

[0065] 1 and 3, distributed antenna system 200B includes headend device 210, remote devices 220-1a through 220-5a and 220-1b through 220-5b, extension devices 230-1a through 230-5a, smolcells 400-1a through 400-5a and 400-1b through 400-5b, and synchronization sources 500-1 and 500-2.

[0066] Distributed antenna system 200B includes two or more communication nodes (eg, 220-5a and 2200-5b) each coupled to synchronization sources 500-1 and 500-2 that provide a synchronization source signal.

[0067] According to an embodiment, the headend device 210 or the NMS 300 may select one communication node (e.g., 220-5a and 220-5b) to be used for clock synchronization from among the communication nodes connected to the plurality of synchronization sources 500-1 and 500-2.

[0068] According to an embodiment, when selecting one communication node to be used for clock synchronization, one communication node to be used for clock synchronization may be selected from among the communication nodes (e.g., 220-5a and 220-5b) connected to the plurality of synchronization sources 500-1 and 500-2, excluding a communication node in which a failure has occurred. In this case, the headend device 210 or the NMS 300 may monitor whether a failure has occurred in the communication nodes (e.g., 220-1a to 220-5a, 220-1b to 220-5b, 230-1a to 230-5a).

[0069] Depending on the embodiment, when selecting one communication node to use for clock synchronization, one communication node to use for clock synchronization may be selected based on the status (e.g., faults, traffic, etc.) of each communication node (e.g., 220-5a and 220-5b) connected to the multiple synchronization sources 500-1 and 500-2, and the performance (grade of the synchronization source, stability and accuracy of the synchronization source signal, etc.) of each of the multiple synchronization sources 500-1 and 500-2.

[0070] In some embodiments, at least a portion of the distributed antenna system 200B may be installed inside a building. In this case, each component of the distributed antenna system 200B may be arranged on a different floor of the building, and communication between different floors is performed through the extension devices 230-1a to 230-5a and the head-end device 210.

[0071] According to an embodiment, the communication nodes (e.g., 220-5a and 220-5b) that receive the synchronization source signal may be the communication nodes located at the highest altitude (or floor) among the communication nodes included in the distributed antenna system 200B. In this case, the communication nodes (e.g., 220-5a and 220-5b) that receive the synchronization source signal may be located adjacent to the rooftop of a building, which is advantageous for receiving the synchronization source signal, and may acquire the synchronization source signal within a short distance.

[0072] FIG. 4 is a flowchart of a method for clock synchronization in a communication network according to an embodiment of the present invention.

[0073] Referring to Figures 1 to 4, a synchronization source signal is received through any one of the remaining communication nodes (e.g., 220-1, 220-5a, or 220-5b) among the communication nodes included in a communication network (e.g., 200, 200A, 200B) excluding the top communication node (e.g., 210) (step S410).

[0074] In some embodiments, the synchronization source signal may be a GPS signal.

[0075] A communication node (for example, 220-1, 220-5a, or 220-5b) that receives the synchronization source signal generates a reference clock for clock synchronization from the received synchronization source signal (step S420).

[0076] The communication node (e.g., 220-1, 220-5a, or 220-5b) that receives the synchronization source signal transmits the reference clock generated in step S420 to another adjacent communication node (e.g., 230-1 or 230-5a) via a second path (e.g., PATH2) that includes at least a portion of a path that runs in the opposite direction to the first path (e.g., PATH1) along which the downlink signal is transmitted (step S430).

[0077] Although the present invention has been described in detail above with reference to preferred embodiments, the present invention is not limited to the above embodiments and various modifications and alterations may be made by those skilled in the art within the technical spirit and scope of the present invention.

Claims

1. 1. A method for clock synchronization between communication nodes included in a communication network, performed by a first communication node that is not a top-level communication node, comprising: receiving a synchronization source signal from a synchronization source; generating a reference clock for clock synchronization based on the received synchronization source signal; and transmitting the generated reference clock to at least one second communication node via a second path that includes at least a portion of a path that reverses a first path along which a downlink signal is transmitted from a base station to the first communication node in the communication network, and that does not pass through the base station to which the communication network is connected.

2. The method according to claim 1 , wherein the highest communication node is a communication node that first receives the downlink signal from the base station among the communication nodes included in the communication network.

3. the communication network includes at least one of a headend device, an extension device, and a remote device; The method of claim 1 , wherein the first communication node and the second communication node are the remote devices.

4. the communication network includes at least one of a headend device, an extension device, and a remote device; The method of claim 1 , wherein the first communication node is the extender device.

5. 2. The method of claim 1, wherein the reference clock is transmitted in a direction from at least one third communication node adjacent to the first communication node in the communication network to at least one fourth communication node not adjacent to the first communication node.

6. In the step of transmitting the reference clock, Any one of the at least one third communication node is defined as a synchronization master, and the at least one fourth communication node is defined as a synchronization slave; 6. The method according to claim 5, wherein the reference clock is transmitted from the communication node defined as the synchronization master to the communication node defined as the synchronization slave.

7. 7. The method according to claim 6, wherein the synchronization master and the synchronization slave are dynamically determined based on an SSM protocol.

8. The method further includes selecting one communication node to be used for clock synchronization from two or more communication nodes respectively connected to two or more synchronization sources that provide the synchronization source signal; 2. The method of claim 1, wherein the step of receiving the synchronization source signal includes receiving the synchronization source signal through the selected one of the communication nodes.

9. 9. The method according to claim 8, wherein the step of selecting one communication node includes selecting the one communication node from among the two or more communication nodes, excluding a communication node in which a failure has occurred.

10. 9. The method of claim 8, wherein the step of selecting one communication node comprises selecting the one communication node depending on the status of each of the two or more communication nodes and the performance of two or more synchronization sources that provide synchronization source signals to each of the two or more communication nodes.

11. The method of claim 1 , wherein the synchronization source signal is a GPS signal.

12. The method of claim 1 , wherein at least a portion of the communication network is provided within a building.

13. 13. The method of claim 12, wherein the first communication node that receives the synchronization source signal is the communication node located at the highest altitude among a plurality of communication nodes included in the communication network.

14. In a first communication node that performs clock synchronization in a communication network and is not a top-level communication node, A first communication node that receives a synchronization source signal from a synchronization source, generates a reference clock based on the received synchronization source signal, and transmits the generated reference clock to at least one second communication node via a second path that includes at least a partial path that reverses a first path in the communication network along which a downlink signal is transmitted from a base station to the first communication node, and that does not pass through the base station to which the communication network is connected.

15. The first communication node according to claim 14, wherein the at least one second communication node is a higher-level node of the first communication node based on a transmission direction of the downlink signal.

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