KR102505297B1 - Method and apparatus for timing control in wireless communication system - Google Patents

Abstract

A timing control method and apparatus in a wireless communication system are disclosed. In a base station supporting function division according to an embodiment of the present invention, a timing control method performed by a first distributed unit (DU) including a processor and a modem (MOdulator and DEModulator, MODEM) includes the base station Acquiring first time information from a central unit (CU) included in , obtaining synchronization information with a first system based on the first time information, based on the synchronization information SFN (system frame number) is changed, if the SFN is changed, a first timing control signal including a signal indicating the changed SFN and a first tick signal having the same cycle as the SFN change cycle It may include generating, and providing the first timing control signal to the modem.

Description

Timing control method and apparatus in wireless communication system

The present invention relates to a timing control method and apparatus in a wireless communication system, and more particularly, to a timing control method and apparatus in a wireless communication system dynamically supporting function division.

Along with the development of information and communication technology, various wireless communication technologies are being developed. Representative wireless communication technologies include long term evolution (LTE) and new radio (NR), which are defined in the 3rd generation partnership project (3GPP) standard. LTE may be one wireless communication technology among 4th generation (4G) wireless communication technologies, and NR may be one wireless communication technology among 5th generation (5G) wireless communication technologies.

For the processing of rapidly increasing wireless data after the commercialization of 4G communication systems (eg, communication systems supporting LTE), the frequency band (eg, frequency bands below 6 GHz) of the 4G communication system as well as the 4G communication system A 5G communication system (eg, a communication system supporting NR) capable of using a frequency band higher than the frequency band of (eg, a frequency band of 6 GHz or higher) is being considered.

In order to build a communication system with improved efficiency compared to the 4G LTE communication system, various technologies related to 'function split' are being researched. Function division may refer to a technique for dividing and operating the function of a base station into a plurality of units. For example, the function division scheme may be implemented through a central unit (CU) and a distributed unit (DU) structure in the 3GPP standard. Alternatively, the function division method may be implemented through an O-RAN distributed unit (O-DU) and O-RAN radio unit (O-RU) structure in the O-RAN Alliance (open radio access network alliance) standard. CU and DU structures in the 3GPP standard may correspond to O-DU and O-RU structures in the O-RAN Alliance standard.

Here, in order for units to perform normal functions in a functional division-applied wireless communication system, a technique for performing accurate timing control not only for units directly having timing information but also for other units may be required.

An object of the present invention to solve the above needs is to provide a method and apparatus for performing timing control for units that divide and perform functions of a base station with high accuracy in a wireless communication system to which function division is applied. .

In a base station supporting function division according to an embodiment of the present invention for achieving the above object, a first distributed unit (DU) including a processor and a modem (MOdulator and DEModulator, MODEM) Performed by The timing control method includes obtaining, by the processor, first time information from a central unit (CU) included in the base station; Obtaining synchronization information of, checking, by the processor, when a system frame number (SFN) is changed based on the synchronization information, indicating, by the processor, the changed SFN when the SFN is changed generating a first timing control signal comprising a signal and a first tick signal having a period equal to the change period of the SFN, and providing, by the processor, the first timing control signal to the modem It may be characterized by including steps.

The timing control method may include determining, by the processor, a subframe number of at least one or more subframes based on a time point at which the SFN is changed, by the processor, each of the subframe numbers Determining a change time point, comprising, by the processor, a signal indicating the changed subframe number at each change time point of the subframe number and a second tick signal having the same period as the change period of the subframe number Generating a second timing control signal, and providing, by the processor, the second timing control signal to the modem.

The timing control method may include determining, by the processor, a slot number of at least one or more slots constituting the at least one or more subframes, by the processor, based on a change time point of each subframe number. and determining, by the processor, a signal indicating the changed slot number at each change time of the slot number and a third tick signal indicating a change of the slot number Generating a third timing control signal, and providing, by the processor, the third timing control signal to the modem.

The timing control method may include determining, by the processor, symbol numbers of at least one or more symbols constituting the at least one or more slots; Determining a change time of each symbol number, by the processor, a fourth timing control signal including the changed symbol number and a fourth tick signal instructing change of the symbol number at each change time of the symbol number Generating and providing the fourth timing control signal to the modem by the processor.

Synchronization information with the first system may be provided to the first distribution unit based on the first time information from the CU that has previously performed synchronization with the first system.

The first time information may be coordinated universal time (UTC) information, and the first system may be a global positioning system (GPS).

Operations according to the timing control method may be performed in a synchronization plane (S-plane) of the first distribution unit.

Acquiring the first time information from the CU may be performed based on an IEEE 1588 protocol.

In a base station supporting function division according to another embodiment of the present invention for achieving the above object, a first distributed unit (DU) included in the base station supporting function division includes a processor, a modem (MOdulator and DEModulator, MODEM), a memory that communicates electronically with the processor, and instructions stored in the memory, and when the instructions are executed by the processor, the Instructions include a first distribution unit obtaining first time information from a central unit (CU) included in the base station, obtaining synchronization information with a first system based on the first time information, and Based on the synchronization information, it is determined when a system frame number (SFN) is changed, and when the SFN is changed, a signal indicating the changed SFN and a first tick signal having the same cycle as the change cycle of the SFN and generate a first timing control signal comprising, and cause providing of the first timing control signal to the modem.

The instructions include determining, by the first distribution unit, a subframe number of at least one or more sub-frames based on a time point at which the SFN is changed, determining a change time point of each subframe number, and Generating a second timing control signal including a signal indicating the changed subframe number at each change time of the subframe number and a second tick signal having the same cycle as the change cycle of the subframe number, and the second and further cause providing a timing control signal to the modem.

The instructions include the first distribution unit determining a slot number of at least one or more slots constituting the at least one or more subframes, and changing each of the slot numbers based on a change time point of each of the subframe numbers. determining a time point, and generating a third timing control signal including a signal indicating the changed slot number and a third tick signal indicating a change of the slot number at each change time point of the slot number, and the third and further cause providing a timing control signal to the modem.

In the instructions, the first distribution unit determines a symbol number of at least one or more symbols constituting the at least one or more slots, and determines a change time point of each symbol number based on a change time point of each of the slot numbers. and generating a fourth timing control signal including the changed symbol number and a fourth tick signal indicating a change of the symbol number at each change time point of the symbol number, and by the processor, the fourth timing It may be characterized in that it operates to further cause providing a control signal to the modem.

Synchronization information with the first system may be provided to the first distribution unit based on the first time information from the CU that has previously performed synchronization with the first system.

The first time information may be coordinated universal time (UTC) information, and the first system may be a global positioning system (GPS).

In a base station supporting function division according to another embodiment of the present invention for achieving the above object, in the base station supporting function division, by a first communication node including a processor and a modem (MOdulator and DEModulator, MODEM) The timing control method to be performed includes obtaining, by the processor, first time information from a second communication node included in the base station; synchronization with a first system based on the first time information, by the processor. Obtaining information, checking, by the processor, when a system frame number (SFN) is changed based on the synchronization information, by the processor, a signal indicating the changed SFN when the SFN is changed, and Generating a first timing control signal including a first tick signal having a period equal to the change period of the SFN, and providing, by the processor, the first timing control signal to the modem. The first communication node and the second communication node include an O-RAN radio unit (O-RU) and an O-RAN distributed O-DU (O-RAN) according to an open radio access network alliance (O-RAN Alliance) communication standard, respectively. unit).

The timing control method may include determining, by the processor, a subframe number of at least one or more subframes based on a time point at which the SFN is changed, by the processor, each of the subframe numbers Determining a change time point, comprising, by the processor, a signal indicating the changed subframe number at each change time point of the subframe number and a second tick signal having the same period as the change period of the subframe number Generating a second timing control signal, and providing, by the processor, the second timing control signal to the modem.

The timing control method may include determining, by the processor, a slot number of at least one or more slots constituting the at least one or more subframes, by the processor, based on a change time point of each subframe number. and determining, by the processor, a signal indicating the changed slot number at each change time of the slot number and a third tick signal indicating a change of the slot number Generating a third timing control signal, and providing, by the processor, the third timing control signal to the modem.

The timing control method may include determining, by the processor, symbol numbers of at least one or more symbols constituting the at least one or more slots; Determining a change time of each symbol number, by the processor, a fourth timing control signal including the changed symbol number and a fourth tick signal instructing change of the symbol number at each change time of the symbol number Generating and providing the fourth timing control signal to the modem by the processor.

Synchronization information with the first system may be provided to the first communication node based on the first time information from the second communication node that has previously performed synchronization with the first system. .

The first time information may be coordinated universal time (UTC) information, and the first system may be a global positioning system (GPS).

According to an embodiment of the present invention, a DU constituting a base station to which functional division is applied obtains time information and synchronization information from a CU constituting the same base station and a global positioning system (GPS), and synchronizes with the CU based on this. can be done

According to an embodiment of the present invention, a DU constituting a base station to which functional division is applied generates a timing control signal based on time information and synchronization information obtained from a CU and a GPS, and transmits the generated timing control signal to a modem of the DU can be provided to Thus, the modem of the DU can be driven simultaneously with the same timing information as the CU directly having the timing information of the base station. This can improve the reliability of base station functions.

1 is a conceptual diagram illustrating an embodiment of a communication system.
2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.
3 is a conceptual diagram for explaining an embodiment of a communication system to which functional division is applied.
4 is a conceptual diagram for explaining a second embodiment of a communication system to which functional division is applied.
5 is a conceptual diagram for explaining an embodiment of a radio frame transmitted and received in a communication system to which functional division is applied.
6 is a flowchart illustrating an embodiment of a method of generating and transmitting timing information in a communication system to which functional division is applied.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

A communication system to which embodiments according to the present invention are applied will be described. A communication system to which embodiments according to the present invention are applied is not limited to the contents described below, and embodiments according to the present invention can be applied to various communication systems. Here, the communication system may be used in the same sense as a communication network.

Throughout the specification, a network refers to, for example, wireless Internet such as WiFi (wireless fidelity), portable Internet such as WiBro (wireless broadband internet) or WiMax (world interoperability for microwave access), and GSM (global system for mobile communication). ) or CDMA (code division multiple access) 2G mobile communication networks, WCDMA (wideband code division multiple access) or CDMA2000 3G mobile communication networks, HSDPA (high speed downlink packet access) or HSUPA (high speed uplink packet access) It may include a 4G mobile communication network such as a 3.5G mobile communication network, a long term evolution (LTE) network or an LTE-Advanced network, and a 5G mobile communication network.

Throughout the specification, a terminal includes a mobile station, a mobile terminal, a subscriber station, a portable subscriber station, a user equipment, and an access terminal. It may refer to a terminal, a mobile station, a mobile terminal, a subscriber station, a mobile subscriber station, a user device, an access terminal, or the like, and may include all or some functions of a terminal, a mobile station, a mobile terminal, a subscriber station, a mobile subscriber station, a user equipment, an access terminal, and the like.

Here, a desktop computer capable of communicating with a terminal, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, and a smart watch (smart watch), smart glass, e-book reader, PMP (portable multimedia player), portable game device, navigation device, digital camera, DMB (digital multimedia broadcasting) player, digital voice digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player ) can be used.

Throughout the specification, a base station includes an access point, a radio access station, a node B, an evolved nodeB, a base transceiver station, and an MMR ( It may refer to a mobile multihop relay)-BS, and may include all or some functions of a base station, access point, wireless access station, NodeB, eNodeB, transmission/reception base station, MMR-BS, and the like.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

1 is a conceptual diagram illustrating an embodiment of a communication system.

Referring to FIG. 1, a communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). A plurality of communication nodes are 4G communication (eg, long term evolution (LTE), advanced (LTE-A)), 5G communication (eg, new radio (NR)) specified in the 3rd generation partnership project (3GPP) standard ), etc. can be supported. 4G communication may be performed in a frequency band of 6 GHz or less, and 5G communication may be performed in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less.

For example, for 4G communication and 5G communication, a plurality of communication nodes may use a code division multiple access (CDMA)-based communication protocol, a wideband CDMA (WCDMA)-based communication protocol, a time division multiple access (TDMA)-based communication protocol, FDMA (frequency division multiple access)-based communication protocol, OFDM (orthogonal frequency division multiplexing)-based communication protocol, Filtered OFDM-based communication protocol, CP (cyclic prefix)-OFDM-based communication protocol, DFT-s-OFDM (discrete Fourier transform-spread-OFDM) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (Non-orthogonal multiple access), GFDM (generalized frequency) division multiplexing)-based communication protocol, FBMC (filter bank multi-carrier)-based communication protocol, UFMC (universal filtered multi-carrier)-based communication protocol, SDMA (Space Division Multiple Access)-based communication protocol, etc. can be supported. .

In addition, the communication system 100 may further include a core network. When the communication system 100 supports 4G communication, the core network may include a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), a mobility management entity (MME), and the like. there is. When the communication system 100 supports 5G communication, the core network may include a user plane function (UPF), a session management function (SMF), an access and mobility management function (AMF), and the like.

Meanwhile, a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-1 constituting the communication system 100 4, 130-5, 130-6) may each have the following structure.

2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.

Referring to FIG. 2 , a communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 to communicate with each other.

However, each component included in the communication node 200 may be connected through an individual interface or an individual bus centered on the processor 210 instead of the common bus 270 . For example, the processor 210 may be connected to at least one of the memory 220, the transmission/reception device 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260 . The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may include at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2), a plurality of terminals 130- 1, 130-2, 130-3, 130-4, 130-5, 130-6). Base stations 110-1, 110-2, 110-3, 120-1, and 120-2 and terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 The inclusive communication system 100 may be referred to as an “access network”. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the cell coverage of the third base station 110-3. there is. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is a NodeB, an evolved NodeB, a base transceiver station (BTS), Radio base station, radio transceiver, access point, access node, RSU (road side unit), RRH (radio remote head), TP (transmission point), TRP ( transmission and reception ooint), eNB, gNB, etc.

Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a UE (user equipment), terminal, access terminal, mobile Mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, IoT (Internet of Thing) It may be referred to as a device, a mounted device (mounted module/device/terminal or on board device/terminal, etc.), and the like.

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul link or a non-ideal backhaul link, and , information can be exchanged with each other through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to a corresponding terminal 130-1, 130-2, 130-3, and 130 -4, 130-5, 130-6), and signals received from corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 are transmitted to the core network can be sent to

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits MIMO (eg, single user (SU)-MIMO, multi-user (MU)- MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, CA (carrier aggregation) transmission, transmission in an unlicensed band, device to device communication (D2D) (or ProSe ( proximity services)) may be supported. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a base station 110-1, 110-2, 110-3, 120-1 , 120-2) and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be performed. For example, the second base station 110-2 can transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 uses the SU-MIMO scheme. A signal may be received from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4 And each of the fifth terminal 130-5 may receive a signal from the second base station 110-2 by the MU-MIMO method.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, and The terminal 130-4 may receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by CoMP. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes a terminal 130-1, 130-2, 130-3, and 130-4 belonging to its own cell coverage. , 130-5, 130-6) and a CA method. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 controls D2D between the fourth terminal 130-4 and the fifth terminal 130-5. and each of the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively. .

Next, methods for setting and managing a radio interface in a communication system will be described. Even when a method (for example, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a second communication node corresponding thereto is described as a method performed in the first communication node and a method (eg, signal transmission or reception) For example, receiving or transmitting a signal) may be performed. That is, when the operation of the terminal is described, the corresponding base station may perform an operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, a terminal corresponding thereto may perform an operation corresponding to the operation of the base station.

Meanwhile, in a communication system, a base station may perform all functions of a communication protocol (eg, a remote wireless transmission/reception function and a baseband processing function). Alternatively, among all functions of the communication protocol, the remote wireless transmission and reception function may be performed by a transmission reception point (TRP) (eg, flexible (f)-TRP), and the baseband processing function among all functions of the communication protocol may be performed by a baseband unit (BBU) block. The TRP may be a remote radio head (RRH), a radio unit (RU), a transmission point (TP), and the like. A BBU block may include at least one BBU or at least one digital unit (DU). A BBU block may be referred to as a "BBU pool", a "centralized BBU", or the like. The TRP can be connected to the BBU block via a wired fronthaul link or a wireless fronthaul link. A communication system composed of a backhaul link and a fronthaul link may be as follows. When a function split method of a communication protocol is applied, the TRP may selectively perform some functions of a BBU or some functions of medium access control (MAC)/radio link control (RLC).

3 is a conceptual diagram for explaining a first embodiment of a communication system to which functional division is applied.

A communication system according to 4G LTE technology may be configured based on the structure of a digital unit (DU) and a radio unit (RU). DUs are installed in centralized offices of mobile communication companies, and RUs can be installed in cell sites. A Common Public Radio Interface (CPRI) may be used as an interface between the DU and the CU.

On the other hand, the 5G NR communication system may apply wide bandwidth, large-scale MIMO, etc. to achieve 5G service requirements. In order to achieve 5G service requirements using the DU-RU structure of the 4G LTE communication system in the 5G NR communication system, a significantly high transmission rate may be required for the interface between the DU and the RU. For example, a transmission rate required for an interface between a DU and an RU may be 230 Gbps or more. Such an approach can result in huge 5G fronthaul deployment costs.

Meanwhile, the CPRI interface applied to the DU-RU structure of the 4G LTE communication system may be configured to have a unique fronthaul standard developed for each radio access network vendor (RAN vendor). There is a problem in that the entry of new vendors may be substantially restricted due to non-disclosure of unique fronthaul standards developed for each existing vendor.

As a way to solve the problem of the DU-RU structure of the 4G LTE communication system, various 'function split' related technologies are being studied. 'Functional division' may also be referred to as 'functional separation'. Function division may refer to a technique for dividing and operating the function of a base station into a plurality of units. For example, the function division scheme may be implemented through a central unit (CU) and a distributed unit (DU) structure in the 3GPP standard. A CU may mean a logical node that performs a central function of a base station. The CU may perform base station functions such as user data transmission, mobility control, radio access network sharing, positioning, and session management, in addition to functions assigned to the DU. According to a specific embodiment, a CU may also be referred to as a BBU, REC, RCC, C-RAN, or V-RAN. A DU may mean a logical node that performs a distributed function of a base station. A DU may perform a subset of base station functions that are partitioned or distributed according to the function partitioning option. The CU can control the operation of the DU through the fronthaul interface. According to a specific embodiment, a DU may also be referred to as RRH, RRU, RE, or RU. In a communication system to which functional division is applied, the interface capacity required between CU-DUs is reduced, and thus the construction cost of a radio access network (RAN) can be reduced. In addition, an open interface can be used in a communication system to which functional division is applied, and thus entry of new vendors can be made relatively easy.

Referring to FIG. 3, in the CU-DU structure of the 3GPP standard, the function of a base station may be divided based on a plurality of options. For example, the functions of the base station may be divided according to any one of options 1 to 8. For example, the functions of the base station can be divided according to option 7, which means to divide the PHY function. According to option 7, the CU can perform up to the higher-level PHY function (High-PHY) of the base station, and the DU can perform the lower-level PHY function (Low-PHY). In particular, option 7 can be subdivided into options 7-1, 7-2, and 7-3 according to the position of the function division point for the PHY function. A communication system to which function division is applied may have different technical characteristics depending on the function division option. For example, a communication system to which the function division option 7-2 is applied requires only a relatively small fronthaul transmission capacity compared to a communication system to which the function division option 8 is applied, and thus, compression of the fronthaul transmission signal is unnecessary. can have

Meanwhile, the function division scheme may be implemented through an O-RAN distributed unit (O-DU) and an O-RAN radio unit (O-RU) structure in the O-RAN Alliance (open radio access network alliance) standard. O-DU and O-RU structures in the O-RAN Alliance standard may correspond to CU and DU structures in the 3GPP standard.

In this specification, for convenience of description, the configuration and characteristics of the present invention will be described by taking a communication system having a CU-DU structure in the 3GPP standard as an example. However, embodiments of the present invention are not limited thereto. For example, an embodiment of the present invention may be equally or similarly applied to a communication system having O-DU and O-RU structures in the O-RAN Alliance standard.

4 is a conceptual diagram for explaining a second embodiment of a communication system to which functional division is applied.

Referring to FIG. 4 , a communication system may include a base station 400 . For example, the base station 400 may be a 4G LTE-based eNodeB (eNB). Alternatively, the base station 400 may be a 5G NR-based gNodeB (gNB). The function division described with reference to FIG. 3 may be applied to the base station 400 . The base station 400 may include one CU 410 and one or more DUs 420 ... 490 .

Control or interworking between the CU 410 and the DUs 420 ... 490 is C-plane (control plane), U-plane (user plane), M-plane (management plane) , and S-plane (synchronization plane). Real-time control between the CU 410 and the DUs 420 ... 490 may be performed through a C-plane. I/Q sample data transmission and reception between the CU 410 and the DUs 420 ... 490 may be performed through a U-plane. Non-real-time management operations between the CU 410 and the DUs 420 ... 490 may be performed through the M-plane. Synchronization control between the CU 410 and the DUs 420 ... 490 may be performed through the S-planes 415 , 425 , ... 495 .

Synchronization between the CU 410 and the DU 420 ... 490 through the interface between the S-plane 415 of the CU 410 and the S-plane 425 ... 495 of the DUs 420 ... 490 control can be performed. In the S-plane, standard time transfer operations or protocols for time synchronization or timing synchronization may be performed. In the S-plane, a synchronization operation based on a Precision Time Protocol (PTP) that enables accurate synchronization between networks may be performed. For example, a synchronization operation based on the IEEE 1588 protocol may be performed on the S-plane. The IEEE 1588 protocol is a type of PTP, and by using a time stamp generated in hardware, accuracy in nanosecond units can be expected. In the S-plane, an IEEE 1588 grand master clock may be used to support the IEEE 1588 protocol. However, this is only one example for explanation, and synchronization operations in various ways may be performed in addition to the S-plane. For example, in the S-plane, a synchronization operation based on a network time protocol (NTP) or a synchronization operation based on a global positioning system (GPS) may be performed.

5 is a conceptual diagram for explaining an embodiment of a radio frame transmitted and received in a communication system to which functional division is applied.

Referring to FIG. 5, in a communication system to which functional division is applied, one radio frame may be composed of a plurality of sub-frames. For example, one radio frame may consist of 10 subframes. Each radio frame may have a length of 10 ms. Alternatively, each radio frame may be updated in a 10 ms cycle. Each subframe may have a length of 1 ms. Alternatively, each subframe may be updated in a 1 ms cycle.

One subframe may consist of a plurality of slots. One slot may include a plurality of subcarriers in the frequency domain. One slot may have a plurality of symbols in the time domain. A plurality of symbols in the time domain may be OFDM symbols. For convenience, an embodiment in which a plurality of symbols in the time domain are OFDM symbols will be described below as an example, but the embodiment of the present invention is not limited thereto.

The number of slots that one subframe has in the time domain may be set differently according to numerology. For example, the number of slots that one subframe has in the time domain may vary according to a value μ according to a subcarrier spacing (SCS).

μ may have any one of integer values from 0 to 4. As the value of μ is closer to 0, the SCS may be shorter in the frequency domain, and as the value of μ is closer to 4, the SCS may be longer in the frequency domain. As the value of μ is closer to 0, the length of symbols in the time domain may be longer, and as the value of μ is closer to 4, the length of symbols in the time domain may be shorter. The closer the value of μ is to 0, the smaller the number of slots each subframe has in the time domain, and the closer the value of μ is to 4, the more slots each subframe has in the time domain. The number of slots that one subframe has in the time domain may be proportional to ^2μ . For example, according to the embodiment shown in FIG. 5, when μ=1, each subframe may have 2 slots in the time domain. In this case, one radio frame may have 20 slots. Meanwhile, when μ=3, each subframe may have 8 slots in the time domain. In this case, one radio frame may have 80 slots.

Slots may consist of OFDM symbols using Short-CP (cyclic prefix) and may additionally include OFDM symbols using Long-CP. Short-CP may mean normal-CP defined in the 3GPP communication standard. Long-CP is a 3GPP communication standard?Э? It may mean the defined extended-CP.

When the value μ is 0 or 1, all slots may be configured to include OFDM symbols using Long-CP. On the other hand, when the value μ is 2 to 4, some slots may be configured to include OFDM symbols using Long-CP, and the remaining slots may be configured only with OFDM symbols using Short-CP.

6 is a flowchart illustrating an embodiment of a method of generating and transmitting timing information in a communication system to which functional division is applied.

Referring to FIG. 6 , the communication system according to the present invention may include a base station to which functional division is applied. A base station may include a first communication node and a second communication node. The first communication node may mean at least one or more DUs that perform a distributed function of the base station, and the second communication node may mean a CU that performs a central function of the base station. The first and second communication nodes may mean DUs and CUs according to the CU-DU structure in the 3GPP standard described with reference to FIG. 3 .

Synchronization control between CU and DU may be performed through the S-plane. In the S-plane, standard time transfer operations or protocols for time synchronization or timing synchronization may be performed. In the S-plane, a synchronization operation based on a Precision Time Protocol (PTP) that enables accurate synchronization between networks may be performed. For example, a synchronization operation based on the IEEE 1588 protocol may be performed in the S-plane. However, this is only one example for explanation, and synchronization operations of various other types may be performed in the S-plane.

A DU may include a processor and a modem (MOdulator and DEModulator, MODEM). Hereinafter, operations of the DU described with reference to FIG. 6 may be performed by a processor of the DU.

In the S-plane, the DU may receive first time information from the CU (S610). The first time information may be coordinated universal time (UTC) information. The DU may receive the first time information from the CU according to the IEEE 1588 protocol. The DU may receive synchronization information with the GPS from the CU based on the first time information (S620). The DU may receive synchronization information with the GPS from a CU that has already completed synchronization with the GPS. The DU may acquire the SFN value of the GPS from synchronization information with the GPS (S630). Both the CU and DU can be synchronized to have the same SFN value at the same time as the GPS. In this way, the configuration of the present invention has been described by taking the synchronization operation between the CU and the DU based on the previously performed synchronization operation between the CU and the GPS as an example, but the embodiment of the present invention is not limited thereto. In another embodiment of the present invention, the DU may use a timing offset of timing information of the CU and timing information of the GPS in performing timing synchronization with the CU. In timing synchronization between a DU and a CU, the DU may check timing information of the CU based on the first time information. The DU may check GPS timing information based on the second time information. The DU may check a timing offset between timing information of the CU and timing information of the GPS. For timing synchronization with the CU, the DU may initially synchronize with the CU based on the first time information received from the CU. After that, the DU can synchronize with the CU based on the timing offset between the CU and the GPS and the timing information of the GPS.

According to step S630 or the like, the DU can check information about the SFN of the CU or GPS. The DU may perform a timing control operation based on information about the identified SFN. A DU may generate at least one timing control signal for a timing control operation. The DU may provide one or more generated timing control signals to a modem (MOdulator and DEModulator, MODEM) of the DU.

The DU can check when the SFN is changed. When the SFN is changed, the DU may generate the first timing control signal. The first timing control signal may include a signal indicating the changed SFN and a first tick signal having the same cycle as the SFN change cycle. The change period of SFN may be 10 ms. The first tick signal may be a 10 ms tick signal. The DU may provide the generated first timing control signal to the modem of the DU (S640). The first timing control signal may be transmitted to the modem at intervals of 10 ms.

The DU may determine a subframe number of one or more subframes based on a time point at which the SFN is changed. The DU may determine a change time point of each subframe number. The DU may generate the second timing control signal at each change time point of the subframe number. The second timing control signal may include a signal indicating the changed subframe number and a second tick signal having the same period as the subframe number change period. For example, the DU may determine 10 subframe numbers from 0 to 9 whenever the SFN is changed, and determine the timing when each of the 10 subframe numbers is changed. A change period of the subframe number may be 1 ms. The second tick signal may be a 1 ms tick signal. The time required to change the 10 subframe numbers may be the same as the SFN change period. The DU may provide the generated second timing control signal to the modem of the DU (S650). The second timing control signal may be transmitted to the modem at intervals of 1 ms.

The DU may determine slot numbers of at least one or more slots constituting each subframe. The DU may determine the change time of each slot number. The DU may generate a third timing signal at each change time of the slot number. The third timing control signal may include a signal indicating the changed slot number and a third tick signal indicating the change of the slot number. The DU may provide the generated third timing control signal to the modem of the DU (S660).

A third timing signal or a third tick signal may be generated and transmitted whenever the slot number is changed. The third timing signal may be periodically or aperiodically generated and transmitted according to a value μ according to a subcarrier spacing (SCS). As described with reference to FIG. 5, slots may be composed of OFDM symbols using Short-CP and may additionally include OFDM symbols using Long-CP. When the value μ is 0 or 1, all slots may be configured to include OFDM symbols using Long-CP. On the other hand, when the value μ is 2 to 4, some slots may be configured to include OFDM symbols using Long-CP, and the remaining slots may be configured only with OFDM symbols using Short-CP.

When the value μ according to the SCS is 0 or 1, all slots may be set to have the same time duration. That is, when the value μ is 0 or 1, the third timing control signal may be generated and transmitted at regular time intervals. In other words, when the value μ is 0 or 1, the third timing control signal may be periodically generated and transmitted with a predetermined period. Meanwhile, when the value of μ is 2 to 4, some slots may be set to have different time intervals from other slots. That is, when the value μ is 2 to 4, the third timing control signal may be generated and transmitted at an irregular time interval. In other words, when the value μ is 2 to 4, the third timing control signal may be generated and transmitted aperiodically.

The DU may determine symbol numbers of at least one or more symbols constituting each slot. The DU can check the time point at which the symbol number is changed. When the symbol number is changed, the DU may generate a fourth timing control signal including a signal indicating the changed symbol number and a fourth tick signal indicating the change of the symbol number. The DU may provide the generated fourth timing control signal to the modem (S670).

The modem of the DU may receive the first to fourth timing control signals described with reference to FIG. 6 or a part thereof. The modem may obtain timing information based on the received timing control signal. For example, the modem of the DU may receive all of the first to fourth timing control signals described with reference to FIG. 6 and obtain timing information at every moment through the received first to fourth timing control signals. Alternatively, the modem of the DU may receive some of the first to fourth timing control signals described with reference to FIG. 6 and calculate and obtain overall timing information based on the received timing control signals. For example, the modem of the DU may receive a first timing control signal and obtain information about a SFN change point from the first timing control signal. The modem of the DU may obtain overall timing information by calculating a change time of each subframe, a change time of each slot, and a change time of each symbol based on the obtained information about the change time of the SFN. The modem may perform a modem function based on the acquired timing information. Thus, the modem of the DU can perform the modem function with the same timing information as the CU.

According to one embodiment of the present invention described above, a DU constituting a base station to which functional division is applied obtains time information and synchronization information from a CU constituting the same base station and a global positioning system (GPS), and based on this, a DU constituting a base station with a CU motivation can be performed.

According to one embodiment of the present invention described above, the DU constituting the base station to which functional division is applied generates a timing control signal based on time information and synchronization information obtained from the CU and GPS, and the generated timing control signal to the DU can be provided to the modem of Thus, the modem of the DU can be driven simultaneously with the same timing information as the CU directly having the timing information of the base station. This can improve the reliability of base station functions.

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software.

Examples of computer readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes generated by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the claims below. You will be able to.

Claims (20)

In a base station supporting function division, a timing control method performed by a first distributed unit (DU) including a processor and a modem (MOdulator and DEModulator, MODEM),
obtaining, by the processor, first time information from a central unit (CU) included in the base station;
obtaining, by the processor, synchronization information with a first system based on the first time information;
Checking, by the processor, a time point at which a system frame number (SFN) is changed based on the synchronization information;
generating, by the processor, a first timing control signal including a signal indicating the changed SFN and a first tick signal having the same cycle as the SFN change cycle, when the SFN is changed; and
and providing, by the processor, the first timing control signal to the modem. The method of claim 1,
The timing control method,
determining, by the processor, a subframe number of one or more subframes based on a time point at which the SFN is changed;
determining, by the processor, a change time point of each of the subframe numbers;
Generating, by the processor, a second timing control signal including a signal indicating the changed subframe number at each change time point of the subframe number and a second tick signal having the same cycle as the change cycle of the subframe number doing; and
and providing, by the processor, the second timing control signal to the modem. The method of claim 2,
The timing control method,
determining, by the processor, slot numbers of one or more slots constituting the one or more subframes;
determining, by the processor, a change time of each of the slot numbers based on a change time of each of the subframe numbers;
generating, by the processor, a third timing control signal including a signal indicating the changed slot number and a third tick signal indicating a change of the slot number at each change time point of the slot number; and
and providing, by the processor, the third timing control signal to the modem. The method of claim 3,
The timing control method,
determining, by the processor, symbol numbers of at least one or more symbols constituting the at least one or more slots;
determining, by the processor, a change time of each symbol number based on a change time of each slot number;
generating, by the processor, a fourth timing control signal including the changed symbol number and a fourth tick signal indicating a change of the symbol number at each change time point of the symbol number; and
and providing, by the processor, the fourth timing control signal to the modem. The method of claim 1,
Synchronization information with the first system,
Characterized in that, the timing control method is provided to the first distribution unit based on the first time information from the CU that has previously performed synchronization with the first system. The method of claim 5,
The first time information is coordinated universal time (UTC) information,
The timing control method, characterized in that the first system is a global positioning system (GPS). The method of claim 1,
Operations according to the timing control method are performed in an S-plane (synchronization plane) of the first distribution unit. The method of claim 1,
Obtaining first time information from the CU,
Characterized in that it is performed based on the IEEE 1588 protocol, the timing control method. As a first distributed unit (DU) included in a base station supporting functional division,
processor;
Modem (MOdulator and DEModulator, MODEM);
a memory that communicates electronically with the processor; and
Includes instructions stored in the memory;
When the instructions are executed by the processor, the instructions cause the first distribution unit to:
obtaining first time information from a central unit (CU) included in the base station;
obtaining synchronization information with the first system based on the first time information;
Checking when a system frame number (SFN) is changed based on the synchronization information;
when the SFN is changed, generating a first timing control signal including a signal indicating the changed SFN and a first tick signal having the same cycle as the change cycle of the SFN; and
A first distribution unit, characterized in that it is operative to cause providing said first timing control signal to said modem. The method of claim 9,
The instructions may cause the first distribution unit to:
determining a subframe number of one or more subframes based on a time point at which the SFN is changed;
determining a change point of each of the subframe numbers;
generating a second timing control signal including a signal indicating the changed subframe number at each change time point of the subframe number and a second tick signal having the same cycle as the change cycle of the subframe number; and
and further operative to cause providing the second timing control signal to the modem. The method of claim 10,
The instructions may cause the first distribution unit to:
determining slot numbers of at least one or more slots constituting the at least one or more subframes;
determining a change time of each of the slot numbers based on the change time of each of the subframe numbers;
generating a third timing control signal including a signal indicating the changed slot number and a third tick signal indicating a change of the slot number at each change time point of the slot number; and
and further operative to cause providing the third timing control signal to the modem. The method of claim 11,
The instructions may cause the first distribution unit to:
determining symbol numbers of at least one or more symbols constituting the at least one or more slots;
determining a change time of each symbol number based on a change time of each of the slot numbers;
generating a fourth timing control signal including the changed symbol number and a fourth tick signal indicating a change of the symbol number at each change time point of the symbol number; and
The first distribution unit of claim 2, further operable by the processor to cause providing of the fourth timing control signal to the modem. The method of claim 9,
Synchronization information with the first system is provided to the first distribution unit based on the first time information from the CU that has previously performed synchronization with the first system, the first distribution unit . The method of claim 13,
The first time information is coordinated universal time (UTC) information,
The first dispersion unit, characterized in that the first system is a global positioning system (GPS). In a base station supporting function division, a timing control method performed by a first communication node including a processor and a modem (MOdulator and DEModulator, MODEM),
obtaining, by the processor, first time information from a second communication node included in the base station;
obtaining, by the processor, synchronization information with a first system based on the first time information;
Checking, by the processor, a time point at which a system frame number (SFN) is changed based on the synchronization information;
generating, by the processor, a first timing control signal including a signal indicating the changed SFN and a first tick signal having the same cycle as the SFN change cycle, when the SFN is changed; and
providing, by the processor, the first timing control signal to the modem;
The first communication node and the second communication node are connected to an O-RAN radio unit (O-RU) and an O-RAN distributed unit (O-DU) according to an open radio access network alliance (O-RAN alliance) communication standard, respectively. Characterized in that the corresponding, timing control method. The method of claim 15
The timing control method,
determining, by the processor, a subframe number of one or more subframes based on a time point at which the SFN is changed;
determining, by the processor, a change time point of each of the subframe numbers;
Generating, by the processor, a second timing control signal including a signal indicating the changed subframe number at each change time point of the subframe number and a second tick signal having the same cycle as the change cycle of the subframe number doing; and
and providing, by the processor, the second timing control signal to the modem. The method of claim 16
The timing control method,
determining, by the processor, slot numbers of one or more slots constituting the one or more subframes;
determining, by the processor, a change time of each of the slot numbers based on a change time of each of the subframe numbers;
generating, by the processor, a third timing control signal including a signal indicating the changed slot number and a third tick signal indicating a change of the slot number at each change time point of the slot number; and
and providing, by the processor, the third timing control signal to the modem. The method of claim 17
The timing control method,
determining, by the processor, symbol numbers of at least one or more symbols constituting the at least one or more slots;
determining, by the processor, a change time of each symbol number based on a change time of each slot number;
generating, by the processor, a fourth timing control signal including the changed symbol number and a fourth tick signal indicating a change of the symbol number at each change time point of the symbol number; and
and providing, by the processor, the fourth timing control signal to the modem. The method of claim 15
Synchronization information with the first system,
The timing control method characterized in that the first time information is provided to the first communication node based on the first time information from the second communication node that has previously performed synchronization with the first system. The method of claim 19
The first time information is coordinated universal time (UTC) information,
The timing control method, characterized in that the first system is a global positioning system (GPS).

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