KR20210139194A - Method and apparatus for path selection in wireless communication system - Google Patents

Abstract

The present invention relates to a method and apparatus for path selection in a wireless communication system. In accordance with an embodiment of the present invention, the method for path selection in the wireless communication system can comprise: a step of detecting the severance of a first communication path which has received communication service from a first base station of the communication system; a step of checking one or more communication nodes connected to the first communication node; a step of calculating a first variable on each communication path connected from the first base station to the first communication node through the one or more communication nodes; a step of comparing each of the one or more communication nodes based on the first variable, and selecting one target node; and a step of substituting the first communication path through a second communication path formed through the target node. The present invention aims to provide a method and apparatus for path selection in a wireless communication system, which are able to rapidly and efficiently set a communication path.

Description

Method and apparatus for selecting a path in a wireless communication system

The present invention relates to a method and apparatus for selecting a path in a wireless communication system, and more particularly, to a method and apparatus for efficiently performing path selection in a wireless communication system to which a mobile backhaul network is applied.

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) defined in 3rd generation partnership project (3GPP) standards. 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.

4G communication system as well as a frequency band of a 4G communication system (eg, a frequency band of 6 GHz or less) for processing of wireless data rapidly increasing after commercialization of a 4G communication system (eg, a communication system supporting LTE) A 5G communication system (eg, a communication system supporting NR) that can use a higher frequency band than the frequency band (eg, a frequency band of 6 GHz or higher) is being considered.

In a wireless communication system such as 5G or NR, it may be necessary to use a high frequency band such as a millimeter wave (mm-wave) in order to satisfy the requirements of a communication system standard. In a high frequency band such as a millimeter wave, characteristics such as higher signal attenuation, high path loss, low diffraction, and strong straightness may appear than in a low frequency band. Accordingly, it may be necessary to arrange high-density base stations (dense stations) in a communication environment in order to ensure smooth communication in a high frequency band. When wired-type base stations are arranged at high density in a communication environment, physical complexity of an optical transmission line and/or a communication cable may increase and installation costs may increase. Therefore, instead of installing a plurality of wired base stations, a method of configuring a network through a plurality of wireless backhaul base stations is being studied. The mixed access-backhaul network configured through a plurality of wireless backhaul base stations and wireless terminals enables high-density base stations to provide coverage and services to wireless terminals through high-frequency radio signals in a communication environment. However, in order to increase the density or number of wireless backhaul base stations, there is a problem in that the installation cost is increased. Accordingly, a mobile backhaul technique or an access-mobile backhaul technique in which wireless terminals perform a role of a wireless backhaul base station or a mobile backhaul base station by themselves for access by other wireless terminals is being studied.

The mobile backhaul network to which the mobile backhaul technology is applied may include a core network, a fixed backhaul base station, and wireless terminals that function as or receive a service as a mobile backhaul base station. Due to the mobility of wireless terminals serving as mobile backhaul base stations. The structure of the mobile backhaul network may have high variability. A technique for efficiently selecting a connection and/or communication path between wireless terminals and a fixed base station or a mobile backhaul base station adaptively to a communication situation such as movement of wireless terminals or a communication environment may be required.

It is an object of the present invention to solve the above needs, a path capable of quickly and efficiently setting a communication path according to the movement of wireless terminals capable of performing the role of a mobile backhaul base station in a wireless communication system to which a mobile backhaul network is applied. To provide a selection method and apparatus.

In the path selection method performed by the first communication node of the communication system according to an embodiment of the present invention, the first communication node is provided with a communication service from the first base station of the communication system, the disconnection of the first communication path sensing, identifying at least one communication node connected to the first communication node, for each of the at least one communication node identified, the first communication from the first base station through the at least one communication node calculating a first variable for each communication path leading to a node, selecting one target node by comparing each of the at least one communication node based on the first variable, and selecting the selected target node It may be characterized in that it comprises the step of replacing the first communication path through the second communication path formed through.

According to an embodiment of the present invention, in a wireless communication system to which a mobile backhaul network is applied, a change in a communication situation or environment, such as movement of communication nodes capable of performing the role of an access-backhaul node or a mobile backhaul base station, or movement of a communication obstacle Accordingly, a path selection method and apparatus capable of quickly and efficiently setting a communication path may be provided. A communication node (hereinafter, referred to as a first communication node) that has been provided with a communication service through a predetermined communication path from a fixed base station may check a list of communication nodes connected thereto when disconnection of the communication path is detected. The first communication node may select a communication path by selecting one communication node based on a value of a first variable (such as link capacity or node quality) that is checked for communication nodes connected thereto. Thereby, selection of a new communication path for replacing the disconnected communication path can be performed quickly and efficiently.

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.
3A to 3C are conceptual diagrams for explaining an embodiment of a communication system including a mobile backhaul network.
4A and 4B are exemplary diagrams for explaining an embodiment of a method of performing path selection based on a value of a first variable calculated for each communication node in a communication system.
5 is an exemplary diagram for explaining a first embodiment of a method for a first communication node to select a communication path in a communication system.
6 is an exemplary diagram for explaining a second embodiment of a method for a first communication node to select a communication path in a communication system.

Since the present invention can have various changes and can 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 it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it is understood that the other component may be directly connected or connected to the other component, but other components may exist in between. it should be On the other hand, when it is mentioned that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

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

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

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

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

Here, a desktop computer that can communicate with a terminal, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, a smart watch (smart watch), smart glass, e-book reader, PMP (portable multimedia player), portable game console, 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 is an access point, a radio access station, a Node B, an advanced nodeB, a base transceiver station, MMR ( It may refer to mobile multihop relay)-BS, etc., and may include all or some functions of a base station, an access point, a radio access station, a Node B, an eNodeB, a transceiver base station, and an MMR-BS.

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

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

1, the communication system 100 is 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), LTE-A (advanced)), 5G communication (eg, NR (new radio)) defined in the 3rd generation partnership project (3GPP) standard. ) 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, a plurality of communication nodes for 4G communication and 5G communication are CDMA (code division multiple access) based communication protocol, WCDMA (wideband CDMA) based communication protocol, TDMA (time division multiple access) 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), and a mobility management entity (MME). have. 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.

On the other hand, a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-) 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 , the 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 of the components included in the communication node 200 may not be connected to the common bus 270 but to the processor 210 through an individual interface or an individual bus. For example, the processor 210 may be connected to at least one of the memory 220 , the transceiver 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 mean 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 be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be configured as 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 and 120 - 2 , and 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, 120-2 and terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 The comprising 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. have. 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, 120-2 is a NodeB (NodeB), an advanced NodeB (evolved NodeB), a BTS (base transceiver station), Radio base station (radio base station), radio transceiver (radio transceiver), access point (access point), access node (node), RSU (road side unit), RRH (radio remote head), TP (transmission point), TRP ( transmission and reception ooint), eNB, gNB, and the like.

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

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. , 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 the corresponding terminals 130-1, 130-2, 130-3, 130 -4, 130-5, 130-6), and the signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is 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, direct communication between terminals (device to device communication, D2D) (or ProSe ( proximity services)), and the like. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 is the base station 110-1, 110-2, 110-3, and 120-1. , 120-2) and corresponding operations, 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 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method, and the fourth terminal 130-4 may transmit a signal based on the SU-MIMO method. 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 terminals 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 fourth 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 the CoMP method. A plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) each of the terminals (130-1, 130-2, 130-3, 130-4) belonging to its own cell coverage , 130-5, 130-6) and the CA method can transmit and receive signals. 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 wireless interface in a communication system will be described. Even when a method (eg, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a second communication node corresponding thereto is a method (eg, a method corresponding to the method performed in the first communication node) For example, reception or transmission of a signal) may be performed. That is, when the operation of the terminal is described, the corresponding base station may perform the operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, the corresponding terminal may perform the 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 radio transmission/reception function, a baseband processing function). Alternatively, a remote radio transmission/reception function among all functions of a communication protocol may be performed by a transmission reception point (TRP) (eg, f(flexible)-TRP), and a baseband processing function among all functions of a communication protocol may be performed by a baseband unit (BBU) block. The TRP may be a remote radio head (RRH), a radio unit (RU), or a transmission point (TP). The 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”, “centralized BBU”, or the like. The TRP may be connected to the BBU block through 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 the function split method of the communication protocol is applied, the TRP may selectively perform some functions of the BBU or some functions of medium access control (MAC)/radio link control (RLC).

3A to 3C are conceptual diagrams for explaining an embodiment of a communication system including a mobile backhaul network.

Referring to FIG. 3A , the communication system 300 may include a core network (CN) 310 , and an access network. Here, the core network 310 may be the same as or similar to the core network described with reference to FIG. 1 . The core network supporting 4G communication may include an MME, an S-GW, a P-GW, and the like. The core network supporting 5G communication may include AMF, UPF, P-GW, and the like.

The access network may include at least one fixed base station (320, 330), and at least one wireless terminal (340-1, 340-2, 340-3, 340-4, 340-5, 340-6). . At least one fixed base station (320, 330) may be the same as or similar to the base stations (110-1, 110-2, 110-3, 120-1, 120-2) described with reference to FIG. At least one wireless terminal (340-1, 340-2, 340-3, 340-4, 340-5, 340-6) is the terminal 130-1, 130-2, 130-3 described with reference to FIG. , 130-4, 130-5, 130-6) may be the same or similar. Communication nodes constituting the communication system 300 may be configured the same as or similar to the communication node 200 illustrated in FIG. 2 . The at least one fixed base station 320 and 330 may include a macro base station 320 and a small base station 330 . The macro base station 320 and/or the small base station 330 may be connected to an end node of the core network through a wired backhaul link or a wireless backhaul link. 3 shows an embodiment in which the macro base station 320 and the small base station 330 are arranged one by one in the communication system 300 for convenience of explanation, but the embodiment of the present invention is not limited thereto. For example, the communication system 300 may include at least one macro base station 320 and/or at least one small base station 330 . Alternatively, the communication system 300 may include communication nodes identical to or similar to the BBU block and/or TRP described with reference to FIG. 1 . For example, TRP may support a remote radio transmission/reception function among all functions of a communication protocol, and a baseband processing function for TRP may be performed in the BBU block. A BBU block may belong to an access network or a core network. The BBU block may be located in the AMF, UPF, MME, S-GW, or macro base station. Alternatively, the BBU block may be located independently of each of the AMF, UPF, MME, S-GW, and macro base station. For example, the BBU block may be composed of a logical functional block between the macro base station and the AMF (or UPF). The BBU block may support a plurality of TRPs, and may be connected to each of the plurality of TRPs using a wired fronthaul link or a wireless fronthaul link. The link between the BBU block and the TRP may be referred to as a “fronthaul link”. Each TRP may be connected to a BBU block through a wired fronthaul link or a wireless fronthaul link, and communicate to a wireless terminal within a predetermined communication coverage area based on a communication protocol (eg, 4G communication protocol, 5G communication protocol) service can be provided.

The macro base station 320 may be connected to the core network 310 (eg, AMF, UPF, MME, S-GW, etc.) using a wired backhaul link or a wireless backhaul link. The macro base station 320 is based on a predetermined communication protocol (eg, 4G communication protocol, 5G communication protocol, etc.), the wireless terminals in the cell coverage (340-1, 340-2, 340-3, 340-4, 340-5, 340-6) may provide a communication service. The macro base station 320 may form a relatively wide cell coverage compared to the small base station 330 . The small base station 330 may be connected to the core network 310 or the macro base station 320 using a wired backhaul link or a wireless backhaul link. The small base station 330 may provide a communication service to the wireless terminal 340-1 within cell coverage based on a predetermined communication protocol (eg, a 4G communication protocol, a 5G communication protocol, etc.). The small base station 330 may form a relatively narrow cell coverage compared to the macro base station 320 .

In an embodiment of the communication system 300 , a mixed access-backhaul network including a plurality of base stations and wireless terminals connected to the core network using a wired or wireless backhaul link may be configured. The mixed access-backhaul network enables high-density base stations to provide coverage and services to wireless terminals through high-frequency radio signals in a communication environment.

At least one fixed base station (320, 330) is directly connected to the at least one wireless terminal (340-1, 340-2, 340-3, 340-4, 340-5, 340-6) within the cell coverage by wireless communication to provide communication services. Alternatively, at least one fixed base station (320, 330) is indirectly connected to at least one wireless terminal (340-1, 340-2, 340-3, 340-4, 340-5, 340-6) through another communication node. to provide communication services. A wireless terminal directly providing a communication service to the at least one fixed base station 320 , 330 and a wireless terminal indirectly providing a communication service may be determined differently depending on a communication environment and/or a communication situation.

The macro base station 320 is a direct link with some of the at least one wireless terminal (340-1, 340-2, 340-3, 340-4, 340-5, 340-6) in the cell coverage is easy to communicate with terminals can be connected to provide communication services. For example, the macro base station 320 may provide a communication service by being directly connected to the second terminal 340-2, the third terminal 340-3, and the fifth terminal 340-5 through a direct link. Meanwhile, the macro base station 320 may be connected to the small base station 330 by a wireless backhaul link to indirectly provide a communication service to the first terminal 340-1.

The fronthaul link or the backhaul link may be referred to as an 'X-hole link'. A network configured including an X-hole link may be referred to as an 'X-hole network'. The X-hole network may be located between the access network and the core network, and may support communication between the access network and the core network. Communication nodes belonging to the X-hole network may be connected using the X-hole link. A communication system including an access network, an X-hole network, and a core network may be referred to as an “integration communication system”. Communication nodes belonging to the integrated communication system (eg, MME, S-GW, P-GW, AMF, UPF, BBU block, DU (distributed unit), CU (central unit), base station, TRP, terminal, etc.) It may be configured the same as or similar to the communication node 200 shown in 2 .

In addition, the UPF (or S-GW) of the integrated communication system may refer to an end communication node of the core network that exchanges packets (eg, control information, data) with the base station, and the AMF (or , MME) may refer to a communication node of a core network that performs a control function in a radio access section (or interface) of the terminal. Here, each of the backhaul link, the fronthaul link, the Xhaul link, the BBU block, S-GW, MME, AMF, and UPF is a function of a communication protocol according to radio access technology (RAT) (eg, a function of an Xhaul network). , the function of the core network) may be referred to by different terms.

In a wireless communication system such as 5G or NR, it may be necessary to use a high frequency band such as a millimeter wave (mm-wave) in order to satisfy the requirements of a communication system standard. In a high frequency band such as a millimeter wave, characteristics such as higher signal attenuation, high path loss, low diffraction, and strong straightness may appear than in a low frequency band. Accordingly, it may be necessary to arrange high-density base stations (dense stations) in a communication environment in order to ensure smooth communication in a high frequency band.

A communication system may include a plurality of macro base stations and/or small base stations. In an embodiment of the communication system, an access-backhaul hybrid network including a plurality of base stations and wireless terminals connected to a core network using a wired or wireless backhaul link may be configured. The mixed access-backhaul network enables high-density base stations to provide coverage and services to wireless terminals through high-frequency radio signals in a communication environment. However, in order to increase the density or number of wireless backhaul base stations, there is a problem in that the installation cost is increased. Accordingly, a mobile backhaul technique or an access-mobile backhaul technique in which wireless terminals perform a role of a wireless backhaul base station or a mobile backhaul base station by themselves for access by other wireless terminals is being studied.

The wireless terminals 340-1, 340-2, 340-3, 340-4, 340-5, 340-6 may perform a function as a mobile backhaul base station according to their own functions, communication environments, communication conditions, and the like. have. Wireless terminals capable of functioning as mobile backhaul base stations may also be referred to as potential mobile backhaul base stations (PBBSs).

Some or all of the at least one wireless terminal 340 - 1 , 340 - 2 , 340 - 3 , 340 - 4 , 340 - 5 , 340 - 6 of the communication system 300 may be configured to perform other wireless For the access of the terminal, it can perform the role of a mobile backhaul base station by itself. The mobile backhaul base station may be connected to a fixed base station or another mobile backhaul base station by a wireless backhaul link to provide communication services to other wireless terminals. In other words, at least one wireless terminal may be connected to another wireless terminal capable of performing the role of a mobile backhaul base station to receive a communication service. For example, the third terminal 340-3 is connected to the macro base station 320 by a wireless backhaul link, and provides a communication service to the second terminal 342-2 and/or the fourth terminal 340-4 as a mobile backhaul base station. can provide The second terminal 342-2 may be directly connected to the macro base station 320 to receive a communication service directly from the macro base station 320, or a third terminal 342-2 capable of performing the role of a mobile backhaul base station. 3) and may receive a communication service from the third terminal 342-3. The fourth terminal 340-4 communicates indirectly from the macro base station 320 through the relay of the third terminal 340-3 and/or the fifth terminal 340-5 that can serve as a mobile backhaul base station. service can be provided. The fourth terminal 340-4 receives the relay of the third terminal 340-3 capable of serving as a mobile backhaul base station, and at the same time, the fifth terminal 340-5 and/or the sixth terminal as a mobile backhaul base station. It may provide a relay service for (340-6). The fifth terminal 340-5 may receive a communication service directly from the macro base station 320, or the third terminal 340-3 and the fourth terminal 340-4 that may serve as a mobile backhaul base station. ) can be provided indirectly through the relay. A structure including a mobile backhaul base station and a fixed base station can be expressed as a 'mobile backhaul network'. The sixth terminal 340-6 cannot receive a direct communication service from the macro base station 320, but instead the third terminal 340-3 and the fourth terminal 340-4 that can serve as a mobile backhaul base station. ), or through a relay through the fifth terminal 340 - 5, the communication service may be indirectly provided. A structure including a mobile backhaul base station and a fixed base station can be expressed as a 'mobile backhaul network'.

Various communication obstacles 350-1, 350-2, 350-3, such as buildings, people, and other structures, may exist in the communication environment. Depending on the communication situation, the radio links formed between the communication nodes may be blocked, disconnected, or blocked due to the communication obstacles 350-1, 350-2, 350-3, or the reception quality may be deteriorated. can When a communication obstacle exists between the respective communication nodes, the mutual link may not satisfy the line of sight (LOS) condition. Each communication node may determine whether to connect directly or indirectly through a relay of another communication node based on whether the LOS condition of the mutual link is satisfied, the distance between each other, and other various communication environment and/or communication situation conditions.

For example, the radio link between the fifth terminal 340-5 and the macro base station 320 may satisfy the LOS condition, and the fifth terminal 340-5 and the macro base station 320 may perform direct communication. However, the fifth terminal (340-4, 340-5) communicates indirectly through a relay of another communication node rather than directly communicating with the macro base station 320 due to problems such as distance from the macro base station 320. It may be more advantageous to For example, the fifth terminal 340-5 may receive a communication service indirectly from the macro base station 320 through the relay of the third and fourth terminals 340-3 and 340-4. The fifth terminal 340-5 can receive the communication service indirectly from the macro base station 320 by using the third and fourth terminals 340-3 and 340-4 as upper nodes or parent nodes. have.

On the other hand, direct communication between the fourth and sixth terminals 340-4 and 340-6 and the radio link between the macro base station 320 is not easy, such as not satisfying the LOS condition due to the presence of a communication obstacle (not shown). may be judged not to be. In this case, the fourth and sixth terminals 340 - 4 and 340 - 6 are not directly connected to the macro base station 320 , but are connected to other communication nodes that facilitate direct communication and indirectly communicate from the macro base station 320 . service can be provided. For example, the fourth terminal 340-4 is directly connected to the third terminal 340-3 and/or the fifth terminal 340-5, etc. for easy communication, and indirectly provides a communication service from the macro base station 320. can be provided The sixth terminal 340-6 is connected to the fourth terminal 340-4 and/or the fifth terminal 340-5, etc. for easy direct communication, and indirectly receives a communication service from the macro base station 320. can The sixth terminal 340-6 may receive a communication service indirectly from the macro base station 320 by using the fourth terminal 340-4 and/or the fifth terminal 340-5 as an upper node or a parent node. have. The sixth terminal 340 - 6 indirectly provides a communication service through the fourth terminal 340 - 4 and/or the fifth terminal 340 - 5 , etc. rather than directly receiving the communication service from the macro base station 320 . By being provided, a more stable communication service can be provided. On the other hand, it can be determined that direct communication between the sixth terminal 340-6 and the second terminal 340-2 is easy, but between the second and sixth terminals 340-2 and 340-6. It may be determined that direct communication with each other is not easy due to the existence of the communication obstacle 350 - 1 of the . In this case, it may not be easy for the second terminal 340 - 2 to perform relaying for the sixth terminal 340 - 6 .

A communication network formed based on communication nodes to which a mobile backhaul technology is applied to perform a role of a mobile backhaul base station may be referred to as a mobile backhaul network. A communication system including a mobile backhaul network may include a core network, a fixed base station, and wireless terminals that function as or receive a service as a mobile backhaul base station.

Wireless terminals capable of simultaneously configuring an access network (or an access network) and a backhaul network (or a mobile backhaul network) may be referred to as 'access-backhaul nodes'. The one or more wireless terminals 340-1, 340-2, 340-3, 340-4, 340-5, 340-6 of the communication system 300 may serve as an access-backhaul node and an end node of the access network. Alternatively, it may serve as a mobile backhaul base station (or wireless backhaul base station) of a mobile backhaul network. A communication network composed of one or more access-backhaul nodes may also be referred to as an access-backhaul network.

In an embodiment of the communication system, the structure of each communication node constituting the access-backhaul network may be expressed by borrowing terms used in graph theory. In an embodiment of the communication system, a path selection operation may be performed based on the structure of each communication node expressed based on terms used in graph theory. For example, the macro base station 320 corresponding to the fixed base station may be referred to as the node-a 320, and the second to sixth terminals 340-2, 340-3, 340-4 corresponding to the access-backhaul node. , 340-5, 340-6) are Node-b(340-2), Node-c(340-3), Node-d(340-4), Node-e(340-5), Node-f, respectively. (340-6), etc. can be called. Here, the method of referring to communication nodes, such as node-a to node-f, is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

Links between communication nodes that are determined to be capable of mutual direct connection are (a,b), (a,c), (a,e), (b,c), (b,d), (c, d), (d,e), (d,f), (e,f), and the like. For example, (a, b) may mean a link between the node-a (320) and the node-b (340-2).

The shape of the entire network composed of each communication node can be expressed as a graph G = (V, E). Here, V may mean a set of communication nodes constituting the access backhaul network. On the other hand, E may mean a set of links between communication nodes that are determined to be capable of performing a direct connection to each other. For example, the set V may be expressed as V={a, b, c, d, e, f}. The set E is E={(a,b), (a,c), (a,e), (b,c), (b,d), (c,d), (d,e), (d ,f), (e,f)}. The set E may vary depending on the communication situation. For example, when it is determined that direct communication between the node-a (320) and the node-d (340-4), the node-a (320) and the node-e (340-5) is not easy according to the communication situation, the set E = {(a,b), (a,c), (b,c), (b,d), (c,d), (d,e), (d,f), (e, f)} can be changed. The expression method for such a communication network structure is merely an example for convenience of description, and embodiments of the present invention are not limited thereto and may include various expression methods and embodiments of a control method according thereto.

Based on the graph G defined as G = (V, E), a hierarchy or a hierarchical structure of a communication network may be expressed. In other words, the graph G defined as G = (V, E) may correspond to the hierarchy or hierarchical structure of the communication network. A first variable corresponding to a variable or function calculated or obtained to evaluate a sequence close to the node-a 320 corresponding to a fixed base station in the communication network, or each communication node and/or a communication path formed through each communication node A layer hierarchy of each communication node may be determined according to an order of evaluation based on and the like. Here, the first variable for each communication node may correspond to, for example, link capacity or node quality (NQ). Each communication node may correspond to a specific layer (eg, a primary layer, an nth layer, etc.).

Each of communication nodes such as an access-backhaul node constituting an access-backhaul network may recognize an upper node or a parent node that is connected to itself in a layer hierarchical structure and located in a layer higher than itself. Meanwhile, each communication node may recognize a lower node or a child node that is connected to itself in a layer hierarchical structure and located in a layer lower than itself. For an arbitrary node-x, a communication node corresponding to a node higher than node-x in the layer hierarchy or a parent node may be expressed as x.π. Here, since there is no upper node of the node-a 320 corresponding to the fixed base station or does not correspond to a component of the access-backhaul network, a.π may be expressed as NIL or NULL. Meanwhile, each communication node may recognize a node directly connected to itself from among the access-backhaul nodes in the structure of the communication network. For any node-x, a set of adjacent nodes or a list of adjacent nodes corresponding to a set or list of communication nodes directly connected to node-x may be expressed as x.Adj. In the neighbor node list x.Adj for an arbitrary node-x, the order of elements is in descending order from the node having the largest first variable in the path from the fixed base station through each node corresponding to each element to the corresponding node can be set to Such an expression method for an upper node or a neighboring node is merely an example for the convenience of description, and embodiments of the present invention are not limited thereto and may include various expression methods and embodiments of a control method according thereto.

For example, V={a, b, c, d, e, f} and E={(a,b), (a,c), (a,e), (b,c), (b,d) , (c,d), (d,e), (d,f), (e,f)}, node-b(340-2) forming a direct link with node-a(320), node -c (340-3) and node-e (340-5) can be seen as corresponding to the primary layer. In this case, the node-d (340-4) and the node forming a link with the node-b (340-2), the node-c (340-3), and the node-e (340-5) corresponding to the primary layer -f (340-6) can be seen as corresponding to the secondary layer. Here, the upper node of the node-b (340-2) corresponding to the first layer may be expressed as b.π, and b.π may correspond to the node-a (320). Similarly, the upper nodes of each of the node-c(340-3) and node-e(340-5) corresponding to the primary layer may be expressed as c.π and e.π, and c.π and e All .π may correspond to node-a (320). On the other hand, the upper node of each of the node-d(340-4) and node-f(340-6) corresponding to the secondary layer may be expressed as d.π and f.π, and d.π is the node- b(340-2), node-c(340-3) and/or node-e(340-5), and f.π may correspond to node-e(340-5). When each node is compared in descending order based on the first variable from node-a 320 corresponding to the fixed base station to each node, node-c (340-3), node-b (340-2), node- It may be an order (descending order) such as e(340-5), node-d(340-4), node-f(340-6). Node-b (340-2), Node-c (340-3), Node-d (340-4), Node-e (340-5), and Node-f (340-6) each of the neighboring node list is It may be expressed as b.Adj, c.Adj, d.Adj, e.Adj and f.Adj. where b.Adj={c, d} , c.Adj={b, d} , d.Adj={c, b, e, f} , e.Adj={d, f} , f may be .Adj={e, d}.

On the other hand, V={a, b, c, d, e, f} and E={(a,b), (a,c), (b,c), (b,d), (c,d) , (d,e), (d,f), (e,f)}, node-b (340-2), node-c (340-3) forming a direct link with node-a (320) ) can be seen as corresponding to the first layer. In this case, the node-b 340-2 and the node-c 340-3 corresponding to the primary layer and the node-d 340-4 forming a link with the node-d 340-4 correspond to the secondary layer. . In addition, node-e (340-5) and node-f (340-6) that form a link with node-d (340-4) corresponding to the secondary layer may be regarded as corresponding to the tertiary layer. Here, the upper nodes of the node-b (340-2) and the node-c (340-3) corresponding to the first layer may be expressed as b.π and c.π, b.π and c.π may correspond to node-a (320). The upper node of the node-d(340-4) corresponding to the secondary layer may be expressed as d.π, where d.π is the node-b(340-2) and/or the node-c(340-3). ) may be applicable. Upper nodes of node-e(340-5) and node-f(340-6) corresponding to the tertiary layer can be expressed as e.π and f.π, and e.π and f.π are nodes It may correspond to -d(340-4). If each node is compared in descending order based on the first variable from node-a 320 corresponding to the fixed base station to each node, node-c (340-3), node-b (340-2), node- d(340-4), node-f(340-6), node-e(340-5) may be in the same order (descending order). Node-b (340-2), Node-c (340-3), Node-d (340-4), Node-e (340-5), and Node-f (340-6) each of the neighboring node list is It may be expressed as b.Adj, c.Adj, d.Adj, e.Adj and f.Adj. where b.Adj={c, d} , c.Adj={b, d} , d.Adj={c, b, f, e} , e.Adj={d, f}, f may be .Adj={d, e}.

The hierarchical structure configured through the first and second layers described above, and/or the hierarchical structure configured through the first to third layers and its expression method are merely examples for convenience of description, and the embodiment of the present invention is It is not limited to this. For example, the layer hierarchical structure between communication nodes constituting the communication network may be configured to include a higher-order (n-order) layer according to the communication situation and/or communication environment such as the arrangement situation of communication nodes and/or communication obstacles. may be

A communication node corresponding to a fixed base station may be connected to the core network to provide communication services to lower nodes located in a lower layer than itself. A communication node corresponding to the first layer may receive a communication service directly from a fixed base station. Communication nodes corresponding to the 2nd or 3rd or higher layer other than the fixed base station or the 1st layer request a relay role from their upper node, and communicate from the fixed base station (or core network) indirectly through the upper node. service can be provided. Communication nodes corresponding to the first or second layer or higher may deliver or provide communication services to their lower nodes by performing a relay role based on a relay request from their lower nodes.

Due to the mobility of wireless terminals capable of functioning as access-backhaul nodes or mobile backhaul base stations. The structure of the access-backhaul network or the mobile backhaul network may have high variability. For example, the wireless terminals may correspond to user equipment (UE) possessed by a user such as a person, or may correspond to a terminal mounted on a vehicle to provide a V2X communication function.

Wireless terminals may have high mobility due to movement of a user or a vehicle. As wireless terminals move, the state of links between wireless terminals and a fixed base station, and/or links between wireless terminals, may change. Alternatively, the state of links between wireless terminals and a fixed base station and/or links between wireless terminals may change due to movement of communication obstacles existing in the communication environment, or the like. A technique for efficiently selecting a connection and/or communication path between wireless terminals and a fixed base station or a mobile backhaul base station adaptively to a communication situation such as movement of wireless terminals or a change in a communication environment may be required.

On the other hand, if a path change is performed more frequently than necessary to support fast path selection, the load of the system may be increased and efficiency may be reduced. That is, when a communication situation or communication environment change such as movement of wireless terminals capable of performing the role of the end node of the access network and/or the role of the mobile backhaul base station of the mobile backhaul network as an access-backhaul node occurs, quickly and stably, In addition, a technique for performing path setting with low complexity may be required. 3B and 3C show a situation in which the structure of an access-backhaul network or a mobile backhaul network must be reconfigured due to a change in the communication environment due to movement of a communication obstacle, etc. in an embodiment of the communication system shown in FIG. 3A. can be seen as

Referring to FIG. 3B , in an embodiment of the communication system shown in FIG. 3A , a situation in which the structure of an access-backhaul network or a mobile backhaul network must be reconfigured due to movement of some communication obstacles 350-3 is shown. can Specifically, V={a, b, c, d, e, f} and E={(a,b), (a,c), (b,c), (b,d), (c, d), (d,e), (d,f), (e,f)}, due to the movement of the communication obstacle 350-3 in the G = (V,E) structure, the node-a 320 and the node It can be seen that the situation in which the radio link (a, b) between -b (340-2) is cut off or does not satisfy the LOS condition is shown. Here, for convenience of explanation, the small base station 330 and the first terminal 340-1 that do not constitute the G=(V,E) structure are omitted in FIG. 3B .

When the radio link (a, b) between the node-a (320) and the node-b (340-2) is cut off, the node-b (340-2) does not receive direct communication service from the node-a (320). may not be able to The node-b 340 - 2 may have to be indirectly connected to the node-a 320 through other communication nodes in order to receive the communication service from the node-a 320 . For example, the node-b 340-2 may be indirectly connected to the node-a 320 through the relay of the node-c 340-3. In other words, the node-c (340-3) may serve as a mobile backhaul base station to connect the node-b (340-2) and the node-a (320).

Specifically, when it is determined that the direct link (a, b) with the node-a 320 corresponding to the fixed base station is disconnected, the node-b 340-2 corresponds to the priority element in its neighbor node list. node can be checked. For example, if the list of neighboring nodes of node-b 340-2 is equal to b.Adj={c, d}, node-b 340-2 corresponds to node-c corresponding to c, which is a priority element in b.Adj. A relay request signal may be transmitted to (340-3). The node-c 340 - 3 may transmit a relay role permission request signal to the node-a 320 to perform a relay role for the node-b 340 - 2 . The node-a 320 may transmit a relay role permission signal that permits the node-c 340 - 3 to perform the relay role for the node-b 340 - 2 . The node-c (340-3) transmits a signal indicating that the relay role for the node-b (340-2) is permitted, or a signal indicating that it will perform the relay role for the node-b (340-2). -b (340-2) can be transmitted. Accordingly, the node-b (340-2) can receive the communication service indirectly from the node-a (320) using the node-c (340-3) as an upper node or a parent node.

When the structure of the communication network is changed as described above, in the G=(V,E) structure, the set E is E={(a,c), (b,c), (b,d), (c,d), (d,e), (d,f), (e,f)}. In this case, among the node-b 340-2 and the node-c 340-3 that previously corresponded to the primary layer, the node-b 340-2 may correspond to the secondary layer. That is, the primary layer is composed of node-c (340-3), the secondary layer is composed of node-b (340-2) and node-d (340-4), and the tertiary layer is composed of node-e It may be changed to consist of (340-5) and node-f (340-6). On the other hand, c.π corresponds to node-a(320), b.π and d.π correspond to node-c(340-3), and e.π and f.π correspond to node-d(340-). 4) may be changed. In addition, the order (descending order) of the first variable from node-a 320 corresponding to the fixed base station to each node is node-c (340-3), node-b (340-2), node-d ( 340-4), node-f (340-6), and node-e (340-5) may be changed. Each of the neighbor node lists set based on the layer hierarchy structure and the first variable for each node is, b.Adj={c, d}, c.Adj={b, d}, d.Adj={c , b, f, e}, e.Adj={d, f}, f.Adj={d, e}.

Referring to FIG. 3C , in an embodiment of the communication system shown in FIG. 3A , a situation in which the structure of an access-backhaul network or a mobile backhaul network must be reconfigured due to movement of some communication obstacles 350-2 is shown. can Specifically, V={a, b, c, d, e, f} and E={(a,b), (a,c), (a,e), (b,c), (b, d), (c, d), (d, e), (d, f), (e, f)} in the structure of G = (V, E), due to the movement of the communication obstacle 350 - 2 A situation in which the radio link (a, e) between the a ( 320 ) and the node-e ( 340 - 5 ) is cut off or does not satisfy the LOS condition can be seen as illustrated. Here, for convenience of explanation, the small base station 330 and the first terminal 340-1 that do not constitute the G=(V,E) structure are omitted in FIG. 3C .

When the radio link (a, e) between the node-a (320) and the node-e (340-5) is cut off, the node-e (340-5) does not receive a direct communication service from the node-a (320). may not be able to The node-e 340 - 5 may need to be indirectly connected to the node-a 320 through other communication nodes in order to receive the communication service from the node-a 320 . For example, the node-e 340-5 may be indirectly connected to the node-a 320 through a relay between the node-c 340-3 and the node-d 340-4. In other words, the node-c (340-3) and the node-d (340-4) may serve as a mobile backhaul base station to connect the node-e (340-5) and the node-a (320). .

Specifically, when it is determined that the direct link (a, e) with the node-a 320 corresponding to the fixed base station is disconnected, the node-e 340-5 corresponds to the priority element in its neighbor node list. node can be checked. For example, if the list of adjacent nodes of node-e 340-5 is equal to e.Adj={d, method, node-e(340-5) is node-d corresponding to d, which is a priority element in e.Adj. A relay request signal may be transmitted to (340-4). In order to perform a relay role for the node-e 340 - 5 , the node-d 340 - 4 may identify a node corresponding to the priority element in its neighbor node list. For example, if the list of adjacent nodes of node-d (340-4) is equal to d.Adj={c, b, e, method}, node-d (340-4) corresponds to c, which is a priority element in d.Adj. It is possible to transmit a relay role permission request signal to the node-c 340 - 3 . The node-c 340 - 3 may transmit a relay role permission request signal to the node-a 320 based on the relay role permission request signal from the node-d 340 - 4 . In the node-a (320), the node-c (340-3) serves as a relay for the node-d (340-4), and the node-d (340-4) is the node-e (340-5). A relay role permission signal that permits to perform a relay role may be transmitted. Node-c 340-3 is a signal indicating that it is authorized to act as a relay for node-d 340-4 and node-e 340-5, or node-d 340-4 and node- A signal indicating that it will serve as a relay for e(340-5) may be transmitted to node-d(340-4). The node-d (340-4) sends a signal indicating that it has been granted the relay role for the node-e (340-5), or a signal indicating that it will perform the relay role for the node-e (340-5). Node-e 340-5 may transmit. Accordingly, the node-e (340-5) can receive the communication service indirectly from the node-a (320) using the node-c (340-3) and the node-d (340-4) as upper nodes or parent nodes. have.

When the structure of the communication network is changed as described above, the set E in the G=(V,E) structure is E={(a,b), (a,c), (b,c), (b,d), (c,d), (d,e), (d,f), (e,f)}. In this case, the node-e (340-5) among the node-b (340-2), the node-c (340-3), and the node-e (340-5) previously corresponding to the first layer is the third layer. may correspond to , and the node-f (340-6), which previously corresponded to the second layer, may correspond to the third layer. That is, the primary layer is composed of node-b (340-2) and node-c (340-3), the secondary layer is composed of node-d (340-4), and the third layer is node-e It may be changed to consist of (340-5) and node-f (340-6). On the other hand, b.π and c.π correspond to node-a (320), d.π corresponds to node-b (340-2) and/or node-c (340-3), and e.π and f.π may be changed to correspond to node-d (340-4). In addition, the order (descending order) of the first variable from node-a 320 corresponding to the fixed base station to each node is node-c (340-3), node-b (340-2), node-d ( 340-4), node-f (340-6), and node-e (340-5) may be changed. Each of the neighbor node lists set based on the layer hierarchy structure and the first variable for each node is, b.Adj={c, d}, c.Adj={b, d}, d.Adj={c , b, f, e}, e.Adj={d, f}, f.Adj={d, e}.

4A and 4B are exemplary diagrams for explaining an embodiment of a method of performing path selection based on a value of a first variable calculated for each communication node in a communication system.

Referring to FIG. 4A , an embodiment of a communication system may include a plurality of communication nodes. The communication system may include at least one fixed base station. Here, the fixed base station may be, for example, the same as or similar to the macro base station 320 (in other words, node-a) or the small base station 330 described with reference to FIGS. 3A to 3C . The communication system may include at least one communication node capable of functioning as a mobile backhaul base station or an access-backhaul node. Here, the mobile backhaul base station is one wireless terminal, and may refer to a wireless terminal that is connected to a fixed base station through a wireless backhaul link to provide a service to another wireless terminal. The access-backhaul node may refer to a wireless terminal capable of simultaneously configuring an access network (or an access network) and a backhaul network (or a mobile backhaul network). For example, at least one communication node capable of functioning as a mobile backhaul base station or an access-backhaul node is the second to sixth terminals 340-2, 340-3, 340-4, 340- described with reference to FIGS. 3A to 3C. 5, 340-6), in other words, node-b (340-2), node-c (340-3), node-d (340-4), node-e (340-5), node-f (340-6) and the like may be the same or similar.

Hereinafter, for convenience of description, a first communication node corresponding to one of the access-backhaul nodes selects a path between links with one fixed base station and two other access-backhaul nodes (first and second target nodes). Taking the execution situation as an example, description will be made based on an embodiment of a method for performing path selection based on the value of the first variable. However, embodiments of the present invention are not limited thereto. For example, the embodiment of the present invention may be equally or similarly applied to embodiments of various communication systems, such as a communication system in which a plurality of fixed base stations, access-backhaul nodes, and/or other communication nodes exist.

In Fig. 4a, the situation shown in Fig. 3b, that is, the node-b (340-2) detects the disconnection of the direct link (a,b) with the node-a (320), and the neighbor node list b.Adj={c,d }, it can be seen that a graph corresponding to a situation in which a path is selected by selecting one node from among node-c and/or node-d corresponding to the element of } is shown.

In an embodiment of the communication system, the first variable value for each communication node may be obtained through a calculation or measurement operation. Here, the first variable obtained for each communication node may mean a variable or a function value for evaluating each communication node and/or a communication path formed through each communication node. In the discovery state, each communication node receives a pilot signal, etc. emitted by other communication nodes in the vicinity, and may measure or obtain information of the first variable for the other communication nodes.

For example, in an embodiment of the communication system, the first variable may correspond to 'link capacity'. The link capacity obtained for each communication node may mean the link capacity in a path from the fixed base station through each node to the corresponding node. In the discovery state, each communication node receives pilot signals and the like emitted by other communication nodes in the vicinity, and can measure or obtain information on link capacity that can be established with other communication nodes. Here, the link capacity information is based on the signal-to-interference/noise ratio, the radio resources that can be allocated, the maximum possible transmission/reception data rate, the tolerance of the packet error rate serviced by the link under service, the tolerance of the user service delay, and/or the value of the link user service characteristic information. can be determined by If other conditions are the same or similar, as the number of hops between each communication node and the fixed base station (node-a) increases, the link capacity value may be obtained smaller, and as the number of hops between the fixed base stations (node-a) decreases, the link capacity value decreases. can be greatly obtained. A relatively large link capacity value can be obtained for a communication node directly connected to the fixed base station (node-a). For a communication node that is not directly connected to the fixed base station (Node-a) but is connected to the fixed base station (Node-a) through relaying of other communication nodes, link capacity information is the total data rate attenuated by relay operation and buffering. It can be calculated or defined taking into account.

Meanwhile, in another embodiment of the communication system, the 'first variable' may correspond to 'node quality' (NQ). The node quality value obtained for each communication node may mean a variable or function value defined based on the link capacity value obtained for each communication node. For example, the node quality (NQ) value may be defined to be the same as or similar to Equation 1 below.

Here, x ₀ , x ₁ , x ₂ , ... , x _n and the like may correspond to values obtained by digitizing link capacity information for each communication node. Meanwhile, C ₀ , C ₁ , C ₂ , ... , C _{n ,} etc. may correspond to predetermined weighting coefficients. That is, the node quality (NQ) value may correspond to a value obtained by adding a predetermined weighting factor to information on link capacity obtained or calculated for each communication node. If other conditions are the same or similar, as the number of hops between each communication node and the fixed base station (node-a) increases, a node quality (NQ) value may be obtained smaller, and as the number of hops between the fixed base station (node-a) decreases, the node A high quality (NQ) value may be obtained. A relatively large node quality (NQ) value may be obtained for a communication node directly connected to the fixed base station (node-a). In an embodiment of the communication system, for a communication node directly connected to the fixed base station (node-a), a node quality (NQ) value may be set to have a value greater than or equal to a predetermined reference value. Alternatively, for a communication node directly connected to the fixed base station (node-a), the node quality (NQ) value may be defined to have an infinite value. On the other hand, for a communication node that is not directly connected to the fixed base station (node-a) but is connected to the fixed base station (node-a) through relaying of other communication nodes, node quality (NQ) information is attenuated by relay operation and buffering, etc. It can be calculated or defined based on the total data rate or link capacity obtained, and the node quality (NQ) value for the upper node (the node of the upper hop).

In an embodiment of the communication system, a wireless communication environment in which each communication node connected to other communication nodes through wireless communication faces may change dynamically or dynamically. Each communication node may occasionally or continuously perform a node quality (NQ) check or update operation in order not to lose the connection to the core network through the fixed base station (node-a) even if the wireless communication environment changes. . When each communication node checks node quality (NQ) information for other communication nodes and establishes a connection path to a fixed base station (node-a), node quality (NQ) predicted in advance for a predetermined service time interval The predicted values can be calculated and used. For example, when each communication node is predicted to have an excessively lowered node quality (NQ) value for a specific communication node in a predetermined service time interval compared to the current time, the connection path through another communication node in the corresponding service time interval can operate to set Each communication node compares the node quality (NQ) predicted value predicted in advance for a predetermined service time interval with the node quality (NQ) value confirmed while actually performing communication in the corresponding time interval, thereby improving the accuracy of the prediction operation. can Each communication node compares the node quality (NQ) predicted value predicted in advance for a predetermined service time interval and the node quality (NQ) value confirmed while actually performing communication in the corresponding time interval, C ₀ , C ₁ , C ₂ , ... , C _{n ,} etc., may be calculated, adjusted, or updated. In an embodiment of the communication system, weight coefficients may be calculated, adjusted, or updated based on a regression method such as a linear regression method. For example, in an embodiment of the communication system, weight coefficient values may be calculated based on equations such as Equations 2 and 3, and the like.

와 노드 품질(NQ)의 예측값

간의 오차 함수에 기초하여 비용 함수를 정의하고, 수학식 3에서와 같이 비용 함수의 그래디언트가 0이 되도록 하는 계수 값들을 구하거나 계산할 수 있다. 수학식 3의 해들은

등과 같이 표현될 수 있다. 각 통신 노드들은 수학식 2 및/또는 수학식 3을 통해 획득된 값 또는 정보들에 기초하여, 수학식 1에 따른 노드 품질(NQ) 정보 및/또는 수학식 1의 가중치 계수 정보 등을 순시적으로 조정할 수 있다. 이를테면, 각 통신 노드들은 수학식 1에 따른 노드 품질(NQ) 정보 및/또는 수학식 1의 가중치 계수 정보 등이, 수학식 2 및/또는 수학식 3을 통해 획득된 값 또는 정보들에 근접한 값을 가지도록 순시적으로 조정할 수 있다. 그러나 이는 설명의 편의를 위한 하나의 예시일 뿐이며, 본 발명의 실시예는 이에 국한되지 않는다. 이를테면, 통신 시스템의 다른 실시예에서는 가중치 계수들이 선형 회귀 방식 외에도 다항성 회귀 방식, 로지스틱 회귀 방식 등 다양한 회귀 방식 중 어느 하나에 기초하여 계산, 조정 또는 갱신될 수 있다.In one embodiment of the communication system, the node quality (NQ) value as in Equation 2

and predicted values of node quality (NQ)

A cost function may be defined based on an error function between the two values, and coefficient values such that the gradient of the cost function becomes 0 may be obtained or calculated as shown in Equation (3). The solutions of Equation 3 are

It can be expressed as Each communication node instantaneously receives node quality (NQ) information according to Equation 1 and/or weight coefficient information of Equation 1 based on the value or information obtained through Equation 2 and/or Equation 3 can be adjusted with For example, each communication node has node quality (NQ) information according to Equation 1 and/or weight coefficient information of Equation 1, and a value close to a value or information obtained through Equation 2 and/or Equation 3 can be adjusted instantaneously to have However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto. For example, in another embodiment of the communication system, weight coefficients may be calculated, adjusted, or updated based on any one of various regression methods such as a polynomial regression method and a logistic regression method in addition to a linear regression method.

In one embodiment of the communication system, each of at least one communication node capable of functioning as an access-backhaul node may operate based on at least one communication status or system status. For example, each of at least one communication node corresponding to an access-backhaul node may include some or all of a discovery state (or discovery mode), a call state (or a call mode), and a backhaul connection state (or a backhaul connection mode). .

In the discovery state (or discovery mode), each of at least one communication node capable of functioning as an access-backhaul node receives or monitors a pilot signal or the like transmitted by neighboring communication nodes, thereby providing a first variable for each communication node. A value of , and/or a value of a first variable for each communication path formed through each communication node may be measured or obtained. Through the discovery procedure performed in each communication node, the layer hierarchy expressed as G = (V, E), the first variable information for each communication node, the upper node for each communication node information, and/or neighbor node list information, etc. may be determined or confirmed.

In a call state (or call mode), each of at least one communication node may receive a communication service directly or indirectly from a fixed base station through a communication path determined through a search state or the like. A communication node in a call state may not easily perform relay or communication service provision to other communication nodes even though it has a function as an access-backhaul node. A communication node in a call state may be restricted not to perform relay or communication service provision to other communication nodes.

A communication node in the backhaul connection state (or backhaul connection mode) provides communication services to the communication node that has made a relay role request or communication service provision request among its child nodes by being connected to its parent node and its child node. can do. The communication node in the backhaul connection state may deliver the communication service delivered from the upper node to the lower node. Alternatively, the communication node in the backhaul connection state may transmit the uplink signal transmitted from the lower node to the upper node.

Specifically, the first communication node (node-b) has a communication path with the fixed base station (node-a) in the search state, or communication nodes (node-c, node) adjacent to itself from the fixed base station (node-a). It is possible to check the first variable for each communication path connected to itself through -d). For example, the first communication node (node-b) has a communication path (ie, path ab) through the fixed base station (node-a) that forms a direct link, and a communication path from the fixed base station (node-a) through node-c (ie, path acb), and a communication path (ie, path adb) through node-d, which is another adjacent communication node, may check the value of the first variable. The first communication node (node-b) has a fixed base station (node-a) through a communication path set or selected based on the first variable value identified for each of the nodes (node-a, node-b, node-c). ) can provide communication services. On the other hand, the first communication node (node-b) determines that the communication path is disconnected when the value of the first variable checked for the communication path currently receiving the communication service is changed to less than a predetermined threshold value can be searched for. Alternatively, the first communication node (node-b) is the communication path based on a predetermined criterion when the value of the first variable checked for the communication path currently receiving the communication service is changed to be less than a predetermined threshold value. can be determined whether to substitute another communication path. Here, the predetermined criterion may include, for example, a predetermined time reference, a change trend of the value of the first variable, a change pattern in the past, and the like. The first communication node (node-b) may determine whether to replace the communication path with another communication path by determining or predicting how long the disconnection of the communication path will last based on a predetermined criterion.

For example, in the initial condition, the first communication node (node-b) determines that the value of the first variable checked for the fixed base station (node-a) is the best, so that the direct link (a) with the fixed base station (node-a) ,b) can provide communication services. However, when a change in the communication environment, such as movement of a communication obstacle, occurs, the value of the first variable for each node may be changed. For example, when the link (a, b) between the first communication node (node-b) and the fixed base station (node-a) is disturbed or does not satisfy the LOS condition due to the movement of a specific communication obstacle, the first communication node ( The value of the first variable identified for the fixed base station (node-a) in node-b) may be decreased. If the value of the first variable identified for the fixed base station (Node-a) or the value of the first variable identified for the communication path (ie, hereinafter, the first path) through the fixed base station (Node-a) is the first threshold When the value is decreased to less than the value, the first communication node (node-b) may determine that it is not easy to receive the communication service through the direct link (a,b) with the fixed base station (node-a). Alternatively, the first communication node (node-b) may determine that the first path through direct connection with the fixed base station (node-a) is disconnected. The first communication node (node-b) may perform a search for another path when it is determined that the first path through which the communication service is currently provided is disconnected. Alternatively, when the first communication node (node-b) determines that the first path through which the communication service is currently provided is disconnected, a predetermined criterion and/or for determining or predicting how long the disconnection of the first path will last. Based on it, it may be determined whether to replace the first path with another communication path. For example, when it is determined or predicted that the first path will be restored within the first preset time interval, the first communication node (node-b) may wait for restoration of the first path without searching for another communication path. On the other hand, when it is determined or predicted that the first path will not be restored within the first time interval, or if the first path is not restored even after the first time interval has elapsed after the first path is disconnected, for searching for another communication path action can be performed. In other words, if it is determined, predicted or confirmed that the first path will not be restored within the first time interval, the first communication node (node-b) may transition from the call state to the search state and perform a search operation.

For example, the first variable for the first path increases above the first threshold value over time after it is determined that the first path is disconnected because the value of the first variable for the first path decreases below the first threshold value If so, the first communication node (node-b) may determine that the first path is restored. When it is confirmed that the first path determined to be temporarily disconnected is restored, the first communication node (node-b) may receive a communication service through the restored first path. On the other hand, after the first variable for the first path decreases below the first threshold value, it is determined that the first variable will not increase above the first threshold value within the first time interval, or the first time interval actually elapses. When the first variable does not increase beyond the first threshold value, the first communication node (node-b) may search for another communication path.

The first communication node (node-b) may check its neighbor node list in order to search for another communication path. For example, the first communication node (node-b) may set each of the communication nodes corresponding to an element of its neighbor node list as a target node, and check a first variable value for each target node. Alternatively, the first communication node (node-b) may check a preset order among elements in its neighbor node list in order to search for another communication path.

For example, the first communication node (node-b) has a first target node (node-c) and a second target node (node-c) corresponding to elements of b.Adj={c, d}, which is its neighbor node list. d) You can check the value of the first variable for each. As shown in the graph of FIG. 4A , when it is confirmed that the first variable value for the first target node (node-c) is superior to the first variable value for the second target node (node-d), the first communication The node (node-b) may select the first target node (node-c). Alternatively, the first communication node (node-b) is the first communication node (node-b) in its neighbor node list, b.Adj={c, d}, based on a preset order based on the value of the first variable, the first communication node corresponding to the priority element c 1 A target node (node-c) can be selected. The first communication node (node-b) transmits a relay request signal to the selected first target node (node-c) to select a communication path through the first target node (node-c) to receive a communication service procedure can be performed.

On the other hand, if it is confirmed that the status of the communication node selected to perform the relay role for the first communication node (node-b) is in the call state, the first communication node (node-b) is selected It may operate to reselect a communication node other than the communication node. For example, if the state of the first target node (node-c) selected by the first communication node (node-b) to perform a relay role for itself is in a call state or a call mode, the first target node (node- c) may not be easy to perform a relay role for the first communication node (node-b). In this case, the first communication node (node-b) may request the second target node (node-d) corresponding to the next priority among the target nodes to perform the relay role.

Referring to FIG. 4B , in an embodiment of the communication system, the first communication node (node-b) may perform path selection through operations such as measuring and updating a value of a first variable with respect to other communication nodes. For example, in an initial condition according to an embodiment of the communication system, the first communication node (node-b) may be directly connected to the fixed base station (node-a). In this case, the upper node of the first communication node (node-b) may be expressed as "b.π=a". Meanwhile, in an embodiment of the communication system, the first communication node (node-b) is connected to the first target node (node-c) and the second target node (node-d), and the first target node (node- A first variable value (eg, a node quality (NQ) value) for c) may be obtained as a value greater than the first variable value for the second target node (node-d). In this case, the list of adjacent nodes of the first communication node (node-b) may be expressed as “b.Adj={c,d}”.

If, due to a change in the wireless communication environment, the value of the first variable confirmed by the specific communication node with respect to the upper node and/or the value of the first variable confirmed by the upper node with respect to the communication path decreases below the first threshold value, the corresponding The communication node may use the highest priority node in the neighbor node list as its parent node instead of the existing upper node. For example, the first communication node (node-b) determines the first variable value for the communication path through the fixed base station (node-a) or the fixed base station (node-a), which is an upper node, to decrease below the first threshold value. In this case, the first target node (node-c) having the highest priority in b.Adj={c,d} may become a higher node of the first communication node (node-b). In this case, the upper node and the neighbor node list of the first communication node (node-b) may be expressed as "b.π=c" and "b.Adj={d}", respectively.

Meanwhile, in the initial condition, it was confirmed that the first variable value for the first target node (node-c) was greater than the first variable value for the second target node (node-d), but due to the change in the wireless communication environment, the second It may be confirmed that the first variable value for the target node (node-d) is greater than the first variable value for the first target node (node-c). In this case, the list of adjacent nodes of the first communication node (node-b) may be updated as b.Adj={d,c}.

If the first variable value confirmed for the fixed base station (node-a), which is the upper node, by the first communication node (node-b) due to a change in the wireless communication environment in the initial condition, decreases below the first threshold value, and the second target When it is determined that the first variable value for the node (node-d) is greater than the first variable value for the first target node (node-c), the upper node of the first communication node (node-b) is the second It may be changed to a target node (node-d). In this case, in this case, the upper node and the neighbor node list of the first communication node (node-b) may be expressed as "b.π=d" and "b.Adj={c}", respectively.

Each communication node may occasionally or continuously calculate or monitor the value of the first variable for connected or adjacent communication nodes, or other communication nodes sensed on the communication system. According to a change in the wireless communication environment and changes in the values of the first variable that are checked accordingly, a connection relationship such as an upper node and/or a list of adjacent nodes of each communication node may also change. For example, in an embodiment of the communication system, the connection relationship of the upper node and the neighbor node list of the first communication node (node-b) is changed from any one of the states shown in FIG. 4B to another according to a change in the wireless communication environment. can change dynamically. Alternatively, the upper node and the neighbor node list of the first communication node (node-b) may dynamically change from one of the states shown in FIG. 4B to another according to a change in the wireless communication environment. The connection relationship such as the upper node and the neighbor node list of the first communication node (node-b) is in other states not shown in FIG. 4B according to the change of the wireless communication environment (for example, the upper node is b.π=c or b .π = d and the list of adjacent nodes can be dynamically changed even in the empty set state, etc.).

5 is an exemplary diagram for explaining a first embodiment of a method for a first communication node to select a communication path in a communication system.

Referring to FIG. 5 , the first communication node 510 of the communication system 500 is connected to one or more communication nodes 520-1, ..., 520-n and/or the first base station 530 for each. , a first variable corresponding to a variable or function calculated or obtained in order to evaluate a communication path formed through each communication node, etc. (including a base station) and/or each communication node, etc. may be identified. Here, the first variable for each communication node may correspond to, for example, link capacity or node quality (NQ) described with reference to FIGS. 4A and 4B . The first communication node 510 is a first base station based on a first variable identified for each of the connected one or more communication nodes 520-1, ..., 520-n and/or the first base station 530 A communication path through which a communication service will be provided may be selected from 530 . Here, the communication system 500 may be configured the same as or similar to the communication system 300 described with reference to FIGS. 3A to 3C and/or the communication system described with reference to FIGS. 4A and 4B . Each of the first communication node 510 and the connected one or more communication nodes 520-1, ..., 520-n may function as a mobile backhaul base station or an access-backhaul node. Here, the mobile backhaul base station is one communication node, and may refer to a communication node that is connected to a fixed base station through a wireless backhaul link to provide a service to another communication node. The access-backhaul node may refer to a communication node capable of simultaneously configuring an access network (or an access network) and a backhaul network (or a mobile backhaul network). The first communication node 510 and the connected one or more communication nodes 520-1, ..., , 520-n, respectively, are the second to sixth terminals 340-2, .. described with reference to FIGS. 3A to 3C. , 340-6), and/or the same as the first communication node (node-b), the first target node (node-c), the second target node (node-d), etc. described with reference to FIGS. 4A and 4B, or It can be configured similarly. The first base station 530 may be configured the same as or similar to the macro base station 320 described with reference to FIGS. 3A to 3C and/or the fixed base station (Node-a) described with reference to FIGS. 4A and 4B . Each of the communication nodes 510 , 520-1 , ... , 520-n, 530 constituting the communication system 500 may be configured the same as or similar to the communication node 200 described with reference to FIG. 2 . .

The first communication node 510 may be connected to the first base station 530 to receive a communication service (S540). Here, the first communication node 510 may be directly connected to the first base station 530 through a direct link between the first communication node 510 and the first base station 530 . Alternatively, the first communication node 510 may be indirectly connected to the first base station 530 through a relay of other communication nodes constituting the communication system 500 . The first communication node 510 may receive a communication service directly or indirectly from the directly or indirectly connected first base station 530 . The first communication node 510 may receive a communication service from the first base station 530 through the first communication path (S540).

In a situation such as a decrease in the first variable for the first communication path due to a communication situation or a change in the communication environment, the first communication node 510 may determine that the first communication path is disconnected (S545) . The first communication path may be temporarily or eventually disconnected in some or all of a link directly connected to the first communication node 510 and/or a link connected indirectly to the first communication node 510 . Here, the first communication node 510 may determine whether the first communication path is disconnected in the same or similar manner as described with reference to FIGS. 4A and 4B . Upon detecting the disconnection of the first communication path, the first communication node 510 may determine whether to search for another communication path to replace the first communication path. Here, the first communication node 510 may determine whether to search for another communication path in the same or similar manner as described with reference to FIGS. 4A and 4B .

The first communication node 510 may search for another communication path to replace the first communication path. The first communication node 510 may perform a search for another communication path in the same or similar manner as described with reference to FIGS. 4A and 4B . For example, the first communication node 510 may check a first variable for each of at least one communication node connected thereto in order to search for another communication path to replace the first communication path ( S550 ). Here, at least one communication node connected to the first communication node 510 may be referred to as a 'target node'. An embodiment of the communication system 500 may include first to n-th target nodes 520-1, ..., 520-n connected to the first communication node 510 . The first communication node 510 may check the elements of its neighbor node list in order to search for another communication path to replace the first communication path. The first communication node 510 may check the first variable for each element of its neighbor node list. Alternatively, the first communication node 510 may check the order of elements set based on the first variable for each element in its neighbor node list. The first communication node 510 may select one target node based on an order of each of the identified elements or a first variable of each of the identified elements. The first communication node 510 may select a target node corresponding to the highest priority element among at least one target node 520-1, ..., 520-n corresponding to the elements of its neighbor node list. . Alternatively, the first communication node 510 has the largest value of the first variable identified among at least one target node 520-1, ..., 520-n corresponding to the elements of its neighbor node list. You can select a node. For example, the first communication node 510 selects the first target node 520-1 from among at least one target node 520-1, ..., 520-n corresponding to the elements of its neighbor node list. You can choose. Here, in FIG. 5 , an embodiment in which the first target node 520-1 selected by the first communication node 510 corresponds to a primary layer directly connected to the first base station 530 can be viewed as an example. However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

The first communication node 510 may transmit a relay request signal to the first target node 520-1 (S555). The relay request signal may be referred to as a 'Relay Request' signal. The first target node 520-1 may receive a relay request signal from the first communication node 510 (S555). The first target node 520-1 corresponding to the primary layer may transmit a relay role permission request signal to the first base station 530 based on the relay request signal received from the first communication node 510. (S560). The relay role permission request signal may be referred to as a 'Relay Role Request' signal.

The first base station 530 may receive a relay role permission request signal from the first target node 520-1 (S560). The first base station 530 performs a relay role for the first communication node 510 by the first target node 520-1 based on a relay role permission request signal received from the first target node 520-1. You can decide whether to allow it or not. When the first target node 520-1 decides to allow the first communication node 510 to perform a relay role, the first base station 530 acts as a relay to the first target node 520-1. A permission signal may be transmitted (S570). The relay role grant signal may be referred to as a 'Relay Role Grant' signal. The first target node 520-1 may receive a relay role permission signal from the first base station 530 (S570). The first target node 520-1 may transmit a relay permission signal to the first communication node 510 based on the received relay role permission signal (S580). The relay grant signal may be referred to as a 'Relay Grant' signal. The first communication node 510 may receive a relay permission signal from the first target node 520-1.

When the first communication node 510 receives the relay permission signal from the first target node 520-1, the first communication node 510 transmits the first communication node 510 through the relay or relay of the first target node 520-1. It can be seen that the base station 530 is indirectly connected. In other words, the first communication node 510 may be viewed as being connected to the first base station 530 through a new communication path (hereinafter, referred to as a second communication path) differentiated from the first communication path (S585). As the communication path through which the first communication node 510 is connected to the first base station 530 is changed, the first variable between the first base station 530 and the first communication node 510 may be changed. The first communication node 510 may notify communication nodes connected thereto of the change of the communication path and/or the change of the first variable ( S590 ). The first communication node 510 may instruct or request an update of the neighbor node list from communication nodes connected thereto (S590). Based on an instruction or request from the first communication node 510 , the configuration and/or order of elements of the neighbor node list of each communication node connected to the first communication node 510 may be changed. Through some or all of the operations described through steps S545 to S590, the operation of the first communication node 510 selecting and setting another communication path to replace the first communication path may be completed. The first communication node 510 is indirectly connected to the first base station 530 through a second communication path established through the first target node 520-1 serving as a relay, and thus the first base station 530 A communication service may be provided indirectly from the user (S595).

6 is an exemplary diagram for explaining a second embodiment of a method for a first communication node to select a communication path in a communication system.

Referring to FIG. 6 , the first communication node 610 of the communication system 600 is connected to one or more communication nodes and/or for each of the first base station 630 , each communication node, etc. (including the first base station) and/or Alternatively, a first variable corresponding to a variable or function calculated or obtained in order to evaluate a communication path formed through each communication node or the like may be identified. Here, the first variable for each communication node may correspond to, for example, link capacity or node quality (NQ) described with reference to FIGS. 4A and 4B . The first communication node 610 selects a communication path through which a communication service is to be provided from the first base station 630 based on a first variable identified for each of the connected one or more communication nodes and/or the first base station 630 . can The communication system 600 includes a first relay node 620-1 directly connected to the first communication node 610, and a second relay node 620-2 corresponding to an upper node of the first relay node 620-1. ) may be included. The communication system 600 may further include communication nodes (not shown) directly connected to the first communication node 610 in addition to the first relay node 620 - 1 . In other words, the communication system 600 may include first to n-th target nodes corresponding to elements of the neighbor node list of the first communication node 610 . The communication system 600 may be the same as or similar to the communication system 300 described with reference to FIGS. 3A to 3C , the communication system described with reference to FIGS. 4A and 4B , and/or the communication system 500 described with reference to FIG. 5 . can be configured. The first communication node 610, the first and second relay nodes 620-1 and 620-2, and other communication nodes (not shown) connected to the first communication node 610 are each shown in FIGS. 3A to 3C. The second to sixth terminals 340-2, ..., 340-6 described with reference to, the first communication node (node-b) described with reference to FIGS. 4A and 4B, and the first target node (node-c) ), the second target node (node-d), and/or the same as the first communication node 510 and one or more connected communication nodes 520-1, ..., , 520-n described with reference to FIG. 5, etc. or similarly configured. The first base station 630 is a macro base station 320 described with reference to FIGS. 3A to 3C, a fixed base station (Node-a) described with reference to FIGS. 4A and 4B, and/or a first base station described with reference to FIG. 5 ( 530) and may be configured in the same or similar manner. Each of the communication nodes 610, 620-1, ..., 620-n, 630 constituting the communication system 600 may be configured the same as or similar to the communication node 200 described with reference to FIG. 2 . . Hereinafter, in describing a second embodiment of a method in which the first communication node selects a communication path with reference to FIG. 6 , content overlapping with that described with reference to FIG. 5 may be omitted.

The first communication node 610 may be connected to the first base station 630 to receive a communication service directly or indirectly (S640). The first communication node 610 may receive a communication service from the first base station 630 through the first communication path (S640). In a situation such as a decrease in the first variable for the first communication path due to a communication situation or a change in the communication environment, the first communication node 610 may determine that the first communication path is disconnected (S645) . Upon detecting the disconnection of the first communication path, the first communication node 610 may determine whether to search for another communication path to replace the first communication path.

The first communication node 610 may search for another communication path to replace the first communication path. For example, the first communication node 610 may check a first variable for each of at least one communication node connected thereto in order to search for another communication path to replace the first communication path ( S650 ). The first communication node 610 searches for another communication path to replace the first communication path, and/or the first variable and/or the first to nth target nodes corresponding to elements of its neighboring node list. You can check the order of each element in the adjacent node list. The first communication node 610 may select one target node based on an order of each of the identified elements or a first variable for each of the first to nth target nodes corresponding to each of the identified elements. A target node selected by the first communication node 610 to select a communication path may be referred to as a 'first relay node' 620-1. Here, FIG. 6 shows an embodiment in which the first relay node 620-1 selected by the first communication node 610 corresponds to a secondary layer or a tertiary or higher layer indirectly connected to the first base station 630 as an example. can be seen to have been However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

The first communication node 610 may transmit a relay request signal to the first relay node 620-1 (S655). The first relay node 620-1 sends a relay role permission request signal to the second relay node 620-2 corresponding to its upper node based on the relay request signal received from the first communication node 610. can be transmitted (S660). Only one relay node (ie, the second relay node 620-2) may exist between the first relay node 620-1 and the first base station 630, or a plurality of relay nodes may exist. When only one relay node (ie, the second relay node 620-2) exists between the first relay node 620-1 and the first base station 630, the second relay node 620-2 is the second relay node 620-2. Based on the relay role permission request signal received from the first relay node 620-1, a relay role permission request signal may be transmitted to the first base station 630 (S665). On the other hand, when a plurality of relay nodes exist between the first relay node 620-1 and the first base station 630, the second relay node 620-2 is another relay node (not shown) that is its upper node. ) to transmit a relay role permission request signal. The relay permission request signal transmitted from the first and second relay nodes 620 - 1 and 620 - 2 may be directly or indirectly transmitted to the first base station 630 .

The first base station 630 is based on the relay permission request signal transmitted directly or indirectly from the first and second relay nodes 620-1 and 620-2, and the first and second relay nodes 620-1 and 620-2. It may be determined whether or not to allow the 620-2 to perform a relay role for the first communication node 610 . When it is decided to allow the first and second relay nodes 620-1 and 620-2 to perform a relay role for the first communication node 610, the first base station 630 is the second relay node ( 620-2) or a higher relay node (not shown) may transmit a relay role permission signal (S670). The second relay node 620 - 2 may transmit a relay role permission signal to the first relay node 620 - 1 based on the relay role permission signal transmitted directly or indirectly from the first base station 630 . (S675). The first relay node 620-1 may transmit a relay permission signal to the first communication node 610 based on the relay role permission signal received from the second relay node 620-2 (S680).

When the first communication node 610 receives the relay permission signal from the first relay node 620-1, the first communication node 610 connects the first and second relay nodes 620-1 and 620-2. It can be seen as indirectly connected to the first base station 630 through a relay or relay. In other words, it can be seen that the first communication node 610 is connected to the first base station 630 through a new communication path (hereinafter, referred to as a second communication path) that is differentiated from the first communication path (S685). As the communication path through which the first communication node 610 is connected to the first base station 630 is changed, the first variable between the first base station 630 and the first communication node 610 may be changed. The first communication node 610 may notify the communication nodes connected thereto of the change of the communication path and/or the change of the first variable, or may instruct or request the update of the neighbor node list (S690). Based on an instruction or request from the first communication node 610, the configuration and/or order of elements of the adjacent node list of each communication node connected to the first communication node 610 may be changed (S690) . Through some or all of the operations described through steps S645 to S690, the operation of the first communication node 610 selecting and setting another communication path to replace the first communication path may be completed. The first communication node 610 is indirectly connected to the first base station 630 through the second communication path set through the first and second relay nodes 620-1 and 620-2 serving as a relay. , a communication service may be indirectly provided from the first base station 630 (S695).

According to an embodiment of the present invention, in a wireless communication system to which a mobile backhaul network is applied, a communication situation or environment such as movement of communication nodes capable of performing the role of an access-backhaul node or a mobile backhaul base station or movement of a communication obstacle A path selection method and apparatus capable of quickly and efficiently setting a communication path according to the change of A communication node (hereinafter, referred to as a first communication node) that has been provided with a communication service through a predetermined communication path from a fixed base station may check a list of communication nodes connected thereto when disconnection of the communication path is detected. The first communication node may select a communication path by selecting one communication node based on a first variable value checked for communication nodes connected thereto. Thereby, selection of a new communication path for replacing the disconnected communication path can be performed quickly and efficiently.

However, effects that can be achieved by the path selection and the apparatus in the wireless communication system in the wireless communication system according to the embodiments of the present invention are not limited to those mentioned above, and other effects that are not mentioned are described in the present application. It will be clearly understood by those skilled in the art from the configurations described in the specification of the present invention.

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 in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software.

Examples of computer-readable media include hardware devices specially configured to store and carry out program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as at least one software module to perform the operations of the present invention, and vice versa.

Although it has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. will be able

Claims (1)

A method for path selection performed by a first communication node of a communication system, the method comprising:
detecting, by the first communication node, disconnection of a first communication path through which a communication service is provided from a first base station of the communication system;
identifying at least one communication node connected to the first communication node;
calculating, for each of the identified at least one communication node, a first variable for each communication path connected from the first base station through the at least one communication node to the first communication node;
selecting one target node by comparing each of the at least one communication node based on the calculated first variable; and
and replacing the first communication path through a second communication path formed via the selected target node.

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