KR20220040988A - Method and appratus for changing beam in communication system - Google Patents

Abstract

A beam changing method technique in a communication system is disclosed. An operating method of a terminal of the communication system comprises the following steps of: forming a virtual beam group including a first beam of a first type and a second beam of a second type, transmitted by a base station, and a plurality of beams of the first type, transmitted by relay nodes; transmitting and receiving data to and from the base station by using the first beam of the first type transmitted by the base station; and selecting a different beam in the virtual beam group to use the selected beam so as to transmit and receive the data to and from the base station when receiving signal strength of the first beam is less than a first threshold value.

Description

Method and apparatus for changing a beam in a communication system

The present invention relates to a beam changing technology in a communication system, and more particularly, to a beam changing technology in a communication system that allows a mobile terminal to maintain communication by changing a beam when communication with a base station is interrupted by an obstacle it's about

4G (4th Generation) communication system (e.g., LTE (Long Term Evolution) communication system, LTE-A (Advanced) communication system) for the processing of rapidly increasing wireless data after the commercialization of the frequency band of the 4G communication system ( For example, a 5th generation (5G) communication system (eg, NR (New Radio) communication system) is being considered. The 5G communication system may support enhanced Mobile BroadBand (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and Massive Machine Type Communication (mMTC).

On the other hand, in a mobile communication environment using a millimeter wave band, a mobile device (or subscriber terminal) has a line-of-sight (LoS) It may disappear and cause communication problems. Disruptions can be exacerbated for seconds by large road signs, heavy trucks, and lush trees. In particular, when a mobile device and a base station have to deal with such a disturbance in a short time, processing delay and signaling load may become a great burden on a communication system. To this end, 3GPP may have proposed integrated access backhaul (IAB), side-link, relay node, multi-connections, and the like in relation to LTE and 5G mobile communication. However, in a communication environment in which the received signal strength of the signal being served by the base station rapidly decreases, it may not be easy for the mobile body and the base station to measure the signal of the adjacent base station or to quickly process the signaling overhead procedure using the existing technology. However, it may not be easy to effectively satisfy the performance indicators required by the industry.

An object of the present invention for solving the above problems is to provide a beam changing method and apparatus in a communication system that allows a moving terminal to maintain communication by changing the beam when communication difficulties occur due to obstructions is doing

In order to achieve the above object, a method for changing a beam in a communication system according to a first embodiment of the present invention is a method of operating a terminal of the communication system, wherein a first type of a first beam and a second type of a beam transmitted by a base station are transmitted. forming a virtual beam group including a plurality of beams of the first type transmitted by beams and relay nodes; transmitting and receiving data to and from the base station using the first beam of the first type transmitted by the base station; and when the received signal strength of the first beam becomes less than the first threshold due to the movement of the terminal, the beam shape is changed to the second type of second beam to transmit/receive data to and from the base station or in the virtual beam group selecting another beam of a first type and changing it to a selected beam, and transmitting/receiving data to and from the base station using the selected beam, wherein the first type may be a narrow beam and the second type may be a wide beam .

When a mobile object encounters an obstacle that interferes with communication when using a plurality of beams with a narrow beam width and a communication loss situation occurs, beam switching can be performed immediately to a default beam with a wide beam width.

In addition, since the mobile unit can immediately switch to the default beam with a wide beam width in a communication interruption situation, it is possible to improve the millimeter wave communication disconnection time due to damage to the visible path.

In addition, since the mobile device can minimize procedures such as beam sweeping, measurement and reporting when switching beams by using the default beam, radio resources and control signal overhead required when changing a beam can be reduced.

1 is a conceptual diagram illustrating a first embodiment of a communication system.
2 is a conceptual diagram illustrating a first embodiment of virtual beam groups according to a location of a terminal.
3 is a conceptual diagram illustrating a first embodiment of beams transmitted by a distribution unit of a base station.
4 is a conceptual diagram illustrating a first embodiment of a method for changing a beam in a communication system.
5A and 5B are flowcharts illustrating a first embodiment of a method for changing a beam in a communication system.
6 is a flowchart illustrating a first embodiment of a method for changing a beam in a communication system.
7 is a conceptual diagram illustrating a second embodiment of a method for changing a beam in a communication system.
8 is a flowchart illustrating a second embodiment of a method for changing a beam in a communication system.
9 is a conceptual diagram illustrating a first embodiment of a process in which a terminal performs beam switching from a narrow beam to a default beam.
10 is a block diagram illustrating a first embodiment of a communication node constituting 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 an element is referred to as being “connected” or “connected” to another element, it is understood that it may be directly connected or connected to the other element, but other elements may exist in between. it should be On the other hand, when it is said 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

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 a first 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). Here, the communication system may be referred to as a “communication network”. Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may include a code division multiple access (CDMA)-based communication protocol, a wideband CDMA (WCDMA)-based communication protocol, a time division multiple access (TDMA)-based communication protocol, and a frequency division multiple (FDMA)-based communication protocol. access) based communication protocol, OFDM (orthogonal frequency division multiplexing) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (non-orthogonal multiple) access)-based communication protocol, space division multiple access (SDMA)-based communication protocol, etc. may be supported.

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 and 130- 2, 130-3, 130-4, 130-5, 130-6). 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 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 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 within the coverage of the third base station 110-3. . The first terminal 130-1 may belong to the coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the 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), A radio base station, a radio transceiver, an access point, an access node, a road side unit (RSU), a digital unit (DU), a cloud digital unit (CDU) , a radio remote head (RRH), a radio unit (RU), a transmission point (TP), a transmission and reception point (TRP), a relay node, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 is an access terminal, a mobile terminal, a station, It may be referred to as a subscriber station, a mobile station, a portable subscriber station, user equipment (UE), a node, a device, and the like.

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) Each may support cellular (cellular) communication (eg, long term evolution (LTE), LTE-A (advanced), etc. defined in the 3rd generation partnership project (3GPP) standard). 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 or a non-ideal backhaul, and the ideal backhaul Alternatively, information may be exchanged with each other through a non-ideal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) through an ideal backhaul or a non-ideal backhaul. 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 a 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

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may support OFDMA-based downlink (DL) transmission, and SC-FDMA-based uplink (uplink, UL) transmission may be supported. In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits multiple input multiple output (MIMO) (eg, single user (SU)-MIMO, MU (multi user)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation transmission, transmission in an unlicensed band, device to device, D2D ) communication (or Proximity services (ProSe), etc.), etc. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 is a base station. (110-1, 110-2, 110-3, 120-1, 120-2) and corresponding operation, by the base station (110-1, 110-2, 110-3, 120-1, 120-2) Supported actions can 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. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes the terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) and a signal may be transmitted/received based on the CA method. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 coordinates D2D communication between the fourth terminal 130-4 and the fifth terminal 130-5. (coordination), each of the fourth terminal 130-4 and the fifth terminal 130-5 is D2D communication by the coordination of each of the second base station 110-2 and the third base station 110-3 can be performed.

On the other hand, a terminal (mobile object) moving in a mobile communication environment using a millimeter wave band may experience inconvenience in communication because a visible path may be lost due to a short-term or long-term obstruction. Disruptions can be exacerbated for seconds by large road signs, heavy trucks, and lush trees. In particular, when the terminal and the base station have to deal with such an interference phenomenon in a short time, processing delay and signaling load may become a great burden on the communication system. In order to solve this problem, when a mobile terminal encounters an obstacle and the received signal strength of a narrow-beam (NB), which is a serving beam transmitted from a base station, falls below a threshold, the terminal is a virtual beam that is a group of predefined candidate beams. A wide-beam (WB) (hereinafter, referred to as a default beam) selected by default in a virtual beam group (VBG) can be immediately used as a serving beam. That is, the terminal can use a general beam as needed. The switching procedure can be omitted and communication can be maintained by performing beam switching of changing the serving beam to the default beam in a hardware manner, where the frequency of the default beam may be the same as or different from the previously serving beam, the narrow beam. The narrow beam may use a millimeter wave band, and the wide beam may use a specific millimeter wave band or a specific cellular band (for example, a shared band of 6 GHz or less), where the virtual beam group can be used directly by the terminal. It may be a set of candidate beams, and may be composed of narrow beams and wide beams.

2 is a conceptual diagram illustrating a first embodiment of virtual beam groups according to a location of a terminal.

Referring to FIG. 2 , in the virtual beam groups according to the location of the terminal, the virtual beam group 1 is located in the communication service area of the distribution unit (DU) 220 of one base station at the time t1 of the terminal 210 . In this case, it may be composed of at least one narrow beam 240-1. On the other hand, while the terminal 210 is moving in the distribution unit 220 of the base station at time t2, two moving relay nodes 230-1 and 230-2 communicate with the distribution unit 220 of the base station. A relay may be provided to the terminal 210 by entering the service area. In this case, the distribution unit 220 of the base station and the second mobile relay node 230 - 2 may exchange data through the narrow beam 230 - 4 transmitted by the distribution unit 220 of the base station. In this case, the virtual beam group 2 includes at least one narrow beam 240-1 transmitted by the distribution unit 220 of the base station and at least one narrow beam 240 transmitted by the first mobile relay node 230-1. -2) and at least one narrow beam 240-3 transmitted by the second mobile relay node 230-2. On the other hand, while the terminal 210 is moving in the communication service area of the distribution unit 220 of the base station at time t3, the first mobile relay node 230-1 may deviate from the communication service area of the distribution unit 220 of the base station. Accordingly, the first mobile relay node 230-1 cannot provide the relay to the terminal 210. In this case, the virtual beam group 3 may be composed of a wide beam 250 transmitted by the distribution unit 220 of the base station and a narrow beam 230-2 transmitted by the second mobile relay node 230-2. . In this case, the distribution unit 220 of the base station may not use the narrow beam 240 - 1 and may provide a communication service to the terminal 210 using the wide beam 250 .

Meanwhile, the distribution unit 220 of the base station may transmit a plurality of narrow beams and broad beams toward the terminal 210 by performing beam sweeping, and the plurality of narrow beams and broad beams from the terminal 210 may be Virtual beam groups may be generated by receiving beam measurement results. In addition, the distribution unit 220 of the base station may inform the terminal 210 of information on the generated virtual beam groups through network signaling (eg, radio resource control (RRC) signaling). At this time, the distribution unit 220 of the base station controls the mobile relay nodes 230-1 and 230-2 so that the mobile relay nodes 230-1 and 230-2 perform beam sweeping to generate a plurality of narrow beams. After transmitting toward the terminal 210, the mobile relay node 230- 1, 230-2) may include narrow beams transmitted in virtual beam groups. On the other hand, the terminal 210 performs beam measurements on a plurality of narrow beams and wide beams transmitted from the distribution unit 220 and the relay nodes 230 - 1 and 230 - 2 of the base station, and the measured beam Virtual beam groups may be generated using the measurement results, and information on the generated virtual beam groups may be reported to the distribution unit 220 of the base station.

On the other hand, the method in which the terminal 210 selects a narrow beam from the virtual beam group and connects to the distribution unit 220 of the base station, the first mobile relay node 230-1, or the second mobile relay node 230-2 is (1) a single-beam access mode in which a best candidate beam is selected from candidate beams constituting a virtual beam group and connected using the selected best candidate beam; (2) two or more candidates from candidate beams constituting a virtual beam group Multi-beam access mode in which beams are selected and simultaneously accessed using the selected candidate beams, (3) the best candidate beam and the next best candidate beam are selected from the candidate beams constituting the virtual beam group and the selected best candidate beam is used to connect, and a hybrid mode in which a candidate beam of the selected lane is set to a dormant state may be considered. Here, the dormant state may mean a state in which L(layer)3 or more is connected but not connected to the L1/L2 radio link.

3 is a conceptual diagram illustrating a first embodiment of beams transmitted by a distribution unit of a base station.

Referring to FIG. 3 , the distribution unit 310 of the base station may simultaneously transmit a plurality of narrow beams NB1, NB2, ..., NBn and a plurality of broad beams WB0, WB1, ..., WBw. Here, n and w may be natural numbers. A plurality of narrow beams VBG(NB) transmitted by the distribution unit 310 of the base station may be expressed as in Equation 1 below. In addition, the plurality of wide beams VBG (WB) transmitted by the distribution unit 310 of the base station may be expressed as in Equation 2 below, and w may be a natural number. One of the plurality of broad beams WB0, WB1, ..., WBw (eg, WB0) may be a default beam.

As such, the distribution unit 310 of the base station may configure a plurality of sectors, and each sector may have one or more broad beams WB0, WB1, ..., WBw. As such, the distribution unit 310 of the base station may be connected to the 5G core network (5G-core, 5G-C) 330 via the central unit (CU) 320 of the base station. Here, the distribution unit 310 of the base station and the central unit 320 of the base station may constitute a base station. Here, the wide beam has a wide beam width like a sector beam or an omni beam of a general cellular system, so that it is possible to overcome the blocking of the visible path due to general obstructions (street trees, trucks, etc.). One wide beam may cover a plurality of (eg 32 or 64) narrow beams. In particular, the default beam (eg, WB0) may be designated by the distribution unit 310 of the base station or the terminal 320 from wide beams, and may be designated one by one for each sector. In this case, each sector may have at least one default beam and, if necessary, may have one or more wide beams. Here, the frequency of the broad beam may be the same as or different from that of the narrow beam. When the wide beam uses a different frequency band from the narrow beam, another radio access method (eg, LTE) may be used. When the wide beam uses the same millimeter band as the narrow beam, interference control between the narrow beam and the default beam may be considered. On the other hand, when the wide beam uses a millimeter band of a different band from the narrow beam, the beam coverage may be different from the narrow beam, so that the transmission power can be expanded so that the coverage of the wide beam can be more than a certain distance. On the other hand, when the wide beam and the narrow beam have different frequency bands and different radio access methods, the distribution unit 310 of the base station uses different radio access methods in a multi-RAT (multi-RAT) environment to set the default beam. and narrow beam can be transmitted simultaneously. That is, the distribution unit 310 of the base station may transmit a narrow beam using a millimeter wave band, and may transmit a wide beam using a part of a millimeter wave band or a part of a cellular band as follows.

- Default beam using millimeter wave band: The distribution unit 310 of the base station may allocate and utilize a specific band of the millimeter wave band as a default beam. In this case, the millimeter wave band resource may be wider than that of the cellular band, and since it is inexpensive, interference with a narrow beam may be avoided.

- Default beam using cellular band: The distribution unit 310 of the base station may dedicate some bands of the cellular band (eg, a specific band of 6 GHz or less) for the purpose of the default beam.

-Default beam using a shared band resource: In the case of general roads, national roads, and highways, it is possible to maintain an island-type radio environment compared to a national mobile communication network, so the distribution unit 210 of the base station is the existing A default beam may be transmitted by using a shared band resource (eg, a specific shared band of a 6 GHz band or less). In this case, the terminal 320 may use the default beam for a while, and may maintain the minimum communication quality required by the terminal 320 by returning the resource immediately. The minimum communication quality may be determined in consideration of the ratio and usage rate at which the terminal 320 can occupy the wide beam at the same time.

As described above, when the default beam is different from the narrow beam in both the frequency band and the radio access method, the terminal 320 simultaneously uses the narrow beam and the default beam during the communication period in the multi-RAT environment to the distribution unit 310 of the base station. can connect to That is, the terminal 320 communicating using the narrow beam can maintain the wide beam and the dormant connection state at the same time. Alternatively, the terminal 320 communicating using the narrow beam may maintain multi-connections at the same time. Alternatively, the terminal 320 communicating using the narrow beam can always maintain the L3 connection and maintain the L1/L2 connection in an on or off state. In addition, the terminal 320 communicating using the narrow beam may maintain all of the L1/L2/L3 connections in an off or all-on state. 3GPP 5G-NR standard can be applied mutatis mutandis for the above detailed related procedures.

4 is a conceptual diagram illustrating a first embodiment of a method for changing a beam in a communication system.

Referring to FIG. 4 , in a beam changing method in a communication system, the terminal 410 performs a narrow beam NB1 in virtual beam group 1 including narrow beams NB1 and NB2 and a default beam WB0 which is a broad beam at time t1. It can be connected to the distribution unit 420-1 of the source base station through. In this case, the virtual beam group 1 may not include the narrow beams NB3 and NB4 of the second and third mobile relay nodes 430 - 2 and 430 - 3 . Thereafter, the terminal 410 may move to meet the first obstacle 440-1 at time t2, and may receive a serving beam in virtual beam group 2 composed of narrow beams NB1 and NB2 and default beam WB0. By performing beam switching to change from the narrow beam NB1 of the distribution unit 420-1 of the source base station to the default beam WB0, which is a wide beam, it is possible to access the distribution unit 420-1 of the source base station through the default beam. there is. In this case, the terminal 410 may not use the first to third mobile relay nodes (430-1 to 430-3).

Meanwhile, the terminal 410 may move and meet the second obstacle 440-2 at time t3, and in the virtual beam group 3 composed of the default beam WB0 and the narrow beams NB3 and NB4, the default beam WB0 ) to the narrow beam NB4 of the third mobile relay node 430 - 3 may perform beam switching for changing the serving beam. The terminal 410 performs such beam switching to bypass the third mobile relay node 430-3 - the second mobile relay node 430-2 to access the distribution unit 420-1 of the source base station. there is. In this case, the virtual beam group 3 may include narrow beams NB3 and NB4 of the second and third mobile relay nodes 430 - 2 and 430 - 3 . In this way, in a situation where the terminal 410 meets the second obstacle 440-2, the multi-hop narrow beam NB4-NB3-NB2 passes through the adjacent second and third mobile relay nodes 430-2 and 430-3. Through the bypass, it is possible to connect to the distribution unit 420-1 of the source base station. Here, the terminal 410 is an end-to-end path topology structure between the second and third mobile relay nodes 430-2 and 430-3, and an end-to-end latency Candidate beams in virtual beam group 3 in consideration of minimizing the number of backhaul hops to reduce can select an optimal candidate beam that meets the corresponding service requirements.

Thereafter, the terminal 410 may move to leave the communication service area of the distribution unit 420-1 of the source base station at time t4 and move to the communication service area of the distribution unit 420-2 of the neighboring base station. In this case, the terminal 410 selects the narrow beam NB5 from the virtual beam group 4 including the narrow beam NB5 of the distribution unit 420 - 2 of the neighboring base station, and selects the narrow beam NB5 through the selected narrow beam NB5. It can be connected to the distribution unit 420-2. Meanwhile, the terminal 410 may periodically update the virtual beam group, where the update period may be, for example, a multiple of a radio frame. Also, the terminal 410 may update the virtual beam group when an event occurs, and the event may be, for example, beam switching or handover. In addition, since the terminal 410 stores the beam access information currently serving in the dormant state as it is, when the obstruction disappears, the access to the beam currently being served can be quickly restored.

5A and 5B are flowcharts illustrating a first embodiment of a method for changing a beam in a communication system.

Referring to FIGS. 5A and 5B , in a communication system, a terminal may search for adjacent mobile relay nodes and a source base station (S501). The terminal may create a virtual beam group based on a search result obtained by searching such adjacent relay nodes or source base stations (S502). That is, the terminal may perform beam measurements on a plurality of narrow beams and wide beams transmitted from the source base station and the mobile relay nodes. In addition, when the measured beam measurement results, that is, the received signal strength measured with respect to the plurality of narrow beams is equal to or greater than the first threshold, the terminal may create a virtual beam group including a plurality of narrow beams corresponding thereto. Also, the terminal may perform beam measurements on a plurality of wide beams transmitted from the source base station. In addition, when the measured beam measurement results, that is, the received signal strength measured for the plurality of wide beams is equal to or greater than the second threshold, the terminal may include a plurality of wide beams corresponding to the virtual beam group. Here, the first threshold value and the second threshold value may be different from or the same as each other. The terminal may select one of the plurality of wide beams as the default beam (S503). The terminal may request shape information for the selected default beam from the source base station (S504). Then, the source base station may transmit the shape information of the default beam required for the terminal to access using the default beam to the terminal. In this case, the source base station may transmit the shape information of the default beam to the terminal through system information block (SIB) or network signaling (eg RRC signaling) during call setup or communication using the serving narrow beam. The shape information of the default beam required for the terminal to access the source base station using the default beam may include L1 shape information and L2 shape information. Here, the shape information of L1 and the shape information of L2 may include the following information.

1) L1 shape information

1-1. Default beam index, frequency information of the default beam, frequency resource information of the default beam, default modulation and toning rate shape (eg 16-ary quadrature amplitude modulation (16QAM)), etc.

1-2. In addition, information related to various reference signals required for access to the default beam (for example, PSS (primary synchronization signal), SSS (secondary synchronization signal), PBCH (physical broadcast channel), SRS (sounding reference signal), CSI- RS (channel state information-reference signal), etc.

2) L2 shape information

2-1. Radio resource scheduling information that can be used exclusively for the default beam, resource allocation information required for a mobile device to use the default beam resource (for example, default designation, random designation, round-robin-based designation), etc.

2-2. If necessary, random access support information, etc.

The source base station may designate the shape information of the default beam as a minimum set of information, and may adjust the value according to the propagation environment. The terminal may receive the shape information of the default beam from the source base station and use the subsequent default beam to access the source base station (S505).

Next, the terminal may periodically search for adjacent mobile relay nodes and the source base station (S506). The terminal may update the virtual beam group based on the search result obtained by searching the adjacent relay nodes and the source base station (S507). That is, the terminal may perform beam measurements on a plurality of narrow beams and wide beams transmitted from the source base station and the mobile relay nodes. Then, the terminal receives the measured beam measurement results, that is, the plurality of narrow beams in which the received signal strength measured for the plurality of narrow beams is equal to or greater than the first threshold as the plurality of narrow beams in the previously generated virtual beam group. can be compared. If the comparison result is the same, the terminal may determine that there is no change in the virtual beam group. On the other hand, if the comparison result is not identical, the terminal determines that there is a change in candidate beams constituting the virtual beam group, and may update the virtual beam group to reflect the change. Meanwhile, in the terminal, the measured beam measurement results, that is, the plurality of broad beams having received signal strengths measured for the plurality of wide beams equal to or greater than the second threshold are the same as the plurality of wide beams in the previously generated virtual beam group. can be compared. If the comparison result is the same, the terminal may determine that there is no change in the virtual beam group. On the other hand, if the comparison result is not identical, the terminal determines that there is a change in candidate beams constituting the virtual beam group, and may update the virtual beam group to reflect the change. In more detail, when there is a change in the narrow beams transmitted from the mobile relay nodes, the terminal may reflect the change to newly select the narrow beams of the mobile relay nodes and include them in the virtual beam group. In addition, when there is a change in the narrow beams and wide beams transmitted from the source base station, the terminal may newly select the narrow beams and the wide beams of the source base station by reflecting these changes and include them in the virtual beam group.

In this case, when the selected default beam is excluded from the virtual beam group, the terminal may reselect the default beam from among the plurality of wide beams to update the default beam (S508). As such, as the default beam is changed, the terminal may request shape information on the default beam selected as the source base station (S509). Then, the source base station may transmit the shape information of the default beam required for the terminal to access using the default beam to the terminal. In this case, the source base station may transmit the shape information of the default beam to the terminal through system information (SIB) or network signaling (eg, RRC signaling) during call setup or communication using the serving narrow beam. The terminal may receive the updated default beam shape information from the source base station and use the subsequent default beam to access the source base station (S510).

Meanwhile, the terminal may determine whether the received signal strength of the narrow beam measured by measuring the received signal strength of the narrow beam serving as the serving beam during communication falls below the first threshold value and thus the received signal strength has sharply decreased ( S511 ). As a result of the determination, if the received signal strength of the narrow beam, which is the serving beam, does not decrease sharply, the terminal may repeat from step S506 of periodically searching for adjacent mobile relay nodes and the source base station. On the other hand, if the received signal strength of the narrow beam serving as the serving beam is sharply decreased as a result of the determination, the terminal may determine whether the movement speed of the terminal is equal to or greater than the speed threshold (S512). As a result of the determination, if the movement speed of the terminal is less than the speed threshold, the terminal moves relatively slowly, and may access the source base station through an access method using a mobile relay node. Contrary to this, when the movement speed is greater than or equal to the speed threshold, the terminal moves quickly and may access the source base station by using a default beam, which is a wide beam. In this case, the terminal may apply a time to trigger (TTT) differently depending on the movement speed in addition to the received signal strength of the serving beam. For example, if the moving speed is less than the speed threshold, TTT(H) is applied, and if it is above the speed threshold, TTT(L) may be applied to reduce the time required for beam switching. Here, TTT(H) may be greater than TTT(L). The UE has a very fast movement speed, so when rapid beam switching is required, the TTT may be set to a minimum value or may not be applied. Looking at this in more detail, it may be as follows.

During communication, the terminal may drop the received signal strength of the serving beam below the first threshold, and at the same time, when the movement speed of the terminal moves relatively slowly below the speed threshold, it is received in narrow beams of adjacent movable relay nodes in the virtual beam group. A narrow beam having the maximum signal strength may be selected (S513). Thereafter, the terminal may change the serving beam by performing beam switching from the narrow beam of the base station to the narrow beam transmitted by the target relay node (S514). A series of procedures required for the terminal to beam switch the narrow beam of the base station to the narrow beam of the target relay node may include procedures such as beam sweeping, beam measurement, beam synchronization, random access, and beam scheduling in the terminal and the target relay node. there is. Meanwhile, the terminal may select an adjacent mobile relay node corresponding to the selected narrow beam as the target mobile relay node and access it using the selected narrow beam (S515). In this case, the radio link signal strength (for example, reference signals received power (RSRP), SINR (signal to interference-plus-noise ratio) , CQI (channel quality indicator), load balancing, the number of multi-hops, separation distance, etc. can be further considered. For example, the terminal may use the maximum An adjacent mobile relay node having a separation distance may be selected as the target relay node.

Here, the terminal selects the narrow beam having the maximum received signal strength from the narrow beams of adjacent mobile relay nodes in the virtual beam group to change the serving beam, but the received signal strength in the narrow beams of the source base station is equal to or greater than the first threshold If there is a narrow beam, the serving beam may be changed to the corresponding narrow beam. The source base station may have an advantage in this case because the radio environment may be less unstable than the mobile relay nodes.

On the other hand, the terminal may be out of the radio wave blocking state of the obstruction by movement. At this time, the terminal measures the received signal strength of the narrow beam of the base station, which is the previous serving beam, before beam switching, and the measured received signal strength of the previous serving beam becomes more than the first threshold again, and determines whether the received signal strength of the previous serving beam sharply increases. It can be done (S516). At this time, if the received signal strength of the previous serving beam does not exceed the first threshold, the terminal may perform step S506 of periodically searching for adjacent mobile relay nodes and the source base station. Contrary to this, when the received signal strength of the previous serving beam of the source base station is equal to or greater than the first threshold, the terminal may determine whether reconnection to the base station is possible by reusing the narrow beam of the source base station, which is the previous serving beam (S517). As a result of the check, the terminal may determine whether reconnection to the base station is possible by reusing the narrow beam of the source base station (S518). In this case, the terminal may determine whether to reconnect in consideration of synchronization loss, packet loss, PER (packet error rate), and RLF (radio link failure) status of the previous serving beam. As a result of the determination, if reconnection is possible, the terminal may re-change the serving beam from the narrow beam of the target relay node to the previous serving beam of the source base station (S519). Then, the terminal may reconnect to the source base station (S520. If necessary, the terminal may perform beam scheduling through a MAC (medium access control) control procedure, etc. The terminal may configure a virtual beam group after re-changing the serving beam) In this case, the updated information in the information of the virtual beam group may be IDs (identifiers) of neighboring mobile relay nodes, IDs of source base stations, narrow beam indexes, etc. In this case, the terminal uses the existing serving A prerequisite for reconnection to the source base station using the existing narrow beam is that the terminal can store the L1/L2 shape parameters when disconnecting from the existing serving narrow beam and at the same time maintain the existing serving beam and dormant state. Accordingly, the UE may maintain L1/L2 shape information as well as L3 or higher shape information until it completely exits the previous serving beam and is completely released.

Meanwhile, if the terminal cannot reconnect as a result of the determination in step S518, the terminal may select a narrow beam having the maximum received signal strength from among the narrow beams of the source base station in the virtual beam group (S521). Thereafter, the terminal may change the serving beam to the narrow beam of the newly selected source base station (S522). Then, the terminal may access the source base station (S523). The terminal may access the source base station using a new serving beam through a series of procedures such as beam synchronization and beam scheduling. Here, when the terminal measures the received signal strength of the previous serving beam and exceeds the first threshold, steps 516 or less are performed. However, unlike this, the terminal always measures the received signal strength for other beams in the virtual beam group other than the current serving beam. When the first threshold or more is reached, a source base station transmitting the corresponding beam or an adjacent mobile relay node may be accessed using the corresponding beam.

Meanwhile, the terminal may select a default beam from the virtual beam group when the reception intensity of the serving beam may fall below the first threshold during communication and at the same time the movement speed of the terminal moves faster than the speed threshold (S524). Then, the terminal can change the serving beam by directly beam-switching the serving beam to the default beam (S525). Through this process, the terminal can maintain a connection state to the source base station. In this case, the terminal may omit a series of beam switching procedures if necessary, and may perform beam switching according to a hardware method. Here, the series of beam switching procedures may include procedures such as an adjacent beam sweeping procedure, a beam signal strength measurement procedure, a measurement result reporting procedure, and beam scheduling in the terminal and the source base station. In such a situation, as the terminal moves, it is possible to escape the radio interference from the obstruction. In this case, steps S516 to S523 may be performed. As another embodiment, the terminal can apply both the beam switching method using the default beam of the base station and the beam switching method using the narrow beam of the mobile relay node in an appropriate combination regardless of the movement speed. For example, when the source base station cannot use the default beam for any reason and only the mobile relay node is available, the terminal can access it using the mobile relay node regardless of the movement speed. Conversely, the terminal may not have an accessible mobile relay node nearby, and when there is an available default beam, it may access the source base station using the default beam, which is a wide beam, regardless of the movement speed. On the other hand, if both methods cannot be applied in an environment where the terminal encounters an obstacle, it may be treated as a beam link failure. In addition, all the beam switching scenarios described with reference to FIGS. 2 to 5C can be applied to a terminal at a subscriber walking speed level as it is. That is, when a millimeter wave interference phenomenon may occur while a general subscriber frequently changes direction during communication, the methods described above can be applied.

6 is a flowchart illustrating a first embodiment of a method for changing a beam in a communication system.

Referring to FIG. 6 , in the communication system, a terminal and a source base station may configure a virtual beam group, and may perform beam change preparation in advance by updating the configured virtual beam group ( S601 ). The terminal and the source base station may transmit and receive uplink (UL) data and downlink (DL) data using the serving narrow beam (S602). In addition, the source base station may transmit and receive 5G-C, uplink data, and downlink data (S603). When the terminal enters the communication interference area of an obstacle during communication, it can be determined whether the received signal strength of the narrow beam measured by measuring the received signal strength of the narrow beam serving as the serving beam falls below the first threshold and the received signal strength has sharply decreased. . Through this determination, the terminal can detect a sharp decrease in the received signal strength of the narrow beam serving as the serving beam (S604). The terminal may select a narrow beam (herein referred to as a target beam) having the maximum received signal strength from narrow beams of adjacent mobile relay nodes in the virtual beam group ( S605 ). Thereafter, the terminal may change the serving beam by performing beam switching from the narrow beam of the source base station to the narrow beam transmitted by the mobile relay node corresponding to the target beam, that is, the target beam (S606). Here, the beam switching may include a series of procedures such as beam synchronization for access and scheduling of beam resources. Meanwhile, the terminal may access the adjacent movable relay node corresponding to the selected narrow beam using the selected narrow beam, that is, the target beam (S607). The terminal and the mobile relay node may transmit/receive uplink data and downlink data using the serving narrow beam (S608). In addition, the mobile relay node may transmit/receive 5G-C, uplink data, and downlink data (S609). At this time, when it may be difficult for the terminal to predict when an obstacle will appear, and the signal strength of an adjacent mobile relay node in charge of a relay may also be unstable, a plurality of narrow beams in the virtual beam group are used for the safety of communication connection. Therefore, it is possible to have a multi-beam access mode in which the adjacent relay nodes are simultaneously accessed.

On the other hand, the terminal may move out of the jamming area of the obstruction, and in this case, the terminal may determine whether the received signal strength of the previous serving beam used before beam switching rises above the first threshold again. Through this determination, when the received signal strength of the previous serving beam rises above the first threshold again, the terminal may detect a surge in the received signal strength of the previous serving beam (S610). The terminal may determine whether reconnection with the source base station is possible using the previous serving beam. If the UE determines that reconnection with the source base station is possible through the previous serving beam, the UE may change the serving beam by performing beam switching using only a minimal procedure such as beam resource scheduling using MAC control (S611). Then, the terminal may reconnect to the source base station (S612. If necessary, the terminal may perform beam scheduling through a MAC (medium access control) control procedure, etc.) Link data and downlink data may be transmitted/received (S613), and the source base station may transmit/receive uplink data and downlink data with 5G-C (S614).

7 is a conceptual diagram illustrating a second embodiment of a method for changing a beam in a communication system.

Referring to FIG. 7 , in a communication system, a terminal 710 may access a distribution unit 720 of a base station through a narrow beam NB1 at time t1 . Thereafter, the terminal 710 may move and meet the obstacle 730 at time t2, and in the virtual beam group, the serving beam in the narrow beam NB1 of the distribution unit 720 of the base station is the default beam WB0. ), it is possible to access the distribution unit 720 of the base station through the default beam by performing beam switching.

Meanwhile, the terminal 710 may move out of the communication interference area of the obstruction 730 at time t3 and reconnect to the distribution unit 720 of the base station using the narrow beam NB2 .

8 is a flowchart illustrating a second embodiment of a method for changing a beam in a communication system.

Referring to FIG. 8 , in the communication system, a terminal and a source base station may configure a virtual beam group, and may perform beam change preparation in advance by updating the configured virtual beam group ( S801 ). In this case, whenever the source base station is changed, the terminal may update the default shape information (L1/L2 parameters) required to perform beam switching with the default beam. In this case, the terminal may take a multi-connection state or a dormant access state for access using the default beam with the source base station. These procedures may follow 3GPP standard procedures. Meanwhile, the terminal and the source base station may transmit/receive uplink data and downlink data using the serving narrow beam (S802). Then, the source base station may transmit and receive 5G-C, uplink data, and downlink data (S803). When the terminal enters the communication interference area of the obstruction during communication, it can be determined whether the received signal strength of the narrow beam measured by measuring the received signal strength of the narrow beam serving as the serving beam falls below the first threshold and the received signal strength has sharply decreased. . Through this determination, the terminal can detect a sharp decrease in the received signal strength of the narrow beam serving as the serving beam (S804). The terminal may select a default beam from the virtual beam group (S805). Thereafter, the terminal may change the serving beam by performing beam switching from the narrow beam of the source base station to the default beam (S806). The terminal and the source base station may transmit and receive uplink data and downlink data using the serving default beam (S807). Then, the source base station may transmit and receive uplink data and downlink data with 5G-C (S808).

On the other hand, the terminal may move out of the jamming area of the obstruction, and in this case, the terminal may determine whether the received signal strength of the previous serving beam used before beam switching rises above the first threshold again. Through this determination, when the received signal strength of the previous serving beam rises above the first threshold again, the terminal may detect a surge in the received signal strength of the previous serving beam (S809). The terminal may determine whether reconnection with the source base station is possible using the previous serving beam. If it is determined that the UE can reconnect with the source base station through the previous serving beam, the UE may change the serving beam by performing beam switching using only a minimal procedure such as beam resource scheduling using MAC control (S810). Then, the terminal and the source base station can transmit and receive uplink data and downlink data using the serving narrow beam (S811). And, the source base station may transmit and receive 5G-C, uplink data, and downlink data (S812).

9 is a conceptual diagram illustrating a first embodiment of a process in which a terminal performs beam switching from a narrow beam to a default beam.

Referring to FIG. 9 , when the terminal enters the interference area 900 of the obstacle in the process of the terminal beam switching from the narrow beam to the default beam, the offset measurement value of the reception signal strength 910 of the serving beam is the entry reception signal It may be greater than or equal to the intensity offset threshold (TH_RX_BEAM_OFF_POWER_IN) 921, and it may be determined whether the duration (TTT) satisfies the entry trigger time threshold (T_OFFSET_IN) 941. The terminal measures the offset of the received signal strength of the serving beam The value may be greater than or equal to the entry received signal strength offset threshold 921, and if the duration satisfies the entry trigger time threshold, the currently connected narrow beam may be switched to the default beam. Here, the reception signal strength of the serving beam The offset of may be the difference from the received signal strength of the currently serving narrow beam in the received signal strength of the default beam measured by the terminal 930. At this time, when the terminal moves very quickly, it is necessary to reduce the possibility of communication interruption. Accordingly, the duration of entry can be minimized or neglected.

On the other hand, when the terminal exits the communication interference area 900 of the obstacle, the offset measurement value of the reception signal strength 910 of the serving beam may be greater than or equal to the exit reception signal strength offset threshold (TH_RX_BEAM_OFF_POWER_OUT) 922, and the duration thereof If the exit trigger time threshold (T_OFFSET_OUT) 942 can be satisfied, the terminal can beam-switch the currently connected default beam to a narrow beam. In the drawing, reference numeral 943 may be a period during which the terminal can communicate using the default beam.

10 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

Referring to FIG. 10 , the communication node 1000 may include at least one processor 1010 , a memory 1020 , and a transceiver 1030 connected to a network to perform communication. Also, the communication node 1000 may further include an input interface device 1040 , an output interface device 1050 , a storage device 1060 , and the like. Each of the components included in the communication node 1000 may be connected by a bus 1070 to communicate with each other. However, each of the components included in the communication node 1000 may not be connected to the common bus 1070 but to the processor 1010 through an individual interface or an individual bus. For example, the processor 1010 may be connected to at least one of the memory 1020 , the transceiver 1030 , the input interface device 1040 , the output interface device 1050 , and the storage device 1060 through a dedicated interface. .

The processor 1010 may execute a program command stored in at least one of the memory 1020 and the storage device 1060 . The processor 1010 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. The processor 1010 may be used to control operations required for communication between the terminal or the base station and the terminal and the base station. For example, the processor 1010 may control operations such as beam sweeping, measurement, and reporting functions performed between the terminal and the base station. Each of the memory 1020 and the storage device 1060 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 1020 may be configured as at least one of a read only memory (ROM) and a random access memory (RAM). The memory 1020 may store information necessary for the virtual beam group, and may store various information necessary for the operation of the processor 1010 . The transceiver 1030 may transmit or receive a radio signal, and may have multiple antennas for this purpose. Here, the multi-antenna may be both integral and modular, and may generate one or more narrow beams and one or more broad beams.

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 may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions may 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.

In addition, the above-described method or apparatus may be implemented by combining all or part of its configuration or function, or may be implemented separately.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that it can be done.

Claims (1)

A method of operating a terminal of a communication system, comprising:
forming a virtual beam group including a first beam of a first type, a second beam of a second type, transmitted by a base station, and a plurality of beams of the first type, transmitted by relay nodes;
transmitting and receiving data to and from the base station using the first beam of the first type transmitted by the base station; and
When the terminal moves and the received signal strength of the first beam becomes less than the first threshold due to an obstruction, the beam shape is changed to the second type of second beam to transmit/receive data to and from the base station or in the virtual beam group Selecting another beam of a first type and changing it to a selected beam, and transmitting and receiving data with the base station using the selected beam, wherein the first type is a narrow beam and the second type is a wide beam. how it works.

Images