KR20190074939A - Method for handover in mobile communication system and apparatus for the same - Google Patents

Abstract

Disclosed is an operating method of a base station performing handover in a mobile communication system. According to the present invention, the handover operating method of a base station comprises: a step of generating handover triggering TA information indicating information on TA handover-triggered by at least one among a mobile relay (MR) of a high speed moving body and a terminal; a step of receiving at least one among SRS, PUCCH and PUSCH from at least one among the MR of the high speed moving body and the terminal; a step of using receiving time information of at least one among the received SRS, PUCCH and PUSCH to generate TA information to be transmitted to the MR of the high speed moving body or the terminal; a step of determining whether handover is needed based on the TA information to be transmitted to the MR of the high speed moving body or the terminal and the handover triggering TA information; and a step of transmitting a handover trigger message to at least one among a target base station, the MR of the high speed moving body, and the terminal if handover is needed.

Description

TECHNICAL FIELD [0001] The present invention relates to a handover method and apparatus in a mobile communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handover method and apparatus in a mobile communication system, and more particularly, to a fast handover method and apparatus for a communication apparatus mounted on a high-speed mobile station moving on a fixed path.

The 5th generation mobile communication which aims at supporting Gbps (Giga bps) class which is at least 10 to 100 times data transmission rate than the 4th generation mobile communication is not limited to the support of enhanced mobile broadband (eMBB) (massively machine type communication) and ultra-reliable low latency communication (URLLC).

In the fifth generation mobile communication system, a baseband unit (BBU) for baseband signal processing and a radio signal processing Lt; RTI ID = 0.0 > RF < / RTI > devices.

On the other hand, 3GPP NR (new radio) (hereinafter referred to as " NR "), one of the fifth generation mobile communication standards, provides robust high-speed wireless communication service to a terminal of a passenger boarding a high- . In this case, a handover scheme considering the characteristics of a high-speed mobile body moving along a predetermined path at a speed of several hundred kilometers per hour should be considered.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a method and apparatus for providing an MR or a terminal of a high-speed train moving at high speed along a corresponding route in a base station including unidirectional RRHs installed in accordance with a fixed route, Handover.

According to an aspect of the present invention, there is provided a base station handover method in a mobile communication system including a timing advance (TA) triggered by handover to at least one of a mobile relay (MR) Generating at least one of a sounding reference signal (SRS), a physical uplink control channel (PUCCH), and a physical uplink shared channel (PUSCH) from at least one of the MR and the terminal of the fast moving vehicle Generating TA information to be transmitted to the MR or the MS of the high-speed mobile station using at least one reception time information of the received SRS, PUCCH, and PUSCH, and transmitting the TA to the MR Determining whether handover is necessary based on the handover triggering TA information, And transmitting a handover trigger message to at least one of a target base station and an MR or a terminal of the fast moving object.

According to the present invention, a base station including unidirectional RRHs installed according to a fixed movement path in the NR can provide a stable and efficient handover to an MR or a terminal of a high-speed train moving at high speed along the movement route.

1 is a conceptual diagram showing a first embodiment of a communication system.
2 is a block diagram showing an embodiment of a communication node constituting a communication system.
3A is a conceptual diagram illustrating communication between a terminal of a high-speed mobile station and a bi-directional C-RAN in an NR.
3B is a conceptual diagram illustrating communication between a terminal of a high-speed mobile station and a unidirectional C-RAN in an NR.
4 is a flowchart illustrating a handover method based on downlink RSRP measurement according to an embodiment of the present invention.
5 is a flowchart illustrating a handover method based on monitoring uplink signal arrival time according to an embodiment of the present invention.
6 is a conceptual diagram illustrating a handover method based on a beam index number of a base station unidirectional RRH in an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

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

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

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

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1 is a conceptual diagram showing a first embodiment of a communication system.

1, a communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 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 be a wireless communication device based on a communication protocol based on a code division multiple access (CDMA) communication protocol, a communication protocol based on a wideband CDMA (WCDMA), a communication protocol based on a time division multiple access (TDMA) based communication protocol, an orthogonal frequency division multiplexing (OFDM) based communication protocol, an OFDMA (orthogonal frequency division multiple access) based communication protocol, a single carrier-FDMA based communication protocol, a non-orthogonal multiple access-based communication protocol, and a space division multiple access (SDMA) -based communication protocol. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing 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 the network to perform communication. 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 and communicate with each other. However, each component included in the communication node 200 may not be connected to the common bus 270 but may be connected to the processor 210 via an individual interface or a separate bus. For example, the processor 210 may be coupled to at least one of the memory 220, the transceiver 230, the input interface 240, the output interface 250 and the storage 260 via a dedicated interface .

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

Referring again to FIG. 1, the communication system 100 includes a plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2, a plurality of user equipments ) 130-1, 130-2, 130-3, 130-4, 130-5, and 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 to 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.

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1 and 120-2 includes a Node B, an evolved Node B, a base transceiver station (BTS) A wireless base station, a radio transceiver, an access point, an access node, a roadside unit (RSU), a digital unit (DU), a cloud digital unit (CDU) , Radio remote head (RRH), radio unit (RU), transmission point (TP), transmission and reception point (TRP), relay node, gNB, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 includes a terminal, an access terminal, a mobile terminal, May be referred to as a station, a subscriber station, a mobile station, a portable subscriber station, 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, Each can support cellular communication (e.g., long term evolution (LTE), advanced (LTE-A), 5G NR (new radio), 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 via an ideal backhaul or a non-ideal backhaul, Or non-idle 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 idle backhaul or a non-idle 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, 130 130-2, 130-3, 130-4, 130-5, and 130-6, and transmits the signals received from the terminals 130-1, 130-2, 130-3, 130-4, Lt; / RTI >

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support downlink transmission based on OFDMA, and uplink ) Transmission. Also, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may perform multiple input multiple output (MIMO) transmission (for example, MIMO, MIMO, MIMO, Coordinated Multipoint (CoMP), Carrier Aggregation, Unlicensed Band, Device to Device (D2D) Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may support communication (or ProSe (proximity services) (110-1, 110-2, 110-3, 120-1, 120-2) corresponding to the base stations 110-1, 110-2, 110-3, 120-1, Supported actions can be performed.

For example, the second base station 110-2 can transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 can transmit a signal based on the SU-MIMO scheme And may receive a signal 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, the fourth terminal 130-4, And the fifth terminal 130-5 may receive signals from the second base station 110-2 by the MU-MIMO scheme. Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 can transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, The terminal 130-4 can 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 terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6) and the CA scheme. 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, the fourth terminal 130-4 and the fifth terminal 130-5 may be coordinated by the coordination of the second base station 110-2 and the third base station 110-3, Can be performed.

Next, handover techniques for a communication node mounted on a high-speed mobile body will be described. Here, even when a method (for example, transmission or reception of a signal) to be performed in the first communication node among the communication nodes is described, the corresponding second communication node is equivalent to the method performed in the first communication node (E.g., receiving or transmitting a signal). That is, when the operation of the terminal is described, the corresponding base station can perform an operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, the corresponding terminal can perform an operation corresponding to the operation of the base station.

In the case of the fifth generation mobile communication system, there is a need for a mobile communication system in which a plurality of terminals using communication services such as buses, subways, high-speed trains, etc., It aims to provide communication service. A terminal in a moving high-speed mobile terminal may receive a communication service through a wireless communication network outside the vehicle, but may be a wireless local area network (WLAN), a femtocell or a moving relay (MR) combined with a mobile wireless backhaul relay through a mobile communication node in the vehicle.

It is expected that the fifth generation mobile communication will be implemented in the frequency band of several tens of GHz (Giga Herz), which aims at supporting Gbps (Giga bps) class which is at least 10 to 100 times the data transmission rate of the fourth generation mobile communication. For example, implementation is being discussed in the 30 GHz to 60 GHz frequency band (the wavelength at 30 GHz is 10 mm). The fifth generation mobile communication technology is also referred to as millimeter wave (hereinafter referred to as "millimeter wave ") mobile communication technology because the wavelengths in the higher frequency band and the lower frequency band are also expressed in mm.

In addition, there are a number of RF devices such as a remote radio head (RRH) and a cloud radio access network (C-RAN) using a virtual base station consisting of a baseband unit (BBU) ) Type wireless communication technology is also an important technology for the fifth generation mobile communication system. Baseband devices and RF devices are interconnected in a wired or wireless manner, such as fiber-optic cables. When a base station having such a baseband device and a plurality of RF devices connected thereto is used, interference between cells can be easily adjusted and a high quality communication service through cooperative communication is possible.

NR aims at providing a robust high-speed wireless communication service to a terminal of a passenger aboard a high-speed mobile body such as a high-speed train (hereinafter, the high-speed mobile body in the embodiments of the present invention means a high-speed train, And the present invention is not limited thereto). In this case, the terminal in the high-speed mobile unit can directly communicate with the communication node outside the high-speed mobile unit, and can communicate with the external communication node using the MR in the high-speed mobile unit. Next, a method of providing a communication service to a terminal in a high-speed mobile station such as a communication high-speed train using the C-RAN scheme in the NR will be described.

3A is a conceptual diagram for explaining communication between a terminal of a high-speed mobile station and a bidirectional C-RAN in NR, and FIG. 3B is a conceptual diagram illustrating communication between a terminal of a high-speed mobile station and a unidirectional C-RAN in NR.

Referring to FIG. 3A, a base station (also called eNodeB or gNodeB) uses a 4 GHz carrier frequency and uses one bidirectional RRH 320 per BBU 330 to provide communication service to a high-speed mobile 310 such as a high- . The BBU of the base station may be coupled to one or more RRHs. A high-speed moving object such as a high-speed train moves along a predetermined fixed path and can know the average speed of the high-speed moving object according to the moving path (railroad path section) in advance. Therefore, it is possible to arrange the base station to provide the NR communication service according to the route section to the passenger of the high speed mobile body.

Also, in consideration of the characteristics of a high-speed moving object such as a high-speed train moving at a high speed, the beam forming direction of the RRH disposed around the moving path of the high-speed moving object can be adjusted or fixed in a bidirectional or unidirectional manner. Therefore, the BBU and the RRH of the base station can be arranged at optimal positions along the movement route in advance, thereby providing high-speed data at high speed to the high-speed mobile terminal economically.

Referring to FIG. 3B, a base station uses a 30 GHz carrier frequency and uses three unidirectional RRHs 360-1, 360-2, and 360-3 per BBU 350 to transmit to a high-speed mobile station 340 such as a high- And a communication service is provided. The arrangement of BBU and RRH shown in FIG. 3B is such that the center between two adjacent RRHs is not a cell boundary, but the neighborhood of neighboring RRHs is arranged to be the cell boundary. As described above, the terminal in the high-speed mobile terminal can perform the direct communication through the external RRH or perform the communication through the MR mounted on the high-speed mobile terminal.

Meanwhile, when handover between the Node Bs of an NR that provides a high-speed data service to a terminal in a high-speed train using a unidirectional RRH is performed, the conventional handover is not appropriate. When a communication service is provided to an MR or a terminal of a high-speed mobile station through a unidirectional RRH, an MR or a mobile station of a high-speed mobile station can receive control and data information from a source base station having a stronger signal strength than a target base station It is because.

Therefore, when the signal strength from the target base station is greater than the signal strength from the source base station, when the signal strength of the target base station becomes larger after comparing the signal strengths of the source base station and the target base station, The over scheme is no longer valid. Next, a handover method according to an embodiment of the present invention will be described in a case where a downlink signal is transmitted through a unidirectional RRH in the NR to provide a communication service to an MR or a terminal of a high-speed mobile station.

4 is a flowchart illustrating a handover method based on downlink RSRP measurement according to an embodiment of the present invention.

Referring to FIG. 4, an MR in a high-speed mobile station or a mobile station receives a synchronization signal from unidirectional beam RRHs of a source base station and a target base station, compares signal strengths of received synchronization signals, Over. ≪ / RTI > Herein, the unidirectional beam RRH denotes an RRH which is fixed or adjusted such that at least one beam installed in the RRH is directed in a specific direction (opposite to the traveling direction of the fast moving object). In the following embodiments of the present invention, It is called.

For example, the unidirectional beam of the RRH in the embodiment of the present invention may be fixed or adjusted to face the approaching high-speed train to the corresponding unidirectional RRH. At this time, the unidirectional beam of the RRH can be fixed or adjusted only in the approach direction of the train based on the unidirectional RRH.

As described above, since NR is expected to be implemented to support operation in a wide frequency band ranging from several hundred MHz to several tens of GHz, in order to solve the problem of cell coverage reduction due to this, a beam forming method is used in a high frequency band To increase the cell coverage.

Such beamforming includes an analog beam forming method and a digital beam forming method. The digital beamforming scheme uses a plurality of radio frequency (RF) paths based on a multiple input multiple output (MIMO) antenna and a digital precoder or a codebook to generate a beamforming gain gain. The analog beamforming scheme achieves beamforming gain through a number of analog devices and antenna arrays, such as a phase shifter, a power amplifier (PA), and a variable gain amplifier (VGA).

When cell coverage is increased through beamforming, not only the dedicated control channel and dedicated data transmitted to the UEs in the cell but also the common control channel and common signals transmitted to all the UEs in the cell are also beamformed Lt; / RTI > However, in this case, the common signal including the common control channel and the synchronization signal can not be transmitted to the entire cell area through one transmission, and the signal is transmitted through a plurality of beams over a plurality of times for a predetermined period of time It is called beam sweeping.

Meanwhile, a terminal connected to the mobile communication system obtains downlink frequency / time synchronization acquisition and cell ID information through a synchronization signal, and acquires uplink and downlink synchronization through a random access procedure and forms a wireless link with the base station. NR transmits a synchronization signal using a synchronization signal burst (SSB).

The SSB consists of one or more synchronization signal blocks (SSBk), and a synchronization signal burst set (SSBS) consists of one or more SSBs (where the synchronization signals include PSS and SSS). That is, when SSBk is transmitted using beamforming, a beam sweeping operation is required in which a plurality of beams are transmitted while being switched. For this purpose, a plurality of SSBs can be allocated within the synchronization signal transmission period. SSBs gather to form SSBS (this is called joint SS structure).

The maximum number of SSBks constituting one SSBS, the number of SSBks used in actual transmission and the location of SSBk may vary depending on the mobile communication system, and the maximum number of SSBks in the SSBS may vary according to the frequency band of the mobile communication system . For example, it can have up to four SSBk in the band below 3 GHz, up to 8 in the band of 3 ~ 6 GHz, and up to 64 SSBk in the band above 6 GHz.

One SSB includes a synchronous signal multiplexed in a time division multiplexing (TDM) scheme and a physical broadcasting channel (PBCH). The SS transmits an SSB index, an OFDM symbol index, or a slot ) Index information can be found explicitly or implicitly.

Each SSB can also be considered as a beam group. The SSBk in each SSB may be located in different beams in the beam group. Such an SSB structure is applicable to single beam or multi-beam operation. This SS structure enables multi-beam operation for high-speed communication service of high-speed mobile objects. The different SSBs may be transmitted via different beams as a reference signal (RS) for beam measurement in the RRH.

The MR or terminal of the high speed mobile may receive the SSB transmitted from the unidirectional RRH of the source base station (410). The MR of the high-speed mobile unit or the UE can measure the RSRP (reference signal received power), which is the signal strength of the SSB received from the unidirectional beam RRH of the source base station. The MR or terminal of the fast moving object may receive the SSB transmitted from the unidirectional beam RRH of the target base station (420). The MR or the MS of the high-speed mobile can measure the signal strength of the SSB received from the unidirectional beam RRH of the target base station.

The MR of the high-speed mobile unit or the MS may compare the received signal strength RSRP of the SSB received from the unidirectional beam RRH of the source base station and the target base station to determine whether handover is required (S430). If the signal strength of the SSB received from the unidirectional beam of the target base station is stronger than the signal strength of the SSB received from the unidirectional beam of the source base station, the MR or terminal of the high-speed mobile station transmits a handover request such as an A3 handover trigger message Message can be transmitted.

The MR or the MS of the high-speed mobile can receive the handover complete message to the target BS (S450). The source base station can not receive the control information and / or data from the MR or the terminal of the high-speed mobile station, so that the source base station can recognize that the high-speed mobile unit has moved outside its coverage area. Or the BBU of the target base station may notify the source base station through the X2 interface that the MR of the high-speed mobile unit or the mobile station has moved from the source base station to the target base station.

If the signal strength of the CSI-RS received from the target BS is larger than the signal strength of the CSI-RS received from the unidirectional RRH of the source BS and the target BS as well as the SSB, Lt; RTI ID = 0.0 > a < / RTI > Next, a description will be made of a handover method according to an embodiment of the present invention in a case where a communication service is provided to an MR or a terminal of a high-speed mobile station via a unidirectional RRH that receives an uplink signal in the NR.

Unlike the embodiment of FIG. 4, the unidirectional RRH of the source base station and the unidirectional RRH of the target base station receive the SRS (sounding reference signal) transmitted from the MR or the terminal of the high-speed mobile station, When the RSRP reaches a certain level or more, the target base station or the source base station can transmit a handover trigger message requesting a handover to an MR or a mobile station of a high-speed mobile station. The target base station or the source base station that has transmitted the handover trigger message can request to prepare the handover to the source base station or the target base station via the X2 interface.

Alternatively, since the source base station can expect a rough position of the high-speed mobile station that runs at a predetermined time at a fixed speed, the source base station prepares for handover in advance, and then, before the mobile station moves out of the cell coverage of the source base station, And may request the base station to prepare for handover. Next, a handover method based on the monitoring of the reception timing of the uplink and downlink signals in the NR unidirectional RRH according to an embodiment of the present invention will be described. Next, a description will be given of a handover method according to an embodiment of the present invention based on the monitoring of the uplink and downlink signal arrival times in a case where a communication service is provided to an MR or a terminal of a high-speed mobile station in the NR.

5 is a flowchart illustrating a handover method based on monitoring of uplink signal arrival time according to an embodiment of the present invention.

Referring to FIG. 5, a source base station including a unidirectional RRH in a NR generates a handover trigger using timing information of an MR in a high-speed mobile station or an SRS transmitted from a UE.

TA (timing advance) is a medium access control control (MAC) element used to control uplink signal transmission timing at a base station. A base station measures a time difference between a reception timing of at least one of a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a sounding reference signal (SRS) transmitted from a mobile station and a subframe timing And controls the terminal to adjust the uplink transmission time so that the PUSCH, PUCCH, and SRS transmitted from the terminal are aligned with the subframe timing at the base station.

The base station including the unidirectional RRH according to an embodiment of the present invention can recognize the reception timing information of the uplink signal such as the SRS, the moving speed of the high-speed mobile and the position on the moving route, (Handover triggering TA information) (e.g., PUSCH and PUCCH may be used instead of SRS) (S510).

At this time, the base station can transmit the information about the TA to which the handover is triggered from the source base station or the previous source base station to which the wireless link is currently set to the MR or the terminal of the high-speed mobile station (not shown). Accordingly, the MR or the UE of the high-speed mobile station can know which TA information the current source base station is performing the handover trigger.

The MR or the terminal of the high-speed mobile may transmit the SRS to the source base station (unidirectional RRH) (S520). The source base station receiving the SRS can transmit the appropriate TA information to the MR or the terminal of the high-speed mobile station. At this time, the source base station can generate the TA information and know the distance between the high-speed mobile unit and the corresponding source base station. Thus, the source base station can determine whether handover is required (S530). For example, when the TA information is close to 0, it is determined that the high-speed mobile station will soon be out of cell coverage of the base station of the unidirectional RRH, and the handover can be prepared.

The source base station may transmit a handover trigger message requesting handover request / preparation to the target base station in step S540 if the high-speed mobile unit is expected to be out of cell coverage of the source base station through the TA information generation process. In addition, the source base station may transmit a handover trigger message (may also be referred to as a handover command message) to the MR of the high-speed mobile unit or the terminal in operation S550.

 On the other hand, between the beam transmitted from the RRH of the source base station and the beam transmitted from the RRH of the target base station, the degree of overlap between the main lobe and the side lobe between the beams due to the movement of the high- A handover ping-pong effect may occur.

In a base station including a unidirectional RRH according to an exemplary embodiment of the present invention, a handover method that uses uplink signal reception timing information such as SRS, a moving speed of a high-speed mobile station, and location information on a path may prevent the handover ping- can do. Next, a handover method based on the monitoring of the downlink signal arrival time according to an embodiment of the present invention will be described.

In the handover method based on downlink signal arrival time monitoring according to an embodiment of the present invention, an MR or a terminal of a high-speed mobile station can generate a handover trigger by using MR or a terminal using TA information transmitted from a base station. To this end, the MR or the UE of the high-speed mobile station can receive information on whether a handover trigger is required according to the TA information (information indicating which handover trigger is generated when a TA is received) from the source base station in advance.

The MR or the UE of the high-speed mobile station can generate a handover trigger using the TA information received from the source base station and information on whether handover trigger generation is required according to the received TA information, and transmit the handover trigger to the target base station.

In this case, even if the source base station does not receive the handover trigger related information from the MR or the terminal of the high-speed mobile station, the location of the high-speed mobile station can be estimated using the transmitted TA information. . Alternatively, the source base station can separately receive information about the handover completion from the target base station to the MR of the high-speed mobile station or the target base station of the terminal via the X2 interface with the target base station. Next, a description will be given of a handover method according to an embodiment of the present invention based on the beam index number of the base station RRH in a case where a communication service is provided to an MR or a terminal of a high-speed mobile station in the NR.

6 is a conceptual diagram illustrating a handover method based on a beam index number of a base station unidirectional RRH in an embodiment of the present invention.

Referring to FIG. 6, a source base station (BBU) connected to a plurality of unidirectional RRHs in a NR generates a handover trigger using beam index information transmitted to an MR of a fast moving object or a mobile station. The NR base station according to an embodiment of the present invention can transmit different SSBs for each beam of the base station RRH.

In this case, an index is assigned to each beam of the RRH to determine whether the MR of the high-speed mobile station or the SSB received by the UE has SSB transmitted from a beam index having a beam index. And so on.

For this, the source base station (BBU) may transmit RRH information and beam index information (beam index mapping table information) mapped to the RRH information and RRH beam numbers in advance to the MR or the terminal of the high-speed mobile station (S610). Using this information, the MR of the high-speed mobile station or the UE can know which RRH is currently provided with the communication service and which beam in the RRH is used to receive the SSB.

The RRH of the current base station may transmit the SSB to the MR of the high-speed mobile station or the terminal using the specific beam (S620). At this time, the beam index information together with the SSB can be transmitted to the MR or the terminal of the high-speed mobile station simultaneously or separately (not shown in the figure) by a separate signal or channel.

The MR or the UE of the high-speed mobile can grasp the RRH information for transmitting the SSB and the beam information of the RRH using the beam index information transmitted separately or the beam index mapping table information previously received. Alternatively, the MR or terminal of the high-speed mobile station can know the beam index information that is currently communicated by the downlink reference signal or channel such as SSB and CSI-RS in a quasi-co-location (QCL) state.

If the UE knows that the wireless channel experienced by two different antenna ports of the communication node transmitting and receiving unit has similar large-scale characteristics, the UE can set a parameter for wireless channel estimation using the same. The use of this characteristic is a quasi-co-location (QCL) concept between antenna ports.

If the antenna port associated with the beam transmitting the SSB and the antenna port associated with the beam transmitting the CSI-RS are in the QCL state, the MR of the high-speed mobile station or the UE may transmit the corresponding wireless channel It can be assumed that the aforementioned large-scale characteristics of the channel are the same. The terminal can receive whether the two specific antenna ports can be assumed to be QCL (QCL information) through base station signaling.

The fact that the channels experienced by both CSI-RS and SSB signals are quite similar in terms of the large-scale channel means that the Doppler spread of the radio channels experienced by the two signals transmitted from two different antenna ports of the same base station ), Average delay spread, average gain, etc. may be the same or similar.

On the other hand, according to the movement of the high-speed moving object, SSB can be transmitted also in the outermost RRH (RRH m in FIG. 6) of the source base station in the fast moving object traveling direction (S630). If the source base station is provided with a communication service by the MR of the high-speed moving object or the outermost RRH beam of the high-speed moving object among the beams of the RRH of the current source base station (the beam n of RRH m in FIG. 6), the source base station (BBU) After generating the trigger message, the base station transmits a trigger message to the target base station (BBU) through the X2 interface or the like to request handover preparation (S640).

At this time, the source base station (BBU) may transmit a handover command message (which may also be referred to as a handover trigger message) to the MR or the terminal of the high-speed mobile station (not shown).

The source base station (BBU) receives feedback on direct beam information from the MR or the terminal or the SRS measurement transmitted from the MR or the terminal as to whether the MR of the high-speed mobile object or the terminal is receiving the communication service by the beam of the source base station RRH .

Meanwhile, the MR or the UE of the high-speed mobile station receives the beam index mapping table information for the beam of the RRHs of the corresponding source base station from the source base station in advance, Over preparation can be done.

That is, when the beam of the RRH and RRH that are provided with the communication service by the movement along the fixed path fluctuates, the MR or the terminal of the high-speed mobile station knowing the beam index mapping information, (The beam n of RRH m of the source base station in the embodiment of FIG. 6, and the RRH coverage generated by the beam can be referred to as a handover area) of the outer RRH A handover trigger can be generated by itself and transmitted to the target base station (S650).

At this time, since the source base station knows the beam information of the RRH and RRH that the current source base station provides the MR or the communication service to the mobile station of the high-speed mobile station, the handover trigger situation . Alternatively, the source base station may receive the handover trigger information directly from the MR or the terminal of the high-speed mobile station.

The methods according to the present invention can be implemented in the form of program instructions that can be executed through various computer means and recorded on 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 those specially designed and constructed for the present invention or may be available to those skilled in the computer software.

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

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (1)

A method of operating a base station for performing handover in a mobile communication system,
Generating handover triggering TA information indicating information about a timing advance (TA) triggered by handover to at least one of a mobile relay (MR) and a terminal of a high-speed mobile station;
Receiving at least one of a sounding reference signal (SRS), a physical uplink control channel (PUCCH), and a physical uplink shared channel (PUSCH) from at least one of the MR and the terminal of the high-speed mobile station;
Generating TA information to be transmitted to an MR or a terminal of the fast moving object using at least one reception time information of the received SRS, PUCCH, and PUSCH;
Determining whether handover is necessary based on the TA of the high-speed mobile station or the TA to be transmitted to the terminal and the handover triggering TA information; And
And transmitting a handover trigger message to at least one of a target base station and an MR or a terminal of the fast moving object when a handover is required,
Wherein the base station comprises at least one unidirectional radio resource head (RRH) and a baseband unit (BBU).

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