KR20180093198A - Method and vehicular equipment for handover of vehicular equipment of high-speed train - Google Patents

Abstract

The present invention provides a vehicle terminal included in a high speed moving body which performs handover and a handover method. The handover method comprises the following steps of: measuring a reception intensity of a reference signal individually received from a main antenna and an auxiliary antenna of a handover radio unit (H-RU) connected to a serving digital unit (DU), and reporting the measured result to the serving DU; and searching an RU of a target DU and performing handover, when the reception intensity of the reference signal received from the auxiliary antenna is larger than a predetermined threshold value.

Description

TECHNICAL FIELD [0001] The present invention relates to a handover method of a vehicle terminal of a high-speed mobile body,

The present invention relates to a handover method of a vehicle terminal included in a high-speed mobile body and a vehicle terminal.

In a mobile wireless backhaul network for a high-speed train (HST) on which many users of a cellular network are boarding, a relay or vehicular equipment installed on a high- , VE) function as a single terminal and transmit / receive signals to / from the base station. Also, a technique such as Wi-Fi or femto-cell may be used to service data received from a mobile wireless backhaul network to a user terminal in a high-speed train. VE has an advantage that the radio wave received from the outside of the high-speed train can overcome the propagation loss generated in the process of passing through the outer wall of the high-speed train. In addition, since the VE of the high-speed train carries out the group handover at the cell boundary, the signaling overhead that occurs when a large number of user terminals in the high-speed train independently perform the handover can be alleviated. In addition, VE of a high-speed train is relatively easy to implement because it does not have implementation-level limitations (miniaturization of hardware, etc.) unlike general user equipment (UE). In addition, the UE can receive service through the VE using a conventional commercial technology such as a Wi-Fi network or a femtocell, so there is no need to upgrade the UE for high-speed train communication.

In various wireless communication systems including cellular mobile communication systems, beamforming (BF) technology is introduced to improve the performance of a wireless link, and beamforming transmission is also considered in a mobile wireless backhaul system for a high-speed mobile station such as a high-speed train . The 3GPP RAN standardization conference has decided to include HST scenarios as one of the deployment scenarios of 5G NR (new radio), and HST scenarios utilizing sub-6GHz and 30GHz bands are under study. In addition, in the LTE / WiBro-based high-speed train communication implemented in various countries such as China and Taiwan, the network configuration of the HST scenario discussed in the 3GPP standardization conference and the beam-forming based single frequency network single frequency network (SFN). Because non-SFN systems based on SFN can be applied, handover can occur very frequently and handover performance can be severely hindered because high-speed trains traveling around the world can be operated at a speed of 400 km / h or more Which can have a serious impact on the quality of the mobile Internet service in a high-speed mobile unit. However, SFN has the advantage of reducing the frequency of handover if it is applied to mobile wireless backhaul network for high-speed mobile objects due to the effect of coverage expansion. Also, the millimeter wave is severely undergoing path loss and propagation attenuation so that the spacing between the radio units (RU) of the base station (cell) is very narrow. Therefore, if millimeter waves are used in a mobile wireless backhaul network for high-speed mobile, SFN technology based on beamforming is more important. In a mobile wireless backhaul network for a high-speed mobile, a handover may not be performed between a plurality of RUs connected to one digital unit (DU), and a handover may be performed only between DUs .

When the cell is configured using the beamforming technique, the signal transmitted at the RU of the serving base station (or DU) and the RU of the target base station (or DU) may be received at VE as in FIG. 1 . 1 (a) (scenario 1) is a graph showing the reception intensity of a signal when a high-speed mobile equipped with VE moves toward a serving base station, and FIG. 1 (b) And a receiving intensity of a signal when the high-speed mobile unit moves away from the serving base station. The intensity of the signal received from the serving RU in communication with VE in the FIG. 1 (a) and the target RU next to the serving RU on the path of VE gradually increases as the distance between VE and RU approaches , Then the VE rapidly drops over the serving RU and the communication link with the serving RU is broken. In FIG. 1 (b), which shows the reception strength of VE moving in the opposite direction to that of FIG. 1 (a), VE can generate a communication link with the target RU over the target RU, And after receiving the signal from the serving RU and the target RU.

That is, since VE communicates through the main lobe of the transmission beam of the base station RU and the reception beam of the VE, the VE receives signals with strong intensity in most areas, but in the vicinity of the RU, the side lobes / The intensity of the received signal is rapidly attenuated by the side lobe / back lobe. Therefore, handover from the serving BS to the target BS can not be performed smoothly in the vicinity of the RU. If the handover is not performed smoothly, it may lead to serious link loss and may also have a fatal impact on the quality of the mobile Internet service in the high-speed mobile unit.

One embodiment provides a handover method of a vehicle terminal included in a high-speed mobile terminal.

Another embodiment provides a vehicle terminal included in a high-speed mobile body performing handover.

According to one embodiment, a handover method of a vehicle terminal included in a high-speed mobile body is provided. The handover method includes measuring a reception strength of a reference signal received from a main antenna and an auxiliary antenna of an H-RU connected to the serving DU, reporting the measurement result to the serving DU, And if the received strength is greater than a predetermined threshold, searching the RU of the target DU and performing a handover.

The handover method may further include receiving resource allocation information from the main antenna so that the vehicle terminal can receive the reference signal from the auxiliary antenna after starting communication with the H-RU.

The step of receiving the resource allocation information in the handover method may include receiving the resource allocation information from the main antenna when the time difference between the vehicle terminal and the H-RU becomes smaller than a preset threshold value.

The step of receiving the resource allocation information in the handover method comprises the steps of: measuring the position of the vehicle terminal; determining a distance between the vehicle terminal and the H-RU determined based on the position of the vehicle terminal and the position of the H- And receiving the resource allocation information from the main antenna if the threshold is less than the threshold.

If the reference signal is not received from the auxiliary antenna or the strength of the reference signal received from the auxiliary antenna is less than a predetermined threshold value, the reception intensity of the reference signal received from the auxiliary antenna in the handover method is measured. To request amplification of the transmit power of the auxiliary antenna.

According to another embodiment, a handover method of a vehicle terminal included in a high-speed mobile body is provided. The handover method comprises the steps of: searching for an H-RU of a target DU during communication with an S-RU connected to a serving DU; detecting an H-RU to enable reception of a pilot signal from the H- RU from the serving DU, if the H-RU is not detected, informing the serving DU of the detection failure of the H-RU, and transmitting the downlink synchronization signal amplified by the H-RU to the H- RU, and measuring the strength of the signal received from the S-RU and the strength of the signal received from the auxiliary antenna of the H-RU, reporting the measurement result to the serving DU, and performing the handover can do.

The step of searching for the H-RU in the handover method may include searching for the H-RU when the time difference T between the vehicle terminal and the S-RU becomes greater than a preset threshold value.

Wherein the step of searching for the H-RU in the handover method comprises the steps of: measuring a position of the vehicle terminal; and determining a distance between the vehicle terminal and the H-RU determined based on the position of the vehicle terminal and the position of the H- Lt; RTI ID = 0.0 > H-RU < / RTI >

According to another embodiment, a vehicle terminal included in a high-speed mobile body is provided. The vehicle terminal includes a processor, a memory, and a wireless communication unit, and the processor executes a program stored in the memory to measure the reception strength of the reference signal received from the main antenna and the auxiliary antenna of the H-RU connected to the serving DU And reporting the measurement result to the serving DU. If the reception strength of the reference signal received from the auxiliary antenna is greater than a predetermined threshold value, the RU of the target DU is searched and a handover is performed.

The processor at the vehicle terminal may further execute the program and after receiving the resource allocation information from the main antenna so that the vehicle terminal can receive the reference signal from the auxiliary antenna after starting communication with the H-RU.

When performing the step of receiving the resource allocation information, the processor at the vehicle terminal can perform the step of receiving the resource allocation information from the main antenna when the time difference between the vehicle terminal and the H-RU becomes smaller than a preset threshold value .

The processor at the vehicle terminal, when performing the step of receiving the resource allocation information, comprises the steps of: measuring the position of the vehicle terminal; and determining a position between the vehicle terminal and the H-RU determined based on the position of the vehicle terminal and the position of the H- And if the distance is less than a predetermined threshold value, receiving the resource allocation information from the main antenna.

The receiving terminal measures the reception strength of the reference signal received from the auxiliary antenna at the vehicle terminal. If the reference signal is not received from the auxiliary antenna or the strength of the reference signal received from the auxiliary antenna is smaller than a predetermined threshold value, And requesting amplification of the transmit power of the auxiliary antenna.

If the strength of the serving RU signal decreases sharply in the vicinity of the serving RU, the VE can perform the handover to the target DU with the help of the auxiliary antenna included in the serving RU, If there is a difficulty in searching, the VE can perform handover to the target DU with the help of the auxiliary antenna included in the target DU.

1 is a graph showing the intensity of a signal received from an RU of each base station in VE.
2 is a simplified diagram illustrating a mobile wireless backhaul network for a high-speed mobile according to one embodiment.
3 is a diagram schematically illustrating a handover method of a mobile wireless backhaul network for a high-speed mobile terminal according to an exemplary embodiment of the present invention.
FIG. 4 is a graph illustrating the intensity of a signal received by each antenna included in an RU according to an exemplary embodiment of the present invention.
5 is a flowchart illustrating a handover method using an auxiliary antenna according to an embodiment.
6 is a flowchart illustrating a handover method using an auxiliary antenna according to another embodiment.
7 is a block diagram illustrating a wireless communication system according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present disclosure can be embodied in various different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention in the drawings, parts not related to the description are omitted, and like reference numerals are given to similar parts throughout the specification.

Throughout the specification, a terminal is referred to as a mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS), a high reliability mobile station A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE), a machine type communication device MTC device and the like and may include all or some functions of MT, MS, AMS, HR-MS, SS, PSS, AT, UE,

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, a high reliability relay station (HR) (BS), a home Node B (HNB), a home eNodeB (HeNB), a pico BS, a macro BS, a micro BS ), Etc., and all or all of ABS, Node B, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR- And may include negative functionality.

2 is a simplified diagram illustrating a mobile wireless backhaul network for a high-speed mobile according to one embodiment.

The high-speed moving object may be a train, a subway train, a high-speed train, and the following description will be made by taking a high-speed train as an example. The base station includes DU and a plurality of RUs. DU controls a plurality of RUs, and SFNs can be configured, and each RU can perform fixed beamforming. Since DU constitutes SFN, handover does not occur between RUs connected to one DU, and VE can select one or more RUs to communicate with DU. VE performs handover only when moving to another DU. In scenario 1, during the handover of the VE, the strength of the signal received from the serving RU is abruptly attenuated and the communication link is disconnected, so that the probability of the VE to fail the handover increases. In Scenario 2, the VE can not receive a signal from the target RU before starting the handover, so it is difficult to perform cell search for handover.

The VE of the high-speed mobile unit receives the data of the mobile wireless backhaul network from the RU of the base station and can transmit the data to UEs in the high-speed mobile unit using a technology such as Wi-Fi or a small cell. In the present description, the link between the RU of the base station and the VE of the high-speed mobile unit will be described.

3 is a diagram schematically illustrating a handover method of a mobile wireless backhaul network for a high-speed mobile terminal according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the VE of the high-speed mobile unit and the RU of the base station include an assisted antenna (A-ANT) for forming a beam having a large width. In this case, since the handover occurs at the boundary between DU _d and DU _{d + 1} , the RU including the auxiliary antenna among the plurality of RUs connected to DU _d is the RU closest to the last RU of DU _d , that is, DU _{d +1} . This is because in the SFN, handover does not occur between a plurality of RUs connected to one DU. For example, when 10 RUs are connected to one DU, one antenna is needed per 5 km when the coverage of one RU is 500 m. VE of the high-speed mobile unit includes the auxiliary antenna, but VE may not include the auxiliary antenna if another antenna included in the VE can form an omni-directional beam.

Pilot signals orthogonal to each other (in frequency, time, and code dimension) can be assigned to the auxiliary antennas included in the RU as in the other antennas of the RU. The maximum coverage of the auxiliary antenna can be determined by the area of the side lobe / back lobe of the main antenna of the RU and the speed of the high-speed mobile so as to sufficiently form the handover area. At this time, the auxiliary antenna can cover from the time before the section where the signal strength starts to decrease sharply due to the back lobe to the point where the handover is finished.

FIG. 4 is a graph illustrating the intensity of a signal received by each antenna included in an RU according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the intensity of the signal received from the main antenna (M-ANT) of the m-th RU in a range of 800 m to 1,000 m of the high-speed mobile station (handover area) decreases sharply. The strength of the signal received from the m < th > RU auxiliary antenna in the handover region is largest in the center of the handover region. At this time, the m-th RU of the d-th DU is the handover RU (H-RU) of the first VE. Therefore, the first VE can perform the handover with the help of the auxiliary antenna included in the m-th RU.

5 is a flowchart illustrating a handover method using an auxiliary antenna according to an embodiment.

First, the VE in the scenario 1 sequentially communicates with a plurality of RUs connected to the serving DU (S110). When the VE of the high-speed mobile unit starts communication with the H-RU, the base station informs that the RU that started communication with the VE through the downlink is the H-RU (S120).

If VE and H-RU are sufficiently close to each other, then VE is a reference to the A-ANT via the M-ANT of the H-RU so that VE can receive the reference signal of the A-ANT included in the H- And receives resource allocation information on the signal (S130). At this time, the distance between VE and H-RU can be determined through a comparison between a time difference T between VE and H-RU and a predetermined threshold value? ₁ . For example, when the time difference T between VE and H-RU becomes smaller than a preset threshold value (T? ₁ ), it is determined that VE and H-RU are sufficiently close to each other. Or the distance between the VE and the RU can be measured through the position measurement. In this case, when the position of the VE is measured using GPS technology or the like, and the distance between the VE and the H-RU determined based on the position of the VE and the position of the H-RU becomes smaller than the preset threshold value (d _threshold ) d _{H - RU} d _threshold ), a resource allocation for receiving a reference signal of VE can be performed.

Then, VE continuously measures the strength of the reference signal received from the M-ANT and the A-ANT of the H-RU (S140) and reports the measurement result to the serving DU (S150). If the A-ANT does not receive the reference signal of the A-ANT or if the reception intensity? _A is smaller than a predetermined threshold value? _{A, min} (? _A ?? _{A, min} ) It may request the serving DU to amplify the power (S160). The A-ANT receiving the power amplification request can amplify the transmission power step by step (S170). If the transmission power of the A-ANT is set to the maximum from the beginning, the interference increases. Therefore, in order to minimize the influence on the data transmitted in the section excluding the handover region, the A- .

The base station determines the communication mode between VE, M-ANT and A-ANT based on the measurement result of VE (S180). If the signal strength of the A-ANT measured at the VE is greater than a predetermined threshold value (γ ₁ ) for a predetermined time (T ₁ ) (γ _A ≥γ ₁ ), the base station transmits VE Performs communication, and determines that VE enters the handover area. At this time, the VE can acquire the diversity gain by receiving the same data through the M-ANT and the A-ANT, or by receiving different data.

VE searches the RU of the target DU (DU _{d + 1} ) and performs the handover (S190). Then, DU stops the data transmission of the M-ANT if the signal intensity ( _M ) of the M-ANT reported by the VE becomes smaller than a predetermined threshold value ( _{M, min} ).

Thereafter, when a handover failure occurs during the handover, the base station and the VE increase the power of the auxiliary antenna step by step and retry the handover. The maximum power of the auxiliary antenna can be set during the design process of the system. If the handover is unsuccessful even if the handover is retried a predetermined number of times or the handover failure occurs even if the transmission power of the auxiliary antenna is the maximum power, the VE attempts initial connection to the target DU.

As described above, in Scenario 1, the intensity of the signal of the serving RU is rapidly reduced in the vicinity of the serving RU, so that the VE can perform the handover to the target DU with the help of the auxiliary antenna included in the serving RU.

6 is a flowchart illustrating a handover method using an auxiliary antenna according to another embodiment.

First, when the VE in scenario 2 continues to communicate with the serving RU (serving RU, S-RU) of the serving DU, it is determined that VE is close enough to the RU of the target DU, Handover RU (H-RU)) (S210). The distance between the VE and the RU of the target DU can be determined through comparison of VE and the time difference T of the serving RU and a preset threshold value? ₂ . For example, if the time difference T between VE and the serving RU is greater than a predetermined threshold value (T > 隆₂ ), it can be determined that VE is sufficiently close to the RU of the target DU. Alternatively, the distance between VE and RU can be measured through position measurement. In this case, the position of the VE is measured, and if the distance between the VE and the H-RU determined based on the position of the VE and the position of the H-RU becomes smaller than the preset threshold value d _threshold (d _{H - RU} ≤ d _threshold ), VE can start searching for the H-RU. VE can detect the H-RU by searching for the downlink synchronization signal of the H-RU.

If the VE succeeds in detecting the H-RU (S220), the S-RU transmits resource allocation information on the resource to the VE so that the VE can receive the pilot signal from the A-ANT of the H-RU (S230) . If the VE fails to detect the H-RU, the VE notifies the serving DU via the S-RU (S240), and the serving DU requests the target DU to amplify the power of the A-ANT by the H-RU (S250). Thereafter, the H-RU step up the transmission power of the auxiliary antenna to transmit the downlink synchronization signal (S260).

Then, VE measures the strength of the signal received from the S-RU and the strength of the signal received from the A-ANT of the H-RU and reports the measurement result to the serving DU (S270). The measurement results of the VE can be shared between the serving DU and the target DU. The serving DU and the target DU perform a handover based on the measurement result report of the VE (S280). At this time, the handover can follow the handover procedure of the cellular system such as LTE. After the VE completes the handover to the H-RU, the VE measures the received strength of the reference signal received from the A-ANT and the M-ANT of the H-RU and reports the measurement result to the target DU. The base station determines the communication method between A-ANT and M-ANT and VE based on the measurement result of VE.

As described above, in the scenario 2, since the VE has difficulty in searching the RU of the target DU for the handover, the VE can perform the handover to the target DU with the help of the auxiliary antenna included in the target DU.

7 is a block diagram illustrating a wireless communication system according to an embodiment.

Referring to FIG. 7, a wireless communication system according to an embodiment includes a base station 710 and a terminal 720.

The base station 710 includes a processor 711, a memory 712, and a radio frequency unit (RF unit) 713. The memory 712 may be coupled to the processor 711 to store various information for driving the processor 711 or at least one program to be executed by the processor 711. [ The wireless communication unit 713 may be connected to the processor 711 to transmit and receive wireless signals. The processor 711 may implement the functions, processes, or methods proposed in the embodiments of the present disclosure. At this time, in the wireless communication system according to the embodiment of the present invention, the wireless interface protocol layer can be implemented by the processor 711. The operation of base station 710 in accordance with one embodiment may be implemented by processor 711. [

The terminal 720 includes a processor 721, a memory 722, and a wireless communication unit 723. [ The memory 722 may be coupled to the processor 721 to store various information for driving the processor 721 or at least one program to be executed by the processor 721. [ The wireless communication unit 723 is connected to the processor 721 to transmit and receive a wireless signal. The processor 721 may implement the functions, steps, or methods suggested in the embodiments of the present disclosure. At this time, in the wireless communication system according to an embodiment of the present invention, the wireless interface protocol layer can be implemented by the processor 721. [ The operation of the terminal 720 according to one embodiment may be implemented by the processor 721. [

In an embodiment of the present disclosure, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various means already known. The memory may be any type of volatile or nonvolatile storage medium, e.g., the memory may include read-only memory (ROM) or random access memory (RAM).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (13)

A handover method of a vehicle terminal included in a high-
Measures the reception strength of the reference signal received from the main antenna and the auxiliary antenna of the handover radio unit (H-RU) connected to the serving digital unit (DU), and transmits the measurement result to the serving DU Reporting step,
If the reception strength of the reference signal received from the auxiliary antenna is greater than a predetermined threshold value, searching the RU of the target DU and performing a handover
/ RTI > The method of claim 1,
Receiving the resource allocation information from the main antenna so that the vehicle terminal can receive the reference signal from the auxiliary antenna after starting communication with the H-RU;
The handover method further comprising: 3. The method of claim 2,
Wherein the step of receiving the resource allocation information comprises:
Receiving the resource allocation information from the main antenna when a time difference between the vehicle terminal and the H-RU becomes smaller than a preset threshold value
And a handover method. 3. The method of claim 2,
Wherein the step of receiving the resource allocation information comprises:
Measuring a position of the vehicle terminal, and
Receiving the resource allocation information from the main antenna if the distance between the vehicle terminal and the H-RU determined based on the position of the vehicle terminal and the position of the H-RU becomes smaller than a preset threshold value
And a handover method. The method of claim 1,
Measuring a reception intensity of the reference signal received from the auxiliary antenna means that if the reference signal is not received from the auxiliary antenna or the strength of the reference signal received from the auxiliary antenna is less than a predetermined threshold value, And requesting the serving DU to amplify the transmit power of the auxiliary antenna. A handover method of a vehicle terminal included in a high-
Searching for a handover RU (H-RU) of a target DU during communication with a serving radio unit (S-RU) connected to a serving digital unit (DU)
Receiving, from the serving DU, resource allocation information on a resource that is capable of receiving a pilot signal from the H-RU's auxiliary antenna upon detecting the H-RU;
Notifying the serving DU of the detection failure of the H-RU if the H-RU is not detected, and receiving a downlink synchronization signal amplified by the H-RU from the H-RU;
Measuring an intensity of a signal received from the S-RU and an intensity of a signal received from the auxiliary antenna of the H-RU, reporting a measurement result to the serving DU, and performing a handover
/ RTI > The method of claim 1,
The step of searching for the H-RU comprises:
When the time difference T between the vehicle terminal and the S-RU becomes greater than a predetermined threshold value, searching for the H-RU
And a handover method. The method of claim 1,
The step of searching for the H-RU comprises:
Measuring a position of the vehicle terminal, and
When the distance between the vehicle terminal and the H-RU determined based on the position of the vehicle terminal and the position of the H-RU becomes smaller than a predetermined threshold value, searching the H-RU
And a handover method. As a vehicle terminal included in a high-speed mobile body,
A processor, a memory, and a wireless communication unit,
Wherein the processor executes a program stored in the memory,
Measures the reception strength of the reference signal received from the main antenna and the auxiliary antenna of the handover radio unit (H-RU) connected to the serving digital unit (DU), and transmits the measurement result to the serving DU Reporting step,
If the reception strength of the reference signal received from the auxiliary antenna is greater than a predetermined threshold value, searching the RU of the target DU and performing a handover
. The method of claim 9,
The processor executes the program,
Receiving the resource allocation information from the main antenna so that the vehicle terminal can receive the reference signal from the auxiliary antenna after starting communication with the H-RU;
To the vehicle terminal. 11. The method of claim 10,
Wherein the processor, when performing the step of receiving the resource allocation information,
Receiving the resource allocation information from the main antenna when a time difference between the vehicle terminal and the H-RU becomes smaller than a preset threshold value
To the vehicle terminal. 11. The method of claim 10,
Wherein the processor, when performing the step of receiving the resource allocation information,
Measuring a position of the vehicle terminal, and
Receiving the resource allocation information from the main antenna if the distance between the vehicle terminal and the H-RU determined based on the position of the vehicle terminal and the position of the H-RU becomes smaller than a preset threshold value
To the vehicle terminal. The method of claim 9,
Measuring a reception intensity of the reference signal received from the auxiliary antenna means that if the reference signal is not received from the auxiliary antenna or the strength of the reference signal received from the auxiliary antenna is less than a predetermined threshold value, And requesting the serving DU to amplify the transmit power of the auxiliary antenna.

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