WO2023136479A1

WO2023136479A1 - Apparatus and method for calculating delay time due to handover in mobile communication system

Info

Publication number: WO2023136479A1
Application number: PCT/KR2022/020083
Authority: WO
Inventors: 이규범; 성민우; 샤하쉬마헤쉬
Original assignee: 삼성전자주식회사
Priority date: 2022-01-12
Filing date: 2022-12-12
Publication date: 2023-07-20
Also published as: KR20230108937A

Abstract

In order to calculate a total delay time having occurred on a user-plane, a base station in a wireless communication system, according to one embodiment, comprises: a communication module for communicating with a source base station controlling a user terminal and a source cell; a memory in which computer-executable instructions are stored; and a processor, which accesses the memory so as to execute instructions, wherein the instructions can be configured to: receive information about pre-handover delay time from the source base station according to the transmission of a request to the source base station if the terminal accessing a base station, which is a target base station for controlling a target cell, performs handover from the source cell to the target cell; obtain information about delay time due to handover on the basis of the number of buffered packets forwarded from the source base station and information about packets received from the terminal; obtain information about post-handover delay time occurring after the access of the terminal; and calculate the total delay time having occurred on the user-plane, on the basis of the information about pre-handover delay time, the information about delay time due to the handover, and the information about post-handover delay time. Other various embodiments are possible.

Description

Apparatus and method for calculating delay time due to handover in mobile communication system

Various embodiments of the present disclosure relate to an apparatus and operation method for calculating handover delay time in a mobile communication system, and specifically, data interruption time caused by handover in a user-plane. It's about how to count.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system to meet the growing demand for wireless data traffic after the commercialization of the 4G communication system. For this reason, the 5G communication system or pre-5G communication system is known as a system after a 4G network (Beyond 4G Network) communication system or an LTE system (Post LTE).

As technology for providing services through packet-based data networks has developed, services through packet networks such as the Internet have become common. ) is provided. In addition, real-time interaction (real-time interaction) call and video call services may be supported based on 5G communication technology. In the case of a voice service provided based on a packet network, data is converted into digital packets, which are the minimum unit of data transmission, through the Internet network having an IP address and transmitted. As delays occur, service quality may deteriorate.

Hand-over or handoff is when a terminal in a state of receiving data from a base station leaves the cell boundary of the base station and moves to a service area of a neighboring base station, and the terminal moves to a new data channel of a neighboring base station. refers to a function that automatically tunes to and maintains a continuous communication state. A base station that provides a channel through which the terminal communicates before handover is called a source base station that controls a source cell, and a base station that provides a channel through which the terminal communicates after completion of handover is referred to as a target cell ( It may be referred to as a target base station that controls a target cell. The UE performs handover while communicating through the source cell, and communicates through the target cell after the handover.

When handover occurs, data forwarding occurs from the source base station to the target base station, and after the terminal accesses the target base station, the target base station can deliver the forwarded data to the terminal. In such a handover situation, time is required for message transmission and reception and interpretation until the data forwarded to the target base station is transmitted to the terminal, and the provision of data to the terminal is stopped during that time, which may reduce user convenience.

The usage of real-time applications such as real-time games and video conferencing is increasing. When a handover occurs due to the movement of a terminal using a real-time application, the delay time (or interruption time) caused by the handover deteriorates the quality of service (QoS) experienced by the user. can make it

However, the technical challenges are not limited to the above-described technical challenges, and other technical challenges may exist.

A base station of a wireless communication system according to an embodiment includes a communication module for communicating with a source base station that controls a user terminal and a source cell; a memory in which computer-executable instructions are stored; and a processor that accesses the memory and executes the instructions, wherein the instructions cause a terminal accessing the base station, wherein the base station is a target base station that controls a target cell, to control the source cell. In case of a terminal performing handover to the target cell, as a request is transmitted to the source base station, pre-handover delay time information is received from the source base station, and forwarding from the source base station Delay time information due to the handover is obtained based on the number of buffered packets received and packet information received from the terminal, and a post-handover delay occurring after the terminal attaches. Post-handover delay time information is acquired, and the total delay generated in the user-plane is based on the pre-handover delay time information, the delay time due to the handover, and the post-handover delay time information. It can be configured to count time.

According to an embodiment, the commands may include traffic information, mobility information of the UE, the source cell information, the target cell information, and neighbor cell information when the total delay time exceeds the threshold value. It may be further configured to generate feedback information based on at least one and transmit the feedback information to the source base station or another base station.

According to an embodiment, the packet information may be classified according to protocol layer and quality of service (QoS).

According to an embodiment, the packet information includes information on the last partial packet transmitted from the source base station to the terminal; and information on some initial packets transmitted from the terminal accessing the target base station to the target base station.

According to an embodiment, the instructions are configured to determine whether the terminal performs handover from the source cell to the target cell based on a handover request received from the source base station. can

According to an embodiment, the pre-handover delay time information includes transmitting a handover command from the source base station to the terminal from the point when the source base station transmits a packet to the terminal but does not receive an ACK. It may include time information up to the point in time.

According to an embodiment, the packet information includes the packet type information and interval time information according to the packet type, and the instructions include the number of buffered packets and the interval time information. It may be configured to obtain delay time information due to the handover by multiplying by .

According to an embodiment, the instructions may be configured to obtain interval time information of the packet based on a real-time transport protocol (RTP) payload type of the packet.

According to an embodiment, the post-handover delay time information includes time information from a time when the target base station receives handover complete from the terminal to a time when the serving cell of the terminal is changed to the target cell. can include

According to an embodiment, each of the target base station and the source base station is either a long term evolution (LTE) base station or a new radio (NR) base station, and the target base station and the source base station control different cell groups and the Signals can be transmitted and received simultaneously with the user terminal.

In a method of operating a base station in a wireless communication system according to an embodiment, a terminal accessing the base station, wherein the base station is a target base station that controls a target cell, performs handover from a source cell to the target cell. If the UE performs, receiving pre-handover delay time information from the source base station as a request is transmitted to the source base station controlling the source cell; obtaining delay time information due to the handover based on the number of buffered packets forwarded from the source base station and packet information received from the terminal; obtaining post-handover delay time information occurring after the terminal is attached; and calculating a total delay time generated in a user-plane based on the pre-handover delay time information, the handover-induced delay time information, and the post-handover delay time information.

According to an embodiment, the method may select among traffic information, mobility information of the UE, the source cell information, the target cell information, and neighbor cell information when the total delay time exceeds a threshold value. An operation of generating feedback information based on at least one of them; and transmitting the feedback information to the source base station or another base station.

According to an embodiment, the packet information includes the packet type information and interval time information according to the packet type, and the method includes the number of buffered packets and the interval time information. It may include an operation of obtaining delay time information due to the handover by multiplying by .

According to an embodiment, the method may include obtaining interval time information of the packet based on a real-time transport protocol (RTP) payload type of the packet.

According to an embodiment, in a method of operating a base station in a wireless communication system, a terminal connected to the base station, wherein the base station is a source base station that controls a source cell, moves from the source cell to a target cell. When handover is performed, a pre-handover delay time from the time when a packet is transmitted to the terminal but an ACK is not received to the time when a handover command is transmitted to the terminal ) obtaining information; forwarding a buffered packet due to the handover to the target base station; delay time information due to the handover, from the target base station; And receiving post-handover delay time information from the time when the target base station receives handover complete from the terminal to the time when the serving cell of the terminal is changed to the target cell. movement; and calculating a total delay time generated in a user-plane based on the pre-handover delay time information, the handover-induced delay time information, and the post-handover delay time information.

According to various embodiments, an apparatus for calculating a total delay time due to handover in a user plane may be provided.

According to various embodiments, an apparatus for analyzing a cause of delay due to handover and providing feedback may be provided.

In addition to this, various effects identified directly or indirectly through this document may be provided.

1 is a block diagram of a base station in a wireless communication system, according to various embodiments.

2A and 2B are diagrams for explaining handover in which a serving cell of a user equipment is changed from a source cell to a target cell.

3 is a diagram illustrating a handover operation in an LTE system according to an embodiment.

4 is a diagram illustrating protocols of entities involved in transmitting and receiving voice packets.

5 is a diagram for explaining a method of collecting packet information through packet mirroring according to an embodiment.

6 is a diagram illustrating a configuration of an RTP packet according to an embodiment.

7 is a flowchart illustrating an operation of a target base station according to an embodiment.

8 is a flowchart for explaining a feedback operation of a base station according to an embodiment.

9 is a flowchart illustrating an operation of obtaining delay time information due to handover according to an embodiment.

10 is a flowchart illustrating an operation of a source base station according to an embodiment.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, the same reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted. The accompanying drawings are not intended to limit the present disclosure to specific embodiments, but are to be understood as including various modifications, equivalents, and/or alternatives of the embodiments of the present disclosure.

< Base station in wireless communication system >

1 is a block diagram of a base station 101 in a wireless communication system 100, according to various embodiments.

Referring to FIG. 1, a base station 101 according to an embodiment includes a communication module 190 for communicating with a user terminal 200 and a collaborative base station 102, computer-executable instructions (computer- It may include a memory 130 in which executable instructions are stored, and a processor 120 that accesses the memory 130 and executes instructions.

The base station 101 or the cooperative base station 102 may be a wireless communication device for communicating with the user terminal 200 in the same or different frequency bands. According to an embodiment, the base station 101 and the base station 102 may be a long term evolution (LTE) base station communicating with the user terminal 200 in a low frequency band or a new radio (NR) base station communicating in a high frequency band. Hereinafter, the handover process and the like will be described based on the LTE communication system, but it is not limited thereto, and may be applied to 5G or NR communication systems.

The base station 101 and the cooperative base station 102 control different cell groups and can simultaneously transmit and receive signals with the user equipment 200 . The cooperative base station 102 illustrated in FIG. 1 may correspond at least in part to the configuration of the base station 101 . According to an embodiment, the base station 101 is a target base station that controls the target cell, the base station 102 is a source base station that controls the source cell, and the serving cell of the terminal 200 is changed from the source cell to the target cell. overruns can occur. The handover process will be described in detail with reference to FIGS. 2A, 2B and 3 .

According to one embodiment, the communication module 190 may process functions or operations for transmitting and receiving signals through a wireless channel, and may be implemented as hardware or software, or a combination of hardware and software. For example, the communication module 190 may perform a conversion function between a baseband signal and a bit string according to the physical layer standard of the system 100 . For example, the communication module 190 may generate complex symbols by encoding and modulating a transmission bit stream during data transmission. In addition, the communication module 190 may restore a received bit stream by demodulating and decoding a baseband signal upon receiving data.

According to an embodiment, the communication module 190 up-converts a baseband signal into a radio frequency (RF) band signal, transmits the signal through an antenna, and down-converts an RF band signal received through the antenna into a baseband signal. can To this end, the communication module 190 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. The communication module 190 may include a plurality of transmit/receive paths.

According to an embodiment, the communication module 190 may include at least one antenna array composed of a plurality of antenna elements. For example, the communication module may further include a Field Programmable Gate Array (FPGA). An FPGA may be a semiconductor device that includes designable logic devices and programmable internal lines. Capable logic elements can be programmed to duplicate logic gates such as AND, OR, XOR, NOT, and more complex decoder functions. An FPGA may further include flip-flops or memory.

According to one embodiment, the communication module 190 may be composed of a digital unit and an analog unit in terms of hardware, and the analog unit has a plurality of sub-units according to operating power, operating frequency, etc. It can be composed of (sub-units). The digital unit may be implemented with at least one processor (eg, a digital signal processor (DSP)).

According to an embodiment, all or part of the communication module 190 may be referred to as a 'transmitter', 'receiver', or 'transceiver'. Also, in the following description, transmission and reception performed through a radio channel are used to mean that the above-described processing is performed by the communication module 190.

According to an embodiment, the communication module 190 may further include a backhaul communication unit, and the backhaul communication unit may provide an interface for communicating with other nodes in the network. For example, the backhaul communication unit converts a bit string transmitted from the base station 101 to another node (eg, another access node, another base station 102, a higher node, a core network, etc.) into a physical signal, and receives it from the other node. A physical signal can be converted into a bit string.

According to an embodiment, the memory 130 may store data such as a basic program for operation of the base station 101, an application program, and setting information. The memory 130 may include volatile memory, non-volatile memory, or a combination of volatile and non-volatile memories. The memory 130 may provide stored data according to a request of the processor 120 . According to an embodiment, a program for calculating the total delay time generated in the user plane based on pre-handover delay time information, handover delay time information, and post-handover delay time information is stored in the memory 130 as software. It can be.

According to an embodiment, the processor 120 may control overall operations of the base station 101 . For example, the processor 120 may transmit and receive signals through the communication module 190 or through the backhaul communication unit, write data to the memory 130, and write the data (eg, : instructions that can be executed by a computer). The processor 120 may perform protocol stack functions required by communication standards. Depending on the implementation example, the protocol stack may be included in the communication module 190 . Protocols of entities related to transmission and reception of packets according to an embodiment will be described in detail with reference to FIG. 4 . A configuration of an RTP packet related to a real-time transport protocol (RTP) will be described in detail with reference to FIG. 6 .

According to an embodiment, the processor 120 may calculate the total delay time generated in the user plane based on pre-handover delay time information, handover delay time information, and post-handover delay time information. Detailed operations of the processor 120 according to various embodiments will be described with reference to FIGS. 7 to 10 .

Referring to FIG. 2A, when a handover (HO) in which a serving cell of a terminal 200 is changed from a source cell 212 to a target cell 211 occurs An example is shown. A base station controlling the source cell 212 may be the source base station 102 , and a base station controlling the target cell 211 may be the target base station 101 . A base station may be referred to as an evolved Node-B (or eNB), a base station, and the like.

In a cellular wireless communication system, base stations perform a handover procedure of changing a serving cell from a source cell to a target cell when a UE crosses a cell boundary and enters another cell. For example, when the terminal 200 moves from the source cell 212 to the target cell 211 as shown in FIG. 2A, the source base station 102 and the target base station 101 may perform a handover process. A handover process in a 3GPP LTE network system according to an embodiment will be described in detail with reference to FIG. 3 .

During the handover process, a delay time (or interruption time) in which the terminal 200 is not temporarily provided with data may occur. In particular, when a user uses a real-time application, QoS deterioration due to delay time may be an important problem. As shown in FIG. 2B , when the terminal 200 frequently moves across cell boundaries, service quality degradation due to handover may be further increased.

The processor 120 of the base station 101 (or base station 102) according to an embodiment determines the total delay time experienced by the user when the terminal 200 performs a handover process in a cellular wireless communication network. Calculate and generate feedback information. A specific operation of the processor 120 will be described in detail with reference to FIGS. 7 to 10 .

Referring to FIG. 3, a handover process according to an embodiment will be described. The source base station 102 may be a base station serving the terminal 200 before handover, and the target base station 101 may be a base station to which the terminal 200 newly attaches through handover.

The handover preparation step 350 may start from a time when the source base station 102 transmits a packet to the terminal 200 but does not receive an ACK. The source base station 102 may select a target base station 101 and determine handover by receiving a measurement report from the terminal 200 after not receiving an ACK for packet transmission from the terminal 200 .

The source base station 102 may determine whether to approve the handover request and transmit the handover request message to the selected target base station 101 . If, for example, the target base station 101 accepts the terminal 200 based on the QoS and load conditions of the active flow of the terminal 200, the HO performing step 360 is initiated; otherwise, Source base station 102 may not select base station 101 as a target base station.

In step 360 of performing the handover, the source base station 102 may transmit a buffer and in-transit packets to the target base station 101 and transmit a handover command to the terminal 200 . Upon receiving this, the terminal 200 may start air interface synchronization with the target base station 101 and transmit handover completion to the target base station 101 after synchronization is completed. After receiving the handover completion, the target base station 101 may start a handover completion step 370 of starting a path switching procedure with the source gateway 330 .

When path switching is performed, the target base station 101 may inform the source base station 102 of handover completion, and the source base station 102 may release resources of the terminal 200 . Referring to FIG. 3, a handover procedure is described as follows.

Phase 0: Geo-restricted offer phase

Step 1: Measurement Control Phase

Step 2: Measurement reporting step

Step 3: HO Determination Step

Step 4: Handover Request Step

Step 5: Admission Control

Step 6: Handover Request Approval Step

Step 7: HO command step

Step 8: SN Status Propagation Step

Step 9: Synchronization Step

Step 10: TA control step for UL allocation and UE

Step 11: HO Completion Steps

Step 12: Route conversion request step

Step 13: Bearer Modification Request Step

Step 14: DL Path Conversion Steps

Step 15: Bearer Modification Response Step

Step 16: Approve route switch request step

Step 17: Resource release instruction step

Step 18: Resource Release Steps

When handover occurs in a wireless cellular communication system, quality degradation may occur due to packet loss. For example, if packet loss occurs while providing an IP-based voice call service or video service, service quality may deteriorate.

According to an embodiment, when handover occurs, the source base station 102 buffers packets having a predetermined size among packets transmitted by the source base station 102 to the terminal 200 before handover, and temporarily stores them. , the buffered packet may be transmitted to the target base station 101.

According to an example, packets with the highest packet loss probability during handover may be the last 1 or 2 packets transmitted by the source base station 102 to the terminal 200 performing the handover. The source base station 102 may buffer preset packets of downlink traffic (eg, the last one or two packets transmitted to a specific terminal performing handover). For example, the PDCP of the source base station 102 may buffer a preset packet of downlink traffic.

When handover between base stations occurs, the source base station 102 may forward buffered packets to the target base station. The PDCP of the base station 102 may transmit the latest buffered packet to the target base station 101 before the Path Switch Request operation.

According to an embodiment, the target base station 101 receiving the buffered packet may transmit the received packet to the terminal 200 accessing the target base station 101 through handover. The terminal 200 may decode and use a received packet if it is a new packet that has not been previously received as a lost packet without decoding it if the received packet is already received.

4 is a diagram illustrating protocols of entities related to transmission and reception of packets.

Referring to FIG. 4 , packets may be transmitted and received between a terminal 200 and

base stations

101 and 102 through air communication. Packets may be transmitted and received through layer 1 and layer 2 protocols among the protocols of the terminal 200 and the

base stations

101 and 102, respectively. For example, layer 1 and layer 2 protocols may include packet data convergence protocol (PDCP), radio link control (RLC), medium access control (MAC), and a physical layer (PHY).

Packets obtained through layer 1 and 2 level protocols are transmitted and received between the

base stations

101 and 102 and the core network entity 450 through a backhaul, and in the core network entity 450, the application level protocol Collecting and analyzing packets can be performed through. In the core network entity 450, the service quality cannot be measured for a path in which packets are transmitted and received in the layer 1 and 2 level protocol between the terminal 200 and the

base stations

101 and 102, and based on the application level protocol Service quality can be measured.

For example, an embodiment in which the terminal 200 performs real-time communication such as a call or a video call with a counterpart terminal (not shown) will be described. When an uplink voice packet transmitted to the

base stations

101 and 102 through air communication is transferred from the

base stations

101 and 102 to the core network entity 450 through the backhaul (B/H), the core end 450 ), the quality of service related to the corresponding packet can be measured by considering the quality of the protocol and backhaul at the application level. Thereafter, the corresponding packet is transferred from the core 450 to the

base stations

101 and 102 through the backhaul, and the counterpart terminal can receive the corresponding packet through wireless communication.

At this time, even if the core unit 450 measures the quality of the voice service related to the voice packet, it cannot measure problems occurring in a wireless communication situation transmitted from the base station to the counterpart terminal. For example, if handover occurs in the process of transmitting a voice packet, information on which cell is a base station (or cell) where a problem occurs cannot be obtained.

Regarding the voice packet obtained from the terminal 200, it can be confirmed that the quality of the voice service has deteriorated at the application protocol level. It is not possible to ascertain a specific reason, such as whether it is due to the cause of the communication situation. That is, on the entire path from the terminal 200 to the counterpart terminal (end-to-end), it is necessary to accurately know what caused the quality of service to deteriorate and deal with it.

Referring to FIG. 5 , a method of collecting packet information through packet mirroring in the core unit 450 is illustrated. Referring to FIG. 5, as the user terminal 200 moves from the source cell 502 to the target cell 501, the handover process described with reference to FIG. 3 by the source base station 102 and the target base station 101 this can be done The user terminal 200 may communicate with the counterpart terminal 300 through the

base stations

101 and 102 and the core network (or core network entity) 450 as described above with reference to FIG. 4 .

As described above with reference to FIG. 4, when packet information is collected based on packet mirroring in the core network entity 450, packets are generated in layer 1 and layer 2 protocols between the terminal 200 and

base stations

101 and 102. The service quality cannot be measured for the transmission/reception path, but the service quality can be measured based on the application level protocol.

For example, when packet information is collected and analyzed in the core layer 450, uplink (UL) performance of a communication network can be measured (510), but this is irrelevant to user experience, The specific cause of the uplink performance degradation is unknown. In addition, since packet information is collected at the core stage 450, downlink (DL) performance, which directly affects user experience, cannot be analyzed (520).

Also, as described above with reference to FIG. 4 , even if the quality of service related to packets is measured in the core 450 , problems related to the downlink transmitted to the counterpart terminal 300 cannot be measured. Similar to the user terminal 200, only the uplink performance of the counterpart terminal 300 can be measured based on the information collected by the core terminal 450. In addition, since packet information is collected from the core rather than the base station, it is impossible to determine which cell is the base station (or cell) where the problem occurs.

With reference to FIGS. 7 to 10 , the operation of the processor 120 of the

base stations

101 and 102 will be described in detail. The processor 120 can measure downlink problems related to user experience by collecting and analyzing packet information at the base station level, rather than collecting information at the core stage 450 as shown in FIG. The cause of the problem can be analyzed. For example, since most of the handover procedures are performed at the base station level, the base station can identify which network layer and which cell the problem occurred.

According to an embodiment, a method of measuring handover delay time based on packet information by the processor 120 will be described. When information is collected in the core unit 450 as shown in FIG. 5 , delay time due to handover can be measured by measuring a packet gap through packet mirroring. The processor 120 may collect packet information at the level of the

base stations

101 and 102 and measure a delay time due to handover.

As described with reference to FIG. 3 , the handover process may be divided into a handover preparation phase 350 , a handover execution phase 360 and a handover completion phase 370 . When packet information is collected by the processor 120 of the base station, delay time information according to each step may be obtained, and the total delay time occurring in the user-plane may be measured. Specifically, in addition to the delay time due to the handover occurring in the handover performing step 360, the processor 120 of the base station also determines the pre-handover delay time occurring to the user in the handover preparation step 350. time) information and post-handover delay time information occurring to the user in the handover completion step 370 may be obtained. The processor 120 may calculate the total delay time actually occurring to the user by summing up the pre-handover delay time information, the delay time information due to handover, and the post-handover delay time information. A specific operation of the processor 120 will be described with reference to FIGS. 7 to 10 .

Real-time transport protocol (RTP) is a standard protocol for transmitting real-time voice, video, and data over an IP network. As described with reference to FIGS. 3 to 5 , the processor 120 of the base station performs handover when performing real-time communication such as voice service and video service with the counterpart terminal (eg, the counterpart terminal 300 of FIG. 5 ). RTP packets may be transmitted and received with the performing terminal 200 and the cooperative base station (eg, if the base station is a target base station, the cooperative base station is a source base station, and if the base station is a source base station, the cooperative base station is a target base station).

Referring to FIG. 6, a configuration of an RTP packet supporting voice or video service according to an embodiment is illustrated. The RTP packet may include a sequence number, a time stamp, and the like related to transmission of the RTP packet in a header.

The processor 120 of the base station 101 according to an embodiment determines whether the packet interval time is greater than or equal to a preset range using the sequence number included in the RTP packet header, and determines the number of missing packets between packets. It is possible to check whether or not the number is greater than or equal to a preset number.

According to an embodiment, the processor 120 of the base station 101 may check the occurrence of an error related to data packet transmission in layer 1 and layer 2 level protocols. For example, the processor 120 may check transmission-related information of packets in protocol layers of PDCP, RLC, and MAC.

According to an embodiment, the processor 120 may check the payload type through the payload of the RTP packet. The processor 120 may check packet interval time information according to a packet type based on a codec of audio data or video data. The processor 120 may obtain delay time information due to handover based on the packet interval time information and the number of buffered packets due to handover. A specific operation of obtaining delay time information due to handover of the processor 120 will be described in detail with reference to FIG. 7 .

Operations 710 to 750 may be performed by the processor 120 of the target base station 101 described above with reference to FIG. 1, and duplicate descriptions of those described with reference to FIGS. 1 to 6 will be omitted for brevity. It can be. As described above with reference to FIGS. 1 to 6 , the target base station 101 is a target cell (e.g. : It may be a base station that controls the target cell 211 of FIG. 2A.

According to an embodiment, in operation 710, the processor 120 allows the terminal 200 that has attached to the target base station 101 to move from a source cell (eg, the source cell 212 of FIG. 2A) to a target cell (eg, the source cell 212 of FIG. 2A). It may be determined whether the UE is performing handover to the target cell 211 of FIG. 2A. For example, in the handover process described above with reference to FIG. 3, the terminal 200 performs handover based on the handover request received from the source base station 102 (eg, step 4 of FIG. 3: Handover Request). It can be determined whether the terminal is

According to an embodiment, in operation 720, the processor 120 may receive pre-handover delay time information from the source base station 102 as it transmits a request to the source base station 102 that controls the source cell. As described above with reference to FIG. 5, the pre-handover delay time information may be information on the delay time occurring to the user in the handover preparation step 350 described above with reference to FIG. 3, and the source base station 102 can be obtained from For example, the pre-handover delay time information is transmitted to the terminal 200 from the time when the source base station 102 transmits a packet to the terminal 200 in the handover process described above with reference to FIG. 3 but does not receive an ACK. It may include time information up to the point at which the over command (eg, step 7 of FIG. 3: handover command) is transmitted.

According to an embodiment, in operation 730, the processor 120 delays due to handover based on the number of packets forwarded from the source base station 102 and buffered due to handover and the packet information received from the terminal 200. Time information can be obtained. For example, in the handover process described above with reference to FIG. 3, a data forwarding process in which the source base station 102 transmits a buffer and in-transit packets to the target base station 101 is performed. Through this, the processor 120 of the target base station 101 may forward the buffered packet. As described above with reference to FIG. 3 , the processor 120 may forward information on the last partial packet transmitted from the source base station 102 to the terminal 200 from the source base station 102 . The processor 120 may obtain information about packets forwarded from the source base station 102 . For example, the processor 120 may receive information according to the protocol layer described above with reference to FIGS. 5 and 6 and information according to QoS, such as a Quality Class Identifier (QCI), and determine the number of forwarded packets. information can be obtained.

In operation 730, the processor 120 may receive packet information from the terminal 200. According to an embodiment, the processor 120 of the target base station 101 may receive information about some initial packets that may be lost in a handover process from the newly accessed terminal 200 . As described above with reference to FIGS. 5 and 6 , the processor 120 may receive information related to data packet transmission in layer 1 and layer 2 protocols from the terminal 200, and may transmit information according to QoS such as QCI. can receive For example, the processor 120 may check transmission-related information of packets in protocol layers of PDCP, RLC, and MAC, which are protocol layers described above with reference to FIG. 4 . In addition, as described above with reference to FIG. 6, the processor 120 checks the RTP packet configuration, checks the RTP payload type, and obtains packet interval time information according to the codec of voice data or video data. can do.

The processor 120 of the target base station 101 not only obtains information from packets transmitted from the source base station 102 and packets transmitted from the terminal 200, but also may receive information from an external entity. For example, the processor 120 may receive base station location information, ISD (Inter Site Distance) information, PCI (Physical Cell Identify) information, and the like from an external base station.

According to an embodiment, the processor 120 may obtain delay time information due to handover based on packet interval time information and the number of buffered packets due to handover in operation 730 . A specific operation of obtaining delay time information due to handover of the processor 120 will be described in detail with reference to FIG. 8 .

According to an embodiment, in operation 740, the processor 120 may obtain information about a post-handover delay time occurring after access of the terminal 200. As described above with reference to FIG. 5 , the post-handover delay time information may be information on the delay time generated in the handover completion step 370 described above with reference to FIG. 3 . For example, the post-handover delay time information indicates that the target base station 101 receives handover completion from the terminal 200 in the handover process described above with reference to FIG. 3 (eg, step 11 of FIG. 3: handover completion). It may include time information from the time of reception to the time when the serving cell of the terminal 200 is changed to the target cell.

According to an embodiment, the processor 120 transmits information about the time when the source base station 102 releases resources with the terminal 200 (eg, step 18 of FIG. 3: resource release) to the source base station 102 or Time information received from the terminal 200 and from the time when handover completion is received to the time when resources of the terminal 200 and the source base station 102 are released may be determined as post-handover delay time information. According to another embodiment, the processor 120 of the target base station 101 issues a resource release instruction command (eg, step 17 of FIG. 3 : resource release instruction) to the source base station 102 from the time when handover completion is received. Time information up to the point of transmission may be determined as post-handover delay time information.

According to an embodiment, in operation 750, the processor 120 may calculate the total delay time generated in the user plane by summing pre-handover delay time information, handover delay time information, and post-handover delay information. The processor 120 calculates the total delay time substantially occurring in the user-plane throughout the handover preparation phase 350, the handover execution phase 360, and the handover completion phase 370, QoS that can be experienced from the user side can be improved.

Operations 810 to 830 may be performed by the processor 120 of the base station 101 described above with reference to FIG. 1, and duplicate descriptions of those described with reference to FIGS. 1 to 7 will be omitted for brevity. can According to an embodiment, the processor 120 may perform operations 810 to 830 after calculating the total delay time generated in the user plane described with reference to FIG. 7 (eg, operation 750 of FIG. 7 ).

According to an embodiment, in operation 810, the processor 120 may determine whether the total delay time generated in the user plane exceeds a threshold value. When the total delay time does not exceed the threshold value, the processor 120 continues to communicate with the terminal 200, and when another terminal accesses the target base station 101 again, the operations described with reference to FIG. 7 are performed. can be done

According to an embodiment, when the total delay time generated in the user plane exceeds the threshold value, the processor 120, in operation 820, performs traffic information, mobility information of the terminal, source cell information, target cell information, and neighbor information. Feedback information may be generated based on at least one of cell information. However, this is only an example, and the processor 120 may generate feedback information based on various information. For example, as described in operation 730 of FIG. 7, the processor 120 performs packet information received from the source base station 102 and packet information received from the terminal 200 as well as base station location information received from an external base station. Feedback information may be generated based on inter site distance (ISD) information, physical cell identify (PCI) information, and the like. As described above with reference to FIG. 5 , since the processor 120 collects packet information at the level of the base station, it is possible to determine where a problem section due to handover is and to analyze which protocol layer it occurred in.

According to one embodiment, in operation 830, the processor 120 may transmit the generated feedback information to the source base station 101 or another base station.

In FIGS. 7 and 8 , operations are described centering on the processor 120 of the target base station 101 , but operations may be separately performed in several base stations depending on implementation. According to an embodiment, an operation of collecting packet information and classifying according to a protocol layer and QoS (eg, an operation of receiving packet information in operation 730 of FIG. 7 ) is performed in the target base station 101, and the packet information is analyzed. operation (eg, calculating the total delay time due to handover through operations 720 to 750 of FIG. 7) and generating feedback information (eg,

operations

810 and 820 of FIG. 8) are performed in different base stations. can be performed

Operations 910 to 920 may be performed by the processor 120 of the target base station 101 described above with reference to FIG. 1 . According to an embodiment, operations 910 to 920 may correspond to operations for obtaining delay time information due to handover described with reference to FIG. 7 (eg, operation 730 of FIG. 7 ).

According to an embodiment, in operation 910, the processor 120 may obtain interval time information of the packet based on the RTP payload type of the packet. As described above with reference to FIG. 7 , the processor 120 may obtain information on packets forwarded from the source base station 102 and buffered due to handover and information on packets received from the terminal 200. there is. For example, the processor 120 may obtain packet information by receiving some last packets transmitted from the source base station 102 to the terminal 200, and loss may occur in the handover process from the terminal 200 that has accessed it. It is possible to receive information about some of the initial packets present.

As described above with reference to FIG. 6, the processor 120 checks the RTP packet configuration to check the RTP payload type, and obtains packet interval time information according to the codec of voice data or video data. can

According to an embodiment, the processor 120 may not be able to obtain interval time information only with RTP payload type information. For example, in the case of VoLTE, the processor 120 may not be able to obtain interval time information as RTP payload type information. When interval time information cannot be obtained with RTP payload type information, the processor 120 may obtain packet interval time information according to a data type based on QoS information (eg, QCI).

According to an embodiment, in operation 920, the processor 120 multiplies the packet interval time information by the number of packets buffered due to the handover, thereby performing the handover (eg, performing the handover step 360 of FIG. 3). Latency information can be calculated.

Operations 1010 to 1050 may be performed by the processor 120 of the base station 102 described above with reference to FIG. 1, and duplicate descriptions of those described with reference to FIGS. 1 to 9 will be omitted for brevity. can As described above with reference to FIGS. 1 to 9 , the base station 102 is a source cell (eg: It may be a base station that controls the source cell 212 of FIG. 2A. Operations 1010 to 1050 may be operations in which a processor (not shown) of the source base station 102 performs the operation of the processor 120 of the target base station 101 described with reference to FIG. 7 .

According to an embodiment, in operation 1010, the processor of the source base station 102 moves the terminal 200 connected to the base station 101 from a source cell (eg, the source cell 212 of FIG. 2A) to a target cell (eg, FIG. 2A). It is possible to determine whether the terminal is performing handover to the target cell 211 of . For example, in the handover process described above with reference to FIG. 3, the processor of the source base station 102 receives a measurement report (eg, step 2 of FIG. 3: measurement report) from the terminal 200 and makes a handover decision (eg : Step 3 of FIG. 3: handover determination), it may be determined whether the terminal 200 is performing handover.

According to an embodiment, in operation 1020, the processor of the base station 102 may obtain pre-handover delay time information. As described above in operation 720 of FIG. 7, the processor of the source base station 102 sends a handover command to the terminal 200 (e.g., 7 in FIG. Step: Handover command) may be obtained prior to handover delay time information.

According to an embodiment, in operation 1030, the processor of the source base station 102 may forward the buffered packet due to the handover to the target base station 101. For example, in the handover process described above with reference to FIG. 3, a data forwarding process in which the source base station 102 transmits a buffer and in-transit packets to the target base station 101 is performed. Through this, the processor of the source base station 102 may forward the buffered packet to the target base station 101 . As described above in operation 730 of FIG. 7 , the processor of the source base station 102 may forward information on some of the last packets transmitted to the terminal 200 to the target base station 101 .

According to an embodiment, in operation 1040, the processor of the source base station 102 may receive handover delay time information and post-handover delay time information from the target base station 101. As described above with reference to

operations

730 and 740 of FIG. 7 and FIG. 8 , the processor 120 of the target base station 101 multiplies the packet interval time information by the number of buffered packets to perform the handover delay. Time information may be obtained, and post-handover delay time information occurring after access of the terminal 200 may be obtained.

According to an embodiment, in operation 1050, the processor of the source base station 102 may calculate the total delay time generated in the user plane by summing pre-handover delay time information, handover delay time information, and post-handover delay information. there is. The processor of the source base station 102 substantially reduces the total delay time occurring in the user-plane throughout the handover preparation phase 350, the handover execution phase 360, and the handover completion phase 370. By calculating, the QoS experienced by the user can be improved.

The embodiments described above may be implemented as hardware components, software components, and/or a combination of hardware components and software components. For example, the devices, methods, and components described in the embodiments may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA) ), a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and software applications running on the operating system. A processing device may also access, store, manipulate, process, and generate data in response to execution of software. For convenience of understanding, there are cases in which one processing device is used, but those skilled in the art will understand that the processing device includes a plurality of processing elements and/or a plurality of types of processing elements. It can be seen that it can include. For example, a processing device may include a plurality of processors or a processor and a controller. Other processing configurations are also possible, such as parallel processors.

Software may include a computer program, code, instructions, or a combination of one or more of the foregoing, which configures a processing device to operate as desired or processes independently or collectively. You can command the device. Software and/or data may be any tangible machine, component, physical device, virtual equipment, computer storage medium or device, intended to be interpreted by or provide instructions or data to a processing device. , or may be permanently or temporarily embodied in a transmitted signal wave. Software may be distributed on networked computer systems and stored or executed in a distributed manner. Software and data may be stored on computer readable media.

The method according to the embodiment may 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, etc. alone or in combination, and the program instructions recorded on the medium may be specially designed and configured for the embodiment or may be known and usable to those skilled in the art of computer software. may be Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. - includes hardware devices specially configured to store and execute program instructions, such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter, as well as machine language codes such as those produced by a compiler.

The hardware device described above may be configured to operate as one or a plurality of software modules to perform the operation of the embodiment, and vice versa.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on them. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Claims

In a base station of a wireless communication system,

A communication module for communicating with a source base station that controls a user terminal and a source cell;

a memory in which computer-executable instructions are stored; and a processor accessing the memory to execute the instructions.

including,

These commands are

If the terminal accessing the base station (the base station is a target base station that controls a target cell) performs handover from the source cell to the target cell,

Receiving pre-handover delay time information from the source base station as the request is transmitted to the source base station;

Obtaining delay time information due to the handover based on the number of buffered packets forwarded from the source base station and packet information received from the terminal;

Acquiring post-handover delay time information occurring after the terminal attaches,

The total delay time generated in the user-plane is calculated based on the pre-handover delay time information, the delay time due to the handover, and the post-handover delay time information.

configured to

base station.
According to claim 1,

These commands are

If the total delay time exceeds the threshold value,

generating feedback information based on at least one of traffic information, mobility information of the terminal, the source cell information, the target cell information, and neighbor cell information;

Transmitting the feedback information to the source base station or another base station

further configured to

base station.
According to claim 1,

The packet information,

Classified according to protocol layer and quality of service (QoS),

base station.
According to claim 1,

The packet information,

information on the last partial packet transmitted from the source base station to the terminal; and

Information on some initial packets transmitted from the terminal accessing the target base station to the target base station

including,

base station.
According to claim 1,

These commands are

Determination of whether the terminal performs handover from the source cell to the target cell based on a handover request received from the source base station

configured to

base station.
According to claim 1,

The pre-handover delay time information,

Including time information from the time when the source base station transmits a packet to the terminal but does not receive an ACK to the time when the source base station transmits a handover command to the terminal,

base station.
According to claim 1,

The packet information includes the packet type information and interval time information according to the packet type,

These commands are

Delay time information due to the handover is obtained by multiplying the number of buffered packets by the interval time information.

configured to

base station.
According to claim 7,

These commands are

Acquiring interval time information of the packet based on a real-time transport protocol (RTP) payload type of the packet

configured to

base station.
According to claim 1,

The post-handover delay time information,

Including time information from the time when the target base station receives handover complete from the terminal to the time when the serving cell of the terminal is changed to the target cell,

base station.
According to claim 1,

Each of the target base station and the source base station is either a long term evolution (LTE) base station or a new radio (NR) base station,

The target base station and the source base station control different cell groups and can transmit and receive signals simultaneously with the user equipment.

base station.
In the method of operating a base station in a wireless communication system,

If the terminal accessing the base station (the base station is a target base station that controls a target cell) performs handover from a source cell to the target cell,

receiving pre-handover delay time information from the source base station as a request is transmitted to the source base station controlling the source cell;

obtaining delay time information due to the handover based on the number of buffered packets forwarded from the source base station and packet information received from the terminal;

obtaining post-handover delay time information occurring after the terminal is attached; and

Calculating a total delay time generated in a user-plane based on the pre-handover delay time information, the handover-induced delay time information, and the post-handover delay time information

including,

A method of operating a base station.
According to claim 11,

The method,

If the total delay time exceeds the threshold value,

generating feedback information based on at least one of traffic information, mobility information of the terminal, the source cell information, the target cell information, and neighbor cell information; and

Transmitting the feedback information to the source base station or another base station

Including more,

A method of operating a base station.
According to claim 11,

The packet information,

Classified according to protocol layer and quality of service (QoS),

A method of operating a base station.
According to claim 11,

The packet information,

information on the last partial packet transmitted from the source base station to the terminal; and

Information on some initial packets transmitted from the terminal accessing the target base station to the target base station

including,

A method of operating a base station.
A computer program stored in a computer readable recording medium in order to execute the method of any one of claims 11 to 14 in combination with hardware.