JP2007150538A - Handover method, mobile terminal, base station, and edge apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a handover method whereby the reception of duplicate frames by a mobile terminal is decreased at soft handover. <P>SOLUTION: An ingress LSR 10 being the edge apparatus at a frame ingress side of a network inserts a label to an ingress frame, increments a sequence number denoting a frame sequence by each frame transfer and attaches the incremented number to the label, a plurality of the base stations BS#1, BS#2, BS#3, BS#4 buffer the frame attached with the sequence number, and when the mobile terminal MH#1 changes the base station, the moving source base station informs the moving destination base station BS#2 about the sequence numbers of the frames having been transmitted to the mobile terminal MH#1, and when the moving destination base station BS#2 connects to the mobile terminal MH#1, the moving destination base station BS#2 transmits frames not received by the mobile terminal MH#1 among the frames in the buffer on the basis of the informed sequence numbers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a handover method for transferring packets to a plurality of base stations at the time of handover by applying a label switch technology for transferring user data using a label such as an MPLS (Multi Protocol Label Switching) label to a mobile unit, The present invention relates to a mobile terminal, a base station, and an edge device, and more particularly, to a handover method related to buffer management at the time of soft handover control, a mobile terminal, a base station, and an edge device.

Soft handover is a method for reducing packet loss in a handover method in mobile communication. This is to prevent the disconnection of the communication at the time of handover by copying the packet to the destination route in advance and transferring the packet before the movement. A method for performing soft handover in an access network using MPLS is described in Patent Document 1 below. In the technique disclosed in Patent Document 1, a mobile terminal that is under the control (diversity area) of a plurality of adjacent base stations notifies a server on the network side of information on which base station is under control. The server uses this information to construct a P2MP (Point to Multi Point) LSP (Label Switched Path) and forwards the packet to a plurality of base stations in the diversity area where the mobile terminal is located. A handover is being executed.
JP 2004-236294 A (abstract)

  When performing such P2MP type soft handover, a frame to a mobile terminal is duplicated at a path branch point and transferred to each base station. In the case of a wireless communication system and a wireless terminal capable of simultaneous communication with a plurality of base stations, since the transferred frame can be received by the wireless terminal through the plurality of base stations, handover without packet loss can be performed. it can. However, in the case of a wireless communication method and a wireless terminal that can communicate with only one wireless base station at the same time (such as a wireless LAN terminal having one wireless interface), the destination base station is wireless with the wireless terminal. Since there is no link connection, in order to realize a handover without packet loss, it is necessary to buffer the frame until the wireless terminal moves. Therefore, in order to prevent packet loss, this buffer needs to be secured sufficiently. However, if the number of frames that are buffered in this way increases, the wireless terminal may receive the received frame again after connecting to the destination base station, which wastes the bandwidth of the wireless section. In addition, it causes an increase in user data reception delay and jitter.

  FIG. 7 shows a frame buffer of a conventional soft handover method. In each base station BS # 1 to BS # 4, frame buffering is performed at the time of soft handover in order to prevent packet loss at the time of connection change. When the mobile terminal MH # 1 changes the connection from the base station BS # 3 to the base station BS # 2, the base station BS # 2 starts to transmit the buffered frame. This can eliminate the packet loss, but the mobile terminal MH # 1 may receive the same frame again instead. In order to eliminate the packet loss, the larger the buffer amount, the higher the possibility of re-reception, leading to unnecessary consumption of the radio band and an increase in delay and jitter. Further, when the mobile terminal MH # 1 moves to the area of the base station BS # 1, there is a possibility that the same frame is received again.

  An object of the present invention is to provide a handover method, a mobile terminal, a base station, and an edge device that can reduce the reception of duplicate frames by a mobile terminal during soft handover.

In order to achieve the above object, the handover method of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame when the mobile terminal moves. In the handover method of transferring to the mobile terminal
The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label; and
The plurality of base stations buffering the frame with the sequence number added thereto;
When changing the base station to which the mobile terminal is connected, notifying the destination base station of the sequence number of the frame that has already been transmitted to the mobile terminal;
When the destination base station connects to the mobile terminal, the step of transmitting to the mobile terminal from the frame that has not yet been received by the mobile terminal based on the notified sequence number among the buffered frames And
It was set as the structure which has.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame that has not yet been received from the destination base station, so that it is possible to reduce the mobile terminal from receiving duplicate frames during soft handover. it can.

The handover method of the present invention is also characterized in that the mobile terminal transmits a connection change notification including information indicating the destination base station to the base station that is currently communicating when the base station is changed, and the destination base Means for transmitting a connection notification to the station,
The base station that has received the connection change notification includes means for notifying the destination base station included in the connection change notification of a sequence number of a frame that has already been transmitted to the mobile terminal,
The destination base station is configured to transmit to the mobile terminal from a frame not yet received by the mobile terminal based on the sequence number notified by the base station that has received the connection change notification.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

The mobile terminal of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations replicate the same frame and transfer it to the mobile terminal In the handover method, an edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating a frame order for each frame transfer to the label. When the plurality of base stations buffer the added frame and the mobile terminal changes the base station, the sequence number of the frame already transmitted to the mobile terminal is notified to the destination base station, and the destination Of the buffered frames when the mobile terminal is connected to the mobile terminal. A said mobile terminal when implementing the handover method of transmitting from a frame in which the mobile terminal has not yet received based on the sequence number,
Means for transmitting a connection change notification including information indicating the destination base station to a base station that is currently communicating at the time of base station change;
Means for transmitting a connection notification to the destination base station;
The base station that has received the connection change notification notifies the destination base station included in the connection change notification of the sequence number of the frame that has been transmitted to the mobile terminal, and the destination base station Based on the sequence number notified by the base station that has received the notification, transmission is performed from a frame not yet received by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

The base station of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal In the handover method, an edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating a frame order for each frame transfer to the label. When the plurality of base stations buffer the added frame and the mobile terminal changes the base station, the sequence number of the frame already transmitted to the mobile terminal is notified to the destination base station, and the destination Of the buffered frames when the mobile station is connected to the mobile terminal. When realizing a handover method for transmitting from a frame that the mobile terminal has not yet received based on the sequence number, information indicating the destination base station to the base station with which the mobile terminal is currently communicating when the base station is changed The base station that has received the connection change notification when transmitting a connection notification to the destination base station,
Means for notifying the sequence number of a frame that has already been transmitted to the mobile terminal to a destination base station included in the connection change notification;
Based on the sequence number notified by the base station from which the destination base station has received the connection change notification, transmission is performed from a frame not yet received by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

Also, the base station of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the plurality of base stations buffer the frame with the added, and the mobile terminal changes the base station, the mobile station is notified of the sequence number of the frame that has been transmitted to the mobile terminal, and the mobile terminal When the previous base station connects to the mobile terminal, the notification is sent out of the buffered frames. When the mobile terminal realizes a handover method that transmits from a frame that has not yet been received based on the sequence number, the mobile terminal indicates the destination base station to the base station that is currently communicating when the base station is changed The base station that has received the connection change notification when transmitting a connection notification to the destination base station, while transmitting a connection change notification including information,
Means for notifying the sequence number of a frame that has already been transmitted to the mobile terminal to a destination base station included in the connection change notification;
Based on the sequence number notified by the base station from which the movement-destination base station has received the connection change notification, the mobile terminal transmits a frame that has not yet been received by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

In addition to the above configuration, the handover method of the present invention adds a means for detecting that the base station in communication is disconnected from the mobile terminal and the label when detecting the disconnection. Information indicating the mobile terminal that has detected the disconnection to the edge device, and means for notifying the mobile terminal of the sequence number of a frame that has already been transmitted,
The edge device notified of the sequence number has means for notifying all base stations constituting the P2MP path of information indicating the mobile terminal that detected the disconnection and the sequence number of the transmitted frame,
Based on the sequence number notified by the edge device, the movement-destination base station transmits to the mobile terminal from a frame not yet received by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

Also, the base station of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the plurality of base stations buffer the frame with the added, and the mobile terminal changes the base station, the mobile station is notified of the sequence number of the frame that has been transmitted to the mobile terminal, and the mobile terminal When the previous base station connects to the mobile terminal, the notification is sent out of the buffered frames. A base station in communication when implementing the handover method of transmitting from said mobile terminal has not received frame based on the sequence number,
Means for detecting that communication with the mobile terminal has been disconnected;
When the disconnection is detected, the edge device to which the label is added includes information indicating the mobile terminal that has detected the disconnection, and means for notifying the mobile terminal of the sequence number of the frame that has been transmitted,
The edge device notified of the sequence number notifies the mobile terminal that has detected the disconnection and the sequence number of the transmitted frame to all base stations that constitute the P2MP path, and the destination base station Based on the sequence number notified by the edge device, the mobile terminal is configured to transmit from a frame not yet received.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

Also, the edge device of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the plurality of base stations buffer the frame with the added, and the mobile terminal changes the base station, the mobile station is notified of the sequence number of the frame that has been transmitted to the mobile terminal, and the mobile terminal When the previous base station connects to the mobile terminal, among the buffered frames, the communication When implementing a handover method for transmitting from a frame that has not yet been received by the mobile terminal based on the sequence number that has been received, when the base station in communication detects that communication with the mobile terminal has been disconnected, The edge device in the case of notifying the edge device to which the label is added information indicating the mobile terminal that has detected the disconnection and the sequence number of a frame that has already been transmitted to the mobile terminal,
Means for notifying all base stations constituting the P2MP path of information indicating the mobile terminal that detected the disconnection and a sequence number of the transmitted frame;
Based on the sequence number notified by the edge device, the base station of the movement destination is configured to transmit from a frame not yet received by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

Furthermore, the base station of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the plurality of base stations buffer the frame with the added, and the mobile terminal changes the base station, the mobile station is notified of the sequence number of the frame that has been transmitted to the mobile terminal, and the mobile terminal When the previous base station is connected to the mobile terminal, the notification is received from the buffered frames. When implementing a handover method for transmitting from a frame that has not yet been received by the mobile terminal based on the received sequence number, if the base station in communication detects that communication with the mobile terminal has been disconnected, Information indicating the mobile terminal that detected the disconnection is sent to the edge device to which the label is added and the sequence number of the frame that has already been transmitted to the mobile terminal, and the edge device transmits the disconnection to all base stations that constitute the P2MP path. The base station of the movement destination when notifying the information indicating the mobile terminal that has detected and the sequence number of the transmitted frame,
Based on the sequence number notified by the edge device, the mobile terminal is configured to transmit from a frame not yet received.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

In addition to the above configuration, the handover method of the present invention is characterized in that the mobile terminal manages the means for terminating the label, the means for managing the sequence number of the received frame, and the base station when the base station is changed. Means for notifying the destination base station of the sequence number of the received frame,
The base station of the movement destination is configured to transmit to the mobile terminal from a frame not yet received by the mobile terminal based on the sequence number notified by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

Furthermore, the mobile terminal of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the plurality of base stations buffer the frame with the added, and the mobile terminal changes the base station, the mobile station is notified of the sequence number of the frame that has been transmitted to the mobile terminal, and the mobile terminal When the previous base station connects to the mobile terminal, among the buffered frames, the communication A said mobile terminal when implementing the handover method of transmitting from a frame in which the mobile terminal based on the sequence number has not yet received that is,
Means for terminating the label;
Means for managing the sequence number of received frames;
Means for notifying the destination base station of the sequence number of the received frame managed when changing the base station,
The destination base station is configured to transmit from a frame not yet received by the mobile terminal based on the sequence number notified by the mobile terminal.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

Furthermore, the base station of the present invention forms a P2MP path for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations copy the same frame and transfer it to the mobile terminal The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the plurality of base stations buffer the frame with the added, and the mobile terminal changes the base station, the mobile station is notified of the sequence number of the frame that has been transmitted to the mobile terminal, and the mobile terminal When the previous base station is connected to the mobile terminal, the notification is received from the buffered frames. The mobile terminal has a function of terminating the label and manages the sequence number of the received frame when realizing a handover method in which the mobile terminal transmits from a frame that has not yet been received based on the received sequence number The destination base station when notifying the destination base station of the sequence number of the received frame managed when changing the base station,
Based on the sequence number notified by the mobile terminal, the mobile terminal transmits a frame that has not been received yet.
With this configuration, when the mobile terminal changes the base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal is prevented from receiving duplicate frames during soft handover. Can do.

  According to the present invention, when a mobile terminal changes a base station, it is transmitted from a frame not yet received from the destination base station, so that the mobile terminal can reduce the reception of duplicate frames during soft handover. Can do.

  Embodiments of the present invention will be described below with reference to the drawings. The basis of the present invention is that when a label is inserted into a frame by a label switch router (Ingress LSR) on the frame entry side, a sequence number is added to the label, and the sequence number at which the mobile terminal or the like has received the frame is moved. By notifying the destination base station, after the movement, the destination base station starts transmission from a frame having a subsequent sequence number.

<Embodiment 1>
The point of Embodiment 1 of the present invention is to notify the number of a transmitted frame between base stations without using a label between the base station and the mobile terminal. FIG. 1 is a system configuration diagram according to Embodiment 1 of the present invention. FIG. 1 shows an access network to which the present invention is applied, and base stations BS # 1 to BS # 4 on the packet egress side (egress) from Ingress LSR10, which is an edge device on the side where packets addressed to mobile terminal MH # 1 enter. The P2MP path P up to is formed for the mobile terminal MH # 1. In FIG. 1, from the Ingress LSR 10 to the base stations BS # 1 and BS # 2 via the LSR # 1 and LSR # 2 serving as branch points of the path P, and via the LSR # 1 and LSR # 3 It shows that the P2MP path P is formed up to the base stations BS # 3 and BS # 4. This P2MP path P is a path for L2 tunneling the received frame of the mobile terminal MH # 1, and is configured using, for example, EoMPLS (Ethernet (registered trademark) over MPLS) or using VLAN (Virtual LAN). It is assumed that it is configured.

  In FIG. 1, it is assumed that the mobile terminal MH # 1 is currently connected to and communicates with the base station BS # 3 among the base stations BS # 1 to BS # 4. Here, in Embodiment 1, since the label termination is performed in the base stations BS # 1 to BS # 4, this sequence number is used only in the access network, and the mobile terminal MH # 1 needs to be aware of this. There is no. FIG. 1 also shows the flow of frames addressed to the mobile terminal MH # 1. Numbers 1 to 6 assigned to the frames in FIG. 1 indicate sequence numbers indicating the frame order newly added in the present invention in the label added to the frame addressed to the mobile terminal MH # 1 by the Ingress LSR 10. . In FIG. 1, six frames pass through the Ingress LSR 10 and sequence numbers are added. Of these, frames 1 and 2 indicate that the mobile terminal MH # 1 has already been received, and the base station BS # 3 is currently transmitting the frame 3. At this time, in the other base stations BS # 1, BS # 2, and BS # 4, after the P2MP path P is formed, frames addressed to the mobile terminal MH # 1 are buffered. Also, since the frames are duplicated at LSR # 1, LSR # 2, and LSR # 3, which are the branch points of the P2MP path P, frames with the same sequence number are buffered at all base stations BS # 1 to BS # 4. The

  A sequence when the mobile terminal MH # 1 switches the connection from the base station BS # 3 to the base station BS # 2 is shown in FIG. The mobile terminal MH # 1 outputs a connection change notification to the currently connected base station BS # 3 in order to switch the radio link from the base station BS # 3 to the base station BS # 2 (step S1), and after disconnecting the link Then, a connection notification is transmitted to the base station BS # 2 which is a new connection destination (step S4). At this time, the connection change notification to the base station BS # 3 in step S1 includes the ID (BS # 2) of the base station to be connected next by the mobile terminal MH # 1.

  The base station BS # 3 that has received the connection change notification stops transmission to the mobile terminal MH # 1, starts buffering the frame (step S2), and moves to the base station BS # 2 included in the connection change notification. The ID of terminal MH # 1 and the sequence number (sequence number 2 in the example of FIG. 2) transmitted by itself are notified (step S3). The base station BS # 2 that receives the connection notification from the mobile terminal MH # 1 and establishes the connection starts frame transmission (step S5). At this time, since the base station BS # 2 has received the sequence number notification from the base station BS # 3, the base station BS # 2 transmits frames after the notified sequence number (sequence number 3 and later). In addition, when the connection with the mobile terminal MH # 1 is established before the sequence number notification, the base station BS # 2 starts outputting from the first frame buffered, but when the sequence number notification is received, Start outputting frames after the notified sequence number. At this time, the previous frame is discarded.

  Further, in order to reduce the buffer amount of the base stations BS # 1 to BS # 4, the base stations BS # 1 to BS # 4 perform buffer aging based on the link switching time of the wireless communication scheme. For example, if the maximum value of the link switching time is 100 ms, the buffer is deleted with an aging time of 100 to 200 ms. This aging time may be adjusted in consideration of packet loss and is treated as a variable. When buffer aging is performed in this way, the maximum number of frames received is determined according to the aging time, and therefore the bit indicating the sequence number can be reduced.

  FIG. 3 shows a label mapping table of the Ingress LSR 10. The label mapping table searches an output destination port and a label to be used based on the received frame ID. In the present invention, a new counter is provided for each IN_frame, and this counter value is inserted as a sequence number in the label. This counter is incremented every time a frame is transmitted, and returns to 1 when the maximum value is reached.

  Next, when the mobile terminal MH # 1 changes the connection destination base station BS, the process when the connection destination change notification cannot be received by the base station BS # 3 (step S11) will be described with reference to FIG. . The case where the base station BS # 3 cannot receive the connection destination change notification means that, for example, the connection destination is changed with respect to the base station BS # 3 due to rapid deterioration of the radio state between the mobile terminal MH # 1 and the base station BS # 3. For example, when the wireless link is disconnected without being notified, or when the connection destination change notification is output, this frame is lost. When the base station BS # 3 cannot receive the connection destination change notification, the base station BS # 3 needs to detect the disconnection with the mobile terminal MH # 1 by itself. This depends on the wireless communication system. For example, in the case of a wireless LAN, a reception completion ACK is returned from the terminal every time a frame is transmitted, so that it is detected as a trigger that this ACK cannot be received (step S12).

  The base station BS # 3 that detects the disconnection with the mobile terminal MH # 1 stops transmission and starts buffering the frame itself (step S13). After that, the base station BS # 3 notifies the ID of the mobile terminal MH # 1 and the transmitted sequence number to the Ingress LSR 10 (step S14). Since the Ingress LSR 10 manages the base stations BS # 1 to BS # 4 that are the exits (egress) of the P2MP path P, the mobile terminal MH # 1 is connected to the base stations BS # 1 to BS # 4. The ID and the transmitted sequence number are notified (step S15). The base station BS # 2 that has received the connection notification from the mobile terminal MH # 1 (step S16) adjusts the frame to be transmitted based on the sequence number notification from the Ingress LSR 10 and has not yet been received by the mobile terminal MH # 1. (Step S17).

<Embodiment 2>
The point of Embodiment 2 is that communication is performed using a label between the base station and the mobile terminal, and the mobile terminal MH # 1 notifies the sequence number. FIG. 5 shows a system configuration according to Embodiment 2 of the present invention. The difference from the access network shown in FIG. 1 is that when the mobile terminal MH # 1 is connected to and communicates with the base station BS # 3, a P2MP path is also established between the mobile terminal MH # 1 and the base station BS # 3. P is extended and transfer using a label is performed. FIG. 5 shows a flow of frames addressed to the mobile terminal MH # 1. The number given to the frame in FIG. 5 indicates the sequence number newly added in the present invention in the label added to the frame addressed to the mobile terminal MH # 1 by the Ingress LSR. Also in FIG. 5, six frames pass through the Ingress LSR 10 and are added with sequence numbers. Of these, frames 1 and 2 indicate that the mobile terminal MH # 1 has already been received, and the base station BS # 3 is currently transmitting the frame 3. At this time, the other base stations BS # 1, BS # 2, and BS # 4 buffer frames addressed to the mobile terminal MH # 1 after forming the P2MP path P. In addition, since the frames are duplicated at LSR # 1, LSR # 2, and LSR # 3, which are the branch points of the P2MP path P, frames with the same sequence number are buffered at all base stations BS # 1 to BS # 4. The

  FIG. 6 shows a sequence when the mobile terminal MH # 1 switches the connection from the base station BS # 3 to the base station BS # 2. In order to switch the radio link, the mobile terminal MH # 1 outputs a disconnection notification to the currently connected base station BS # 3 (step S21). After disconnecting the link, the mobile terminal MH # 1 newly transmits to the base station BS # 2 that is the connection destination. A connection notification is transmitted to the terminal (step S23). At this time, the sequence number of the frame received by the mobile terminal MH # 1 is added to the connection notification.

  Receiving the disconnection notification in step S21, the base station BS # 3 stops transmission to the mobile terminal MH # 1 and starts buffering the frame (step S22). Further, the base station BS # 2 that has received the connection notification in step S23 starts transmission from a frame after the indicated number based on the sequence number included in the message (step S24). At this time, the previous frame is discarded. The mobile terminal MH # 1 notifies the sequence number in this way, so that even if the connection with the base station BS # 3 is suddenly lost, the mobile terminal MH # 1 itself is connected to the newly connected base station BS # 2. Since the sequence number can be notified directly, it is possible to reliably avoid redundant reception of frames.

  As described above, according to the present invention, frames that have already been received and buffered in the newly connected base station BS # 2 are not transmitted to the mobile terminal # 1, thereby reducing wasteful consumption of radio bands. It is possible to reduce a delay until the mobile terminal MH # 1 receives a useless frame and receives a necessary frame, and to reduce jitter. As a result, it becomes possible to support high-speed movement on a low-speed wireless link, for example.

  INDUSTRIAL APPLICABILITY The present invention has an effect of reducing the reception of duplicate frames by a mobile terminal during soft handover, and can be used for a mobile network.

System configuration diagram according to Embodiment 1 of the present invention Explanatory drawing which shows the procedure in which a mobile terminal changes a connecting base station in FIG. Explanatory drawing which shows the label mapping table of the frame entrance side LSR in FIG. Explanatory drawing which shows the other procedure in which a mobile terminal changes a connecting base station in FIG. System configuration diagram according to Embodiment 2 of the present invention Explanatory drawing which shows the procedure in which a mobile terminal changes a connecting base station in FIG. System configuration diagram showing a conventional soft handover method

Explanation of symbols

BS # 1, BS # 2, BS # 3, BS # 4 Base station MH # 1 Mobile terminal P P2MP path (path)
10 Ingress LSR

Claims (12)

In a handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer using a label, and a plurality of base stations replicate the same frame and transfer the same frame to the mobile terminal when the mobile terminal moves.
The edge device on the frame entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label; and
The plurality of base stations buffering the frame with the sequence number added thereto;
When changing the base station to which the mobile terminal is connected, notifying the destination base station of the sequence number of the frame that has already been transmitted to the mobile terminal;
When the destination base station connects to the mobile terminal, the step of transmitting to the mobile terminal from the frame that has not yet been received by the mobile terminal based on the notified sequence number among the buffered frames And
A handover method. The mobile terminal transmits a connection change notification including information indicating the destination base station to a base station that is currently communicating when the base station is changed, and a means for transmitting a connection notification to the destination base station And
The base station that has received the connection change notification includes means for notifying the destination base station included in the connection change notification of a sequence number of a frame that has already been transmitted to the mobile terminal,
The destination base station transmits to the mobile terminal from a frame not yet received by the mobile terminal based on the sequence number notified by the base station that has received the connection change notification. The handover method according to claim 1. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. The mobile terminal There are a still said mobile terminal when implementing the handover method of transmitting from a frame is not received,
Means for transmitting a connection change notification including information indicating the destination base station to a base station that is currently communicating at the time of base station change;
Means for transmitting a connection notification to the destination base station;
The base station that has received the connection change notification notifies the destination base station included in the connection change notification of the sequence number of the frame that has been transmitted to the mobile terminal, and the destination base station A mobile terminal configured to transmit from a frame not yet received by the mobile terminal based on the sequence number notified by the base station that has received the notification. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. When the mobile terminal implements a handover method for transmitting from a frame that has not been received yet, the connection change including information indicating the destination base station to the base station that the mobile terminal is currently communicating with when the base station is changed The base station that has received the connection change notification in the case of transmitting a notification and transmitting a connection notification to the destination base station,
Means for notifying the sequence number of a frame that has already been transmitted to the mobile terminal to a destination base station included in the connection change notification;
A base station configured to transmit from a frame not yet received by the mobile terminal based on the sequence number notified by the base station from which the destination base station has received the connection change notification. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and when the mobile terminal moves, a plurality of base stations replicate the same frame and transfer the same frame to the mobile terminal, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. When the mobile terminal implements a handover method for transmitting from a frame that has not been received yet, the connection change including information indicating the destination base station to the base station that the mobile terminal is currently communicating with when the base station is changed The connection change notification includes the sequence number of the frame that has been transmitted to the mobile terminal by the base station that has received the connection change notification and transmits the connection notification to the destination base station. The destination base station when notified to the destination base station,
A base station comprising means for transmitting from a frame not yet received by the mobile terminal based on the sequence number notified by the base station that has received the connection change notification. The base station in communication is means for detecting that the communication with the mobile terminal has been disconnected, and information indicating the mobile terminal that has detected the disconnection in the edge device to which the label is added when the disconnection is detected. And means for notifying the mobile terminal of the sequence number of the frame already transmitted,
The edge device notified of the sequence number has means for notifying all base stations constituting the P2MP path of information indicating the mobile terminal that detected the disconnection and the sequence number of the transmitted frame,
The handover according to claim 1, wherein the destination base station transmits to the mobile terminal from a frame not yet received by the mobile terminal based on the sequence number notified by the edge device. Method. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, An edge device on the frame entry side of the network inserts the label into the entry frame and adds a sequence number indicating the frame order to the label for each frame transfer, and adds the plurality of frames to which the sequence number is added. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. A base station in communication when implementing the handover method of transmitting from said mobile terminal has not received frames have,
Means for detecting that communication with the mobile terminal has been disconnected;
When the disconnection is detected, the edge device to which the label is added includes information indicating the mobile terminal that has detected the disconnection, and means for notifying the mobile terminal of the sequence number of the frame that has been transmitted,
The edge device notified of the sequence number notifies the mobile terminal that has detected the disconnection and the sequence number of the transmitted frame to all the base stations configuring the P2MP path, and the destination base station A base station configured to transmit from a frame not yet received by the mobile terminal based on a sequence number notified by an edge device. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. When implementing a handover method for transmitting from a frame that has not yet been received by the mobile terminal, if the base station in communication detects that communication with the mobile terminal has been disconnected, an edge with the label added thereto The edge device when notifying the device of information indicating the mobile terminal that detected the disconnection and the sequence number of a frame that has already been transmitted to the mobile terminal,
Means for notifying all base stations constituting the P2MP path of information indicating the mobile terminal that detected the disconnection and a sequence number of the transmitted frame;
An edge device configured to transmit from a frame not yet received by the mobile terminal based on a sequence number notified by the edge device by the base station of the movement destination. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. When implementing a handover method for transmitting from a frame that the mobile terminal has not yet received, an edge device to which the label is added when the communicating base station detects that the communication with the mobile terminal has been disconnected Information indicating the mobile terminal that detected the disconnection and the sequence number of the frame that has already been transmitted to the mobile terminal, and the edge device detects the mobile terminal that detected the disconnection to all base stations constituting the P2MP path. The destination base station when notifying the information indicating and the sequence number of the transmitted frame,
A base station comprising means for transmitting from a frame not yet received by the mobile terminal based on the sequence number notified by the edge device. The mobile terminal uses the means for terminating the label, the means for managing the sequence number of a received frame, and the sequence number of the received frame managed when changing the base station to the destination base station. And means for notifying
The handover according to claim 1, wherein the destination base station transmits to the mobile terminal from a frame not yet received by the mobile terminal based on the sequence number notified by the mobile terminal. Method. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. The mobile terminal There are a still said mobile terminal when implementing the handover method of transmitting from a frame is not received,
Means for terminating the label;
Means for managing the sequence number of received frames;
Means for notifying the destination base station of the sequence number of the received frame managed when changing the base station,
A mobile terminal configured to transmit from a frame not yet received by the mobile terminal based on a sequence number notified by the mobile terminal by the destination base station. A handover method in which a P2MP path is formed for each mobile terminal in a network that performs transfer by label, and a plurality of base stations replicate the same frame and transfer to the mobile terminal when the mobile terminal moves, The edge device on the network entry side of the network inserts the label into the entry frame and increments and adds a sequence number indicating the frame order for each frame transfer to the label. When the base station is buffered and the mobile terminal changes the base station, the mobile base station is notified of the sequence number of the frame transmitted to the mobile terminal, and the mobile base station Of the buffered frames based on the notified sequence number. When the mobile terminal implements a handover method for transmitting from a frame that has not been received yet, the mobile terminal has a function of terminating the label and manages the sequence number of the received frame to The destination base station when notifying the destination base station of the sequence number of the received frame that was managed when changing,
A base station comprising means for transmitting from a frame not yet received by the mobile terminal based on the sequence number notified by the mobile terminal.

Images