JP2853026B2 - Flow control method and mobile communication network having flow control function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control method, and more particularly, to a flow control method corresponding to a radio-specific handover (switching by moving) when an ATM method is applied to a multimedia mobile communication network of a microcell method. The present invention relates to a mobile communication network having a flow control function.

[0002]

2. Description of the Related Art In recent years, research and development on high-speed and multimedia transmission in mobile communication have been actively conducted.
In such a system, in order to suppress the transmission power, the radio communication range covered by one radio base station in a conventional automobile / mobile phone is several kilometers, but the radio communication range becomes about 100 m. Have been.
When the wireless communication range is small as described above, a mobile station moving at a high speed immediately goes out of the communication range, so that a function for performing handover between wireless base stations is required. Note that handover refers to switching of a radio base station in order to continue a call even if the mobile station moves between radio zones during a call.

[0003]

Conventionally, wireless communication range 1
There is a PHS as a system as narrow as about 00 m, but a mobile station moving at a speed of a pedestrian is assumed as a communication target, and handover of a mobile station moving at a high speed cannot be performed. In the conventional car telephone system, there is an instantaneous interruption of 0.7 to 0.8 seconds when switching channels during a call. This occurs because the data flowing through the transmission line during the handover is simply discarded. Due to this momentary interruption, in the case of transmission of audio and moving images, sound skips,
Although phenomena such as image quality deterioration appear, in the case of computer data transmission, data loss occurs, data retransmission occurs,
There was a problem that traffic congestion was caused. In the case of a microcell, a handover occurs in a shorter cycle than in a macrocell, so this problem becomes more remarkable.
In order to solve the problem of such an instantaneous interruption, not only a wireless-level channel switching technology but also a technology that does not cause data loss in the communication system as a whole is required.

[0004] In a mobile communication system, there are a radio portion between a mobile station and a radio base station, and a wired portion connecting the radio base station, the serving control station, and the gateway control station. As the wired part, a dedicated network is used in an automobile / mobile phone system, and an N-ISDN network is used in a PHS. However, in all cases, voice is assumed as a service quality, and moving images and computer data are also integrated and transmitted. Had a problem that he lacked the ability. Therefore, a network using the ATM system is expected as a wired network for performing high-speed multimedia transmission.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and it is not necessary to increase the memory capacity of a buffer for holding cells in a mobile communication network employing an ATM system for a wired part, and it is not necessary to perform handover at It is an object of the present invention to provide a flow control method between ATM nodes without data loss and a mobile communication network having a flow control function.

[0006]

In order to achieve the above object, the present invention relates to a method for establishing a communication between a radio base station in which a mobile station is located and an ATM node accommodating a communication partner terminal of the mobile station. When a mobile station moves to a radio zone of another radio base station in a mobile communication network that performs communication via the selected ATM virtual channel, handover start information is transmitted from the old radio base station to the ATM node. The ATM node specifies the ATM transmission line into which the ATM cell flows and the ATM virtual channel from the information, and suspends the switching of the ATM cell and temporarily stores the ATM cell.

[0007] When the handover is completed, the new radio base station transmits handover completion information to the ATM node.
The ATM transmission line and ATM virtual channel into which the ATM cell flows are specified, the stored ATM cell is transmitted, and the reservation is released.

In the above-mentioned flow control system,
It is also characterized in that handover start information and handover end information are successively transferred to the terminal ATM node, and cells are distributed and held in output hold queues provided in the ATM transmission lines of the respective ATM nodes.

Further, for each input ATM transmission line, there is provided an output destination table commonly referred to by the flow control module, the cell switch, and the cell switch control device.
Another feature is that the ATM virtual channel identifier when inputting to each ATM node is used to retrieve the ATM virtual channel identifier when outputting from each ATM node and the output ATM transmission line information.

According to the present invention, with such a configuration, the radio base station disperses and suspends cells by transferring handover start information from the neighboring serving control station or gateway control station to the end node one after another by the handover start notification cell. By stopping cell transmission at each node, cells can be held in the output hold queue having a smaller memory capacity, and cell loss during handover can be prevented.

[0011] Further, a simple notification mechanism using a handover start information cell and a handover end information cell, and an AT virtual channel identifier used when inputting to an ATM node is used to determine an AT.
By providing an output destination table having a structure in which an ATM virtual channel identifier and output ATM transmission line information at the time of output from the M node can be searched, high-speed flow processing is possible.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a block diagram showing a configuration of a mobile communication network to which the present invention is applied. A mobile communication network has a hierarchical structure. The gateway control station 1 is an ATM node (switch) located at the highest level of the hierarchy, and is connected to the serving control stations 2 and 3 located at lower levels.
It is also connected to another communication network 9. Serving control stations 2, 3
Is an ATM node located below the gateway control station 1. Although FIG. 2 shows only one layer, it may have a plurality of layers. Wireless base stations 4 to 7 are connected to the lowest located control stations 2 and 3.

Each of the radio base stations 4 to 7 performs radio connection with a mobile station 8 located in a predetermined service area (cell) 10 to 13, and when the mobile station 8 moves to another cell, The wireless base station is switched by performing a handover process as described later.

FIG. 1 is a block diagram showing an embodiment of the present invention in which a new radio base station and an old radio base station are connected to the same serving control station. Mobile station 11
Communicates with the wireless base station 21 via the wireless lines 41 and 51. The radio base stations 21 and 22 and the located control station 31 are connected to input / output ATM transmission lines 61, 71 and 6 respectively.
2, 72 are connected. Further, the located control station 31
It is assumed that the mobile station 11 is connected to another serving control station or a gateway control station via the input / output ATM transmission lines 63 and 73, and a terminal ATM node with which the mobile station 11 communicates exists.

The serving control station 31 includes a cell switch 81, a cell switch control device 91, flow control modules 101, 102, 103 existing for each input ATM transmission line, output holding queues (buffers) 111, 112, 113, and outputs. There are provided destination tables 121, 122 and 123. The output hold queues 111, 112, and 113 each have input A
In the TM transmission lines 61, 62 and 63, the cell switch 8
1 is a buffer memory of a cell connected to the previous stage.

Output destination tables 121, 122, 123
Are provided before the cell switch 81 in the input ATM transmission lines 61, 62, and 63, respectively, based on the ATM virtual channel identifier at the time of input of a cell, the virtual channel identifier at the time of the cell passing through the cell switch, and the ATM virtual at the time of output. This is a table from which a channel identifier and output ATM transmission line information can be searched, and includes a cell switch 81, a cell switch control device 91, flow control modules 101, 102, 1
03 is configured to be commonly referred to. Regarding the virtual channel identifier, the conversion of the virtual channel using the table is performed both when the cell is input to the switch and when the cell is output.

The flow control modules 101, 102, 1
03 monitors the input ATM transmission lines 61, 62 and 63 respectively, searches the output destination table with the ATM virtual channel identifier of the input cell, and finds that the output ATM transmission line information is "
If "pending", the cell is output to the output pending queue 111, 1
It is queued (stored) in 12, 113, and otherwise passed to the cell switch 81. The connection control information cell passes through the cell switch 81 to the cell switch control device 9.
Transferred to 1.

FIGS. 3, 4, and 5 are explanatory diagrams showing the flow control operation in the ATM node. FIG. 3 shows a state before the start of the handover. The wireless base stations 21 and 22 form an adjacent wireless zone, and the mobile station 11 is located in the wireless zone of the wireless base station 21. Then, for example, when the mobile station 11 moves to the wireless zone of the wireless base station 22, a request for a handover is made based on the control signal strength or the like.

At this time, the radio base station 21
To the radio base station 22 as the handover destination, and (1) information indicating the new radio base station 22 and (2)
A handover start information cell (s) including information indicating the ATM virtual channel (a ″) established for the mobile station is generated, and the control ATM virtual channel established in advance on the input ATM transmission line 61 is set. Using control station 3
Send to 1.

In FIG. 4, upon receiving the handover start information cell (s) from the input ATM transmission line 61, the cell switch control device 91 of the serving control station 31 uses the ATM virtual channel (a ″) as a key to output the destination table. 121 and the ATM virtual channel (a) of the cell at the time of output and the output A
Know the TM transmission path (73). Note that, regarding the contents of the output destination tables in FIGS. 3, 4, and 5, the description of the virtual channel identifiers (a ′, b ′) at the time of passing through the cell switch is omitted. The cell switch control device 91 routes the handover start information cell (s) to the upstream serving control station or the gateway control station using the control ATM virtual channel established in the output ATM transmission line 73 in advance.

The cell switch control device 91 determines from the information indicating the new radio base station 22 that the path is to be switched within the home control station when switching the route to the new radio base station, and changes the cell addressed to the mobile station 11. Hold. That is, the output destination table 123 is searched using the ATM virtual channel (a) of the cell at the time of input in the input ATM transmission line 63 into which the cell to be routed flows as a key, and the corresponding output ATM transmission line is set to "hold". I do.

Thereafter, the serving control station 31 holds the cells to be route-changed input from the input ATM transmission line 63 in the output hold queue 113. Further, the cell switch control device 9
1 establishes a new ATM virtual channel (b) to be used after the end of handover with the new radio base station 22.

For example, when the handover process is completed via the mobile station 11, the new radio base station 22 stores information indicating the new radio base station 22 and A which is established for the mobile station.
A handover end information cell (e) including information indicating the TM virtual channel (b) is generated and transmitted to the serving control station 31 using a control virtual channel established in the input ATM transmission line 62 in advance.

In FIG. 5, upon receiving the handover end information cell (e) from the input ATM transmission line 62, the cell switch control device 91 of the serving control station 31 uses the ATM virtual channel (b) as a key to output the destination table 122. Search for
ATM virtual channel (a) of cell at output and output ATM
Know the transmission path (73). The cell switch control device 91 outputs the handover end information cell (e) to the output ATM transmission line 73.
Is used to route to the upstream control station or the gateway control station. If it is determined from the information indicating the new radio base station 22 that the route has been changed by the home control station, the ATM virtual channel (a) of the cell at the time of input in the input ATM transmission line 63 into which the cell to be changed flows flows. Is used as a key to search the output destination table 123, and the corresponding output ATM transmission line information is changed from “reserved” to 72. Thereafter, the exchange 31 outputs the cells held in the output hold queue 113 to the output transmission line 72 and outputs the cells to be rerouted input from the input ATM transmission line 63 to the output ATM transmission line 72.

FIG. 6 is a block diagram showing another embodiment of the present invention in which the new radio base station and the old radio base station are connected to different serving control stations. Note that the same components as those in FIG. 1 are given the same numbers. The mobile station 11 communicates with the wireless base station 21 via wireless lines 41 and 51. The wireless base stations 21 and 22 are connected to the serving control stations 31 and 32 and the input / output ATM transmission lines 61 and 71, respectively.
And 62,72. The serving control stations 31 and 32 communicate with the serving control station 33 by input / output ATM, respectively.
Transmission lines 63 (75), 73 (65) and 64 (76),
74 (66). Furthermore, the serving control station 33
Is connected to other control stations or gateway control stations via input / output ATM transmission lines 67 and 77, and it is assumed that a terminating ATM node which is a communication partner of the mobile station 11 exists beyond the control station.

In general, it is conceivable that nm radio base stations are connected to a serving control station having n pairs of ATM transmission lines, and m other serving control stations or gateway control stations are connected. FIG. 6 shows the simplest case.

The serving control stations 31, 32 are ATM nodes (switches) each having the same configuration as the serving control station 31 in FIG. The input / output units 101 to 104 in the serving control stations 31 and 32 each include a flow control module, an output hold queue, and an output destination table.

Next, the operation of the second embodiment will be described with reference to FIGS. The radio base stations 21 and 22 form an adjacent radio zone, and initially the mobile station 11
, But handover is performed when moving to the wireless zone of the wireless base station 22. At this time,
The radio base station 21 instructs the mobile station 11 to make the handover destination the radio base station 22,
, And a handover start information cell including information indicating the ATM virtual channel established for the mobile station.
It transmits to the serving control station 31 using the TM virtual channel.

FIG. 7 is an explanatory diagram showing a cell reserved state in the second embodiment. Upon receiving the handover start notification cell from the input ATM transmission line 61, the cell switch control device 91 of the serving control station 31 searches the output destination table 121 using the ATM virtual channel (a ″) as a key, and searches for the virtual cell at the time of output. The cell switch control device 91 routes the handover start notification cell to the serving control station 33 by using the control ATM virtual channel established in the output ATM transmission line 73 in advance. At the same time, when switching the route from the information indicating the new radio base station 22 to the new radio base station, it is determined that the information does not pass through the home control station 31, and no special processing is performed. Are kept until they reach the mobile station 11.

Upon receiving the handover start information cell from the input ATM transmission line 65, the cell switch control unit 93 of the serving control station 33 searches the output destination table 125 using the ATM virtual channel as a key, and outputs the ATM of the cell at the time of output. Know the virtual channel and output ATM transmission path (77). The cell switch control device 93 outputs the handover start information cell to the AT.
In addition to routing to an upstream station using a control ATM virtual channel established in advance in the M transmission line 77 and switching the path from the information indicating the new radio base station 22 to the new radio base station, the current control station is used. It is determined that the route is to be switched within the network 33, and the same operation as that of the serving control station 31 in the first embodiment is performed to suspend the transfer of the cell addressed to the mobile station 11.

Thereafter, the serving control station 33 holds the cell (a) to be route-changed input from the input ATM transmission line 67 in the output hold queue 117. Further, the cell switch control device 93 transmits the new radio base station 22 via the serving control station 32.
Until the end of the handover, a virtual channel to be used after the handover is established.

When the handover is completed, the new radio base station 22 generates a handover end information cell including information indicating the new radio base station 22 and information indicating the ATM virtual channel established for the mobile station. It transmits to the serving control station 32 by using a control virtual channel established in the input transmission line 62 in advance.

The cell switch control device 92 of the serving control station 32 that has received the handover completion notification cell from the input ATM transmission line 62 searches the output destination table 122 using the virtual channel as a key, and searches the output destination table 122 for the virtual channel of the cell at the time of output. Output A
Know the TM transmission path. The cell switch control device 92 transmits the handover end notification cell to the output ATM transmission line 74 by using a control virtual channel which has been previously established.
Route to

Upon receiving the handover completion notification cell from the input ATM transmission line 66, the cell switch control unit 93 of the serving control station 33 searches the output destination table 126 using the ATM virtual channel as a key, and searches for the virtual channel of the cell at the time of output. And the output ATM transmission line (77). The cell switch control device outputs the handover end notification cell to the output ATM transmission line 77.
, And when it is determined from the information indicating the new radio base station 22 that the route has been changed by the home control station, the output ATM transmission line 77 and the virtual channel (a) of the cell at the time of output, that is, The output destination table 127 is searched using the virtual channel (a) of the cell at the time of input in the input ATM transmission line 66 into which the cell to be routed flows as a key, and the corresponding output ATM transmission line information is changed from "reserved" to 76.
And Thereafter, the serving control station 33 outputs the cells held in the output hold queue to the output transmission line 76, and outputs the cells to be rerouted input from the input ATM transmission line 67 to the output transmission line 76.

Note that the routed handover start notification cell and handover end information cell are the mobile station 1
The data is sequentially transferred via the serving control station or the gateway control station to the terminating ATM node that communicates with No. 1. Then, each ATM node determines the station to be switched from the contents of the handover start notification cell, and does nothing when switching is performed at a higher level than the own station. When the process is performed and the switching is performed in a station lower than the own station, only the reservation of the cell is performed.

[0036]

As described above, according to the present invention, the radio base station transfers the handover start information from the neighboring serving control station or gateway control station to the end node one after another by the handover start notification cell. By suspending cells and disabling cell transmission at the end node, cells can be suspended in a smaller output suspension queue compared to suspending all cells at the switching station, preventing cell loss during handover There is an effect that can be.

Further, a simple notification mechanism using a handover start information cell and a handover end information cell, and an AT virtual channel identifier used for input to an ATM node,
By providing an output destination table having a structure capable of searching for the ATM virtual channel identifier and the output ATM transmission line information when outputting from the M node, there is an effect that high-speed handover processing can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a serving control station according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a mobile communication network to which the present invention is applied.

FIG. 3 is an explanatory diagram illustrating a flow control operation in an ATM node.

FIG. 4 is an explanatory diagram illustrating a flow control operation in an ATM node.

FIG. 5 is an explanatory diagram illustrating a flow control operation in the ATM node.

FIG. 6 is a block diagram showing a configuration of another embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a cell reserved state in the second embodiment.

FIG. 8 is an explanatory diagram showing a state after switching in the second embodiment.

[Explanation of symbols]

11: mobile station, 21, 22 ... radio base station, 31, 32,
33: control station in service area, 41, 42: input wireless transmission path, 5
1, 52 ... output wireless transmission path, 61, 62, 63, 64,
65, 66, 67 ... input ATM transmission lines, 71, 72, 7
3, 74, 75, 76, 77 ... output ATM transmission line, 8
1, 82, 83 ... cell switch, 91, 92, 93 ... cell switch control device, 101, 102, 103, 10
4, 105, 106, 107 flow control modules,
111, 112, 113, 114, 115, 116, 1
17: output hold queue, 121, 122, 123, 12
4, 125, 126, 127 ... output destination table

Continued on the front page (72) Inventor Yoneo Watanabe 1-132 Shinurashima-cho, Kanagawa-ku, Yokohama-shi, Kanagawa-ken Inside YRP Co., Ltd. Mobile Communication Technology Research Laboratories (72) Inventor Motoharu Tanaka Kanagawa, Yokohama-shi, Kanagawa 1-32 Shinurashima-cho, Ward WIP Corporation Mobile Communication Technology Laboratories (56) References JP-A-8-46643 (JP, A) JP-A-6-30466 (JP, A) Kaihei 4-10720 (JP, A) JP-A-6-30460 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 7/24-7/26 H04L 12/00- 12/28 H04Q 3/00 H04Q 7/00-7/38

Claims (5)

(57) [Claims] A mobile station passes through one or more ATM nodes established between a wireless base station in which the mobile station is currently located and an ATM node to which a communication partner device of the mobile station is connected. In a mobile communication network that performs communication via an ATM virtual channel, (1) when a mobile station moves to a wireless zone of another wireless base station, an old wireless base station transmits an ATM node to the ATM node via the ATM virtual channel; Transmitting handover start information. (2) At least one of the ATM nodes that performs a path switch, based on the handover start information, an AT into which an ATM cell for the mobile station flows.
Identifying M transmission paths and ATM virtual channels. (3) At least one of the ATM nodes that performs a route switch, the AT for the mobile station.
Suspending the switching of the M cell and temporarily storing the cell. (4) transmitting handover completion information to the ATM node through which the virtual channel from the new radio base station to the new radio base station passes when the handover is completed. (5) A step of specifying, from the handover completion information, an ATM transmission path into which an ATM cell flows and an ATM virtual channel in the ATM node that has held the ATM. (6) A step of releasing the hold and sending out the stored ATM cells at the ATM node that has held the hold. A flow control method comprising: 2. A wireless base station which is the lowest station and a plurality of ATM nodes having a hierarchical structure which are present above the wireless base station are connected by an ATM transmission line, and are connected to a wireless base station in which a mobile station is located. In a mobile communication network performing communication via an ATM virtual channel established with an ATM node accommodating a communication partner of a mobile station, (1) when a mobile station moves to a radio zone of another radio base station, A step of transmitting handover start information including new radio base station information after the handover and ATM virtual channel information established for the mobile station to be handed over from the old radio base station requesting the handover to the upper station. (2) A step of, in the upper station, specifying an ATM transmission path into which an ATM cell flows and an ATM virtual channel from the handover start information. (3) a step of suspending the switching of the ATM cell to the mobile station and storing the cell in the upper station. (4) transmitting, when the handover is completed, handover end information including the new radio base station information and the ATM virtual channel information newly established for the mobile station to which the handover has been performed, from the new radio base station to the upper station; . (5) From the handover end information in the upper station,
A step of specifying an ATM transmission line into which an ATM cell flows and an ATM virtual channel. (6) A step of releasing the hold of the switching of the ATM cell in the upper station. A flow control method comprising: 3. An output hold queue provided in an ATM transmission line of each ATM node for sequentially transferring handover start information and handover end information between ATM nodes up to a terminal ATM node through the ATM virtual channel. 3. The flow control method according to claim 1, wherein the cells are distributed and held. 4. ATM for input to each ATM node
It has a data structure capable of retrieving an ATM virtual channel identifier and output ATM transmission line information when outputting from each ATM node from the virtual channel identifier, and for each input ATM transmission line, a flow control module, a cell switch, and a cell switch control. 4. The flow control method according to claim 1, wherein an output destination table that can be referred to by the device is used. 5. A mobile communication network having a flow control function for executing the flow control method according to claim 1.