JP2960365B2 - Handoff method and mobile communication network with handoff function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handoff method and a mobile communication network having a handoff function, and is regarded as a promising means for realizing multimedia communication.
The present invention relates to a handoff method and a mobile communication network having the functions in an ATM mobile communication system including a TM communication system exchange, a communication link connected between the ATM exchanges, a base station connected to the ATM exchange, a mobile terminal, and the like. It is.

2. Description of the Related Art In a conventional mobile communication system (PHS, cellular phone), an exchange for controlling a call connection with a mobile terminal receives a request to change (hand off) a radio base station from a moving mobile terminal. Or receives a handoff request by monitoring the radio power intensity of a base station that is performing radio communication with a mobile terminal, and maintains a call (connection) connection. In the conventional connection maintenance method, a mobile connection control device is connected to a terminal exchange, and handoff is realized only between base stations connected to the device, or a connection is extended when handoff is performed between exchanges. Stayed connected. On the other hand, an ATM network is a promising communication method for realizing multimedia communication.
The mobile communication in the M network is PVC [: Permanent Virtual Circuit] which is a predetermined connection route.
SVC [: Switched Virtual Circuit] which can connect the connection freely only by studying the method of maintaining the connection at the time of handoff by selecting
Mobile communication using is not realized.

When the conventional mobile communication system is applied to an ATM network, the following problems occur. First, high-speed communication must be performed in multimedia communication, and a broadband frequency, that is, a high radio frequency must be used. For this reason, as a first problem, the area of the wireless area that can be covered by one wireless base station is reduced, and the overlapping part of the adjacent wireless area is reduced, so that the time required for selecting the wireless base station of the handoff destination Has to be shortened. Also, as a second problem, since it is necessary to hand off a broadband connection, if the connection connection is maintained by using the connection extension method, link resources between ATM exchanges are wasted, and the number of connections that can be connected is reduced. There is a problem of reduction. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, reduce the time required for selecting a handoff destination, and effectively use a network resource at the time of handing off a connection with a large bandwidth. And a mobile communication network having a handoff function.

In order to achieve the first object, in the ATM mobile communication system of the present invention, a mobile communication system including an ATM switch, a link between the ATM switches, a radio base station, and a mobile terminal. , When the mobile terminal enters the destination wireless area, information such as the address of the ATM switch to which the destination (next) wireless area is connected and the handoff request are sent to the current wireless base station. Send to ATM exchange. The currently connected ATM switch connects the spare connection to the next ATM switch.
The connection of the connection requires the other terminal, but since the connection must be connected to the ATM exchange that has not been handed off yet, each ATM exchange has a pseudo terminal, and the pseudo terminal has a spare terminal. Connect the connection. In addition, in the spare connection, a plurality of connections can be made in an area where a plurality of wireless areas overlap. Next, when the mobile terminal further approaches the next radio base station and the radio power from the current radio base station is weakened, the mobile terminal issues a data stop request and a connection connection request to the currently connected ATM exchange, A currently connected
The TM exchange requests a radio frequency from the next connected ATM exchange, and transmits this frequency to the mobile terminal. In addition, another standby connection disconnection request not to be connected is issued, and the conventional connection and the standby connection to be used are connected so that the connection is connected to the next ATM exchange. At this time, since each connection is connected to the same link in the opposite direction in some cases, the call reference which is the connection number is set to a different value, and a call reference conversion table is provided in the ATM exchange. To convert. Finally, the mobile terminal switches the radio frequency, issues a data transmission start request, and completes the handoff. In order to achieve the second object, in the ATM mobile communication system of the present invention, when a mobile terminal enters a destination wireless area in a mobile communication system, a destination (next) wireless area is connected. The information such as the address of the ATM exchange and the handoff request are transmitted to the handoff control station (exchange). In addition, the handoff control station checks the
Link information is collected from the M exchange, and the optimum route between the mobile terminal and the partner terminal with which the mobile terminal is communicating is calculated from these used bands. This optimum route can be calculated using, for example, the Dijkstra method or the Warshall method. Next, the handoff control station compares the route of the current connection with the route of the optimal connection, and issues a backup connection connection request to an ATM switch (switching switch) where a difference in the route starts to occur. A plurality of backup connections can be provided in the same manner as the above connection extension method, and each ATM exchange is provided with a pseudo terminal in order to realize the backup connection. Next, when the mobile terminal further approaches the next radio base station and the radio power from the current radio base station is weakened, the mobile terminal issues a data stop request and a connection connection request to the handoff control station, and the handoff control station switches the switching equipment. To the ATM to which the mobile terminal will move next, while making a connection connection request to the
It requests a radio frequency from the exchange and communicates this frequency to the mobile terminal. In this case, since the same connection does not pass through the same link, the call reference is unified when these connections are connected by the switching equipment. Finally, the mobile terminal switches the radio frequency, issues a data transmission start request, and completes the handoff.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
The embodiment will be described in detail. FIG. 1 shows the application of the present invention.
Showing a configuration of a mobile communication network which is an example of a communication network to be used.
It is a lock figure. The mobile communication network 1 has an ATM exchange
Exchanges 10-15, communication links between ATM exchanges, connectors
Hand to control handoff in the
Dooff control station (exchange) 11, in wireless areas 30-32
It consists of the corresponding radio base stations 16 to 18, the mobile terminal 19, etc.
You. Each of the ATM exchanges 10 to 15 communicates with the destination of the mobile terminal.
Connect a virtual communication line to a possible ATM switch
Simulates the role of mobile terminal when connecting an application
Terminals 20 to 24 are provided. Also, each ATM exchange
The output communication link connection has an output buffer.
You. The mobile terminal 19 is, for example, a fixed network.
The connection 33 is connected to the partner terminal 3 via
It is assumed that you are trusting. Connection in the embodiment
33 is a well-known ATM forum UNI (User-Net
work Interface), and this connection
The order is shown in FIG. 2 and the format of the ATM cell is shown in FIG.
Format of the data stored in the payload of the control cell
The plot is shown in FIG. Hereinafter, a general call connection based on FIG.
The connection control procedure will be described. Connection requesting connection
The calling terminal uses the payload, which is the user information part of the cell.
In the (PayloadUser Information) section, "Call setting" in Fig. 4
(Hereafter, the angle brackets indicate the cell of the name.)
And the cell is transmitted via the ATM exchange to the called terminal.
To reach. Each ATM exchange receives "call setup"
At that point, the received "call setting accepted" is returned.
The callee accepts this "call setup" and establishes a connection.
A "response" is sent back to the calling party. The calling party
When this "response" is received, "response confirmation" is returned and the connection
The action is established and communication is started. Communication ends,
To release the connection, select "Release
Release) to the other party, and when the other party receives it,
"Release complete" is sent back to release the connection. What
Please note that this connection release is not limited to terminals.
Can also be released from the ATM exchange.
Send "Release" in direction (caller and callee). Of FIG.
The procedure is for fixed communication, and this method is suitable for mobile communication.
To respond, it is necessary to solve the following two problems.
First, it is necessary to manage the location of the mobile terminal. This
This is not necessary when the mobile terminal is the caller,
This function is required when becoming the caller, and the location of the mobile terminal
For managing ATMs and specifying the ATM switch that is the final connection destination
Noh. However, make sure that the mobile terminal is always the caller.
This feature is no longer needed. That is, the mobile terminal
If you want to communicate with
Broadcast call request like bell (all A
Broadcast to the TM exchange) and call from the mobile terminal.
It will be good. Second, if the mobile terminal 19
When crossing 0 to 32, the radio base corresponding to this radio cell
Switch between base stations 16 to 18 and move
AT to track mobile terminals, ie, perform handoff
Extend or switch connection between M exchanges 10-15
Need to be Therefore, the connection connection of the UNI is required.
It is necessary to add new functions to the connection procedure and the ATM switch.
You. In the following, the connection of the handoff
The connection control will be described. First, connection extension method
Will be described. In FIG. 1, the mobile terminal 19 is
When moving to the area 31 corresponding to the exchange B14
Is connected from the current exchange A13 to another exchange B14.
Connection and add it to the current connection 33.
Return the connected connection to the current exchange A13
Then, the connection with the mobile terminal 19 is established. Mobile terminal 19
Is moved to another area 32, the connection
Connection, and use that connection to establish a connection.
Do. This method requires a connection every time the mobile terminal moves.
This is called a connection extension method because additional connections are made.
Next, a connection switching method will be described. Move
When the terminal 19 moves to the area 31, the connection
The mobile terminal side from the exchange C10 of the switch 33 to the exchange B14.
Switching and communication with the mobile terminal 19 are performed. In addition, other mobile terminals
Is moved to the area 32 of the connection 33,
The mobile terminal side from the exchange C10 and the exchanges 12 and 15
Connection to the mobile terminal 19 and communicate with the mobile terminal 19.
U. The location and route of the exchange that switches the connection
The designation is performed by the handoff control station 11. In this scheme,
The connection is switched every time the mobile terminal moves.
This is called a connection switching method. Hereafter, connection
Extension method, connection switching method and connection
Details about the handoff control station used in the
This will be described in detail. FIG. 7 illustrates the connection extension method.
FIG. The same numbers as those in Fig. 1
No. is attached. Area 30 receives radio waves from base station 16
Wireless area. D provided inside the wireless area 30
It is assumed that good communication is possible in the rear 40 and 41.
You. Each radio base station 16 and 17 has its own radio area.
A of the ATM switch connected to the identification number of the wireless base station
The TM address is flowing. For example, in the wireless area 30
Is the identification number of the wireless base station 16 and the ATM exchange A13.
ATM address (to be described later, actually, ATM exchange A
13) and the pseudo terminal 22 connected to the
I have. Now, the mobile terminal 19 is in the area 40 → 41 → 42 →
Handoff from mobile terminal 19 when moving to 43
The request and the actual connection are explained based on FIG. 7 and FIG.
I will tell. When the mobile terminal 19 exists in the area 40
The mobile terminal 19 is communicating with the base station 16 by radio.
The mobile terminal 19 is located in the area 41, that is, the adjacent radio base station 1.
7 moves to the area where radio waves reach
4 to the ATM exchange A13.
Handoff request ”(HANDOFF REQ FROM MT)
(S1 in FIGS. 7 and 10). ATM handoff request
Format is the same as the format of the “call setup”.
You. The mobile terminal 19 receives the “handoff from mobile terminal”.
In the “Called party address” part of the “request”, the radio base station 17
Address of ATM switch B14 to which is connected
And send. ATM receiving handoff request
Exchange A13 is preferably a connection extension method,
It is determined whether the connection switching method is desirable. Judgment base
As standard, connection time is short, like a mobile phone, and
Connection if the bandwidth used by the connection is small
Uses the extension method, and switches when the bandwidth is large.
Is adopted. Because the connection switching method is
We do not waste links as network resources,
When the bandwidth used is small and the number of handoffs is small
The connection extension method has fewer control cells,
This is because it is suitable for a hand-off connection control method. here
Indicates that the connection extension method has been selected (S
2). ATM switch A that has received the "handoff request"
13 controls the mobile terminal 19 for handoff request control.
"Handoff acceptance" is sent as the reply that started. this
The cell format is shown in FIG.
In the expression section, the mobile terminal is notified of the handoff control method.
You. A system that uses only the connection extension method
Then, the "hand-off method" section is unnecessary (S3).
ATM switch A13 reserves for ATM switch B14.
Perform "call setting" of the connection. Backup connection
Can be connected multiple times and multiple wireless cells overlap
If you move to the area where
Is connected to the backup connection (S4 to S7).
The backup connection will be further described with reference to FIG.
You. In this example, the mobile terminal 19 is a wireless base station in the wireless area 40.
Communication via the office 16 and the ATM switch 16
This is the state immediately after entering the wireless area 43. General
When setting up a connection,
The mobile terminal is not communicating in the next wireless area.
State, connect the connection to this mobile terminal
I can't do that. In this example, the mobile terminal 19 has an ATM switch.
Sends a hand-off request to switch A13 and exchanges ATM
Machine A13 sends "call setup" to ATM exchange B14.
I'm trying. Therefore, the pseudo terminal 2 is connected to each ATM exchange.
2 and 23, and "call setup" for this pseudo terminal
Send it. Then, it is not communicating with the mobile terminal
The standby connection can be connected even in the unattended state.
Returning to FIGS. Backup connection
When the connection is completed, the ATM exchange A13 sends a message to the mobile terminal.
Sends a "handoff request confirmation" notification. Figure 6 shows self
The format is shown (S8). Next, the mobile terminal 19
A, the communication via the wireless base station 17
To start, stop the data and switch to ATM switch A13.
For "request for connection of spare connection from mobile terminal"
Is sent. FIG. 5 shows a cell format. The four
The identification number of the wireless base station with which you want to communicate on the mat
Want to connect a connection to the “BS node number”
New ATM switch address (pseudo terminal address)
It is sent out in the "ATM address" part (S9). AT
The M exchange A13 sends a "handoff acceptance" to the mobile terminal 19.
Is returned, and a spare connection to exchange A13 is used.
To exchange B14 via exchange C10.
And sends a “preliminary connection connection request”. This self
The format is shown in FIG. Each contact receiving the request cell
The exchanges 10 and 14 each return "call setting acceptance".
(S10). The exchange B14 that has received the cell,
Releases the connection to terminal 23 and disconnects
Switch to line base station 17. In addition, exchange B14 moves.
Prepare the radio frequency to communicate with the terminal, and
Uplink to base station 17 in the "Uplink frequency" section of
Frequency of the downlink line from the base station to
And send it out in the "frequency" section (S11). ATM exchange
When the machine A13 receives the "preliminary connection confirmation",
Connection and the connection to exchange B14
Connection and multiple backup connections
, Release unused spare connections
(S12). Switch A13 connects to mobile terminal
And the frequency used in the wireless area 43
Notification of backup connection to mobile terminal ".
This cell format is shown in FIG. 5 (S13). Spare connector
The operation connection part will be described in detail. FIG.
Connections used and spare connectors to be used
Explains the connection procedure of the application. ATM switch A1
3 is an internal call reference (call reference number) conversion table.
Bull 45 is provided. ATM switch B14 displays
Exchange request is received, the exchange
Prepare a radio frequency for communication with the
To the exchange A13 by using "confirmation of the exchange". It
At the same time, the connection between exchange B14 and pseudo terminal 23
Release the connection and extend the connection to the wireless base station 17.
When the "preliminary connection confirmation" returns, the exchange A1
3 notifies the mobile terminal 19 of the frequency and the like, and
The middle connection and the backup connection are connected. Figure
9, the same link between exchange A13 and exchange C10 is used.
There are outgoing and returning connections on the network. here
And the call reference, which is the connection number, is the same.
In the case of 1, the connection classification cannot be performed by the exchange C10.
Become. Therefore, the old connection and the new connection added
The call reference is changed in the
Number of the connection in the rule reference conversion table 45
Signal conversion. For example, the call reference of the old connection
Set the reference to 1 and call reference for the new connection
Is 2, the call reference conversion stable is used.
And 1 and 2 are mutually converted. 7 and 10 again
Will be explained. If the mobile terminal says "Preliminary connection to
Received from the exchange A13,
Switch to the line frequency (S14),
Send "off done" notification. Figure 5 shows this cell format.
(S15). Finally, the mobile terminal 19 displays "Hand
Handoff control is completed
(S16). FIG. 11 illustrates the connection switching method
FIG. 14 is a block diagram showing the connection.
FIG. 9 is an explanatory diagram showing a handoff procedure in the switching method.
You. In FIG. 11, the same parts as those in FIGS.
Is attached. Each of the ATM switches 10, 13, and 14 is
To the switch-off control station (exchange) 11 for use of each link.
ATM cells in the output band of the ATM switch
The product amount is constantly transmitted using “link information”.
This cell format is shown in FIG. Now, if the mobile terminal
When moving to the rear 40, 41, 42, 43,
Handoff request from the mobile terminal 19 and the actual connection.
This will be described with reference to FIGS. If the mobile terminal 19
When present in the rear 40, the mobile terminal
Communicating wirelessly. The mobile terminal moves to area 41
That is, when moving to a portion overlapping with the wireless area 43,
Via the base station 16 to the ATM exchange A13,
"Handoff request from mobile terminal" is sent. This hand
FIG. 4 shows the ATM cell format of the off request. Move
The terminal sets the radio base in the "Called party address" part of this cell.
ATM of ATM switch B14 to which the base station 17 is connected
The address is entered and transmitted (S21). Handoff request
Exchange A13 receives the connection extension
Is preferred or connection switching is preferred
Judge. Here, select the connection switching method
(S22). Receive handoff request
ATM switch A13 sends a handover to mobile terminal 19.
As a response to the start of the handoff request control,
Send "with". This cell format is shown in FIG. The cell
Handoff system for mobile terminals
Notify the control method. Note that only the connection switching method is used.
The “hand-off method” section is unnecessary for systems that do not use
There is (S23). ATM switch A13 is hand-off system
Send a “handoff request” to your station 11. This selfie
The mat is shown in FIG. 4 (S24). "Handoff request"
Handoff control station received is processing handoff request
Is sent back (S25). Continued
The hand-off control station 11 is in charge of each ATM exchange.
Off Based on the "link information" transmitted to the control station,
Calculate the optimal route from the terminal to the exchange B14 and connect
Notify exchanges that need to switch applications. Handoff
Control within the control station will be described later with reference to FIGS.
Will be described. In the example of FIG. 11, switching is performed by the exchange C10.
And the handoff control station 11 exchanges
A route is designated for machine C10,
Issues a "call setup request" requesting a connection. Book cell former
The plot is shown in FIG. "SwATM address" part of the cell
ATM switch of ATM switch to connect to
Address and the output port information of the exchange in the "port" section.
Put in and send. This cell may be multiple cells
(S26). Switch C10 that has received the "call setup request"
Indicates to the handoff control station 11 that "call setting has been accepted"
Is sent (S27). Subsequently, the exchange C10 is switched to the exchange B1.
4, a "call setting" of the backup connection is performed. Reserve
Multiple connections are possible, and multiple wireless cells
If you move to the overlapping area,
Connect a backup connection to the ATM switch (S
28-S30). FIG. 12 shows the backup connection.
This will be further described below. In this example, the mobile terminal 19
A via the wireless base station 16 and the ATM switch A13
Immediately after entering the wireless area 43 while communicating
It is a state of. In this example, ATM switch C10 is an AT switch.
Connection of a spare connection to the M exchange B14, that is, "call setup"
In such a case, each ATM
The exchange has pseudo terminals 22 and 23, and this pseudo terminal
"Call setting" is transmitted to it. Like this
If it is not in communication with the mobile terminal,
A spare connection can be connected. Figure 1 again
Description will be made returning to 1,14. The backup connection is connected
At the end, the ATM switch C10 switches to the handoff control station 11
Send "call setup request confirmation" to This cell format
This is shown in FIG. 4 (S31). When the handoff control station 11
Received a handoff request, the
A "hand-off request confirmation" notice is sent to the exchange A13. this
FIG. 6 shows the cell format (S32). Exchanger A1
3 receives the “handoff request confirmation”,
"Confirm handoff request to mobile terminal" is sent. This cell
The format is shown in FIG. 6 (S33). Next, the mobile terminal
Moves to the area 42 and passes through the radio base station 17.
To start communication, stop sending data and use ATM
Switching end to ATM exchange B14 for exchange A13
From the end of the connection. this
FIG. 5 shows the cell format. In the cell,
Enter the identification number of the wireless base station you want to
ATM switch to which you want to connect the connection
Address (actually, the pseudo terminal address) is "ATM
It is sent in the "address" part (S34). ATM exchange
The machine A13 reads “Need to connect a spare connection from the mobile terminal.
Request, the hand-off control station 11 receives a "reserve connection".
(S35). Handoff control
The office 11 switches to the exchange C10 which actually switches the connection.
Sends a "reserve connection connection request"
A connection request is made (S36). Also, multiple spare connectors
If you have connected an
Release the action. Subsequently, the ATM exchange C10
Is the spare connector to exchange B14.
In order to use the
Request ”. Further description of the connection procedure will be described with reference to FIG.
It will be described later. The cell format is shown in FIG.
7). The exchange B14 that has received this cell sends the pseudo terminal 2
Release the connection to 3 and change the connection to the radio base
Switch to station 17. The exchange B14 is the mobile terminal 1
9 and prepare the radio frequency to communicate with
Confirmation ”(Fig. 5) in the“ Uplink Frequency ”section.
And the frequency for communication from the base station
Into the "down-link frequency" section, and exchange C10, exchange A
13 (S38). ATM switch C10
If you receive a "preliminary connection confirmation"
ATM switch C10 to ATM switch A13
Connection of ATM and exchange from ATM switch C10
The backup connection to the device B14 is connected (S3
9). Switch A13 connects to mobile terminal 19
When the completion, the frequency used in the wireless areas 42 and 43 is
The notification is made using “confirmation of backup connection to terminal”. Book
FIG. 5 shows the cell format (S40). FIG.
Previously used connections and spares to be used
FIG. 9 is an explanatory diagram showing a connection procedure of a connection. First,
The handoff control station 11 sends a “reserve connection connection request”
Is received, the exchange C10 is notified that "preliminary connection connection
Exchange C10, and exchange C10
Connection 52 and unnecessary connection 51
"release. The ATM switch C10 is an ATM switch.
Sends a “preliminary connection connection request” to the device B14. AT
M exchange B14 receives the "reserve connection connection request"
In this case, the exchange uses a wireless communication for communication with the mobile terminal 19.
Prepare the frequency and use "Preliminary connection check"
Notify exchange A13. At the same time, exchange B14
And release the connection between the pseudo terminal 23 and the radio base station.
Extend the connection to 17. The exchange A13 is "Reserve
When "connection confirmation" is returned from exchange B14,
The mobile terminal 19 is notified of the frequency and the like. The example of FIG.
Connection switching, so after connecting a new connection, connect
Call reference for connection 50 and connection 51
Can be the same number. This allows connection extension
The call reference conversion table needed for the expression is not
It becomes important. However, similar to the connection extension method,
Transform without changing the call reference of the new connection
You can have a table. Return to FIGS. 11 and 14 again.
I will explain. If the mobile terminal says `` Spare connection to mobile terminal
Is received from exchange A13
Switching to the radio frequency (S41), the exchange B14 displays
Dodge completion "notification. Diagram of this cell format
5 (S42). Finally, the mobile terminal 19 displays “Hand
Handoff control is completed
(S43). The handoff control station disconnects
ATM switch used in the switching system
It is different from other ATM exchanges used in this patent.
There is no. However, the connection at the time of handoff is controlled.
Processing and some tables have been added
You. This will be described with reference to FIGS. The above connection
As described above, each ATM exchange is
Use the link bandwidth and output buffer cell storage
Using the “link information” cell to communicate to the handoff control station 11
I know. FIG. 6 shows this cell format. Each exchange
The timing at which the exchange sends this cell is for a fixed time.
Changes in bandwidth or the number of stored cells at intervals or links
Can be sent out when is greater than or equal to a predetermined value. one
When sending at regular intervals, shorten the sending time interval.
The more real-time information you get, the more
This can be detected before congestion occurs in the system. That is, Han
Dooff control station connects connection before congestion occurs
You can do it again. However, if this time interval is short,
The higher the number, the greater the number of ATM switches
The number of "link information" cells in the network
Increases, and network resources are wasted. This time
Adjusting the interval depends on the traffic in the network,
It must be performed by various parameters such as moving speed and communication time.
It is necessary and difficult to adjust. On the other hand, the bandwidth used for each link
Or the change in the number of cells stored in the output buffer,
How to send out the "link information" cell depends on the use of each link
Each time the bandwidth and output buffer increases or decreases
Output the file. For example, the maximum bandwidth of each link
Is set to 155Mbps every time the bandwidth of 5-10% increases or decreases
Send out a "link info" cell. Then, especially used
"Link information" is not sent from parts that are not
To collect necessary information when needed.
Become. In the embodiment, based on a change in the band used or the amount of stored cells,
To send the "link information", and link information table 6
It is assumed that a method of updating the information of 0 is adopted. FIG.
Indicates a route determination process in the handoff control station 11.
It is a flowchart. The handoff control station is a mobile terminal
From the "handoff request" (or "call setup")
Then, the processing of FIG. 15 is started. In S50,
From the link information table 60.
Receives the amount of cells stored in the power buffer and the cost of each link
Is calculated. In this embodiment, handoff will be described.
However, it may adapt to the "call setup" at the beginning of the connection.
it can. The link cost is calculated, for example, as shown in FIG.
This is done by the following formula. At this time, the communication service
Quality requirements for connection (QoS: Qualityo)
f Service) changes the cost. The reason
Is the lowest cost from only the currently used and requested bandwidth
After calculating the route, various routes such as audio, video, data, etc.
QoS connection simultaneously from the same location in the same direction
If so, will everyone adopt the same route?
It is. In addition, cell delay may increase or congestion may occur.
, Everyone tries to take another route at the same time. At this time
Each QoS connection takes a different route
Link cost is the same for any QoS
This is because the same route is taken. Kostlin
The current calculation method is used as a parameter.
Used bandwidth of the link being used, accumulated in the output buffer
Use the number of cells and the required bandwidth of the connection. this is,
Basically make it possible to select a route that uses less bandwidth
Use bandwidth usage information of the link for strict delay requirements
In the case of connection (QoS), reduce cell delay
In consideration of the number of cells stored in the output buffer,
Accumulation in the buffer will cause delays), request band
No impact on bandwidth used for connections with a small bandwidth
So use as much of the link bandwidth as possible
This is to reduce the number of ATM exchanges. Re
An example of the link cost calculation formula is shown in FIG. This expression
Where A = maximum value of link cost, B is 0 <B <1,
Parameters approaching 1 as QoS delay requirements become more stringent
It is. Calculating the formula, the link cost is shown in FIG.
The required link cost can be calculated.
You. FIG. 17 (a) shows the used band for each series having a different required band.
It shows the relationship between the area and the link cost.
The number of cells stored in the output buffer is not considered (B =
0). 17 (a) for link cost calculation
If used, connections with large requested bandwidths
Link, which requires less bandwidth.
Connection requires fewer ATM switches
You. FIG. 17B illustrates an example (B) in which the number of storage cells is considered.
> 0), and the number of stored cells is proportional to the used band of the link.
Is assumed to increase. The series 3 in FIG.
Qo with small reserved bandwidth and strict delay requirements like voice
S. In the case of QoS such as voice, FIG.
As can be seen by comparing with the series 1 in (a), the cell accumulation amount
The bandwidth used, even if the required bandwidth is small.
As the number increases, the link cost also increases,
Even though the cell storage amount is small, that is, switching with a small cell delay
Via the machine. Series 4 is like data,
This is QoS with a large bandwidth and a low delay requirement. FIG.
Compared to series 2 in (a), there is little difference.
Call Returning to FIG. 15 again, in S51, the hand
Calculate the minimum cost route of the off destination communication route. This minimum
The cost route calculation method will be described later. In S53
The calculated minimum cost and the current connection
AT that actually switches connections compared to the road
Determine the M exchange. Note that this process is performed during “call setup”.
Skip. The route information of the current connection is route information
It is stored in the table 61. This route information table
The writing to 61 is performed at the time of “call setting” (S58),
When the action is actually switched (S62 in FIG. 16)
U. In S54, the backup connection (“call setting”
Switch to make a formal connection)
Switch (the mobile terminal at the time of "call setup")
Send "Request". In S55, this connection
Determines whether the connection was successful,
In the case of success, the process shifts to S58 and the route table 61
Write the road. S59 if the backup connection is successful
And sends a "handoff request confirmation" to the mobile terminal.
If the connection is unsuccessful, the process proceeds to S56, where
In the above equation, B is changed,
The process moves to 51, and the calculation of the minimum cost route is tried again. Next
Figure about processing when actually switching connections
16 will be described. This control is performed by the handoff control station.
Opened when a “reserve connection request” is received from the mobile terminal.
Begun. In step S60, the exchange performing the switching
To instruct connection switching processing (FIG. 13)
Issues a “preliminary connection request” at S61
Are the old connections and their
Disconnect the other spare connection to the respective exchange.
Show. In S62, the connection route information
After updating the table 61, the process ends. Next, about the minimum route calculation
Will be described. Conventionally known route selection methods include the shortest route
The problem is how to search from one node to any node
Method (distributed processing) and a search method between arbitrary nodes (centralized processing)
Reason). The former is the Dijkstra method, the latter
Is famous for the Warshall method, and the total number of nodes
Is m, the order of the number of calculations is (m
Squared) and (m3). Each
These algorithms are well known and will not be described.
Also, the cost of each link is required to perform these calculations.
Necessary, the Dijkstra method transfers cost information to all nodes.
To the central control node in the worst case method.
You. Looking at the whole network, this traffic is the former
Are [(m-1) squared] cells, and the latter is m cells. Total
As for the number of calculations, the Dijkstra method is advantageous, but
For the number of control cells in the
Become. In the present invention, the number of control cells is reduced as much as possible.
Use the centralized processing method, the worst-case method.
You. In addition, the worshall method has been improved,
So that it can be used even when the downlink bandwidth is different.
You. By the means described so far, the ATM network
Support mobile handoff
it can. Note that the present invention is not limited to an ATM network.
Communication using any method that establishes a connection
Applicable to connection switching control in networks
You. In particular, in the case of the switching method, avoid congestion and obstacles.
It is also possible to move connections between fixed terminals for
Become.

As described above, according to the present invention, when the mobile terminal moves beyond the wireless area and needs to switch the ATM exchange, the connection having a small required bandwidth uses the extension method, By using the switching method for connections having a large bandwidth, there is an effect that resources can be effectively used even when connections of various bandwidths are connected. Further, since a backup connection can be established to a plurality of exchanges which may move using the pseudo terminal, there is an effect that connection to the next base station at the time of handoff is quickened. Further, the link information is transmitted to the handoff control station, and the handoff control station calculates and controls the optimum route, so that network resources can be effectively used and network congestion can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a mobile communication network to which the present invention is applied.

FIG. 2 is an explanatory diagram showing a general call connection control procedure.

FIG. 3 is an explanatory diagram showing an ATM cell format.

FIG. 4 is an explanatory diagram showing a format of control data of a call control cell in a general call connection control procedure.

FIG. 5 is an explanatory diagram (1) showing a format example of a call control cell used in the present invention.

FIG. 6 is an explanatory diagram (2) showing a format example of a call control cell used in the present invention.

FIG. 7 is a block diagram for explaining a connection extension method.

FIG. 8 is a block diagram illustrating a backup connection in the connection extension method.

FIG. 9 is a block diagram for explaining a connection procedure between an old connection and a backup connection.

FIG. 10 is an explanatory diagram showing a handoff procedure in the connection extension method of the present invention.

FIG. 11 is a block diagram for explaining a connection switching method.

FIG. 12 is a block diagram illustrating a backup connection in the connection switching method.

FIG. 13 is a block diagram for explaining a connection procedure between an old connection and a backup connection.

FIG. 14 is an explanatory diagram showing a handoff procedure in the connection switching method of the present invention.

FIG. 15 is a flowchart showing a route determination process in the handoff control station.

FIG. 16 is a flowchart showing processing when a connection is actually switched in the handoff control station.

FIG. 17 is a graph showing a relationship between a used band and a link cost.

[Explanation of symbols]

1 ... mobile network, 2 ... fixed network, 3 ...
Partner terminal, 10-15 ATM switch, 16-18 radio base station, 19 mobile terminal, 20-24 pseudo terminal, 3
0 to 32: wireless cell area, 45: call reference conversion table, 60: link information table, 61: route information table

Claims (8)

(57) [Claims] In a mobile communication network including an exchange, a communication line, a radio base station, and a mobile terminal, a radio base station corresponding to a radio area where the mobile terminal is expected to move is accommodated in another exchange. In this case, a spare connection is established from the exchange accommodating the currently communicating radio base station to the pseudo terminal means accommodated in the another exchange, and the mobile terminal moves to the radio area corresponding to the another exchange. In this case, the mobile communication characterized by connecting the connection currently being communicated with the spare connection to extend the route, and performing communication with the mobile terminal by switching the pseudo terminal means to the mobile terminal. Handoff method in the network. 2. In a mobile communication network including an exchange, a communication line, a wireless base station, and a mobile terminal, a wireless base station corresponding to a wireless area where the mobile terminal is expected to move is accommodated in another exchange. In such a case, a spare connection is established from the exchange requiring a change in the communication path to the pseudo terminal means accommodated in the another exchange, and when the mobile terminal moves to the wireless area corresponding to the another exchange, Handoff in a mobile communication network, wherein a communication path is switched to the spare connection in an exchange requiring a change in the communication path, and the pseudo terminal means is switched to a mobile terminal to perform communication with the mobile terminal. Method. 3. The handoff method according to claim 2, further comprising a handoff control station in the mobile communication network, wherein the handoff control station routes the backup connection based on the collected traffic information in the network. Determining a handoff method. 4. In a mobile communication network including an exchange, a communication line, a wireless base station, and a mobile terminal, a wireless base station corresponding to a wireless area expected to move the mobile terminal is accommodated in another exchange. In the case, in order to extend or switch the connection, when establishing a spare connection to the another exchange, the exchange is provided with pseudo-terminal means temporarily acting as a mobile terminal function, A mobile communication network with a handoff function. 5. The mobile communication network according to claim 4, wherein when the connection is extended from the exchange before the movement to the exchange after the movement using the backup connection, the connection numbers can be referred to each other. A mobile communication network having a handoff function, wherein a connection number conversion table is provided in an exchange. 6. The mobile communication network according to claim 4, further comprising: a handoff control station for determining a path of the backup connection based on collected traffic information in the network. Mobile communication network with a handoff function. 7. The mobile communication network according to claim 6, wherein the handoff control station uses communication link use band information;
A link information table for storing the amount of cells stored in an output buffer of the exchange connected to the communication link; and a connection route table for retaining the exchange and the communication link through which the connection passes as route information. Based on the information, it has a handoff function that determines the switch and communication link through which the new connection passes, compares the determined route with the route before moving in the connection route table, and specifies the switching switch of the connection. Mobile communication network. 8. The mobile communication network according to claim 6, wherein the handoff control station determines a communication link as a path and an exchange based on the routing information in the link information table, and establishes a connection of the mobile terminal. Calculates the cost of each communication link using the required bandwidth, the bandwidth used by each communication link, the maximum bandwidth, the number of cells stored in the output buffer of the exchange, and the maximum cell storage value, and selects the path with the lowest cost. Mobile communication network with a handoff function.