JP3479883B2 - Handover method and mobile communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system, and more particularly to a handover method for an IMT-2000 system that provides different bearer services for each area.

[0002]

2. Description of the Related Art The IMT-2000 system, which is being studied and developed for practical use, supports various bearer services to provide multimedia services. That is, the IMT-2000 can provide a plurality of bearer services.

In the IMT-2000 system, the bearer service provided may be differentiated for each area, that is, the transmission rate that can be provided for a call may be determined for each area. For example, it is conceivable to provide an area that provides a high-speed rate and an area that provides only a low-speed rate at the request of the communication carrier.

Further, in a base station such as a micro base station which has less hardware resources than an ordinary base station, if a channel of packet data of 384 kbps is set, for example, voice or data of data communication at a low rate is set. May be overflowed in the base station, so it is necessary to limit it to only slow rates.

FIG. 9 is a block diagram showing the configuration of the IMT-2000 system.

In FIG. 9, the IMT system has a mobile switching center 91, a radio base station controller 92, a base station 93 and a base station 94, and connects an incoming / outgoing call of a mobile station (UE) 95 to perform communication. It is possible.

A mobile switching center (CN) 91 establishes an exchange connection between a calling source and a called destination. In addition, usually IMT-2000
Among the multiple mobile switching centers 91 in the system, IMT-
Some are connected to a telephone network to connect a subscriber in the 2000 system and a subscriber in a wired telephone network.

A radio base station controller (RNC) 92 is connected to the mobile switching center 91 and base stations 93 and 94,
Call control is performed by controlling the subordinate base stations 93 and 94.

A base station (NodeB) 93 is a radio device capable of communicating with the mobile station 95 by radio waves, and has a high rate (3
It is possible to provide up to 84 kbps).

A base station (NodeB) 94 is a radio device capable of communicating with a mobile station 95 by radio waves and has a low rate (6
4 kbps) can be provided.

The base stations are classified according to the transmission rate that can be provided. Here, the base station 9 that provides a high rate is provided.
Base station 94 that classifies Class 3 as 0 and provides only low-speed rates
Is class 1.

The radio base station control device 92 is a subordinate base station 9
The transmission rates that can be provided by the mobile stations 3, 94 are stored as station data, and at the time of handover, the cells of all base stations over which the mobile station 95 crosses the transmission rate (active set cell rate) at which the mobile station 95 communicates are provided. Change to a possible transmission rate.

In FIG. 9, the mobile station 95 is a class 1 base station 9
Handover is performed across 4 and the base station 93 of class 0. Since the base station 94 cannot provide the high speed rate, the transmission rate becomes 64 kbps.

FIG. 10 is a diagram showing a situation in which the mobile station 5 is further disconnected from the base station 94 of class 1 after the handover shown in FIG. 9 and connects a new base station 93 of class 0. is there.

Until then, the mobile station 95 had an active set cell rate of 64 kbps, while the base station 93 had 38.
Since it is possible to provide 4 kbps, the rate is changed in the handover of FIG. 10 and the active set cell rate is 384 kb.
ps.

[0016]

Generally, IMT-2000
The system is provided with a plurality of radio base station controllers 92, and a handover (subscriber line extension) may occur across the radio base station controllers 92.

The radio base station controller 92 stores the transmission rate that can be provided by the base station under its own station as station data, but does not store the transmission rate that can be provided by the base station under other stations. .

When performing a handover from a class 0 base 93 under the control of its own station to a class 1 base station 94 under the control of another station, the handover source radio base station controller 92 establishes a 384 kbps bearer channel to the handover destination base station 94. In order to set, the handover destination radio base station controller 9
For 2 "Radio Link Setup procedure"
To execute.

However, since the radio base station controller 92 of the handover destination cannot set the bearer channel of 384 kbps in the base station 94, "Radio Link S" is set.
Reject the channel setup with "setup Failure procedure".

Therefore, the handover fails and the call is lost when the communication between the mobile station 95 and the base station 93 cannot be maintained.

By storing the transmission rates that can be provided by all the base stations 93 and 94 in all the radio base station control devices 92, it is possible to change the handover speed across the radio base station control devices 92, but the station data Is enormous, and it is not realistic considering the difficulty of adding or changing the system.

An object of the present invention is to provide a mobile communication system under the control of different radio base station control devices and capable of performing handover between base stations having different transmission rates that can be provided.

[0023]

In order to achieve the above object, the handover method of the present invention is a handover method for changing the connection between a mobile station and a cell as the mobile station moves in a mobile communication system. In advance, the cells are classified into classes according to the transmission rate that can be provided to the call, and used for scrambling the pilot channel, the identification code unique to the cells includes information indicating the classes to which the cells belong, When receiving the notification of the reception status of the pilot channel from the mobile station, determine an additional cell to be newly connected and a deleted cell to be disconnected from the notification,
The class to which the additional cell belongs is obtained from the identification code included in the notification, the additional cell is added to the currently connected cell, and the transmission rate that can be provided by all the cells except the deleted cell And changing the communication with the mobile station to the transmission rate, disconnecting the communication with the mobile station via the deleted cell, and connecting with the mobile station via the additional cell.

Therefore, according to the present invention, when the mobile communication system receives the notification of the reception state of the pilot channel from the mobile station, whether or not to perform the handover based on the reception quality of each radio wave indicated in the notification. To decide. When performing a handover, a class is obtained by calculation from the identification code of the additional cell, and the available transmission rate is obtained by referring to the station data. Since the handover is performed by changing the transmission rate so that it can be provided to all cells that are in the connected state after the handover, and deleting and adding cells, the class of all cells is managed by the enormous station data registered. It is possible to perform a handover across cells having different transmission rates even without using them.

According to an embodiment of the present invention, the information indicating the class is a remainder obtained by dividing the identification code by the number of classes.

When the additional cell is under the control of the handover source radio base station controller, the class of the additional cell is determined from the second station data in which the correspondence between the cell and the class is preset. May be obtained directly.

The mobile communication system of the present invention is a mobile communication system that performs handover by changing the connection between the mobile station and a cell as the mobile station moves, and has a transmission rate that can be provided for a call. A plurality of base stations that include information indicating a class to be classified and that form at least one cell identified by the identification information used for scrambling the pilot channel, and a notification of the reception state of the pilot channel from the mobile station. At this time, from the notification, the additional cell to be newly connected to the mobile station and the deleted cell to be disconnected are determined, and the class to which the additional cell belongs is obtained from the identification code included in the notification. Adding the additional cell to the cell, determining the transmission rate that can be provided in all the cells except the deleted cell, communication with the mobile station After changing to the transmission rate, the handover source radio base station control device that disconnects the communication between the deleted cell and the mobile station and connects the additional cell and the mobile station, and the handover source radio base station control It has a handover destination radio base station control device that operates in cooperation with a device to change the transmission rate and connects the additional cell and the mobile station.

According to an embodiment of the present invention, the information indicating the class is a remainder obtained by dividing the identification code by the number of classes.

When the additional cell is under the control of the handover source radio base station controller, the second station data in which the correspondence between the cell and the class has been set in advance is used to determine the additional cell You may ask for classes directly.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, an IMT-2000 mobile communication system according to an embodiment of the present invention is a mobile switching center (C).
N) 1, a radio base station controller (RNC) 2, and base stations (NodeB) 3 and 4.

The mobile switching center 1 establishes an exchange connection between a calling source and a called destination. In addition, a plurality of mobile switching centers 1 usually provided in the IMT-2000 system are connected to another system such as a telephone network for connecting a subscriber of the IMT-2000 system and a subscriber of another system. There is something.

The radio base station control device 2 is connected to the mobile switching center 1 and the base stations 3 and 4, and is under the control of the base stations 3 and 4.
To control call connection.

Further, when the mobile station 5 performs a handover across the radio base station control devices 2, the mobile station 5 is operated before that.
The radio base station control device 2 that has been transmitting and receiving a signal as a handover source (S-RNC), and the radio base station control device 2 that newly starts transmitting and receiving a signal with the mobile station 5 as a handover destination (D-RNC). I will call it.

As shown in FIG. 2, the radio base station controller 2
Has a network unit 21 and a control unit 22.

In order for the radio base station control device 2 to communicate with the base stations 3 and 4 or the mobile switching center 1, the network section 21 performs exchange connection of signals transmitted and received to and from desired destinations.

The control unit 22 has a call information management unit 23, a call control unit 24, a handover determination unit 25, a speed determination unit 26 and a station data management unit 27.

The call information management unit 23 records and manages information about each call as a call information table.

In the call information table, the cell IDs of the cells connected to the mobile station 5 for each call, the states of those cells, and the primary scrambling code (Primary).
A scrambling code), a transmission rate (corresponding speed) provided in the cell, a class thereof, and a transmission rate currently used by the mobile station 5 for communication are stored. The state of the cell means whether the call is effectively using the cell (Active), or whether the call is about to be terminated due to a decrease in the reception level of radio waves (tobe d
deleted), are you going to use (t
o be added).

Hereinafter, a set of cells to which the mobile station 5 is connected by a handbar is referred to as an active set, a cell belonging to the active set is referred to as an active set cell, and a transmission rate used by the mobile station 5 for communication is referred to as an active set cell. It will be referred to as speed.

In the IMT-2000 system, the mobile station 5 measures the reception level of the radio pilot channel sent from the base station, which is called the primary CPICH, in order to know the quality of the radio wave. Primary CP of each cell
The ICHs are scrambled by different primary scrambling codes, and the base stations and cells can be identified by using the scrambling codes.

In general, the values that the primary scrambling code can take are n = 16 × i (i = 0, 1,
2, ..., 511), but for ease of understanding,
As used herein, "primary scrambling code" shall refer to i rather than n.

Each cell has a limitation on the transmission rate that can be provided, and is classified into classes according to the limitation conditions. Normally, the transmission rate that can be provided by the cell is determined for each base station. Here, it is assumed that the classes are classified into two classes, a class 0 that can provide a high speed rate (384 kbps) and a class 1 that can only provide a low speed rate (64 kbps).

Primary scrambling of each cell
The code is set to the value associated with the class of that cell. The relationship is class = (primary scrambling code)% m (% is the remainder operator, m is the number of classes into which the cells are classified).

When the mobile station performs a handover across a plurality of cells, it is necessary to match the transmission rate used for communication to a rate that can be provided by all active set cells before actually performing the handover. That transmission rate is the active set cell rate.

When there is an incoming or outgoing call, the call control unit 24 controls the connection of those calls. In addition, the call control unit 24, "Mes
When the measurement result of the primary CPICH is notified from the mobile station 5 by the "Urement Report message", the handover determining unit 25 is activated to determine whether or not to perform handover. Then, the call control unit 24 needs the determination. When performing the handover, the call control unit 24 also performs the handover after changing the active set cell rate to the rate determined by the rate determining unit 26, if necessary.

The handover determining unit 25 selects a cell to be terminated or a cell to be newly used from the measurement result of the primary CPICH reported from the mobile station 5, and determines whether or not to perform the handover.

The rate determining unit 26 determines the transmission rate that can be provided by all the active set cells including the cell which is about to be newly used in the handover, and sets it as the active set cell rate. The speed determination unit 26 uses the primary scrambling code as the number of classes (here,
Since there are Class 0 and Class 1, the number of classes is "2". The remainder divided by is the class of each active set cell, and the transmission rate that each class can provide is recognized from the station data, and all active set cells are recognized. Determines the transmission rate that can be provided by the active set cell rate.

The station data management unit 27 stores, as station data, the relationship between each class, which is a cell classification, and the transmission rate that each class can provide. This is common in the system and is common to all radio base station control devices 2.

The base station 3 is a radio device capable of communicating with the mobile station 5 by radio waves and has a high transmission rate (384).
kbps). Therefore, the cells covered by the base station 3 are classified into class 0. The base station 4 is also a radio device capable of communicating with the mobile station 5 by radio waves, but provides only a low rate (64 kbps). Therefore, the cells covered by the base station 4 are classified into class 1.

Next, the operation of the mobile communication system of this embodiment will be described.

FIG. 3 is a sequence diagram showing the operation of the mobile communication system in a hander between base stations of different classes, which are under the control of different radio base station controllers. In the figure, UE is a mobile station, S-RNC is a handover source radio base station controller, D-RNC is a handover destination radio base station controller, and NodeB is a handover destination base station under the control of the D-RNC. .

Referring to FIG. 3, first, the UE measures the quality of the primary CPICH of each neighboring cell and outputs the result to S.
-Notify the RNC with a Measurement Report message. Measurement Report
The message contains the primary scrambling code for each cell and the measurement results corresponding to that cell. S-RNC is the Measurement Report
Depending on the content of the message, the cell to be deleted from the active set cell, the cell to be added, and the like are determined, and whether or not to perform the handover is determined. Here, it is assumed that it is decided to add the NodeB under the control of the D-RNC to the active set cell.

The S-RNC identifies the class from the Node B's primary scrambling code and No
Calculate the active set cell rate including deB.

If the calculated active set cell rate is different from the current one, the S-RNC will be "Physic".
al CH Reconfiguration procedure "to change the transmission rate. Next, the S-RNC executes" Active Set Update procedure "to update the active set (here, D-RNC is added) to perform handover. Complete.

Therefore, the mobile communication system according to the present embodiment includes the measurement report from the mobile station 5.
When the t message is received, it is determined from the reception quality of each radio wave indicated therein whether or not the handover is performed, and when the handover is performed, each active set cell considering the cells to be added or deleted. Cell I
The class is calculated from D, the transmission rate that can be provided is obtained by referring to the station data, the transmission rate that can be provided by all the active set cells is obtained as the active set cell rate, and the active set cell rate is obtained if necessary. After the change, the handover is performed by adding or deleting the active set cell, so that the handover can be performed across the base stations 3 and 4 which are under the control of different radio base station control devices 2 and which can provide different transmission rates. Therefore, when the mobile station moves in the mobile communication system, the transmission rate that can be provided by the cell does not match, so that the communication is not disconnected.

In this embodiment, when the cell to be added to the active set is under the control of the handover source radio base station controller, the cell class may be obtained by the above-described operation of the present invention. Alternatively, it may be directly obtained from station data as in the conventional case.

In FIG. 4, the base station controller 2 measures
It is a flowchart which shows the procedure which receives a ment Report message and determines whether to implement a hand-over.

Measurement from mobile station 5
Upon receiving the Report message, the radio base station control device 2 activates the handover determination unit 25 from the call control unit 24, and the handover determination unit 25 determines whether or not to perform the handover (step 101). At this time, the handover determining unit 25 determines that the Measurement Re
A cell to be added to or deleted from the active set is determined from the contents of the port message, and the new state of each active set cell is set to Active (in communication), To b.
e added (to be added), To be delete
Any one of ed (scheduled to be deleted) is recorded in the call information table 60 in association with the primary scrambling code.

The handover decision unit 25 determines whether or not the handover can be carried out (step 102), and when the handover is not carried out, the processing is ended. When performing a handover, the handover determining unit 25 calls the speed determining unit 26, the speed determining unit 26 determines the class of each active set cell, the transmission rate (corresponding speed) that can be provided, and the call information managing unit 23 calls. Record in the information table (step 103). The processing of the speed determination unit 26 at this time is (primary scrambling code)% n = class (for primary scrambling code recorded in the call information table corresponding to each active set cell). n is the number of classes,% is a remainder operator), the class is determined, and the transmission rate that can be provided by each class is extracted from the station data of the station data management unit 27.

After that, the speed determination unit 26 determines the transmission rate that can be provided by all the active set cells as a new active set cell speed, and the call information management unit 23 records it in the call information table (step 104). Then, the speed change and the handover are performed thereafter.

Next, the structure of the call information management table and the specific contents during operation will be described in detail.

FIG. 5 is a diagram showing the contents of the call information table managed by the call information management unit 23.

The call information table 50 is composed of a primary list 51 and a secondary list 52. In the primary list 51, the terminal number of the mobile station 5 in communication and the information indicating the recording position of the call information in the secondary list corresponding thereto are recorded for each call. The secondary list 52 includes cell IDs (Cell I) of active set cells for each call.
D), status, primary scrambling code,
The class, available transmission rate (supported rate) and active set cell rate are recorded.

The contents of the call information table shown in FIG.
In the operation shown in FIG. 4, Measurement Re
It is an example of an initial state before receiving a port message.

The mobile station 5 is in a handover state across a plurality of cells, and the cell IDs of the respective active set cells are 230, 232 and 235 in order. The state of all cells is Active (in communication). The primary scrambling codes are 202, 103, 400 in order.

Here, assuming that the number of classes of cells n is 4, the classes obtained by the calculation are 2, 3, 0 in order.

Here, each class has a class 0 up to 384 kbps and a class 1 of 1 as shown in the station data of FIG.
It is assumed that transmission rates up to 28 kbps, class 2 up to 64 kbps, and class 3 up to 32 kbps can be provided. Therefore, 32 kbps that can be provided by all active set cells is set as the active set cell speed, and the mobile station 5 is communicating at 32 kbps.

From mobile station 5 to Measurement R
Upon receiving the eport message, the call control unit 53 activates the handover determining unit 25, and the handover determining unit 25
Determines whether to execute the handover. Here, it is assumed that the handover of deleting the cell having the cell ID of 232 and adding the cell having the cell ID of 233 is determined.

The speed determining unit 26 obtains the class of the cell having the cell ID 233 by calculation, extracts the corresponding transmission rate from the station data, and rewrites the call information table. At this time, the state of the cell to be deleted is changed to "to be de
"letted", and the state of the cell to be added is "t
In addition, the active set cell speed is for the active set cell after the addition and deletion of cells. The contents of the secondary list 52 at this time are as shown in FIG.

Active set cell speed is 32 kbps
From 64 kbps to "Physical
After changing the speed by executing the "CH Reconfiguration procedure", "Active Set U"
The handover is performed by adding and deleting cells according to the "pdate procedure." The contents of the secondary list 52 after the handover is completed are as shown in FIG.

[0072]

According to the present invention, when the mobile communication system receives the notification of the reception state of the pilot channel from the mobile station, whether or not to carry out the handover based on the reception quality of each radio wave indicated in the notification. To decide. When performing a handover, a class is obtained by calculation from the identification code of the additional cell, and the available transmission rate is obtained by referring to the station data. Since the handover is performed by changing the transmission rate so that it can be provided to all cells that are in the connected state after the handover, and deleting and adding cells, the class of all cells is managed by the enormous station data registered. Even if it is not necessary, handover can be performed across cells having different transmission rates, and when the mobile station moves within the mobile communication system, the transmission rate that can be provided by the cells does not match and communication is not cut off.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing a configuration of a mobile communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a radio base station control device of this embodiment.

FIG. 3 is a sequence diagram showing an operation of a mobile communication system in a hander between base stations of different classes, which are under the control of different radio base station controllers.

[Fig. 4] A base station controller 2 is a Measurement R
9 is a flowchart showing a procedure of receiving an eport message and determining whether or not to perform a handover.

5 is a diagram showing the contents of a call information table managed by a call information management unit 23. FIG.

FIG. 6 is a diagram showing an example of station data.

FIG. 7 is a diagram showing the contents of a secondary list after a handover is decided.

FIG. 8 is a diagram showing the contents of a secondary list after completion of handover.

FIG. 9 is a block diagram showing a configuration of a conventional IMT-2000 system.

FIG. 10 is a diagram showing a state in which a mobile station performs a handover from a class 0 base station to a class 0 base station.

[Explanation of symbols]

1 Mobile Switching Center (CN) 2 Radio base station controller (RNC) 3,4 Base station (NodeB) 5 Mobile Station (UE) 21 Network Department 22 Control unit 23 Call Information Management Department 24 Call control unit 25 Handover decision unit 26 Speed determination unit 27 station data management department 50 Call information table 51 Primary list 52 Secondary list 101-104 steps

Claims (6)

(57) [Claims] 1. In a mobile communication system, a mobile station is moved.
Hand-over that changes the connection between the mobile station and the cell
In this method, the cells are preset at the transmission rate that can be provided for the call.
Classify into ras and use for scrambling pilot channel
The cell belongs to an identification code unique to the cell,
Including the information indicating the class, the mobile station notifies the reception status of the pilot channel.
When notified, an additional session to be newly connected from the above notification.
And the deleted cells to be disconnected and included in the notification.
The class to which the additional cell belongs from the identification code
And add the additional cell to the currently connected cell,
The transmission rate that can be provided by all the cells except the deleted cell.
Of the mobile station, and after changing the communication with the mobile station to the transmission rate,
Disconnecting communication with the mobile station via the deleted cell,
Handover connecting to the mobile station via the additional cell
Method. 2. The handover method according to claim 1, wherein the information indicating the class is a remainder obtained by dividing the identification code by the number of classes. 3. When the additional cell is under the control of the handover source radio base station controller, the class of the additional cell is calculated from the second station data in which the correspondence between the cell and the class is preset. The handover method according to claim 1, wherein the request is directly obtained. 4. A mobile communication system that performs handover by changing the connection between a mobile station and a cell as the mobile station moves, and indicates a class classified into a transmission rate that can be provided for a call. A plurality of base stations including information and forming at least one cell identified by the identification information used for scrambling the pilot channel, and when receiving the notification of the reception state of the pilot channel from the mobile station, from the notification, Determining an additional cell to be newly connected to the mobile station and a deleted cell to be disconnected,
The class to which the additional cell belongs is obtained from the identification code included in the notification, the additional cell is added to the currently connected cell, and the transmission rate that can be provided by all the cells except the deleted cell And changing the communication with the mobile station to the transmission rate, disconnecting the communication between the deleted cell and the mobile station, and controlling the handover-source radio base station that connects the additional cell and the mobile station. A mobile communication system comprising a device and a handover destination radio base station control device that operates in cooperation with the handover source radio base station control device to change the transmission rate and connect the additional cell and the mobile station. 5. The mobile communication system according to claim 4, wherein the information indicating the class is a remainder obtained by dividing the identification code by the number of classes. 6. When the additional cell is under the control of the handover source radio base station controller, the correspondence of the cell and the class is set in advance from the second station data of the additional cell. The mobile communication system according to claim 4, wherein the class is directly obtained.