JP2002135823A - Hand-over method and mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system, which enables handing- over between the base stations of different presentable transmission rates under the control of different radio base station controllers. SOLUTION: Information showing the classes of classifying cells prepared by base stations 3 and 4 at the transmission rate presentable to a call is contained in a primary scrambling code and a radio base station controller 2 of a hand-over source receives the notice of the receiving state of a pilot channel from a mobile station, determines an adding cell and a deleting cell by a hand-over determining part 25, finds a class, to which the adding cell belongs, from the information showing the classes and adds the adding cell to the cell under connection at present. Then, the transmission rate presentable in all the cells except for the deleting cell is determined by a velocity determining part 26. After communication with the mobile station is changed to the transmission rate by a call control part 24, the communication between the deleting cell and the mobile station is cut off and the adding cell and the mobile station are connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mobile communication system, and more particularly, to a handover method for an IMT-2000 system that provides a different bearer service for each area.

[0002]

2. Description of the Related Art An IMT-2000 system under study and development for practical use supports various bearer services to provide multimedia services. That is, IMT-2000 can provide a plurality of bearer services.

In the IMT-2000 system, the bearer service to be 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 a communication carrier.

[0004] In a base station such as a micro base station, which has less hardware resources than a normal base station, if a channel of 384 kbps packet data is set, for example, data for voice or data communication at a low rate is set. May overflow in the base station, so it is necessary to limit to only a low rate.

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 incoming and outgoing calls of a mobile station (UE) 95 to perform communication. Make it possible.

[0007] A mobile switching center (CN) 91 makes a switching connection between a calling source and a called party. Also, usually IMT-2000
Some mobile switching centers 91 in the system include IMT-
Some are connected to a telephone network to connect subscribers in the 2000 system to subscribers in the wired telephone network.

A radio base station controller (RNC) 92 is connected to a mobile switching center 91 and base stations 93 and 94,
It controls the subordinate base stations 93 and 94 to perform call connection.

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

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

[0011] The base stations are classified according to the transmission rates that can be provided.
Base station 94 that provides 3 for class 0 and provides only low rate
Is class 1.

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

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

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

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

[0016]

SUMMARY OF THE INVENTION IMT-2000
In the system, a plurality of radio base station controllers 92 are provided, and a handover (subscriber line extension) across radio base station controllers 92 may occur.

The radio base station controller 92 stores, as station data, a transmission rate that can be provided by a base station under its control, but does not store a transmission rate that can be provided by a base station under another station. .

When a handover is performed from the class 0 base 93 under the control of the own station to the class 1 base station 94 under the control of another station, the handover source radio base station controller 92 transmits a 384 kbps bearer channel to the handover destination base station 94. In order to set, the handover destination radio base station controller 9
2 for “Radio Link Setup procedure”
Execute

However, the radio base station controller 92 at the handover destination cannot set a 384 kbps bearer channel to the base station 94, so that "Radio Link S"
The channel setting is rejected by the "setup failure procedure".

Therefore, if the handover fails and communication between the mobile station 95 and the base station 93 cannot be maintained, a call loss occurs.

By storing the transmission rates that can be provided by all the base stations 93 and 94 in all the radio base station controllers 92, it is possible to change the handover speed across the radio base station controllers 92. This 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 which is under the control of different radio base station controllers and is capable of performing handover between base stations having different transmission rates.

[0023]

In order to achieve the above object, a handover method according to the present invention is a handover method for changing a 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 for the call, and used for scrambling the pilot channel, and information indicating the class to which the cell belongs is included in an identification code unique to the cell, When receiving the notification of the reception state 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,
Determine the class to which the additional cell belongs from the identification code included in the notification, add the additional cell to the currently connected cell, and provide a transmission rate that can be provided by all the cells except the deleted cell After the communication with the mobile station is changed to the transmission rate, the communication with the mobile station via the deleted cell is disconnected, and the mobile station is connected with the mobile station via the additional cell.

Therefore, according to the present invention, when receiving the notification of the pilot channel reception state from the mobile station, the mobile communication system determines whether to perform the handover based on the reception quality of each radio wave indicated in the notification. To determine. When performing handover, a class is obtained by calculation from the identification code of the additional cell, and a transfer rate that can be provided is obtained by referring to the station data. The handover is performed by changing the transmission rate so that it can be provided by all cells that are in a connected state after the handover, and by deleting and adding cells, so the class of all cells is managed with a huge amount of registered station data. A handover can be performed across cells having different transmission rates without the need.

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 obtained from the second station data in which the correspondence between the cell and the class is set in advance. May be obtained directly.

A mobile communication system according to the present invention is a mobile communication system in which a handover is performed by changing a connection between a mobile station and a cell as the mobile station moves. Including information indicating a class to be classified, a plurality of base stations that form at least one cell identified by identification information used for scrambling the pilot channel, and received a notification of the reception state of the pilot channel from the mobile station When, from the notification, determine an additional cell to be newly connected to the mobile station and a deleted cell to be disconnected, determine the class to which the additional cell belongs from the identification code included in the notification, Adding the additional cell to the cell, determining a transmission rate that can be provided in all the cells except the deleted cell, and performing communication with the mobile station. After changing to the transmission rate, the communication between the deleted cell and the mobile station is disconnected, and the handover source radio base station controller connecting the additional cell and the mobile station is controlled, and the handover source radio base station control is performed. A handover destination radio base station controller for changing the transmission rate in cooperation with a device and connecting 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 cell of the additional cell is obtained from the second station data in which the correspondence between the cell and the class is set in advance. You may ask for a class directly.

[0030]

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 (Node B) 3 and 4.

The mobile switching center 1 performs a switching connection between a calling source and a called destination. Also, some mobile switching centers 1 in the IMT-2000 system are usually connected to another system such as a telephone network in order to connect a subscriber of the IMT-2000 system to a subscriber of another system. There is something.

The radio base station controller 2 is connected to the mobile switching center 1 and the base stations 3 and 4, and the subordinate base stations 3 and 4
Is controlled to perform a call connection.

In the case where the mobile station 5 performs a handover across the radio base station controllers 2, the
The radio base station controller 2 that has transmitted and received the signal is a handover source (S-RNC), and the radio base station controller 2 that newly starts transmitting and receiving signals to and from the mobile station 5 is a handover destination (D-RNC). Shall be referred to.

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 controller 2 to communicate with the base stations 3 and 4 or the mobile switching center 1, the network unit 21 performs exchange connection of signals to be transmitted and received with the desired destination.

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 on each call as a call information table.

The call information table contains, for each call, the cell IDs of the cells connected to the mobile station 5, the states of those cells, and the primary scrambling code (Primary code).
Scramble Code), the transmission rate (corresponding speed) provided by the cell, its class, and the transmission rate currently used by the mobile station 5 for communication are stored. The state of the cell indicates whether the call is using the cell effectively (Active) or is ending the use due to a decrease in the reception level of the radio wave (tobe d).
eliteed), or is it about to be used (t
o be added).

Hereinafter, a set of cells to which the mobile station 5 is connected by a handover 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 is referred to as speed.

In the IMT-2000 system, the mobile station 5 measures the reception level of a wireless pilot channel called a primary CPICH, which is transmitted from a base station, in order to know the quality of a radio wave. Primary CP of each cell
Each ICH is scrambled with a different primary scrambling code, and the base station and the cell can be identified using the scrambled code as an identification code.

In general, the possible values of the primary scrambling code are n = 16 × i (i = 0, 1,
2, ..., 511), but in order to facilitate understanding,
In this specification, "primary scrambling code" refers to i rather than n.

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

The primary scrambling of each cell
The code has a value associated with the class of the cell. The relation is class = (primary scribbling code)% m (% is a remainder operator, and m is the number of classes into which cells are classified).

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

When there are incoming and outgoing calls, the call control unit 24 controls those call connections. Further, the call control unit 24 sets “Mes
When the measurement result of the primary CPICH is notified from the mobile station 5 by the “report Report message”, the mobile station 5 activates the handover determining unit 25 to determine whether or not to perform the handover. When performing the handover, the call control unit 24 changes the active set cell speed to the speed determined by the speed determination unit 26, if necessary, and then performs the handover.

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

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

The station data management section 27 stores, as station data, the relationship between each class, which is a classification of cells, and the transmission rate that each class can provide. This is common in the system, and is data common to all the radio base station controllers 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, cells covered by the base station 3 are classified into class 0. The base station 4 is also a wireless device capable of communicating with the mobile station 5 by radio waves, but provides only a low rate (64 kbps). Therefore, cells covered by the base station 4 are classified into class 1.

Next, the operation of the mobile communication system according to the present embodiment will be described.

FIG. 3 is a sequence diagram showing the operation of the mobile communication system in a handover between base stations of different classes 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 of the neighboring cells and reports the result to S.
-Notify the RNC with a Measurement Report message. Measurement Report
The message includes the primary scrambling code of each cell and the measurement result corresponding to that cell. S-RNC is Measurement Report
Based on the contents of the message, a cell to be deleted from the active set cell, a cell to be added, and the like are determined, and whether or not to perform handover is determined. Here, it is assumed that it has been decided to add a NodeB under the control of the D-RNC to the active set cell.

The S-RNC identifies the class from the primary scrambling code of the Node B,
Calculate the active set cell rate including deB.

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

Therefore, in the mobile communication system of this embodiment, the measurement report is transmitted from the mobile station 5 to the measurement reporter.
When the t message is received, it is determined whether or not to perform a handover based on the reception quality of each radio wave indicated therein, and when performing the handover, each active set cell considering a cell to be added or deleted Cell I of
A class is obtained by calculation from D, a transmission rate that can be provided by referring to station data is obtained, a transmission rate that can be provided by all active set cells is obtained as an active set cell speed, and an active set cell speed is obtained as necessary. Is changed, the handover is performed by adding or deleting the active set cell, so that the handover can be performed over the base stations 3 and 4 under different radio base station controllers 2 and having different transmission rates that can be provided. In addition, when the mobile station moves in the mobile communication system, the communication is not disconnected because the transmission rates that the cells can provide do not match.

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 the station data as in the related art.

FIG. 4 shows that the base station controller 2
It is a flowchart which shows the procedure which determines whether a handover is performed by receiving a report report message.

Measurement from mobile station 5
Upon receiving the Report message, the radio base station controller 2 activates the handover deciding unit 25 from the call control unit 24, and the handover deciding unit 25 decides whether or not to perform a handover (Step 101). At this time, the handover determination unit 25 sets the Measurement Re
Cells to be added to or deleted from the active set are determined from the contents of the port message, and Active (during communication) and Tob are set as new states of each active set cell.
e added (to be added), To be delete
Any one of ed (to be deleted) is recorded in the call information table 60 in association with the play scrambling code.

The handover determining section 25 determines whether or not to execute the handover (step 102), and terminates the processing if the handover is not to be executed. 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 and the available transmission rate (corresponding speed), and the call information managing unit 23 The information is recorded in the information table (step 103). At this time, the processing of the speed determination unit 26 is based on (primary scrambling code)% n = class (for the 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) to determine the class, and further extract the transmission rate that can be provided for each class from the station data of the station data management unit 27.

Thereafter, the rate determining unit 26 determines a transmission rate that can be provided by all the active set cells as a new active set cell rate, 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 specific contents during operation will be described in detail.

FIG. 5 is a diagram showing the contents of a 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 the communication state and the information indicating the recording position of the call information in the secondary list corresponding to the terminal number are recorded for each call. The secondary list 52 includes a cell ID (Cell I) of an active set cell for each call.
D), state, primary scrambling code,
The class, the available transmission rate (corresponding rate) and the active set cell rate are recorded.

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

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

Here, assuming that the class number n of the cell is 4, the classes obtained by the operation are 2, 3, and 0 in order.

Here, as shown in the station data of FIG. 6, each class is up to 384 kbps for class 0 and 1 for class 1
It is assumed that up to 28 kbps, up to 64 kbps for class 2 and up to 32 kbps for class 3 can be provided. Therefore, 32 kbps that can be provided by all the active set cells is set as the active set cell speed, and the mobile station 5 is communicating at 32 kbps.

Measurement R from mobile station 5
Upon receiving the report message, the call control unit 53 activates the handover determination unit 25, and the handover determination unit 25
Determines whether to perform a handover. Here, it is assumed that a handover in which the cell with the cell ID of 232 is deleted and the cell with the cell ID of 233 is added is determined.

The rate determining section 26 calculates the cell class of 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
lett ", and the state of the cell to be added is" t ".
o be added ". The active set cell speed is related to the active set cell after the addition or deletion of the cell. The contents of the secondary list 52 at this time are as shown in FIG.

Active set cell speed is 32 kbps
Is 64 kbps, so "Physical
After performing the “CH Reconfiguration procedure” to change the speed, the “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 completion of the handover are as shown in FIG.

[0072]

According to the present invention, when a mobile communication system receives a notification of a pilot channel reception state from a mobile station, it determines whether to perform a handover based on the reception quality of each radio wave indicated in the notification. To determine. When performing handover, a class is obtained by calculation from the identification code of the additional cell, and a transfer rate that can be provided is obtained by referring to the station data. The handover is performed by changing the transmission rate so that it can be provided by all cells that are in a connected state after the handover, and by deleting and adding cells, so the class of all cells is managed with a huge amount of registered station data. Even without this, handover across cells with different transmission rates is possible, and when a mobile station moves in a mobile communication system, communication is not cut off because the transmission rates that the cells can provide do not match.

[Brief description of the 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 illustrating a configuration of a radio base station controller according to the present embodiment.

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

FIG. 4 is a diagram illustrating a Measurement R
It is a flowchart which shows the procedure which receives an report message and determines whether to implement handover.

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

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

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

FIG. 8 is a diagram showing 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 illustrating a situation where a mobile station performs a handover from a class 0 base station to a class 0 base station.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mobile switching center (CN) 2 radio base station controller (RNC) 3, 4 base station (NodeB) 5 mobile station (UE) 21 network unit 22 control unit 23 call information management unit 24 call control unit 25 handover determination unit 26 Speed determination unit 27 station data management unit 50 call information table 51 primary list 52 secondary list 101 to 104 steps

Claims (6)

[Claims] 1. A handover method in a mobile communication system for changing a connection between a mobile station and a cell as the mobile station moves, wherein the cell is classified into classes according to a transmission rate that can be provided for a call in advance. And, for use in scrambling of a pilot channel, information indicating the class to which the cell belongs is included in an identification code unique to the cell, and when the mobile station receives a notification of the reception state of the pilot channel from the mobile station, the notification Determine the additional cell to be newly connected and the deleted cell to be disconnected from, determine the class to which the additional cell belongs from the identification code included in the notification, and determine the additional cell for the currently connected cell. In addition, after determining the transmission rate that can be provided in all the cells except the deleted cell, after changing the communication with the mobile station to the transmission rate
A handover method for disconnecting communication with the mobile station via the deleted cell and connecting to the mobile station via the additional cell. 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 radio base station controller at the handover source, the class of the additional cell is obtained from second station data in which the correspondence between the cell and the class is set in advance. The handover method according to claim 1, wherein? 4. A mobile communication system for performing a handover by changing a connection between a mobile station and a cell as the mobile station moves, indicating a class classified as a transmission rate that can be provided for a call. Including information, a plurality of base stations that create at least one cell identified by the identification information used for scrambling the pilot channel, When receiving a notification of the reception state of the pilot channel from the mobile station, from the notification, Determine an additional cell to be newly connected to the mobile station and a deleted cell to be disconnected,
Determine the class to which the additional cell belongs from the identification code included in the notification, add the additional cell to the currently connected cell, and provide a transmission rate that can be provided by all the cells except the deleted cell After 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 connecting the additional cell and the mobile station A mobile communication system comprising: a device; and a handover destination radio base station controller that operates in cooperation with the handover source radio base station controller to change the transmission rate and connects 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 radio base station controller of the handover source, the additional cell of the additional cell is obtained from second station data in which correspondence between the cell and the class is set in advance. The mobile communication system according to claim 4, wherein the class is directly obtained.