KR20040105069A - Hand off call processing method - Google Patents

Abstract

PURPOSE: A method for processing a handoff call is provided to delete a target base station in an active set of a mobile station and a call DB when the target base station does not receive a signal of the mobile station during handoff, and to collect channels assigned to the mobile station, thereby preventing a call of the mobile station from being abnormally disconnected. CONSTITUTION: After a target base station is completely added to a call DB of a CCP and an active set of a mobile station(S30), the target base station transmits information for permitting the use of a channel assigned to the mobile station(S32), and drives a timer for measuring a response standby time of the mobile station(S34). The target base station monitors whether a response signal is received(S36). If not, the target base station requests a BSC to collect channels(S44). A selector of a base station reports the channel collection to a CCP, so that the CCP can delete information on the target base station to restore call data(S46). The selector supplies channel setup information without the information on the target base station to the mobile station(S48). The mobile station restores the active set to an original state(S50). The selector informs the target base station and a serving base station that the active set is fully recovered(S52). The target base station collects the channels from the mobile station, and transmits cell setup information showing that the channels cannot be used in the mobile station(S54).

Description

HAND OFF CALL PROCESSING METHOD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handoff call processing method. In particular, in a 1 × Evolution Data Optimized (EVEV) system providing a high-speed packet data service, a call of a mobile station being handed off between cells is abnormally disconnected due to a channel recovery of a target base station. A handoff call processing method for preventing the phenomenon.

The 1 × EVDO service is a high-speed packet data service based on CDMA2000 and is mainly applied to video and data services. When inter-cell handoff occurs in a 1xEVDO system, the forward link proceeds in a hard handoff manner and the reverse link proceeds in a soft handoff manner.

The mobile station in the 1xEVDO system requires a high-speed packet data service to a base station which transmits a pilot having the best forward signal quality by comparing magnitudes of pilot signals in an active set during a handoff process.

Here, the active set is a base station in which a forward call channel is assigned to a mobile station and is in a call. The candy date set is a base station that has a sufficiently large pilot signal but does not participate in a call, and a neighbor ser is active. A base station that is not included in the set or the candy date set but is likely to have a handoff.

When the mobile station moves from the serving base station in the active set to the adjacent target base station, when the pilot signal of the target base station becomes larger than the preset value, handoff is started to the target base station and the target base station is updated in the active set.

An update method for such an active set will be described in detail with reference to FIG. 1. 1 is a signal flowchart according to a target base station information adding process for handoff.

If the mobile station 3 receives a base station pilot signal of which the forward pilot signal is greater than or equal to the preset value T_Add while the mobile station 3 moves between cells, the mobile station 3 transmits the base station controller 20 through the serving base station 3 that is currently provided with the service. A handoff request message is sent to the selector 22 (Selector, SLP) of S1 and requests channel resource allocation of the target base station 5 to be handed off (C1). Here, the base stations 3 and 13 transmit and receive data to and from the mobile station 3 with the base station transmitters 5 and 15 and the base station processors 7 and 17, respectively.

The selector 22 reports the handoff request message of the mobile station 3 to the Call Control Processor (CCP) 24 (C3).

The CCP 24 transmits information for the update of the active set of the mobile station 3 to the selector 22 to allocate channel resources of the target base station 5 requested by the mobile station 3 (C5).

The selector 22 provides information related to channel allocation of the target base station 5 requested by the mobile station 3 to the serving serving base station 3 (C7), and the serving serving base station 3 receives the received serving base station 3 to the selector 22. A response signal for receiving the information is transmitted (C9).

The selector 22 transmits a channel assignment message including handoff information to the mobile station 3 (C12). Here, the format of the channel assignment message is configured according to the IS-856 method, which is a 1 × EVDO standard defined in 3GGP2, and includes a message ID, a message sequence, a message, a channel, a frame offset, and a DRC. Information such as length (DRCLength), DRC channel gain (DRCCannelGain), and the number of pilots (NumPilots) is included. Information such as pilot PN, MAC index, etc. is included per number of pilots in the active set.

Accordingly, the mobile station 3 transmits a channel setup completion message, which is a response signal to the channel assignment message received from the selector 22, wherein the mobile station 3 transmits the target base station 5 to the active set. Add the information of (C14).

The selector 22 receiving the channel setting completion message from the mobile station 3 informs the serving base station 3 that the mobile station 3 has added the target base station 5 to the active set (C16), and the serving base station (3). ) Transmits a response signal thereto (C16).

The selector 22 informs the CCP 24 that the mobile station 3 has added the target base station 5 to the active set. At this time, the CCP 24 updates the call database (C20).

According to the above process, the information of the target base station 5 is added to the active set of the mobile station 3 and the call database of the CCP 24, and a procedure for transmitting and receiving between the mobile station 3 and the target base station 5 is performed. .

Meanwhile, the channel card of the serving base station 3 and the target base station 5 transmits a QuickConfig message including setting information of the corresponding cell into the cell so that the mobile station 3 in the cell can use the channel allocated by the base station. The format of the QuickConfig message provided to this mobile station 3 includes the following Table 1 information according to the IS-856 method, which is a 1xEVDO standard defined by 3GGP2.

<Table 1>

field Length (bits) MessageID 8 Colorcode 8 SectorID24 24 SectorSignature 16 AccessSignature 16 Redirect One RPCCount 6

Here, each RPCCount field includes the information of Table 2 below.

DRCLock One ForwardTrafficValid 1 (or 0)

Here, ForwardTrafficValid is information indicating whether the channel is permitted to the mobile station 3, and if the field value is set to '1', the channel can be used, and if set to '0', the ForwardTrafficValid is sent to the mobile station 3. Indicates that the channel usage is not allowed.

Therefore, the target base station 5 added to the active set of the mobile station 3 and the call database of the CCP 24 sets the ForwardTrafficValid to '1' and transmits a QuickConfig message in the cell, thereby making it possible to use the channel to the corresponding mobile station 3. In response to the notification, the mobile station 3 transmits a pilot signal and a DRC channel signal in response to this, thereby enabling signal transmission and reception between the two.

As such, after the information of the target base station 5 is added to the active set of the mobile station 3 and the call database of the CCP 24, the cell setting information provided by the target base station 5 (QuickConfig message) and The communication between the target base station 5 and the mobile station 3 is possible only when the exchange of the response (pilot signal and DRC channel signal) of the mobile station 3 is completed. If this process fails, the target base station 5 and Communication between the mobile stations 3 is cut off.

This process will be described in more detail with reference to FIG. 2. 2 is a control flow diagram illustrating a conventional handoff call processing process. After the information of the target base station 5 is added to the active set of the mobile station 3 and the call database of the CCP 24, the handoff call processing process is performed. It is shown.

After completion of adding the target base station 5 to the active set of the mobile station 3 and the call database of the CCP 24 (S1), the target base station 5 sets ForwardTrafficValid to '1' in the RPCCount field of the cell configuration information (QuickConfig message). By setting the signal to ',' the mobile station 3 in the cell is informed that the channel can be used (S3). The target base station 5 drives the timer after transmission of the channel availability information (S5).

The target base station 5 monitors whether a response signal (pilot signal and DRC channel signal) from the mobile station 3 has been received by the target base station 5 (S7), and when a response is received from the mobile station 3, a timer Ignoring the time (S9), the addition of the target base station 5 information is successfully completed by initiating communication with the mobile station 3 (S10).

Here, the mobile station 3 receives cell configuration information for all pilot PNs (PilotPNs) in the active set, but checks whether the channel is available only for the pilot PNs in which the forward traffic MAC (ForwardTrfficMAC) is activated. The ForwardTraffficMAC is activated when the channel allocation message is transmitted from the selector 22 in step C12 of FIG. 1, so that the mobile station 3 is a target base station for handoff among base stations included in the active set. Only for (5), the channel availability is checked.

On the other hand, if a response is not received from the mobile station 3 after the channel availability information of the target base station 5 is transmitted, the target base station 5 checks the elapsed time of the timer and responds from the mobile station 3 for a predetermined reference time or more. It is determined whether a signal is not received (S12).

When no response signal is received from the mobile station 3 for a reference time or more, the target base station 5 recovers the channel, sets the ForwardTrafficValid to '0' in the RPCCount field of the cell configuration information (QuickConfig message), and transmits the cell. It is notified that the channel of the corresponding mobile station 3 in the channel is unavailable (S14).

The target base station 5 reports to the CCP 24 that the channel to the mobile station 3 has been recovered (S16), and the CCP 24 deletes the information of the target base station 5 from the call database to restore the call data. By recovering (S18), it fails to add the target base station 5 (S20).

In this way, if the mobile station 3 does not respond to the cell setting information transmitted by the target base station 5 within a predetermined time, the target base station 5 first retrieves the channel and then reports it to the CCP 24. The call database is being restored.

On the other hand, even when the target base station 5 has recovered the channel, the mobile station 3 still contains the target base station 5 in the active set of the mobile station 3, so that the mobile station 3 is configured to perform the operation of the target base station 5 in the active set. The pilot PN is periodically monitored and transferred to a call waiting state according to channel unavailable information of the target base station 5.

Accordingly, when the handoff fails because the signal of the mobile station 3 is not received by the target base station 5, in the state where the target base station 5 is still included in the call database and the active set of the mobile station 3, Since the target base station 5 recovers the channel, there is a problem that the call of the mobile station 3 is abnormally disconnected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and the call of the mobile station being handed off between cells in the 1 × EVDO (1 × Evolution Data Optimized) system providing high-speed packet data service is abnormal due to the channel recovery of the target base station. It is an object of the present invention to provide a handoff call processing method for preventing a phenomenon of being cut off.

1 is a signal flow diagram illustrating a process of adding information of a target base station to an active set of a mobile station and a call database of a CCP as a handoff occurs.

2 is a control flow diagram illustrating a conventional handoff call processing process after information of a target base station is added to an active set of a mobile station and a call database of a CCP;

3 is a control flowchart illustrating a handoff call processing process according to the present invention after information of a target base station is added to an active set of a mobile station and a call database of a CCP.

*** Explanation of symbols for the main parts of the drawing ***

1: mobile station 3: serving base station

13 target base station 20 base station controller

22 selector 24 call processing processor

The handoff call processing method according to the present invention for achieving the above object is a target in the call database of the active set of the mobile station and the base station controller according to the handoff request of the mobile station moving from the serving base station to the adjacent target base station in the current call Adding information of the base station; Transmitting, by the target base station, a cell establishment message including channel availability information allowing use of a channel allocated to the mobile station; Requesting, by the target base station, the base station controller to restore the call database if the mobile station does not receive a response signal from the mobile station; Deleting, by the base station controller, information of the target base station added to the call database according to a request of the target base station; Transmitting, by the base station controller, active set recovery information to the mobile station through a serving base station based on the restored call database; The mobile station deleting information on the target base station added to the active set based on the active set recovery information; The base station controller notifying of completion of restoration of the call database and the active set; And recovering the channel allocated to the mobile station by the target base station which has confirmed the restoration of the call database and the active set.

The requesting of the target base station to restore the call database to the base station controller may include: driving the timer by the target base station after the cell setting message is transmitted; Determining whether a response signal of the mobile station to the cell setting message has been received within a predetermined reference time of the timer; If the mobile station is not answered within the reference time, the target base station may include requesting the base station controller to restore the call database.

And deleting information of the target base station added to the active set by the mobile station based on the active set recovery information, when the information of the target base station is added to the active set, is activated for the target base station. It is preferable to include the step of switching the ForwardTrafficMAC in an inactive state.

The recovering of the channel allocated to the mobile station by the target base station comprises: transmitting a cell setting message in the cell, the cell setting message including channel unavailable information, which disallows use of the channel allocated to the mobile station; It is preferable to further include.

Hereinafter, a handoff call processing method according to a preferred embodiment of the present invention with reference to the accompanying drawings will be described in detail. When the mobile station moves from a serving serving base station to an adjacent target base station, the handoff is initiated at the request of the mobile station, and is applied to the handoff process after the target base station is updated to the active set.

Therefore, the process of adding the information of the target base station to the call database of the active set of the mobile station and the CCP by requesting handoff by the mobile station moving between cells, the active set of the mobile station described with reference to FIG. The procedure is the same as updating the call database of the CCP.

3 is a control flowchart showing a handoff call processing process according to the present invention after the information of the target base station 5 is added to the active set of the mobile station 3 and the call database of the CCP 24.

After the completion of the addition of the target base station 5 to the active set of the mobile station 3 and the call database of the CCP 24 (S30), the target base station 5 sets ForwardTrafficValid to '1' in the RPCCount field of the cell configuration information (QuickConfig message). By setting to ',' it is notified that the channel of the mobile station 3 in the cell can be used (S32). The target base station 5 drives a timer for measuring the response waiting time from the mobile station 3 after transmission of the channel availability information (S34).

The target base station 5 monitors whether a response signal (pilot signal and DRC channel signal) from the mobile station 3 has been received by the target base station 5 (S36), and when a response is received from the mobile station 3, a timer The process of adding the target base station 5 is successfully completed by ignoring the time (S38) and commencing communication with the mobile station 3 (S40).

Here, the mobile station 3 receives cell configuration information for all pilot PNs (PilotPNs) in the active set, but checks whether the channel is available only for the pilot PNs in which the forward traffic MAC (ForwardTrfficMAC) is activated. The forward traffic MAC is activated when a channel assignment message is transmitted from the selector 22 in step C12. That is, the mobile station 3 checks whether the channel is available only for the target base station 5 for handoff among the base stations included in the active set, and when the channel use is allowed (forwardTrafficValid is set to '1'), Send and receive data through the channel.

On the other hand, if a response is not received from the mobile station 3 after the channel availability information of the target base station 5 is transmitted, the target base station 5 checks the elapsed time of the timer and responds from the mobile station 3 for a predetermined reference time or more. It is determined whether a signal is not received (S12).

If the response signal is not received from the mobile station 3 for the reference time or more, the target base station 5 requests the base station controller 20 to recover the channel (S44).

The selector 22 of the base station receiving the channel recovery request from the target base station 5 reports it to the CCP 24, whereby the CCP 24 deletes the information of the target base station 5 from the call database and restores the call data. (S46).

After call data recovery, the CCP 24 requests the selector 22 to update the active set of the mobile station 3 according to the restored call data, and the selector 22 deletes the information of the target base station 5. The provided channel setting information (TrafficChannelAssignment) message is provided to the mobile station 3 through the serving base station 3 (S48).

Accordingly, the mobile station 3 responds to the channel setting information provided by the selector 22 and restores the active set to its original state by deleting the target base station 5 from the active set based on the channel setting information (S50). . At this time, the forward traffic MAC (ForwardTrfficMAC), which was initially activated while adding the target base station 5 to the active set, is inactivated according to step C12 of FIG. 1. Therefore, the mobile station 3 does not confirm the channel setting message originating from the target base station 5 later.

When the reception of the channel setting information of the mobile station 3 is confirmed, the selector 22 fails to add the target base station 5 during the handoff process, indicating that the recovery of the active set is completed, and thus the target base station 5 and the serving base station 3 are completed. Notify (S52).

When the active set recovery completion signal is received from the selector 22, the target base station 5 recovers the channel assigned to the mobile station 3, and sets ForwardTrafficValid to '0' in the RPCCount field of the cell configuration information (QuickConfig message). By setting and transmitting, it is notified that the channel of the mobile station 3 in the cell cannot be used (S54).

As described above, when the target base station does not receive the signal of the mobile station during handoff, the present invention first deletes the target base station from the active set and call database of the mobile station, and then confirms that the restoration of the active set and the call database is completed. In this case, the channel allocated to the mobile station is recovered.

Therefore, it is possible to prevent the call of the mobile station from being abnormally disconnected when the target base station fails to receive the signal of the mobile station during handoff.

As described above, the embodiment of the handoff call processing method according to the present invention is not limited to the above description, and various modifications can be made within the scope obvious to those skilled in the art.

According to the present invention as described above, when the target base station does not receive a signal of the mobile station during handoff, the target base station is first deleted from the active set and call database of the mobile station, thereby restoring the active set and the call database. After the completion is confirmed, the channel allocated to the mobile station is recovered.

Accordingly, when the target base station fails to receive a signal of the mobile station during handoff, it is possible to prevent the call of the mobile station from being abnormally disconnected.

Claims (4)

Adding information of the target base station to a call database of an active set of the mobile station and a base station controller according to a handoff request of a mobile station moving from a serving base station currently in communication to an adjacent target base station; Transmitting, by the target base station, a cell establishment message including channel availability information allowing use of a channel allocated to the mobile station; Requesting, by the target base station, the base station controller to restore the call database if the mobile station does not receive a response signal from the mobile station; Deleting, by the base station controller, information of the target base station added to the call database according to a request of the target base station; Transmitting, by the base station controller, active set recovery information to the mobile station through a serving base station based on the restored call database; The mobile station deleting information on the target base station added to the active set based on the active set recovery information; The base station controller notifying of completion of restoration of the call database and the active set; And recovering a channel allocated to the mobile station by a target base station which has confirmed the restoration of the call database and active set. The method of claim 1, The target base station requests the base station controller to restore the call database. Driving, by the target base station, a timer after transmitting the cell setting message; Determining whether a response signal of the mobile station to the cell setting message has been received within a predetermined reference time of the timer; Requesting the base station controller to recover the call database if the target base station is not answered within the reference time. The method of claim 1, The mobile station deleting information on the target base station added to the active set based on the active set recovery information; And adding a forward traffic MAC (ActivatedTrafficMAC) activated for the target base station to an inactive state when adding information of a target base station to the active set. The method of claim 1, The step of recovering the channel assigned to the mobile station by the target base station, And transmitting, by the target base station, a cell setting message including channel unavailable information for disallowing use of a channel allocated to the mobile station in the corresponding cell.