KR100486414B1 - A hard hand-over method and system without data loss - Google Patents

Abstract

The present invention relates to data transmission during hand-over in a mobile communication system. In particular, the present invention relates to a communication path from an existing link to a new link in a hard hand-over such as an inter frequency hand over. The present invention relates to a system and a method for preventing loss of untransmitted data existing in an existing link and supporting reliable hard hand-over. The present invention defines a new signal between the base station and the control station so that the control station notifies the base station of the time when a hand-over occurs, and the existing base station notifies the control station of the time when all the data stored in the buffer is transmitted to the mobile station. This ensures that all data remaining in the communication path is delivered to the mobile terminal. In addition, by placing a hand-over buffer at the control station to store the received data while establishing a new communication path, when the new communication path is completed up to the mobile terminal, the data is transferred from the buffer to the mobile terminal. It can prevent the loss of data during hand-over and support reliable hand-over.

Description

A hard hand-over method and system without data loss}

The present invention relates to a hard hand-over method and a system for preventing data loss in a mobile communication system. More particularly, the present invention relates to a hard hand-over method for adaptively selecting data loss prevention and real-time service guarantee according to a communication service type. Hand-over method.

In the mobile communication system, since the mobile terminal can basically move even during a call or data communication, the mobile terminal can move out of the corresponding base station service area and move to a service area of another adjacent base station or another control station. In this case, the mobile terminal forms a new communication channel in the adjacent communication network without interruption of the call and continuously maintains the call state. Hand-over is required.

This type of hand-over includes soft hand-over (CDMA) system, in which two or more communication channels are simultaneously formed and combined in the physical layer, as in the case of hand-over at the same frequency. There is over, and there is a hard hand-over that releases one talk channel and goes to another talk channel like hand-over between different frequencies or systems.

 In the case of soft hand-over, no data loss occurs because there is no disconnection of the call channel, but hard hand-over causes a problem because the call channel is disconnected even in a short time. For example, during the transition from an existing call channel to a new call channel, if the mobile terminal moves to the new call channel with data remaining in the buffer of the existing call channel, the data in the existing call channel is lost. . This lost data degrades the communication service.

This problem is described with reference to FIG. 1, which schematically illustrates a hard hand-over system of a mobile communication system. In FIG. 1, it is assumed that the mobile terminal 500 communicates with the existing first call channel 101. If a hand-over occurs at this time, the first call channel 101 will be released and will be transferred to the second call channel 201. At this time, the control station 300 first sets the second call channel 201 and then sends a signal to the mobile terminal 500 to switch to the second call channel 201. However, when the mobile terminal 500 crosses the second call channel 200 before all the data stored in the buffer of the first base station 100 arrives at the mobile terminal, the first base station 100 is buffered. All existing data will be lost. The lost data cannot be retransmitted to the counterpart communication entity or can not be recovered and can simply be skipped.

In Fig. 2, the signal flow in this conventional hand-over system is shown in detail. When the mobile terminal 500 enters the service area of the second base station 200 from the service area of the first base station 100, the mobile station 500 reports the result to the control station through a measurement report message. When the control station receives this observation report message, a hand-over occurs, and a new call channel via the second base station 200 is established by performing hand-over processing. When a new call channel is established, data from the core network is transmitted to the mobile terminal 500 via the second base station 200. Therefore, as described above, the data buffered in the first base station 100 is lost.

In order to prevent such data loss, conventionally, when a hand-over occurs, a control station stores a data in a buffer and returns it to a mobile switching system (MSC) to transmit a new communication channel.

However, this prior art requires an extra data transmission to return the data transmitted back to the control station in the reverse direction, causing a load on the network, and the data transmitted to the existing base station may be lost until the handover occurs. There is a problem that cannot be completely prevented from loss.

Another conventional technique proposes to transmit information not transmitted during the idle period stored in the control station buffer by setting a common channel in the mobile terminal when a hard hand-over occurs.

However, this prior art is not efficient in allocating and freeing a new common channel for a short period of time, and there is no guarantee that data loss can be completely prevented even if the idle period can be shortened.

The present invention provides a technical problem of preventing a loss of data that may occur during hard hand-over as in the aforementioned problem of the related art, improving service quality and efficiently operating a new hard hand-over method.

In order to solve the above-mentioned problems of the prior art, the present invention focuses on a new hand-over method and system from four viewpoints.

First, in the hand-over process, a new signal is defined between the control station and the base station (Iub Interface) to inform the existing base station that a hand-over has occurred, and the existing base station transmits all the data in the buffer in the base station to the mobile terminal. If so, inform the control station. Therefore, it is possible to ensure that all data in the existing base station is transmitted to the mobile terminal.

Second, when a hand-over occurs, the control station no longer transmits data in the forward direction to the base station, but creates a hand-over buffer in the radio link control (RLC) layer and stores the data therein. When a new call channel is established, the mobile terminal is instructed to change to a new call channel, data is transmitted from the hand-over buffer, and when this is completed, data transmission is performed in the conventional manner.

Third, a new scheduling scheme is proposed for efficiently transmitting data accumulated in the control station hand-over buffer until all data remaining in the existing call channel is transmitted to the mobile terminal. For example, it does not matter if the new call channel is a dedicated channel, but if it is a common channel that is commonly used with other users, a new scheduling method considering the accumulated data is required. Accordingly, the present invention proposes a new scheduling scheme in consideration of the data amount of the newly proposed hand-over buffer and the transmission buffer existing in the existing radio link controller.

Fourth, the hand-over method of the present invention described above recognizes that data loss guarantee is in a trade-off relationship with maintaining real time. Therefore, it is necessary to determine whether to apply the aforementioned hand-over method according to the type of current communication service. In other words, if the call service type has strong characteristics of real-time service such as voice call, it is important to reduce time delay rather than data loss, and in case of background service, it is important to prevent data loss even if it takes time delay. Accordingly, the Radio Resource Control (RCC) of the control station determines the type of the current call service and decides whether to apply the above technique.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, a situation in which hand-over occurs through FIG. 1 showing the hand-over system of the mobile communication system as a whole is defined. In the situation where hand-over occurs, it can be seen that data transmission is performed by interworking between the control station 300, the first base station 100, the second base station 200, and the mobile terminal 500. Assume that the mobile terminal is communicating with the call channel 101 through the first base station 100. When the mobile terminal leaves the area of the first base station 100 and enters the area of the adjacent second base station 200, the mobile station reports this information to the control station (observation report). Then, the Call Controller in the control station determines whether or not the hand-over is performed and performs the hand-over.

<Example 1>

3 shows a detailed configuration in the control station 300 in the hand-over system according to the first embodiment of the present invention.

The control station 300 is composed of a radio resource control (RRC) 310 layer and a radio link control (RLC) 320 layer. The RRC layer includes a call controller 311, and the RLC layer is a buffer. The controller 321 and the hand-over buffer 322 are included. The call control unit 311 controls the buffer control unit 321 together with call setup and release.

In the present embodiment, the operation of the detailed configuration in the control station will be described in detail through the signal flow diagram shown in FIG.

When the mobile terminal 500 enters the service area of the second base station 200 from the service area of the first base station 100, the mobile station 500 reports the result to the control station 300 through a measurement report message. When the control station 300 receives the observation report, it generates a hand-over. When a hand-over occurs, the call controller 311 stops downlink data transmission to the first base station 100 and instructs the buffer controller 321 to send data from the core network 400 to a hand-over buffer ( 322). At the same time, the call controller 311 notifies that the hand-over has occurred by transmitting a hand-over occurrence message to the first base station 100.

When the first base station 100 receives the hand-over occurrence message, the first base station transmits the data stored in the first base station buffer 101 to the mobile station 500, and when the transmission is completed, the buffer transmission complete message Is transmitted to the control station 300.

When the control station receives the buffer transmission complete message, the call control unit 311 performs a hand-over process to establish a new call channel with the second base station, and the data stored in the hand-over buffer 322 until then. Will be sent.

Therefore, according to the present embodiment, all the data transmitted to the first base station can be transmitted to the mobile terminal when a handover occurs, and data transmitted from the core network until the new call channel is set up is also stored in the hand-over buffer and then a new call channel is created. This allows for hard hand-over with no data loss.

<Example 2>

This embodiment relates to a new scheduling technique used in the first embodiment when data accumulated in the hand-over buffer 322 of a control station is transmitted through a common channel used by several users. .

Since this embodiment includes the hand-over situation, system components, and signal flow used in the description of the first embodiment, duplicate descriptions are omitted and the same reference numerals are used for the same components.

The configuration of the hand-over system according to another embodiment of the present invention will be described in detail with reference to FIG. 5.

FIG. 5 is a diagram showing the configuration of the system of the present embodiment centering on a transmit entity and a receive entity. 5 shows a hand-over buffer 322 as well as a transmission buffer 323 used for normal transmission. As can be seen in the block flow of FIG. 5, the data stored in the hand-over buffer 322 and the transmit buffer 323 are assembled together via segmentation and junction 324 and the RLC header is added at the RLC header adder 325. And is sent to the receiving entity 600. The received data is buffered in the reception buffer 610 and then reassembled after removing the RLC header (620) (630).

As can be seen in the foregoing description and in FIG. 5, since a considerable amount of data is accumulated in the hand-over buffer 322, it is not necessary if the new call channel is a dedicated channel. If the common channel (Common Channel), it is necessary to apply a new scheduling method considering both the hand-over buffer and the data of the existing transmission buffer (322). In this embodiment, the following scheduling scheme is proposed.

When the number of users using the common channel is N and the i-th user is a handover call according to the above-described embodiment, assuming that the traffic volume of each user is V (n), V (n) is Will follow.

V (n) = the number of data in the transmit buffer (if n is not i)

V (n) = number of data in hand-over buffer + number of data in transmit buffer (if n = i)

Here, if the priority for transmitting data for each user through a common channel is P (n), it is as follows.

P (n) = V (n) / {V (1) + V (2) + ... + V (N)}

Thus, user k with the highest priority becomes user k with the maximum value of P (n).

That is, k = n, where max {P (n)}.

Thus, the data of user k is transmitted through the common channel.

The above calculation may be performed once every data transmission occurs a predetermined T times to determine a user to be transmitted to the common channel.

Therefore, according to this embodiment, efficient scheduling and channel allocation are possible in operating the hand-over method of the present invention.

<Example 3>

This embodiment is directed to providing an adaptive hand-over method according to a service type in the first or second embodiment.

Since the present embodiment includes the hand-over situation and system components and signal flows used in the description of the first and second embodiments, the redundant description is omitted and the same reference numerals are used for the same components.

Therefore, the hand-over method according to the present embodiment only describes the processing flow according to the flowchart of FIG. 6.

In this embodiment, the type of communication service is divided into a type in which real-time and strong data loss is allowed, such as a voice call, and a type in which data loss prevention is important and, to some extent, weak in real-time, such as background (or data) communication. To provide a different hand-over method. In the present embodiment, the call control unit 311 of the control station 300 determines whether to apply the existing hand-over method or the hand-over method proposed in the present invention. This determination may be made according to the type of communication service currently used by the mobile terminal. In other words, if the current type of communication service is strong in real time, such as voice call, if the existing data loss is applied, the existing hand-over method is applied. The hand-over method proposed in the present invention is applied.

An overall flowchart of the hand-over method according to the present embodiment is shown in FIG.

When a hand-over call occurs, the call controller 311 first determines whether the hand-over is a soft hand-over or a hard hand-over (S12). If it is determined that the hard hand-over is determined, the call controller 311 again determines whether the service type is voice call or data transmission (S13). If the service type is a voice call with strong real-time and a certain amount of data loss, the existing hard hand-over process as shown in FIG. 2 is performed and the hand-over is terminated (S14, S15). )

However, in case of data communication where real time is weak but data loss is not allowed, the call controller 311 stops downlink data transmission (S20) and stores data transmitted from the core network in a hand-over buffer. (S21). When the data stored in the first base station buffer is transmitted to the mobile terminal and hand-over is completed (S22), the hand-over buffering is stopped (S23).

Thereafter, it is determined whether the new channel set after the hand-over is a common channel (S24). If the new channel is not a common channel, data transmission in the buffer in the control station starts (S26). If the new channel is a common channel, after allocating the channel applying the scheduling considering the data of the hand-over buffer and the transmission buffer (S25). ) Transmit the data of the buffers.

Therefore, according to this embodiment, it is possible to adaptively select the most efficient hard hand-over method according to the service type.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, the present invention defines a new signal between the control station and the base station when a hard hand-over occurs in the mobile communication system to prevent the loss of data that may be lost in the existing call channel, and at the same time In this paper, we propose a scheduling scheme that saves data from the core network with a hand-over buffer and transmits data through a new call channel, and also allocates a channel considering the amount of data in the buffer when the new call channel is a common channel. By doing so, there is a remarkable effect of improving the quality of the communication service.

1 is a block diagram illustrating a data transmission system in a hand-over situation of a mobile communication system.

2 is a signal flow diagram illustrating a prior art signal flow in a hand-over situation.

3 is a diagram illustrating a configuration of a buffer and a buffer control unit in a base station and a control station according to the present invention.

4 is a signal flow diagram illustrating a signal flow according to the present invention in a hand-over situation.

5 is a diagram showing a detailed configuration of a buffer for hand-over in a control station according to the present invention.

6 is a flowchart showing an operation sequence at a control station when a hand-over occurs in accordance with the present invention.

Claims (13)

In a hand-over method of a mobile terminal moving from a first base station area to a second base station area: (a) the mobile station reporting the first base station area deviation to a control station; (b) the control station sending hand-over occurrence information to the first base station and stopping downlink data transmission to the first base station; (c) the first base station transmitting data stored in a buffer of the first base station to the mobile terminal in response to the hand-over occurrence information; (d) when step (c) is completed, transmitting, by the first base station, a buffer transmission completion message to the control station; (e) When the control station receives the buffer transmission completion message, it performs hand-over processing and transmits data transmitted from the core network from the time of the hand-over until the new call channel is established with the second base station. Storing in the hand-over buffer of the; (f) if the new call channel is established, transmitting the data stored in the hand-over buffer and the transmit buffer in a control station to the established call channel. The method of claim 1, Before the step (b), the control station further comprises the step of identifying the communication service according to the degree of real-time, the first service type having a weak real-time and the second service type having a strong real-time Way. The method of claim 2, When the communication service is the first service type, performing the steps (b) to (f), when the communication service is the second service type, the control station establishes a call channel with the second base station, and Hand-over method for transmitting data to a second base station. The method of claim 1, wherein, before the step (b), the control station sets the communication service according to the data loss tolerance, the third service type having low data loss tolerance, and the fourth service type having high data loss tolerance. Hand-over method further comprising the step of identifying. The method of claim 4, wherein If the communication service is the third service type, performing steps (b) to (f), And the control station establishes a call channel with the second base station and transmits data to the second base station when the communication service is the fourth service type. The method according to any one of claims 1 to 5, wherein in step (f), when the new call channel is a common channel, the amount of data stored in the hand-over buffer and the transmission buffer is summed and set as a user traffic amount. And allocating channels according to priorities based on the user traffic volume. Core network; A first base station having a first base station area; A second base station having a second base station area; A mobile terminal movable from the first base station area to a second base station area; A control station for controlling hand-over between the first base station and the second base station by setting a new call channel in the second base station when the mobile terminal moves from the first base station area to the second base station area; The first base station transmits an observation report to the control station when the mobile station leaves the first base station area, and transmits data stored in the buffer to the mobile station when a hand-over occurs, and buffers when the transmission is completed. Send a transmission completion message to the control station, The control station includes a hand-over buffer, and upon receiving the observation report, suspends data transmission and transmits a hand-over occurrence message to the first base station, and after receiving the buffer transmission completion message, Performing hand-over processing and storing data transmitted from a core network from the reception of the buffer transmission completion message to the completion of the hand-over processing in a hand-over buffer and transmitting the data to a second base station. The method of claim 7, wherein The control station includes: a call controller for transmitting the hand-over occurrence message and performing the hand-over process; And a buffer controller configured to store data in the hand-over buffer under the control of the call controller. The method of claim 8, The call controller identifies the communication service transmitted from the core network according to a degree of real time, as a first service type having low real time and a second service type having strong real time. The method of claim 9, The control station, And when the identified service is the second service type, performing hand-over processing immediately after receiving the observation report to transmit data to a new call channel. The method of claim 8, The call controller may further include identifying a communication service transmitted from the core network as a third service type having a low data loss tolerance and a fourth service type having a high data loss tolerance according to data loss tolerance. Hand-over system. The method of claim 11, The control station, And if the identified service is a fourth service type, performing hand-over processing immediately after receiving the observation report to transmit data to a new call channel. 13. The control station according to any one of claims 7 to 12, wherein the control station further comprises a transmission buffer used for data transmission, and when the new call channel is a common channel, A sum-over amount of stored data is set as a user traffic amount, and a control is made to allocate a channel according to a priority based on the user traffic amount.