KR20080085388A - Data processing method and system during handover of mobile terminal in mobile communication system - Google Patents

Abstract

The present invention relates to a data processing method and system during handover in a mobile communication system, and a data processing method in a mobile communication system in which a mobile terminal for transmitting and receiving packet data provided by the present invention with a source base station is handed over to a target base station. Transmitting, by the mobile terminal, a measurement report including the optimal cell change information at which the target base station is located to the source base station, wherein the source base station examines a handover condition with respect to the measurement report, and the handover condition is satisfied; When the source base station transmits a handover indication message to an access gateway to which the source base station is connected, the access gateway receiving the handover indication message sets a data rate for the source base station until the handover is completed. The process of making adjustments By adjusting the amount of packet data buffered in the source base station by including increasing the quality of communication services provided to mobile users can efficiently use a communication resource.

Description

METHOD AND SYSTEM FOR PROCESSING DATA AT HANDOVER OF A MOBILE TERMINAL IN A MOBILE COMMUNICATION SYSTEM}

1 is a network configuration diagram of a general LTE system connected to a packet network;

2 is a flowchart illustrating a packet data processing method in a handover situation in a mobile communication system according to an embodiment of the present invention;

3 is a call processing diagram illustrating a flow of calls between communication entities for processing packet packet data during handover in a mobile communication system according to an embodiment of the present invention.

The present invention relates to data processing of a mobile communication system, and more particularly, to a data processing method and system during handover in a mobile communication system.

Handover means that when a source cell in which a terminal is located is changed due to mobility of the terminal, data received by the terminal is continuously received in a target cell where the terminal is located after the movement. It is a procedure to receive.

The procedure of the handover is briefly described as follows. The terminal measures a pilot signal of a source cell and cells adjacent to the source cell and reports to a source base station located in the source cell. This report is called a Measurement Report. If there is a pilot of a target base station having a stronger intensity than the pilot of the source base station during the measurement report, the terminal may include "best cell change" information for a new connection with the target base station in the measurement report. .

The source base station receiving the optimal cell change information checks whether the target base station is suitable for communication with the terminal, and if the communication between the target base station and the terminal is appropriate, requests a handover to the target base station and the target base station. Prepares a handover with the terminal, and when the preparation for the handover is completed, the terminal is connected with the target base station and the source base station releases resources allocated to the terminal.

In addition, there are two types of data transmission methods in a mobile communication system, a circuit method and a packet method. The circuit method enables communication only when a communication request is made to the other party such as a voice call, and the communication is possible, and since a dedicated channel is set up one-to-one for each communication between the transmitting and receiving terminal devices, the stability of data transmission and reception is increased. Even when data is not exchanged between channels, the channel is set and other users cannot use the dedicated channel, which may cause waste of resources.

The packet method is a method of dividing data to be transmitted in a predetermined size and performing communication using a packet, which is a data block attached to an address to which the data should be transmitted. Since data is transmitted in packet units, a dedicated channel between communication users does not need to be established. Therefore, since a packet generated by a plurality of users can be transmitted through one channel, resources can be efficiently used.

Therefore, in the mobile communication system, the circuit method is generally used for voice data in which communication stability is important, and the packet method is used for text data other than voice. In the following, a Long Term Evolution (LTE) system will be described as an example of the mobile communication system.

The LTE system is being discussed as the next generation mobile communication system for Universal Mobile Telecommunications System (UMTS) in 3GPP (3rd Generation Partnership Projct), and it is possible to change the bandwidth, which was limited to 5 MHz in the existing 3G mobile communication, from 1.25 MHz to 20 MHz. Standardization is currently under discussion, aiming for a data rate of 100Mbps, and aims for commercialization in 2010.

1 is a network configuration diagram of a general LTE system connected to a packet network.

The LTE system uses an Evolved UMTS Radio Access Network (E-UTRAN), which is an access node and an access node that is a higher node than the Evolved Node B (ENB) 121, 123, 125. A gateway (Access GateWay: AGW) 131 is included. User equipment (UE) (111, 113, 115), which is a user terminal (hereinafter, abbreviated as " terminal "), accesses the packet network 141 through the E-UTRAN. It is assumed that b 113 and UE c 113 are wirelessly connected to ENB b 123. According to the network structure as described above, each terminal may transmit and receive data by accessing the packet network 140 through the E-UTRAN.

In general, a user terminal may be represented by a mobile station (MS), a terminal equipment (TE), etc. In 3GPP, a user terminal is represented as a user equipment (UE) in 3GPP. Also, in FIG. 1, three terminals are shown for convenience of description, but the number of terminals varies according to a communication environment.

However, since the data transmitted from the packet network 141 to the terminals is often large data such as multimedia data, and the wireless communication section has a relatively low data rate compared to the wired section, the base station ENB when the packets are transmitted to the terminals. In b 123, a large number of packets are often buffered. For reference, in the LTE system, when the terminal receives the TCP / IP packet data, the base station may be buffered up to 64 KB.

In general, a data service provided in a mobile communication system is limited in a maximum transmission rate according to a bandwidth set between a base station and respective terminals. In addition, since a plurality of terminals are connected to one base station ENB b 123, bottlenecks of packets may occur at the base station ENB b 123 when packets are transmitted from the base station ENB b 123 to the respective terminals. Can be. The bottleneck causes the base station ENB b 123 to buffer a large amount of packets.

If a UE a 111 that has been transmitting and receiving data through the ENB b 123 moves to a cell in charge of the ENB a 121 and a handover occurs, the ENB b as a source base station Data buffered at 123 is transmitted or discarded to ENB a 121, which is a target base station. That is, the source base station may transmit the buffered packets to the target base station before handover so that the packets are forwarded to the terminal, or the source base station may discard the buffered data.

Whether to transmit or discard the buffered data is irrelevant to whether the terminal receives the buffered data from a target base station and may be determined according to a type of a communication system or a service.

If the buffered packet is transmitted to the target base station, resources for packet transmission are required and a problem may occur in transmission quality of packets transmitted from the target base station to the terminal due to a transmission delay in the transmission process. In addition, when the buffered packets are discarded at the source base station and the same packets as the buffered packets do not reach the terminals through the target base station directly in the packet network, the terminal cannot receive the discarded packets. This can be degraded.

That is, in both cases where the buffered packets are transmitted or discarded, there is a problem that the quality of communication service provided to the terminal is degraded. Also, the greater the amount of packets buffered, the greater the degree of degradation of the quality of service. Therefore, when a handover situation occurs in a mobile communication system, it is necessary to reduce the amount of packets buffered at the source base station to improve communication service quality due to handover.

One aspect of the present invention provides a method and system for adjusting and processing the amount of packet data buffered at a source base station in a handover situation in a mobile communication system.

Accordingly, in a mobile communication system in which a mobile terminal that transmits and receives packet data provided by the present invention with a source base station is handed over to a target base station, the data processing method includes measuring the mobile terminal including optimal cell change information at which the target base station is located. Transmitting a report to the source base station, and the source base station checks a handover condition with respect to the measurement report, and if the handover condition is satisfied, transmits a handover indication message to an access gateway to which the source base station is connected; And adjusting, by the access gateway, receiving the handover indication message, a data rate for the source base station in a preset manner until the handover is completed.

In addition, a mobile communication system in which a mobile terminal that transmits and receives packet data provided by the present invention with a source base station is handed over to a target base station. A preset method of receiving a handover indication message and a source base station for checking a handover condition of the target base station with respect to the measurement report and transmitting a handover indication message to an access gateway when the handover condition is satisfied And an access gateway for adjusting the data rate for the source base station until the mobile terminal completes the handover.

An embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

2 is a flowchart illustrating a packet data processing method in a handover situation in a mobile communication system according to an embodiment of the present invention.

In step 201, the UE measures pilot signals of adjacent cell base stations and reports a measurement report to the source base station if at least one of the measured values satisfies a predetermined reference value. The measurement report may include the above-described "best cell change" information.

The source base station which has received the measurement report including the optimal cell change information in step 203 checks the handover primary condition and proceeds to step 207 when the primary condition is satisfied in step 205 and the source base station instructs the AGW to handover. Send a (HO Indication) message. The primary test may be a condition that is less relaxed than the final condition of handover.

In addition, when the primary condition is satisfied, the source base station transmits a handover indication message to the AGW because the final condition of the handover is likely to be satisfied, and according to the handover indication message, the AGW transmits a handover primary condition. It can be seen that it is satisfied. The handover indication message includes traffic amount information buffered at the source base station at the time of transmission of the message, and maximum throughput information limited to the terminal.

In step 209, the UE performs the second measurement on the pilot signal of the adjacent cell as in step 201. When the second measurement value satisfies a predetermined reference value, the UE reports the second measurement to the source base station. In step 211, the step 203 is performed. Check the handover final condition.

If the final condition is satisfied in step 213, the process proceeds to step 215 and the source base station requests a handover to the target base station. If the final condition is not satisfied, the process proceeds to step 225 and the source base station transmits a message to the AGW to cancel the handover indication message transmitted in step 207. This is because the first condition is satisfied but the final condition is not met.

If the target base station completes preparation for handover in step 217, the process proceeds to step 219. The source base station instructs the terminal to handover, and in step 221, the AGW adjusts a data rate of data transmitted to the source base station. The method of adjusting the transmission rate will be described in detail in Equation 1 to be described later. The rate adjustment continues until the handover ends in step 223.

In FIG. 2, the first and final conditions of the handover are divided into two stages. However, in some cases, the handover may be determined based on a plurality of differential conditions.

Hereinafter, a method of adjusting the data rate of data transmitted from the AGW to the source base station in step 221 will be described in detail with Equation 1 below.

(1) R = 0, 0≤ t <8B / (r * a)

(2) R = r * b, 8B / (r * a) ≤ t <e

here

R: Data rate in bps for the source base station of the gateway during handover

B: Amount of data buffered in the source base station when transmitting a handover indication message (Byte)

r: data rate between the base station and the terminal (bps)

a: time adjustment factor

b: Underflow argument

e: When handover completes

t: time since the handover indication message is sent

An example of the data transfer restriction by Equation 1 will be described. When the source base station transmits a handover indication message to the AGW, it is assumed that the data B buffered at the source base station is 1k bytes and the data rate r from the source base station to the terminal is 8000 bps and a = 1 is set. R = 0 during the time that all the buffered data is transmitted to the terminal by 0) (0≤t <8B / (r X a): 0≤t <8 X 1000 / (8000 X 1) = 1 sec) Because of the limitations, no data is sent from the AGW to the source base station.

If the time adjustment factor a = 1.1 is set, the data transmitted from the AGW to the source base station is 0 for 0 ≦ t <8 × 1000 / (8000 × 1.1) = 0.91 sec. Therefore, in this case, before all the buffered data is transmitted to the terminal, the AGW may transmit new data to the source base station so that the data can be continuously transmitted from the source base station to the terminal. The value of a may vary depending on the communication environment or the type of service.

In (2), R = r X b is limited to 8B / (r X a) ≤ t <e. If b = 1.2, R = 8000 X 1.2 = 9600 bps. The reason for setting b in the above (2) is to efficiently use communication resources by making the data transfer rate more than a certain limit so that no data underflow occurs.

According to Equation 1, the AGW restricts the data rate for the source base station to minimize the data buffered at the source base station during the handover, thereby efficiently using the communication resources and improving the communication quality provided to the terminal during the handover. You can.

3 is a call processing diagram illustrating a flow of calls between communication entities for packet data processing during handover in a mobile communication system according to an embodiment of the present invention.

In step 301, the terminal 341 transmits the primary measurement report described with reference to FIG. 2 to the source base station 343, and in step 303, the source base station 343 examines the handover primary condition based on the primary measurement report. In step 305, the source base station 343 transmits a handover indication message to the AGW 347. In operation 307, the secondary measurement result described with reference to FIG. 2 is reported to the source base station 343. In step 309, the handover final condition is checked, and in step 311, the source base station 343 requests the handover to the target base station 345.

In step 313, the target base station 345 performs a handover preparation process in response to the handover request. When the preparation is completed, the target base station 345 transmits a response to the handover request to the source base station 343. The source base station 343 receiving the response instructs the UE 341 to handover in step 317, and in step 131, the AGW 347 receives the source base station 343 in a state in which the data rate according to Equation 1 is limited. Send data to In step 321, the source base station 343 may forward or discard the buffered data to the target base station 345. Whether to transfer or discard can be selected according to a communication service or a system as described above.

In step 323, the target base station 345 and the terminal 341 mutually perform time synchronization to perform handover, and exchange information between the base station and the terminal 341. In step 325, the terminal 341 targets the target. In step 327, the target base station 345 transmits a handover end message to the AGW 347.

The AGW 347 that has received the termination message in step 329 switches the transmission path to the target base station 345 and forwards an acknowledgment (ACK) message for the handover termination message to the target base station 345 in step 331. By doing so, the UE 341, the target base station 345, and the AGW 347 are connected, and the handover is terminated. Since the handover is terminated, the source base station 343 is no longer required to participate in data transmission. In step 333, the target base station 345 transmits a release message to the source base station 343. 343 completely releases the resources allocated to the terminal 341.

Although the present invention has been described in detail so far, the embodiments mentioned in the process are only illustrative and are not intended to be limiting, and the present invention is provided by the following claims. Within the scope not departing from the scope of the present invention, component changes to the extent that they can be equivalently substituted from the present invention will fall within the scope of the present invention.

According to the above-described technical configuration of the present invention, by adjusting the amount of packet data buffered at the source base station even in the handover in the mobile communication system, it is possible to improve the quality of the communication service provided to the mobile communication user and to efficiently use the communication resources.

Claims (8)

 A data processing method in a mobile communication system in which a mobile terminal for transmitting and receiving packet data with a source base station is handed over to a target base station, Transmitting, by the mobile terminal, a measurement report including optimal cell change information at which the target base station is located to the source base station; Checking, by the source base station, a handover condition with respect to the measurement report and transmitting a handover indication message to an access gateway to which the source base station is connected when the handover condition is satisfied; And And the access gateway receiving the handover indication message adjusts a data rate for the source base station in a preset manner until the handover is completed. The method of claim 1, The preset method is a data processing method according to <Equation 2>.  (1) R = 0, 0≤ t <8B / (r X a) (2) R = r X b, 8B / (r X a) ≤ t <e here R: Data rate in bps for the source base station of the gateway during handover B: Amount of data buffered in the source base station when transmitting a handover indication message (Byte) r: data rate between the base station and the terminal (bps) a: time adjustment factor b: Underflow argument e: When handover is completed. t: time since the handover indication message is sent The method of claim 1, The handover condition is a plurality of data processing method is set in step by step differential. The method of claim 3, wherein And adjusting the data rate until completion of the handover is performed when the plurality of differentially set handover conditions are satisfied. A mobile communication system in which a mobile terminal for transmitting and receiving packet data with a source base station is handed over to a target base station, A mobile terminal for transmitting a measurement report including the optimal cell change information in which the target base station is located to the source base station; A source base station which checks a handover condition of the target base station with respect to the measurement report and transmits a handover indication message to an access gateway when the handover condition is satisfied; And And an access gateway that receives the handover indication message and adjusts the data rate for the source base station until the mobile terminal completes the handover in a preset manner. The method of claim 5, The preset method is a mobile communication system according to Equation 3 below. (1) R = 0, 0≤ t <8B / (r x a) (2) R = r x b, 8B / (r X a) ≤ t <e here R: Data rate in bps for the source base station of the gateway during handover B: Amount of data buffered in the source base station when transmitting a handover indication message (Byte) r: data rate between the base station and the terminal (bps) a: time adjustment factor b: Underflow argument e: When handover completes t: time since the handover indication message is sent The method of claim 5, And wherein the handover condition is differentially set in stages. The method of claim 7, wherein And the access gateway adjusts the data rate until completion of the handover when the plurality of differentially set handover conditions are satisfied.

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