KR20150040080A - Method and appratus for traffic offloading in a communication system - Google Patents

Abstract

According to an embodiment of the present invention, a method for transmitting/receiving data by a user terminal of a mobile communications system comprises the steps of: receiving traffic offloading-related information from a base station; determining whether to perform traffic offloading to a different network based on the traffic offloading-related information; transmitting a message to offload traffic determined based on the traffic offloading-related information to a packet data network gateway (P-GW) if it is determined to perform the traffic offloading; and performing the traffic offloading to the different network. By using the proposed method, the base station can efficiently offload terminals within the base station to a wireless LAN even without an ANDSF server, while minimizing the effect to existing specifications.

Description

[0001] METHOD AND APPARATUS FOR TRAFFIC OFFLOADING A COMMUNICATION SYSTEM [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system, and more particularly to a wireless communication system, such as a 3GPP (Universal Mobile Telecommunications System) system (e.g., Universal Mobile Telecommunications System (UMTS), Long Term Evolution To a method for offloading a terminal from a 3GPP system to a wireless LAN network in a system interworking with a wireless LAN network.

Recently, the wireless communication technology has developed rapidly, and the communication system technology has evolved accordingly. Of these, the UMTS system is the third generation mobile communication technology and the LTE system is the fourth generation mobile communication technology.

In addition, according to the spread of smart phones, the data usage of the users has been increased. In order to cope with the explosion of data, mobile communication network operators have to use the wireless LAN network in addition to the existing cellular networks (that is, 3G and 4G networks) And efforts are being made to distribute user data.

Thus, there is a need for an effective apparatus and method for distributing user data.

It is an object of the present invention to provide a wireless communication system in which a cellular network (for example, a 3G network such as UMTS, a 4G network such as LTE, etc.) and a wireless LAN IEEE 802.11 based short range communication technology), it provides a method of offloading a terminal from a cellular network to a wireless LAN network even in the absence of the above-mentioned ANDSF. In addition, even when the mobile terminal is offloaded to the wireless LAN network, the mobile terminal maintains the registered state in the cellular network, thereby receiving important services (for example, voice service, SMS) from the cellular network .

According to an aspect of the present invention, there is provided a method of transmitting / receiving data in a mobile station in a mobile communication system, the method comprising: receiving traffic offloading related information from a base station; Determining whether to perform traffic offloading to the heterogeneous network based on the traffic offloading related information; Transmitting a message for offloading traffic determined based on the traffic offloading related information to a packet data network gateway (P-GW) when performing traffic offloading; And performing traffic offloading to the heterogeneous network.

According to another aspect of the present invention, there is provided a method of transmitting / receiving data in a base station of a mobile communication system, the method comprising: generating traffic offloading related information; And transmitting information related to traffic offloading to the terminal, wherein the terminal determines whether to perform traffic offloading to the heterogeneous network based on the traffic offloading related information, and when performing traffic offloading, A message for offloading traffic determined based on loading-related information is transmitted to a packet data network gateway (P-GW), and traffic off-loading is performed to the heterogeneous network.

A terminal for transmitting and receiving data in a mobile communication system according to another embodiment of the present invention includes a transmitting and receiving unit for transmitting and receiving signals to and from another communication entity; And controlling the transceiver to receive traffic offloading related information from the base station, determine whether to perform traffic offloading on the heterogeneous network based on the traffic offloading related information, and perform traffic offloading when the traffic offloading is performed. And a controller for transmitting a message for offloading traffic determined based on the information to the packet data network gateway (P-GW) and for performing traffic offloading on the heterogeneous network.

According to another aspect of the present invention, a base station for transmitting and receiving data in a mobile communication system includes a control unit for generating information related to traffic offloading; And a transmission / reception unit for transmitting traffic offloading related information to the terminal. The terminal determines whether to perform traffic offloading to the heterogeneous network based on the traffic offloading related information, and when the traffic offloading is performed, A message for offloading traffic determined based on loading-related information is transmitted to a packet data network gateway (P-GW), and traffic off-loading is performed to the heterogeneous network.

Using the proposed method, the base station can efficiently offload the terminals in the base station to the wireless LAN network while minimizing the effect on the existing standard without the ANDSF server. Also, even when the terminal is offloaded to the wireless LAN, the terminal can still receive services (e.g., voice service, SMS, etc.) that are connected to the mobile communication network and must be received through the mobile communication network.

1 is a diagram showing the structure of an LTE system to which an embodiment of the present invention is applied.
2 is a diagram illustrating a wireless protocol structure in an LTE system to which an embodiment of the present invention is applied.
3 is a diagram illustrating an example of a scenario in which an ANDSF is used to interwork between a 3GPP network and a wireless LAN network.
4 is a diagram illustrating an example of a scenario of a method for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed by an embodiment of the present invention.
FIG. 5 is a diagram illustrating a method example 2 of a method for offloading a terminal when interworking between 3GPP and a wireless LAN proposed by an embodiment of the present invention.
6 is a diagram illustrating a method example 3 of a method for offloading a terminal when interworking between 3GPP and a wireless LAN proposed by an embodiment of the present invention.
FIG. 7 is a diagram illustrating a message flow of an example of a scenario scenario example 1 for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed by an embodiment of the present disclosure.
FIG. 8 is a diagram illustrating a message flow of a method example scenario 2 in which a terminal is offloaded when an embodiment of the present invention proposes a 3GPP interworking with a wireless LAN.
FIG. 9 is a diagram illustrating a message flow of a method example 3 of a method scenario for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed by an embodiment of the present disclosure.
FIGS. 10A and 10B are exemplary diagrams showing the operation sequence of the terminal according to the embodiment of the present invention.
11 is a diagram illustrating an operation sequence of a base station according to an embodiment of the present invention.
FIG. 12 is an apparatus diagram illustrating a configuration of a terminal according to an embodiment of the present invention.
13 is an apparatus diagram showing a configuration of a base station according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the embodiments of the present invention, descriptions of techniques which are well known in the technical field of the present invention and are not directly related to the present invention will be omitted. This is for the sake of clarity of the present invention without omitting the unnecessary explanation.

For the same reason, some of the components in the drawings are exaggerated, omitted, or schematically illustrated. Also, the size of each component does not entirely reflect the actual size. In the drawings, the same or corresponding components are denoted by the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

At this point, it will be appreciated that the combinations of blocks and flowchart illustrations in the process flow diagrams may be performed by computer program instructions. These computer program instructions may be loaded into a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, so that those instructions, which are executed through a processor of a computer or other programmable data processing apparatus, Thereby creating means for performing functions. These computer program instructions may also be stored in a computer usable or computer readable memory capable of directing a computer or other programmable data processing apparatus to implement the functionality in a particular manner so that the computer usable or computer readable memory The instructions stored in the block diagram (s) are also capable of producing manufacturing items containing instruction means for performing the functions described in the flowchart block (s). Computer program instructions may also be stored on a computer or other programmable data processing equipment so that a series of operating steps may be performed on a computer or other programmable data processing equipment to create a computer- It is also possible for the instructions to perform the processing equipment to provide steps for executing the functions described in the flowchart block (s).

In addition, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative implementations, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may actually be executed substantially concurrently, or the blocks may sometimes be performed in reverse order according to the corresponding function.

Herein, the term " part " used in the present embodiment means a hardware component such as software or an FPGA or an ASIC, and 'part' performs certain roles. However, 'part' is not meant to be limited to software or hardware. &Quot; to " may be configured to reside on an addressable storage medium and may be configured to play one or more processors. Thus, by way of example, 'parts' may refer to components such as software components, object-oriented software components, class components and task components, and processes, functions, , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and components may be further combined with a smaller number of components and components or further components and components. In addition, components and " parts " may be embodied to reproduce one or more CPUs in a device or a secure multimedia card. In the following description of the embodiments of the present specification, The detailed description will be omitted when it is determined that the description of the present invention may unnecessarily obscure the gist of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

For convenience of description, the embodiments of the present invention are described on the basis of an LTE system as an example of a cellular network, but may be applied to other cellular networks (for example, UMTS).

1 is a diagram showing the structure of an LTE system to which an embodiment of the present invention is applied.

Referring to FIG. 1, a radio access network of an LTE system includes an Evolved Node B (hereinafter, referred to as an ENB, a Node B or a base station) 105, a Mobility Management Entity (MME) And an S-GW 130 (Serving-Gateway). A user equipment (UE) 135 accesses the external network through the ENBs 105 to 120 and the S-GW 130.

In FIG. 1, the ENBs 105 to 120 correspond to the existing node B of the UMTS system. The ENB is connected to the UE 135 via a radio channel and plays a more complex role than the existing Node B. In the LTE system, since all user traffic including a real-time service such as Voice over IP (VoIP) over the Internet protocol is serviced through a shared channel, status information such as buffer status, available transmission power status, And the ENBs 105 to 120 take charge of the scheduling. One ENB normally controls a plurality of cells. For example, in order to realize a transmission rate of 100 Mbps, an LTE system uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology, for example, at a bandwidth of 20 MHz. In addition, Adaptive Modulation and Coding (AMC) scheme is used to determine a modulation scheme and a channel coding rate in accordance with a channel state of a UE. The S-GW 130 is a device that provides a data bearer and generates or removes a data bearer under the control of the MME 125. [ The MME is a device that performs various control functions as well as a mobility management function for a terminal, and is connected to a plurality of base stations.

2 is a diagram illustrating a wireless protocol structure in an LTE system to which an embodiment of the present invention is applied.

Referring to FIG. 2, the wireless protocol of the LTE system includes Packet Data Convergence Protocols (PDCP) 205 and 240, RLC (Radio Link Control) 210 and 235, and MAC (Medium Access Control) 215 and 230 in the UE and the ENB, respectively. The PDCP (Packet Data Convergence Protocol) 205 and 240 are responsible for operations such as IP header compression / decompression and Radio Link Control (RLC) 210 and 235 are PDCP PDU ) To an appropriate size. The MACs 215 and 230 are connected to a plurality of RLC layer devices configured in a terminal, multiplex RLC PDUs into MAC PDUs, and demultiplex RLC PDUs from MAC PDUs. The physical layers 220 and 225 perform channel coding and modulation on the upper layer data, transmit them to a wireless channel by making OFDM symbols, demodulate OFDM symbols received through a wireless channel, channel-decode and transmit the OFDM symbols to an upper layer . Also, in the physical layer, HARQ (Hybrid ARQ) is used for additional error correction. In the receiving end, transmission of the packet transmitted from the transmitting end is carried out with 1 bit. This is called HARQ ACK / NACK information. The downlink HARQ ACK / NACK information for uplink transmission is transmitted through a PHICH (Physical Hybrid-ARQ Indicator Channel) physical channel, and the uplink HARQ ACK / NACK information for downlink transmission includes a Physical Uplink Control Channel (PUCCH) (Physical Uplink Shared Channel) physical channel.

According to the embodiment, when the mobile station is offloading to the wireless LAN network, for example, when there are not many mobile stations in the base station, it may not be necessary to offload the terminals in the base station to the wireless LAN network. On the other hand, for example, when there are many terminals in the base station and a large amount of traffic is generated due to congestion, it is necessary to offload the terminal.

In 3GPP standardization, a framework for interworking with a 3GPP network (including UMTS and LTE) and a wireless LAN network is defined, and an access network discovery and selection function (hereinafter referred to as ANDSF) do.

3 is a diagram illustrating an example of a scenario in which an ANDSF is used to interwork between a 3GPP network and a wireless LAN network.

Referring to FIG. 3, in this scenario, the terminal receives a network selection policy 325 for selecting the 3GPP network or the wireless LAN network from the ANDSF server 317, and according to the received network selection policy, And selects an access network (i.e., a 3GPP network and / or a wireless LAN network). Examples of the network selection policy include a case where the access priority of a wireless LAN network having a specific wireless LAN identifier is set to the highest priority when the terminal is connected to a specific carrier 3GPP network and if the wireless LAN is present around the terminal If not, there may be a policy of accessing the second-ranked 3GPP network.

Meanwhile, the network selection policy may include a policy for selecting only one of the 3GPP network and the wireless LAN network, or may include a policy for simultaneously operating the 3GPP network and the wireless LAN network. For example, when a terminal uses a Voice over Internet Protocol (VoIP) service, VoIP packets are always received through a 3GPP network for seamless service, And receive a policy for accessing the network or the wireless LAN to receive the service.

In order to inform that the specific traffic is to be offloaded as described above, there are two units of the network selection policy, one of which can offload the access point name (APN) And the other can be offloaded in an Internet Protocol (IP) flow unit. The APN is a name of a gateway device between a 3GPP network and another external network (e.g., the Internet), and a terminal can set up the APN information so that specific traffic can communicate through the gateway. That is, when offloading in units of the APN, all the traffic communicating through the APN is offloaded to the WLAN. When offloading is performed on the basis of the IP flow unit, offsets are performed on flows corresponding to the IP address and the port number specified in the network selection policy.

If the UE performs offloading in units of APN or IP flow as described above, the UE determines whether to offload according to conditions specified in the network selection policy, and if the condition is met, (E.g., PDN-GW, 331) to the corresponding network (e.g., a wireless LAN network or a 3GPP network). That is, when the terminal requests the PDN-GW to transfer the traffic to another network, it requests to be moved on an APN basis or to be moved to a specific IP flow unit.

The policy may include various conditions at the time of selecting the wireless LAN and the 3GPP network as well as the above example. For example, when the access point (AP) having a low load of the wireless LAN is used, It is possible to limit the selection of the wireless LAN network. For example, in the network selection policy 325, there is included a policy of 'access priority is higher than that of the 3GPP network for APs whose channel utilization is less than 50% When searching for the neighboring wireless LAN network, the terminal receives the channel utilization level of the corresponding AP from the searched AP 313 (323), determines whether it meets the condition, and determines whether or not the access point is connected to the AP.

However, the above method has a problem that the network selection can not be performed by reflecting the load state of the base station of the 3GPP network. The ANDSF server 317 must be introduced and retained by the provider in order to transmit the network selection policy. If the provider does not introduce the ANDSF server 317, the ANDSF server 317 If there is no client capable of receiving the network selection policy from the client, the above solution can not be used.

It is suggested that the base station 317 transmits a value related to the offload probability to the terminals 315 in the base station 317 in this embodiment. When the terminal receives the offload probability value from the base station, the terminal generates a random value between 0 and 1 excluding 1 (i.e., 0 <= generated value <1) Try to offload to the LAN network. According to the embodiment, the generated value may be configured as 0 < generated value < = 1.

Also, when the off-load probability is reduced as described above, information on which unit is to be off-loaded can be selectively provided, and off-loading can be instructed in the following units.

- Offload all traffic

- Offload in APN units

- When the APN unit is used, APN list information can be included

- APN list information is set to the base station by a separate method

- Offload in bearer units

- The bearer is a concept of virtual path between the terminal and the base station or between the terminal and the PDN-GW, and can perform offload to the terminal in the bearer unit.

- when the bearer unit is used, a bearer identifier (e.g., a data radio bearer identifier (hereinafter referred to as &quot; drb-Identity &quot;))

Upon receiving the command, the terminal requests an offload to the PDN-GW if there is a wireless LAN AP available in the vicinity.

- Offload all traffic

- an offload request for all APNs held by the terminal, or

- Offload requests (using wildcards) for all IP flows that the terminal has.

- Offload in APN units

- Compares the received APN list with the list of APNs held by the terminal, and notifies the PDN-GW of the corresponding APN only

- Offload in bearer units

- The terminal converts the received bearer into an IP flow and informs the PDN-GW of the converted IP flow information

In addition, the MS can selectively inform the PDN-GW by including an 'No Bearer Deactivation' indicator or flag. Upon receiving the No Bearer Deactivation request, the PDN-GW does not issue a command to disconnect the UE from the 3GPP network, but instead registers the PDN-GW in a registered state to enable services available in the cellular network (e.g., SMS service, etc.).

The embodiment of the present invention proposes a method of offloading a mobile station to a wireless LAN network when a mobile communication network (e.g., UMTS, LTE, etc.) is interworked with a wireless LAN network in a wireless communication system. The present invention enables a base station to efficiently off-load terminals in a base station to a wireless LAN network, and even when the terminal is offloaded to a wireless LAN, services (e.g., For example, voice service, SMS, etc.).

FIG. 4 is a diagram illustrating a method example of a method for offloading a terminal when interworking between 3GPP and a wireless LAN proposed in the embodiment of the present invention.

Referring to FIG. 4, in the case of the first embodiment, it is assumed that a scenario in which there is no ANDSF server described in FIG. 3 and that all traffic is transferred from the 3GPP network to the WLAN. Scenarios for offloading traffic in embodiments may be used interoperatively between embodiments.

In FIG. 4, the terminal 415 receives an offload related message from the base station 411 (421). The offload related message 421 may be transmitted in a message of a radio resource control (RRC) layer and may be transmitted in a broadcast or unicast. If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information is included in the offload related message 421. The 'offload probability' value may indicate a probability that the UE performs offload from the 3GPP network to another network (for example, a wireless LAN network). In addition, the offload related message 421 may optionally include 'offload type' information, which may include a value indicating which unit to offload the traffic.

In the present embodiment, a scenario is assumed in which all the traffic is transferred from the 3GPP network to the WLAN, and therefore, a value corresponding to 'all traffic movement' may be included in the 'offload mode'. If only the scenario for moving all the traffic is considered among the various scenarios to be listed in the present invention, it is assumed that the terminal moves all the traffic even if the 'offload type' value is not included.

If there is a setting in the terminal 415 that the wireless LAN related module of the terminal 415 is powered off or the user does not prefer to use the wireless LAN, the received value is ignored.

However, if the terminal 415 can access the wireless LAN 413, the terminal 415 generates a random value between 0 and 1 excluding 0 (i.e., 0 < = 0) Generated value <1). If the generated value is smaller than the value of the 'offload probability' value received from the BS 411, the BS attempts to offload the WLAN to the WLAN (423).

For example, if the base station 411 sets the value of the 'offload probability' to 1 (i.e., 100%), the terminal 415 always attempts to offload because it is a value smaller than 1 even if any value is generated . On the other hand, if the base station 411 sets the value of the 'offload probability' to 0 (that is, 0%), the terminal 415 does not attempt to offload because it is 0 even if it generates the smallest value.

If the base station 411 sets the value of the 'offload probability' to 0.5 (that is, 50%), the terminal 415 tries to offload at a probability of 50% according to the generated random value.

Even if the terminal 415 determines to attempt offloading as described above, the terminal 415 can access the AP and perform off-loading only when a wireless LAN AP 413 capable of accessing the periphery is searched. Accordingly, when it is determined to try to offload according to the received 'offload probability' value, the terminal 415 searches for a signal transmitted from the neighboring WLAN AP 413 and attempts connection (425 ).

The signal transmitted from the WLAN AP 413 may include a 'Beacon' message or a 'Probe Response' message.

If the terminal 415 succeeds in connection with the WLAN AP 413, the terminal 415 can stop data communication with the 3GPP network and perform data communication with the WLAN network, And transmits a message to the PDN-GW through the WLAN, which is successfully connected, to inform the corresponding 3GPP network of the fact (435). The operation of the identification number 435 may be performed through a Binding Update

At this time, since it is assumed that all the traffic is moved by the terminal 415 in the embodiment, an offload request including all the APNs held by the terminal 415 is included in the message, or the terminal 415 holds Lt; RTI ID = 0.0 &gt; (435) &lt; / RTI &gt;

Alternatively, when offload is requested to all IP flows in place of all APN information in the message, the PDN-GW 431 is turned off using a wildcard character (for example, the * character means all numbers) And requests a load (435).

In addition, if the terminal 415 offloads all the traffic from the 3GPP network to the WLAN, the traffic of the corresponding terminal is not transmitted to the 3GPP network. Therefore, the PDN-GW 431 transmits the terminal 415 information It is not necessary to hold the terminal 415, and the terminal 415 can be disconnected. If the terminal 415 is disconnected from the terminal 415, the terminal 415 is no longer able to listen to a message from the 3GPP network and can not receive an important service (e.g., a voice call service or a short message service SMS )) And the like can not be received.

In order to solve this problem, in the embodiment of the present invention, the 'No Bearer Deactivation' indicator or flag is included in the message sent from the terminal 415 to the PDN-GW 431 . The terminal 415 may inform the PDN-GW 431 not to deactivate the bearers held by the corresponding terminal 415, including the indicator.

Then, the PDN-GW 431 transmits the corresponding traffic to the 3GPP network to the WLAN, and offloads the traffic of the corresponding terminal to the WLAN.

FIG. 5 is a diagram illustrating a method example 2 for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed in the embodiment of the present invention.

Referring to FIG. 5, a scenario assuming that there is no ANDSF server described in FIG. 3 is assumed in the present exemplary embodiment, and a scenario in which only traffic transmitted through a specific APN among terminal traffic is transferred from a 3GPP network to a wireless LAN network is assumed.

In an embodiment, the terminal 515 receives an offload related message from the base station 511 (521). The offload related message may be transmitted as a message of the RRC layer and may be transmitted by broadcast or unicast. If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information is included in the offload related message. The 'offload probability' value means a probability that the UE performs offload from the 3GPP network to another network (for example, a WLAN). Optionally, 'offload type' information may be included, which is a value indicating which unit to offload the traffic. In this embodiment, a scenario is assumed in which only traffic transmitted through a specific APN among terminal traffic is transferred from the 3GPP network to the wireless LAN network. Therefore, a value corresponding to 'APN unit traffic movement' may be included in the ' . If only the scenario in which only the traffic transmitted through the specific APN among the traffic of the UE is transferred from the 3GPP network to the WLAN network among the various scenarios to be listed in the present invention is considered, The terminal may assume that only the traffic transmitted through the specific APN among the terminal traffic is transferred from the 3GPP network to the wireless LAN network. In addition, since only the traffic transmitted through the specific APN is transferred from the 3GPP network to the wireless LAN network, APN information used by the traffic that can be transferred to the wireless LAN network is transmitted. The APN information may be set manually by the service provider to the base station or may be set to the base stations collectively through an operation and management server (hereinafter referred to as O & M server) (543).

If the power of the wireless LAN module of the terminal 515 is turned off or a setting that the user does not prefer the wireless LAN exists in the terminal 515, the received value can be ignored.

However, if the terminal 515 can access the wireless LAN, the terminal 515 generates a random value between 0 and 1 except for 0 (i.e., 0 <= generation value < One). If the generated value is smaller than the value of the 'offload probability' value received from the base station, it attempts to offload to the WLAN (523).

For example, if the base station 511 sets the value of the 'offload probability' to 1 (i.e., 100%), the terminal 515 tries to always offload because it is a value smaller than 1 even if any value is generated . On the other hand, if the base station 511 sets the value of the 'offload probability' to 0 (i.e., 0%), the terminal 515 does not attempt to offload because it is 0 even if it generates the smallest value. If the base station 511 sets the 'offload probability' value to 0.5 (i.e., 50%), the terminal 515 tries to offload with 50% probability according to the generated random value.

Even when the terminal 515 determines to attempt the offload as described above, the terminal 515 connects to the wireless LAN AP 513 only when the wireless LAN access point 513 capable of accessing to the surrounding area is searched, .

Accordingly, when the terminal 515 decides to try to offload according to the received 'offload probability' value, the terminal 515 searches for a signal transmitted from the neighboring WLAN AP 513, (525). The signal transmitted from the WLAN AP may include a 'beacon' message or a 'probe response' message.

If the terminal 545 successfully connects to the WLAN AP 513, the terminal 515 stops data communication with the 3GPP network, performs data communication with the wireless LAN network, And transmits a message to the PDN-GW 531 through the successful wireless LAN network in order to inform the network of the fact (535).

At this time, since it is assumed that only the traffic transmitted through the specific APN among the terminal traffic is transferred from the 3GPP network to the wireless LAN network, among the APNs currently held and maintained by the terminal 515, The APN information 521 received from the PDN-GW 531 is compared with the received APN information 521, and the PDN-GW 531 may request the PDN-GW 531 to offload the APN information 521.

In addition, if the terminal 515 offloads all the traffic from the 3GPP network to the WLAN, the PDN-GW 531 transmits the information of the corresponding terminal 515 because the traffic of the corresponding terminal is not transmitted to the 3GPP network. It is not necessary to hold the terminal 515, and the terminal 515 can be disconnected. If the terminal 515 is disconnected, the terminal 515 can no longer receive any message from the 3GPP network. In this case, there is a danger that the terminal 515 may become unable to receive an important service (for example, a voice call service or a short message service (SMS)). In order to solve this problem, in this embodiment, a message to be transmitted to the PDN-GW 531 by the terminal 515 includes an indicator 'No Bearer Deactivation' . The UE 515 may inform the PDN-GW 531 not to deactivate bearers held by the UE, including the indicator.

Then, the PDN-GW 531 transmits the corresponding traffic to the WLAN to the 3GPP network and offloads the traffic of the corresponding terminal 515 to the WLAN.

FIG. 6 is a diagram illustrating a method example 3 of a method for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed in the embodiment of the present invention.

Referring to FIG. 6, a scenario assuming that there is no ANDSF server described in FIG. 3 is assumed, and a scenario in which only traffic transmitted through a specific bearer among the terminal's traffic is transferred from the 3GPP network to the WLAN network is assumed. The bearer is a virtual channel concept in which traffic flows between a terminal and a base station or between a terminal and a PDN-GW. In this scenario, it is assumed that the bearer is offloaded to the terminal. For reference, the bearer unit is a more detailed concept than the APN unit described in FIG. 5, and one or a plurality of bearers may be associated with one APN.

In an embodiment, the terminal 615 receives an offload related message from the base station 611 (621). The offload related message may be transmitted as a message of the RRC layer and may be transmitted by broadcast or unicast. If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information may be included in the offload related message. The 'offload probability' value means a probability that the UE performs offload from the 3GPP network to another network (for example, a WLAN). Optionally, 'offload type' information may be included, which is a value indicating which unit to offload the traffic.

In this embodiment, a scenario is assumed in which only the traffic transmitted through a specific bearer among the UEs 'traffic is transferred from the 3GPP network to the WLAN network. Therefore, a value corresponding to' bearer-based traffic movement 'may be included in the' . When considering only scenarios in which only the traffic transmitted through a specific bearer among the UE traffic from the 3GPP network to the WLAN network is included among the various scenarios to be listed in this embodiment, the 'offload type' value is not included It is assumed that only traffic transmitted through a specific bearer among the UE traffic is transferred from the 3GPP network to the WLAN. In addition, since only the traffic transmitted through a specific bearer is transferred from the 3GPP network to the WLAN, it is assumed that the bearer information used by the traffic that can be transferred to the WLAN network is transmitted. In order to inform the bearer information, a bearer identifier may be used, for example, a data radio bearer identifier (DRB-Identity) or an evolved packet system (EPS) bearer identifier (Hereinafter referred to as &quot; eps-BearerIdentity &quot;). In order for the BS to select bearers used by the traffic that can be transferred to the WLAN among bearers owned by the MSs, a Quality of Service Class Identifier (hereinafter referred to as QCI) value set for each bearer . &Lt; / RTI &gt; Table 1 below shows the QCI value-specific characteristics defined in the 3GPP standard 23.202 document. For example, the bearer with the lowest priority QCI value of 9 can be offloaded (to the wireless LAN network) A method of judging a bearer can be used.

Q CI R esource
Type P riority P acket
Delay
Budget P acket
Error
Loss
Rate Example Services One GBR 2 100 ms 10 ^-2 Conversational Voice 2 4 150 ms 10 ^-3 Conversational Video (Live Streaming) 3 3 50 ms 10 ^-3 Real Time Gaming 4 5 300 ms 10 ^-6 Non-Conversational Video (Buffered Streaming) 5 Non-GBR One 100 ms 10 ^-6 IMS Signaling 6 6 300 ms 10 ^-6 Video (Buffered Streaming), TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.) 7 7 100 ms 10 ^-3 Voice, Video (Live Streaming), Interactive Gaming 8 8 300 ms 10 ^-6 Video (Buffered Streaming), TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.) 9 9

On the other hand, if the wireless LAN related module of the terminal 615 is powered off or the user does not prefer the wireless LAN, the terminal 615 ignores the received values.

However, if the terminal 615 can access the wireless LAN, the terminal generates a random value between 0 and 1 excluding 1 (i.e., 0 <= generation value <1). If the generated value is smaller than the value of the 'offload probability' value received from the base station 611, it attempts to offload to the wireless LAN network (623).

For example, if the base station 611 sets the value of the 'offload probability' to 1 (i.e., 100%), the terminal 615 always attempts to offload because it is a value smaller than 1 even if any value is generated . On the other hand, when the base station 611 sets the value of the 'offload probability' to 0 (i.e., 0%), the terminal 615 does not attempt to offload because it is 0 even if it generates the smallest value. If the base station 611 sets the value of the 'offload probability' to 0.5 (that is, 50%), the terminal 615 tries to offload at a probability of 50% according to the generated random value.

Even if the terminal 615 decides to attempt the offload as described above, the terminal 615 can access the AP and perform the off-loading only when the wireless LAN AP 613 capable of accessing the periphery is searched. Accordingly, if it is determined to try to offload according to the received 'offload probability' value, the terminal 615 searches for a signal transmitted from the neighboring WLAN AP 613 and attempts connection (625 ). The signal transmitted from the WLAN AP 613 may include a 'beacon' message or a 'probe response' message.

If the terminal successfully connects to the WLAN AP 613, the terminal 615 can stop data communication with the 3GPP network and perform data communication with the WLAN. Accordingly, in order to inform the currently connected 3GPP network of the fact, a message is transmitted to the PDN-GW 631 through the successful wireless LAN network (635). In this case, since it is assumed that only the traffic transmitted through the specific bearer among the traffic of the UE is transferred from the 3GPP network to the WLAN, the UE 615 transmits the bearer And compares the bearer information 621 with the bearer information included in the message, and requests the PDN-GW to offload the bearer information 625 (635). However, only the APN information or the IP flow information is available as the information included in the message in the current standard, as described above. Therefore, in the present embodiment, the terminal 615 converts the bearer information for performing the offload into IP flow information so as to reuse the current standard as much as possible, and includes traffic information to be offloaded in the message (624).

In addition, if the terminal 615 offloads all the traffic from the 3GPP network to the WLAN, the traffic of the corresponding terminal 615 is not transmitted to the 3GPP network. Therefore, the PDN-GW 631 transmits the terminal information It is not necessary to hold it, and the connection of the terminal can be canceled. If the terminal 615 is disconnected from the 3GPP network, the terminal 615 can not receive any message from the 3GPP network and can not receive an important service (for example, a voice call service or SMS) There is a risk that the user can not receive the service. Accordingly, in order to solve such a problem, the present invention includes a 'No Bearer Deactivation' indicator or flag in a message sent to the PDN-GW 631 by the terminal. Including the indicator, the terminal 615 can inform the PDN-GW not to deactivate the bearers held by the corresponding terminal.

Then, the PDN-GW 631 transmits the corresponding traffic to the 3GPP network to the WLAN and offloads the traffic of the corresponding terminal to the WLAN.

FIG. 7 is a diagram illustrating a message flow of an example of a scenario method example 1 for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed in the embodiment of the present invention described above.

Referring to FIG. 7, it is assumed that all traffic is transferred from the 3GPP network to the WLAN as shown in FIG. In this scenario, not only the scenario in which the terminal 701 establishes a connection establishment procedure with the base station 705 and the base station defined in 3GPP (step 711), considering a scenario in which data transmission / reception is possible (the terminal is 'RRC connected' RRC_CONNECTED) state), a scenario in which only the base station signal is monitored (the terminal is in 'RRC_IDLE' state) without performing the connection establishment procedure (step 711) Is also applicable. That is, the present invention is applicable to any case where the terminal 701 is in the RRC_CONNECTED state or the RRC_IDLE state.

The terminal 701 determines whether the terminal 701 is offloaded to the wireless LAN according to the current terminal setting and status (step 715). For example, if the power of the wireless LAN module of the terminal 701 is turned off, or if there is a setting in the terminal that the user does not prefer the wireless LAN, the terminal 701 does not perform offload and does not search for an unnecessary wireless LAN signal (Step 723).

Then, the terminal 701 receives an offload related message from the base station (step 717). The offload related message may be transmitted as a message of the RRC layer and may be broadcast (common) or unicast (dedicated). If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information may be included in the offload related message. The 'offload probability' value means a probability that the UE performs offload from the 3GPP network to another network (for example, a WLAN). Optionally, 'offload type' information may be included, which is a value indicating which unit to offload the traffic. In the present embodiment, a scenario is assumed in which all the traffic is transferred from the 3GPP network to the WLAN, and therefore, a value corresponding to 'all traffic movement' may be included in the 'offload mode'. If only the scenario for moving all the traffic is considered among the various scenarios to be listed in the present invention, even if the 'offload type' value is not included, the terminal 701 can assume that all traffic is moved have.

If the terminal 701 can access the wireless LAN network, the terminal 701 generates a random value between 0 and 1 excluding 0 (i.e., 0 <= generated value <1 ). If the generated value is smaller than the value of the 'offload probability' value received from the base station, it attempts to offload to the wireless LAN network (step 731).

For example, if the base station 705 sets the value of the 'offload probability' to 1 (i.e., 100%), the terminal 701 will always try to offload because it is smaller than 1 even if any value is generated (Step 731). On the other hand, if the BS 705 sets the 'offload probability' value to 0 (i.e., 0%), the terminal 701 does not attempt to offload because it is 0 even if it generates the smallest value (step 721) . If the base station 705 sets the 'offload probability' value to 0.5 (i.e., 50%), the terminal 701 tries to offload with 50% probability according to the generated random value.

If the terminal 701 decides not to perform the offload according to the above procedure, the terminal does not search for an unnecessary wireless LAN signal and saves the consumed power (step 723). On the other hand, even if the terminal 701 decides to try to offload, the terminal 701 can access the AP and perform offloading only when the wireless LAN AP 703 capable of accessing the surrounding area is searched have. Accordingly, when the terminal 701 determines to attempt to offload according to the received 'offload probability' value, the terminal 701 searches for a signal transmitted from the neighboring WLAN AP 703 (step 733) and attempts connection (step 737). A beacon message or a probe response message may be transmitted from the WLAN AP 703 (step 735).

If the terminal 701 has successfully connected to the WLAN AP 703 (step 737), the terminal 701 suspends data communication with the 3GPP network and performs data communication with the wireless LAN network 701, In order to report the fact to the currently connected 3GPP network, a message is transmitted to the PDN-GW 707 through the successful wireless LAN network (step 741). At this time, since it is assumed that all the traffic is moved, the terminal 701 includes all the APNs held by the terminal 701 in the message for an offload request, or all IPs held by the terminal 701 Information about the flows in the message (step 739), and transmits a message requesting the offload to the PDN-GW 707 (step 741). Alternatively, in the case of requesting offload for all IP flows in place of all APN information in the message, a wildcard character (for example, the * character means all numbers) may be included in the message.

In addition, if the UE 701 offloads all the traffic from the 3GPP network to the WLAN, the traffic of the UE is not transmitted to the 3GPP network. Therefore, the PDN-GW 707 needs to have the corresponding UE information And the connection of the terminal can be canceled. If the terminal 701 is disconnected from the terminal 701, the terminal 707 is no longer able to listen to a message from the 3GPP network and can not receive an important service (e.g., voice call service or short message service )) And the like can not be received. Therefore, in order to solve such a problem, the present invention includes a 'No Bearer Deactivation' indicator or flag in a message sent from the UE to the PDN-GW 707. [ The terminal 701 may inform the PDN-GW not to deactivate the bearers held by the corresponding terminal 701, including the indicator.

Then, the PDN-GW 707 transmits the corresponding traffic to the WLAN, and offloads the traffic of the corresponding terminal to the WLAN.

FIG. 8 is a diagram illustrating a message flow of an exemplary method scenario example 2 in which the terminal is offloaded when interworking between a 3GPP and a wireless LAN proposed in the embodiment of the present invention described above.

Referring to FIG. 8, it is assumed that only traffic transmitted through a specific APN among the terminal's traffic is transferred from the 3GPP network to the WLAN as shown in FIG. Also, in this scenario, the terminal 801 performs a connection establishment procedure defined in 3GPP with the base station 805 (step 811), not only considering a scenario in which data transmission / reception is possible, but also performs the connection establishment procedure (step 811) A scenario in which only the base station signal is monitored is applicable. That is, the present invention is applicable to any case where the terminal 801 is in the RRC_CONNECTED state or the RRC_IDLE state.

The base station 805, on the other hand, does not know which traffic through which APNs can be offloaded, so that information on this is additionally needed. Accordingly, the list information for the one or more APNs that can be offloaded can be manually set up by the business or can be set to the base station through the O & M server 809 (step 813).

The terminal 801 determines whether the terminal 801 is offloaded to the wireless LAN according to the setting and the state of the current terminal 801 (step 815). For example, if the power of the wireless LAN module of the terminal 801 is turned off, or if the user does not prefer the wireless LAN, the terminal 801 does not perform offloading, (Step 823).

Then, the terminal 801 receives an offload related message from the base station (step 817). The offload related message may be transmitted as a message of the RRC layer and may be broadcast (common) or unicast (dedicated). If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information is included in the offload related message. The 'offload probability' value means a probability that the terminal 801 performs offload from the 3GPP network to another network (for example, a wireless LAN network). Optionally, 'offload type' information may be included, which is a value indicating which unit to offload the traffic. In this embodiment, since only the traffic transmitted through the specific APN among the traffic of the terminal 801 is transferred from the 3GPP network to the WLAN, the value corresponding to 'APN unit traffic movement' . In the case of considering only scenarios in which only the traffic transmitted through the specific APN among the traffic of the UE 801 from the 3GPP network to the wireless LAN network among the various scenarios to be listed in the embodiment of the present invention, The terminal 801 can assume that only the traffic transmitted through the specific APN among the terminal's traffic is transferred from the 3GPP network to the WLAN. In addition, since it is assumed that only the traffic transmitted through a specific APN is transferred from the 3GPP network to the wireless LAN network, the base station 805 transmits the acquired APN list to the mobile station with 'APN information' 817).

If the terminal 801 is able to access the wireless LAN, the terminal generates a random value between 0 and 1 excluding 1 (i.e., 0 <= generation value <1). If the generated value is smaller than the value of the 'offload probability' received from the base station 805, the mobile station attempts to offload to the wireless LAN network (step 831). For example, if the base station sets the value of the 'offload probability' to 1 (i.e., 100%), the terminal always attempts to offload (831) since it is smaller than 1 even if any value is generated. On the other hand, if the BS 805 sets the value of the 'offload probability' to 0 (i.e., 0%), the UE does not attempt to offload the UE even if it generates the smallest value (step 821). If the base station 805 sets the value of the 'offload probability' to 0.5 (i.e., 50%), the terminal attempts to offload at a probability of 50% according to the generated random value.

If the terminal 801 decides not to perform the offload according to the above procedure, the terminal 801 can save the power consumption without searching for an unnecessary wireless LAN signal (step 823). On the other hand, even when the terminal 801 decides to attempt off-loading, the terminal 801 can access the wireless LAN AP 803 and perform off-loading only when the wireless LAN AP 803 capable of accessing the surrounding area is searched have. Accordingly, if it is determined to try to offload according to the received 'offload probability' value, the terminal 801 searches for a signal transmitted from the neighboring WLAN AP 803 (step 833) (Step 837). A beacon message or a probe response message may be transmitted from the WLAN AP 803 (step 835).

If the terminal succeeds in connection with the WLAN AP 803 (step 837), the terminal 801 can stop data communication with the 3GPP network and perform data communication with the wireless LAN network. Accordingly, the UE 801 transmits a message to the PDN-GW 807 via the WLAN, which is connected to the currently connected 3GPP network (step 841). In this case, since it is assumed that only the traffic transmitted through the specific APN among the terminal traffic is transferred from the 3GPP network to the wireless LAN network, among the APN currently held and maintained by the AT 801, (Step 817), and only the overlapping APNs are included in the message (step 839), and the PDN-GW may transmit a message requesting offload to the PDN-GW (step 841).

In addition, if the terminal 801 offloads the traffic transmitted through all the APNs from the 3GPP network to the WLAN, the traffic of the corresponding terminal is not transmitted to the 3GPP network, so that the PDN- It is not necessary to hold the information and the connection of the terminal 801 can be canceled. If the terminal 801 is disconnected from the corresponding terminal 801, the terminal 801 can no longer receive any messages from the 3GPP network and can transmit an important service (for example, a voice call service or a short message service )) And the like can not be received. Accordingly, in order to solve such a problem, the present invention includes a 'No Bearer Deactivation' indicator or flag in a message sent from the terminal 801 to the PDN-GW 807. The UE 801 may inform the PDN-GW 807 not to deactivate the bearers held by the UE, including the indicator.

Then, the PDN-GW 807 transmits the corresponding traffic to the 3GPP network to the WLAN and offloads the traffic of the corresponding terminal to the WLAN.

FIG. 9 is a diagram illustrating a message flow of an example of a method scenario 3 for offloading a terminal when interworking between a 3GPP and a wireless LAN proposed in the embodiment of the present invention described above.

Referring to FIG. 9, it is assumed that only traffic transmitted through a specific bearer among the UE traffic is transferred from the 3GPP network to the WLAN. The bearer is a virtual channel concept in which traffic flows between a terminal and a base station or between a terminal and a PDN-GW. In this scenario, it is assumed that the bearer is offloaded to the terminal. For reference, the bearer unit is a more detailed concept than the APN unit described in FIG. 5, and one or a plurality of bearers may be associated with one APN.

The terminal 901 performs a connection establishment procedure defined in 3GPP with the base station 905 (step 911), not only considering a scenario in which data transmission / reception is possible, but also performs the connection establishment procedure (step 911) A scenario in which only the base station 905 signal is monitored is applicable. That is, the present invention can be applied to any case where the terminal 901 is in the RRC_CONNECTED state or the RRC_IDLE state.

Meanwhile, the base station 905 needs a procedure for determining which bearers of the UE 901 are capable of offloading (step 913). To this end, the base station 905 can determine whether it is offloadable according to a Quality of Service Class Identifier (QCI) value set for each bearer held by the UEs 901 . Table 1 above refers to the QCI value-specific characteristics defined in the 3GPP standard 23.202 document. For example, it is assumed that bearers with the lowest QCI value of 9 can be offloaded A method of judging that the bearer is available) can be used.

The terminal 901 determines whether the terminal 901 is offloaded to the wireless LAN according to the current terminal setting and status (step 915). For example, when the power of the wireless LAN module of the terminal 901 is turned off or if the user does not prefer the wireless LAN, the terminal 901 does not perform offloading, It does not search (step 923).

Then, the terminal 901 receives an offload related message from the base station (step 917). The offload related message can be transmitted as a message of the RRC layer, and can be broadcast (common) or unicast (dedicated). If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information is included in the offload related message. The 'offload probability' value means a probability that the UE performs offload from the 3GPP network to another network (for example, a WLAN). Optionally, 'offload type' information may be included, which is a value indicating which unit to offload the traffic. In this embodiment, a scenario is assumed in which only the traffic transmitted through a specific bearer among the UEs 'traffic is transferred from the 3GPP network to the WLAN network. Therefore, a value corresponding to' bearer-based traffic movement 'may be included in the' . If only scenarios in which only traffic transmitted through a specific bearer among the UE traffic is transferred from the 3GPP network to the WLAN network among various scenarios to be listed in each embodiment of the present specification, It is assumed that only the traffic transmitted through a specific bearer among the UE traffic is transferred from the 3GPP network to the WLAN. In addition, since it assumes a scenario in which only the traffic transmitted through a specific bearer is transferred from the 3GPP network to the WLAN, the 'bearer information' used by the traffic that can be transferred to the WLAN network is transmitted. For informing the bearer information, a bearer identifier may be used. For example, a drb-Identity or an eps-BearerIdentity may be used.

If the terminal 901 can access the wireless LAN, the terminal 901 generates a random value between 0 and 1 excluding 0 (i.e., 0 <= generation value <1) . If the generated value is smaller than the value of the 'offload probability' value received from the base station 905, the mobile station attempts to offload to the wireless LAN network (step 931). For example, if the base station 905 sets the value of the 'offload probability' to 1 (that is, 100%), the terminal 901 always attempts to offload since it is smaller than 1 even if any value is generated (Step 931). On the other hand, if the base station 905 sets the value of the 'offload probability' to 0 (i.e., 0%), the terminal 901 does not try to offload because it is 0 even if it generates the smallest value (step 921) . If the base station 905 sets the value of the 'offload probability' to 0.5 (i.e., 50%), the terminal 901 tries to offload with 50% probability according to the generated random value.

If the terminal 901 decides not to perform the offload according to the above procedure, the terminal 901 can save power consumed because it does not search for an unnecessary wireless LAN signal (step 923). On the other hand, even when the terminal 901 decides to attempt off-loading, the terminal 901 can access the wireless LAN AP 903 and perform off-loading only when a wireless LAN AP 903 capable of accessing to the surrounding area is searched have. Accordingly, if it is determined to try to offload according to the received 'offload probability' value, the terminal 901 searches for a signal transmitted from the neighboring WLAN AP 903 (step 933) (Step 937). A beacon message or a probe response message may be transmitted from the wireless LAN AP 903 (step 935).

If the terminal 901 succeeds in connection with the WLAN AP 903 (step 937), the terminal 901 stops data communication with the 3GPP network and can perform data communication with the WLAN network have. In this case, the UE 901 transmits a message to the PDN-GW 907 via the WLAN, which is successfully connected, to notify the currently connected 3GPP network of the fact (step 941). In this case, since it is assumed that only the traffic transmitted through a specific bearer among the traffic of the UE 901 is transferred from the 3GPP network to the WLAN network, the UE 901 transmits the bearer (Step 917), and selects the bearers held by the terminal 901 among the bearer information transmitted by the base station 905 (step 917). On the other hand, only the APN information or the IP flow information is available as the information included in the message in the current standard, as described above. Accordingly, in the present invention, the terminal 901 converts the bearer information to be offloaded to IP flow information so as to reuse the current standard as much as possible, and transmits traffic information to be offloaded to the message (Step 939), and transmits a message requesting off-loading to the PDN-GW 907 (step 941).

In addition, if the terminal 901 offloads the traffic transmitted through all the APNs from the 3GPP network to the WLAN, the traffic of the corresponding terminal is not transmitted to the 3GPP network, so that the PDN- It is not necessary to hold the information, and the connection of the terminal 901 can be canceled. If the terminal 901 is disconnected from the corresponding terminal 901, the terminal 901 can no longer receive any message from the 3GPP network, )) And the like can not be received. Accordingly, in order to solve such a problem, the present invention includes a 'No Bearer Deactivation' indicator or flag in a message sent from the UE 901 to the PDN-GW 907. The UE can inform the PDN-GW 907 not to deactivate the bearers held by the corresponding UE 901, including the indicator.

Then, the PDN-GW 907 transmits the corresponding traffic to the 3GPP network to the WLAN, and offloads the traffic of the corresponding terminal to the WLAN.

FIGS. 10A and 10B are exemplary diagrams showing the operation sequence of the terminal according to the embodiment of the present invention.

Referring to FIGS. 10A and 10B, the UE may be in an RRC_CONNECTED state or a RRC_IDLE state in which data transmission / reception is possible by performing a connection establishment procedure with a BS (step 1003).

On the other hand, the terminal determines whether it is offloaded to the wireless LAN according to the current terminal setup and status (step 1004). For example, if the wireless LAN related module of the terminal is turned off, or if the user does not prefer the wireless LAN, the terminal does not perform offloading and does not search for an unnecessary wireless LAN signal (Step 1041).

If it is determined that it is possible to offload (step 1004), the terminal receives an offload related message from the base station (step 1005). Alternatively, the terminal may receive an offload related message from the base station (step 1005) and determine that it is possible for the terminal to offload (step 1004).

The offload related message may be transmitted as a message of the RRC layer and may be broadcast (common) or unicast (dedicated). If it is broadcast, it can be transmitted in the form of a system information block (System Information Block), which is a message for transmitting system information of the RRC layer.

The 'offload probability' information is included in the offload related message. The 'offload probability' value means a probability that the UE performs offload from the 3GPP network to another network (for example, a WLAN). Optionally, 'offload type' information may be included, which is a value indicating which unit to offload the traffic. If only one scenario is used, or if various scenarios are used, the 'offload type' information may be omitted if the parameter includes only the scenario.

The UE generates a random value between 0 and 1 excluding 0 (i.e., 0 <= generation value <1) and determines whether the value is smaller than the value of the 'offload probability' received from the base station (Step 1007).

If it is not small, it is determined that the terminal does not perform the offload (step 1009), and the terminal ends the procedure without performing the signal search of the unnecessary wireless LAN (step 1041).

If the generated value is small, it is determined to attempt to offload to the wireless LAN network (step 1009), and search for a signal transmitted from the neighboring wireless LAN AP is started (step 1011) The transmitted signal may be a 'beacon' message or a 'probe response' message.

If the UE succeeds in connection with the WLAN AP (step 1013), the UE generates a message according to another process according to which unit performs the offload, and transmits a message to the PDN-GW (step 1031 ).

If the 'offload type' is 'all traffic movement' in the RRC message received in step 1005 or only one scenario in which all traffic is moved, the 'offload type' is omitted (Step 1015), the terminal generates a message including all of the currently connected APN information or all IP flow information to be transmitted to the PDN-GW (step 1021). In addition, a 'No Bearer Deactivation' indicator may be included in the message to inform the PDN-GW not to deactivate the bearers held by the corresponding UE (step 1021).

If the 'offload type' is 'APN unit traffic movement' in the RRC message received in step 1005 or only one scenario is used to move traffic in APN units, the 'offload type' (Step 1017), it is determined that the 'APN information' is included in the received RRC message and the traffic is moved in units of APN implicitly (step 1017) (Step 1023), and generates a message to be transmitted to the PDN-GW including only the selected APN information (step 1025). In addition, the message may include a 'No Bearer Deactivation' indicator to inform the PDN-GW not to deactivate bearers held by the UE (step 1025).

If the 'offload type' is 'bearer unit traffic movement' in the RRC message received in step 1005, or the scenario in which traffic is moved in bearer units, the 'offload type' (Step 1019). If the bearer information is included in the received RRC message and the bearer information is implicitly considered as a bearer, Only the bearer information currently connected by the terminal is selected and the selected bearer information is converted into the IP flow information (step 1027). Thereafter, a message for transmitting the converted IP flow information to the PDN-GW is generated (step 1029). Also, a 'No Bearer Deactivation' indicator may be included in the message to inform the PDN-GW not to deactivate bearers held by the UE (step 1029).

The UE transmits the generated message to the PDN-GW through the connected AP (step 1031), and offloads the traffic of the corresponding terminal to the wireless LAN network.

11 is a diagram illustrating an operation sequence of a base station according to an embodiment of the present invention.

Referring to FIG. 11, the base station determines whether to transmit the offload-related parameters by broadcast (i.e., transmit to all terminals in the cell) or unicast (i.e., transmit to a specific terminal) ). When transmitting to a specific terminal, a terminal to transmit an offload related message is selected in consideration of the signal quality of terminals or the amount of traffic to be generated (step 1105).

Thereafter, the base station determines a probability of offloading (step 1107). For example, if the probability is set to 1, among the terminals receiving the message, the terminals that can offload to the wireless LAN all move the traffic to the wireless LAN. If the probability is set to 0, terminals that can offload to the wireless LAN among the terminals receiving the message do not perform offloading.

In addition, when transmitting the offload-related message, the base station generates a message through another procedure according to which unit is offloaded, and transmits the generated message to the mobile station (step 1141).

If all traffic of the terminal receiving the message is to be offloaded (step 1111), 'offload mode' is set to 'all traffic moves' (step 1113). If only one scenario for moving all traffic is used, step 1113 may be omitted if the 'offload mode' is omitted.

If it is desired to offload the traffic transmitted through the specific APN of the terminal receiving the message (step 1121), it is checked whether there is APN information that can be offloaded (step 1123). If not, And obtains APN information capable of being offloaded through communication with the O & M servers (step 1125). Thereafter, 'offload mode' is set to 'APN unit traffic movement', and the acquired APN information is included in the message (step 1127). Only one scenario for offloading the traffic transmitted through the specific APN of the MS is used, and if the 'offload type' is omitted, the offload type information may be omitted.

If it is desired to offload the traffic transmitted through the specific bearer of the UE receiving the message (step 1131), the BS checks QCI information of the bearer of the UE to determine bearers capable of being offloaded among the bearers (Step 1133). Then, the 'bearer unit traffic movement' is set to 'offload mode', and the determined bearer information is included in the message (step 1135). Only one scenario for offloading traffic transmitted through a specific bearer of the UE is used, and if the 'offload type' is omitted, the offload type information may be omitted.

Thereafter, the generated message is transmitted to the terminal according to the determination of step 1103 by broadcast or unicast (step 1141).

12 is a block diagram illustrating a configuration of a terminal according to an embodiment of the present invention.

12, a terminal according to an exemplary embodiment of the present invention includes a transmitter / receiver 1205, a controller 1210, a multiplexer / demultiplexer 1215, a control message processor 1230, and an upper layer processor 1220, .

The transceiver 1205 receives data and a predetermined control signal on a forward channel of a serving cell and transmits data and a predetermined control signal on a reverse channel. When a plurality of serving cells are set, the transmitting and receiving unit 1205 performs data transmission and reception and control signal transmission and reception through the plurality of serving cells.

The multiplexing and demultiplexing unit 1215 multiplexes the data generated in the upper layer processing unit 1220 and the control message processing unit 1230 or demultiplexes the data received in the transmission and reception unit 1205 and transmits the multiplexed data to an appropriate upper layer processing unit 1220, To the message processing unit 1230.

The control message processing unit 1230 processes the control message received from the base station and takes necessary actions. Upon receiving the RRC message used in the present invention, the UE determines whether or not the RRC message is offloaded according to the offload probability and type.

The upper layer processing unit 1220 may be configured for each service and may process data generated in a user service such as FTP (File Transfer Protocol) or VoIP (Voice over Internet Protocol) and transmit the processed data to the multiplexing and demultiplexing unit 1215 And processes the data transmitted from the multiplexing and demultiplexing unit 1215 and transfers the processed data to a higher layer service application.

The control unit 1210 checks the scheduling command, e.g., the reverse resource allocation position and amount received via the transceiver 1205, and outputs the scheduling command to the transmission / reception unit 1205 so that the reverse transmission is performed with an appropriate transmission resource at an appropriate time, And controls the multiplexing unit 1215.

In the present invention, it is assumed that the wireless LAN device 1245 coexists in the terminal. If the wireless LAN search / selection instruction unit 1240 proposed in the present invention determines that the wireless LAN device 1245 is in the off- And informs the LAN that the wireless LAN device 1245 of the terminal can search for and perform connection with the neighboring wireless LAN AP.

13 is a block diagram showing a configuration of a base station according to an embodiment of the present invention.

13, the base station apparatus of the embodiment includes a transmitter / receiver 1305, a controller 1310, a multiplexer / demultiplexer 1320, a control message processor 1335, upper layer processors 1325 and 1330, Scheduler 1315. &lt; / RTI &gt;

Transmitter / receiver 1305 transmits data and a predetermined control signal to a forward carrier and receives data and a predetermined control signal to a reverse carrier. When a plurality of carriers are set, the transmitting and receiving unit 1305 performs data transmission and reception and control signal transmission and reception with the plurality of carriers.

The multiplexing and demultiplexing unit 1320 multiplexes data generated in the upper layer processing units 1325 and 1330 and the control message processing unit 1335 or demultiplexes the data received in the transmission and reception unit 1305 and transmits the multiplexed data to an appropriate upper layer processing unit 1325 ) 1330, the control message processing unit 1335, or the control unit 1310. The control message processor 1335 processes the control message transmitted by the mobile station to perform a necessary operation or generates a control message to be transmitted to the mobile station and transmits the control message to the lower layer. The RRC message including the offload related parameters proposed by the present invention is also generated and transmitted by the control message processing unit.

The upper layer processing units 1325 and 1330 may be configured for each service for each terminal and may process data generated in a user service such as FTP and VoIP and transmit the processed data to the multiplexing and demultiplexing unit 1320 or the multiplexing and demultiplexing unit 1320 to the service application of the upper layer.

The control unit 1310 controls the transmitting and receiving unit according to the state of the signal quality or the like that the terminal can receive.

The scheduler 1315 allocates transmission resources to the terminal at an appropriate time in consideration of the buffer state of the terminal, the channel state, and the activity time of the terminal, processes the signal transmitted from the terminal to the transceiver, do.

Using the proposed method, the base station can efficiently offload the terminals in the base station to the wireless LAN network while minimizing the influence of the existing standard without the ANDSF server. Even when the terminal is offloaded to the wireless LAN, (E.g., voice service, SMS, etc.) that are connected to the network and must be received through the mobile communication network.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the scope of the appended claims, and equivalents thereof.

Claims (20)

A method of transmitting and receiving data in a terminal of a mobile communication system,
Receiving traffic offloading related information from a base station;
Determining whether to perform traffic offloading to the heterogeneous network based on the traffic offloading related information;
Transmitting a message for offloading traffic determined based on the traffic offloading related information to a packet data network gateway (P-GW) when performing traffic offloading; And
And performing traffic offloading to the heterogeneous network. The method of claim 1, wherein
The step of receiving the traffic offloading related information
Receiving a probability value for determining whether to perform traffic offloading,
The step of determining whether to perform the traffic offloading comprises:
And determining whether to perform traffic offloading to the heterogeneous network based on the received probability value. The method according to claim 1,
The step of receiving the traffic offloading related information
Receiving information indicative of a type of traffic to perform traffic offloading,
The step of transmitting a message offloading the traffic to the P-GW
And transmitting to the P-GW a message for offloading traffic determined based on a message indicating the received traffic type. The method of claim 3,
The information indicating the type of traffic for performing the traffic offloading is
Wherein the terminal includes at least one of an access point name (APN), IP flow information, and bearer information related to traffic to be offloaded by the terminal. The method according to claim 1,
The step of transmitting a message offloading the traffic to the P-GW
And transmitting, to the P-GW, a message including an indicator for instructing not to release the information of the terminal. A method of transmitting and receiving data in a base station of a mobile communication system,
Generating information related to traffic offloading; And
And transmitting information on traffic offloading to the terminal,
The UE determines whether to perform traffic offloading on the heterogeneous network based on the traffic offloading related information, and when the traffic offloading is performed, a message for offloading the traffic determined on the basis of the traffic offloading related information is transmitted to the terminal To a network gateway (Packet Data Network GateWay, P-GW), and performs traffic offloading to the heterogeneous network. The method according to claim 6,
The terminal
Receiving a probability value for determining whether to perform traffic offloading, and determining whether to perform traffic offloading to the heterogeneous network based on the received probability value. The method according to claim 6,
The terminal
Receiving a message indicating a type of traffic for performing traffic offloading, and transmitting a message for offloading traffic determined based on a message indicating the received traffic type to the P-GW. 9. The method of claim 8,
The information indicating the type of traffic for performing the traffic offloading is
Wherein the terminal includes at least one of an access point name (APN), IP flow information, and bearer information related to traffic to be offloaded by the terminal. The method according to claim 6,
The terminal
And transmits to the P-GW a message including an indicator for instructing not to release the information of the terminal. 1. A terminal for transmitting and receiving data in a mobile communication system,
A transmitting and receiving unit for transmitting and receiving signals to and from other communication entities; And
Receiving the traffic offloading related information from the base station, controlling whether to perform traffic offloading on the heterogeneous network based on the traffic offloading related information, and when performing traffic offloading, And a controller for transmitting a message for offloading the traffic determined based on the P-GW to a packet data network gateway (P-GW), and for performing traffic offloading to the heterogeneous network. 12. The method of claim 11,
The control unit
Receiving a probability value for determining whether to perform traffic offloading, and determining whether to perform traffic offloading to the heterogeneous network based on the received probability value. 12. The method of claim 11,
The control unit
And transmits a message for offloading the traffic determined based on the message indicating the type of the received traffic to the P-GW. 14. The method of claim 13,
The information indicating the type of traffic for performing the traffic offloading is
Wherein the terminal comprises at least one of an access point name (APN), IP flow information, and bearer information related to traffic to be offloaded by the terminal. 12. The method of claim 11,
Wherein the controller transmits a message including an indicator for instructing not to release the information of the terminal to the P-GW. A base station for transmitting and receiving data in a mobile communication system,
A control section for generating information related to traffic offloading; And
And a transmission / reception unit for transmitting traffic offloading related information to the terminal,
The UE determines whether to perform traffic offloading on the heterogeneous network based on the traffic offloading related information, and when the traffic offloading is performed, a message for offloading the traffic determined on the basis of the traffic offloading related information is transmitted to the terminal To a network gateway (Packet Data Network GateWay, P-GW), and performs traffic offloading to the heterogeneous network. 17. The method of claim 16,
The terminal
Receiving a probability value for determining whether to perform traffic offloading, and determining whether to perform traffic offloading to the heterogeneous network based on the received probability value. 17. The method of claim 16,
The terminal
And transmits a message to the P-GW, the P-GW receiving information indicating a traffic type to perform traffic offloading, and offloading traffic determined based on the received traffic type indicator. 19. The method of claim 18,
The information indicating the type of traffic for performing the traffic offloading is
Wherein the terminal comprises at least one of an access point name (APN), IP flow information, and bearer information related to traffic to be offloaded by the terminal. 17. The method of claim 16,
The terminal
And transmits to the P-GW a message including an indicator for instructing not to release the information of the terminal.

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