WO2013066103A1

WO2013066103A1 - Apparatus and method for congestion control for continuity of mbms service

Info

Publication number: WO2013066103A1
Application number: PCT/KR2012/009175
Authority: WO
Inventors: 정명철; 권기범; 안재현
Original assignee: 주식회사 팬택
Priority date: 2011-11-04
Filing date: 2012-11-02
Publication date: 2013-05-10

Abstract

The present invention relates to an apparatus and a method for congestion control for continuity of an MBMS service. The present specification discloses a method in which a base station controls network congestion for continuity of an MBMS service, said method comprising: a step of recognizing network congestion caused by excessive traffic entering a network; a step of transmitting a congestion notification indicator that indicates the perception of network congestion and includes information relating to MBMS to a terminal in a connection mode for receiving an MBMS service at a specific frequency; a step of receiving congestion response information from the terminal; and a step of transmitting congestion solution information for solving the network congestion to the terminal. According to the present invention, a terminal may continuously receive an MBMS service, and continuity of the MBMS service and quality of the service for the terminal may be ensured.

Description

Congestion control device and method for continuity of MBMS service

The present invention relates to wireless communications, and more particularly, to an apparatus and method for congestion control for continuity of MBMS services.

Cellular is a concept proposed to overcome the limitations of coverage area, frequency and subscriber capacity. This is a method of providing a call right by replacing a high power single base station with a plurality of low power base stations. In other words, by dividing the mobile communication service area into several small cells, adjacent cells are assigned different frequencies, and two cells that are sufficiently far apart from each other and do not cause interference can use the same frequency band to spatially reuse frequencies. To make it possible.

Handover or handoff is when the terminal moves away from the current communication service area (source cell) as the terminal moves to an adjacent communication service area (target cell). It is a function that automatically tunes to a new traffic channel of an adjacent communication service area and keeps a call state continuously. That is, a terminal communicating with a specific base station is linked to another neighboring base station (target base station) when the signal strength of the specific base station (hereinafter referred to as a source base station) is weakened. . If a handover is made, the problem of call disconnection occurring when moving to an adjacent cell can be solved.

MBMS (Multimedia Broadcast / Multicast Service) is a service that transmits data packets to multiple users at the same time similarly to the existing CBS (Cell Broadcast Service). However, while CBS is a low-speed message-based service, MBMS is intended for high-speed multimedia data transmission. In addition, CBS is not based on IP (internet protocol), but MBMS is based on IP multicast. When a certain level of users exists in the same cell, the necessary resources (or channels) are shared when they are transmitted to each user so that multiple users receive the same multimedia data to improve the efficiency of radio resources and to provide multimedia services from the user's point of view. It is an advantage of MBMS that it is available cheaply.

MBMS uses a shared channel to efficiently receive data from a plurality of terminals in one service. That is, not one dedicated channel is allocated to one service data, but only one shared channel, as many as the number of terminals to receive the service in one cell. A plurality of terminals simultaneously receive the shared channel, thereby improving the efficiency of radio resources.

However, when network congestion occurs, the base station should be able to solve network congestion for terminals related to the MBMS service. Alternatively, even when network congestion is detected in a communication situation where the MBMS service is not considered, the base station should be able to grasp information on the terminal interested in the MBMS service or receiving the MBMS service.

According to an aspect of the present invention, in the method of controlling network congestion of a base station for continuity of a multimedia broadcast multicast service (MBMS) service, recognizing a network congestion in which excessive traffic is introduced into a network; Indicating that network congestion is recognized and transmitting a congestion notification indicator including MBMS related information to a terminal in a connected mode that receives an MBMS service at a specific frequency, and receiving congestion response information from the terminal; And transmitting the congestion resolution information to solve the network congestion to the terminal.

According to another aspect of the present invention, there is provided a base station for controlling network congestion for continuity of MBMS service, comprising: a congestion control unit recognizing a network congestion in which excessive traffic flows into a network, and including MBMS-related information by an instruction of the congestion control unit; A message processing unit for generating a congestion notification indicator, transmitting the congestion notification indicator to a terminal in a connected mode that receives an MBMS service at a specific frequency, and sending congestion response information that is a response to the congestion notification indicator from the terminal; And an RF unit configured to transmit congestion resolution information to the terminal to solve the network congestion.

According to another aspect of the present invention, in the method of controlling network congestion of a terminal for continuity of MBMS services, receiving a MBMS service from a base station at a specific frequency, and network congestion in which excessive traffic flows into a network on the specific frequency. Receiving, from the base station, a congestion notification indicator including MBMS related information, transmitting congestion response information to the base station in response to the congestion notification indicator, and congestion to resolve the network congestion Receiving resolution information from the base station.

According to another aspect of the present invention, in a terminal for controlling network congestion for continuity of an MBMS service, network congestion occurs in which an MBMS service is received from a base station at a specific frequency and excessive traffic flows into a network on the specific frequency. Receiving a congestion notification indicator indicating from the base station, an RF unit for receiving congestion resolution information for solving the network congestion from the base station, extracting MBMS information from the congestion notification indicator, and based on the MBMS information And a message processing unit for generating congestion response information and transmitting the congestion response information to the RF unit, and a communication control unit for controlling the terminal to operate in the idle mode according to the instruction of the congestion resolution information.

According to another aspect of the present invention, there is provided a network congestion control method of a terminal for continuity of a multimedia broadcast multicast service (MBMS) service. The method includes transmitting a service priority indicator to a base station indicating that one of an MBMS service and a unicast service has priority, and connecting the unicast service based on the MBMS service having the priority. Receiving a radio resource control (RRC) connection release message from the base station indicating that the release.

The change of the priority may be indicated by the transmission of the service priority indicator, and the change of the priority may be indicated by the non-transmission of the service priority indicator.

The network congestion control method of a terminal for continuity of the multimedia broadcast multicast service (MBMS) service indicates that the base station recognizes a network congestion in which excessive traffic flows into a network, and the MBMS service. The method may further include receiving a congestion notification indicator from the base station, the congestion notification indicator including information related to the.

The information related to the MBMS service includes frequency information indicating a specific frequency provided by the MBMS service, alternative frequency information indicating another frequency providing the MBMS service, and a type of MBMS service provided through the specific frequency. It may include at least one of the MBMS type list indicating.

According to still another aspect of the present invention, there is provided a network congestion control method of a base station for continuity of MBMS service. The method may further include receiving a service priority indicator from a terminal informing that one of the MBMS service and the unicast service has priority, and disconnecting the unicast service based on the MBMS service having the priority. And transmitting to the terminal an RRC connection release message indicating.

Here, the base station may recognize that there is a change in the priority by the reception of the service priority indicator, and may recognize that there is no change in the priority by non-receipt of the service priority indicator.

The network congestion control method of the base station for the continuity of the MBMS service includes the steps of recognizing a network congestion in which excessive traffic flows into the network, and instructing the network congestion and including a information related to the MBMS service. The method may further include transmitting to the terminal.

The information related to the MBMS service may include frequency information indicating a specific frequency provided by the MBMS service, alternative frequency information indicating another frequency providing the MBMS service, and a type of MBMS service provided through the specific frequency. It may include at least one of the MBMS type list.

The network congestion can be solved by transmitting MBMS related information to the terminal in the situation of network congestion, the terminal can continuously receive the MBMS service, the continuity of the MBMS service for the terminal and the quality of service (Quality of Service (QoS) can be guaranteed. In addition, in a network congestion situation, the UE may inform the base station of the priority of the MBMS or unicast service to solve the network congestion, the UE may continuously receive the MBMS service, and the continuity and service of the MBMS service for the UE. The quality of can be guaranteed.

1 is a block diagram illustrating a wireless communication system.

FIG. 2 is a block diagram illustrating a radio protocol architecture for a user plane and a radio protocol architecture for a control plane.

3 shows a mapping between a downlink logical channel and a downlink transport channel.

4 shows a mapping between a downlink transport channel and a downlink physical channel.

5 is a diagram illustrating a core network structure for MBMS to which the present invention is applied.

6 is an example of a deployment scenario of a system providing a service in an MBMS according to the present invention.

7 is a flowchart illustrating a congestion control method performed by a base station according to an embodiment of the present invention.

8 is a flowchart illustrating a congestion control method performed by a terminal according to an embodiment of the present invention.

9 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to an embodiment of the present invention.

10 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention.

11 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention.

12 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention.

13 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention.

14 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention.

15 is a block diagram illustrating a terminal and a base station for performing congestion control according to the present invention.

16 is a flowchart illustrating a method of performing congestion control according to an embodiment of the present invention.

17 is a flowchart illustrating a method of performing congestion control according to another example of the present invention.

18 is a flowchart illustrating a method of performing congestion control according to another example of the present invention.

19 is a flowchart illustrating a method of performing congestion control according to another example of the present invention.

20 is a flowchart illustrating a method of performing congestion control according to another example of the present invention.

21 is a flowchart illustrating a method of performing congestion control according to another example of the present invention.

22 is a flowchart illustrating a congestion control method performed by a base station according to an embodiment of the present invention.

23 is a flowchart illustrating a congestion control method performed by a terminal according to an embodiment of the present invention.

24 is a block diagram illustrating a terminal and a base station for performing congestion control according to the present invention.

Hereinafter, some embodiments will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the embodiments of the present specification, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

In addition, the present specification describes a wireless communication network, the operation performed in the wireless communication network is performed in the process of controlling the network and transmitting data in the system (for example, the base station) that is in charge of the wireless communication network, or the corresponding wireless Work may be done at the terminal coupled to the network.

1 is a block diagram illustrating a wireless communication system. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be referred to as Long Term Evolution (LTE) or LTE-A (Advanced) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, the E-UTRAN includes at least one base station (BS) 20 that provides a control plane and a user plane to the terminal. The UE 10 may be fixed or mobile and may have other mobile stations, advanced MSs (AMS), user terminals (UTs), subscriber stations (SSs), wireless devices (Wireless Devices), and the like. It may be called a term.

The base station 20 generally refers to a station communicating with the terminal 10, and includes an evolved-NodeB (eNodeB), a Base Transceiver System (BTS), an Access Point, an femto-eNB, It may be called other terms such as a pico-eNB, a home eNB, and a relay. The base station 20 may provide at least one cell to the terminal. The cell may mean a geographic area where the base station 20 provides a communication service or may mean a specific frequency band. The cell may mean a downlink frequency resource and an uplink frequency resource. Alternatively, the cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource. In addition, in general, when carrier aggregation (CA) is not considered, one cell always has a pair of uplink and downlink frequency resources.

An interface for transmitting user traffic or control traffic may be used between the base stations 20. The source base station (Source BS) 21 refers to a base station in which a radio bearer is currently set up with the terminal 10, and the target base station (Target BS, 22) means that the terminal 10 disconnects the radio bearer from the source base station 21 and renews it. It means a base station to be handed over to establish a radio bearer.

The base stations 20 may be connected to each other through an X2 interface, which is used to exchange messages between the base stations 20. The base station 20 is connected to an evolved packet system (EPS), more specifically, a mobility management entity (MME) / serving gateway (S-GW) 30 through an S1 interface. The S1 interface supports a many-to-many-relation between base station 20 and MME / S-GW 30. The PDN-GW 40 is used to provide packet data services to the MME / S-GW 30. The PDN-GW 40 varies depending on the purpose or service of communication, and the PDN-GW 40 supporting a specific service can be found using APN information.

Inter-E-UTRAN handover is a basic handover mechanism used for handover between E-UTRAN access networks. It is composed of X2 based handover and S1 based handover. X2-based handover is used when the UE wants to handover from the source base station (source BS, 21) to the target base station (target BS, 22) using the X2 interface. At this time, the MME / S-GW 30 is not changed. Do not.

By S1 based handover, the first bearer set between the P-GW 40, the MME / S-GW 30, the source base station 21, and the terminal 10 is released, and the P-GW 40 is released. A new second bearer is established between the GW 40, the MME / S-GW 30, the target base station 22, and the terminal 10.

Hereinafter, downlink means communication from the base station 20 to the terminal 10, and uplink means communication from the terminal 10 to the base station 20. The downlink is also called a forward link, and the uplink is also called a reverse link. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20.

FIG. 2 is a block diagram illustrating a radio protocol architecture for a user plane and a radio protocol architecture for a control plane. The data plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

Referring to FIG. 2, a physical layer (PHY) layer provides an information transfer service to a higher layer using a physical channel. The physical layer is connected to the upper layer Medium Access Control (MAC) layer through a transport channel. Data is moved between the MAC layer and the physical layer through the transport channel. Transport channels are classified according to how and with what characteristics data is transmitted over the air interface. Data moves between the physical layers, that is, between the physical layers of the transmitter and the receiver. There are several physical control channels. The physical downlink control channel (PDCCH) informs the terminal of resource allocation of a paging channel (PCH) and downlink shared channel (DL-SCH) and hybrid automatic repeat request (HARQ) information related to the DL-SCH. The PDCCH may carry an uplink scheduling grant informing the UE of resource allocation of uplink transmission. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. PHICH (physical Hybrid ARQ Indicator Channel) carries a HARQ ACK / NAK signal in response to uplink transmission. Physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request, and CQI for downlink transmission. Physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH).

The functions of the MAC layer include mapping between logical channels and transport channels and multiplexing / demultiplexing into transport blocks provided as physical channels on transport channels of MAC service data units (SDUs) belonging to the logical channels. The MAC layer provides a service to a Radio Link Control (RLC) layer through a logical channel. The logical channel may be divided into a control channel for transmitting control region information and a traffic channel for delivering user region information.

Functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs. In order to guarantee the various Quality of Service (QoS) required by the radio bearer (RB), the RLC layer has a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (Acknowledged Mode). Three modes of operation (AM). AM RLC provides error correction through an automatic repeat request (ARQ).

Functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include delivery of user data, header compression, and ciphering. The functionality of the Packet Data Convergence Protocol (PDCP) layer in the user plane includes the transfer of control plane data and encryption / integrity protection.

The RRC layer is responsible for the control of logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers. RB means a logical path provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, PDCP layer) for data transmission between the terminal and the network. The establishment of the RB means a process of defining characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and operation method. RB can be further divided into SRB (Signaling RB), DRB (Data RB), and MRB (MBMS PTM RB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane. MRB is used as a path for transmitting MBMS data.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

Referring to FIG. 3, a paging control channel (PCCH) is mapped to a paging channel (PCH), and a broadcast control channel (BCCH) is mapped to a broadcast channel (BCH) or a downlink shared channel (DL-SCH). Common Control Channel (CCCH), Dedicated Control Channel (DCCH), Dedicated Traffic Channel (DTCH), Multicast Control Channel (MCCH) and Multicast Traffic Channel (MTCH) are mapped to DL-SCH. MCCH and MTCH are also mapped to MCH (Multicast Channel).

Each logical channel type is defined by what kind of information is transmitted. There are two types of logical channels: control channels and traffic channels.

The control channel is used for transmission of control plane information. BCCH is a downlink channel for broadcasting system control information. PCCH is a downlink channel that transmits paging information and is used when the network does not know the location of the terminal. CCCH is a channel for transmitting control information between the terminal and the network, and is used when the terminal does not have an RRC connection with the network. The MCCH is a point-to-multipoint downlink channel used to transmit MBMS control information and is used for terminals receiving MBMS. DCCH is a point-to-point one-way channel for transmitting dedicated control information between the terminal and the network, and is used by a terminal having an RRC connection.

The traffic channel is used for transmission of user plane information. DTCH is a point-to-point channel for transmitting user information and exists in both uplink and downlink. MTCH is a point-to-multipoint downlink channel for transmission of traffic data, and is used for a terminal receiving an MBMS.

Transport channels are classified according to how and with what characteristics data is transmitted over the air interface. The BCH has a predefined transmission format that is broadcast and fixed in the entire cell area. DL-SCH supports hybrid automatic repeat request (HARQ). Support for dynamic link adaptation by changing modulation, coding and transmission power, possibility of broadcast, possibility of beamforming, support for dynamic / semi-static resource allocation, and support for discontinuous reception (DRX) to save terminal power And MBMS transmission support. PCH is characterized by DRX support for terminal power saving and broadcast to the entire cell area. The MCH is characterized by broadcast to the entire cell and MBMS Single Frequency Network (MBSFN) support. MBSFN uses a common scrambling code and spreading code to simultaneously broadcast the same MBMS channel in a plurality of cells forming an MBMS cell group.

Referring to FIG. 4, a BCH is mapped to a physical broadcast channel (PBCH), an MCH is mapped to a physical multicast channel (PMCH), and a PCH and a DL-SCH are mapped to a PDSCH. PBCH carries the BCH transport block, PMCH carries the MCH, and PDSCH carries the DL-SCH and PCH.

MBMS uses two logical channels. MCCH as a control channel and MTCH as a traffic channel. User data such as actual voice or video is transmitted on the MTCH, and setting information for receiving the MTCH is transmitted on the MCCH. MTCH and MCCH are a point-to-many downlink channel for a plurality of terminals, and may be referred to as a shared channel. The MBMS does not allocate radio resources as many as the number of terminals receiving a service, but allocates only radio resources for a shared channel, and simultaneously receives a shared channel from a plurality of terminals, thereby improving efficiency of radio resources.

If the UE changes the cell due to a location movement while receiving the MBMS service, it may be in a state in which the MBMS service cannot be continuously received. Even in this state, if the UE continuously performs the decoding operation for receiving the MBMS service, it may cause battery consumption. There is a need for an apparatus and method for allowing a terminal using an MBMS service to continuously receive an MBMS service without wasting resources during handover.

A source cell refers to a cell in which a terminal is currently receiving a service. A base station providing a source cell is called a source base station. A neighbor cell refers to a cell that is geographically adjacent to a source cell or on a frequency band. An adjacent cell using the same carrier frequency with respect to the source cell is called an intra-frequency neighbor cell. In addition, adjacent cells using different carrier frequencies based on the source cell are called inter-frequency neighbor cells. That is, not only a cell using the same frequency as the source cell but also a cell using a different frequency, all of the cells adjacent to the source cell may be referred to as adjacent cells.

The UE handover from the source cell to the neighboring cell in frequency is called intra-frequency handover. On the other hand, the UE handover from the source cell to the inter-frequency neighbor cell is referred to as inter-frequency handover. An adjacent cell to which the UE moves in handover is called a target cell. The base station providing the target cell is called a target base station.

The source cell and the target cell may be provided by one base station or may be provided by different base stations. Hereinafter, for convenience of description, it is assumed that the source cell and the target cell are provided by different base stations, that is, the source base station and the target base station. Therefore, the source base station and the source cell, the target base station and the target cell can be used interchangeably with each other.

Referring to FIG. 5, a radio access network (EUTRAN) 500 includes a multi-cell coordination entity (hereinafter referred to as MCE) 510 and a base station eNB 520. The MCE 510 is a main entity controlling the MBMS, and plays a role of radio resource allocation or admission control in the MBSFN region. MCE 510 may be implemented within base station 520 or may be implemented independently of base station 520. The interface between the MCE 510 and the base station 520 is called an M2 interface. The M2 interface is an internal control plane interface of the wireless access network 500, and MBMS control information is transmitted. If the MCE 510 is implemented in the base station 520, the M2 interface may only exist logically.

An Evolved Packet Core (EPC) 550 includes an MME 560 and an MBMS Gateway (MBMS GW) 570. MME 560, NAS signaling, roaming (authentication), authentication (authentication), PDN gateway and S-GW selection, MME selection for handover by MME change, accessibility to the idle mode terminal, AS security Performs operations such as security control.

The MBMS gateway 570 is an entity that transmits MBMS service data and is located between the base station 520 and the BM-SC and performs MBMS packet transmission and broadcast to the base station 520. The MBMS gateway 570 uses PDCP and IP multicast to transmit user data to the base station 520, and performs session control signaling for the radio access network 500.

The interface between the MME 560 and the MCE 510 is a control plane interface between the radio access network 500 and the EPC 550, which is called an M3 interface, and transmits control information related to MBMS session control.

The interface between the base station 520 and the MBMS gateway 570 is an interface of a user plane, which is called an M1 interface, and transmits MBMS service data.

Referring to FIG. 6, the MBMS service may be managed based on cell or location. MBMS service area is a general term for the area where a particular MBMS service is provided. For example, if an area where a specific MBMS service A is performed is called an MBMS service area A, the network may be in a state of transmitting an MBMS service A in the MBMS service area A. In this case, the terminal may receive the MBMS service A according to the capability of the terminal. The MBMS service area may be defined in terms of applications and services as to whether or not a particular service is provided in a certain area.

Cell A, Cell B, Cell C, Cell D, and Cell E are included in MBSFN Region 1, and Cell F is included in MBSFN Region 2. Cell G is a cell serving a frequency band f2 other than a cell in the MBSFN region. The MBSFN region refers to a region in which a particular MBMS service is provided in a single frequency band. For example, in the case of MBSFN region 1, an MBSFN subframe is allocated to frequency f1 to support a specific MBMS service A. At this time, in the MBSFN region, the MBSFN subframe may be allocated to the same frequency f1 to support the MBMS service A. For example, MBMSN region 2 may support MBMS service A, but MBMS service A may be supported using f3 different from frequency resource f1 in MBSFN region 1. In the same MBSFN region, even when the UE moves, the UE may receive the MBMS service based on the same MBMS configuration.

MBMS location range can be used to receive MBMS service through MRB only within a specific region or location range within the same MBSFN region, whereas MBMS service can be serviced by MRB in all cells in the MBSFN region. It is the way of management. As a management method of the MBMS location range, a method of managing by a cell unit and a method of positioning a specific location or region may be considered.

Network congestion is a condition in which excessive traffic or data is introduced that the network cannot accept. In general, this may occur when a plurality of terminals are concentrated to use a specific cell or frequency band. This may occur when a specific service or the like is performed in a specific cell or frequency band. For example, when performing communication in an area in which RRC connection mode terminals are concentrated, such as a hot spot, or by rapidly increasing the number of MBMS terminals that want to receive MBMS services provided in the same frequency band, a specific frequency band The lack of resources can cause network congestion. Congestion control, on the other hand, is a certain level of congestion in a network congestion situation, by stopping further resource allocation in a network or releasing a call or bearer that is currently maintained. It is a control method that maintains / manages a load.

The base station performs congestion control based on Allocation and Retention Priority (ARP), whether MBMS service or unicast service. In other words, when congestion occurs in the network, a service having a high allocation and occupancy priority is maintained and a service having a low high allocation and occupancy priority is stopped. The network performs congestion control regardless of MBMS service.

The terminal may receive the service with priority between the MBMS service and the unicast service. The unicast service refers to a dedicated type of service in which a terminal and a base station form a connection and through which a service is performed. For example, voice communication may correspond to this.

Or, the terminal may tend to receive the MBMS service in preference to the unicast service at a specific time or in a specific situation. For example, in order to receive a specific program of a specific specific broadcast, the priority may be increased so as to preferentially receive an MBMS service for a predetermined time. In some circumstances, the priority of the unicast service may be set higher than that of the MBMS service. For example, even during reception of an MBMS service, there may be a unicast service preferred by the terminal, such as a service based on a connection request from a specific person. In this case, even though the terminal is receiving the MBMS service, higher priority should be given to the unicast service.

Since a severe congestion is placed on resources in a network congestion situation, the base station needs to selectively provide either the MBMS service or the unicast service to the terminal according to the priority. To this end, the base station should be able to properly provide the MBMS service and unicast service, and manage the bearer appropriately. For example, in order to perform a unicast service through a terminal having a high unicast state, the base station needs to handover to a cell or another frequency other than the current cell or frequency. In this case, the MBMS service may not proceed in another cell or frequency that moves, and a problem may occur in the MBMS service continuity.

When the network congestion is recognized, the base station should be able to solve the network congestion for the terminals related to the MBMS service. Alternatively, even when network congestion is detected in a communication situation where the MBMS service is not considered, the base station should be able to grasp information on the terminal interested in the MBMS service or receiving the MBMS service. Here, the information about the terminal interested in the MBMS service or receiving the MBMS service may be MBMS related information used in the MBMS counting procedure.

Hereinafter, after the base station detects network congestion, two embodiments are disclosed as a method of solving the network congestion.

The base station may notify the network congestion to the terminal receiving or to receive the MBMS service in the state of detecting the network congestion.

Referring to FIG. 7, a base station providing an MBMS service at a specific frequency recognizes network congestion (S700). There may be several ways for the base station to recognize network congestion. As an example, the base station may be aware of network congestion by using the MBMS counting procedure for collecting the number of connected mode terminals receiving the MBMS service. When determining whether the network is congested based on the number of terminals collected by the MBMS counting procedure, the base station may determine as follows. For example, if it is recognized that a terminal having a predetermined threshold number or more is receiving the MBMS service, since the number of terminals for the MBMS service is higher than expected, it may be considered that network congestion has occurred. Furthermore, the base station may also know the number of terminals operating in the connected mode for the reception of the unicast service while accessing the cell of the specific frequency for the reception of the MBMS service.

As another example, the base station may be aware of network congestion based on the MBMS priority information. The base station may obtain MBMS related information of the terminal by receiving MBMS priority information and the like from the terminal.

As another example, the base station may recognize network congestion based on information on a terminal that has performed a cell change to a specific cell to receive a specific MBMS service. Of course, even though the base station may know that network congestion occurs, there may be a limit in accurately knowing what kind of situation provides the cause of network congestion.

Upon recognition of network congestion, the base station transmits a congestion notifying indicator to the terminal (S705). The congestion notification indicator is information for notifying the terminal that the base station has recognized the network congestion. The congestion notification indicator includes congestion status information indicating network congestion status at the frequency at which the MBMS service is provided. The congestion state information may indicate the congestion state for each frequency provided by each of the plurality of MBMS services. Meanwhile, the congestion notification indicator may further include MBMS related information.

Here, the MBMS-related information may include frequency information indicating a frequency (hereinafter, referred to as MBMS frequency) at which the UE receives the MBMS service, and alternative information indicating another frequency providing the same service as the MBMS service provided through the MBMS frequency. alternative) at least one of frequency information, an MBMS type list indicating a type of MBMS service provided through the MBMS frequency, a session start timing information of each MBMS service, and geographical area information provided by each MBMS service; Include. The frequency information or the alternative frequency information may indicate any one index in the following table indicating an E-UTRA operating band supported by the terminal as an index.

Table 1

Referring to Table 1, network operating bands are identified by indices of 1 to 43. Network operating bands 1 to 32 are operating bands supported in frequency division duplex (FDD) mode, and network operating bands 33 to 43 are operating bands supported in time division duplex (TDD) mode. Each network operating band may be divided into an uplink operating band and a downlink operating band. The uplink operating band is limited to the lowest band (F _{UL_Low} ) and the highest band (F _{UL_High} ), and the downlink operating band is limited to the lowest band (F _{DL_Low} ) and the highest band (F _{DL_High} ).

On the other hand, the MBMS type list may list a temporary mobile group identity (TMGI) corresponding to each MBMS service. The congestion notification indicator may be transmitted through an RRC message dedicated to each terminal in the connected mode. For example, the RRC message includes an RRC connection reconfiguration message. Alternatively, the congestion notification indicator may be transmitted through system information commonly applied to a plurality of terminals. For example, the congestion notification indicator is transmitted on the BCCH or MCCH which is a logical channel.

When the congestion notification indicator is received, the UE may know that network congestion has occurred at a specific MBMS frequency provided with the MBMS service. The terminal selectively performs at least one of several operations intended to respond to network congestion. For example, when the terminal transmits the congestion response information, the base station receives the congestion response information from the terminal (S710).

As one example, the congestion response information is included in the RRC connection release request message for releasing the connected mode of the terminal.

As another example, the congestion response information is included in a measurement report used to determine handover.

Congestion response information may be transmitted in a specific message such as a measurement report, but is not limited thereto and may be included in a message for transmitting MBMS-related assistant information such as a degree of congestion response.

The base station transmits congestion resolution information to the terminal based on the congestion response information (S715). The congestion resolution information is information that the base station instructs the terminal to correspond to network congestion in a designated manner.

As one example, the congestion resolution information is included in the RRC connection release message for releasing the connection mode of the terminal.

As another example, the congestion resolution information is included in a handover command message instructing the base station to the terminal to perform handover to the target eNB.

The base station releases the RRC connection with the terminal, and releases the radio resources allocated to the terminal (S720). Here, the released radio resource includes a resource for unicast service dedicated to the terminal. By releasing radio resources, network congestion can be reduced. Even if the radio resource is released, the UE may continuously receive the MBMS service, thereby ensuring continuity of the MBMS service and quality of service (QoS).

Referring to FIG. 8, the terminal receiving the MBMS service at a specific frequency receives a congestion notification indicator from the base station (S800). The congestion notification indicator includes congestion status information indicating network congestion status at the frequency at which the MBMS service is provided. The congestion state information may indicate the congestion state for each frequency provided by each of the plurality of MBMS services. Meanwhile, the congestion notification indicator may further include MBMS related information.

The MBMS related information includes at least one of frequency information indicating an MBMS frequency, alternative frequency information, a list of MBMS types, session start timing information of each MBMS service, and geographic area information provided by each MBMS service. The frequency information or the alternative frequency information may indicate any one of the indexes in Table 1, which indicates the network operating bands supported by the terminal as an index.

The congestion notification indicator may be transmitted through an RRC message dedicated to each terminal in the connected mode. For example, the RRC message includes an RRC connection reconfiguration message. Alternatively, the congestion notification indicator may be transmitted through system information commonly applied to a plurality of terminals. For example, the congestion notification indicator is transmitted on the BCCH or MCCH which is a logical channel.

When the congestion notification indicator is received, the UE may know that network congestion has occurred at a specific MBMS frequency provided with the MBMS service. The terminal optionally performs at least one of several operations intended to respond to network congestion. For example, if the terminal determines that network congestion is not a big problem, it can take an unresponsive operation. Alternatively, if the terminal determines that network congestion should be avoided, the terminal generates congestion response information containing a specific message and transmits it to the base station (S805).

The terminal receives congestion resolution information from the base station (S810). The congestion resolution information is information that the base station instructs the terminal to correspond to network congestion in a designated manner. As one example, the congestion resolution information is included in the RRC connection release message for releasing the connection mode of the terminal. As another example, the congestion resolution information is included in a handover command message instructing the base station to the terminal to perform handover to the target eNB.

Upon receiving the congestion resolution information, the terminal releases the current unicast service and enters an idle mode (S815). Even in the idle mode, the UE may continuously receive the MBMS service. In this case, the terminal may move to another frequency (or cell) by cell reselection with reference to the alternative frequency information, and receive the MBMS service through the other frequency. Alternatively, the terminal may give up the MBMS service reception and handover to another cell. As a result, the continuity of the MBMS service and the quality of service (QoS) can be guaranteed.

9, the base station that recognizes network congestion transmits a congestion notification indicator including MBMS related information to the terminal (S900). In this case, the terminal is in the connected mode, and gives the MBMS service higher priority than other unicast services. Therefore, the terminal transmits congestion response information to the base station (S905). The base station transmits congestion resolution information to the terminal (S910).

10 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention. This is an example embodiment of FIG. 9.

Referring to FIG. 10, congestion control is performed using an RRC connection release procedure. For example, the base station that recognizes network congestion transmits a congestion notification indicator including MBMS related information to the terminal (S1000). In this case, the terminal is in the connected mode, and gives the MBMS service higher priority than other unicast services.

In this case, in order to continuously receive the MBMS service, the terminal may release the connection mode, that is, release the unicast service. Therefore, the terminal transmits an RRC connection release request message to the base station as a response to the congestion notification indicator (S1005). When receiving the RRC connection release request message of the terminal, the base station transmits an RRC connection release message indicating the release of the RRC connection to the terminal (S1010). As a result, the terminal switches from the connected mode to the idle mode. Thereafter, even if the priority of the MBMS service and the unicast service is changed, the RRC connection cannot be reestablished for the terminal until the network congestion decreases to a certain level (that is, before the end of the network congestion). Alternatively, until the network congestion ends, the network may reject a configuration request for an RRC connection reestablishment or an RRC connection establishment request of the terminal.

In this case, the terminal determines whether the MBMS service currently being received can be received at another frequency by using the alternative frequency information included in the MBMS related information, and if the same MBMS service can be provided through another frequency, the terminal can Handover may be performed at another frequency (or target base station). Preferably said other frequency should be free of network congestion. In this case, although the UE manages the MBMS service as a higher priority than the unicast service, it is to increase the flexibility and efficiency of using the frequency to support the MBMS service continuity according to the capability of the UE.

11 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention. This is another example embodied in FIG.

Referring to FIG. 11, congestion control is performed using a handover procedure. For example, the base station that recognizes network congestion transmits a congestion notification indicator including MBMS related information to the terminal (S1100). At this time, the terminal is in the connected mode. Unlike FIG. 10, in FIG. 11, the UE does not require the MBMS service to be given a higher priority than other unicast services. For UEs that are not interested in MBMS service or give higher priority to unicast service, handover to neighbor cell rather than staying at current MBMS frequency may be helpful in resolving network congestion. Because it can. Accordingly, when a terminal giving a high priority to unicast receives a congestion notification indicator, it may be determined that handover is possible to an adjacent cell.

The UE determines whether the MBMS service currently being received can be received at another frequency using the alternative frequency information included in the MBMS-related information, and if the UE can be provided with the same MBMS service through another frequency, the UE can receive the other frequency. (Or the target base station) may perform a handover. Preferably said other frequency should be free of network congestion.

To this end, the terminal performs measurement on the frequency of the MBMS service currently being received, and transmits the result of the measurement report to the base station (S1105).

The base station transmits a handover (HO) preparation request to the target base station through the X2 interface (S1106), and the target base station receiving the handover preparation request transmits a handover (HO) preparation response to the base station (S1107). .

When the handover preparation response is received from the target base station, the base station transmits a handover command message to the terminal (S1110).

Meanwhile, a terminal supporting carrier aggregation (CA) may be a component carrier (CC) in which an MBMS frequency in which the same MBMS service is performed may be aggregated. In this case, while receiving an MBMS service through the CC, it is possible to receive a unicast service through another CC. Alternatively, another frequency or another CC that provides the same MBMS service may be newly configured in the terminal in addition to the CC where the current network congestion occurs. In this case, whether the MBMS service is supported in the CC or the like, information on the MBMS service available for each CC supported by the MBMS may be transmitted from the primary serving cell (PCell) or the primary CC (PCC) or cell to the terminal. have. In this case, the MBMS-related CC information may be included in the CC configuration message. The CC configuration message may be an RRC reconfiguration message.

Referring to FIG. 12, the base station that recognizes network congestion transmits a congestion notification indicator including MBMS related information to the terminal (S1200). In this case, the terminal is in the connected mode, and gives the MBMS service higher priority than other unicast services. Thereafter, the base station transmits congestion resolution information to the terminal (S1205). Unlike the congestion control in FIG. 9, this excludes the transmission procedure of the congestion response information.

13 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention. This is an example embodiment of FIG.

Referring to FIG. 13, congestion control is performed using a modified RRC connection release procedure. For example, the base station that recognizes network congestion transmits a congestion notification indicator including MBMS related information to the terminal (S1300). In this case, the terminal is in the connected mode, and gives the MBMS service higher priority than other unicast services.

The base station transmits an RRC connection release message to the terminal instructing release of the RRC connection (S1305). As a result, the terminal switches from the connected mode to the idle mode. Thereafter, even if the priority of the MBMS service and the unicast service is changed, the RRC connection cannot be reestablished for the terminal until the network congestion decreases to a certain level (that is, before the end of the network congestion). Alternatively, until the network congestion ends, the network may reject a configuration request for an RRC connection reestablishment or an RRC connection establishment request of the terminal.

14 is a flowchart illustrating a congestion control method performed between a terminal and a base station according to another embodiment of the present invention. This is another embodiment embodied in FIG.

Referring to FIG. 14, congestion control is performed using a modified handover procedure. For example, the base station that recognizes network congestion transmits a congestion notification indicator including MBMS related information to the terminal (S1400). At this time, the terminal is in the connected mode. The base station transmits a handover command message to the terminal (S1405). As a result, the UE hands over to a cell provided by another base station or another base station. The cell provides the same MBMS service as the MBMS service received by the UE before handover.

Referring to FIG. 15, the terminal 1500 includes an RF unit 1505 and a terminal processor 1510. The terminal processor 1510 includes a message processor 1511 and a communication controller 1512. Here, the terminal 1500 may operate in one of a connected mode and a idle mode.

The RF unit 1505 receives an MBMS service provided at a specific frequency, a congestion notification indicator including MBMS related information, or congestion resolution information from the base station 1550. In addition, the RF unit 1505 transmits the congestion response information generated by the message processing unit 1511 to the base station 1550.

The message processor 1511 extracts MBMS related information from the congestion notification indicator. Here, the extracted MBMS-related information is frequency information indicating the MBMS frequency provided by the MBMS service being received by the terminal 1500, and an alternative frequency indicating another frequency providing the same service as the MBMS service provided through the MBMS frequency. At least one of the information, an MBMS type list indicating a list of MBMS services provided through the MBMS frequency, session start timing information of each MBMS service, and geographic area information provided by each MBMS service. The frequency information or the alternative frequency information may indicate any one of the indexes in Table 1, which indicates the network operating bands supported by the terminal as an index.

The message processor 1511 may generate congestion response information that is a response to the congestion notification indicator and transmit the congestion response information to the RF unit 1505 based on the MBMS-related information. As an example, the congestion response information is included in the RRC connection release request message. As another example, the congestion response information is included in the measurement report.

When the RF unit 1505 receives the congestion resolution information from the base station 1550 as a response to the congestion response information, the message processor 1511 transfers the content indicated by the congestion resolution information to the communication control unit 1512. Congestion resolution information is included in the RRC connection release message. In this case, the message processor 1511 instructs the communication controller 1512 to release the RRC connection according to the instruction of the RRC connection release message.

Or the congestion resolution information is included in the handover command message. In this case, the message processing unit 1511 instructs the communication control unit 1512 to handover according to the instruction of the handover command message.

The communication controller 1512 releases the RRC connection and switches the terminal 1500 from the connected mode to the idle mode according to the instruction of the message processor 1511. That is, the communication control unit 1512 no longer transmits or receives a unicast service related signal. Alternatively, the communication controller 1512 may measure the MBMS frequency, perform a handover to another base station, or perform cell reselection using MBMS-related information according to the instruction of the message processor 1511.

The base station 1550 includes an RF unit 1555 and a base station processor 1560. The base station processor 1560 includes a congestion control unit 1561 and a message processing unit 1562.

The RF unit 1555 transmits an MBMS service at a specific frequency, and transmits a congestion notification indicator including MBMS related information generated by the message processor 1561 and congestion resolution information to the terminal 1500. For example, the RF unit 1555 may transmit the congestion resolution information through one of an RRC connection release message and a handover command message.

In addition, the RF unit 1555 receives congestion response information from the terminal 1500. For example, the RF unit 1555 transmits a radio resource control (RRC) connection release request message, a measurement report message, and MBMS-related assistant information requesting release of the connection mode. The congestion response information may be received through one of the messages.

The congestion control unit 1561 recognizes network congestion. There may be various ways for the congestion control unit 1561 to recognize network congestion. As an example, the congestion control unit 1561 may use an MBMS counting procedure that collects the number of connected mode terminals receiving the MBMS service. When determining whether the network is congested based on the number of terminals collected by the MBMS counting procedure, the congestion control unit 1561 may determine as follows. For example, if it is recognized that a terminal having a predetermined threshold number or more is receiving the MBMS service, it is determined that network congestion has occurred since the number of terminals for the MBMS service is higher than expected.

As another example, the congestion control unit 1561 may recognize the network congestion based on the MBMS priority information. The congestion control unit 1561 may obtain MBMS-related information of the terminal 1500 by receiving MBMS priority information and the like from the terminal 1500.

As another example, the congestion control unit 1561 may recognize network congestion based on information on a terminal that has performed a cell change to a specific cell to receive a specific MBMS service.

When the congestion control unit 1561 is aware of network congestion, the message processing unit 1562 instructs to generate a congestion notification indicator. In addition, the congestion control unit 1561 instructs the message processing unit 1562 to generate congestion resolution information when the congestion response information is received from the terminal 1500.

The message processing unit 1562 generates a congestion notification indicator or congestion resolution information according to the instruction of the congestion control unit 1561. The congestion control unit 1561 releases the radio resource allocated to the terminal 1500. In addition, the message processor 1562 includes at least one of frequency information indicating a specific frequency, alternative frequency information indicating another frequency for providing an MBMS service, and an MBMS type list indicating an MBMS service type provided through the specific frequency. MBMS related information can be generated.

In addition, the message processing unit 1562 includes congestion state information indicating a network congestion state at a frequency where an MBMS service is provided, includes congestion state information for each frequency provided by each MBMS service, or further includes MBMS related information. Congestion notification indicators can be generated.

Second Embodiment

As another embodiment of solving the network congestion, the terminal may inform the terminal of the priority between the MBMS service and the unicast service in advance so that the base station can cope with the network congestion, thereby controlling the network congestion. To this end, the base station should receive information on service priority from the terminal.

Referring to FIG. 16, the terminal transmits a service priority indicator to the base station (S1600). The service priority means the priority between the MBMS service and the unicast service for the terminal, and the service priority indicator is information indicating service priority. For example, service priority may be defined as shown in the following table.

TABLE 2

Service priority indicator	Service priority
0	MBMS Service
One	Unicast Service

Referring to Table 2, if the service priority indicator is 1 bit, 0 means that the service priority is in the MBMS service, and 1 means that the service priority is in the unicast service. Of course, the indication of the service priority indicator may be reversed. The service priority indicator may also indicate priority for 2 ⁿ services as n bits.

On the other hand, service priority may be granted to the MBMS service as a default, or may be assigned to the unicast service. This is called the default priority. In this case, the service priority indicator may mean a modification of the previous service priority as shown in the following table.

TABLE 3

Service priority indicator	Service priority
No transfer	Maintain transfer service priority
send	Change Priority Service Priority

Referring to Table 3, when the service priority indicator is not transmitted or there is no signaling, it means that the previous service priority is maintained. If the service priority indicator is transmitted, it means that the previous service priority is changed. The terminal may transmit a service priority indicator to the base station whenever a change in service priority occurs. In other words, the service priority indicator may be used as an indicator indicating a change of priority as an indicator that the priority has been changed.

For example, if the service priority is not changed while the MBMS service has a default priority, the terminal does not transmit the service priority indicator to the base station. From the base station's point of view, if no service priority indicator is received, the base station still determines that the MBMS service has priority. If the service priority is changed, the terminal transmits a service priority indicator to the base station. From the point of view of the base station, upon receipt of the service priority indicator, the base station may know that the service priority has changed from MBMS service to unicast service.

Alternatively, if the service priority is not changed while the unicast service has a default priority, the terminal does not transmit the service priority indicator to the base station. From the base station's point of view, if no service priority indicator is received, the base station still determines that the unicast service has priority. If the service priority is changed, the terminal transmits a service priority indicator to the base station. From the point of view of the base station, upon receiving the service priority indicator, the base station may know that the service priority has changed from unicast service to MBMS service.

As such, the terminal may inform the base station of the change or maintenance of the service priority by transmitting or not transmitting the service priority indicator. The base station may perform network congestion control according to the service priority indicator.

On the other hand, the service priority indicator may indicate the priority (which is called a higher level priority) between different types of services such as MBMS service and unicast service, and additionally, priority between services of the same kind (low level priority). May be used). As an example, the lower level priority includes the priority between unicast services. For example, low-level priorities between application services such as file transfer protocol (FTP), messaging, and games may be indicated by the service priority indicator. As another example, lower level priorities include priorities between particular users or between particular servers. In this case, the user may be designated by an identifier, and the server may be designated by a server name. Alternatively, an email address, a telephone number, or the like may be used.

Referring to FIG. 17, the terminal transmits a service priority indicator to the base station (S1700). The terminal receives the MBMS service and the unicast service. The service priority indicator may explicitly indicate that a particular service has priority as shown in Table 1. Alternatively, the service priority indicator may instruct maintenance or change of service priority as shown in Table 2. In this case, the default priority is assumed to be in MBMS service. Service priorities include high level priorities (priorities between MBMS services and unicast services) and / or low level priorities (priorities between various application services included in unicast services), as described above. The service priority indicator may be transmitted to the base station not only by the base station but also by the terminal itself. For example, when a user has changed a symbol or priority for a specific service, the terminal may transmit a change fact to the base station. Alternatively, the terminal may transmit the service priority indicator to the base station at regular intervals.

If the network congestion is recognized, the base station transmits an RRC connection release message to the terminal to release the unicast service (S1705). The RRC connection release message may include MBMS frequency (MBMSfreq) information, which is a frequency at which the MBMS service is provided. MBMS frequency information indicates that the RRC connection is explicitly released because the priority is set in the MBMS service. The RRC connection release message may further include alternative frequency information indicating another frequency providing the same service as the MBMS service provided through the MBMS frequency.

Referring to FIG. 18, the terminal transmits a service priority indicator to the base station (S1800). The terminal receives the MBMS service and the unicast service. The service priority indicator may explicitly indicate that a particular service has priority as shown in Table 2. Alternatively, the service priority indicator may instruct maintenance or change of service priority as shown in Table 3. In this case, the default priority is assumed to be in MBMS service. Service priorities include high level priorities (priorities between MBMS services and unicast services) and / or low level priorities (priorities between various application services included in unicast services), as described above. The service priority indicator may be transmitted to the base station not only by the base station but also by the terminal itself.

One scenario is that the UE does not know that the same MBMS service is provided through an alternative frequency, and performs the cell change to the current MBMS frequency to receive the MBMS service. This can be one cause of network congestion. If the UE knows the alternative frequency information, the cell can be changed to the alternative frequency, thereby congesting the network.

The base station transmits a system information block (SIB) to the terminal to inform the MBMS that the MBMS service is performed even at the alternative frequency (S1805). The system information block includes alternate frequency information and network congestion state information at the alternate frequency. The system information block may be transmitted through a broadcast channel or an MBMS control channel (MCCH). Upon receiving the system information block, the terminal may move to an alternative frequency and seamlessly receive the same MBMS service.

Referring to FIG. 19, the terminal transmits an RRC connection request message including a service priority indicator to the base station (S1900). The RRC connection request message is a message used for the UE in idle mode to switch to the connected mode. The service priority indicator may be piggybacked on the RRC connection request message used in the RRC connection procedure and transmitted.

The base station can know how the terminal sets the priority of the MBMS service and the unicast service by checking the service priority indicator piggybacked in the RRC connection request message. The base station may determine whether to accept the RRC connection request of the terminal based on the service priority indicator. For example, in a situation in which network congestion is not eliminated, when the RRC connection request message is received from the UE which gives priority to the MBMS service, the base station may reject the RRC connection request. This is because the network congestion will increase when the terminal is switched to the connected mode. On the other hand, if the RRC connection request message is received from the UE that gives priority to the unicast service, the base station may accept the RRC connection request.

Upon determining rejection or acceptance of the RRC connection request, the base station transmits an RRC connection response message indicating the determination to the terminal (S1905). Upon determining acceptance of the RRC connection request, the RRC connection response message is an RRC connection establishment message.

Referring to FIG. 20, upon recognition of network congestion, the base station transmits a congestion notifying indicator to the terminal (S2000). The congestion notification indicator is information for notifying the terminal that the base station has recognized the network congestion. The congestion notification indicator includes congestion status information indicating network congestion status at the frequency at which the MBMS service is provided. The congestion state information may indicate the congestion state for each frequency provided by each of the plurality of MBMS services. Meanwhile, the congestion notification indicator may further include MBMS related information.

Here, the MBMS-related information is frequency information indicating a frequency (hereinafter, referred to as MBMS frequency) at which the UE receives the MBMS service, and an alternative frequency indicating another frequency providing the same service as the MBMS service provided through the MBMS frequency. And at least one of an MBMS type list indicating a type of MBMS service provided through the MBMS frequency, session initiation timing information of each MBMS service, and geographical area information provided by each MBMS service. The frequency information or the alternate frequency information may indicate any one of the indexes in Table 1 indicating an E-UTRA operating band that can be supported by the terminal as an index.

On the other hand, the MBMS type list may list a temporary mobile group identity (TMGI) corresponding to each MBMS service.

In response to the congestion notification indicator, the terminal transmits the service priority indicator to the base station (S2005). When the terminal receives the congestion notification indicator from the base station, not when the service priority is changed as in the embodiment according to Table 3, the terminal transmits the service priority indicator to the base station as in the embodiment according to Table 1 above.

The base station may perform network congestion control based on the service priority indicator.

Referring to FIG. 21, when network congestion is recognized, the base station transmits a congestion notification indicator to the terminal (S2100). In response to the congestion notification indicator, the terminal transmits a service priority indicator to the base station (S2105). When the terminal receives the congestion notification indicator from the base station, not when the service priority is changed as in the embodiment according to Table 3, the terminal transmits the service priority indicator to the base station as in the embodiment according to Table 2.

At this time, the base station transmits an RRC connection release message to the terminal (S2110). The RRC connection release message may include MBMS frequency (MBMSfreq) information, which is a frequency at which the MBMS service is provided. MBMS frequency information indicates that the RRC connection is explicitly released because the priority is set in the MBMS service. The RRC connection release message may further include alternative frequency information indicating another frequency providing the same service as the MBMS service provided through the MBMS frequency. The RRC connection release message may further include information indicating that the MBMS service releases the RRC connection because it has priority.

Referring to FIG. 22, a base station providing an MBMS service at a specific frequency recognizes network congestion (S2200). There may be several ways for the base station to recognize network congestion. As an example, the base station may be aware of network congestion by using the MBMS counting procedure for collecting the number of connected mode terminals receiving the MBMS service. When determining whether the network is congested based on the number of terminals collected by the MBMS counting procedure, the base station may determine as follows. For example, if it is recognized that a terminal having a predetermined threshold number or more is receiving the MBMS service, since the number of terminals for the MBMS service is higher than expected, it may be considered that network congestion has occurred. Furthermore, the base station may also know the number of terminals operating in the connected mode for the reception of the unicast service while accessing the cell of the specific frequency for the reception of the MBMS service.

Upon recognition of network congestion, the base station transmits a congestion notification indicator to the terminal (S2205).

As a response to the congestion notification indicator, the base station receives a service priority indicator from the terminal (S2210). From the service priority indicator, the base station determines which of the MBMS service and the unicast service the terminal has priority, and determines a priority service (S2215). Priority service means a service that is given priority. For example, when receiving the service priority indicator according to the embodiment of Table 2, the base station determines one of the MBMS service and the unicast service as the priority service according to the indication of the service priority indicator. Alternatively, when receiving the service priority indicator according to the embodiment of Table 3, the base station may know that the priority service has been changed. Accordingly, the base station determines the priority service as a unicast service if the previous service priority was an MBMS service, and determines the priority service as an MBMS service if the previous service priority was a unicast service.

The base station transmits congestion resolution information to the terminal (S2220). The congestion resolution information is information that the base station instructs the terminal to correspond to network congestion in a designated manner.

As another example, the congestion resolution information is included in a system information block that includes system information parameters.

Based on the congestion resolution information, the terminal may determine what action it should take.

Referring to FIG. 23, a terminal receiving an MBMS service at a specific frequency receives a congestion notification indicator from a base station (S2300). The congestion notification indicator includes congestion status information indicating network congestion status at the frequency at which the MBMS service is provided. The congestion state information may indicate the congestion state for each frequency provided by each of the plurality of MBMS services. Meanwhile, the congestion notification indicator may further include MBMS related information.

As a response to the congestion notification indicator, the terminal transmits a service priority indicator to the base station (S2305).

The terminal receives congestion resolution information from the base station (S2310). Congestion resolution information may be included in the system information block, or may be included in the RRC connection release message.

The terminal establishes an RRC connection or releases an RRC connection to solve network congestion based on the congestion resolution information (S2315).

For example, when the MBMS service is a priority service, congestion resolution information may be included in the RRC connection release message. In this case, the terminal releases the RRC connection and enters the idle mode. On the other hand, when the unicast service is a priority service, congestion resolution information may be included in the RRC connection establishment message. In this case, the terminal may be switched from the idle mode to the connected mode.

In this case, the terminal may move to another frequency (or cell) by cell reselection with reference to the alternative frequency information included in the congestion notification indicator, and may receive MBMS service through the other frequency. Alternatively, the terminal may give up receiving the MBMS service and hand over to another cell. As a result, the continuity of the MBMS service and the quality of service (QoS) can be guaranteed.

Referring to FIG. 24, the terminal 2400 includes an RF unit 2405 and a terminal processor 2410. The terminal processor 2410 includes a message processor 2411 and a communication controller 2412. Here, the terminal 2400 may operate in one of a connected mode and a idle mode.

The RF unit 2405 receives an MBMS service provided at a specific frequency, a congestion notification indicator including MBMS related information, or congestion resolution information from the base station 2450. The RF unit 2405 also transmits the service priority indicator generated by the message processing unit 2411 to the base station 2450.

The message processor 2411 extracts MBMS related information from the congestion notification indicator. Here, the extracted MBMS-related information is frequency information indicating the MBMS frequency provided by the MBMS service being received by the terminal 2400, and an alternative frequency indicating another frequency providing the same service as the MBMS service provided through the MBMS frequency. At least one of the information, an MBMS type list indicating a list of MBMS services provided through the MBMS frequency, session start timing information of each MBMS service, and geographic area information provided by each MBMS service. The frequency information or the alternative frequency information may indicate any one of the indexes in Table 3, which indicates the network operating bands supported by the terminal as an index.

The message processing unit 2411 may generate a service priority indicator based on the priority between the MBMS service and the unicast service and transmit the service priority indicator to the RF unit 2405. As an example, the service priority indicator may be included in the RRC connection request message. The service priority indicator may explicitly indicate that a specific service has priority as shown in Table 1 above. Alternatively, the service priority indicator may instruct maintenance or change of the service priority as shown in Table 2 above. In this case, the default priority is assumed to be in MBMS service. Service priorities include high level priorities (priorities between MBMS services and unicast services) and / or low level priorities (priorities between various application services included in unicast services), as described above.

When the RF unit 2405 receives the congestion resolution information from the base station 2450, the message processing unit 2411 transfers the content indicated by the congestion resolution information to the communication control unit 2412. Congestion resolution information is included in the RRC connection release message. In this case, the message processing unit 2411 instructs the communication control unit 2412 to release the RRC connection according to the instruction of the RRC connection release message.

Or the congestion resolution information is included in the system information block. In this case, the message processor 2411 instructs the communication controller 2412 to maintain or switch the state of the terminal 2400 to the idle mode or the connected mode according to the instruction of the system information block.

The communication controller 2412 releases the RRC connection and switches the terminal 2400 from the connected mode to the idle mode according to the instruction of the message processor 2411. That is, the communication control unit 2412 no longer transmits or receives a unicast service related signal. Alternatively, the communication control unit 2412 controls to receive the unicast service in the connected mode according to the instruction of the message processing unit 2411.

The base station 2450 includes an RF unit 2455 and a base station processor 2460. The base station processor 2460 includes a congestion control unit 2641 and a message processing unit 2246.

The RF unit 2455 transmits an MBMS service at a specific frequency, and transmits a congestion notification indicator including MBMS related information generated by the message processor 2241 and congestion resolution information to the terminal 2400. In addition, the RF unit 2455 receives a service priority indicator from the terminal 2400.

The congestion control unit 2241 recognizes network congestion. There may be various ways for the congestion control unit 2641 to recognize network congestion. As an example, the congestion control unit 2461 may use an MBMS counting procedure that collects the number of connected mode terminals receiving the MBMS service. When determining whether the network is congested based on the number of terminals collected by the MBMS counting procedure, the congestion control unit 2241 may determine as follows. For example, if it is recognized that a terminal having a predetermined threshold number or more is receiving the MBMS service, it is determined that network congestion has occurred since the number of terminals for the MBMS service is higher than expected.

As another example, the congestion control unit 2241 may recognize the network congestion based on the MBMS priority information. The congestion control unit 2241 may obtain MBMS related information of the terminal 2400 by receiving MBMS priority information and the like from the terminal 2400.

As another example, the congestion control unit 2461 may recognize network congestion based on information on a terminal that has performed a cell change to a specific cell to receive a specific MBMS service.

When the congestion control unit 2641 recognizes network congestion, the message processing unit 2246 instructs to generate a congestion notification indicator. In addition, when the service priority indicator is received from the terminal 2400, the congestion control unit 2241 determines a priority service based on the priority of a plurality of services set in the terminal 2400. For example, when the RF unit 2455 receives the service priority indicator according to the embodiment of Table 2, the congestion control unit 2241 may prioritize any one of the MBMS service and the unicast service according to the indication of the service priority indicator. Decide on service. Alternatively, when the RF unit 2455 receives the service priority indicator according to the embodiment of Table 3, the congestion control unit 2241 may know that the priority service has been changed. Therefore, the congestion control unit 2241 determines the priority service as a unicast service if the previous service priority was an MBMS service, and determines the priority service as an MBMS service if the previous service priority was a unicast service.

The congestion control unit 2651 instructs the message processing unit 2542 to generate congestion resolution information based on the determined priority service.

The message processing unit 2542 generates a congestion notification indicator or congestion resolution information according to the instruction of the congestion control unit 2241. The congestion control unit 2241 releases the radio resource allocated to the terminal 2400, or establishes an RRC connection.

As described above, the described methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the described steps or blocks, and those skilled in the art. It will be appreciated that other combinations are possible. Accordingly, it is intended that the present invention cover all other replacements, modifications and variations that fall within the scope of the following claims.

Claims

In the method of controlling network congestion of a base station for continuity of a multimedia broadcast multicast service (MBMS) service,

Recognizing network congestion;

Transmitting a congestion notification indicator and MBMS related information indicating the network congestion to a terminal in a connected mode that receives an MBMS service at a specific frequency;

Receiving congestion response information from the terminal; And

And transmitting congestion resolution information to solve the network congestion to the terminal.
The method of claim 1, wherein the MBMS related information,

And at least one of frequency information indicating the specific frequency, alternative frequency information indicating another frequency for providing the MBMS service, and an MBMS type list indicating the type of MBMS service provided through the specific frequency. Network congestion control method.
The method of claim 2, wherein the congestion notification indicator is

Information indicating that the base station has recognized the network congestion,

The congestion notification indicator includes congestion state information indicating a network congestion state at a frequency where an MBMS service is provided, includes congestion state information for each frequency provided by each MBMS service, or further includes the MBMS related information. A network congestion control method.
The method of claim 1,

The congestion response information is one of a radio resource control (RRC) connection release request message requesting the release of the connection mode, a measurement report message, and a message for transmitting MBMS-related assistant information. Network congestion control method, characterized in that received through.
The method of claim 1, wherein the congestion resolution information is

A method of controlling network congestion, characterized by being transmitted through one of an RRC connection release message and a handover command message.
A base station for controlling network congestion for continuity of MBMS services,

A congestion control unit for recognizing network congestion;

A message processing unit for generating a congestion notification indicator and MBMS information indicating the network congestion;

Transmits the congestion notification indicator and the MBMS related information to a terminal in a connected mode that receives an MBMS service at a specific frequency, receives congestion response information from the terminal, and receives congestion resolution information that resolves the network congestion; A base station comprising an RF unit for transmitting to the terminal.
The method of claim 6, wherein the message processing unit,

The MBMS related information including at least one of frequency information indicating the specific frequency, alternative frequency information indicating another frequency for providing the MBMS service, and an MBMS type list indicating the type of MBMS service provided through the specific frequency; Generating a base station.
The method of claim 6,

The congestion notification indicator is information for notifying that the base station has recognized network congestion,

The message processing unit includes congestion state information indicating a network congestion state at a frequency where an MBMS service is provided, includes congestion state information for each frequency provided by each MBMS service, or further includes the MBMS related information. And generate an indicator.
The method of claim 6, wherein the RF unit,

The congestion response through one of a radio resource control (RRC) connection release request message requesting release of the connection mode, a measurement report message, and a message transmitting MBMS-related assistant information And receiving information.
The method of claim 6, wherein the RF unit,

And transmit the congestion resolution information through one of an RRC connection release message and a handover command message.
In the network congestion control method of a terminal for continuity of MBMS service,

Receiving an MBMS service from a base station at a specific frequency;

Receiving, from the base station, a congestion notification indicator and MBMS related information indicating that network congestion occurs on the specific frequency;

Transmitting congestion response information to the base station;

Receiving congestion resolution information from the base station to resolve the network congestion; And

And performing cell reselection using the MBMS related information.
The method of claim 11, wherein the MBMS related information,

And at least one of frequency information indicating the specific frequency, alternative frequency information indicating another frequency for providing the MBMS service, and an MBMS type list indicating the type of MBMS service provided through the specific frequency. Network congestion control method.
The method of claim 11, wherein the congestion notification indicator is

Information indicating that network congestion has been recognized by the base station,

The congestion notification indicator includes congestion state information indicating a network congestion state at a frequency where an MBMS service is provided, includes congestion state information for each frequency provided by each MBMS service, or further includes the MBMS related information. A network congestion control method.
The method of claim 11,

The congestion response information is one of a radio resource control (RRC) connection release request message requesting the release of the connection mode, a measurement report message, and an MBMS-related assistant information message. Network congestion control method, characterized in that transmitted through.
The method of claim 11,

The congestion resolution information is received via one of an RRC connection release message, a handover command message, network congestion control method.
In the terminal for controlling network congestion for continuity of MBMS service,

Receives an MBMS service from a base station at a specific frequency, receives a congestion notification indicator and MBMS related information indicating that network congestion occurs on the specific frequency from the base station, transmits congestion response information to the base station, and transmits the network congestion. RF unit for receiving congestion resolution information from the base station to solve the;

A message processing unit which generates the congestion response information based on the MBMS related information and transmits the congestion response information to the RF unit; And

And a communication control unit configured to control the terminal to operate in the idle mode according to the congestion resolution information and perform cell reselection using the MBMS-related information.
The method of claim 16, wherein the message processing unit,

The MBMS related information including at least one of frequency information indicating the specific frequency, alternative frequency information indicating another frequency for providing the MBMS service, and an MBMS type list indicating the type of MBMS service provided through the specific frequency; Terminal, characterized in that the extraction.
The method of claim 16,

The congestion notification indicator is information for notifying that network congestion has been recognized by the base station,

The congestion notification indicator includes congestion state information indicating a network congestion state at a frequency where an MBMS service is provided, includes congestion state information for each frequency provided by each MBMS service, or further includes the MBMS related information. Terminal.
The method of claim 16, wherein the RF unit,

The congestion response through one of a radio resource control (RRC) connection release request message requesting the release of the connection mode, a measurement report message, and a message transmitting MBMS-related assistant information Terminal, characterized in that for transmitting information.
The method of claim 16, wherein the RF unit,

And receiving the congestion resolution information through one of an RRC connection release message and a handover command message.