METHOD FOR REPORTING MBMS INFORMATION IN WIRELESS COMMUNICATION SYSTEM AND DEVICE FOR SUPPORTING SAME

Abstract

Provided is a method for reporting multimedia broadcast and multicast service (MBMS) information by a terminal in a wireless communication system. The method comprises: determining whether or not to perform the logging of MBMS information; logging the MBMS information if the logging is determined to be performed; and reporting the logged MBMS information to a network. Whether or not to perform the logging of the MBMS information is determined on the basis of conditions for performing the logging of the MBMS information. The conditions for performing the logging of the MBMS information comprise the failure of receiving MBMS provided from the network and/or deterioration in the quality of receiving the MBMS.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communication and, more particularly, to a method for reporting Multimedia Broadcast and Multicast Service (MBMS) information in a wireless communication system and a device supporting the same.

2. Related Art

3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.

As technologies for supporting wireless communication are advanced, the type of service that may be provided from a network to users is diversified. A Multimedia Broadcast and Multicast Service (MBMS) is one of those services, and provides a terminal with information that may be provided in TV, movie, and digital forms in a broadcast and/or multicast manner. The MBMS has a great advantage in excellent efficiency compared to the case where a network is newly constructed in order to provide a service in that it can provide a service through the infrastructure of an already constructed network.

In order to optimize network performance, a network obtains a measured result from a terminal. In this case, the network may also obtain location information related to the measured result from the terminal and optimize network performance more efficiently. In order to optimize networks, service providers may obtain a measured result and location information using a terminal, which is called a Minimization of Driving Test (MDT).

In order to optimize network performance in relation to the MBMS, a network may support an MBMS MDT. The MBMS MDT may include a series of procedures, such as a configuration, acquisition, and reporting for MBMS information reporting. To this end, the network may select a terminal for the MBMS information reporting based on the capabilities of a terminal and/or the consent of a terminal user. However, an MBMS service is provided on an MBMS Single Frequency Network (MBSFN) area through broadcast or multicast, and a terminal that receives the MBMS service does not provide corresponding feedback. Accordingly, a network rarely obtains information about the MBMS reception status of the terminal. Accordingly, there is a need for a method that enables a network to receive a report on MBMS information from a terminal.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for reporting Multimedia Broadcast and Multicast Service (MBMS) information in a wireless communication system and a device supporting the same.

In one aspect, provided is a method of reporting, by user equipment, Multimedia Broadcast and Multicast Service (MBMS) information in a wireless communication system. The method includes determining whether or not to execute a logging of the MBMS information, logging the MBMS information if the logging is determined to be performed and reporting the logged MBMS information to a network. Whether or not to execute the logging of the MBMS information is determined based on an MBMS information logging execution condition. The MBMS information logging execution condition comprises at least one of a reception failure of an MBMS service and reception quality of the MBMS service provided by the network.

Determining whether or not to execute the logging of the MBMS information may comprise determining to execute the logging if the MBMS information logging execution condition is satisfied.

The method may further comprise determining whether or not to stop the execution of the logging of the MBMS information.

Determining whether or not to stop the execution of the logging of the MBMS information may comprise determining to stop the execution of the logging if the MBMS information logging execution condition that has been satisfied is released.

Logging the MBMS information may comprise logging a first MBMS log entry if the MBMS information logging execution condition is satisfied and logging a second MBMS log entry if the MBMS information logging execution condition is not satisfied. The logged MBMS information may comprise the first MBMS log entry and the second MBMS log entry.

The first MBMS log entry may comprise information indicating that the first MBMS log entry has been logged because the MBMS information logging execution condition has been satisfied.

The second MBMS log entry may comprise information indicating that the second MBMS log entry has been logged because the satisfaction of the MBMS information logging execution condition has been released.

Logging the MBMS information may comprise periodically logging third MBMS log entries until the satisfaction of the MBMS information logging execution condition is released after the MBMS information logging execution condition is satisfied. The logged MBMS information may further comprise the third MBMS log entries.

Each of the third MBMS log entries may comprise information indicating that a corresponding third MBMS log entry has been periodically logged.

The method may further comprise receiving an MBMS reporting configuration comprising configuration information for the logging and reporting of the MBMS information by the user equipment from the network. The MBMS reporting configuration may comprise MBMS logging execution information which specifies the MBMS information logging execution condition.

Reporting the logged MBMS information to the network may comprise sending a logged MBMS information availability indicator indicating that the logged MBMS information to be reported to the network is present to the network, receiving a logged MBMS information reporting request which requests the reporting of the logged MBMS information from the network and sending a logged MBMS information report comprising the logged MBMS information to the network in response to the logged MBMS information reporting request.

Reporting the logged MBMS information to the network may comprise immediately sending the logged MBMS information to the network in response to the logging of the MBMS information.

In another aspect, provided is a wireless device operating in a wireless communication system. The wireless device comprises a Radio Frequency (RF) unit which sends and receives radio signals and a processor which is functionally coupled to the RF unit and operates. The processor is configured to: determine whether or not to execute a logging of the MBMS information, log the MBMS information if the logging is determined to be performed and report the logged MBMS information to a network. Whether or not to execute the logging of the MBMS information is determined based on an MBMS information logging execution condition. The MBMS information logging execution condition comprises at least one of a reception failure of an MBMS service and reception quality of the MBMS service provided by the network.

In accordance with the method of reporting MBMS information according to an embodiment of the present invention, UE configured to report MBMS information can obtain and log MBMS information depending on the reception status or reception quality status of an MBMS service. Accordingly, a problem in which unnecessary power is consumed because UE obtains and logs MBMS information in the situation in which an MBMS service not related to the UE is provided or the UE is not provided with an MBMS service can be prevented. Furthermore, signaling overhead can be reduced because unnecessary signaling for reporting MBMS information by UE can be prevented, and thus use efficiency of radio resources can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system to which the present invention is applied.

FIG. 2 is a block diagram showing the structure of a wireless protocol on the user plane.

FIG. 3 is a block diagram showing the structure of a wireless protocol on the control plane.

FIG. 4 is a flowchart illustrating the operation of UE in the RRC idle state.

FIG. 5 is a flowchart illustrating a process of establishing RRC connection.

FIG. 6 is a flowchart illustrating an RRC connection reconfiguration process.

FIG. 7 is a diagram illustrating an RRC connection re-establishment procedure.

FIG. 8 is a flowchart illustrating a measuring method according to the related art.

FIG. 9 illustrates an example of measurement configuration in the terminal.

FIG. 10 illustrates an example of removing the measurement identity.

FIG. 11 illustrates an example of removing the measurement object.

FIG. 12 is a flowchart illustrating a method for performing a logged MDT.

FIG. 13 is a diagram illustrating an example of a logged MDT according to a logging area.

FIG. 14 is a diagram illustrating an example of a logged MDT according to a change of an RAT.

FIG. 15 is a diagram illustrating an example of logged measurements.

FIG. 16 is a diagram illustrating an example of an immediate MDT.

FIG. 17 is a diagram illustrating a method for reporting MBMS information in accordance with an embodiment of the present invention.

FIG. 18 is a diagram illustrating an example of a method for reporting MBMS information in accordance with an embodiment of the present invention.

FIG. 19 is a diagram illustrating another example of a method for reporting MBMS information in accordance with an embodiment of the present invention.

FIG. 20 is a block diagram illustrating a wireless device in which an embodiment of the present invention is implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system to which the present invention is applied. The wireless communication system may also be referred to as an evolved-UMTS terrestrial radio access network (E-UTRAN) or a long term evolution (LTE)/LTE-A system.

The E-UTRAN includes at least one base station (BS) 20 which provides a control plane and a user plane to a user equipment (UE) 10. The UE 10 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, etc. The BS 20 is generally a fixed station that communicates with the UE 10 and may be referred to as another terminology, such as an evolved node-B (eNB), a base transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20 are also connected by means of an S1 interface to an evolved packet core (EPC) 30, more specifically, to a mobility management entity (MME) through Sl-MME and to a serving gateway (S-GW) through Sl-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway (P-GW). The MME has access information of the UE or capability information of the UE, and such information is generally used for mobility management of the UE. The S-GW is a gateway having an E-UTRAN as an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network can be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. Among them, a physical (PHY) layer belonging to the first layer provides an information transfer service by using a physical channel, and a radio resource control (RRC) layer belonging to the third layer serves to control a radio resource between the UE and the network. For this, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a wireless protocol architecture for a user plane. FIG. 3 is a diagram showing a wireless protocol architecture for a control plane. The user plane is a protocol stack for user data transmission. The control plane is a protocol stack for control signal transmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with an information transfer service through a physical channel. The PHY layer is connected to a medium access control (MAC) layer which is an upper layer of the PHY layer through a transport channel. Data is transferred between the MAC layer and the PHY layer through the transport channel. The transport channel is classified according to how and with what characteristics data is transferred through a radio interface.

Data is moved between different PHY layers, that is, the PHY layers of a transmitter and a receiver, through a physical channel. The physical channel may be modulated according to an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and use the time and frequency as radio resources.

The functions of the MAC layer include mapping between a logical channel and a transport channel and multiplexing and demultiplexing to a transport block that is provided through a physical channel on the transport channel of a MAC Service Data Unit (SDU) that belongs to a logical channel. The MAC layer provides service to a Radio Link Control (RLC) layer through the logical channel.

The functions of the RLC layer include the concatenation, segmentation, and reassembly of an RLC SDU. In order to guarantee various types of Quality of Service (QoS) required by a Radio Bearer (RB), the RLC layer provides three types of operation mode: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). AM RLC provides error correction through an Automatic Repeat Request (ARQ).

The RRC layer is defined only on the control plane. The RRC layer is related to the configuration, reconfiguration, and release of radio bearers, and is responsible for control of logical channels, transport channels, and PHY channels. An RB means a logical route that is provided by the first layer (PHY layer) and the second layers (MAC layer, the RLC layer, and the PDCP layer) in order to transfer data between UE and a network.

The function of a Packet Data Convergence Protocol (PDCP) layer on the user plane includes the transfer of user data and header compression and ciphering. The function of the PDCP layer on the user plane further includes the transfer and encryption/integrity protection of control plane data.

What an RB is configured means a process of defining the characteristics of a wireless protocol layer and channels in order to provide specific service and configuring each detailed parameter and operating method. An RB can be divided into two types of a Signaling RB (SRB) and a Data RB (DRB). The SRB is used as a passage through which an RRC message is transmitted on the control plane, and the DRB is used as a passage through which user data is transmitted on the user plane.

If RRC connection is established between the RRC layer of UE and the RRC layer of an E-UTRAN, the UE is in the RRC connected state. If not, the UE is in the RRC idle state.

A downlink transport channel through which data is transmitted from a network to UE includes a broadcast channel (BCH) through which system information is transmitted and a downlink shared channel (SCH) through which user traffic or control messages are transmitted. Traffic or a control message for downlink multicast or broadcast service may be transmitted through the downlink SCH, or may be transmitted through an additional downlink multicast channel (MCH). Meanwhile, an uplink transport channel through which data is transmitted from UE to a network includes a random access channel (RACH) through which an initial control message is transmitted and an uplink shared channel (SCH) through which user traffic or control messages are transmitted.

Logical channels that are placed over the transport channel and that are mapped to the transport channel include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH).

The physical channel includes several OFDM symbols in the time domain and several subcarriers in the frequency domain. One subframe includes a plurality of OFDM symbols in the time domain. An RB is a resources allocation unit, and includes a plurality of OFDM symbols and a plurality of subcarriers. Furthermore, each subframe may use specific subcarriers of specific OFDM symbols (e.g., the first OFDM symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), that is, an L1/L2 control channel. A Transmission Time Interval (TTI) is a unit time for subframe transmission.

As disclosed in 3GPP TS 36.211 V8.7.0, a physical channel in a 3GPP LTE may be divided into a PDSCH (Physical Downlink Shared Channel) and a PUSCH (Physical Uplink Shared Channel) being a data channel and a PDCCH (Physical Downlink Control Channel), a PCFICH (Physical Control Format Indicator Channel), a PHICH (Physical Hybrid-ARQ Indicator Channel), and a PUCCH (Physical Uplink Control Channel) being a control channel.

A PCFICH transmitted through a first OFDM symbol of a sub-frame carries a CFI (control format indicator) with respect to the number of OFDM symbols used to transmit control channels in a sub-frame. The terminal firstly receives a CFI on a PCFICH to monitor the PDCCH.

The PDCCH refers to a scheduling channel to carry schedule information as a downlink control channel. The control information transmitted through the PDCCH refers to downlink control information (DCI). The DCI may include resource allocation of the PDSCH (refers to DL grant (downlink grant)), resource allocation of the PUSCH (refers to uplink (UL) grant)), and a group and/or VoIP (Voice over Internet Protocol) of a transmission power control command with respect to individual UEs in an optional UE group.

In the 3GPP LTE, blind decoding is used to detect the PDCCH. The blind decoding de-masks a desired identifier to a CRC (Cyclic Redundancy Check) of a received PDCCH (refers to candidate PDCCH), and checks a CRC error to determine whether a corresponding PDCCH is a control channel thereof.

The base station determines a PDCCH format according to a DCI to be sent to the terminal to attach a CRC to the DCI, and masks a unique identifier (refers to RNTI (Radio Network Temporary Identifier)) according to an owner or a use of the PDCCH.

The RRC state of UE and an RRC connection method are described below.

The RRC state means whether or not the RRC layer of UE is logically connected to the RRC layer of the E-UTRAN. A case where the RRC layer of UE is logically connected to the RRC layer of the E-UTRAN is referred to as an RRC connected state. A case where the RRC layer of UE is not logically connected to the RRC layer of the E-UTRAN is referred to as an RRC idle state. The E-UTRAN may check the existence of corresponding UE in the RRC connected state in each cell because the UE has RRC connection, so the UE may be effectively controlled. In contrast, the E-UTRAN is unable to check UE in the RRC idle state, and a Core Network (CN) manages UE in the RRC idle state in each tracking area, that is, the unit of an area greater than a cell. That is, the existence or non-existence of UE in the RRC idle state is checked only for each large area. Accordingly, the UE needs to shift to the RRC connected state in order to be provided with common mobile communication service, such as voice or data.

When a user first powers UE, the UE first searches for a proper cell and remains in the RRC idle state in the corresponding cell. The UE in the RRC idle state establishes RRC connection with an E-UTRAN through an RRC connection procedure when it is necessary to set up the RRC connection, and shifts to the RRC connected state. A case where UE in the RRC idle state needs to set up RRC connection includes several cases. For example, the cases may include a need to send uplink data for a reason, such as a call attempt by a user, and to send a response message as a response to a paging message received from an E-UTRAN.

A Non-Access Stratum (NAS) layer placed over the RRC layer performs functions, such as session management and mobility management.

In the NAS layer, in order to manage the mobility of UE, two types of states: EPS Mobility Management-REGISTERED (EMM-REGISTERED) and EMM-DEREGISTERED are defined. The two states are applied to UE and the MME. UE is initially in the EMM-DEREGISTERED state. In order to access a network, the UE performs a process of registering it with the corresponding network through an initial attach procedure. If the attach procedure is successfully performed, the UE and the MME become the EMM-REGISTERED state.

In order to manage signaling connection between UE and the EPC, two types of states: an EPS Connection Management (ECM)-IDLE state and an ECM-CONNECTED state are defined. The two states are applied to UE and the MME. When the UE in the ECM-IDLE state establishes RRC connection with the E-UTRAN, the UE becomes the ECM-CONNECTED state. The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes SI connection with the E-UTRAN. When the UE is in the ECM-IDLE state, the E-UTRAN does not have information about the context of the UE. Accordingly, the UE in the ECM-IDLE state performs procedures related to UE-based mobility, such as cell selection or cell reselection, without a need to receive a command from a network. In contrast, when the UE is in the ECM-CONNECTED state, the mobility of the UE is managed in response to a command from a network. If the location of the UE in the ECM-IDLE state is different from a location known to the network, the UE informs the network of its corresponding location through a tracking area update procedure.

System information is described below.

System information includes essential information that needs to be known by UE in order for the UE to access a BS. Accordingly, the UE needs to have received all pieces of system information before accessing the BS, and needs to always have the up-to-date system information. Furthermore, the BS periodically transmits the system information because the system information is information that needs to be known by all UEs within one cell. The system information is divided into a MIB (Master Information Block) and a plurality of SIBs (System Information Blocks).

The MIB may include a limited number of parameters which are most frequently transmitted and are required for acquisition for other information from a cell. The terminal firstly searches the MIB after downlink synchronization. The MIB may include information such as a downlink channel bandwidth, PHICH configuration, an SFN to support synchronization and to be operated as a timing reference, and eNB transmission antenna configuration. The MIB may be broadcasted on the BCH.

A SIB1 (SystemInformationBlockType1) among SIBs is transmitted while being included in a SystemInformationBlockType1, and other SIBs except for the SIB1 is transmitted while being included in the system information message. The SIBs may be flexibly mapped to the system information message according to a scheduling information list parameter included in the SIB1. However, each SIB is included in a single system information message, and only SIBs having the same scheduling required value (e.g. period) may be mapped to the same system information message. Further, a SIB2 (SystemInformationBlockType2) is mapped to a system information message corresponding to a first entry in a system information message list of a scheduling information list. A plurality of system information messages may be transmitted within the same time period. The SIB1 and all system information messages are transmitted on a DL-SCH.

Further to broadcast transmission, the E-UTRAN may be dedicated-signaled in a state that the SIB1 includes the same parameter as a preconfiguration value. In this case, the SIB1 may be transmitted while being included in a RRC connection reconfiguration message.

The SIB1 includes information on terminal cell access, and defines scheduling of other SIBs. The SIB1 may include PLMN identifiers of a network, a TAC (Tracking Area Code), a cell ID, a cell barring status to indicate whether a cell may camp-on, the lowest reception level required in a cell used as a cell reselection reference, and information on a transmission time and a time period of other SIBs.

The SIB2 may include radio resource configuration information common in all terminals. The SIB2 may include a uplink carrier frequency, an uplink channel bandwidth, RACH configuration, paging configuration, uplink power control configuration, sounding reference signal configuration, PUCCH configuration and PUSCH configuration supporting ACK/NACK transmission.

The terminal may apply acquisition and change sensing procedures of system information with respect to only a PCell. In the SCell, the E-UTRAN may provide all system information on the RRC connection state operation through dedicated signaling when a corresponding SCell is added. When system information on the configured SCell is changed, the E-UTRAN may release a considered SCell and may add the considered SCell later, which may be performed together with a single RRC connection reconfiguration message. The E-UTRAN may configure parameter values different from a value broadcasted in the considered SCell through the dedicated signaling.

The terminal should ensure validity with respect to system information of a specific type. The above system information refers to required system information. The required system information may be defined as follows.

• • When the terminal is in a RRC idle state: the terminal should to have a valid version of an MIB and the SIB1 as well as a SIB2 to a SIBS, which may depend on support of a considered RAT.
  • When the terminal is in a RRC connection state: the terminal should ensure to have valid versions of the MIB, the SIB1 and the SIB2.

In general, after the system information is acquired, validity may be ensured with a maximum three hours.

In general, service that is provided to UE by a network may be classified into three types as follows. Furthermore, the UE differently recognizes the type of cell depending on what service may be provided to the UE. In the following description, a service type is first described, and the type of cell is described.

1) Limited service: this service provides emergency calls and an Earthquake and Tsunami Warning System (ETWS), and may be provided by an acceptable cell.

2) Suitable service: this service means public service for common uses, and may be provided by a suitable cell (or a normal cell).

3) Operator service: this service means service for communication network operators. This cell may be used by only communication network operators, but may not be used by common users.

In relation to a service type provided by a cell, the type of cell may be classified as follows.

1) An acceptable cell: this cell is a cell from which UE may be provided with limited service. This cell is a cell that has not been barred from a viewpoint of corresponding UE and that satisfies the cell selection criterion of the UE.

2) A suitable cell: this cell is a cell from which UE may be provided with suitable service. This cell satisfies the conditions of an acceptable cell and also satisfies additional conditions. The additional conditions include that the suitable cell needs to belong to a Public Land Mobile Network (PLMN) to which corresponding UE may access and that the suitable cell is a cell on which the execution of a tracking area update procedure by the UE is not barred. If a corresponding cell is a CSG cell, the cell needs to be a cell to which UE may access as a member of the CSG.

3) A barred cell: this cell is a cell that broadcasts information indicative of a barred cell through system information.

4) A reserved cell: this cell is a cell that broadcasts information indicative of a reserved cell through system information.

FIG. 4 is a flowchart illustrating the operation of UE in the RRC idle state. FIG. 4 illustrates a procedure in which UE that is initially powered on experiences a cell selection process, registers it with a network, and then performs cell reselection if necessary.

Referring to FIG. 4, the UE selects Radio Access Technology (RAT) in which the UE communicates with a Public Land Mobile Network (PLMN), that is, a network from which the UE is provided with service (S410). Information about the PLMN and the RAT may be selected by the user of the UE, and the information stored in a Universal Subscriber Identity Module (USIM) may be used.

The UE selects a cell that has the greatest value and that belongs to cells having measured BS and signal intensity or quality greater than a specific value (cell selection) (S420). In this case, the UE that is powered off performs cell selection, which may be called initial cell selection. A cell selection procedure is described later in detail. After the cell selection, the UE receives system information periodically by the BS. The specific value refers to a value that is defined in a system in order for the quality of a physical signal in data transmission/reception to be guaranteed. Accordingly, the specific value may differ depending on applied RAT.

If network registration is necessary, the UE performs a network registration procedure (S430). The UE registers its information (e.g., an IMSI) with the network in order to receive service (e.g., paging) from the network. The UE does not register it with a network whenever it selects a cell, but registers it with a network when information about the network (e.g., a Tracking Area Identity (TAI)) included in system information is different from information about the network that is known to the UE.

The UE performs cell reselection based on a service environment provided by the cell or the environment of the UE (S440). If the value of the intensity or quality of a signal measured based on a BS from which the UE is provided with service is lower than that measured based on a BS of a neighboring cell, the UE selects a cell that belongs to other cells and that provides better signal characteristics than the cell of the BS that is accessed by the UE. This process is called cell reselection differently from the initial cell selection of the No. 2 process. In this case, temporal restriction conditions are placed in order for a cell to be frequently reselected in response to a change of signal characteristic. A cell reselection procedure is described later in detail.

FIG. 5 is a flowchart illustrating a process of establishing RRC connection.

UE sends an RRC connection request message that requests RRC connection to a network (S510). The network sends an RRC connection establishment message as a response to the RRC connection request (S520). After receiving the RRC connection establishment message, the UE enters RRC connected mode.

The UE sends an RRC connection establishment complete message used to check the successful completion of the RRC connection to the network (S530).

FIG. 6 is a flowchart illustrating an RRC connection reconfiguration process. An RRC connection reconfiguration is used to modify RRC connection. This is used to establish/modify/release RBs, perform handover, and set up/modify/release measurements.

A network sends an RRC connection reconfiguration message for modifying RRC connection to UE (S610). As a response to the RRC connection reconfiguration message, the UE sends an RRC connection reconfiguration complete message used to check the successful completion of the RRC connection reconfiguration to the network (S620).

Hereinafter, a public land mobile network (PLMN) is described.

The PLMN is a network which is disposed and operated by a mobile network operator. Each mobile network operator operates one or more PLMNs. Each PLMN may be identified by a Mobile Country Code (MCC) and a Mobile Network Code (MNC). PLMN information of a cell is included in system information and broadcasted.

In PLMN selection, cell selection, and cell reselection, various types of PLMNs may be considered by the terminal.

Home PLMN (HPLMN): PLMN having MCC and MNC matching with MCC and MNC of a terminal IMSI.

Equivalent HPLMN (EHPLMN): PLMN serving as an equivalent of an HPLMN.

Registered PLMN (RPLMN): PLMN successfully finishing location registration.

Equivalent PLMN (EPLMN): PLMN serving as an equivalent of an RPLMN.

Each mobile service consumer subscribes in the HPLMN. When a general service is provided to the terminal through the HPLMN or the EHPLMN, the terminal is not in a roaming state. Meanwhile, when the service is provided to the terminal through a PLMN except for the HPLMN/EHPLMN, the terminal is in the roaming state. In this case, the PLMN refers to a Visited PLMN (VPLMN).

When UE is initially powered on, the UE searches for available Public Land Mobile Networks (PLMNs) and selects a proper PLMN from which the UE is able to be provided with service. The PLMN is a network that is deployed or operated by a mobile network operator. Each mobile network operator operates one or more PLMNs. Each PLMN may be identified by Mobile Country Code (MCC) and Mobile Network Code (MNC). Information about the PLMN of a cell is included in system information and broadcasted. The UE attempts to register it with the selected PLMN. If registration is successful, the selected PLMN becomes a Registered PLMN (RPLMN). The network may signalize a PLMN list to the UE. In this case, PLMNs included in the PLMN list may be considered to be PLMNs, such as RPLMNs. The UE registered with the network needs to be able to be always reachable by the network. If the UE is in the ECM-CONNECTED state (identically the RRC connection state), the network recognizes that the UE is being provided with service. If the UE is in the ECM-IDLE state (identically the RRC idle state), however, the situation of the UE is not valid in an eNB, but is stored in the MME. In such a case, only the MME is informed of the location of the UE in the ECM-IDLE state through the granularity of the list of Tracking Areas (TAs). A single TA is identified by a Tracking Area Identity (TAI) formed of the identifier of a PLMN to which the TA belongs and Tracking Area Code (TAC) that uniquely expresses the TA within the PLMN.

Thereafter, the UE selects a cell that belongs to cells provided by the selected PLMN and that has signal quality and characteristics on which the UE is able to be provided with proper service.

The following is a detailed description of a procedure of selecting a cell by a terminal.

When power is turned-on or the terminal is located in a cell, the terminal performs procedures for receiving a service by selecting/reselecting a suitable quality cell.

A terminal in an RRC idle state should prepare to receive a service through the cell by always selecting a suitable quality cell. For example, a terminal where power is turned-on just before should select the suitable quality cell to be registered in a network. If the terminal in an RRC connection state enters in an RRC idle state, the terminal should selects a cell for stay in the RRC idle state. In this way, a procedure of selecting a cell satisfying a certain condition by the terminal in order to be in a service idle state such as the RRC idle state refers to cell selection. Since the cell selection is performed in a state that a cell in the RRC idle state is not currently determined, it is important to select the cell as rapid as possible. Accordingly, if the cell provides a wireless signal quality of a predetermined level or greater, although the cell does not provide the best wireless signal quality, the cell may be selected during a cell selection procedure of the terminal.

A method and a procedure of selecting a cell by a terminal in a 3GPP LTE is described with reference to 3GPP TS 36.304 V8.5.0 (2009-03) “User Equipment (UE) procedures in idle mode (Release 8)”.

A cell selection process is basically divided into two types.

The first is an initial cell selection process. In this process, UE does not have preliminary information about a wireless channel. Accordingly, the UE searches for all wireless channels in order to find out a proper cell. The UE searches for the strongest cell in each channel. Thereafter, if the UE has only to search for a suitable cell that satisfies a cell selection criterion, the UE selects the corresponding cell.

Next, the UE may select the cell using stored information or using information broadcasted by the cell. Accordingly, cell selection may be fast compared to an initial cell selection process. If the UE has only to search for a cell that satisfies the cell selection criterion, the UE selects the corresponding cell. If a suitable cell that satisfies the cell selection criterion is not retrieved though such a process, the UE performs an initial cell selection process.

A cell selection reference may be defined as expressed by a following equation 1.

Srxlev>0 AND Squal>0   [Equation 1]

where:

Srxlev=Q_rxlevmeas−(Q_rxlevmin+Q_{rxlevminoffset})−Pcompensation

Squal=Q_qualmeas−(Q_qualmin+Q_{qualminoffset})

In this case, respective variables of the equation I may be defined by a following table 1.

TABLE 1
Srxlev          Cell selection RX level value (dB)
Squal           Cell selection quality value (dB)
Qrxlevmeas      Measured cell RX level value (RSRP)
Qqualmeas       Measured cell quality value (RSRQ)
Qrxlevmin       Minimum required RX level in the cell (dBm)
Qqualmin        Minimum required quality level in the cell (dB)
Qrxlevminoffset Offset to the signalled Qrxlevmin taken into account in the
                Srxlev evaluation as a result of a periodic search for a
                higher priority PLMN while camped normally in a
                VPLMN [5]
Qqualminoffset  Offset to the signalled Qqualmin taken into account in the
                Squal evaluation as a result of a periodic search for a
                higher priority PLMN while camped normally in a
                VPLMN [5]
Pcompensation   max(PEMAX − PPowerClass, 0) (dB)
PEMAX           Maximum TX power level an UE may use when
                transmitting on the uplink in the cell (dBm) defined as
                PEMAX in [TS 36.101]
PPowerClass     Maximum RF output power of the UE (dBm) according
                to the UE power class as defined in [TS 36.101]

Signaled values Qrxlevminoffset and Qqualminoffset are a result of periodic search with respect to a PLMN of a higher priority while the terminal camps on a normal cell in the VPLMN. During the periodic search with the PLMN having the higher priority, the terminal may perform cell selection estimation using stored parameters from other cell of the PLMN having the higher priority.

After the UE selects a specific cell through the cell selection process, the intensity or quality of a signal between the UE and a BS may be changed due to a change in the mobility or wireless environment of the UE. Accordingly, if the quality of the selected cell is deteriorated, the UE may select another cell that provides better quality. If a cell is reselected as described above, the UE selects a cell that provides better signal quality than the currently selected cell. Such a process is called cell reselection. In general, a basic object of the cell reselection process is to select a cell that provides UE with the best quality from a viewpoint of the quality of a radio signal.

In addition to the viewpoint of the quality of a radio signal, a network may determine priority corresponding to each frequency, and may inform the UE of the determined priorities. The UE that has received the priorities preferentially takes into consideration the priorities in a cell reselection process compared to a radio signal quality criterion.

As described above, there is a method of selecting or reselecting a cell according to the signal characteristics of a wireless environment. In selecting a cell for reselection when a cell is reselected, the following cell reselection methods may be present according to the RAT and frequency characteristics of the cell.

• • Intra-frequency cell reselection: UE reselects a cell having the same center frequency as that of RAT, such as a cell on which the UE camps on.
  • Inter-frequency cell reselection: UE reselects a cell having a different center frequency from that of RAT, such as a cell on which the UE camps on
  • Inter-RAT cell reselection: UE reselects a cell that uses RAT different from RAT on which the UE camps

The principle of a cell reselection process is as follows.

First, UE measures the quality of a serving cell and neighbor cells for cell reselection.

Second, cell reselection is performed based on a cell reselection criterion. The cell reselection criterion has the following characteristics in relation to the measurements of a serving cell and neighbor cells.

Intra-frequency cell reselection is basically based on ranking. Ranking is a task for defining a criterion value for evaluating cell reselection and numbering cells using criterion values according to the size of the criterion values. A cell having the best criterion is commonly called the best-ranked cell. The cell criterion value is based on the value of a corresponding cell measured by UE, and may be a value to which a frequency offset or cell offset has been applied, if necessary.

Inter-frequency cell reselection is based on frequency priority provided by a network. UE attempts to camp on a frequency having the highest frequency priority. A network may provide frequency priority that will be applied by UEs within a cell in common through broadcasting signaling, or may provide frequency-specific priority to each UE through UE-dedicated signaling. A cell reselection priority provided through broadcast signaling may refer to a common priority. A cell reselection priority for each terminal set by a network may refer to a dedicated priority. If receiving the dedicated priority, the terminal may receive a valid time associated with the dedicated priority together. If receiving the dedicated priority, the terminal starts a validity timer set as the received valid time together therewith. While the valid timer is operated, the terminal applies the dedicated priority in the RRC idle mode. If the valid timer is expired, the terminal discards the dedicated priority and again applies the common priority.

For the inter-frequency cell reselection, a network may provide UE with a parameter (e.g., a frequency-specific offset) used in cell reselection for each frequency.

For the intra-frequency cell reselection or the inter-frequency cell reselection, a network may provide UE with a Neighboring Cell List (NCL) used in cell reselection. The NCL includes a cell-specific parameter (e.g., a cell-specific offset) used in cell reselection.

For the intra-frequency or inter-frequency cell reselection, a network may provide UE with a cell reselection black list used in cell reselection. The UE does not perform cell reselection on a cell included in the black list.

Ranking performed in a cell reselection evaluation process is described below.

A ranking criterion used to apply priority to a cell is defined as in Equation 1.

R_s=Q_meas,s+Q_hyst,R_n=Q_meas,s−Q_offset   [Equation 1]

In this case, R_s is the ranking criterion of a serving cell, R_n is the ranking criterion of a neighbor cell, Q_meas,s is the quality value of the serving cell measured by UE, Q_meas,n is the quality value of the neighbor cell measured by UE, Q_hyst is the hysteresis value for ranking, and Q_offset is an offset between the two cells.

In Intra-frequency, if UE receives an offset “Q_offsets,n” between a serving cell and a neighbor cell, Q_offset=Q_offsets,n. If UE does not receive Q_offsets,n, Q_offset=0.

In Inter-frequency, if UE receives an offset “Q_offsets,n” for a corresponding cell, Q_offset=Q_offsets,n+Q_frequency. If UE does not receive “Q_offsets,n”, Q_offset=Q_frequency.

If the ranking criterion R_s of a serving cell and the ranking criterion R_n of a neighbor cell are changed in a similar state, ranking priority is frequency changed as a result of the change, and UE may alternately reselect the twos. Q_hyst is a parameter that gives hysteresis to cell reselection so that UE is prevented from to alternately reselecting two cells.

UE measures R_s of a serving cell and R_n, of a neighbor cell according to the above equation, considers a cell having the greatest ranking criterion value to be the highest-ranked cell, and reselects the cell.

In accordance with the criterion, it may be checked that the quality of a cell is the most important criterion in cell reselection. If a reselected cell is not a suitable cell, UE excludes a corresponding frequency or a corresponding cell from the subject of cell reselection.

In order to perform the cell reselection according to the cell reselection estimation, when the cell reselection reference is satisfied for a specific time, the terminal determines that the cell reselection reference is satisfied and may perform cell movement to a selected target cell. In this case, the specific time may be given from the network as a Treselection parameter. The Treselection may specify a cell reselection timer value, and may be defined with respect to each frequency of the E-UTRAN and other RAT.

Hereinafter, cell reselection information used for cell reselection of the terminal will be described.

The cell reselection information is a type of a cell reselection parameter and may be transmitted and provided to the terminal while being included in the system information broadcasted from the network. The cell reselection parameter provided to the terminal may include following types.

Cell reselection priority cellReselectionPriority: The cellReselectionPriority parameter specifies a priority with respect to a frequency of the E-UTRAN, a frequency of a UTRAN, a group of GERAN frequencies, a band glass of a CDMA2000 HRPD or a band glass of a CDMA2000 1xRTT.

Qoffset_s,n: specifies an offset value between two cells.

Qoffset_frequency: specifies frequency specific offset with respect to an E-UTRAN frequency having the same priority.

Q_hyst: specifies a hysteresis value with respect a rank index.

Q_qualmin: specifies a required minimum quality level in a dB unit.

Q_rxlevmin: specifies a required minimum Rx in a dB unit.

Treselection_EUTRA: may specify a cell reselection timer value for the E-UTRAN, and may be configured with respect to each frequency of the E-UTRAN.

Treselection_UTRAN: specifies a cell reselection timer value for the UTRAN.

Treselection_GERA: specifies a cell reselection timer value for the GERAN.

Treselection_CDMA—HRPD: specifies a cell reselection timer value for CDMA HRPD.

Treselection_CDMA—1xRTT: specifies a cell reselection timer value for CDMA 1xRTT.

Thresh_{x, HighP}: specifies a Srxlev threshold value used by a terminal upon cell reselection to an RAT/frequency having a priority higher than a serving frequency. A specific threshold value may be independently configured with respect to each frequency of the E-UTRAN and the UTRAN, each group of a GERAN frequency, each band glass of CDMA2000 HRPD and each band glass of CDMA2000 1xRTT.

Thresh_{x, HighQ}: When cell reselection to RAT/frequency having a priority higher than the serving frequency is performed, a Squal threshold value used by a terminal is specified in a dB unit. The specific threshold value may be independently configured with respect to each frequency of the E-UTRAN and a UTRAN FDD.

Thresh_{x, LowP}: When cell reselection to RAT/frequency having a priority lower than the serving frequency is performed, a Srxlev threshold value used by a terminal is specified in a dB unit. The specific threshold value may be independently configured with respect to each frequency of the E-UTRAN and a UTRAN FDD, each group of a GERAN frequency, each band glass of a CDMA2000 HRPD and each band glass of CDMA2000 1xRTT.

Thresh_{x, LowQ}: When cell reselection to RAT/frequency having a priority lower than the serving frequency is performed, a Squal threshold value used by a terminal is specified in a dB unit. The specific threshold value may be independently configured with respect to each frequency of the E-UTRAN and a UTRAN FDD.

Thresh_{Serving, LowP}: When cell reselection to RAT/frequency having a priority lower than the serving frequency is performed, a Srxlev threshold value used by a terminal is specified in a dB unit.

Thresh_{Serving, LowQ}: When cell reselection to RAT/frequency having a priority lower than the serving frequency is performed, a Squal threshold value used by a terminal is specified in a dB unit.

S_IntraSearchP: specifies a Srxlev threshold value with respect to intra-frequency measurement in a dB unit.

S_IntraSearchQ: specifies a Squal threshold value with respect to intra-frequency measurement in a dB unit.

S_{nonIntraSerachP}: specifies E-UTRAN inter-frequency and a Srxlev threshold value with respect to inter-RAT measurement.

S_{nonIntraSearchQ}: specifies E-UTRAN inter-frequency and a Squal threshold value with respect to E-UTRAN inter-frequency and inter-RAT measurement.

Meanwhile, the cell reselection information may be provided while being included in a RRC connection release message which is a RRC message transmitted for RRC connection release between the network and the terminal. For example, the RRC connection release message may include a sub-carrier frequency list and cell reselection priority of the E-UTRAN, a sub-carrier frequency list and cell reselection priority of the UTRA-FDD, a sub-carrier frequency list and cell reselection priority of the UTRA-TDD, a sub-carrier frequency list and cell reselection priority of the GERAN, a band glass list and cell reselection priority of the CDMA2000 HRPD, and a band glass list and cell reselection priority of CDMA2000 1xRTT.

Hereinafter, radio link monitoring (RLM) will be described.

The terminal monitors downlink quality based on a cell-specific reference signal in order to detect downlink radio link quality of a PCell. The terminal estimates the downlink radio link quality for the purpose of monitoring downlink radio link quality of the PCell and compares the estimated downlink radio link quality with threshold values Qout and Qin. The threshold values Qout is defined as a level at which a downlink radio link may not be received, which corresponds to a 10% block error rate of hypothetical PDCCH transmission by taking into consideration a PDFICH error. The threshold value Qin is defined as a downlink radio link quality level which may be stable more than a level of the threshold value Qout, which corresponds to a 2% block error rate of hypothetical PDCCH transmission by taking into consideration the PCFICH error.

A Radio Link Failure (RLF) is described below.

UE continues to perform measurements in order to maintain the quality of a radio link with a serving cell from which the UE receives service. The UE determines whether or not communication is impossible in a current situation due to the deterioration of the quality of the radio link with the serving cell. If communication is almost impossible because the quality of the serving cell is too low, the UE determines the current situation to be an RLF.

If the RLF is determined, the UE abandons maintaining communication with the current serving cell, selects a new cell through cell selection (or cell reselection) procedure, and attempts RRC connection re-establishment with the new cell.

In the specification of 3GPP LTE, the following examples are taken as cases where normal communication is impossible.

• • A case where UE determines that there is a serious problem in the quality of a downlink communication link (a case where the quality of a PCell is determined to be low while performing RLM) based on the radio quality measured results of the PHY layer of the UE
  • A case where uplink transmission is problematic because a random access procedure continues to fail in the MAC sublayer.
  • A case where uplink transmission is problematic because uplink data transmission continues to fail in the RLC sublayer.
  • A case where handover is determined to have failed.
  • A case where a message received by UE does not pass through an integrity check.

An RRC connection re-establishment procedure is described in more detail below.

FIG. 7 is a diagram illustrating an RRC connection re-establishment procedure.

Referring to FIG. 7, UE stops using all the radio bearers that have been configured other than a Signaling Radio Bearer (SRB) #0, and initializes a variety of kinds of sublayers of an Access Stratum (AS) (S710). Furthermore, the UE configures each sublayer and the PHY layer as a default configuration. In this process, the UE maintains the RRC connection state.

The UE performs a cell selection procedure for performing an RRC connection reconfiguration procedure (S720). The cell selection procedure of the RRC connection re-establishment procedure may be performed in the same manner as the cell selection procedure that is performed by the UE in the RRC idle state, although the UE maintains the RRC connection state.

After performing the cell selection procedure, the UE determines whether or not a corresponding cell is a suitable cell by checking the system information of the corresponding cell (S730). If the selected cell is determined to be a suitable E-UTRAN cell, the UE sends an RRC connection re-establishment request message to the corresponding cell (S740).

Meanwhile, if the selected cell is determined to be a cell that uses RAT different from that of the E-UTRAN through the cell selection procedure for performing the RRC connection re-establishment procedure, the UE stops the RRC connection re-establishment procedure and enters the RRC idle state (S750).

The UE may be implemented to finish checking whether the selected cell is a suitable cell through the cell selection procedure and the reception of the system information of the selected cell. To this end, the UE may drive a timer when the RRC connection re-establishment procedure is started. The timer may be stopped if it is determined that the UE has selected a suitable cell. If the timer expires, the UE may consider that the RRC connection re-establishment procedure has failed, and may enter the RRC idle state. Such a timer is hereinafter called an RLF timer. In LTE spec TS 36.331, a timer named “T311” may be used as an RLF timer. The UE may obtain the set value of the timer from the system information of the serving cell.

If an RRC connection re-establishment request message is received from the UE and the request is accepted, a cell sends an RRC connection re-establishment message to the UE.

The UE that has received the RRC connection re-establishment message from the cell reconfigures a PDCP sublayer and an RLC sublayer with an SRB1. Furthermore, the UE calculates various key values related to security setting, and reconfigures a PDCP sublayer responsible for security as the newly calculated security key values. Accordingly, the SRB 1 between the UE and the cell is open, and the UE and the cell may exchange RRC control messages. The UE completes the restart of the SRB1, and sends an RRC connection re-establishment complete message indicative of that the RRC connection re-establishment procedure has been completed to the cell (S760).

In contrast, if the RRC connection re-establishment request message is received from the UE and the request is not accepted, the cell sends an RRC connection re-establishment reject message to the UE.

If the RRC connection re-establishment procedure is successfully performed, the cell and the UE perform an RRC connection reconfiguration procedure. Accordingly, the UE recovers the state prior to the execution of the RRC connection re-establishment procedure, and the continuity of service is guaranteed to the upmost.

FIG. 8 is a flowchart illustrating a measuring method according to the related art.

The terminal receives measurement configuration information from a base station (S810). A message including measurement configuration information refers to a measurement configuration message. The terminal performs measurement based on the measurement configuration information (S820). If the measurement result satisfies a report condition in the measurement configuration information, the terminal reports the measurement result to the base station. A message including the measurement result refers to a measurement report message.

The measurement configuration information may include following information.

(1) Measurement object information: represents information on an object to be measured by the terminal. The measurement object includes at least one of an intra-frequency measurement object being a measurement object in a cell, an inter-frequency measurement object being a measurement object between cells, and an inter-RAT measurement object being an inter-RAT measurement object. For example, the inter-frequency measurement object may indicate a neighboring cell having the same frequency band as that of the serving cell, the inter-frequency measurement object may indicate a neighboring cell having a frequency band different from that of the serving cell, and an inter-RAT measurement object may indicate a neighboring cell of a RAT different from that of the serving cell.

(2) Reporting configuration information: represents information on a reporting condition and a reporting type when transmission of the measurement result is reported. The reporting configuration information may be configured as a list of reporting configuration. Each reporting configuration may include a reporting criterion and a reporting format. The reporting criterion is a criterion triggering transmission of the measurement result by the terminal. The reporting criterion may include a period of a measurement reporting or a single event for the measurement reporting. The reporting format is information on which type the terminal configures the measurement result.

(3) Measurement identity information: represents information on a measurement identity to determine when the terminal reports a certain measurement object as a certain type by associating the measuring reporting with reporting configuration. The measurement identity information is included in the measurement reporting message, which may represent which measurement object is the measurement result and in which reporting condition the measurement reporting is generated.

(4) Quantity configuration information: represents information on a parameter for configuring filtering of a measurement unit, a reporting unit, and/or a measurement result value.

(5) Measurement gap information: represents information on a measurement gap which is an interval when the terminal may use for measurement without considering data transmission with the serving cell because downlink transmission or uplink transmission is not scheduled.

The terminal has a measurement object list, a measurement reporting configuration list, and a measurement identity list in order to perform a measurement procedure.

In the 3GPP LTE, the base station may configure only one measurement object with respect to one frequency band to the terminal. According to section 5.5.4 of 3GPP TS 36.331 V8.5.0 (2009-03) “Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource Control (RRC); Protocol specification (Release 8)”, events resulting in the measurement reporting as listed in a following table 2 are defined.

TABLE 2
Event    Reporting condition
Event A1 Serving becomes better than threshold
Event A2 Serving becomes worse than threshold
Event A3 Neighbour becomes offset better than serving
Event A4 Neighbour becomes better than threshold
Event A5 Serving becomes worse than threshold1 and neighbour
         becomes better than threshold2
Event B1 Inter RAT neighbour becomes better than threshold
Event B2 Serving becomes worse than threshold1 and inter RAT
         neighbour becomes better than threshold2

If the measurement result of the terminal satisfies the configured event, the terminal transmits a measurement reporting message to the base station.

FIG. 9 illustrates an example of measurement configuration in the terminal.

First, the measurement identity 1 ( 901) connects an intra-frequency measurement object with a reporting configuration 1. The terminal performs intra frequency measurement, and the reporting configuration 1 is used to determine criterion and type of the measurement result reporting.

As in the measurement identity 1 ( 901), the measurement identity 2 ( 902) is connected to the intra-frequency measurement object, but connects the intra-frequency measurement object to the reporting configuration 2. The terminal performs measurement and the reporting configuration 2 is used to determine criterion and type of the measurement result reporting.

According to a measurement identity 1 ( 901) and a measurement identity 2 ( 902), even if a measurement result with respect to the intra-frequency measurement object satisfies one of reporting configuration 1 and reporting configuration 2, the terminal transmits the measurement result.

The measurement identity 3 ( 903) connects the inter-frequency measurement object 1 to the reporting configuration 3. If the measurement result with respect to the inter-frequency measurement object 1 satisfies a reporting condition included in the reporting configuration 1, the terminal reports the measurement result.

The measurement identity 4 ( 904) connects the inter-frequency measurement object 2 to the reporting configuration 2. If the measurement result with respect to the inter-frequency measurement object 2 satisfies a reporting condition included in the reporting configuration 2, the terminal reports the measurement result.

Meanwhile, the measurement object, reporting configuration and/or measurement identity may be added, changed, and/or removed. This may be indicated by sending a new measurement configuration message or the measurement configuration change message to the terminal.

FIG. 10 illustrates an example of removing the measurement identity. If the measurement identity 2 ( 902) is removed, measurement with respect to a measurement object associated with the measurement identity 2 ( 902) is stopped and the measurement reporting is not transmitted. The measurement object associated with the removed measurement identity or the reporting configuration may not be changed.

FIG. 11 illustrates an example of removing the measurement object. If the inter-frequency measurement object 1 is removed, the terminal also remove the measurement identity 3 ( 903) associated with the inter-frequency measurement object 1. Measurement with respect to the inter-frequency measurement object 1 is stopped and the measurement reporting is not transmitted. However, the reporting configuration associated with the remove inter-frequency measurement object 1 may not be changed or removed.

If the reporting configuration is removed, the terminal also removes a measurement identity associated with the reporting configuration. The terminal stops measurement with respect to the measurement object associated with the associated measurement identity. However, the measurement object associated with the removed reporting configuration may not be changed or removed.

The measurement reporting may include a measurement identity, measured quality of the serving cell and a measurement result of the neighboring cell. The measurement identity identifies a measurement object to which the measurement report is triggered. The measurement result of the neighboring cell may include a cell identity and measured quality of the neighboring cell. The measured quality may include at least one of Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ).

FIG. 12 is a flowchart illustrating a method for performing a logged MDT.

Referring to FIG. 12, UE receives a logged measurement configuration (S1210). The logged measurement configuration may be included in an RRC message and transmitted as a downlink control channel. The logged measurement configuration may include at least one of pieces of information about a TCE ID, a reference time that is a criterion in performing logging, logging duration, a logging interval, and an area configuration. The logging interval is indicative of an interval in which a measured result is stored. The logging duration is indicative of duration in which UE performs a logged MDT. The reference time is indicative of the time, that is, a criterion for duration in which a logged MDT is performed. The area configuration is indicative of an area on which UE has been requested to perform logging.

Meanwhile, the UE starts a validity timer when it receives the logged measurement configuration. The validity timer means the lifetime of the logged measurement configuration, and may be specified based on information about logging duration. The duration of the validity timer may also indicate the validity of a measured result owned by the UE in addition to the valid lifetime of the logged measurement configuration.

A procedure in which the UE receives the logged measurement configuration and a corresponding overall procedure is performed as described above is called a configuration phase.

When the UE enters an RRC idle state (S1221), the UE logs a measured result while the validity timer is driven (S1222). The value of the measured result may be RSRP, RSRQ, Received Signal Code Power (RSCP), or Ec/No. Information obtained by logging the measured result is called a logged measurement and/or a measured result log. A temporal phase in which UE logs a measured result more than once is called a logging phase.

The execution of a logged MDT based on a logged measurement configuration by UE may be changed depending on a place where the UE is present.

FIG. 13 is a diagram illustrating an example of a logged MDT according to a logging area.

A network may configure a logging area, that is, an area in which UE needs to perform logging. The logging area may be represented in the form of a cell list or may be represented in the form of a tracking area/location area list. If a logging area has been configured for the UE, the UE stops logging when it deviates from the logging area.

Referring to FIG. 13, a first area 1310 and a third area 1330 are areas configured as a logging area, and a second area 1320 is an area in which logging is not permitted. The UE performs logging in the first area 1310, but does not perform logging in the second area 1320. The UE performs logging again when it moves from the second area 1320 to the third area 1330.

FIG. 14 is a diagram illustrating an example of a logged MDT according to a change of an RAT.

UE performs logging only when it camps on an RAT through which a logged measurement configuration has been received, but stops logging in other RATs. In this case, the UE may log cell information of another RAT in addition to the RAT in which the UE camps on.

A first area 1410 and a third area 1430 are E-UTRAN areas, and a second area 1420 is a UTRAN area. A logged measurement configuration is received from the E-UTRAN. The UE does not perform MDT measurements when it enters the second area 1420.

Referring back to FIG. 12, if the UE enters an RRC connected state (S1231) and has logged measurements to be reported, the UE notifies an eNB that it has the logged measurements to be reported (S1232). When the UE has established RRC connection or re-established RRC connection or RRC connection is reconfigured, the UE may notify the eNB that it has the logged measurements. Furthermore, if the UE performs handover, it may notify a target handover cell that it has the logged measurements. To notify, by the UE, the eNB of the logged measurements may include including a logged measurement availability indicator, that is, indication information providing notification of the presence of the logged measurements, in an RRC message transmitted from the UE to the eNB and sending the RRC message. The RRC message may be an RRC connection establishment-complete message, an RRC connection re-establishment-complete message, an RRC reconfiguration-complete message, or a handover-complete message.

When the eNB receives a signal providing notification of the presence of the logged measurements from the UE, it requests the UE to report the logged measurements (S1233). To request the report on the logged measurements may include including a logged measurement reporting request parameter regarding information indicative of the logged measurements in an RRC message and sending the RRC message. The RRC message may be a UE information request message.

When the UE receives the request for the report on the logged measurements from the eNB, it reports the logged measurements to the eNB (S1234). To report the logged measurements to the eNB may include including a logged measurement report, including the logged measurements, in an RRC message and sending the RRC message to the eNB. The RRC message may be a UE information report message. In reporting the logged measurements, the UE may report all of the logged measurements owned by the UE to the eNB or some of the logged measurements owned by the UE to the eNB at a point of time at which the report is made. If some of the logged measurements owned by the UE is reported, the reported some logged measurements may be discarded.

A phase in which a process of notifying, by UE, an eNB of the presence of logged measurements, receiving a request for a report from the eNB, and reporting the logged measurements is performed as described above is called a reporting phase.

While a logged MDT is performed, a subject measured by UE is chiefly related to a wireless environment. The MDT measurements may include a cell identity and the signal quality and/or signal intensity of a cell. The MDT measurements may include a measurement time and a measurement place. Table 3 below illustrates contents logged by UE.

TABLE 3
PARAMETER
(SET)            DESCRIPTION
Serving cell     Global cell identity of a serving cell
identity
Measured result  Measured Reference Signal Received Power (RSRP)
of serving cell  of a serving cell
                 Measured Reference Signal Received Quality (RSRQ)
                 of a serving cell
Measured result  Cell identities of measured E-UTRA cells, Measured
of neighbor cell result of E-UTRA cells
                 Cell identities of measured UTRA cells, Measured
                 result of UTRA cells
                 Cell Identities of measured GERAN cells, Measured
                 result of GERAN cells
                 Cell Identities of measured CDMA 2000 cells,
                 Measured result of CDMA 2000 cells
Time stamp       The moment of a logging measured result, calculated
                 as {current time minus absoluteTimeStamp}
                 in seconds
Location         Detailed location information at the moment of logging
information

Information logged at different logging points of time may be stored so that it is divided into different log entries as follows.

FIG. 15 is a diagram illustrating an example of logged measurements.

The logged measurements include one or more log entries.

The log entry includes a logging location, a logging time, a serving cell identity, a serving measured result, and a neighbor cell measured result.

The logging location is indicative of a location in which UE has performed measurements. The logging time is indicative of the time when UE performed measurements. Information logged on a different logging time is stored in a different log entry.

The serving cell identity may include a cell identity in Layer 3, which is called a Global Cell Identity (GCI). The GCI is a set of a Physical Cell Identity (PCI) and a PLMN identity.

Meanwhile, UE may analyze and log indices related to performance of the UE in addition to a wireless environment. For example, the indices may include a throughput and an erroneous transmission/reception rate).

Referring back to FIG. 12, the aforementioned logging phase and reporting phase may be present in the logging duration in plural times (S1241, S1242).

The eNB may record/store the logged measurements in a TCE when it receives a report on the logged measurements.

After the validity timer expires, that is, after a lapse of the logging duration, if the UE has logged measurements that have not yet been reported, the UE performs a procedure for reporting the logged measurements to the eNB. A phase in which an overall procedure for reporting the logged measurements to the eNB is performed is called a post-reporting phase.

After the logging duration is terminated, the UE discards the logged measurement configuration and starts a conservation timer. After the logging duration is terminated, the UE stops MDT measurements. However already logged measurements remain without being discarded. The conservation timer is indicative of the lifetime of the remaining logged measurements.

If the UE enters an RRC connected state before the conservation timer expires (S1251), the UE may report logged measurements that have not yet been reported to the eNB. In this case, the aforementioned procedures for reporting the logged measurements may be performed (S1252, S1253, and S1254). When the conservation timer expires, the remaining logged measurements may be discarded. The eNB may record/store the logged measurements when a report on the logged measurements is received.

The conservation timer may be fixed to a predetermined value for the UE and may be previously set in the UE. For example, the value of the conservation timer may be 48 hours. Alternatively, the value of the conservation timer may be included in a logged measurement configuration and delivered to the UE or may be included another RRC message and delivered to the UE.

Meanwhile, when a new logged measurement configuration is transferred to the UE, the UE may update an existing logged measurement configuration with the newly obtained logged measurement configuration. In this case, a validity timer may be started again from the time when the logged measurement configuration is newly received. Furthermore, logged measurements based on a prior logged measurement configuration may be discarded.

FIG. 16 is a diagram illustrating an example of an immediate MDT. The immediate MDT is based on a Radio Resource Management (RRM) measurement and report mechanism. In addition, information related to a location is added when a measured report is made and reported to an eNB.

Referring to FIG. 16, UE receives an RRC connection reconfiguration message (S1610) and sends an RRC connection reconfiguration-complete message (S1620). Accordingly, the UE enters an RRC connected state. The UE may receive a measurement configuration by receiving the RRC connection reconfiguration message. In the example of FIG. 16, the measurement configuration is received through the RRC connection reconfiguration message, but may be included in an RRC message according to an example and transmitted.

The UE performs measurements and evaluations in the RRC connected state (S1631) and reports a measured result to an eNB (S1632). In an immediate MDT, the measured result may provide accurate location information, if possible, as in an example of Global Navigation Satellite System (GNSS) location information. For location measurement, such as an RF fingerprint, neighbor cell measurement information that may be used to determine the location of the UE may be provided.

From FIG. 16, it may be seen that even after the prior measurements and evaluations (S1631) and report (S1632), the UE reports a measured result to the eNB (S1642) right after performing measurements and evaluations (S1641). This may be said to be the greatest difference between a logged MDT and an immediate MDT.

A Multimedia Broadcast and Multicast Service (MBMS) is described in detail below.

A logical channel MCCH channel or MTCH channel may be mapped to a transport channel MCH channel for the MBMS. The MCCH channel sends an MBMS-related RRC message, and the MTCH channel sends traffic of a specific MBMS service. A single MCCH channel is present in each MBMS Single Frequency Network (MBSFN) area in which the same MBMS information/traffic is transmitted. If a single cell provides a plurality of MBSFN areas, UE may receive a plurality of MCCH channels. If an MBMS-related RRC message is changed in a specific MCCH channel, a PDCCH channel sends an indicator indicative of an MBMS Radio Network Temporary Identity (M-RNTI) and a specific MCCH channel. UE supporting the MBMS may receive the M-RNTI and the MCCH indicator through the PDCCH channel, may check that the MBMS-related RRC message has been changed in a specific MCCH channel, and may receive the specific MCCH channel. The RRC message of the MCCH channel may be changed for each change cycle and repeatedly broadcasted for each repetition cycle.

UE may also be provided with a dedicated service while it is provided with an MBMS service. For example, a user may watch TV through an MBMS service through his or her smart phone and simultaneously perform chatting using an Instant Messaging (IM) service, such as MSN or Skype, using the smart phone. In this case, the MBMS service is provided through an MTCH received by several UE, and a service provided to each UE, such as an IM service, may be provided through a dedicated bearer, such as a DCCH or DTCH.

In one area, a specific eNB may use several frequencies at the same time. In this case, in order to efficiently use radio resources, a network may select one of the several frequencies, may provide an MBMS service only the selected frequency, and may provide dedicated bearers to respective UEs in all the frequencies.

In this case, if UE provided with a service using a dedicated bearer in a frequency through which the MBMS service is not provided wants to receive the MBMS service, the UE need to perform handover to the frequency through which the MBMS service is provided. To this end, the UE sends an MBMS interest indication to an eNB. That is, if the UE wants to receive the MBMS service, it sends an MBMS interest indication to the eNB. When the indication is received, the eNB recognizes that the UE wants to receive the MBMS service and moves the UE to the frequency through which the MBMS service is provided. In this case, the MBMS interest indication means information indicating that the UE wants to receive the MBMS service and additionally includes information about a frequency to which the UE wants to move.

UE that wants to receive a specific MBMS service first checks frequency information and broadcasting time information through which the specific MBMS service is provided. If the MBMS service is already broadcasted or starts to be broadcasted, the UE sets the highest priority in a frequency through which the MBMS service is provided. The UE moves to a cell that provides the MBMS service by performing a cell reselection procedure using the reconfigured frequency priority information, and receives the MBMS service.

If UE receives an MBMS service or is interested to receiving an MBMS service and if UE is able to receive an MBMS service while it camps on a frequency through which the MBMS service is provided, the highest priority may be considered to have been applied to the corresponding frequency during an MBMS session as long as the following situation continues in the state in which a reselected cell broadcasts SIB13.

• • If the inclusion of one or more MBMS Service Area Identities (SAIs) in the User Service Description (USD) of a corresponding service is indicated by SIB15 of a serving cell.
  • If SIB 15 is not broadcasted within a serving cell and a corresponding frequency is included in the USD of a corresponding service.

The aforementioned MDT may be applied in relation to an MBMS. A network may enable specific UE to report information related to an MBMS to the network. A series of procedures, including a corresponding configuration from a network and/or an UE MBMS information reporting operation, may be implemented as in the aforementioned MDT, which may be called an MBMS MDT.

A network may select UE for an MBMS MDT based on the capabilities of the UE and/or the consent of a user. However, an MBMS service is broadcasted and provided on an MBSFN area, and UE provided with the MBMS service does not provide corresponding feedback. Accordingly, the network rarely checks the MBMS reception status of the UE. Accordingly, the network may perform a configuration in UE so that MBMS MDT management is performed regardless of the MBMS reception status of the UE.

When UE measures MBMS transmission related to an MBMS service that is not interested, the UE consumes power for the purpose of the reporting of MBMS information. If the reporting of MBMS information depends on the improvement of MBMS service reception from a viewpoint of a user, excessive consumption of UE-side power attributable to the improvement may not be preferred. Accordingly, a method capable of improving MBMS service reception for UE while preventing excessive consumption of UE-side power needs to be proposed.

FIG. 17 is a diagram illustrating a method for reporting MBMS information in accordance with an embodiment of the present invention.

Referring to FIG. 17, UE receives an MBMS reporting configuration from a network (S1710). The MBMS reporting configuration may include configuration information for obtaining, logging, and reporting information related to the MBMS service reception of the UE. The configuration information set in the UE through the MBMS reporting configuration may be implemented as follows.

(1) The MBMS reporting configuration may include MBMS logging execution information. The MBMS logging execution information may be information specifying that the UE will obtain and log MBMS information when and how. The MBMS logging execution information may include the following lower information.

• • A logging execution condition: the logging execution condition specifies a condition in which UE determines to execute the acquisition and logging of MSBM information. The UE may determine to execute the acquisition and logging of MSBM information depending on the logging execution condition. Furthermore, the UE may determine to stop the acquisition and logging of MSBM information depending on the logging execution condition. The following conditions may be taken into consideration as the logging execution condition.

a) An MSBM service reception failure

b) The deterioration of MSBM service reception quality

c) The failure of a measured result of an MSBM service-specific reference signal

If the logging execution condition is included in MBMS logging execution information, UE may determine whether or not to execute MBMS logging by applying the logging execution condition.

• • Logging duration: the logging duration indicates duration in which UE that has determined to perform the acquisition/logging of MBMS information obtains and logs the MBMS information. A point of time at which logging duration starts may be a point of time at which an MBMS reporting configuration is received or a point of time at which the acquisition/logging of MBMS information are first started.
  • A logging interval: the logging interval indicates a time interval in which UE performs the acquisition/logging of MBMS information during logging duration. If information indicative of a logging interval is included in MBMS logging execution information, UE may periodically perform the acquisition/logging of MBMS information at the logging interval during logging duration.

(2) An MBMS reporting configuration may include MBMS logging purpose information. The MBMS logging purpose information may indicate that an operation according to an MBMS reporting configuration is for MBMS information reporting. That is, the MBMS logging purpose information may indicate that the operation according to the MBMS reporting configuration is for an MBMS MDT.

A reporting configuration transmitted to UE may include MBMS logging purpose information indicative of an object of logging. The MBMS logging purpose information may indicate the report of MBMS information by UE. The logging purpose information may indicate an MBMS MDT.

(3) An MBMS reporting configuration may include MBMS logging area information indicative of an area in which the acquisition and logging of MBMS information by UE is permitted. The MBMS logging area information may include the following information.

• • An MBSFN area: an MBSFN area in which the acquisition and logging of MBMS information by UE is permitted
  • A PLMN list: a PLMN identity set in which the acquisition and logging of MBMS information by UE is permitted

(4) An MBMS reporting configuration may include MBMS logging target information specifying MBMS information to be obtained and logged by UE. The MBMS logging target information may specify the content of MBMS information to be obtained by UE through measurements.

(5) An MBMS reporting configuration may include MBMS reporting condition information indicative of a reporting condition on logged MBMS information. The MBMS reporting condition information may specify that logged MBMS information is to be reported when, where and/or how. The MBMS reporting condition may include the following information.

• • A reporting cycle: The reporting cycle of logged MBMS information
  • A reporting event: an event that triggers the reporting of logged MBMS information (e.g., an MBMS service failure, MBMS service deterioration, and an RRC connected state)
  • A reporting method: The reporting of MSBM information indicates whether one or more pieces of MSBM information, such as a logged MDT, are logged and reported once or are immediately reported right when the MSBM information is obtained.

(6) An MBMS reporting configuration may further include a trace parameter. The trace parameter may include at least one of a trace reference parameter, a trace recording session reference, and a TCE ID.

An MBMS reporting configuration may be provided to UE through broadcast signaling (e.g., signaling through a BCCH and/or an MCCH). UE may receive an MBMS reporting configuration provided through broadcast signaling and determine whether there is user consent for reporting MBMS information according to the MBMS reporting configuration. If there is user consent, the UE may determine to apply the MBMS reporting configuration. If there is no user consent, the UE disregards the received MBMS reporting configuration. In this case, the user consent for performing MBMS information reporting may be previously set in the UE or may be set by an application using Open Mobile Alliance (OMA) Device Management (DM), for example.

An MBMS reporting configuration may be provided to UE through dedicated signaling (e.g., signaling through a DCCH). An RRC message for an MBMS reporting configuration may be newly defined. Alternatively, an MBMS reporting configuration may be additionally included in an existing RRC message. For example, an MBMS reporting configuration may be additionally included in a logged measurement configuration message. If a logged measurement configuration is used through a logged measurement configuration message, the logged measurement configuration message may need to indicate whether UE needs to perform MBMS information reports. To this end, the aforementioned MBMS logging purpose information may be included in the logged measurement configuration message. Meanwhile, if a logged measurement configuration message is used for only MBMS information reporting, the logged measurement configuration message may further include information indicating that measurement logging for a logged MDT must be omitted.

The UE determines whether or not to execute the logging of the MBMS information (S1720). The determination of whether or not to execute the logging of the MBMS information by the UE may be based on a logging execution condition configured in the UE. The logging execution condition to be applied by the UE, as described above, may be included in an MBMS reporting configuration and configured in the UE or may have been previously configured in the UE. The UE may determine whether the logging execution condition is satisfied and determine whether or not to execute the logging of the MBMS information.

(1) Determine whether or not to execute the logging of the MBMS information depending on an MBMS service reception failure

The UE detects that an MBMS service reception failure has occurred and thus may determine to obtain and log the MBMS information. The occurrence of the MBMS service reception failure may be taken into consideration as follows.

a) If the UE does not obtain an MCCH from the cell of a frequency provided by an interested MBMS service, the UE may determine that the MBMS service reception failure has been detected.

b) If the UE has failed in obtaining SIB13 (if the UE has failed in obtaining the configuration of an MCCH), the UE may determine the MBMS service reception failure has been detected.

c) If the UE has failed in obtaining SIB15S, the UE may determine that the MBMS service reception failure has been detected.

d) Whether the UE will detect the occurrence of the MBMS service reception failure by applying which one of the aforementioned MBMS service reception failure determination criteria may be previously set in the UE or may be configured in the UE through the explicit signaling of a network.

If the UE determines that the MBMS service reception failure has been solved, the UE may determine to stop the acquisition and logging of the MBMS information. The solving of the MBMS service reception failure may be configured contrary to the aforementioned determination criteria.

(2) Determine whether or not to execute the logging of the MBMS information depending on the deterioration of MBMS service reception quality

The UE detects the deterioration of MBMS service reception quality and thus may determine to obtain and log the MBMS information. The occurrence of the deterioration of the MBMS service reception quality may be taken into consideration as follows.

a) If the block error rate (BLER) of a received MBMS service is higher than a specific threshold, the UE may determine that the deterioration of the MBMS service reception quality has been detected.

b) The BLER may be the CRC failure rate of transmission that includes an MBMS service and that is received by the UE in a subframe on a PMCH and/or an MTCH.

c) The BLER may be measured or evaluated as a BLER per MCS.

d) The BLER may be defined as an average BLER during a moving time window.

If the UE determines that the deterioration of the MBMS service reception quality has been solved, the UE may determine to stop the acquisition and logging of the MBMS information. The solving of the deterioration of the MBMS service reception quality may be configured contrary to the aforementioned determination criteria.

(3) Determine whether or not to execute the logging of the MBMS information depending on the failure of a measurement result of an MBMS service-specific reference signal

The UE detects that a measurement result of an MBMS service-specific reference signal is poor and thus may determine to obtain and log the MBMS information. The occurrence of the failure of a measurement result of the MBMS service-specific reference signal may be taken into consideration as follows.

a) If the measurement result of the MBMS service-specific reference signal is lower than a specific threshold, the UE may determine that it has detected that measurement result of the MBMS service-specific reference signal is poor.

b) The measurement result of the MBMS service-specific reference signal may be measured and evaluated in such a manner that the UE measures a subframe on a PMCH or an MTCH that includes an MBMS service. The MBMS service-specific reference signal may be a reference signal transmitted on an MBSFN subframe provided by the MBMS service.

c) The measurement result may be the signal intensity of the reference signal and/or signal quality.

d) The measurement result may be defined as an average value during a moving time window.

If the UE determines that the failure of the measurement result of the MBMS service-specific reference signal has been solved, the UE may determine to stop the acquisition and logging of the MBMS information. The solving of the failure of the measurement result may be configured contrary to the aforementioned determination criteria.

One or more of the aforementioned criteria for determining whether or not to execute the acquisition and logging of the MBMS information may be combined and implemented. For example, one or more logging execution criteria may be included in MBMS logging execution information so that UE determines whether or not to execute the acquisition and logging of the MBMS information by taking the one or more logging execution criteria into consideration.

The UE executes the acquisition and logging of the MBMS information (S1730). The UE may perform MBMS measurements in order to obtain the MBMS information. The UE may perform MBMS measurements on a frequency and/or subframe provided by the MBMS service and may obtain a measurement result. The UE may include the measurement result of the MBMS service in the MBMS information. The UE may include information about the location of the UE in the MBMS information when obtaining and logging the MBMS information.

The acquisition and logging of the MBMS information by the UE may be periodically performed when the logging execution condition is satisfied. To this end, an MBMS logging cycle may be set in the UE. The MBMS logging cycle may be configured in the UE through the logging interval of MBMS logging execution information of an MBMS reporting configuration. The UE may obtain MBMS information at a logging point of time based on the MBMS logging cycle and may log the MBMS information. In order to periodically log the MBMS information, a timer may be set. The timer may be set as an MBMS logging cycle value. When the timer expires, it is restarted. The UE may obtain and log MBMS information when the timer expires.

The logging of the periodic MBMS information by the UE may be performed for duration in which a logging execution condition is satisfied. If the logging execution condition is no longer satisfied, the UE may stop the acquisition and logging of the MBMS information. If the logging execution condition continues to be satisfied, the logging of the periodic MBMS information by the UE may be performed for the logging duration. If the logging duration expires, the logging of the periodic MBMS information may be stopped.

Unlike in the logging of periodic MBMS information, the UE may obtain and log MBMS information depending on the satisfaction/dissatisfaction of the logging execution condition. That is, the UE may obtain and log the MBMS information when the logging execution condition is satisfied and may obtain and log MBMS information again when the logging execution condition that has been satisfied is no longer satisfied.

Whether the UE will obtain and log the MBMS information based on which one of the two methods may be determined by the configuration of a network. For example, separate information indicative of a method of obtaining and logging MBMS information by the UE may be provided by a network. For another example, if logging interval information is not included in an MBMS reporting configuration, the UE may log MBMS information when a logging execution condition is satisfied and is no longer satisfied. In contrast, if logging interval information is included in an MBMS reporting configuration, the UE may periodically log MBMS information for an interval in which a logging execution condition is satisfied. If information indicative of a method of obtaining and logging MBMS information is included in an MBMS reporting configuration, the UE may perform the acquisition and logging of MBMS information according to an instructed method.

Alternatively, whether the UE will obtain and log the MBMS information based on which one of the two methods may have been previously configured in the UE.

The MBMS information obtained and logged by the UE may include the following information. If obtained MBMS information is logged and reported to a network at once without immediately reporting the obtained MBMS information, a piece of the logged MBMS information may be stored as a single logged entry.

(1) MBMS control information

• • MBMS service area information about the interest MBMS service of UE or an MBMS service being received by the UE (e.g., MBMS SAD
  • MBSFN area information about the interest MBMS service of UE or an MBMS service being received by the UE (MBSFN area identity)
  • PMCH information related to each MBSFN area of the interest MBMS service of UE or an MBMS service being received by the UE
  • A Temporary Mobile Group Identity (TMGI) for the interest MBMS service of UE or an MBMS service being received by the UE
  • MBSFN subframe information (MBSFN-SubframeConfig)

(2) MBMS cell information

• • An MBMS cell means a cell which provides the interest MBMS service of UE on the frequency of the corresponding cell. The MBMS cell may have a different meaning from a serving cell on another frequency.
  • The MBMS cell information may include an MBMS cell ID list. If a serving cell is different from an MBMS cell, the ID of a corresponding cell may be logged. If the frequency of a serving cell is different from the frequency of an MBMS cell, the ID of a corresponding cell may be logged.
  • The MBMS cell information may include an frequency list of an MBMS cell which provides the interest MBMS service of UE or an MBMS service being received by the UE.
  • The MBMS cell information may include the PLMN of an MBMS cell. The PLMN of an MBMS cell may be included in MBMS cell information if the PLNM of a corresponding MBMS cell is different from the rPLMN of UE.
  • An indicator indicating that UE currently camps on an MBMS frequency or indicating whether the MBMS frequency is the same as the frequency of a serving cell with which the UE has established RRC connection may be included in the MBMS cell information.

(3) Logging reason information

• • The logging reason information may be indicative of the logging reason of MBMS information logged by UE. The logging reason information may indicate that the logged MBMS information is based on periodic logging. The logging reason information may indicate whether the logged MBMS information is based on specific event-based logging, such as a logging execution condition. The logging reason information may be included in each log entry as unit MBMS information logged at a specific point of time and may be configured to indicate a reason for which the corresponding log entry has been logged. The logging reason information may be configured to indicate a reason for which all pieces of MBMS information logged at a plurality of points of time, that is, a plurality of log entries has been logged.

(4) MBMS service deterioration/failure reason information

• • The MBMS service deterioration/failure reason information may be indicative of an MBMS service failure. An MCCH acquisition failure, an MBMS service reception failure from a cell on a frequency for the interest MBMS service of UE, an SIB 13 acquisition failure (MCCH configuration acquisition failure), an SIB 15 acquisition failure, entry into a cell that does not provide an MBMS service (e.g., entry into a CSG cell/cell in which an MBSFN subframe has not been configured/irregular cell/invalid cell/entry into a cell of a PLMN other than an rPLMN), and deviation from a regular camp state may be taken into consideration as the MBMS service failure.
  • The MBMS service deterioration/failure reason information may be indicative of the deterioration of MBMS service reception quality. The MBMS service deterioration/failure reason information may be indicative of a reason that has caused the deterioration of MBMS service reception quality.

(5) MBMS service reception quality of information

• • A Block Error Rate (BLER) per Modulation and Coding Scheme (MCS)
  • A BLER per MCS in each MBSFN area
  • If an MBMS-specific reference signal is to be measured, a measured result (RSRP, RSRQ) of a serving cell

(6) MBMS transmission information

• • An MCS applied to an MCCH
  • An MCS applied to a PMCH

(7) Wireless measurements information

• • Serving cell information (a PCI, a GCI, a serving frequency, a tracking area, a PLMN list, etc.)
  • If a common reference signal has been measured, a measured result (RSRP, RSRQ) of a serving cell
  • Neighbor cell information (a PCI, a neighbor cell frequency)
  • A measured result (RSRP, RSRQ) of a neighbor cell

(8) Time information

• • Logging time information (e.g., SS:MM:HH:DD)
  • Service deterioration time
  • A point of time at which the deterioration of service quality occurred
  • A point of time at which the deterioration of service quality was previously generated
  • Service deterioration the duration
  • An MBMS service deterioration occurrence indicator
  • An indicator per log entry

(9) Information about the location of UE at a point of time at which MBMS information is logged (e.g., GPS, GNSS-based location information)

The MBMS information that may be logged by the UE may be obtained and/or determined from a serving cell and/or a non-serving cell.

The UE reports the logged MBMS information to the network (S1740).

To report, by the UE, the logged MBMS information to the network may be performed as in an existing logged MDT. The UE may include a logged MBMS information availability indicator, indicating that there is logged MBMS information to be reported, in an RRC connection establishment-complete message, an RRC connection reconfiguration-complete message, or an RRC connection re-establishment-complete message, and send the message.

When the reporting of the logged MBMS information is requested by the network, the UE may report the logged MBMS information to the network at a specific report time interval during an RRC connected state. The specific report time interval may be set by the network.

The reporting of logged MBMS information by UE may be performed with respect to a network after MBMS measurements are obtained and/or right after the logged MBMS information is obtained. UE may immediately report MBMS information to a network without a request for the report by the network. In accordance with the method of immediately reporting MBMS information as described above, a logging execution condition may be taken into consideration as a condition in which the acquisition and reporting of the MBMS information are triggered. UE in a logging RRC connected state may report MBMS information to a network right after the MBMS information is obtained. UE in an RRC connected state may include MBMS information in an RRC connection establishment-complete message, RRC connection re-establishment-complete message, or a separate RRC message after the RRC connected state is established and send the message to a network.

How UE will report MBMS information may be performed depending on a reporting method previously configured in the UE. Alternatively, if information indicative of a reporting method is included in an MBMS reporting configuration, UE may report MBMS information depending on reporting method indication information included in the MBMS reporting configuration.

A detailed example of a method of reporting MBMS information in accordance with an embodiment of the present invention is described in detail with reference to a figure.

FIG. 18 is a diagram illustrating an example of a method of reporting MBMS information in accordance with an embodiment of the present invention.

Referring to FIG. 18, an LTE cell is assumed to be an MBMS cell providing UE with an interested MBMS service.

The UE receives an MBMS reporting configuration from the LTE cell (S1810). The MBMS reporting configuration may include a logging execution condition, logging duration T_D, and a logging interval T₁ as MBMS logging execution information. The logging execution condition may indicate an MBMS service reception failure.

The LTE cell is an MBMS cell which provides the UE with an interested MBMS service, and thus the UE may receive an MBMS service from the LTE cell. While the UE receives the MBMS service, the reception failure of the MBMS service may occur (S1821). In this case, the UE determines to start the logging of MBMS information and logs related MBMS information (S1822). The UE performs MBMS measurements in order to obtain the MBMS information. The UE may perform wireless measurements on a frequency and/or subframe provided by the MBMS service. The UE may include a measurement result in the MBMS information. Furthermore, the UE may include location information indicative of the location of the UE in the MBMS information at a point of time at which the MBMS information is obtained and logged.

Furthermore, the UE may include logging reason information indicative of a reason for which the MBMS information has been obtained/logged in the MBMS information. The logging reason information may indicate that the MBMS information is information logged based on an event, such as a logging execution condition. The MBMS information may include MBMS service failure reason information. The MBMS service failure reason information may be indicative of an MBMS service reception failure. Furthermore, the MBMS service failure reason information may be indicative of a detailed reason (e.g., an MCCH acquisition failure or an SIB13 acquisition failure) for which the MBMS service reception failure has occurred. The MBMS information may include logging time information indicative of a point of time at which the MBMS information has been logged. Furthermore, the MBMS information may further include pieces of lower information that may be included in the MBMS information described above with reference to FIG. 17. The MBMS information obtained and logged at step S1822 may be stored as a single log entry.

If the reception failure of the MBMS service continues to occur (S1831, S1841, S1851), the UE may periodically obtain and log MBMS information at the specific logging interval T₁ within the logging duration T_D (S1832, S1842, S1852). At each point of time, the UE performs MBMS measurements in order to obtain the MBMS information. The UE may perform wireless measurements on a frequency and/or subframe provided by an MBMS service. The UE may include a measurement result in the MBMS information. Furthermore, the UE may include location information indicative of the location of the UE in the MBMS information at a point of time at which the MBMS information is obtained and logged.

Furthermore, the UE may include logging reason information indicative of a reason for which the MBMS information has been obtained/logged in the MBMS information. The logging reason information may indicate that the obtained and logged MBMS information has been logged based on periodic logging. Logging time information indicative of a point of time at which corresponding MBMS information has been logged may be include in each of pieces of MBMS information. Furthermore, each piece of MBMS information may further include pieces of lower information that may be included in the MBMS information described with reference to FIG. 17. MBMS information obtained and logged at each step may be stored as a single log entry.

When the logging duration T_D expires, the UE determines to stop the acquisition and logging of the MBMS information (S1860). The UE may drive a timer in order to manage duration in which MBMS information is obtained and logged. The timer may be set as the logging duration T_D.

The UE that has stopped the acquisition and logging of the MBMS information may report the logged MBMS information to the network. To this end, the UE may send a logged MBMS information availability indicator to the network in order to notify the network that the logged MBMS information is present (S1871). The logged MBMS information availability indicator may be included in an RRC message and transmitted. The logged MBMS information availability indicator may be included in an RRC connection establishment-complete message, an RRC connection reconfiguration-complete message, an RRC connection re-establishment-complete message, or an UE information message and transmitted to the network. In this figure, the logged MBMS information availability indicator has been illustrated as being transmitted to the LTE cell. If the UE uses another cell as a serving cell, the UE may send the logged MBMS information availability indicator to the corresponding serving cell.

The LTE cell or another serving cell that has received the logged MBMS information availability indicator may send a logged MBMS information reporting request that requests the reporting of the logged MBMS information to the UE (S1872). Thereafter, the UE may send the logged MBMS information to the LTE cell or another serving cell in response to the MBMS information reporting request (S1873).

In the example shown in FIG. 18, the acquisition and logging of the MBMS information by the UE has been performed for the logging duration T_D. In this case, it is assumed that the UE has continuously failed in receiving an MBMS service for the logging duration T_D. If the UE normally receives the MBMS service before the logging duration T_D expires, the satisfaction of the logging execution condition is released. Accordingly, the UE may obtain and log corresponding MBMS information and may determine to stop the acquisition and logging of the MBMS information. The MBMS information of a log entry logged at this point of time may include logging reason information. The logging reason information may indicate that the logged MBMS information is information logged based on an event, such as a logging execution condition. The MBMS information may include MBMS service failure reason information. The MBMS service failure reason information may be indicative of the recovery of an MBMS service reception failure. Furthermore, the MBMS service failure reason information may be indicative of a detailed reason (e.g., a success in obtaining an MCCH or a success in obtaining SIB13) for which the MBMS service reception failure has been recovered. The MBMS information may include information indicative of a point of time at which the MBMS information has been logged and/or information indicative of the time for which the MBMS service failure has continued. Furthermore, the MBMS information may further include pieces of lower information that may be included in the MBMS information described above with reference to FIG. 17.

In FIG. 18, the UE has stored the obtained and logged MBMS information and reported a plurality of log entries to the network at once. However, a method of reporting, by the UE, MBMS information is not limited to the method, and the UE may immediately report the MBMS information to the network when it obtains the MBMS information. In the example of FIG. 18, the UE may obtain MBMS information at each of steps S1832, S1842, and S1851 and may immediately report the obtained MBMS information to the network.

In the example of FIG. 18, the logging of the MBMS information by the UE may be performed depending on the deterioration of MBMS service reception quality unlike in the case where the logging of the MBMS information is performed depending on the MBMS service reception failure. Furthermore, unlike in the case where the acquisition and logging of the MBMS information are periodically performed by the UE, the acquisition and logging of the MBMS information may be performed based on an event related to a logging execution condition. Such an example is described with reference to FIG. 19.

FIG. 19 is a diagram illustrating another example of a method of reporting MBMS information in accordance with an embodiment of the present invention.

Referring to FIG. 19, an LTE cell is assumed to be an MBMS cell which provides UE with an interested MBMS service.

The UE receives an MBMS reporting configuration from the LTE cell (S1910). The MBMS reporting configuration may include a logging execution condition as MBMS logging execution information. The logging execution condition may be indicative of the deterioration of MBMS service reception quality. In order to determine whether the deterioration of the MBMS service reception quality has occurred, a reception quality threshold may be set. The reception quality threshold may be previously set in the UE or may be set in the UE through an MBMS reporting configuration.

The LTE cell is an MBMS cell which provides the UE with an interest MBMS service, and thus the UE may receive the MBMS service from the LTE cell (S1920).

While the UE receives the MBMS service from the MBMS cell, it may detect the deterioration of MBMS service reception quality (S1931). In this case, the UE determines to log MBMS information and logs related MBMS information (S1932). The UE performs MBMS measurements in order to obtain the MBMS information. The UE may perform wireless measurements on a frequency and/or subframe provided by the MBMS service. The UE may include a measurement result in the MBMS information. Furthermore, the UE may include location information indicative of the location of the UE in the MBMS information at a point of time at which the MBMS information is obtained and logged.

Furthermore, the UE may include logging reason information indicative of a reason for which the MBMS information has been obtained/logged in the MBMS information. The logging reason information may indicate that the MBMS information is information logged based on an event, such as a logging execution condition. The MBMS information may include MBMS service deterioration reason information. The MBMS service deterioration reason information may be indicative of the deterioration of MBMS service reception quality. Furthermore, the MBMS service deterioration reason information may be indicative of a detailed reason for which the deterioration of the MBMS service reception quality has occurred. The MBMS information may include logging time information indicative of a point of time at which the MBMS information has been logged. Furthermore, the MBMS information may further include pieces of lower information that may be included in the MBMS information described above with reference to FIG. 17. The MBMS information obtained and logged at step S1932 may be stored as a single log entry.

The UE performs the acquisition and logging of MBMS information based on an event related to a logging execution condition. Accordingly, the UE may obtain and log (S1932) MBMS information when the deterioration of MBMS service reception quality occurs (S1931) and may not log MBMS information unless the satisfaction and/or release of the logging execution condition is generated (if the deterioration of the MBMS service reception quality is not recovered).

The UE receives MBMS service of normal quality from the MBMS cell and may detect that the deterioration of the MBMS service reception quality has been solved (S1941). In this case, the UE determines to stop the logging of the MBMS information and logs related MBMS information (S1942). The UE performs MBMS measurements in order to obtain the MBMS information. The UE may perform wireless measurements on a frequency and/or subframe provided by the MBMS service. The UE may include a measurement result in the MBMS information. Furthermore, the UE may include location information indicative of the location of the UE in the MBMS information at a point of time at which the MBMS information is obtained and logged.

Furthermore, the UE may include logging reason information indicative of a reason for which the MBMS information has been obtained/logged in the MBMS information. The logging reason information may indicate that the MBMS information is information logged based on an event, such as a logging execution condition. The MBMS information may include MBMS service deterioration reason information. The MBMS service deterioration reason information may indicate that the deterioration of MBMS service reception quality has been solved. The log entry may include information indicative of a point of time at which the MBMS information has been logged and/or information indicative of the time for which the deterioration of the MBMS service reception quality has continued. Furthermore, the MBMS information may further include pieces of lower information that may be included in the MBMS information described above with reference to FIG. 17. The MBMS information obtained and logged at step S1932 may be stored as a single log entry.

The UE that has determined to stop the acquisition and logging of the MBMS information may report the logged MBMS information to the network. To this end, the UE may send a logged MBMS information availability indicator to the network in order to notify the network that the logged MBMS information is present (S1951). The logged MBMS information availability indicator may be included in an RRC message and transmitted. The logged MBMS information availability indicator may be included in an RRC connection establishment-complete message, an RRC connection reconfiguration-complete message, an RRC connection re-establishment-complete message, or an UE information message and transmitted to the network. In this figure, the logged MBMS information availability indicator has been illustrated as being transmitted to the LTE cell. If the UE uses another cell as a serving cell, the UE may send the logged MBMS information availability indicator to the corresponding serving cell.

The LTE cell or another serving cell that has received the logged MBMS information availability indicator may send a logged MBMS information reporting request that requests the reporting of the logged MBMS information to the UE (S1952). Thereafter, the UE may send the logged MBMS information to the LTE cell or another serving cell in response to the MBMS information reporting request (S1953).

In the example shown in FIG. 19, the execution of the acquisition and logging of the MBMS information by the UE has been stopped when the satisfaction of the logging execution condition is released (S1941), but may not be limited thereto. If logging duration T_D has been set in the MBMS reporting configuration, the UE may obtain and log MBMS information for the logging duration. In the example of FIG. 19, if logging duration has been set, if the deterioration of MBMS service reception quality has not been solved within the logging duration, the UE may determine to stop the logging of MBMS information when the logging duration expires.

In FIG. 19, the UE has stored obtained and logged MBMS information and reported a plurality of log entries to the network. However, a method of reporting, by the UE, MBMS information is not limited thereto. The UE may immediately report MBMS information to the network when it obtains the MBMS information. In the example of FIG. 19, the UE may obtain MBMS information at each of steps S1932 and S1942 and immediately send the obtained MBMS information to the network.

In accordance with the method of reporting MBMS information according to an embodiment of the present invention, UE configured to report MBMS information may obtain and log the MBMS information depending on the reception status or reception quality of an MBMS service. Accordingly, a problem in which unnecessary power is consumed because UE obtains and logs MBMS information in the situation in which an MBMS service not related to the UE is provided or the UE is not provided with an MBMS service can be prevented. Furthermore, signaling overhead can be reduced and use efficiency of radio resources can be improved because unnecessary signaling for the MBMS information reporting of UE can be prevented.

FIG. 20 is a block diagram illustrating a wireless device in which an embodiment of the present invention is implemented. The device may be implemented using UE or a network system for performing a method in accordance with an embodiment of the present invention.

Referring to FIG. 20, the wireless device 2000 includes a processor 2010, memory 2020, and a Radio Frequency (RF) unit 2030. The processor 2010 implements the proposed functions, processes and/or methods. The processor 2010 may be configured to generate and provide an MBMS reporting configuration for the acquisition/logging and reporting of MBMS information. The processor 2010 may be configured to perform the acquisition/logging and reporting of MBMS service information. The processor 2010 may be configured to perform the embodiments of the present invention described with reference to FIGS. 17 to 19.

The RF unit 2030 is connected to the processor 2010, and sends and receives radio signals.

The processor may include Application-Specific Integrated Circuits (ASICs), other chipsets, logic circuits, and/or data processors. The memory may include Read-Only Memory (ROM), Random Access Memory (RAM), flash memory, memory cards, storage media and/or other storage devices. The RF unit may include baseband circuits for processing radio signals. When the embodiment is implemented in software, the aforementioned scheme may be implemented as a module (process or function) that performs the aforementioned function. The module may be stored in the memory and executed by the processor. The memory may be placed inside or outside the processor and may be connected to the processor using a variety of well-known means.

In the above exemplary systems, although the methods have been described on the basis of the flowcharts using a series of the steps or blocks, the present invention is not limited to the sequence of the steps, and some of the steps may be performed at different sequences from the remaining steps or may be performed simultaneously with the remaining steps. Furthermore, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive and may include other steps or one or more steps of the flowcharts may be deleted without affecting the scope of the present invention.

Claims

1. A method of reporting, by user equipment, Multimedia Broadcast and Multicast Service (MBMS) information in a wireless communication system, the method comprising:

determining whether or not to execute a logging of the MBMS information;

logging the MBMS information if the logging is determined to be performed; and

reporting the logged MBMS information to a network,

wherein whether or not to execute the logging of the MBMS information is determined based on an MBMS information logging execution condition, and

the MBMS information logging execution condition comprises at least one of a reception failure of an MBMS service and reception quality of the MBMS service provided by the network.

2. The method of claim 1, wherein determining whether or not to execute the logging of the MBMS information comprises determining to execute the logging if the MBMS information logging execution condition is satisfied.

3. The method of claim 2, further comprising:

determining whether or not to stop the execution of the logging of the MBMS information.

4. The method of claim 2, wherein determining whether or not to stop the execution of the logging of the MBMS information comprises determining to stop the execution of the logging if the MBMS information logging execution condition that has been satisfied is released.

5. The method of claim 4, wherein logging the MBMS information comprises:

logging a first MBMS log entry if the MBMS information logging execution condition is satisfied; and

logging a second MBMS log entry if the MBMS information logging execution condition is not satisfied,

wherein the logged MBMS information comprises the first MBMS log entry and the second MBMS log entry.

6. The method of claim 5, wherein the first MBMS log entry comprises information indicating that the first MBMS log entry has been logged because the MBMS information logging execution condition has been satisfied.

7. The method of claim 6, wherein the second MBMS log entry comprises information indicating that the second MBMS log entry has been logged because the satisfaction of the MBMS information logging execution condition has been released.

8. The method of claim 5, wherein logging the MBMS information comprises periodically logging third MBMS log entries until the satisfaction of the MBMS information logging execution condition is released after the MBMS information logging execution condition is satisfied, wherein the logged MBMS information further comprises the third MBMS log entries.

9. The method of claim 8, wherein each of the third MBMS log entries comprises information indicating that a corresponding third MBMS log entry has been periodically logged.

10. The method of claim 1, further comprising receiving an MBMS reporting configuration comprising configuration information for the logging and reporting of the MBMS information by the user equipment from the network, wherein the MBMS reporting configuration comprises MBMS logging execution information which specifies the MBMS information logging execution condition.

11. The method of claim 1, wherein reporting the logged MBMS information to the network comprises:

sending a logged MBMS information availability indicator indicating that the logged MBMS information to be reported to the network is present to the network;

receiving a logged MBMS information reporting request which requests the reporting of the logged MBMS information from the network; and

sending a logged MBMS information report comprising the logged MBMS information to the network in response to the logged MBMS information reporting request.

12. The method of claim 1, wherein reporting the logged MBMS information to the network comprises immediately sending the logged MBMS information to the network in response to the logging of the MBMS information.

13. A wireless device operating in a wireless communication system, the wireless device comprising:

a Radio Frequency (RF) unit which sends and receives radio signals; and

a processor which is functionally coupled to the RF unit and operates, wherein the processor is configured to:

determine whether or not to execute a logging of the MBMS information;

log the MBMS information if the logging is determined to be performed; and

report the logged MBMS information to a network,

wherein whether or not to execute the logging of the MBMS information is determined based on an MBMS information logging execution condition, and

the MBMS information logging execution condition comprises at least one of a reception failure of an MBMS service and reception quality of the MBMS service provided by the network.