Measurement mechanism to reduce power consumption and method for providing service contiunity in handover in mobile communications system

MEASUREMENT MECHANISM TO REDUCE POWER CONSUMPTION AND METHOD FOR PROVIDING SERVICE CONTIUNITY IN HANDOVER IN MOBILE COMMUNICATIONS SYSTEM

The present invention relates to an Evolved Universal Mobile Telecommunications System (E-UMTS) in wireless communication, and more particularly, to a method for mobility of a terminal for improving system service quality, and a method for reducing power consumption for movement of a terminal.

1 is a diagram illustrating a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS), which is a mobile communication system to which the prior art and the present invention are applied. The E-UMTS system is an evolved system from the existing UMTS system, and basic standardization work is currently underway in 3GPP. The E-UMTS system may be referred to as a Long Term Evolution (LTE) system.

The E-UMTS network can be largely divided into E-UTRAN and CN (Core Network). E-UTRAN consists of a terminal (User Equipment; hereinafter abbreviated as UE), a base station (hereinafter abbreviated as eNode B or eNB), and an access gateway (Access Gateway; hereinafter abbreviated as AG) located at the end of the network and connected to the external network. do. AG may be divided into a part in charge of user traffic processing and a part processing control traffic. In this case, a new interface may be used between the AG for handling new user traffic and the AG for controlling traffic to communicate with each other. One or more cells may exist in one eNode B. An interface for transmitting user traffic or control traffic may be used between eNode Bs. The CN may be composed of an AG and other nodes for user registration of the UE, and the like. An interface for distinguishing between E-UTRAN and CN may be used.

The layers of the Radio Interface Protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) standard model, which is widely known in communication systems, L1 (Layer 1) and L2. It can be divided into (2nd layer) and L3 (3rd layer), of which the physical layer belonging to the first layer provides an information transfer service using a physical channel, and the third layer The radio resource control (RRC) layer located in the layer performs a role of controlling radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the UE and the network. The RRC layer may be located distributed among network nodes such as eNode B and AG, or located only in eNode B or AG.

FIG. 2 shows the structure of a control plane among the structures of a radio interface protocol between a UE and E-UTRAN based on the 3GPP radio access network standard. The wireless interface protocol of FIG. 2 horizontally consists of a physical layer, a data link layer, and a network layer, and a user plane for data information transmission vertically. It is divided into a control plane for transmitting and a control signal (Signaling). The protocol layers of FIG. 2 are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems, L1 (Layer 1), L2 (Layer 2), and L3 (Layer 2). It can be divided into three layers).

The first layer, the physical layer, provides an information transfer service to the upper layer by using a physical channel. The physical layer is connected to the upper medium access control layer through a transport channel, and data between the medium access control layer and the physical layer moves through this transport channel. In addition, data moves through physical channels between different physical layers, that is, between the physical layers of the transmitting side and the receiving side.

The second layer medium access control (hereinafter abbreviated as MAC) provides a service to the higher layer, the Radio Link Control layer, through a logical channel. The second layer of the radio link control (Radio Link Control; hereinafter abbreviated as RLC) layer supports reliable data transmission. The function of the RLC layer may be implemented as a function block inside the MAC. In this case, the RLC layer may not exist. The PDCP layer of the second layer performs header compression (Header Compression) function. In addition, integrity protection and ciphering may be performed on a control signal such as an RRC signal and/or user data.

The Radio Resource Control (RRC) layer located at the top of the third layer is defined only in the control plane, and the configuration and resetting (Re) of the radio bearer (Radio Bearer; RB) -configuration) and release (Release) are responsible for the control of logical channels, transport channels and physical channels. In this case, the RB means a service provided by the second layer for data transfer between the UE and the UTRAN. If there is an RRC connection between the RRC of the terminal and the RRC layer of the wireless network, the terminal is in the RRC connected mode (Connected Mode), otherwise it is in the RRC idle state (Idle Mode).

The NAS (Non-Access Stratum) layer located above the RRC layer performs functions such as session management and mobility management.

As a downlink channel for transmitting data from the network to the terminal, a BCH (Broadcast Channel) for transmitting system information, a PCH (Paging Channel) for transmitting a paging message, and a downlink SCH (Shared Channel) for transmitting user traffic or control messages in addition to ) is there. In the case of downlink multicast or broadcast service traffic or control message, it may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, as an uplink channel for transmitting data from the terminal to the network, there are a random access channel (RACH) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or control messages.

The eNB manages radio resources of one or more cells, and one cell is set to one of bandwidths such as 1.25, 2.5, 5, 10, 20Mhz, and provides downlink or uplink transmission services to multiple terminals. In this case, different cells may be configured to provide different bandwidths. And it is also possible to configure cells so that multiple cells are geographically overlapped by using multiple frequencies. The eNB informs the UE of basic information for accessing the network using system information (hereinafter abbreviated as SI). The SI includes essential information that the terminal needs to know in order to access the base station. Therefore, the terminal must receive all SI before accessing the base station, and must always have the latest SI. And, since the SI is information that all terminals in one cell need to know, the base station periodically transmits the SI.

The logical channels that are located above the transport channel and are mapped to the transport channel include a Broadcast Channel (BCCH), a Paging Control Channel (PCCH), a Common Control Channel (CCCH), a Multicast Control Channel (MCCH), and a Multicast Traffic Channel (MTCH). ), DCCH (Dedicated Control Channel), and the like.

A physical channel is composed of several subframes on the time axis and several sub-carriers on the frequency axis. Here, one sub-frame is composed of a plurality of symbols and a plurality of sub-carriers on the time axis. One subframe is composed of a plurality of resource blocks (Resource Block), and one resource block is composed of a plurality of symbols and a plurality of subcarriers. In addition, each subframe is composed of a Physical Downlink Control Channel (PDCCH, L1/L2 Control Channel) and a Physical Downlink Shared Channel (PDSCH, carrying downlink SCH and PCH, etc.), and a specific symbol of the corresponding subframe for their transmission. It is possible to use specific subcarriers of these (eg, the first symbol). And, one resource block is called a slot and has a length of 0.5 ms in time. A transmission time interval (TTI), which is a unit time for data transmission, is 1 ms corresponding to one subframe.

The following describes a method for transmitting and receiving a call message. When receiving a paging message containing a paging record composed of a paging cause and a UE identity, the terminal performs a discontinuous reception cycle (DRX) for the purpose of reducing power consumption. can do. To this end, the network configures several paging occasion times for each time period called the paging DRX cycle, and a specific terminal receives only a specific paging opportunity time to obtain a paging message. The terminal does not receive a paging channel during times other than the specific paging opportunity time and may be in a sleep state to reduce power consumption. One call opportunity time corresponds to one TTI.

The base station and the terminal indicate whether the paging message appears or not by using a paging indicator (hereinafter abbreviated as PI) as a specific value indicating the transmission of the paging message, and a specific identifier (eg, Paging Indicator-Radio Network Temporary) for the purpose of PI. Identity; PI-RNTI), the base station can notify the terminal of call information transmission. For example, the terminal wakes up every DRX cycle and receives one subframe to know whether a call message appears or not. If the terminal has a PI-RNTI in the L1/L2 control channel (PDCCH) of the received subframe, it can know that the PDSCH of the corresponding subframe contains a paging message, and its own terminal identifier (eg, IMSI) in the paging message If there is, the terminal responds to the base station (eg, RRC connection) to receive the service.

The following is the process of moving from the base station (or center base station, source eNB) of the first cell receiving service due to the mobility of the terminal in the connected mode to the base station (or target base station, target eNB) of the second cell. briefly described. In this case, the second cell to which the terminal moves may be a cell corresponding to one of the following cases.

Intra-frequency cell: A cell having the same center-frequency as Radio Access Technology (RAT) as the cell used by the UE. Inter-frequency cell: The same radio access technology (RAT) as the cell being used by the UE. Cell Inter-RAT cell having a different center-frequency from RAT): A cell (eg, GSM, WCDMA) that uses a radio technology (RAT) different from the radio technology used by the terminal (eg, GSM, WCDMA) has mobility, If the signal specific value is lowered by moving away from the base station receiving the service, by allowing the service to be received by another base station having a higher signal characteristic value, the quality of the service provided to the terminal can be improved, and the radio resource usage rate can be increased. Therefore, the UE needs to measure not only the serving cell receiving the service, but also the neighboring cell of the serving cell (Measurement). Neighboring cells are abbreviated as neighboring cells. In the LTE system, as a signal measurement value (or a signal characteristic value), Reference Symbol Received Power (RSRP), Reference Symbol Received Quality (RSRQ), and Received Signal Strength Indicator (RSSI) are being discussed.

4 briefly describes the measurement along with the handover process of the terminal.

1) The base station sets to the terminal a list of frequencies to which the target cell to be measured by the terminal belongs to the terminal. The following information can be set. (Step 1)

- Measurement frequency and radio technology (RAT): Set the frequency and radio technology that the UE should measure.

- Measurement reporting event (measurement reporting event) and offset (offset): means a specific condition for sending a measurement report. For example, a measurement report is sent to an event when the serving cell is higher or lower than a specific value, an event when the neighbor cell is lower than a specific value, an event in which the neighbor cell becomes larger by an offset than the serving cell, and the like.

- Neighbor cell identifier (Cell ID) and/or offset: An identifier is set for two main purposes. A physical ID identified by a reference symbol is used as a cell identifier (Cell ID). (Alternatively, you can use the unique cell ID in the PLMN, Tracking Area, or use the unique cell ID in the world)

i. Neighbor cell to be measured (white listed cell): The base station may inform the terminal of the identifier of the neighbor cell to be measured. The UE can measure cells on a frequency to be measured even if a neighbor cell to be measured is not specified.

ii. Cells that should not be measured or cells that should not report a measurement even if they are measured (black listed cell): The network performs handover to a specific cell by not performing event evaluation or sending a measurement report for a specific cell to the UE can be prevented from becoming As an example, the purpose may be to prevent a handover of a UE receiving a service from another cell to a specific cell because the load of a specific cell is too heavy.

- Threshold to perform measurement (eg, s-Measure in TS 36.331v850): Measuring that the UE consumes that much power. If the measurement value of the serving cell is not lower than the threshold value (s-Measure), the measurement on the neighboring cell is not performed to minimize power consumption.

- Reporting interval: Set the interval for periodically sending measurement reports.

Measurement report evaluation time (timeToTrigger): Set to send a measurement report message when a measurement report event is satisfied during the evaluation time.

- Measurement gap: A time interval for which the UE can measure at a specific time interval is set. A measurement interval may be set for each frequency, or cells of the set frequency/RAT may be measured using one measurement interval. In the current LTE, cells of the same frequency (intra-frequency) as the serving cell can be measured without a measurement interval, and in the case of a neighboring cell on inter-frequency/RAT, measurement is performed using the measurement interval.

- The specific value or measured value in the above refers to the value defined in the system to ensure the quality of the physical signal in data transmission/reception. Accordingly, the value may be different depending on the applied RAT.

2) When a situation that satisfies the criteria specified by the base station occurs, the terminal transmits a measurement report message to the base station. In this case, the measurement report message sent may include measurement result values for one or a plurality of cells, cell identifier values, and the like. (Step 2)

3) The source eNB makes a handover decision with reference to the measurement report message from the UE. The central base station transmits a handover preparation message to the target base station (target eNB). (Steps 3 and 4)

4) After the target base station secures resources, it transmits resource configuration information for the corresponding terminal to the central base station together with a new temporary identifier (C-RNTI) for the corresponding terminal. (Steps 5 and 6)

5) The terminal receives a handover command from the central base station. The central base station starts transmitting user data to the target base station. (Steps 7 and 8)

6) The terminal resets the radio environment to the target base station. This includes synchronizing the timing. (Steps 9 and 10)

7) The target base station responds with timing information. After that, the terminal sends a handover confirm message to the target base station. (Step 11)

8) When the location of the terminal in the core network (eg, MME) is updated, and the target base station notifies the center base station of handover success, the center base station releases the resource of the terminal. (Steps 12 to 18)

Hereinafter, the CSG cell will be described.

5 shows an E-UTRAN structure when a CSG cell is operated.

In FIG. 5, HeNB (or Home eNode B) refers to a base station operating a Closed Subscriber Group (CSG) cell. A CSG cell refers to a cell that can be used only by one or more specific users or terminals, and is used for the purpose of expanding service coverage for users or increasing radio capacity. As an example in which the CSG cell is used, the case of Home Node B, which can be installed and used by a user in the same place as home, can be considered as an example of the CSG cell. Although the CSG cell has narrower coverage than the cell serviced by the eNode B, a low rate policy may be applied to the service received from the CSG cell according to the operator's policy. Therefore, it can be used as a femto cell or a pico cell, which are common terms in wireless communication. In other words, a femto cell in wireless communication can be applied as a term CSG cell in LTE. Hereinafter, a cell operated by the eNode B is abbreviated as a normal cell or a macro cell to distinguish it from a CSG cell.

The CSG cell needs to allow only a specific user or group to use the service in the cell. For example, in case of a CSG cell operated for wireless communication in a home, an example may be that only people belonging to the household receive a service from the cell.

Basically, the terminal can receive a normal service (eg, streaming service, normal voice call) in an accessible CSG cell, and in an inaccessible CSG cell, a limited service such as an emergency call can be used. A CSG cell in which a user of a specific terminal can receive a general service is called an 'Allowed CSG cell or accessible CSG cell', and a CSG cell that cannot receive a general service is a 'Not allowed CSG cell' (not allowed) CSG cell or inaccessible CSG cell)

The following describes specific details about the CSG cell:

- A specific CSG cell has a CSG ID corresponding to a specific group, and preferably, a plurality of CSG cells corresponding to a specific CSG ID may exist. However, the CSG ID itself may be a unique value in a specific Public Land Mobile Network (PLMN) or a specific area (eg, Tracking Area), or may be a unique value in the world.

- There may be the following methods as a method for a specific terminal to know the accessible CSG group, that is, the accessible CSG ID.

i. It is known through a list of one or more CSG IDs accessible to the USIM.

ii. A list of CSG IDs accessible from the network is allocated from the network in the process of registering with the network or registering a location, such as Attach or Tracking Area Update.

iii. Due to the user's access to a cell with a specific CSG ID or an attempt to access a specific CSG cell (e.g., the user inputs a name pointing to a specific CSG cell or a specific CSG group, or the user enters the name of the Home eNB) A specific CSG ID is known as an accessible CSG.

- The above-mentioned methods for the UE to know the accessible CSG cell may be used interchangeably, and the identifier (CSG ID) of the accessible CSG group may be updated such as addition or deletion by a specific method. . Here, CSG IDs accessible to a specific terminal are called a CSG White List or an allowed CSG list.

- In a method that enables the UE to distinguish whether a specific cell is a macro cell or a CSG cell, it broadcasts whether a CSG cell is a CSG cell through system information or divides available physical IDs into CSG cells and general cells. By doing so, it is possible for the terminal to distinguish whether a specific neighboring cell is a CSG cell.

- The CSG ID is broadcast through the system information, and the UE reads the system information of a specific neighboring CSG cell and compares it with the accessible CSG IDs (ie, CSG white list) that the neighboring cell has. In the case of a CSG cell, it may be known whether the CSG cell is accessible or not.

- Based on the allowed CSG list that the UE has, it is determined whether a specific cell can be accessed.

- As can be seen above, by acquiring the measurement and system information of the neighboring cell, the UE determines whether the physical ID and CSG of the neighboring cell and the accessible CSG ID list that the UE has (ie, allowed CSG list or CSG white list) ) to determine whether neighboring cells are accessible.

- If the UE has an allowed CSG list, the UE searches for a cell of the allowed CSG list at a specific period or time point according to implementation, regardless of the 3GPP standard (eg, TS 36.331), and provides a service in the CSG cell to which it is accessible make it possible to receive This is called an autonomous search function.

- In the case of cell-reselection (cell reselection, the process of changing the serviced cell by camping on from the serving cell to the neighboring cell), the terminal in the idle mode is the CSG white list that the terminal has in the neighboring CSG cell. If it belongs to the cell-reselection, it satisfies the requirements of a suitable cell, making it a candidate for the ranking-process for re-selecting the cell with the largest signal measurement value, so that the CSG cell is cell re-selection. can make it happen On the other hand, if the neighboring CSG cell does not belong to the CSG white list possessed by the UE, the cell does not become a candidate for the ranking-process, so that the cell re-selection to the CSG cell that can receive the general service is prioritized.

- The process in which a terminal in connected mode is handed over to a CSG cell follows the same process of handover to a general cell.

<p>The following is a brief description of a process in which the UE performs handover to a specific CSG cell as an example. It is assumed that the UE has an allowed CSG list.</p><p>One. It is searched whether there is a CSG cell belonging to the allowed CSG list by the automatic search function of the terminal.</p><p>2. The UE determines whether it is a CSG cell from among the detected neighboring cells, and also determines whether it is an accessible CSG cell by comparing it with the allowed CSG list by acquiring the CSG ID of a specific neighboring cell through system information of the neighboring cell. At this time, in order to obtain the CSG ID of the system information of the neighboring cell, the UE uses the measurement interval allocated from the base station when the neighboring cell has a different frequency (or RAT) from the serving cell (process 1 in FIG. 4), It may request a measurement time (Measurement Gap request) and measure a neighbor cell and receive system information at the allocated time.</p><p>3. The UE performs measurement for a specific time (eg, timeToTrigger) on the detected normal cell and CSG cells, and the condition for sending a measurement report message during that time (eg, the signal characteristic value of a neighbor cell rather than a serving cell is a specific value (threshold or offset) or higher), a measurement report message is sent. In this case, not only the measurement value/identifier of the CSG cell but also the measurement value/identifier information of the normal cell are transmitted through the measurement report message.</p><p>4. The subsequent process follows the process described above (that is, the base station determines to which cell the terminal is handed over based on the measured value of the cell and performs the handover).</p><p>As can be seen from steps 1 to 4, if the measured value of the serving cell of the UE is lower than the threshold (ie, s-Measure), the UE performs measurements on neighboring cells including the CSG cell and the normal cell. . And, if the result value to be measured satisfies the condition for sending a measurement report (eg, a condition where the neighbor cell is greater than a specific threshold value is satisfied for a specific time; event A4 (Neighbor becomes better than threshold during timeToTrigger described in 3GPP TS36.331) , the UE transmits a measurement report message including the identifiers of each cell together with the measurement values of the cells being measured to the base station of the serving cell. At this time, the base station, according to an arbitrary determination (eg, the cell with the best measurement value, the cell with the least load), the target (the target base station, the target cell) in the handover command (handover command or mobility control information in RRC connection reconfiguration) Transmits (or instructs) to the terminal, including the identifier (eg, physical ID) information of a specific cell to be may be transmitted.) The UE performs handover to a specific neighboring cell to maintain the service (eg, ftp download) being received from the serving cell.</p><p>In the above, the measurement report message received by the network from the UE includes the measurement values along with the physical IDs of the general cell and the CSG cell, and the network determines whether the specific CSG cell in the received measurement report message is a CSG cell accessible to the specific UE. Alternatively, since it is impossible to distinguish whether it is an inaccessible CSG cell (that is, because the UE has an allowed CSG list), the UE may issue a handover command to an inaccessible CSG cell. When the terminal is handed over to an inaccessible CSG cell, it can no longer receive a general service. Therefore, a general service (eg, ftp download) received from the serving cell (ie, the source cell) is handed over to an inaccessible CSG cell, and then the service is interrupted.</p><p>Therefore, by sending a measurement report message containing only the measurement results of the accessible CSG cell and the normal cell to the source eNB of the serving cell, it is possible to prevent handover to the inaccessible CSG cell as described above.</p><p>However, on the other hand, a user who was receiving an urgent service (or limited service) such as an emergency call (e.g., 119 in korea, 911 in USA) service makes an emergency call even if handover to an inaccessible CSG cell. can keep going Therefore, when there is no cell capable of handover among the cells that are candidates for the target cell of the measurement report message (eg, when it is difficult to provide a service because the signal measurement value is less than a certain value, or when the service is difficult because the load is too heavy) Since it may occur, it may be necessary to transmit the measurement report message even in an inaccessible cell, so that an emergency call is continuously maintained. However, since a user who has completed an emergency call in an inaccessible CSG cell needs to change the cell to an accessible CSG cell or a normal cell in order to receive general service, the terminal can receive general service. In order to receive , it is necessary to measure and receive system information to change cells, which may cause a problem of wasted power (above, for convenience of explanation, the present invention is called 'the first problem of the prior art' to be solved) ).</p><p>On the other hand, as can be seen in steps 1 to 4, since the CSG cell has a small service coverage, a plurality of CSG cells may exist in the area of one general cell. In this situation, if the CSG cell is continuously searched for by the automatic search function at a specific period, serious power consumption is caused by the measurement process for determining the existence of the CSG cell. Currently, 3GPP TS36.331 reduces power consumption by measuring neighboring cells only when the measured value of the serving cell (which is arbitrarily ordered as serving) is less than or equal to a specific value (eg, s-Measure). For example: s-Measure), it can be seen that power is wasted by CSG discovery because the discovery process for detecting CSG cells is performed.</p><p>In addition, in the current standard, if the measured value of the serving cell does not exceed a specific threshold (ie, s-Measure), the neighboring cell is not measured. That is, the measurement is not performed regardless of whether the neighboring cell is a normal cell or a CSG cell. As a result, the terminal does not send a measurement report from the base station. As a result, even if the terminal receiving the service in the normal cell enters the area of the accessible CSG cell with good signal characteristics, if the signal characteristic value of the normal cell currently being serviced is good, handover to the CSG cell can be performed. lead to non-existent results. That is, it results in that a service cannot be received in a CSG cell to which a higher bandwidth or a lower cost is applied.</p><p>6 is a block diagram illustrating a case in which the terminal enters the area of the CSG_B cell.</p><p>In FIG. 6, even if the terminal enters the area of the CSG_B cell, if the signal characteristic value of the normal cell (non-CSG cell in FIG. 6) is better than s-Measure, the terminal does not measure CSG-B, A measurement report message for CSG_B is not sent to a base station of a normal cell that is not currently receiving service. As a result, since the terminal does not receive a handover command for CSG_B from the base station of the normal cell, it cannot receive the service from CSG_B.</p><p>For example, even if the user enters the house while talking on the phone from outside the house, it may result in not receiving the service from the cell to which the cheap communication fee installed in the house is applied, which may be a direct factor causing the user's service dissatisfaction. (above, for convenience of description, the present invention is referred to as 'the second problem of the prior art').</p>

<p>Therefore, a first object of the present invention is to prevent a phenomenon in which a service in service is interrupted due to handover to an inaccessible CSG cell in the process of allowing a terminal to receive a service from the CSG cell in order to solve the first problem of the prior art. We aim to provide a high quality of service to users by providing a method to</p><p>In addition, a first object of the present invention, in order to solve the first problem of the prior art, when the terminal is handed over from a serving cell (ie, source cell) to a neighboring CSG cell (ie, target cell), access An object of the present invention is to provide a method that enables a user to continuously receive a user's general service by handover to a possible CSG cell.</p><p>In order to realize the first object as described above, the present invention transmits a measurement report message containing only the measurement results for the accessible CSG cell and the normal cell to the source eNB of the serving cell, and as described above, the non-accessible CSG It is proposed to prevent handover to the cell.</p><p>A user who was receiving an urgent service (or limited service) such as an emergency call (e.g., 119 in Korea, 911 in USA) service in the serving cell (souce cell) makes an emergency call even if handover to an inaccessible CSG cell can continue to be maintained. Therefore, it can be said that it is necessary to transmit the measurement report message even to the existing inaccessible cell.</p><p>In addition, in order to realize the first object as described above, in the present invention, when the service being received by the serving cell is a limited service such as an emergency call, when a measurement report message is sent, information on the normal cell and the CSG cell (eg: physical ID, measurements, etc.) are suggested to be sent.</p><p>To this end, the present invention transmits both information (eg, physical ID, measurement value, etc.) of the normal cell and the CSG cell when sending a measurement report message when the service being received by the serving cell is a limited service such as an emergency call. In this case, it is proposed to transmit information on whether the CSG cell is accessible.</p><p>To this end, the present invention, regardless of the type of service being received by the serving cell, when sending a measurement report message, when sending information (eg, physical ID, measurement value, etc.) of a general cell and/or CSG cell, the CSG cell It is proposed to transmit information on the accessibility of</p><p>On the other hand, a second object of the present invention is to solve the second problem of the prior art, to provide a method for minimizing power waste generated in the process of allowing a terminal to receive a service in a CSG cell, and also to provide a CSG accessible to the terminal An object of the present invention is to provide a method of providing high quality of service to users by accelerating the time at which a service is received from a cell.</p><p>To this end, the present invention is to provide a method of reducing power consumption in the operation of the UE measuring for movement from the connected mode to the CSG cell.</p><p>To this end, the present invention proposes not to perform the operation of measuring the CSG cell when the measured value of the serving cell does not exceed a specific threshold.</p><p>To this end, the present invention proposes that a specific threshold for measurement of a CSG cell is a specific value different from s-Measure currently used in 3GPP TS36.331.</p>

<p>A first embodiment of the present invention provides a method for reducing power consumption in moving to a CSG cell when a cell (eg, a CSG cell) that a specific user or group can use is used on a network, and a method for receiving a service When entering the service area of the CSG cell during a call (e.g., during a call or while downloading a file from the ftp server), it enables handover to a CSG cell that the terminal can access and maintains the service. rather than providing services at low cost. In addition, it suggests a way to effectively maintain services such as emergency calls. In the present invention, the terminal informs the network whether the terminal can access neighboring CSG cells, and enables the network to distinguish the cell in which the terminal can continue to maintain the service, so that the terminal can maintain the service as a target cell. By enabling handover, a method of reducing power consumption as well as providing high-quality service to users is provided.</p><p>A second embodiment of the present invention provides a method for reducing power consumption in moving to a CSG cell when a cell (eg, a CSG cell) that a specific user or group can use is used on a network, and a method for receiving a service When entering the service area of the CSG cell (eg, during a call or while downloading a file from the ftp server), handover to the CSG cell is possible. In the present invention, the network may transmit a threshold value limiting the measurement of the CSG cell, and the UE performs measurement of the neighboring CSG cell only when the measurement value of the serving cell is less than or equal to the received threshold value. In another invention, the UE performs measurement when it finds an accessible neighboring CSG cell regardless of the threshold value (eg, s-Measure, sg-Measure) that limits the measurement defined in the system, so that the handover is performed make it possible Through the present invention, the terminal not only provides a method for extending the terminal use time to the user by effectively reducing power consumption on a network in which the CSG cell is distributed, but also provides a service in the CSG cell while receiving the service in the general cell. It provides a method to provide high quality of service to users.</p>

1 is a diagram illustrating a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS), which is a mobile communication system to which the prior art and the present invention are applied. 2 is a structure of a control plane among the structures of a radio interface protocol between a UE and E-UTRAN based on the 3GPP radio access network standard. 3 is a diagram illustrating control channel transmission in an LTE system. 4 is a signal flow diagram illustrating a handover process of a terminal in an LTE system. 5 is an E-UTRAN structure when a CSG cell is operated. 6 is a block diagram illustrating a case in which the terminal enters the area of the CSG_B cell. 7 is a block diagram illustrating that a terminal receives an emergency call after handover when CSG_C is an inaccessible CSG cell as an embodiment of the present invention. 8 is an example of a second embodiment of the present invention, and is a diagram illustrating a process of measuring an accessible cell regardless of a measurement value of a serving cell when an accessible cell is found. <b>Modes for carrying out the invention</b> The present invention is applied to a mobile communication system, particularly an E-UMTS system. However, embodiments of the present invention are not limited thereto, and may be applied to all communication systems and communication methods to which the technical spirit of the present invention can be applied. Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. Terms including ordinal numbers such as first, second, etc. may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related described items or any of a plurality of related described items. When a component is referred to as being "connected" or "connected" to another component, it may be directly connected or connected to the other component, but another component may exist in between. On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle. The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof. Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, and in the description with reference to the accompanying drawings, the same or corresponding components are given the same reference numbers regardless of the reference numerals and overlapped therewith. A description will be omitted. The present invention is divided into a first embodiment and a second embodiment for convenience of description. In both the first and second embodiments of the present invention, in the Evolved Universal Mobile Telecommunications System (E-UMTS) evolved from the UMTS (Universal Mobile Telecommunications System), the service is provided by the first base station for the macro cell or the CSG cell. When the receiving terminal accesses the second base station operating the CSG cell, a method of performing measurement according to whether the second base station can access the CSG is provided. In addition, the first embodiment of the present invention provides a method that can be continuously provided to the user according to a general service (eg, file download) or an emergency service (eg, emergency call) and at the same time reduces power to provide a service to the user It provides a way to improve quality. In addition, the second embodiment of the present invention performs measurement on an accessible CSG cell regardless of the measurement value of the serving cell to enable handover to the CSG cell, so that the user can receive a service from the CSG cell. , we propose a method to increase user satisfaction with the service. Hereinafter, a first embodiment of the present invention will be described. A first embodiment of the present invention provides a method for preventing a service interruption in service due to handover to an inaccessible CSG cell in the process of allowing a terminal to receive a service from a CSG cell, thereby providing a high quality of service to a user. will be. Therefore, according to the first embodiment of the present invention, when the terminal is handed over from a serving cell (ie, source cell) to a neighboring CSG cell (ie, target cell), the user's general service is performed by handover to an accessible CSG cell. It provides a way to make it possible to continuously receive To this end, the first embodiment of the present invention transmits a measurement report message containing only the measurement results for the accessible CSG cell and the normal cell to the source eNB of the serving cell, and handover to the non-accessible CSG cell as described above. can be prevented from doing In addition, in the first embodiment of the present invention, the user who was receiving an urgent service (or limited service) such as an emergency call (e.g., 119 in Korea, 911 in USA) service in the serving cell (source cell), Even if a handover is made to an inaccessible CSG cell, an emergency call can be maintained continuously. Therefore, it can be said that it is necessary to transmit the measurement report message even to the existing inaccessible cell. To this end, in the first embodiment of the present invention, when the service received by the serving cell is a limited service such as an emergency call, when a measurement report message is sent, information (eg, physical ID, measurement value) of the normal cell and the CSG cell , etc) are all sent. In addition, according to the first embodiment of the present invention, when the service received from the serving cell is a limited service such as an emergency call, when a measurement report message is sent, information on the normal cell and the CSG cell (eg, physical ID, measurement value, etc.), information on whether the CSG cell is accessible is also transmitted. To this end, the first embodiment of the present invention provides information (eg, physical ID, measurement value, etc.) of a normal cell and/or CSG cell when a measurement report message is sent, regardless of the type of service received by the serving cell. ), information on whether the CSG cell is accessible is also transmitted. Hereinafter, a first embodiment of the present invention will be described in more detail. In the first embodiment of the present invention, the proposed accessibility information can be expressed in the following way: - A specific value indicating whether access is possible (eg, 1-bit indication): an accessible CSG cell and a normal cell are set to 1 (or 0), and an inaccessible CSG cell is set to 0 (or 1). - Defines the format for sending measurement report messages to indicate whether they are accessible: Example: The non-accessible cells are transmitted in different set or list formats, and the base station can know whether it is accessible or not according to the set format. * Accessible cell list (or set) {(physical_ID_A,-100dbm), (physical_ID_B,-101dbm)} * Inaccessible cell list (or set) {(physical_ID_C,-100dbm), (physical_ID_D,-101dbm)} * The accessible cell list includes both a normal cell and an accessible CSG cell, or a list (or set) may be separately defined for a normal cell and an accessible CSG cell. Preferably, in the above, information on whether neighboring cells are accessible can be transmitted to the base station through the following method in addition to a measurement report message. - L1/L2 control channel: A specific value indicating whether access to a channel transmitting control information, such as PDCCH, is possible can be transmitted to the terminal. Like a PI-RNTI that notifies the existence of a call message, an RNTI indicating an identity value indicating whether access is possible may be defined and used. - RRC signaling: Radio Bearer Setup, Radio Bearer Reconfiguration, RRC Connection Request, RRC Connection Reconfiguration, RRC Connection Reconfiguration Accessibility can be transmitted through signals related to -establishment). - NAS signaling: A threshold value may be transmitted through a NAS signal such as a message in the Tracking Area Update process. - Accessibility can be transmitted through PDUs such as RLC, MAC, and PDCP, and can be transmitted by all signaling procedures of the base station and the terminal. Hereinafter, another embodiment of the first embodiment of the present invention will be described. In case of an emergency call, service can be received even if handed over to an inaccessible CSG cell. In addition, even when the cell cannot be used even for emergency calls for system information regardless of the general cell or CSG cell (eg, when cellBared is barred in 3GPP TS36.331 or when the cell load is heavy), the base station Or, since it is possible to know whether the cells of neighboring base stations) are available (that is, the base station is difficult to know whether the terminal/user can use a specific CSG cell, but regardless of the user/terminal, whether the cell itself can be used can be known. .), when sending a handover command to the terminal, the handover command can be instructed to a neighboring cell that can use an emergency call. Therefore, as another invention, when receiving a service such as an emergency call, when handover to a neighboring cell is required (eg, when the measured value of the serving cell falls below a specific value), even if the neighboring cell is a CSG cell, CSG It is proposed not to perform an operation to obtain an ID. The operations for acquiring the CSG ID may include the following. - Measurement Gap Request: In order to receive system information to obtain the CSG ID of a neighboring CSG cell, measurement is required for a specific time, and for this, a measurement gap may be requested. - Acquire system information: Receive system information to read CSG ID According to the present invention, the terminal can prevent power wastage of measurement for obtaining the CSG ID. 7 is a block diagram illustrating that a terminal receives an emergency call after handover when CSG_C is an inaccessible CSG cell as an embodiment of the present invention. Hereinafter, it will be described with reference to FIG. 7 . If the service currently being received by the terminal is a general service (eg, ftp download), only the normal cell and accessible CSG cell among the measured cells are put in the measurement report message and sent to the base station to handover to the accessible cell to receive the general service. In the case that the service currently being received by the terminal is an emergency service (or limited service or special service) such as an emergency call, all the measured cells can be put in a measurement report message and sent to the base station, so that the general service is not available. Even if there is no serviceable cell among the available normal cells or accessible CSG cells (for example, in FIG. 6, if CSG_C is an inaccessible CSG cell, that is, the signal characteristic value satisfies a specific threshold or more that can receive service If there is no general cell or accessible CSG cell), emergency call service can be continued in the non-accessible CSG cell. In the first embodiment of the present invention, when the UE transmits the measurement report to the base station receiving the service (source eNB), it can inform whether the access is possible together with the measurement result of the neighboring cell, so the base station transmits the measurement report message from the UE Based on the , it is possible to know whether the terminal of a specific CSG cell approaches. Accordingly, the base station may instruct the handover command to a cell accessible to the terminal. Accordingly, it is possible to prevent the case where the terminal cannot receive a general service due to handover to an inaccessible CSG cell as in the example described above. In addition, in the first embodiment of the present invention, even when the terminal performs a handover while receiving a limited service (or a service having a specific purpose) such as in the case of an emergency call, an inaccessible CSG cell and Since information on whether access to an accessible CSG cell or/and a normal cell can be informed, the base station can issue a handover command to a cell capable of general service. Therefore, when a user receiving an emergency call service performs handover, it is possible to handover to an accessible CSG cell or a normal cell, effectively reducing power consumption for receiving measurement or system information to go to a normal cell after the emergency call is finished. can be reduced Hereinafter, a second embodiment of the present invention will be described. The second embodiment of the present invention provides a method for minimizing power wastage that occurs in the process of allowing the terminal to receive a service in a CSG cell, and also provides a high level of service to the user by accelerating the time at which the terminal receives a service in an accessible CSG cell. to provide quality of service. To this end, the second embodiment of the present invention proposes the following: First, a method is provided for reducing power consumption in an operation in which a UE measures for movement to a CSG cell in a connected mode; Second, if the measured value of the serving cell does not exceed a specific threshold, it is proposed not to perform the operation of measuring the CSG cell; Third, it is proposed that the specific threshold for measurement of the CSG cell be a specific value different from s-Measure currently used in 3GPP TS36.33l. Hereinafter, terms and prerequisites defined in the second embodiment of the present invention will be described: A threshold value for measurement of a CSG cell proposed by the second embodiment of the present invention will be arbitrarily named as sg-Measure and will be described. Here, s-Measure is used as a threshold value for measurement of a normal cell, and sg-Measure is used as a threshold value for measurement of an accessible CSG cell. If the threshold value (ie, sg-Measure) proposed in the second embodiment of the present invention exceeds a specific threshold value (ie, sg-Measure) suggested by the measured value of the serving cell, the CSG cell is searched (eg: Stop the automatic search function) and/or it is suggested not to perform the measurement operation. In addition, if the threshold value (ie, sg-Measure) proposed in the second embodiment of the present invention does not exceed a specific threshold value (ie, sg-Measure) suggested by the measured value of the serving cell, the CSG cell is searched ( It is suggested to be able to perform actions such as starting an automatic search function) and/or measuring. In addition, due to the use of the sg-Measure, different threshold values (ie, s-Measure and sg-Measure) are compared with the measurement value of the serving cell (ie, Sserving), and the measurement time point for different neighboring cells can be determined, resulting in the following performance improvements: - When s-Measure &gt; sg-Measure is set: sg-Measure has a lower value than s-Measure. In this case, when the measured value (Sserving) of the serving cell is gradually lowered due to the mobility of the terminal, the condition of sg-Measure &gt; Sserving is satisfied before the condition of s-Measure &gt; Sserving. Since the measurement is performed before the time of measurement, the measurement report value of the CSG cell can be transmitted first through the measurement report message, thereby increasing the possibility that the user can handover to the CSG cell; - When s-Measure &lt; sg-Measure is set: s-Measure has a lower value than sg-Measure. In this case, when the measurement value (Sserving) of the serving cell is gradually lowered due to the mobility of the terminal, the condition of s-Measure &gt; Sserving is satisfied before the condition of sg-Measure &gt; Sserving. Since the measurement time of the normal cell is performed before the time of measuring the CSG cell, the measurement report value of the normal cell is first sent through the measurement report message. This means that even if multiple CSG cells are found in an area where CSG cells are densely distributed (regardless of CSG cells accessible or inaccessible to the user), if the measured value of the serving cell does not fall below sg-Measure, CSG Since the cell measurement is not performed, it is possible to prevent power consumption in the measurement for the CSG cell. In the above, the setting of the s-Measure value and the sg-Measure value may be determined in consideration of geographic characteristics such as the size of a general cell (service coverage), the number or density of CSG cells, or operator policy ) can be set and used. Methods for the network to deliver the threshold value used to measure the CSG cell proposed in the present invention to the terminal may be as follows: - System Information: Transmits a threshold value through system information. There are two main ways to do this. There may be a method of delivering a threshold value commonly applied to neighboring CSG cells through system information of the serving cell. As another method, each CSG cell transmits a threshold value for measuring its own cell as system information, and a specific terminal acquires a threshold value through system information of a neighboring CSG cell, When performing measurements, the obtained threshold is applied; - Paging: A threshold value can be transmitted to the terminal through a paging signal. That is, like a paging record consisting of the call reason and the terminal identifier, the threshold value is put in the paging message and transmitted to the terminal. In this case, if there is a call record in the call message, the terminal performs the above-described normal call procedure according to the call record information, and if there is a threshold value, the terminal performs the corresponding operation. When the call history information and the threshold value exist in the call message at the same time, whether to perform all operations or only one operation according to each information can follow the definition of the system. In another case, the threshold may be in the content of the call log. In addition, the call record and the threshold value are written together, so that only a specific terminal can perform an operation according to the threshold value according to the terminal identifier like a call procedure; - L1/L2 control channel: A specific value indicating a threshold value may be transmitted to the terminal on a channel for transmitting control information, such as PDCCH. An RNTI indicating an identity value indicating a threshold may be defined and used, such as a PI-RNTI indicating the existence of a call message; - RRC signaling: Measurement Configuration, Radio Bearer Setup, Radio Bearer Reconfiguration, RRC Connection Request/Connection Setup/Disconnect (Connection Release), RRC connection reconfiguration (RRC Connection Reconfiguration), RRC connection re-establishment (Connection Re-establishment) related signals, the threshold value may be transmitted through; - NAS signaling: a threshold value may be transmitted through a NAS signal such as a message in the Tracking Area Update process; - Threshold values can be transmitted through PDUs such as RLC, MAC, and PDCP, and can be transmitted through all signaling procedures of the base station and the terminal; According to the threshold value and measurement method proposed in the second embodiment of the present invention, when sg-Measure is configured for the terminal, the terminal even when a CSG cell is found (eg, when it is discovered by an automatic search function), a serving cell If the measured value of sg-Measure is greater than (or greater than) sg-Measure, the power consumption due to the measurement can be effectively reduced by not performing the measurement. Hereinafter, another embodiment (invention) of the second embodiment of the present invention will be described. When the terminal enters the area of the accessible CSG cell, the time of receiving the service is made faster, so that the user can receive a service with a high bandwidth or a low cost. To this end, in the second embodiment of the present invention, when the terminal enters the area of the accessible CSG cell, the time of receiving the service is accelerated, so that the user can receive a high-bandwidth or low-cost service. In addition, the second embodiment of the present invention for this purpose, even if the measured value of the serving cell is higher than a specific threshold value, if the CSG is accessible, the measurement is performed on the corresponding CSG cell, a measurement report message (measurement report) It is proposed to enable handover by sending In addition, for this purpose, in the second embodiment of the present invention, when the terminal discovers a neighboring CSG cell (eg, by an automatic search function), the value of the serving cell (s-Measure) in case the neighboring CSG is an accessible CSG cell. Alternatively, it is proposed to measure accessible CSG cells regardless of sg-Measure) proposed by the present invention. 8 is an example of a second embodiment of the present invention, and is a diagram illustrating a process of measuring an accessible cell regardless of a measurement value of a serving cell when an accessible cell is found. However, in FIG. 8 , it is assumed that the UE is always performing the measurement of the serving cell and the automatic search function for finding the CSG cell at a specific periodicity. In FIG. 8 , when a CSG cell is found among neighboring cells (eg, by an auto-discovery function), the UE acquires a CSG ID by receiving system information of the discovered cell. Then, the terminal searches the allowed CSG list and determines whether it is an accessible CSG cell (step in FIG. 8). In addition, in the case of an accessible CSG cell, measurement of an accessible cell can be performed regardless of the measurement value of the serving cell, and a measurement report message can be sent to the base station, so that the terminal can handover to a CSG cell accessible to it will do According to the present invention, when an accessible neighboring CSG cell is found irrespective of the measurement value or signal characteristic value of the serving cell, the UE performs the measurement on the accessible CSG cell, thereby providing a service of the accessible CSG cell through the mobility of the UE. When entering the area, handover to an accessible CSG cell is made possible by performing measurement and sending a measurement report message. As a result, by allowing the user to receive a service in an accessible CSG cell, a high bandwidth is provided to the user or a low charge is applied to the user, so that a high quality service can be received.