KR20120030946A - Apparatus and method for detecting cause of radio link failure or handover failure in mobile communication systme - Google Patents

Abstract

PURPOSE: A failure cause detecting apparatus and method thereof are provided to improve the performance of a mobile communication system by optimizing the handover and a wireless link. CONSTITUTION: A control unit(640) determines the occurrence of handover and a wireless link failure. The control unit access to a connection mode through a connection establishment procedure. A modem(620) transmits a wireless link failure information report to a base station after the modem entry into a connection mode. The wireless link failure information report includes cell identification information and timer. The timer is located between wireless link or handover failure time and a connection success time.

Description

Apparatus and method for detecting a cause of a radio link failure or a handover failure in a mobile communication system {APPARATUS AND METHOD FOR DETECTING CAUSE OF RADIO LINK FAILURE OR HANDOVER FAILURE IN MOBILE COMMUNICATION SYSTME}

TECHNICAL FIELD The present invention relates to a mobile communication system, and in particular, the present invention relates to an apparatus and method for detecting a cause of Radio Link Failure (RFL) and handover failure.

With the development of communication technology, mobile communication system has evolved into SAE (System Architecture Evolution) system. 1 shows a schematic structure of a conventional SAE system. As shown in FIG. 1, the SAE system includes an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 101, a Mobile Management Entity (MME) 105, and a Serving Gateway (S-GW) 106. It includes a core network. The E-UTRAN 101 is configured to connect a user equipment (UE) to the core network, and includes at least one eNB (eNodeB) 102 and at least one HeNB (Home eNB) 103, Additionally, the mobile station may further include a Home eNodeB (HeNB) Gateway 104. The MME 105 and the S-GW 105 may be integrated into one module or may be implemented separately. The eNB 102 is connected to another eNB 102 through an X2 interface, and is connected to each of the MME 105 and the S-GW 105 through an S1 interface. The HeNB 103 is connected to each of the MME 105 and the S-GW 105 via an S1 interface, or is connected to the HeNB GW 104 via an S1 interface, and then the HeNB GW 104. ) May be connected to each of the MME 105 and the S-GW 105 through an S1 interface.

In the early stages of SAE system development or in the operation of the SAE system, the SAE system is designed to optimize the system's parameters, particularly radio parameters such as good coverage, capacity, mobility enhancement, load balancing, etc. Should be used. In order to save the human and material resources consumed during the operation of the SAE system, a method of self-optimizing the SAE system has been proposed. During the self-optimization procedure, the configuration of the eNB or HeNB is optimized according to the current stage of the SAE system. In the following description of the self-optimization scheme, both the eNB and the HeNB are referred to as eNBs.

2 schematically illustrates the basic principle of self-optimization of a SAE system. As shown in FIG. 2 above, a self-configuring (self-configuration) procedure may be initiated by the eNB powering on or connecting to the SAE system. The self-configuration procedure includes a basic configuration 210 and an initial radio parameter configuration 220 for the eNB. The basic configuration 210 for the eNB may include configuring an Internet Protocol (IP) address of the eNB, detecting an OAM (Operation Administration and Maintenance) 211, and authenticating between the eNB and the core network ( 212) If the eNB is a HeNB, the method includes detecting the HeNB GW to which the eNB belongs (213), operating the eNB for self-configuration, and downloading the parameters of the software (214). The initial radio parameter configuration 220 may be implemented by experiment or simulation. Since the performance of each eNB in the SAE system is affected by the environment of the region where the eNB is located, the eNB needs to initialize the radio parameter configuration according to the environment of the region where the eNB is located. Specifically, the eNB performs an initial configuration 221 of the neighbor area list and an initial configuration 222 for load balance. After the self-configuration procedure, many parameters configured by the eNB are optimized. That is, in order to make the SAE system have better performance, it is necessary to optimize or adjust the configuration of the eNB, which is also called self-optimization of the mobile communication system. If the configuration of the eNB is optimized or adjusted, it may be implemented by the eNB under the control of the OAM in the background. Specifically, there may be a standardized interface between the eNB and the OAM, and the OAM may transmit a parameter to be optimized to the eNB or the HeNB through the standardized interface, and the eNB may self-determine according to a parameter to be optimized. Parameters can be optimized at the configuration stage. Alternatively, the configuration of the eNB may be optimized or adjusted by the eNB itself. For example, the ENB can detect or obtain the performance to be optimized and optimize or adjust its parameters according to the performance. Optimization or adjustment of the configuration of the eNB 230 is a process of self-optimizing the neighbor list (231), the process of self-optimizing coverage (coverage) and capacity, the process of self-optimizing mobile robustness, load Self-optimizing the balance 232, self-optimizing the RACH (Random Access Channel) parameter, and the like.

Currently, SAE release 8 proposes self-optimization of neighbor list, while release 9 proposes self-optimization of coverage and capacity self-optimization and mobility enhancement. The basic principle of self-optimization in the defined technique is as follows. According to the difference between the handover of the last successful UE and the point in time at which the UE attempts to re-establish a Radio Resource Control (RRC) connection, the eNB has a handover too late or too fast so that self-optimization can be performed. Or, it is determined that the wrong cell is performed.

However, in the above-described conventional technique for self-optimization, after the UE successfully reestablishes the RRC connection, whether the handover is too late or a coverage leak occurs according to UE measurement information obtained by the UE. Whether or not can be determined. However, after the UE fails to reset the RRC connection, for example, if the eNB receives an RRC re-establishment request but fails during the reset procedure, the eNB to which the UE attempted to reset the RRC connection indicates an RLF indication. When transmitting to the eNB in charge of the cell in which the RLF has occurred, the cell in which the RLF has occurred can distinguish whether a coverage leak or too late handover has occurred. On the other hand, if the eNB that the UE attempts to reset the RRC connection does not transmit an RLF indication to the eNB in charge of the cell in which the RLF has occurred, the cell in which the RLF has occurred is the time when the UE succeeded in the last handover and the UE attempted to reset the RRC connection. The time difference is not known and thus it is not possible to distinguish whether the handover is too late, too fast, or with the wrong cell. Alternatively, even if the UE reports the difference to the network after reconnecting to the network, the network may still make a wrong decision because the difference between the time that the UE attempts to reset the RRC and the time of the RLF / handover failure is large. .

As described above, in self-optimization using conventional approaches for detecting the cause of RLF or handover failure, after failing to reset the RRC connection, the network still has to determine the failure cause determined by whether the RRC connection is successfully reset. If self-optimization is performed on the basis, the analysis of the cause of failure can be wrong. As a result, the self-optimization procedure may also go wrong and affect network performance.

Accordingly, an object of the present invention is to provide an apparatus and method for detecting a cause of an RLF or handover failure in a mobile communication system.

Another object of the present invention is to provide an apparatus and method for performing correct self optimization according to a cause of an RLF or handover failure in a mobile communication system.

It is another object of the present invention to provide an apparatus and method for improving performance through proper self-optimization in a mobile communication system.

According to a first aspect of the present invention for achieving the above object, a method of operating a terminal in a mobile communication system, after determining whether the RLF or handover failure occurs, and after experiencing the RLF or the handover failure, Entering a connected mode through a connection reset or connection establishment procedure; and after entering the connected mode, transmitting a RLF information report to a base station, wherein the RLF information report includes a failure of the RLF or handover by the terminal. Information indicating whether a handover has been performed before experiencing the UE, a UE measurement result of a UE measurement of neighboring cells and serving cells of the UE when an RLF or handover failure occurs, and hand to a cell in which the RLF or handover failure has occurred Before the over, the identity of the cell where the terminal is located, the RLF or the identity of the cell where the handover failure occurred, the RLF or the hand And at least one of a timer between the time of the dover failure and the time of subsequent connection reestablishment success or connection establishment success.

According to a second aspect of the present invention for achieving the above object, a method of operating a base station in a mobile communication system, the process of performing a connection reset or connection establishment procedure with a terminal experiencing a RLF or handover failure, and RLF from the terminal Receiving an information report, and transmitting the RLF information report to a base station that controls the RLF or the cell in which the handover has occurred, wherein the RLF information report includes an RLF or handover failure. Information indicating whether a handover has been performed before, when a RLF or a handover failure occurs, handover to a cell in which the RLF or handover failure has occurred as a result of UE measurement for the neighbor cell and the serving cell of the terminal. Identity of the cell where the terminal is located, RLF or identity of the cell where the handover failure occurred, RLF or And at least one of a timer between a time of handover failure and a time of subsequent connection reestablishment success or connection establishment success.

According to a third aspect of the present invention for achieving the above object, a method of operating a base station in a mobile communication system includes the steps of receiving an RLF information report generated by a terminal experiencing an RLF or handover failure from another base station; And determining a cause of the RLF or the handover failure according to the RLF information report, wherein the RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure has occurred. When the RLF or the handover failure occurs, the UE measurement result of the UE measurement for the neighboring cell and the serving cell of the terminal, before identification of the cell where the terminal is located before handover to the cell where the RLF or handover failure occurs , Identity of the cell in which the RLF or handover failure occurred, the time of the RLF or handover failure, and subsequent connection reset success It is characterized in that it comprises at least one of a timer (timer) between the time of connection establishment success.

According to a fourth aspect of the present invention for achieving the above object, in a mobile communication system, the terminal device determines whether an RLF or handover failure occurs, and after resetting the connection or reconnecting after experiencing the RLF or the handover failure, And a control unit for entering a connected mode through a setting procedure and a modem for transmitting an RLF information report to a base station after entering the connected mode, wherein the RLF information report includes a hand before the terminal experiences an RLF or handover failure. Information indicating whether or not an overrun has been performed, as a result of UE measurement of a neighbor cell and a serving cell of the UE when an RLF or handover failure occurs, before the handover to the cell in which the RLF or handover failure occurs Identity of the cell where the UE is located, identity of the cell where the RLF or handover failure occurred, RLF or handover failure It characterized in that of the timer (timer) between the connection of the reset time, and after the success or the connection times of success includes at least one.

According to a fifth aspect of the present invention for achieving the above object, a base station apparatus in a mobile communication system, a control unit performing a connection reset or connection establishment procedure with a terminal that has experienced an RLF or handover failure, and reports the RLF information from the terminal And a backhaul communication unit which transmits the RLF information report to the base station controlling the RLF or the cell in which the handover has occurred, wherein the RLF information report includes: before the terminal experiences an RLF or handover failure; Information indicating whether a handover has been performed, as a result of UE measurement of neighboring cells and serving cells of the UE when an RLF or handover failure occurs, before handover to a cell in which an RLF or handover failure occurs Identity of the cell in which the terminal is located, identity of the cell in which the RLF or handover failure has occurred, RLF or And at least one of a timer between the time of handover failure and the time of subsequent connection reestablishment success or connection establishment success.

According to a sixth aspect of the present invention for achieving the above object, a base station apparatus in a mobile communication system, a backhaul communication unit for receiving an RLF information report generated by a terminal that has experienced an RLF or handover failure from another base station, and the RLF And a controller for determining the cause of the RLF or the handover failure according to the information report, wherein the RLF information report includes information indicating whether the terminal has performed a handover before the RLF or the handover failure has occurred; UE measurement results for neighboring cells and serving cells of the terminal when an RLF or handover failure occurs, identification information of a cell where the terminal is located before handover to a cell where an RLF or handover failure occurs, The identity of the cell in which the RLF or handover failure occurred, the time of the RLF or handover failure, and the subsequent successful connection reset. Or at least one of a timer between time of successful connection establishment.

In the mobile communication system, the UE transmits the RLF information report including information on the RLF or handover failure to the eNB so that the eNB can correctly determine the cause of the RLF or the handover failure experienced by the UE according to the RLF information report. Thus, according to the detected cause, correct self optimization for the mobile communication system can be performed, and as a result, the performance of the mobile communication system can be improved.

1 shows a schematic structure of a conventional SAE system;
2 schematically illustrates the basic principle of self-optimization of a SAE system;
3 is a diagram illustrating a procedure for detecting a cause of an RLF or handover failure in a mobile communication system according to an embodiment of the present invention;
4A is a diagram illustrating signaling for a UE to transmit RLF or handover failure information to an eNB in a mobile communication system according to an embodiment of the present invention;
4B is a diagram illustrating signaling for a UE to transmit RLF or handover failure information to an eNB in a mobile communication system according to another embodiment of the present invention;
5 is a diagram illustrating a procedure for determining a cause of an RLF or handover failure in a mobile communication system according to an embodiment of the present invention;
6 is a block diagram of a UE in a mobile communication system according to an embodiment of the present invention;
7 is a block diagram of an eNB in a mobile communication system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, the present invention will be described a technique for detecting the cause of the RLF or handover failure. Specifically, in order for the eNB to correctly detect the cause of the RLF or handover failure determined by the UE, the UE sends an RLF information report including information on the RLF or handover failure to the eNB, whereby the eNB According to the detected cause, correct self optimization for the mobile communication system can be performed, thereby improving the performance of the mobile communication system.

For convenience of description below, the present invention uses the terms and names defined in the 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard. However, the present invention is not limited to the above terms and names, and may be equally applied to systems conforming to other standards. For example, 'UE' used in the following description may be replaced with terms such as a terminal, a user terminal, and a mobile station, and 'eNB' may be replaced with terms such as a base station and a radio access station (RAS).

Technical features according to the present invention are as follows.

The UE undergoes an RLF and handover failure (encounter). When the UE enters the connection mode, the UE sends an RLF information report to the eNB. The RLF information report may include the following information. The RLF information report is information indicating whether the UE has performed a handover before the RLF or the handover failure, UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result, the identity of the cell where the UE is located before the handover to the cell where the RLF or handover failure occurred, the identity of the cell where the RLF or handover failure occurred, the time of the RLF or handover failure, and subsequent The timer may include at least one of a timer between an RRC connection reestablishment success or an RRC connection establishment success time. In response to the RLF information report, the eNB determines whether the UE has a costly RLF or a handover failure due to too fast handover, too late handover, or because of an attempt by a wrong cell. hole).

BRIEF DESCRIPTION OF DRAWINGS To make the purpose, technical features, and gains of the present invention more clear, the present invention is described in detail below with reference to the drawings.

3 illustrates a procedure of detecting a cause of an RLF or handover failure in a mobile communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, in step 301, the UE experiences an RLF or handover failure.

Subsequently, in step 302, after the RRC connection is successfully reset or the RRC connection is successfully established, the UE proceeds to obtain information on whether the UE has recently performed a handover before the RLF or the handover failure. Send failure information to the eNB. In step 302, the failure information transmitted by the UE to the eNB in addition to whether the UE has recently performed a handover before experiencing the RLF or the handover failure, RSRP (Reference Signal Receiving Power) Measurement results for the neighbor cell of the UE and the serving cell of the UE when the RLF or the handover failure occurs, such as a reference signal reception quality (RSRQ), an enhanced cell global identity (ECGI), and a physical channel identity (PCI) Identification information of the cell where the UE is located, identification information of the cell in which the handover failure occurs, such as ECGI, PCI, or the like, before the handover to the cell in which the handover failure has occurred, the RLF or the handover It may further include at least one of a timer between the time of failure and the time of subsequent RRC connection reestablishment success or RRC connection establishment success. .

That is, the UE may determine whether the UE recently performed a handover before experiencing the RLF or the handover failure, and then, the UE indicates an indicator indicating that the UE has performed the handover. May transmit to the eNB. Alternatively, the UE directly sends a timer between the time when the UE receives the last handover command and the time when the RLF or the handover failure occurs, so that the eNB fails the RLF or the handover. Before experiencing the UE, it may be determined whether the UE has recently performed a handover.

Thereafter, in step 303, the eNB determines the cause of the RLF or the handover failure experienced by the UE according to the failure information transmitted by the UE. In step 303, the cause of the RLF or the handover failure experienced by the UE is that the UE hands over too early. This may be due to handover too late, handover to the wrong cell, or coverage hole.

After the above steps, the procedure for detecting the cause of the RLF or handover failure experienced by the UE is terminated.

FIG. 4A illustrates signaling for a UE to transmit RLF or handover failure information to an eNB in a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 4A, in step 401, the UE 410 experiences an RLF or handover failure in cell 1. The cell 1 is a cell controlled by the eNB1 421.

Accordingly, in step 402, the UE 410 performs an RRC connection reconfiguration procedure or an RRC connection establishment procedure in cell 2. The cell 2 is a cell controlled by the eNB2 422. In step 402, the UE may start the RRC connection reconfiguration procedure in the cell 2, the RRC connection reset may succeed. Alternatively, after the UE fails the RRC connection reconfiguration procedure in the cell 2, the UE may start the RRC connection establishment procedure, and the RRC connection establishment may succeed. Alternatively, the UE may fail an RRC connection reconfiguration procedure or an RRC connection establishment procedure in another cell and succeed in establishing an RRC connection in the cell 2. The RRC connection re-establishment complete message or the RRC connection establishment complete message may include an available RLF information indicator. The RLF information indicator may include information on RLF or information on handover failure.

Thereafter, in step 403, the UE 410 enters an active state, accesses an E-UTRAN system, and transmits an RLF information report to the eNB2 422. The active state may be referred to as a connection mode. The RLF information report may include the same information as included in the failure report transmitted from the UE to the eNB in step 302 of FIG. 3.

Subsequently, in step 404, the eNB2 422 transmits the RLF information report to the eNB1 421 which controls the cell in which the RLF has occurred. In step 404, the eNB2 422 finds the eNB1 421 using identification information of the cell in which the RLF or the handover failure has occurred. The RLF information is a measurement result of the neighbor cell of the UE 410 and the serving cell of the UE 410 when the RLF or the handover failure occurs, and the UE 410 detects the RLF or the handover failure. Information indicating whether a handover has been recently performed before experiencing, identification information of a cell where the UE 410 is located before handing over to the cell where the RLF or the handover failed, or a cell in which the RLF or the handover failed At least one of identification information of the RLF or the handover failure time and a subsequent RRC connection reestablishment success or RRC connection establishment success time, and identification information of a cell in which the RRC connection reset or establishment, such as ECGI, is made. It may include. The RLF information report may be a conventional RLF Indication message or a newly defined message.

In steps 403 and 404, similar to step 302 of FIG. 3, it is determined whether the UE 410 has handed over before experiencing the RLF or the handover failure, and the UE 410 The indicator indicating that the handover is performed may be transmitted to the eNB1 421. Alternatively, the UE 410 directly transmits a timer between the time when the UE 410 receives the last handover command and the time between the RLF or the time when the handover failure occurs, to the eNB1 421. Before eNB1 421 experiences the RLF or the handover failure, it may be determined whether the UE 410 has recently performed a handover.

Thereafter, in step 405, the eNB1 421 determines the cause of the RLF or the handover failure that the UE 410 has experienced. When the eNB1 421 determines that the cause of the failure is a handover that is too early or a handover to a wrong cell, the eNB1 421 may report a too-early-handover report or an incorrect cell handover report ( It is necessary to send a handover-to-wrong-cell report to the source cell (eg, the cell triggers a handover).

FIG. 4B illustrates signaling for a UE to transmit RLF or handover failure information to an eNB in a mobile communication system according to another embodiment of the present invention.

Referring to FIG. 4B, in step 451, the UE 410 experiences an RLF or handover failure in cell 1. The cell 1 is a cell controlled by the eNB1 421.

Accordingly, in step 452, the UE 410 performs an RRC connection reconfiguration procedure or RRC connection establishment in cell 2. The cell 2 is a cell controlled by the eNB2 422. In step 452, the UE starts the RRC connection reconfiguration procedure in the cell 2, and the RRC connection reconfiguration may succeed. Alternatively, after the UE fails the RRC connection reconfiguration procedure in the cell 2, the UE may start the RRC connection establishment procedure, and the RRC connection establishment may succeed. Alternatively, the UE may fail an RRC connection reconfiguration procedure or an RRC connection establishment procedure in another cell and succeed in establishing an RRC connection in the cell 2. The RRC connection re-establishment complete message or the RRC connection establishment complete message may include an available RLF information indicator. The RLF information indicator may include information on RLF or information on handover failure.

Thereafter, in step 453, when the UE 410 enters an active state and accesses an E-UTRAN system, the eNB2 422 transmits an RLF information request to the UE 410. Accordingly, in step 454, the UE 410 transmits an RLF information report to the eNB2 422. Each of the RLF information request procedure and the RLF information reporting procedure may be similar to the information request procedure and response procedure of a general UE or may be based on a newly defined RRC messaging procedure. The RLF information report may include the same information as included in the failure report transmitted from the UE to the eNB in step 302 of FIG. 3.

Subsequently, in step 455, the eNB2 422 transmits the RLF information report to the eNB1 421 which controls the cell in which the RLF has occurred. In step 455, the eNB2 422 finds the eNB1 421 using identification information of the cell in which the RLF or the handover failure has occurred. The RLF information is a measurement result of the neighbor cell of the UE 410 and the serving cell of the UE 410 when the RLF or the handover failure occurs, and the UE 410 detects the RLF or the handover failure. Information indicating whether a handover has been recently performed before experiencing, identification information of a cell where the UE 410 is located before handing over to the cell where the RLF or the handover failed, or a cell in which the RLF or the handover failed At least one of identification information of the RLF or the handover failure time and a subsequent RRC connection reestablishment success or RRC connection establishment success time, and identification information of a cell in which the RRC connection reset or establishment, such as ECGI, is made. It may include. The RLF information report may be a conventional RLF Indication message or a newly defined message.

In steps 454 and 455, similar to step 302 of FIG. 3, it is determined whether the UE 410 has handed over before experiencing the RLF or the handover failure, and the UE 410. The indicator indicating that the handover is performed may be transmitted to the eNB1 421. Alternatively, the UE 410 directly transmits a timer between the time when the UE 410 receives the last handover command and the time between the RLF or the time when the handover failure occurs, to the eNB1 421. Before eNB1 421 experiences the RLF or the handover failure, it may be determined whether the UE 410 has recently performed a handover.

In step 456, the eNB1 421 determines the cause of the RLF or the handover failure that the UE 410 has experienced. When the eNB1 421 determines that the cause of the failure is a handover that is too early or a handover to a wrong cell, the eNB1 421 may report a too-early-handover report or an incorrect cell handover report ( It is necessary to send a handover-to-wrong-cell report to the source cell (eg, the cell triggers a handover).

As described above, a procedure is performed for the UE to send RLF or handover failure information to the eNB. Upon receiving the RLF or handover failure information transmitted by the UE, the eNB accurately determines the cause of the RLF or handover failure experienced by the UE, and performs a procedure as shown in FIG. 5 below.

5 illustrates a procedure of determining a cause of an RLF or handover failure in a mobile communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 5, in step 501, the eNB determines whether the UE has performed the handover prior to the RLF or the handover failure. If the UE has not performed the handover prior to the RLF or the handover failure, the eNB proceeds to step 502 and if the UE has performed the handover prior to the RLF or the handover failure, The eNB proceeds to step 503.

Here, the eNB performs a handover before the UE experiences the RLF or handover failure through an indicator indicating whether the UE received from the UE has performed the handover prior to the RLF or the handover failure. You can see for yourself. Alternatively, the eNB may directly determine itself.

According to the timer PA between the time when the UE receives the last handover command and the time when the RLF or the handover failure occurs, the eNB determines whether the UE has performed a recent handover by determining whether the PA is greater than a threshold. It can be determined. Here, the PA indicates a time interval between the time when the UE receives the last handover command and the time when the RLF or the handover failure occurs. If the PA is greater than the threshold, this means that the UE does not perform handover. On the other hand, if the PA is less than or equal to the threshold, this means that the UE performed the handover before the connection failure.

In step 502, the eNB determines whether the RLF information report transmitted by the UE includes information on a good-signal-quality cell measured by the UE.

If the information on the good signal quality cell measured by the UE is included, in step 503, the eNB determines that the cause of the RLF or the handover failure experienced by the UE is too late handover, Quit.

If the information on the good signal quality cell measured by the UE is not included, in step 504, the eNB determines that the cause of the RLF or the handover failure experienced by the UE is a coverage hole, and performs the procedure. Quit.

In step 505, the eNB determines whether the cell having the highest signal quality is a PD cell in the UE measurement report included in the RLF report. If the cell having the highest signal quality is a PD cell, the eNB proceeds to step 508. If the cell having the highest signal quality is not a PD cell, the eNB proceeds to step 506. The PD refers to identity of a cell where the UE is located before handover to the last serving cell. For example, the PD may comprise an ECGI.

In step 506, the eNB determines whether there is another cell having a better signal quality (eg, a cell other than the RLF or the cell in which the handover failure has occurred). If there is another cell with better signal quality, the eNB proceeds to step 507 and if there is no other cell with better signal quality, the eNB proceeds to step 504.

If there is another cell with better signal quality, in step 507, the eNB determines that the cause of the RLF or the handover failure experienced by the UE is handover to the wrong cell, and terminates this procedure.

If the cell having the highest signal quality in the UE measurement report included in the RLF report is a PD cell, in step 508, the eNB determines that the cause of the RLF or the handover failure experienced by the UE is too early handover. And terminate this procedure.

As described above, a procedure in which the eNB determines the cause of the RLF or the handover failure is performed.

In the embodiment illustrated in FIG. 5, steps 501, 502, 505, and 506 mean conditions for determining a cause of an RLF or handover failure. In this case, according to another embodiment of the present disclosure, some determination conditions may be omitted. For example, if the condition of step 501 is satisfied without the determination of step 502, the eNB may proceed to step 503 and determine that the cause of the RLF or the handover failure is too late.

If the eNB determines that the UE enters the coverage hole or attempts a handover but enters the coverage hall, the eNB determines that the RLF or handover failure has occurred and the success of the subsequent RRC connection reestablishment or success of the RRC connection establishment. The size of the coverage hole may be further determined according to a timer. The eNB may perform coverage optimization.

4A, 4B, and 5 illustrate an embodiment of a method of detecting a cause of an RLF or handover failure experienced by a UE using an SAE system as an example. However, the present invention is not limited thereto and may be equally applied to other systems.

In summary, according to a method of detecting a cause of an RLF or handover failure experienced by a UE according to an embodiment of the present invention, the eNB may correctly determine the cause of the RLF or handover failure experienced by the UE according to an RLF information report. To the UE, the UE sends the RLF information report including information on the RLF or handover failure to the eNB. Accordingly, depending on the detected cause, correct self optimization for the mobile communication system can be performed. As a result, the performance of the mobile communication system can be improved.

6 is a block diagram of a UE in a mobile communication system according to an embodiment of the present invention.

As illustrated in FIG. 6, the UE includes a radio frequency (RF) processor 610, a modem 620, a storage 630, and a controller 640.

The RF processor 610 performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of the signal. That is, the RF processor 610 up-converts the baseband signal provided from the modem 620 into an RF band signal and transmits the signal through an antenna, and downlinks the RF band signal received through the antenna to the baseband signal. To convert. For example, the RF processor 610 may include an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like.

The modem 620 performs baseband signal and bit string conversion function according to the physical layer standard of the system. For example, according to an Orthgonal Frequency Division Multiplexing (OFDM) scheme, during data transmission, the modem 620 generates complex symbols by encoding and modulating a transmission bit stream, and maps the complex symbols to subcarriers. OFDM symbols are configured through Inverse Fast Fourier Transform (IFFT) operation and Cyclic Prefix (CP) insertion. In addition, upon receiving data, the modem 620 divides the baseband signal provided from the RF processor 610 into OFDM symbol units and restores signals mapped to subcarriers through a fast fourier transform (FFT) operation. After that, the received bit stream is recovered by demodulation and decoding.

The storage unit 630 stores data such as basic programs and system information for the operation of the UE. The storage unit 630 provides stored data at the request of the controller 640.

The controller 640 controls the overall function of the UE. For example, the controller 640 generates and transmits a transmission traffic packet and a message to the modem 620, and interprets the reception traffic packet and the message provided from the modem 620. In particular, according to an embodiment of the present invention, the control unit 640 provides the RLF information report when the RLF or the handover failure has occurred. For example, the controller 640 controls the UE to operate as shown in FIG. 4A or 4B. The operation of the controller 640 to provide the RLF information report is as follows.

If the RLF or the handover fails, the controller 640 enters the connected mode through a connection reset or connection establishment procedure. After entering the connected mode, the controller 640 generates an RLF information report and controls to transmit the RLF information report to a base station connected through the modem 620 and the RF processor 610. At this time, the control unit 640 transmits the RLF information report in accordance with a request from the eNB or voluntarily. Here, the RLF information report, the information indicating whether the UE has performed the handover before the RLF or handover failure, the UE for the neighbor cell and the serving cell of the UE when the RLF or handover failure occurs As a result of UE measurement, before handing over to a cell in which an RLF or handover failure occurs, identity of the cell in which the UE is located, an identity of a cell in which an RLF or handover failure occurs, an RLF or a handover And a timer between a time of failure and a time of subsequent RRC connection reestablishment success or RRC connection establishment success.

Information indicating whether the UE included in the RLF information report has performed the handover before the RLF or the handover failure has been performed is an indicator indicating whether the handover has been performed and the UE indicates the last handover command. It may include at least one of a timer between the received time and the time when the RLF or the handover failure occurs. When an indicator indicating whether the handover has been performed is included, the controller 630 determines whether the UE has performed a handover before experiencing the RLF or the handover failure, and transmits the indicator. To control. When a timer between the time when the UE receives the last handover command and the time when the RLF or the handover failure occurs, the controller 640 controls to transmit the timer.

7 is a block diagram of an eNB in a mobile communication system according to an embodiment of the present invention.

As shown in FIG. 7, the eNB includes an RF processor 710, a modem 720, a backhaul communication unit 730, a storage unit 740, and a controller 750.

The RF processor 710 performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of the signal. That is, the RF processor 710 up-converts the baseband signal provided from the modem 720 to an RF band signal and transmits the signal through an antenna, and downlinks the RF band signal received through the antenna to the baseband signal. Convert. For example, the RF processor 710 may include an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like.

The modem 720 performs a conversion function between the baseband signal and the bit string according to the physical layer standard of the system. For example, according to the OFDM scheme, during data transmission, the modem 720 generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then performs IFFT operation and CP insertion. Through OFDM symbols are configured. In addition, upon receiving data, the modem 720 divides the baseband signal provided from the RF processor 710 into OFDM symbol units, restores signals mapped to subcarriers through an FFT operation, and then demodulates and decodes the signal. Restore the received bit string through.

The backhaul communication unit 730 provides an interface for the eNB to communicate with other nodes (eg, another eNB, MME, GW, etc.). The backhaul communication unit 730 converts a bit string transmitted from the eNB to the other node into a physical signal, and converts a physical signal received from the other node into a bit string. For example, the backhaul communication unit 730 supports the X2 interface. The storage unit 740 stores data such as a basic program and system information for the operation of the eNB. The storage unit 740 provides the stored data at the request of the control unit 750.

The controller 750 controls the overall function of the eNB. For example, the controller 750 generates and transmits a transmission traffic packet and a message to the modem 720, and interprets the reception traffic packet and the message provided from the modem 720. In addition, the controller 750 generates and interprets a message for signaling with other nodes. In particular, according to an embodiment of the present invention, the controller 750 controls to transmit the RLF information report received from the UE to the eNB that controls the cell where the RLF or handover failure occurs. In addition, according to an embodiment of the present disclosure, the controller 750 receives an RLF information report on an RLF or handover failure occurring in its cell from another eNB, and determines a cause of the RLF or the handover failure. . For example, the controller 750 controls the eNB to operate like the eNB2 422 or the eNB1 421 of FIG. 4A or 4B.

The operation of the controller 750 for transmitting the RLF information report received from the UE to the eNB controlling the cell in which the RLF or the handover failure has occurred is as follows. First, the controller 750 performs a connection reset or connection establishment procedure with a UE that has experienced an RLF or handover failure, and receives an RLF information report from the UE through the RF processor 710 and the modem 720. . In this case, the controller 750 may request transmission of the RLF information report to the UE. The control unit 750 transmits the RLF information report to the base station controlling the cell in which the RLF or the handover has occurred through the backhaul communication unit 730. Here, the RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure has occurred. Furthermore, the information indicating whether the UE has performed the handover before the RLF or the handover failure has occurred includes an indicator indicating whether the handover has been performed and the time when the UE received the last handover command and the It may include at least one of an RLF or an inter-time timer in which the handover failure occurs.

The operation of the controller 750 to determine the cause of the RLF or the handover failure is as follows. The control unit 750 receives an RLF information report generated by a UE that has experienced an RLF or handover failure from another eNB through the backhaul communication unit 730, and generates an RLF or handover failure report according to the RLF information report. Determine the cause. For example, the controller 750 may be configured to perform a handover before the UE experiences an RLF or a handover failure. The controller 750 may be configured to provide a good-signal-quality cell for reporting the RLF information. If at least one of the conditions that the information is included is determined, it is determined that the cause of the RLF or the handover failure is too late handover. For example, the control unit 750, the condition that the UE has not performed the handover before the RLF or handover failure, the cell with the highest signal quality was located before the UE handover to the last serving cell If at least one of the cell conditions is satisfied, it is determined that the cause of the RLF or the handover failure is handover too early. For example, the control unit 750, the condition that the UE has not performed the handover before the RLF or handover failure, the cell with the highest signal quality was located before the UE handover to the last serving cell If at least one of the condition that is not a cell and the condition that there is another cell having a better signal quality than the cell where the handover failure occurs, the handover to the cell that caused the RLF or the handover failure is wrong Should be judged.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

Claims (28)

In the method of operation of a terminal in a mobile communication system,
Determining whether an RLF or handover failure has occurred,
Entering the connected mode through a connection reset or connection establishment procedure after experiencing the RLF or the handover failure;
After entering the connected mode, transmitting a RLF information report to a base station;
The RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure, and UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result of the UE measurement, before handing over to the cell in which the RLF or the handover failed, the identity of the cell in which the terminal is located, the identity of the cell in which the RLF or the handover failed, the RLF or the handover failure And at least one of a timer between the time and the time of subsequent connection reestablishment success or connection establishment success.
The method of claim 1,
The process of transmitting the RLF information report,
Determining whether the terminal has performed a handover before experiencing the RLF or the handover failure;
And transmitting to the base station an indicator indicating whether the handover has been performed.
The method of claim 1,
The process of transmitting the RLF information report,
And transmitting a timer between the time that the terminal receives the last handover command and the RLF or the time when the handover failure occurs to the base station.
The method of claim 1,
Prior to transmitting the RLF information report, further comprising receiving a request for transmission of the RLF information report from the base station.
In the method of operating a base station in a mobile communication system,
Performing a connection reestablishment or connection establishment procedure with a terminal having an RLF or handover failure;
Receiving an RLF information report from the terminal;
Transmitting the RLF information report to a base station controlling the cell in which the RLF or the handover has occurred,
The RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure, and UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result of the UE measurement, before handing over to the cell in which the RLF or the handover failed, the identity of the cell in which the terminal is located, the identity of the cell in which the RLF or the handover failed, the RLF or the handover failure And at least one of a timer between the time and the time of subsequent connection reestablishment success or connection establishment success.
The method of claim 5,
The information indicating whether or not the terminal has performed the handover before the RLF or the handover failure, the method comprising an indicator indicating whether the handover has been performed.
The method of claim 5,
The information indicating whether the terminal has performed the handover before the RLF or the handover failure has been included includes a timer between a time when the terminal receives the last handover command and a time when the RLF or the handover failure occurs. Characterized in that.
The method of claim 5,
Prior to receiving the RLF information report from the terminal, requesting transmission of the RLF information report to the terminal.
In the method of operating a base station in a mobile communication system,
Receiving an RLF information report generated by a terminal that has experienced an RLF or handover failure from another base station;
Determining a cause of the RLF or the handover failure according to the RLF information report,
The RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure, and UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result of the UE measurement, before handing over to the cell in which the RLF or the handover failed, the identity of the cell in which the terminal is located, the identity of the cell in which the RLF or the handover failed, the RLF or the handover failure And at least one of a timer between the time and the time of subsequent connection reestablishment success or connection establishment success.
10. The method of claim 9,
Information indicating whether the terminal has performed the handover before the RLF or handover failure,
And an indicator indicating whether the handover has been performed.
10. The method of claim 9,
Information indicating whether the terminal has performed the handover before the RLF or handover failure,
And a timer between a time when the terminal receives the last handover command and a time when the RLF or the handover failure occurs.
10. The method of claim 9,
Determining the cause of the RLF or the handover failure,
At least one of the condition that the UE has performed the handover before the RLF or the handover failure, and the condition that the RLF information report includes information on a good-signal-quality cell are satisfied. If so, the method comprising the step of determining that the cause of the RLF or the handover failure is too late handover.
10. The method of claim 9,
Determining the cause of the RLF or the handover failure,
If at least one of the condition that the terminal has not performed the handover before the RLF or handover failure, the condition that the cell having the highest signal quality is the cell where the terminal is located before the handover to the last serving cell is satisfied, Determining that the cause of the RLF or the handover failure is too early handover.
10. The method of claim 9,
Determining the cause of the RLF or the handover failure,
Condition that the UE has not performed the handover before the RLF or handover failure, condition that the cell having the highest signal quality is not the cell where the UE was located before the handover to the last serving cell, the RLF or the handover Determining that the cause of the RLF or the handover failure is a handover to a wrong cell when at least one of the conditions that there is another cell having a better signal quality than the failed cell is satisfied. Way.
A terminal device in a mobile communication system,
A controller which determines whether an RLF or handover failure occurs, enters a connected mode through a connection reset or connection establishment procedure after experiencing the RLF or the handover failure,
After entering the connected mode, including a modem for transmitting an RLF information report to the base station,
The RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure, and UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result of the UE measurement, before handing over to the cell in which the RLF or the handover failed, the identity of the cell in which the terminal is located, the identity of the cell in which the RLF or the handover failed, the RLF or the handover failure And at least one of a timer between a time and a subsequent connection reestablishment success or time of successful connection establishment.
16. The method of claim 15,
The controller determines whether the terminal performs a handover before experiencing the RLF or the handover failure,
And the modem transmits to the base station an indicator indicating whether the handover has been performed.
16. The method of claim 15,
The modem is characterized in that for transmitting the timer between the time the terminal receives the last handover command and the time when the RLF or the handover failure occurs to the base station.
16. The method of claim 15,
And the control unit is requested to transmit the RLF information report from the base station before transmitting the RLF information report.
A base station apparatus in a mobile communication system,
A control unit for performing a connection reestablishment or connection establishment procedure with a terminal having an RLF or handover failure;
A modem for receiving an RLF information report from the terminal;
A backhaul communication unit configured to transmit the RLF information report to a base station controlling the cell in which the RLF or the handover has occurred;
The RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure, and UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result of the UE measurement, before handing over to the cell in which the RLF or the handover failed, the identity of the cell in which the terminal is located, the identity of the cell in which the RLF or the handover failed, the RLF or the handover failure And at least one of a timer between a time and a subsequent connection reestablishment success or time of successful connection establishment.
20. The method of claim 19,
The information indicating whether the terminal has performed the handover before the RLF or the handover failure, the device comprising an indicator indicating whether the handover has been performed.
20. The method of claim 19,
The information indicating whether the terminal has performed the handover before the RLF or the handover failure has been included includes a timer between a time when the terminal receives the last handover command and a time when the RLF or the handover failure occurs. Device characterized in that.
20. The method of claim 19,
The control unit, before receiving the RLF information report from the terminal, characterized in that to request the transmission of the RLF information report to the terminal.
A base station apparatus in a mobile communication system,
A backhaul communication unit receiving an RLF information report generated by a terminal that has experienced an RLF or handover failure from another base station;
A control unit for determining a cause of the RLF or the handover failure according to the RLF information report,
The RLF information report includes information indicating whether the UE has performed a handover before the RLF or the handover failure, and UE measurement for the neighbor cell and the serving cell of the UE when the RLF or the handover failure occurs. As a result of the UE measurement, before handing over to the cell in which the RLF or the handover failed, the identity of the cell in which the terminal is located, the identity of the cell in which the RLF or the handover failed, the RLF or the handover failure And at least one of a timer between a time and a subsequent connection reestablishment success or time of successful connection establishment.
The method of claim 23, wherein
The information indicating whether the terminal has performed the handover before the RLF or the handover failure, the device comprising an indicator indicating whether the handover has been performed.
The method of claim 23, wherein
The information indicating whether the terminal has performed the handover before the RLF or the handover failure has been included includes a timer between a time when the terminal receives the last handover command and a time when the RLF or the handover failure occurs. Device characterized in that.
The method of claim 23, wherein
The controller may be configured to perform a handover before the UE experiences an RLF or a handover failure, and may include information about a good-signal-quality cell in the RLF information report. And if at least one is satisfied, determining that the cause of the RLF or the handover failure is too late handover.
The method of claim 23, wherein
The controller may be configured to perform at least one of a condition that the UE has not performed the handover before the RLF or the handover failure, and that the cell having the highest signal quality is the cell where the UE is located before the handover to the last serving cell. If it is satisfied, it is determined that the cause of the RLF or the handover failure is too early handover.
The method of claim 23, wherein
The control unit is a condition that the terminal has not performed the handover before the RLF or handover failure, the condition that the cell having the highest signal quality is not the cell where the terminal is located before the handover to the last serving cell, the RLF Or when the condition that at least one of the conditions exists that there is another cell having a better signal quality than the cell where the handover failure occurs, determining that the cause of the RLF or the handover failure is a handover to a wrong cell. Device.

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