JP5752083B2 - Measurement control method and user terminal - Google Patents

Description

  The present invention relates to a measurement control method and a user terminal in a mobile communication system.

  In a mobile communication system, when a building is built around a base station or the installation status of the peripheral base station of the base station changes, the radio environment related to the base station changes. For this reason, conventionally, an operator has performed a drive test in which a measurement vehicle equipped with measurement equipment is used to measure a wireless environment and collect a measurement log.

  Such measurement and collection can contribute to, for example, optimizing the coverage of the base station, but there are problems that the number of man-hours and the cost are high. Therefore, in 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, specifications of MDT (Minimization of Drive Tests) for automating the measurement and collection using a user terminal are formulated.

  As one type of MDT, there is a holding type MDT (referred to as “Logged MDT”). In the current specification, the Logged MDT is a method in which a user terminal measures a wireless state according to a measurement configuration set from a network, and stores a measurement result as a measurement log together with position information and time information (referred to as “logging”). The stored measurement log is reported to the network later.

  The current Logged MDT supports Periodic as a trigger for logging (see Non-Patent Document 1). On the other hand, Non-Patent Document 2 proposes an event trigger type logging trigger. Specifically, the user terminal holds a measurement log within a certain period (referred to as a “logging window”) before and after the timing when the wireless environment satisfies the threshold, triggered by the wireless environment satisfying the threshold.

3GPP Technical Specification “TS 37.320 V10.4.0” (2011-12) 3GPP Technical Report “TR 36.805 V9.0.0” (2009-12)

  However, since the method described in Non-Patent Document 2 has a constant time length of the logging window, if the time length is set to be short, a necessary part of the measurement log cannot be held, and the time length is set to be long. If this is done, there is a problem that unnecessary measurement logs are retained.

  Therefore, an object of the present invention is to provide a measurement control method and a user terminal that can appropriately hold a measurement log in MDT.

  In order to solve the above-described problems, the present invention has the following features.

  The measurement control method of the present invention is a measurement control method applied to a user terminal that supports MDT, and the measurement for the MDT is performed when a specific radio environment related to the user terminal satisfies a first threshold. Step A for starting log acquisition, and acquisition after Step A when the specific wireless environment satisfies the second threshold after the specific wireless environment satisfies the first threshold And B for retaining the measured log.

  The specific wireless environment may be a transmission power margin of the user terminal.

  The first threshold and the second threshold may be determined according to the maximum transmission power of the user terminal.

  The specific wireless environment may be a state of a received signal from a serving cell.

  The received signal state may be an error rate in a received signal from the serving cell.

  The first threshold and the second threshold may be determined according to a maximum error rate allowed in the lowest MCS.

  The measurement control method, when the specific wireless environment does not satisfy the first threshold before the specific wireless environment satisfies the second threshold after the specific wireless environment satisfies the first threshold, You may further have the step C which discards, without hold | maintaining the said measurement log started acquisition by the said step A.

  The step A is when the moving average of received signal power measured at the user terminal satisfies a third threshold, and when the specific radio environment satisfies the first threshold, Acquisition of a measurement log may be started.

  The first threshold value and the second threshold value may be determined by a network device.

  The measurement control method may further include a step D of continuing acquisition and holding of the measurement log until a predetermined time elapses after the specific wireless environment satisfies the second threshold.

  The predetermined time may be set to n times the time from when the specific wireless environment satisfies the first threshold to when the second threshold is satisfied.

  The user terminal of the present invention is a user terminal that supports MDT, and starts acquisition of a measurement log for the MDT when a specific wireless environment related to the user terminal satisfies a first threshold; Means for holding the measurement log started to be acquired in the step A when the specific wireless environment satisfies the second threshold after the specific wireless environment satisfies the first threshold; It is characterized by having.

  ADVANTAGE OF THE INVENTION According to this invention, the measurement control method and user terminal which can hold | maintain a measurement log appropriately in MDT can be provided.

It is a block diagram of the mobile communication system which concerns on 1st Embodiment and 2nd Embodiment. It is a block diagram of UE which concerns on 1st Embodiment and 2nd Embodiment. It is a figure for demonstrating operation | movement of the control part of UE which concerns on 1st Embodiment. It is an operation | movement flowchart of UE which concerns on 1st Embodiment. It is a figure for demonstrating the comparative example of 1st Embodiment. It is a figure for demonstrating operation | movement of the control part of UE which concerns on 2nd Embodiment (the 1). It is a figure for demonstrating operation | movement of the control part of UE which concerns on 2nd Embodiment (the 2). It is an operation | movement flowchart of UE which concerns on 2nd Embodiment.

[Outline of Embodiment]
A measurement control method according to an embodiment is a measurement control method applied to a user terminal that supports MDT, and when a specific wireless environment related to the user terminal satisfies a first threshold, Step A for starting acquisition of a measurement log, and after the specific wireless environment satisfies the first threshold, if the specific wireless environment satisfies a second threshold, the acquisition is performed in Step A. Holding the started measurement log.

  Thereby, the measurement log from when the wireless environment satisfies the first threshold to when the second threshold is satisfied can be reliably held. Therefore, regardless of whether the specific wireless environment gradually deteriorates or rapidly deteriorates, a measurement log in the process of deterioration, that is, a measurement log of a necessary part (important measurement log) Can be held.

  In addition, the measurement control method according to the embodiment continues to acquire and hold the measurement log until a predetermined time elapses after the specific wireless environment satisfies the second threshold. The predetermined time is set to n times the time from when the specific wireless environment satisfies the first threshold until the second threshold is satisfied (n> 1).

  Thereby, a measurement log can be acquired and held in a period according to the speed at which the specific wireless environment deteriorates. Therefore, regardless of whether the specific wireless environment gradually deteriorates or rapidly deteriorates, a measurement log in the process of deterioration, that is, a measurement log of a necessary part (important measurement log) Can be held.

  As described above, the measurement control method according to the embodiment can make the time length of the logging window variable, and can optimize the time length of the logging window according to the situation where the specific wireless environment deteriorates.

  Furthermore, the measurement control method according to the embodiment starts acquisition of the measurement log when the moving average of the received signal power measured by the user terminal satisfies a third threshold.

  As a result, when the deterioration of the specific wireless environment is caused by fading accompanying movement of the user terminal, that is, when it is instantaneous deterioration, the acquisition of the measurement log is not started. It is possible to retain the measurement log by eliminating the influence of.

[Embodiment]
In the following embodiments, a mobile communication system configured based on LTE (Long Term Evolution) will be described as an example.

(1) First Embodiment (1.1) Overview of Mobile Communication System FIG. 1 is a configuration diagram of a mobile communication system according to this embodiment.

  As shown in FIG. 1, a mobile communication system includes a user terminal (UE) 100, a base station (eNB: evolved Node-B) 200, a mobility management device (MME: Mobility Management Entity) / gateway device ( It has an S-GW (Serving Gateway) 300 and an operation and maintenance device (OAM: Operation and Maintenance) 400.

  The eNB 200 is a network device included in a radio access network (E-UTRAN: Evolved-UMTS Terrestrial Radio Access Network) 10. The MME / S-GW 300 and the OAM 400 are network devices included in a core network (EPC: Evolved Packet Core) 20.

  The UE 100 is a mobile radio communication device possessed by a user. The UE 100 performs wireless communication with a cell (referred to as a “serving cell”) that has established a connection in a connected state corresponding to a state during communication. The “cell” is used as a term indicating the minimum unit of the radio communication area, and is also used as a function of performing radio communication with the UE 100. Thus, the eNB 200 may be referred to as a cell.

  The eNB 200 is a fixed wireless communication device installed by a communication carrier (operator), and is, for example, a macro base station (MeNB) or a pico base station (PeNB). Alternatively, the eNB 200 may be a home base station (HeNB) that can be installed indoors. The eNB 200 forms a cell. The eNB 200 performs radio communication with the UE 100. Moreover, eNB200 transmits a reference signal for every cell.

  The eNB 200 performs communication with the EPC 20 (MME / S-GW 300) on the S1 interface that is a logical communication path with the EPC 20. The eNB 200 performs communication with the adjacent eNB 200 on the X2 interface that is a logical communication path with the adjacent eNB 200.

  The MME is provided corresponding to a control plane that handles control information, and performs various types of mobility management and authentication processing for the UE 100. The S-GW is provided corresponding to a user plane that handles user data, and performs transfer control of user data transmitted and received by the UE 100 and the like.

  The OAM 400 performs operation and maintenance of the E-UTRAN 10.

(1.2) Outline of MDT UE 100 and eNB 200 according to the present embodiment support MDT. Hereinafter, the outline of MDT will be described.

  The eNB 200 transmits, for example, an MDT setting message (MDT Configuration) for performing MDT to the UE 100 under its control in response to an instruction from the OAM 400.

  UE100 which received the MDT setting message performs the process which acquires and hold | maintains the measurement log containing the measurement result of a radio | wireless environment with a predetermined | prescribed logging trigger. Such acquisition and holding processing is called “logging”. The logging trigger may be specified in the MDT setting message.

  The wireless environment is, for example, reference signal reception power (RSRP), reference signal reception quality (RSRQ), or transmission power margin (PHR: Power Headroom). PHR is the difference between the maximum transmission power of UE 100 and the predicted transmission power used for uplink shared channel (UL-SCH) transmission.

  The measurement log includes position information obtained at that time and time information (time stamp) at the time of measurement in addition to the measurement result of the wireless environment.

  The location information is GNSS location information (detailed location information) when the UE 100 has a positioning system such as GNSS (Global Navigation Satellite System), and the RF finger when the UE 100 does not have a positioning system. Print information.

  The time information is a set of absolute time information included in the MDT setting message and relative time information measured by the UE 100.

  The UE 100 that holds the measurement log transmits information (Availability Indicator) indicating that the measurement log is held to the eNB 200 with a predetermined trigger. When acquiring the measurement log held by the UE 100, the eNB 200 transmits a measurement log transmission request (UE Information Request) to the UE 100.

  The UE 100 transmits a measurement log notification (UE Information Response) to the eNB 200 in response to the measurement log transmission request.

  The eNB 200 that has received the measurement log from the UE 100 transfers the measurement log to the OAM 400. Alternatively, the eNB 200 may use the measurement log for its own optimization.

  The OAM 400 analyzes the measurement log. For example, when the OAM 400 finds a coverage problem based on the measurement log, the OAM 400 performs network optimization for solving the found coverage problem.

(1.3) Configuration of UE FIG. 2 is a block diagram of UE 100.

  As illustrated in FIG. 2, the UE 100 includes a radio transmission / reception unit 110, a GNSS receiver 120, a storage unit 130, and a control unit 140. However, the UE 100 may not have the GNSS receiver 120.

  The wireless transmission / reception unit 110 transmits / receives a wireless signal. The GNSS receiver 120 outputs position information based on the received GNSS signal to the control unit 140. The storage unit 130 stores various information used for control by the control unit 140. The control unit 140 controls various functions of the UE 100.

  The control unit 140 receives the MDT setting message from the eNB 200, causes the parameters included in the MDT setting message to be stored in the storage unit 130, and then starts the measurement process according to MDT.

  FIG. 3 is a diagram for explaining the operation of the control unit 140 according to the present embodiment. In the present embodiment, the control unit 140 performs logging by a method that performs logging when the PHR becomes less than the threshold (referred to as “Transmit power headroom less than one threshold”). That is, in the present embodiment, the PHR corresponds to a “specific wireless environment”.

  “Transmit power headroom less than threshold” holds, for example, a measurement log in a situation where the transmission power of the UE 100 is close to the maximum transmission power and the uplink communication quality deteriorates when the UE 100 is located at the cell edge. Is. PHR means that the smaller the value, the worse the wireless environment.

  As shown in FIG. 3, the control unit 140 performs logging using two threshold values (threshold value α1 and threshold value β1) related to the logging trigger.

  The threshold value α1 is a threshold value for determining a trigger for starting acquisition of a measurement log. On the other hand, the threshold value β1 is a threshold value for determining a trigger for holding the acquired measurement log. In the present embodiment, the threshold value α1 corresponds to a first threshold value, and the threshold value β1 corresponds to a second threshold value.

  The threshold value β1 is a value smaller than the threshold value α1. The threshold α1 and the threshold β1 are determined according to the maximum transmission power of the UE 100, for example.

  The threshold value α1 and the threshold value β1 may be stored in the storage unit 130 in advance. In this case, the threshold value α1 is set to “maximum transmission power-a”, and the threshold value α2 is set to “maximum transmission power-b”.

  Alternatively, the threshold value α1 and the threshold value β1 may be specified by the MDT setting message. In this case, the network device (eNB 200 or OAM 400) determines the threshold α1 and the threshold β1, and includes the threshold α1 and the threshold β1 in the MDT setting message.

  The control unit 140 measures PHR and compares it with the threshold value α1. The control unit 140 starts obtaining the measurement log when the PHR becomes less than the threshold value α1.

  When the PHR becomes less than the threshold value β1 after the PHR becomes less than the threshold value α1, the control unit 140 causes the storage unit 130 to store the acquired measurement log.

  On the other hand, after the PHR becomes less than the threshold value α1, the control unit 140 discards the acquired measurement log without holding it when the PHR becomes equal to or more than the threshold value α1 before becoming less than the threshold value β1. .

  The control unit 140 continues to acquire and hold the measurement log (that is, logging) until a predetermined time elapses after the PHR becomes less than the threshold value β1. The predetermined time is set to n times the time from when the PHR satisfies the threshold value α1 until the threshold value β1 is satisfied (n> 1).

  As a result, the control unit 140 causes the storage unit 130 to hold measurement logs for a total period of {(α1 time to β1 time) + (β1 time−α1 time) × n}. Here, the α1 time is a time when it is determined that the PHR is less than the threshold value α1, and the β1 time is a time when it is determined that the PHR is less than the threshold value β1.

  However, the control unit 140 may continue to acquire and hold the measurement log until a certain period (fixed time length) elapses after the PHR satisfies the threshold value β1.

  Thereafter, the control unit 140 controls the radio transmission / reception unit 110 to transmit the measurement log held by the storage unit 130 to the eNB 200.

(1.4) Operation of UE according to First Embodiment FIG. 4 is an operation flowchart of the UE 100 according to the present embodiment.

  As shown in FIG. 4, in step S101, the UE 100 measures PHR and compares it with a threshold value α1.

  When the PHR is less than the threshold value α1 (step S101; Yes), in step S102, the UE 100 starts obtaining a measurement log. As described above, the measurement log includes the measurement result of the radio environment, the location information of the UE 100, and the time information at the time of measurement. The UE 100 records the time when the PHR is determined to be less than the threshold α1, that is, the measurement log acquisition start time.

  In step S103, UE100 measures PHR and compares with threshold value (beta) 1.

  When the PHR is less than the threshold β1 (step S103; No), in step S104, the UE 100 compares the PHR with the threshold α1.

  When the PHR is not less than the threshold α1 (step S104; No), in step S105, the UE 100 discards the measurement log acquired after step S102 without holding it. On the other hand, when the PHR is less than the threshold value α1 (step S104; Yes), the UE 100 returns the process to step S103.

  On the other hand, when the PHR is less than the threshold value β1 (step S103; Yes), in step S106, the UE 100 starts holding the measurement log. Here, UE100 hold | maintains the measurement log acquired after step S102. Further, the UE 100 records the time when the PHR is determined to be less than the threshold value β1, that is, the measurement log retention decision time.

  In step S107, the UE 100 has expired a period determined according to the time when the PHR is determined to be less than the threshold α1 (α1 time) and the time when the PHR is determined to be less than the threshold β1 (β1 time). Check whether or not. The period is calculated by (β1 time−α1 time) × n.

  When the said period expires (step S107; Yes), acquisition and holding | maintenance (logging) of a measurement log are complete | finished. Thereafter, the UE 100 transmits the retained measurement log to the eNB 200.

(1.5) Comparative Example FIG. 5 is a diagram for explaining a comparative example of the present embodiment. Here, a case where the PHR gradually decreases (deteriorates) is shown.

  As shown in FIG. 5, in the comparative example, the UE 100 holds a measurement log within a certain period (logging window) before and after the timing when the PHR becomes less than the threshold, triggered by the PHR becoming less than the threshold.

  In the comparative example, since the time length of the logging window is constant, the UE 100 cannot hold the measurement logs of the portions indicated by “A” and “B”. The measurement log indicated by “A” and “B” is important for the operator to analyze the behavior when the PHR is lowered.

  Thus, the method of the comparative example has a problem that an important measurement log cannot be retained.

(1.6) Summary of First Embodiment As described above, the UE 100 starts obtaining a measurement log when the PHR becomes less than the threshold value α1. The UE 100 retains the acquired measurement log when the PHR becomes less than the threshold value β1 after the PHR becomes less than the threshold value α1. Thereby, even in a case where the PHR gradually decreases, a measurement log from when the PHR becomes less than the threshold value α1 until it becomes less than the threshold value α2 can be held. Therefore, the UE 100 can maintain an important measurement log (that is, a measurement log of a portion indicated by “A” in FIG. 5).

  Further, by determining the threshold α1 and the threshold β1 according to the maximum transmission power of the UE 100, appropriate thresholds (α1 and β1) can be used for each UE 100.

  Further, the network device (eNB 200 or OAM 400) determines the threshold value α1 and the threshold value β1, so that logging according to the needs of the operator can be performed.

  In the present embodiment, after the PHR becomes less than the threshold value α1, the UE 100 discards the acquired measurement log without retaining it when the threshold value α1 is not satisfied before the PHR satisfies the threshold value β1. Thereby, since the measurement log which should be held can be reduced, the storage capacity of the UE 100 can be saved.

  In the present embodiment, the UE 100 continues to acquire and hold the measurement log (that is, logging) until a predetermined time elapses after the PHR satisfies the threshold value β1. The predetermined time is set to n times the time from when the PHR satisfies the threshold value α1 until the threshold value β1 is satisfied. As a result, even in a case where the PHR gradually decreases, the measurement log can be acquired and held in a period corresponding to the decrease rate of the PHR. Therefore, the UE 100 can maintain an important measurement log (that is, a measurement log indicated by “B” in FIG. 5).

(2) Second Embodiment Hereinafter, differences of the second embodiment from the first embodiment will be described.

  In the first embodiment described above, an example has been described in which logging is performed by “Transmit power headroom less than threshold” which is triggered by the fact that the PHR has become less than the threshold.

  In the present embodiment, logging is performed by a method of performing a trigger when the state of a received signal from a serving cell is deteriorated below a threshold value (referred to as “Serving Cell becomes worst than threshold”).

  “Serving Cell becomes worst than threshold” holds, for example, a measurement log of a situation where the received signal state of the UE 100 deteriorates and the downlink communication quality deteriorates when the UE 100 is located at the cell edge.

  In the present embodiment, the frame error rate (FER) is used as the state of the received signal from the serving cell. That is, in the present embodiment, the FER corresponds to a “specific wireless environment”. However, a bit error rate (BER) may be used instead of FER. In addition, FER means that it is a worse wireless environment, so that the value is large.

(2.1) Operation of UE according to Second Embodiment FIGS. 6 and 7 are diagrams for explaining the operation of the control unit 140 according to the present embodiment.

  As shown in FIGS. 6 and 7, the control unit 140 performs logging using three threshold values (threshold value α2, threshold value β2, and threshold value γ) related to the logging trigger. The threshold value α2 and the threshold value γ are threshold values for determining a trigger for starting acquisition of a measurement log. On the other hand, the threshold value β2 is a threshold value for determining a trigger for holding the acquired measurement log. In the present embodiment, the threshold value α2 corresponds to the first threshold value, the threshold value β2 corresponds to the second threshold value, and the threshold value γ corresponds to the third threshold value.

  The threshold value α2 and the threshold value β2 are threshold values to be compared with the FER, and the threshold value β2 is larger than the threshold value α2. The threshold value α2 and the threshold value β2 are determined according to the maximum FER at which communication is established when using a specific MCS (Modulation and Coding Scheme), for example. The specific MCS may be an MCS having the lowest data rate and the highest error resilience (that is, the lowest MCS).

  The threshold value γ is a threshold value to be compared with received signal power (RSSI: Received Signal Strength Indicator). The threshold value γ is determined according to RSSI necessary for ensuring reception quality, for example.

  The threshold value α2, the threshold value β2, and the threshold value γ may be stored in the storage unit 130 in advance.

  Alternatively, the threshold value α2, the threshold value β2, and the threshold value γ may be specified by the MDT setting message. In this case, the network device (eNB 200 or OAM 400) determines the threshold α2, the threshold β2, and the threshold γ, and includes the threshold α2, the threshold β2, and the threshold γ in the MDT setting message.

  The control unit 140 measures RSSI a plurality of times (m times), calculates an average value thereof (that is, a moving average), and compares it with the threshold value α2. When the average RSSI value is less than the threshold value γ, the control unit 140 makes the measurement log acquisition startable.

  The control unit 140 measures the FER and compares it with the threshold value α2. The control unit 140 starts acquiring the measurement log when the FER exceeds the threshold value α2.

  For example, when the threshold value α2 is set to “0%”, it is possible to start the measurement log acquisition immediately when the average RSSI value is less than the threshold value γ.

  The control unit 140 causes the storage unit 130 to retain the acquired measurement log when the FER exceeds the threshold value β2.

  On the other hand, the control unit 140 is obtained when the FER is less than or equal to the threshold value α2 before the threshold value β2 is exceeded, or when the average RSSI value is greater than or equal to the threshold value γ before the FER value exceeds the threshold value β2. Discard the stored measurement log without retaining it.

  The control unit 140 continues to acquire and hold the measurement log (that is, logging) until a predetermined time elapses after the FER exceeds the threshold value β2. The predetermined time is set to n times the time from when the FER exceeds the threshold value α2 to when it exceeds the threshold value β2 (n> 2).

  As a result, the control unit 140 causes the storage unit 130 to hold measurement logs for a total period of {(α2 time to β2 time) + (β2 time−α2 time) × n}. Here, the α2 time is a time when it is determined that the FER has exceeded the threshold value α2, and the β2 time is a time when it is determined that the FER has exceeded the threshold value β2.

  However, the control unit 140 may continue to acquire and hold the measurement log until a certain period (fixed time length) elapses after the FER satisfies the threshold value β2.

  Thereafter, the control unit 140 controls the radio transmission / reception unit 110 to transmit the measurement log held by the storage unit 130 to the eNB 200.

  FIG. 8 is an operation flowchart of the UE 100 according to the present embodiment.

  As shown in FIG. 8, in step S201, the UE 100 compares the RSSI average value with a threshold value γ.

  When the RSSI average value is less than the threshold value γ (step S201; Yes), in step S202, the UE 100 compares the FER with the threshold value α2.

  When FER exceeds less than threshold value α2 (Step S202; Yes), UE100 starts acquisition of a measurement log in Step S203. As described above, the measurement log includes the measurement result of the radio environment, the location information of the UE 100, and the time information at the time of measurement. The UE 100 records the time when it is determined that the FER has exceeded the threshold value α2, that is, the measurement log acquisition start time.

  In step S204, UE100 measures FER and compares with threshold value (beta) 2.

  When the FER is equal to or less than the threshold β2 (step S204; No), in step S205, the UE 100 compares the FER with the threshold α2, and compares the current RSSI average value with the threshold γ.

  When the FER is less than or equal to the threshold value α2 or the RSSI average value is greater than or equal to the threshold value γ (step S205; No), in step S206, the UE 100 discards the measurement log acquired after step S203 without holding it. On the other hand, when the FER exceeds the threshold value α2 and the RSSI average value is less than the threshold value γ (step S205; Yes), the UE 100 returns the process to step S204.

  On the other hand, when the FER exceeds the threshold value β2 (step S204; Yes), in step S207, the UE 100 starts holding the measurement log. Here, UE100 hold | maintains the measurement log acquired after step S203. Further, the UE 100 records the time when it is determined that the FER has exceeded the threshold value β2, that is, the measurement log retention decision time.

  In step S208, the UE 100 determines whether or not the period determined according to the time when the FER is determined to exceed the threshold value α2 (α2 time) and the time when the FER is determined to exceed the threshold value β2 (β2 time) has expired. To check. This period is calculated by (β2 time−α2 time) × n.

  When the period has expired (step S208; Yes), the UE 100 ends the acquisition and retention (logging) of the measurement log. Thereafter, the UE 100 transmits the retained measurement log to the eNB 200.

(2.2) Summary of Second Embodiment In this embodiment, in addition to the effects described in the first embodiment, the following effects can be obtained.

  Specifically, the UE 100 does not start acquisition of a measurement log unless the RSSI moving average is less than the threshold γ. Thereby, when the increase in FER is caused by fading associated with movement of the UE 100, for example, the acquisition of the measurement log can be prevented from starting, so that the influence of fading can be eliminated.

[Other Embodiments]
The descriptions and drawings forming part of this disclosure should not be construed as limiting the invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first embodiment, the case where the logging trigger is determined based on PHR has been described, and in the second embodiment, the case where the logging trigger is determined based on RSSI and FER has been described. However, not limited to PHR, RSSI, and FER, for example, RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), or the like may be used.

  In each of the above-described embodiments, the mobile communication system configured based on LTE has been described as an example. However, the present invention is not limited to LTE and is applied to other mobile communication systems (for example, W-CDMA). Also good.

  DESCRIPTION OF SYMBOLS 10 ... UTRAN, 20 ... EPC, 100 ... UE, 110 ... Radio transceiver unit, 120 ... GNSS receiver, 130 ... Storage unit, 140 ... Control unit, 200 ... eNB, 300 ... MME / GW, 400 ... OAM

Claims (12)

A measurement control method applied to a user terminal that supports MDT,
Starting acquisition of a measurement log for the MDT when a specific wireless environment related to the user terminal satisfies a first threshold;
Step B for holding the measurement log started to be acquired in Step A when the specific wireless environment satisfies the second threshold after the specific wireless environment satisfies the first threshold. When,
A measurement control method characterized by comprising:   The measurement control method according to claim 1, wherein the specific wireless environment is a transmission power margin of the user terminal.   The measurement control method according to claim 2, wherein the first threshold value and the second threshold value are determined according to a maximum transmission power of the user terminal.   The measurement control method according to claim 1, wherein the specific radio environment is a state of a received signal from a serving cell.   The measurement control method according to claim 4, wherein the received signal state is an error rate in a received signal from the serving cell.   6. The measurement control method according to claim 5, wherein the first threshold value and the second threshold value are determined according to a maximum error rate allowed in the lowest MCS.   If the specific wireless environment does not satisfy the first threshold before the specific wireless environment satisfies the second threshold after the specific wireless environment satisfies the first threshold, acquisition is performed in the step A. The measurement control method according to claim 1, further comprising a step C of discarding the started measurement log without holding the measurement log.   The step A is when the moving average of received signal power measured at the user terminal satisfies a third threshold, and when the specific radio environment satisfies the first threshold, The measurement control method according to claim 1, wherein acquisition of a measurement log is started.   The measurement control method according to claim 1, wherein the first threshold value and the second threshold value are determined by a network device.   2. The measurement control according to claim 1, further comprising a step D of continuing acquisition and holding of the measurement log until a predetermined time elapses after the specific wireless environment satisfies the second threshold. Method.   The measurement control according to claim 10, wherein the predetermined time is set to n times a time from when the specific wireless environment satisfies the first threshold to when the second threshold is satisfied. Method. A user terminal that supports MDT,
Means for starting acquisition of a measurement log for the MDT when a specific wireless environment related to the user terminal satisfies a first threshold;
Means for holding the measurement log started to be acquired in the step A when the specific wireless environment satisfies the second threshold after the specific wireless environment satisfies the first threshold; ,
A user terminal characterized by comprising:

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