Patent Publication Number: US-2013237211-A1

Title: Mobile communication method, mobile station, and radio base station

Description:
TECHNICAL FIELD 
     The present invention relates to a mobile communication method, a mobile station, and a radio base station. 
     BACKGROUND ART 
     In an LTE (Long Term Evolution) scheme, “MDT (Minimisation of Drive Tests)” is defined. Conventionally, “MDT” is a concept according to which the area quality measurement that was performed by an operator by using a radio wave measuring vehicle, etc., is substituted by a measurement report from a mobile station UE. 
     In the MDT, during the Logged MDT mode, the mobile station UE is configured to perform a measurement process of the radio quality on a visiting cell (serving cell) and a neighboring cell, and save the measurement result as a log in the memory, and then later on, report the measurement result (that is, report the log) all at one time to a radio base station eNB when a connection is established with the radio base station eNB. 
     Furthermore, if the location information is available, the mobile station UE logs the location information, together with the above measurement result, and reports the location information, together with the above measurement result, to the radio base station eNB. 
     CITATION LIST 
     Non Patent Literature 
     
         
         [NPL 1] 3GPP TS37.320 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the conventional Logged MDT mode, the mobile station UE performs nothing but measurement according to a parameter for neighboring cell measurement that is broadcasted in the visiting cell, and only logs the measurement result obtained by the measurement according to a specified logging method. 
     Here, the parameter that is broadcasted includes a predetermined threshold value S search  for a reception level (RSRP: Reference Signal Received Level) or a reception quality (RSRQ: Reference Signal Received Quality) of the visiting cell. 
     The mobile station UE needs to perform the neighboring cell measurement only when the RSRP (or the RSRQ) is below the predetermined threshold value S search . Thereby, the battery consumption can be controlled. 
     The predetermined threshold value S search  is a parameter that is broadcasted, and is also a parameter that is applied uniformly to all the mobile stations UE within the cell. In order to control the battery consumption, the value of the predetermined threshold value S search  is usually set to a low value such that the neighboring cell measurement is performed only at the cell end. 
     However, in the MDT, it is desired to be able to recognize the propagation status of various cells across a wide range, and it is also desired to be able to acquire the log of the results of neighboring cell measurements performed in a relatively broad range rather than being limited to the cell end. In this case, a problem that exists is that when the predetermined threshold value S search  is set to a low value, a sufficient log is not obtained by the MDT. 
     Thus, the present invention has been achieved in view of the above problem, and an object thereof is to provide a mobile communication method, a mobile station, and a radio base station, with which it is possible to obtain a sufficient log of measurement results with taking into consideration the battery constraints of the mobile station UE, during the Logged MDT mode. 
     Solution to Problem 
     A first characteristic of the present invention is summarized in that a mobile communication method, comprising: a step A of transmitting, by a radio base station, to a mobile station that is in a connected state in a subordinate cell, individual information including a predetermined parameter; and a step B of determining, by the mobile station, whether or not a neighboring cell measurement needs to be performed, by using a radio quality of the cell, and the predetermined parameter, when the mobile station is in an idle state. 
     A second characteristic of the present invention is summarized in that a mobile station, comprising: an individual information reception unit that receives individual information including a predetermined parameter, from a radio base station, when the mobile station is in a connected state in a cell that is subordinate to the radio base station; and a determination unit that determines whether or not a neighboring cell measurement needs to be performed, by using a radio quality of the cell, and the predetermined parameter, when the mobile station is in an idle state. 
     A third characteristic of the present invention is summarized in that A radio base station comprising: 
     an individual information transmission unit that transmits individual information including a predetermined parameter, to a mobile station that is in a connected state in a subordinate cell; and 
     a decision unit that decides the value of the predetermined parameter on the basis of at least one of capability information of the mobile station and subscriber profile information. 
     Advantageous Effects of Invention 
     As described above, according to the present invention, it is possible to provide a mobile communication method, a mobile station, and a radio base station, with which it is possible to obtain a sufficient log of measurement results with taking into consideration the battery constraints of the mobile station UE, during the Logged MDT mode. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating the entire configuration of a mobile communication system according to a first embodiment of the present invention. 
         FIG. 2  is a functional block diagram of a radio base station according to the first embodiment of the present invention. 
         FIG. 3  is a diagram illustrating an example of a format of SIB  3  used in the mobile communication system according to the first embodiment of the present invention. 
         FIG. 4  is a diagram illustrating an example of a format of “RRC Connection Release” used in the mobile communication system according to the first embodiment of the present invention. 
         FIG. 5  is a diagram illustrating an example of a format of “Logged Measurement Configuration” used in the mobile communication system according to the first embodiment of the present invention. 
         FIG. 6  is a functional block diagram of a mobile station according to the first embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Mobile Communication System According to First Embodiment of the Present Invention 
     A mobile communication system according to a first embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 6   
     The mobile communication system according to the present embodiment is an LTE mobile communication system, and includes radio base stations eNB# 1  through eNB# 3  as illustrated in  FIG. 1 . In this case, cells # 1  through # 3  are subordinate to the radio base stations eNB# 1  through eNB# 3 . 
     It is noted that because the function of the radio base stations eNB# 1  through # 3  is basically the same, hereinafter, the radio base stations eNB# 1  through # 3  are collectively called “the radio base station eNB”. 
     As illustrated in  FIG. 1 , the radio base station eNB includes a decision unit  10 , a broadcast information transmission unit  11 , and an individual information transmission unit  12 . 
     The broadcast information transmission unit  11  is configured to transmit broadcast information, such as MIB (Master Information Block) and SIB (System Information Block)  1  through  3 , in a cell subordinate to the radio base station eNB. 
     For example, as illustrated in  FIG. 3 , the broadcast information transmission unit  11  is configured to transmit SIB  3  that includes a predetermined threshold value S Search . 
     Here, if the mobile communication system according to the present embodiment is an LTE (Rel-9) mobile communication system, S IntraSearchRSRP  (“s-IntraSearchP-r9” in  FIG. 3 ), S NonIntraSearchRSRP  (“s-NonIntraSearchP-r9” in  FIG. 3 ), S IntraSearchRSRQ  (“s-IntraSearchQ-r9” in  FIG. 3 ), or S NonIntraSearchRSRQ  (“s-NonIntraSearchQ-r9” in  FIG. 3  can be set as the predetermined threshold value S Search . 
     On the other hand, if the mobile communication system according to the present embodiment is an LTE (Rel-8) mobile communication system, S IntraSearchRSRP  or S NonIntraSearchRSRP  can be set as the predetermined threshold value S Search . 
     The individual information transmission unit  12  is configured to transmit individual information such as “RRC Connection Release” and “Logged Measurement Configuration” to the mobile station UE that is in a connected state in a cell subordinate to the radio base station eNB. 
     For example, as illustrated in  FIG. 4 , the individual information transmission unit  12  may be configured to notify a predetermined parameter S Search/Dedicated  (“s-Search-r10” in  FIG. 4 ) by “RRC Connection Release”, to the mobile station UE that is in a connected state in a cell subordinate to the radio base station eNB. 
     In this case, S IntraSearchRSRP  (“s-IntraSearchP-v10x0” in  FIG. 4 ), S IntraSearchRSRQ  (“s-IntraSearchQ-v10x0” in  FIG. 4 ), S NonIntraSearchRSRP  (“s-NonIntraSearchP-v10x0” in  FIG. 4 ), or S NonIntraSearchRSRQ  (“s-NonIntraSearchQ-v10x0” in  FIG. 4 ) can be set as the predetermined parameter S Search/Dedicated . 
     Similarly, as illustrated in  FIG. 5 , the individual information transmission unit  12  may be configured to notify a predetermined parameter S Search/Dedicated  (“s-Search-r10” in  FIG. 5 ) by “Logged Measurement Configuration”, to the mobile station UE that is in a connected state in a cell subordinate to the radio base station eNB. 
     S IntraSearchRSRP  (“s-IntraSearchP-v10x0” in  FIG. 5 ), S IntraSearchRSRQ  (“s-IntraSearchQ-v10x0” in  FIG. 5 ), S NonIntraSearchRSRP  (“s-NonIntraSearchP-v10x0” in  FIG. 5 ), or S NonIntraSearchRSRQ  (“s-NonIntraSearchQ-v10x0” in  FIG. 5 ) can be set as the predetermined parameter S Search/Dedicated . 
     It must be noted that the value of the predetermined parameter S Search/Dedicated  included in “RRC Connection Release” and “Logged Measurement Configuration” may be an absolute value, or may be an offset value (differential value) for the predetermined threshold value S Search  included in SIB  3 . 
     The mobile station UE moves across a plurality of cells in an idle state, and therefore, if the value of the predetermined parameter S Search/Dedicated  is set to an offset value for the predetermined threshold value S Search , then when the predetermined threshold value S Search  that is broadcasted in each cell differs due to reasons such as the difference in the cell shape, the difference in the predetermined threshold value S Search  of each cell can be reflected. 
     The decision unit  10  is configured to decide the value of the predetermined parameter S Search/Dedicated , based on “UE Capability” and “SPID (Subscriber Profile Identifier for RAT/frequency priority)” of the mobile station UE. 
     In this case, the decision unit  10  may set such that the value of the predetermined parameter S Search/Dedicated  is larger than the predetermined threshold value S Search . 
     For example, the decision unit  10  can set the value of the predetermined parameter S Search/Dedicated  for a mobile station UE (for example, a vehicle-mounted mobile station UE and a vending machine-loaded mobile station UE) having less battery constraints, to be larger than the predetermined threshold value S Search . 
     Furthermore, the decision unit  10  can set the value of the predetermined parameter S Search/Dedicated  for a mobile station UE in which the MDT is set, to be larger than the predetermined threshold value S Search . In such a case, by notifying the predetermined parameter S Search/Dedicated  only to the mobile station UE in which the MDT is performed, and not notifying the predetermined parameter S Search/Dedicated  to the mobile station UE in which the MDT is not performed, and using the predetermined threshold value S Search , the individual information transmission unit  12  can reduce the consumption of battery in the mobile station UE in which the MDT is not performed. 
     In the LTE scheme, when the mobile station UE is in the Attached state, the “UE Capability” is notified from the mobile station UE to the mobile management node MME through the radio base station eNBE# 1 , and when the mobile station UE is in the idle state, the mobile management node MME retains the “UE Capability”. 
     Also, when the mobile station UE changes to the connected state, the mobile management node MME notifies the “UE Capability” to the radio base station eNB. 
     In this case, when the radio base station eNB cannot acquire the “UE Capability” from the mobile management node MME, the radio base station eNB can acquire the “UE Capability” from the mobile station UE. 
     Furthermore, “SPID” is the information that is notified by the mobile management node MME to the radio base station eNB, when the mobile station UE changes to the connected state. “SPID” is an index that can be used when the operator defines the terminal type and the contract type. 
     As illustrated in  FIG. 6 , the mobile station UE includes a broadcast information reception unit  21 , an individual information reception unit  22 , a determination unit  23 , a measurement unit  24 , and a Logged MDT execution unit  25 . 
     The broadcast information reception unit  21  is configured to receive the broadcast information, for example, the SIB  3  that includes the predetermined threshold value S Search , in a cell in which the mobile station UE is in an idle state. 
     The individual information reception unit  22  is configured to receive the individual information, for example, the “RRC Connection Release” and the “Logged Measurement Configuration” that include the predetermined parameter S Search/Dedicated , from the radio base station eNB# 1  that manages the cell in which the mobile station UE is in the connected state. 
     The determination unit  23  is configured to determine whether or not neighboring cell measurement (that is, the neighboring cell search and the measurement of reception level and reception quality of the detected neighboring cell) needs to be performed by using the radio quality (for example, the RSRP and the RSRQ) of a cell in which the mobile station UE is in the idle state, and the predetermined threshold value S Search  included in the SIB  3 . 
     Specifically, only when the RSRP of a cell in which the mobile station UE is in the idle state is lower than the S IntraSearchRSRP  included in the SIB  3 , the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell that is using the same frequency as the cell. 
     Alternatively, only when the RSRQ of a cell in which the mobile station UE is in the idle state is lower than the predetermined threshold value S IntraSearchRSRQ  included in the SIB  3 , the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell that is using the same frequency as the cell. 
     Furthermore, only when the RSRP of a cell in which the mobile station UE is in the idle state is lower than the predetermined threshold value S NonIntraSearchRSRP  included in the SIB  3 , the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell that is using a frequency (RAT: Radio Access Technology) different from the cell. 
     In addition, only when the RSRQ of a cell in which the mobile station UE is in the idle state is lower than the predetermined threshold value S NonIntraSearchRSRQ  included in the SIB  3 , the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell that is using a frequency (RAT) different from the cell. 
     According to the above configuration, the mobile station UE that is in an idle state in a cell subordinate to the radio base station eNB is configured to perform the neighboring cell measurement only when the radio quality of the cell is lower than the predetermined threshold value that is broadcasted by the radio base station eNB, and therefore, the consumption of battery of the mobile station UE can be reduced. 
     Furthermore, the determination unit  23  is configured to determine whether or not the neighboring cell measurement needs to be performed, by using the radio quality (for example, the RSRP or RSRQ) of the cell in which the mobile station UE is in the Idle state, and the predetermined parameter S Search/Dedicated , when a predetermined parameter S Search  is acquired by the individual information reception unit  22 . 
     When the value of the predetermined parameter S Search/Dedicated  is an absolute value, the determination unit  23  may be configured to determine whether or not the neighboring cell measurement needs to be performed, without using the predetermined threshold value S Search . 
     On the other hand, when the value of the predetermined parameter S Search/Dedicated  is an offset value for the predetermined threshold value S Search , the determination unit  23  may be configured to determine whether or not the neighboring cell measurement needs to be performed, by using the radio quality RSRP or RSRQ of the cell # 1 , the predetermined parameter S Search/Dedicated , and the predetermined threshold value S Search . 
     Specifically, only when the RSRP of a cell in which the mobile station UE is in the idle state is lower than the predetermined parameter S IntraSearchRSRP  included in the “RRC Connection Release/Logged Measurement Configuration”, the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell (for example, the cell # 2 ) that is using the same frequency as the cell. 
     Alternatively, only when the RSRQ of a cell in which the mobile station UE is in the idle state is lower than the predetermined parameter S IntraSearchRSRQ  included in the “RRC Connection Release/Logged Measurement Configuration”, the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell (for example, the cell # 2 ) that is using the same frequency as the cell. 
     Furthermore, only when the RSRP of a cell in which the mobile station UE is in the idle state is lower than the predetermined parameter S NonIntraSearchRSRP  included in the “RRC Connection Release/Logged Measurement Configuration”, the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell (for example, the cell # 3 ) that is using a frequency (RAT) different from the cell. 
     In addition, only when the RSRQ of a cell in which the mobile station UE is in the idle state is lower than the predetermined parameter S NonIntraSearchRSRQ  included in the “RRC Connection Release/Logged Measurement Configuration”, the determination unit  23  may be configured to determine that the neighboring cell measurement needs to be performed for a neighboring cell (for example, the cell # 3 ) that is using a frequency (RAT) different from the cell. 
     The measurement unit  24  is configured to perform the neighboring cell measurement based on the determination result of the determination unit  23 . Furthermore, the measurement unit  24  is configured to measure the radio quality of the cell # 1 . 
     The Logged MDT execution unit  25  is configured to execute the Logged MDT based on the measurement result by the measurement unit  24 . 
     For example, the Logged MDT execution unit  25  is configured to save, as a log, the measurement result of the radio quality (for example, the RSRP or the RSRQ) of the cell # 1  and the neighboring cells # 2  and # 3  that is measured by the measuring unit  24 , and then report a log to the radio base station eNb# 1  when the connected state occurs in the cell # 1 . 
     According to the mobile communication system of the first embodiment of the present invention, because the mobile station UE is configured to determine whether or not the neighboring cell measurement needs to be performed, by using the radio quality of the cell in which the mobile station UE is in the idle state, and the predetermined parameter S Search/dedicated  included in the “RRC Connection Release” and the “Logged Measurement Configuration”, that is, because the neighboring cell measurement (that is, the Logged MDT) need not be performed when the radio quality of the cell in which the mobile station UE is in the idle state is good, the consumption of battery can be reduced. 
     Furthermore, in the mobile communication system according to the first embodiment of the present invention, by setting the value of the predetermined parameter S Search/Dedicated  within the “RRC Connection Release/Logged Measurement Configuration” larger than the value of the predetermined threshold value S Search  within the SIB  3 , the geographical range of performing the neighboring cell measurement can be expanded, and many more Logged MDT measurement results can be acquired. 
     The reason for this is that given the property of the neighboring cell measurement, even if the measurement is not performed, no problem occurs, as long as the radio quality of a cell in which the mobile station UE is in the idle state is good; however, given the property, the Logged MDT is essentially preferred to be performed regardless of whether the radio quality of a cell in which the mobile station UE is in the idle state is good or bad. 
     The characteristics of the present embodiment as described above may be expressed as follows. 
     A first characteristic of the present embodiment is summarized as a mobile communication method that includes a step A of transmitting, by a radio base station eNB# 1 , to a mobile station UE that is in a connected state in a subordinate cell # 1 , an RRC message (individual information) including a predetermined parameter S Search/Dedicated ; and a step B of determining, by the mobile station UE, whether or not a neighboring cell measurement needs to be performed, by using a radio quality RSRP or RSRQ of the cell # 1 , and the predetermined parameter S Search/Dedicated , when the mobile station UE is in an idle state. 
     According to the first characteristic of the present embodiment, in the step B, if the value of the predetermined parameter S Search/Dedicated  is an absolute value, then even when the mobile station UE receives SIB  3  (broadcast information) that includes a predetermined threshold value S Search , from the radio base station eNB# 1 , the mobile station UE may determine whether or not the neighboring cell measurement needs to be performed, without using the predetermined threshold value S Search . 
     According to the first characteristic of the present embodiment, in the step B, if the value of the predetermined parameter S Search/Dedicated  is an offset value for the predetermined threshold value S Search  that is included in the SIB  3  received from the radio base station eNb# 1 , the mobile station UE may determine whether or not the neighboring cell measurement needs to be performed, by using the radio quality RSRP or RSRQ of the cell # 1 , the predetermined parameter S Search/Dedicated , and the predetermined threshold value S Search . 
     According to the first characteristic of the present embodiment, in the step A, the radio base station eNB# 1  may notify the predetermined parameter S Search/Dedicated , to the mobile station UE, by the “RRC Connection Release”, which is a message for releasing an RRC connection with the mobile station UE. 
     According to the first characteristic of the present embodiment, in the step A, the radio base station eNB# 1  may notify the predetermined parameter S Search/Dedicated , to the mobile station UE, by the “Logged Measurement Configuration”, which is a message for performing the Logged MDT. 
     According to the first characteristic of the present embodiment, the radio base station eNB# 1  may include a step of deciding the value of the predetermined parameter S Search/Dedicated , based on at least one of “UE Capability (Capability information of the mobile station)” and “SPID (subscriber profile information)”. 
     According to the first characteristic of the present embodiment, the value of the predetermined parameter S Search/Dedicated  may be set so as to be larger than the predetermined threshold value S Search . 
     A second characteristic of the present embodiment is summarized as a mobile station UE that includes an individual information reception unit  22  that receives an RRC message including a predetermined parameter S Search/Dedicated , from a radio base station eNB# 1 , when the mobile station UE is in a connected state in a cell # 1  that is subordinate to the radio base station eNB# 1 ; and a determination unit  23  that determines whether or not a neighboring cell measurement needs to be performed, by using a radio quality RSRP or RSRQ of the cell # 1 , and the predetermined parameter S Search/Dedicated , when the mobile station UE is in an idle state. 
     According to the second characteristic of the present embodiment, in the cell # 1 , there is provided a broadcast information reception unit  21  that receives SIB  3  including a predetermined threshold value S Search , and when the value of the predetermined parameter S Search/Dedicated  is an absolute value, the determination unit  23  may be configured to determine whether or not the neighboring cell measurement needs to be performed, without using the predetermined threshold value S Search . 
     According to the second characteristic of the present embodiment, in the cell # 1 , there is provided the broadcast information reception unit  21  that receives SIB  3  including the predetermined threshold value S Search , and when the value of the predetermined parameter S Search/Dedicated  is an offset value for the predetermined threshold value S Search , the determination unit  23  may be configured to determine whether or not the neighboring cell measurement needs to be performed, by using a radio quality RSRP or RSRQ of the cell # 1 , the predetermined parameter S Search/Dedicated , and the predetermined threshold value S Search . 
     According to the second characteristic of the present embodiment, the individual information reception unit  22  may be configured to receive an “RRC Connection Release” as the RRC message described above. 
     According to the second characteristic of the present embodiment, the individual information reception unit  22  may be configured to receive “Logged Measurement Configuration” as the RRC message described above. 
     A third characteristic of the present embodiment is summarized as a radio base station eNB# 1  that includes an individual information transmission unit  12  that transmits an RRC message including a predetermined parameter S Search/Dedicated , to a mobile station UE that is in a connected state in a subordinate cell # 1 ; and a decision unit  10  that decides the value of the predetermined parameter S Search/Dedicated  based on at least one of “UE Capability” and “SPID”. 
     According to the third characteristic of the present embodiment, in the cell # 1 , there is provided a broadcast information transmission unit  11  that transmits SIB  3  including S Search , and the decision unit  10  may set such that the value of the predetermined parameter S Search/Dedicated  is larger than the predetermined threshold value S Search . 
     In addition, the operation of the above-mentioned radio base station eNB or mobile station UE may be implemented by hardware, may also be implemented by a software module executed by a processor, or may further be implemented by the combination of the both. 
     The software module may be arranged in a storage medium of an arbitrary format such as a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and Programmable ROM), a register, a hard disk, a removable disk, or a CD-ROM. 
     The storage medium is connected to the processor so that the processor can write and read information into and from the storage medium. Such a storage medium may also be accumulated in the processor. Such a storage medium and processor may be arranged in an ASIC. The ASIC may be arranged in the radio base station eNB and the mobile station UE. Furthermore, such a storage medium and processor may be arranged in the radio base station eNB and the mobile station UE as discrete components. 
     Thus, the present invention has been explained in detail by using the above-described embodiments; however, it is obvious that for persons skilled in the art, the present invention is not limited to the embodiments explained herein. The present invention can be implemented as a corrected and modified mode without departing the gist and the scope of the present invention defined by the claims. Therefore, the description of the specification is intended for explaining the example only and does not impose any limited meaning to the present invention. 
     REFERENCE SIGNS LIST 
     
         
         eNB . . . Radio base station 
           10  . . . Decision unit 
           11  . . . Broadcast information transmission unit 
           12  . . . Individual information transmission unit 
         UE . . . Mobile station 
           21  . . . Broadcast information reception unit 
           22  . . . Individual information reception unit 
           23  . . . determination unit 
           24  . . . Measurement unit 
           25  . . . Logged MDT execution unit