JP2013143664A - Radio terminal device, communication system, communication control method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of an out-of-service condition in a radio terminal device in an idle state.SOLUTION: A radio terminal device 202 includes: a re-selecting unit 11 for executing a re-selection operation for determining in an idle state whether to continuously select as a communication partner a serving base station which is a radio base station device selected as the communication partner, or to newly select as the communication partner a peripheral base station which is another radio base station device other than the serving base station; an evaluation value calculating unit 13 for calculating an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station device; and a reception quality information creating unit 14 for creating reception quality information updated in a period shorter than the evaluation value, and indicating the reception quality of the radio signal from the serving base station. The re-selecting unit 11 uses the reception quality information when determining whether or not to execute the re-selection operation.

Description

  The present invention relates to a wireless terminal device, a communication system, a communication control method, and a communication control program, and in particular, an idle wireless terminal device becomes a communication partner based on a measurement result of a wireless signal from each wireless base station device. The present invention relates to a wireless terminal device, a communication system, a communication control method, and a communication control program in a communication system for selecting a wireless base station device.

  Conventionally, in a mobile communication system, a communication service is provided by a radio base station apparatus (hereinafter also referred to as a macro base station) that forms an area in which a cell having a radius of several hundred meters to several tens of kilometers, that is, a radio terminal apparatus can communicate. It was.

  In recent years, due to a dramatic increase in the number of subscribers of mobile communication services and an increase in the amount of communication traffic due to data communication, subscribers and communication traffic are distributed by forming smaller radius cells, and a certain level of communication It is desirable to provide speed to users in a stable manner. In addition, in order to deal with dead zones associated with the increase in the number of buildings, it is desired to install radio base station devices on the corporate floor and in ordinary households.

  Together with these demands, the processing capability of various devices used in the radio base station apparatus has been dramatically improved, and the miniaturization of the radio base station apparatus has progressed. Collecting.

  Since the radius of the femto cell (Femto Cell) formed by this small base station (hereinafter also referred to as a femto base station) is as small as about 10 meters, the femto base station is the macro cell (Macro Cell) formed by the macro base station. It may be used in places such as indoors and underground malls where it is out of service area and it is difficult to install macro base stations.

  In addition, since many femto base stations are installed in a specific area, it is difficult to connect the femto base stations directly to the core network. For this reason, it is conceivable that a large number of femto base stations installed in a specific area are once connected to a gateway device such as a HeNB-GW, and the femto base station and the core network are connected via the HeNB-GW.

  In addition to the femto base station, a pico base station that forms a pico cell having a radius of 100 to 200 meters, for example, has been developed based on a macro base station.

  Here, the cell reselection in which the idle radio terminal apparatus selects the radio base station apparatus to be a communication partner based on the measurement result of the radio signal from each radio base station apparatus is 3GPP TS 36.304. V10.3.0 2011.10 (Non-Patent Document 1).

3GPP TS 36.304 V10.3.0 2011.10

  In a heterogeneous network that is a communication system in which femto base stations, pico base stations, and macro base stations are mixed as described above, for example, a plurality of femto cells or pico cells are formed in a macro cell. For this reason, with the movement of the wireless terminal device in the idle state, the radio wave environment of the wireless terminal device may rapidly deteriorate, and the cell reselection may not be in time in the wireless terminal device, resulting in an out-of-service state.

  In this case, since the wireless terminal device is in the cell again, it is necessary to re-execute processing such as searching for the frequency of the wireless signal from the wireless base station device, and the increase in power consumption of the wireless terminal device and Various problems such as deterioration of the user's feeling occur. A technology that suppresses the occurrence of such an out-of-service state and constructs a good communication system is desired.

  This invention was made in order to solve the above-mentioned subject, The objective is the radio | wireless terminal apparatus which can suppress generation | occurrence | production of an out-of-service state in the radio | wireless terminal apparatus of an idle state, a communication system, a communication control method, and It is to provide a communication control program.

  (1) In order to solve the above problems, a radio terminal apparatus according to an aspect of the present invention is a radio terminal apparatus capable of communicating with the radio base station apparatus by transmitting and receiving radio signals to and from the radio base station apparatus. In the idle state, a serving base station that is a radio base station device selected as a communication partner is continuously selected as a communication partner, or a peripheral that is a radio base station device other than the serving base station. A reselection unit for executing a reselection operation for determining whether to newly select a base station as a communication partner, and an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station device And a received product for generating reception quality information indicating a reception quality of a radio signal from the serving base station, which is updated at a cycle shorter than the evaluation value. And an information creating unit, the re-selection section uses the reception quality information in determining whether or not to perform the reselection operation.

  In this way, the configuration for performing execution of cell reselection operation using reception quality information whose update cycle is shorter than the evaluation value makes it possible to follow a sudden change in radio wave environment, Cell reselection can be performed quickly. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  (2) Preferably, the reselection unit uses the evaluation value and the reception quality information in determining whether to execute the reselection operation.

  As described above, the configuration using the evaluation value in addition to the reception quality information for the execution determination of the cell reselection operation makes it possible to grasp the radio wave environment of the wireless terminal device in more detail and more appropriately determine the execution of the cell reselection operation. be able to.

  (3) Preferably, the wireless terminal device further measures a wireless signal from the serving base station in an idle state, and when the evaluation value of the serving base station satisfies a condition, A measurement unit for starting signal measurement, wherein the reselection unit sets the condition based on the reception quality information, and measurement of a radio signal from the neighboring base station by the measurement unit is started Whether to continue to select the serving base station as a communication partner based on at least the evaluation value of the neighboring base station, or to newly select the neighboring base station as a communication partner. Judging.

  With such a configuration, it is possible to appropriately set measurement start conditions for neighboring cells in accordance with the reception quality of the wireless terminal device and to appropriately determine whether to perform a cell reselection operation.

  (4) More preferably, the reselection unit sets the condition so that the measurement start of the radio signal from the neighboring base station by the measurement unit is accelerated when the reception quality indicated by the reception quality information is deteriorated.

  With such a configuration, it is possible to speed up the start of measurement of neighboring cells in accordance with the deterioration of the reception quality of the wireless terminal device, so that information for determining whether to perform cell reselection follows the rapid change in the radio wave environment. Can be acquired quickly.

  (5) More preferably, in the idle state, when the reception quality indicated by the reception quality information is bad, the measurement unit receives a radio signal from the neighboring base station if the evaluation value of the serving base station satisfies a condition. Start measuring.

  With such a configuration, the neighboring cell measurement start condition using the evaluation value of the serving base station can be set at an appropriate timing according to the degradation of the reception quality of the wireless terminal device.

  (6) Preferably, the radio terminal device further includes a measurement unit for starting measurement of radio signals from the neighboring base stations when the condition is satisfied in an idle state, and the reselection unit receives the reception The above condition is set based on quality information, and when the measurement of the radio signal from the neighboring base station by the measurement unit is started, the reselection operation is started, and at least based on the evaluation value of the neighboring base station , It is determined whether to continue to select the serving base station as a communication partner or to newly select the neighboring base station as a communication partner.

  With such a configuration, without measuring the neighboring cell measurement start based on the evaluation value of the serving base station, the measurement of the neighboring cell is started by detecting the degradation of the reception quality of the wireless terminal device based on the reception quality information, Cell reselection to neighboring cells can be performed quickly.

  (7) More preferably, the reselection unit sets the condition based on the reception quality information and a time elapsed since the reception quality information was updated.

  As described above, the configuration in which the update elapsed time of the information indicating the radio wave environment of the wireless terminal device is used as the measurement start condition of the neighboring cell suppresses misjudgment due to old information, and more appropriately determines whether to perform measurement of the neighboring cell. be able to.

  (8) More preferably, the reselection unit sets the condition based on the reception quality information for a plurality of times.

  With such a configuration, it is possible to suppress misjudgment caused by an instantaneous change in the radio wave environment and more appropriately perform execution judgment of measurement of neighboring cells.

  (9) Preferably, the reception quality information creation unit communicates with the radio base station apparatus, transmitted from the radio base station apparatus in a process for allowing the own radio terminal apparatus to be in the radio base station apparatus. The reception quality information is created in an idle state in accordance with an instruction included in the information for establishing a connection.

  With such a configuration, the information transmitted from the radio base station apparatus can be diverted in the process for allowing the radio terminal apparatus to be in the cell, and the idle radio terminal apparatus can create reception quality information. it can.

  (10) Preferably, the reception quality information creation unit communicates with the radio base station apparatus, transmitted from the radio base station apparatus in a process for allowing the own radio terminal apparatus to be in the radio base station apparatus. The reception quality information is created in the idle state in accordance with an instruction included in the information for releasing the connection.

  With such a configuration, the information transmitted from the radio base station apparatus can be diverted in the process for allowing the radio terminal apparatus to be in the cell, and the idle radio terminal apparatus can create reception quality information. it can.

  (11) A radio terminal apparatus according to another aspect of the present invention can communicate with the radio base station apparatus by transmitting and receiving radio signals to and from the radio base station apparatus, and according to a communication protocol having a plurality of layers. An operating wireless terminal apparatus, wherein a first measurement for acquiring first measurement information based on a measurement result in an idle state of a wireless signal from a wireless base station apparatus according to a first layer of the plurality of layers Acquire second measurement information based on a measurement result in an idle state of a radio signal from a radio base station device according to an information acquisition unit and a second layer lower than the first layer among the plurality of layers. The second measurement information acquisition unit for the communication base station in the idle state and the serving base station that is the radio base station apparatus selected as the communication partner And a reselecting unit for executing a reselection operation for determining whether to select a neighboring base station that is a radio base station apparatus other than the serving base station as a communication partner. The selection unit uses the second measurement information acquired by the second measurement information acquisition unit in determining whether to execute the reselection operation.

  In this way, in the communication protocol, the configuration for performing the cell reselection operation execution determination using lower layer information can reduce the acquisition time of information for the cell reselection operation execution determination, A quick and appropriate execution decision of cell reselection can be made. That is, since it is possible to follow a sudden change in the radio wave environment, cell reselection to a neighboring cell can be performed quickly, and the occurrence of an out-of-service state of the wireless terminal device can be suppressed. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  (12) Preferably, the first layer is an RRC (Radio Resource Control) layer defined by 3GPP (Third Generation Partnership Project), and the second layer is a MAC (Media Access) defined by 3GPP. Control) layer and / or PHY (Physical) layer.

  With such a configuration, it is possible to suppress the occurrence of an out-of-service state in the idle state by appropriately performing execution determination of the cell reselection operation in the wireless terminal device that operates in accordance with the communication protocol defined in 3GPP. .

  (13) In order to solve the above-described problem, a communication system according to an aspect of the present invention includes a radio base station that transmits and receives radio signals between a plurality of radio base station apparatuses and the radio base station apparatus. A wireless communication system comprising: a wireless terminal device capable of communicating with a device, wherein the wireless terminal device continues in the idle state with a serving base station that is a wireless base station device selected as a communication partner as a communication partner; A reselection unit for performing a reselection operation for determining whether to select or newly select a neighboring base station other than the serving base station as a communication partner, and a radio base station apparatus An evaluation value calculation unit for calculating an evaluation value of at least one of reception power and reception quality of a radio signal from the radio signal, and updated in a cycle shorter than the evaluation value, A reception quality information creation unit for creating reception quality information indicating reception quality of a radio signal from a base station, wherein the reselection unit determines whether to perform the reselection operation. Use information.

  In this way, the configuration for performing execution of cell reselection operation using reception quality information whose update cycle is shorter than the evaluation value makes it possible to follow a sudden change in radio wave environment, Cell reselection can be performed quickly. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  (14) A communication system according to another aspect of the present invention is capable of communicating with the radio base station apparatus by transmitting and receiving radio signals between the plurality of radio base station apparatuses and the radio base station apparatus. , A communication system comprising a wireless terminal device that operates according to a communication protocol having a plurality of layers, and according to a first layer of the plurality of layers, a measurement result in an idle state of a wireless signal from a wireless base station device A first measurement information acquisition unit for acquiring the first measurement information based on the idle signal of the radio signal from the radio base station device according to a second layer lower than the first layer among the plurality of layers. A second measurement information acquisition unit for acquiring second measurement information based on a measurement result in a state, and a radio base selected as a communication partner in an idle state A reselection operation for determining whether to continuously select a serving base station as a communication partner as a communication partner or to newly select a neighboring base station as a communication partner other than the above serving base station as a communication partner. A reselection unit for executing the reselection unit, and the reselection unit uses the second measurement information acquired by the second measurement information acquisition unit in determining whether to execute the reselection operation.

  In this way, in the communication protocol, the configuration for performing the cell reselection operation execution determination using lower layer information can reduce the acquisition time of information for the cell reselection operation execution determination, A quick and appropriate execution decision of cell reselection can be made. That is, since it is possible to follow a sudden change in the radio wave environment, cell reselection to a neighboring cell can be performed quickly, and the occurrence of an out-of-service state of the wireless terminal device can be suppressed. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  (15) In order to solve the above-described problem, a communication control method according to an aspect of the present invention provides a radio terminal apparatus capable of communicating with the radio base station apparatus by transmitting and receiving radio signals to and from the radio base station apparatus. And calculating an evaluation value of at least one of reception power and reception quality of a radio signal from a radio base station device in an idle state, and in an idle state with a cycle shorter than the evaluation value. The step of creating reception quality information indicating the reception quality of the radio signal from the serving base station which is the updated radio base station apparatus selected as the communication partner, and continuing the serving base station as the communication partner in the idle state Or select a neighboring base station other than the serving base station as a communication partner. Reselection operation to determine whether the to run, and a step of using the reception quality information in determining whether or not to perform the reselection operation.

  In this way, the configuration for performing execution of cell reselection operation using reception quality information whose update cycle is shorter than the evaluation value makes it possible to follow a sudden change in radio wave environment, Cell reselection can be performed quickly. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  (16) In order to solve the above-described problem, a communication control program according to an aspect of the present invention provides a radio terminal device capable of communicating with the radio base station device by transmitting and receiving radio signals to and from the radio base station device. A communication control program for use in a computer, wherein the computer calculates an evaluation value of at least one of reception power and reception quality of a radio signal from a radio base station apparatus in an idle state; and in the idle state, the evaluation value Generating reception quality information indicating a reception quality of a radio signal from a serving base station which is a radio base station apparatus selected as a communication partner and updated in a shorter cycle, and in the idle state, the serving base station Continuously as a communication partner, or with a radio base station device other than the serving base station. For executing a reselection operation for determining whether or not a neighboring base station to be newly selected as a communication partner and using the reception quality information in determining whether to execute the reselection operation. It is.

  In this way, the configuration for performing execution of cell reselection operation using reception quality information whose update cycle is shorter than the evaluation value makes it possible to follow a sudden change in radio wave environment, Cell reselection can be performed quickly. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the out-of-service state in the wireless terminal device in an idle state can be suppressed.

It is a figure which shows the structure of the communication system which concerns on embodiment of this invention. It is a figure which shows an example of the condition where movement operation | movement is performed in the communication system which concerns on embodiment of this invention. It is a figure which shows an example of the sequence of the cell reselection in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the parameter which the radio | wireless terminal apparatus which concerns on embodiment of this invention uses in S value calculation and S value determination. It is a figure which shows an example of the measurement result of the serving cell in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the structure of the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the control part in the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the cell reselection in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the sequence of the cell reselection which considered CQI in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the attach process in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the tracking area update process in the radio | wireless communications system which concerns on embodiment of this invention. It is the flowchart which defined an example of the procedure of radio wave environment degradation judgment by the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is the flowchart which defined an example of the procedure of radio wave environment degradation judgment by the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is the flowchart which defined an example of the procedure of radio wave environment degradation judgment by the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is a figure which shows a response | compatibility with each layer in a communication protocol and S value and CQI by the radio | wireless terminal apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  The radio base station apparatus notifies the radio terminal apparatus of information about the cell and the neighboring cell that it forms, that is, the frequency of the radio signal and the ID (identification) of the neighboring cell. The wireless terminal device detects and measures neighboring cells based on information notified from the wireless base station device. The wireless terminal device starts moving to the neighboring cell based on the measurement result. Here, “movement” of the wireless terminal device means not only handover but also through which cell the wireless terminal device in an idle state starts communication in the future, that is, when a call or data communication is started. This means selecting whether to perform communication.

  For example, when the wireless terminal device is communicating with the wireless base station device, the destination of the wireless terminal device is determined by the wireless base station device or a higher-level device in the core network. For example, when the wireless terminal device is not communicating with the wireless base station device, the wireless terminal device determines the destination of the wireless terminal device.

  In addition, handover means that a radio base station apparatus serving as a communication destination of a radio terminal apparatus during a call or data communication is switched.

  The “idle state” of a wireless terminal device is a state in which a wireless base station device has selected a wireless base station device as a communication partner and is not communicating with the wireless base station device. In addition, the “state in which communication is not performed” is a state in which an operation for transmitting some information to the radio base station apparatus is not performed.

  Note that the definition of “Idle Mode” defined in 3GPP may be used as the definition of the “idle state” of the wireless terminal device.

  The wireless terminal device is located in a cell means that the wireless terminal device selects a wireless base station device forming the cell as a communication partner and can communicate with the wireless base station device. This means that communication is in progress.

  Specifically, for example, “in-service area” of a wireless terminal device means a state in which a higher-level device of the wireless base station device registers that the wireless terminal device has moved to a new cell, that is, the wireless base station device. .

  Further, “located” includes a state in which a higher-level device has registered the update of the tracking area to which the wireless terminal device belongs.

  That is, when the wireless terminal apparatus moves to a new cell, if the tracking area where the wireless terminal apparatus exists, that is, the paging process target area changes, the wireless terminal apparatus executes a tracking area update process.

  The femtocell and access mode are described in 3GPP (Third Generation Partnership Project) SPEC TS 22.22 as follows. That is, a femto base station is a customer premises apparatus that connects a wireless terminal device connected via a wireless interface to a mobile communication carrier network using an IP backhaul.

  Further, in the femtocell access mode, the femto base station in the closed access mode provides a service only to related CSG (Closed Subscriber Group) members. The hybrid mode femto base station also provides services to the associated CSG members and CSG non-members. The femto base station in the open access mode operates as a normal base station.

  Such a 3GPP definition may also be applied to the wireless communication system according to the embodiment of the present invention.

  Further, the following definitions can be applied together with or separately from the above definitions.

  The macro base station and the pico base station are wireless base station devices that are under the management of the operator and can communicate with the wireless base station device that has contracted with the operator. Further, it is considered that the macro base station and the pico base station are basically not turned off.

  A femto base station is a radio base station apparatus that is installed mainly in an individual or corporate building and may move or be turned off depending on the circumstances of the user.

  Further, the femto base station operates in one of open / hybrid / closed access modes. When the femto base station operates in the closed access mode, only registered members (terminals) can be connected. When operating in the closed access mode, the service is provided only to registered members. When operating in the hybrid mode, the service is provided to both registered members and unregistered members, that is, non-members. When operating in the open access mode, the same operation as that of the macro base station and the pico base station is performed.

[Configuration and basic operation]
FIG. 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention.

  Referring to FIG. 1, a communication system 401 is a mobile communication system that complies with, for example, LTE (Long Term Evolution) standardized by 3GPP, and includes radio base station apparatuses 101A, 101B, and 101C. In FIG. 1, three radio base station apparatuses are representatively shown, but a larger number of radio base station apparatuses may be provided. The communication system 401 further includes an S-GW (Serving Gateway) 161, an MME (Mobility Management Entity) 162, and a P-GW (Packet Data Network Gateway) 163 provided in the core network 301.

  The wireless terminal device 202 establishes a communication connection with a server or the like in the IP network 302 via the wireless base station device 101A, the wireless base station device 101B, or the wireless base station device 101C, the S-GW 161, and the P-GW 163, For example, communication data including an IP (Internet Protocol) packet is transmitted / received.

  More specifically, the wireless base station devices 101A, 101B, and 101C communicate with the wireless terminal device 202 by transmitting and receiving wireless signals to and from the wireless terminal device 202.

  The S-GW 161 is connected between the radio base station apparatuses 101A, 101B, and 101C and the IP network 302. The S-GW 161 transmits communication data received from the wireless terminal device 202 via the wireless base station devices 101A, 101B, and 101C to the IP network 302 via the P-GW 163, and from the server in the IP network 302 via the P-GW 163. The communication data received in (1) is transmitted to the wireless terminal device 202 via the wireless base station devices 101A, 101B, 101C.

  The MME 162 manages the radio base station apparatuses 101A, 101B, 101C, the radio terminal apparatus 202, and the like in the communication system 401. The MME 162 transmits and receives control messages to and from the radio base station apparatuses 101A, 101B, and 101C.

  The radio base station apparatuses 101A, 101B, and 101C transmit / receive communication data to / from the IP network 302 via the S-GW 161 and the P-GW 163.

  The radio base station apparatuses 101A, 101B, 101C and the S-GW 161 exchange various data with each other via the S1-U interface by transmitting and receiving communication data according to the S1-U interface which is a logical interface.

  The radio base station apparatuses 101A, 101B, 101C and the MME 162 transmit and receive communication data according to the S1-MME interface, which is a logical interface, to each other via the S1-MME interface, as indicated by dotted lines. Communicate.

  The MME 162 and the S-GW 161 exchange various data with each other via the S11 interface by transmitting and receiving communication data according to the S11 interface which is a logical interface.

  The S-GW 161 and the P-GW 163 exchange various kinds of information with each other via the S5 interface by transmitting and receiving communication data according to the S5 interface which is a logical interface.

  FIG. 2 is a diagram illustrating an example of a situation where a mobile operation is performed in the communication system according to the embodiment of the present invention.

  Referring to FIG. 2, radio base station apparatuses 101A, 101B, and 101C are, for example, femto base stations, pico base stations, or macro base stations.

  The radio base station apparatus 101A can communicate with the radio terminal apparatus 202 by forming a cell CA and transmitting and receiving radio signals to and from the radio terminal apparatus 202 existing in the cell CA. The radio base station apparatus 101B can communicate with the radio terminal apparatus 202 by forming a cell CB and transmitting and receiving radio signals to and from the radio terminal apparatus 202 existing in the cell CB. The radio base station apparatus 101C can communicate with the radio terminal apparatus 202 by forming a cell CC and transmitting and receiving radio signals to and from the radio terminal apparatus 202 existing in the cell CC.

  Here, the direction from the wireless terminal device 202 to the core network 301 is referred to as an uplink direction, and the direction from the core network 301 to the wireless terminal device 202 is referred to as a downlink direction.

  Further, the movement-source radio base station apparatus of the radio terminal apparatus 202 is also referred to as a serving base station, and the movement-destination radio base station apparatus is also referred to as a target base station. Hereinafter, a case where the radio base station apparatus 101A is a serving base station and the radio base station apparatus 101B is a target base station will be described.

  The radio base station apparatus and the radio terminal apparatus in the communication system according to the embodiment of the present invention read and execute a program including each step of the following sequences from a memory (not shown). This program can be installed externally. The installed program is distributed in a state stored in a recording medium, for example.

  In the radio base station apparatus according to the embodiment of the present invention, power measurement processing (Measurement) is used for determining whether to perform cell reselection. This power measurement process corresponds to RRC (Radio Resource Control) of the layer 3 stack in 3GPP, for example.

  Here, in 3GPP TS36.133 4.2.2.1, the measurement period of the serving cell for cell reselection is described as follows. That is, the wireless terminal device 202 measures the RSRP (Reference Signal Received Power) level of the serving cell at least every DRX (Discontinuous Reception) cycle, and the S value (Cell Selection Criterion S) defined in TS36.304 and the RSRP level. And compare.

  The radio | wireless terminal apparatus 202 filters the measurement result of a serving cell by at least 2 times of measurement. This filtering is considered averaging.

  Of the above-described measurement sets to be filtered, at least two measurements must be performed with an interval of at least 1/2 of the DRX cycle. This is considered to mean that the measurement interval must be ½ or more of the DRX cycle.

  Here, in Table 4.2.2.1-1 of 3GPP TS36.133 4.2.2.1, the correspondence relationship between the DRX cycle length [seconds] and the DRX cycle number Nserv is shown. Specifically, when the DRX cycle length is 0.32 seconds, 0.64 seconds, 1.28 seconds, and 2.56 seconds, the DRX cycle number Nserv is 4, 4, 2, and 2, respectively.

  If the serving cell does not satisfy the S value in Nserv consecutive DRX cycles, the wireless terminal device 202 is designated by the serving base station unless its measurement function is restricted by some restrictions. Start measuring all neighboring cells. That is, if a certain period of time elapses, the wireless terminal device 202 starts measuring neighboring cells even if the S value does not satisfy the condition.

  From the description of 3GPP TS36.133, at least 0.16 seconds (160 ms) is required as the measurement period of the serving cell, and the determination of the S value as described above requires at least two measurements. For this reason, an interval of substantially 0.32 seconds (320 ms) or more is necessary for determining the measurement start of the neighboring cells.

  Further, when the measurement of the neighboring cell is started in a state where the S value does not satisfy the condition, an interval of 0.32 seconds × 4 times = 1.28 seconds is necessary for the judgment of the measurement start of the neighboring cell.

  In 3GPP TS36.133 4.2.2.1, only RSRP is described, but since RSRQ (Reference Signal Receive Quality) is also measured according to RRC, it is considered to be the same as RSRP.

  First, cell reselection by the radio terminal apparatus according to the embodiment of the present invention will be described in detail.

  Cell reselection is processing performed when the radio terminal apparatus 202 moves from a serving cell formed by a serving base station to a neighboring cell formed by a neighboring base station in an idle state. The cell reselection is performed under the initiative of the radio terminal apparatus 202, and is normally performed without the radio base station apparatus 101 giving a specific instruction to the radio terminal apparatus 202.

  FIG. 3 is a diagram showing an example of a cell reselection sequence in the radio communication system according to the embodiment of the present invention.

  Here, as shown in FIG. 2, the case where the wireless terminal device 202 is located in the cell CA and moves to the overlapping area of the cell CA and the cell CB after selecting the wireless base station device 101A as a communication partner. Suppose.

  Referring to FIG. 3, first, when wireless terminal apparatus 202 determines to newly select wireless base station apparatus 101A as a communication partner, it receives broadcast information transmitted from wireless base station apparatus 101A (step S1). ), The content of the received notification information is stored (step S2). This broadcast information includes neighboring cell information and information for performing cell reselection.

  Next, in order to notify the MME 162 or the like in the core network 301 that the wireless terminal apparatus 202 has moved to a new cell CA, the wireless terminal apparatus 202 executes an attach process (Attach Procedure) that is a terminal registration process (step S3).

  Next, the wireless terminal device 202 starts measuring the received power of the wireless signal transmitted from the wireless base station device 101A that is a serving base station. That is, the wireless terminal device 202 measures the reception power of the serving cell. For example, the wireless terminal device 202 measures received power using a pilot signal included in the wireless signal. As described above, this measurement cycle is, for example, 0.16 seconds (step S4).

  Next, the wireless terminal device 202 calculates an S value, which is an evaluation value of the serving cell, and performs S value determination (step S5).

  When the S value of the serving cell satisfies the predetermined condition (YES in step S5), the radio terminal apparatus 202 measures the received power of the radio signal transmitted from the neighboring base station indicated by the broadcast information at the frequency indicated by the broadcast information. To start. That is, the radio | wireless terminal apparatus 202 measures the reception power of a periphery cell in addition to a serving cell. For example, the wireless terminal device 202 measures received power using a pilot signal included in the wireless signal (step S6).

  Next, the wireless terminal device 202 calculates an S value that is an evaluation value of a neighboring cell, and performs S value determination (step S7).

  When the S value of the neighboring cell satisfies the predetermined condition (step S8), the wireless terminal device 202 ranks the serving cell and the neighboring cell, for example, in the order of good reception power quality using the measurement result of the serving cell and the neighboring cell. (Step S8).

  Next, as a result of the ranking, if the highest cell is not the serving cell (YES in step S9), the wireless terminal device 202 performs cell reselection to the highest cell. That is, radio terminal apparatus 202 determines to newly select a radio base station apparatus corresponding to the highest neighboring cell, for example, radio base station apparatus 101B, as a communication partner. And the radio | wireless terminal apparatus 202 receives the alerting | reporting information from the wireless base station apparatus 101B (step S10), and preserve | saves the content of the received alerting | reporting information (step S11).

  Next, in order to notify the MME 162 and the like in the core network 301 that the wireless terminal device 202 has moved to a new cell CB, the wireless terminal device 202 executes an attach process that is a terminal registration process (step S12).

  For example, the wireless terminal device 202 performs computation and processing related to the S value according to the method described in 3GPP TS36.304 or the like. Hereinafter, this content will be described in detail.

The wireless terminal device 202 does not select a cell that does not satisfy a certain level in the measurement result of the wireless signal from the wireless base station device 101, specifically, a cell that does not satisfy the following formula (A1) as a communication partner. To work.
Srxlev> 0 and Squal> 0 (A1)

Here, Srxlev and Squal are expressed by the following equations.
Srxlev = Qrxlevmeas− (Qrxlevmin + Qrxlevminoffset) −Pcompensation
Squal = Qqualmeas- (Qqualmin + Qqualminoffset)

  FIG. 4 is a diagram illustrating an example of parameters used in the S value calculation and the S value determination by the wireless terminal device according to the embodiment of the present invention. FIG. 4 summarizes the contents of 3GPP TS36.304 and the like.

  Referring to FIG. 4, Srxlev (Cell selection RX level value [dB]) is a reception level value for cell selection. Squal (Cell selection quality value [dB]) is a reception quality value for cell selection. Qrxlevmeas (Measured cell RX level value) is RSRP (Reference Signal Received Power), that is, the received power value of the cell. Qqualmeas (Measured cell quality value) is RSRQ (Reference Signal Receive Quality), that is, the reception quality value of the cell. Qrxlevmin (Minimum required RX level in the cell [dBm]) is a minimum reception level required in the cell. Qqualmin (Minimum required quality level in the cell [dB]) is a minimum reception quality level required in the cell. Qrxlevminoffset (Offset to the signaled Qrxlevmin) is defined in 3GPP TS 23.122 as shown in FIG. 4 and is an offset for adjusting the reception level. Qqualminoffset (Offset to the signaled Qqualmin) is defined in 3GPP TS 23.122 as shown in FIG. 4 and is an offset for adjusting the reception quality level. Pcompensation is max (PEMAX_H−PPowerClass, 0) [dB]. PEMAX_H (Maximum TX power level [dBm]) is defined in TS 36.101 as shown in FIG. 4 and is the maximum transmission power level. PPowerClass (Maximum RF output power of the UE [dBm]) is defined in TS 36.101 as shown in FIG. 4 and is the maximum RF output power.

[Starting Criteria for Surrounding Cell Measurement]
In the case of the same frequency cell (intra-frequency cell), that is, when the frequency of the radio signal transmitted by the serving cell and the neighboring cell is the same, the wireless terminal device 202 determines that the S value of the serving cell is expressed by the following equation (B1). When it is satisfied, the peripheral cell is measured.
Srxlev ≦ SIntraSearchP or Squal ≦ SIntraSearchQ (B1)

  Here, SIntraSearchP and SIntraSearchQ are positive values. That is, the wireless terminal device 202 starts measuring neighboring cells before the serving cell becomes in a state that does not satisfy the formula (A1).

  Further, the wireless terminal device 202 is a case of an inter-frequency cell, that is, a case where the frequencies of wireless signals transmitted by the serving cell and the neighboring cells are different, and the priority of each cell is determined by the broadcast information. When the priority of the neighboring cell is higher than the priority of the serving cell given to the device 202, the neighboring cell is measured regardless of the state of the serving cell. In this case, the cell reselection operation taking into account CQI (Channel Quality Indication) described later, that is, the determination of the start of neighboring cell measurement according to equation (B2) is out of scope.

  On the other hand, when the priority of the neighboring cell is lower than the priority of the serving cell, or when the priority of the serving cell and the priority of the neighboring cell are equal, the same standard as in the case of the same frequency cell as described above is followed. , Measure peripheral cells.

  This priority is, for example, for a mobile communication carrier to set a cell that the wireless terminal device 202 wants to preferentially select in the communication system.

  Further, the radio terminal apparatus 202 is the same as the case of the different frequency cell as described above when the cell (Inter-RAT Cell) of different radio access schemes, that is, when the radio access schemes of the serving cell and the neighboring cells are different. The peripheral cells are measured according to the standard.

[Criteria for cell reselection]
First, the criteria for performing cell reselection to a different frequency cell or a cell of a different radio access scheme will be described.

  The wireless terminal apparatus 202 changes the execution criteria for cell reselection to neighboring cells according to the priority of each cell. That is, when the priority of the neighboring cell is higher than that of the serving cell and the wireless terminal device 202 is given the following thresholds for reception quality (hereinafter also referred to as “ThreshX-Q”), the following conditions are satisfied. If the condition is satisfied, cell reselection to the neighboring cells is performed.

  That is, when one second or more has passed since the wireless terminal device 202 has been in the serving cell (Camp) and the measurement result of the neighboring cell satisfies Squal> ThreshX, HighQ during the TreselectionRAT, Cell reselection to the neighboring cell is performed. Here, the condition of “1 second or more has elapsed” is to prevent a state in which cell reselection is repeatedly performed in a short time.

  In addition, when the priority of the neighboring cell is higher than that of the serving cell and no ThreshX-Q is given, the wireless terminal device 202 performs cell reselection when the following condition is satisfied.

  That is, when the wireless terminal device 202 has been in the serving cell for more than 1 second and the measurement result of the neighboring cell satisfies Srxlev> ThreshX, HighP during the ReselectionRAT, Cell reselection.

  In addition, when the priority of the neighboring cell is lower than that of the serving cell and the ThreshX-Q is given, the wireless terminal device 202 performs cell reselection when the following condition is satisfied.

  That is, more than 1 second has elapsed since the wireless terminal device 202 has been in the serving cell, the measurement result of the serving cell satisfies Squal <ThreshServing, LowQ, and the measurement result of the surrounding cell is Squall> ThreshX during TreselectionRAT. , When LowQ is satisfied, cell reselection from the serving cell to the neighboring cell is performed.

  On the other hand, when the priority of the neighboring cell is lower than that of the serving cell, and the ThreshX-Q is not given, the wireless terminal device 202 performs cell reselection when the following condition is satisfied.

  That is, more than 1 second has elapsed since the wireless terminal device 202 has been in the serving cell, the measurement result of the serving cell satisfies Srxlev <ThreshServing, LowP, and the measurement result of the neighboring cell is Srxlev> ThreshX during TreselectionRAT. , If LowP is satisfied, cell reselection from the serving cell to the neighboring cell is performed.

  In addition, when the priority of the neighboring cell is the same as that of the serving cell, the wireless terminal device 202 follows the same standard as when performing cell reselection to the same frequency cell as described below.

  Radio terminal apparatus 202 performs cell reselection to a cell with higher priority when a plurality of cells with different priorities satisfy the cell reselection criteria as described above.

  Next, criteria for performing cell reselection to the same frequency cell, a different frequency cell having the same priority as the serving cell, and a cell of a radio access scheme having the same priority as the serving cell will be described. In the following, the subscripts “s” and “n” represent a serving cell and a neighboring cell, respectively.

In 3GPP, a criterion (Criterion Rs, Rn) for cell ranking is defined for a serving cell and neighboring cells. The wireless terminal device 202 ranks cells using these Rs and Rn, for example. Rs and Rn are represented by the following formulas.
Rs = Qmeas, s + QHyst
Rn = Qmeas, n−Qoffset

  Here, Qmeas is the received power quality. Further, in the case of cell reselection to the same frequency cell, Qoffset is equal to Qoffsets, n if the offset value Qoffsets, n is valid, and zero if not valid. Here, Qoffsets, n is “valid” means that Qoffsets, n is given to the wireless terminal device 202 by broadcast information or the like.

  Further, in the case of cell reselection to a different frequency cell, Qoffset is equal to Qoffsetfrequency if Qoffsets, n is valid (Qoffsets, n + Qoffsetfrequency), and otherwise. Here, Qoffsetfrequency is an offset value set for each radio frequency.

  Radio terminal apparatus 202 ranks cells based on Rs and Rn, and performs cell reselection to the highest cell when the following condition is satisfied for the highest cell.

  That is, when one second or more has elapsed since the wireless terminal device 202 was in the serving cell, and the highest cell is ranked higher than the serving cell during the Reselection RAT, Cell reselection to the upper cell is performed.

  Note that the wireless terminal device 202 may be configured to perform ranking only for neighboring cells, except for the serving cell, in the ranking.

[Cell reselection issues]
As described above, in the cell reselection operation of the wireless terminal device 202, in order to start measurement of neighboring cells having a priority equal to or lower than the serving cell, or neighboring cells of the same frequency, measurement of the serving cell is performed first, The measurement result of the serving cell needs to satisfy a predetermined condition. For this reason, if the wireless environment suddenly deteriorates during measurement of the serving cell, the wireless terminal device 202 may go out of service without performing measurement of neighboring cells or cell reselection to neighboring cells.

  FIG. 5 is a diagram illustrating an example of a measurement result of the serving cell in the wireless communication system according to the embodiment of the present invention.

  In FIG. 5, the horizontal axis represents time, and the vertical axis represents radio wave intensity. SVC is the radio field intensity of the serving cell, that is, the reception power at the wireless terminal device 202 of the wireless signal transmitted by the serving base station. In FIG. 5, for the sake of simplicity, it is assumed that SIntraSearchP and SIntraSearchQ have the same value.

  Referring to FIG. 5, it is assumed that wireless terminal apparatus 202 starts serving cell measurement at timing T1, and periodically obtains measurement results, for example, at timings T2 and T4.

  For example, when the radio wave environment of the wireless terminal device 202 rapidly deteriorates between the timing T2 and the timing T4, the measurement result indicating that the radio wave environment has deteriorated, that is, the measurement result in which the S value of the serving cell satisfies the formula (B1) is the timing. Obtained at T4. However, before the timing T3 before the timing T4, the wireless terminal device 202 becomes out of service or before the cell reselection to the neighboring cell is performed at the timing T5 after the timing T4. May be out of range.

  Therefore, the wireless terminal device according to the embodiment of the present invention solves the above problems by the following configuration and operation.

[Wireless terminal device]
FIG. 6 is a diagram showing a configuration of the wireless terminal apparatus according to the embodiment of the present invention.

  Referring to FIG. 6, the wireless terminal device 202 includes an antenna 81, a circulator 82, a wireless reception unit 83, a wireless transmission unit 84, a signal processing unit 85, a control unit 88, and an input / output unit 89. Prepare. The signal processing unit 85 includes a reception signal processing unit 86 and a transmission signal processing unit 87. The signal processing unit 85 and the control unit 88 are realized by a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like.

  Circulator 82 outputs the radio signal received from antenna 81 from radio base station apparatus 101 to radio reception unit 83, and outputs the radio signal received from radio transmission unit 84 to antenna 81.

  Radio receiving section 83 converts the radio signal received from circulator 82 into a baseband signal or IF (Intermediate Frequency) signal, converts the frequency-converted signal into a digital signal, and outputs the digital signal to received signal processing section 86.

  The received signal processing unit 86 performs signal processing such as FFT (Fast Fourier Transform) in the OFDM (Orthogonal Frequency Division Multiplex) method on the digital signal received from the wireless receiving unit 83, and outputs one of the digital signals after the signal processing. Part or all of the data is output to the control unit 88.

  The control unit 88 converts the digital signal received from the reception signal processing unit 86 into, for example, audio data and video data, and converts it into an analog signal as necessary. And the control part 88 outputs to the input-output part 89 containing a speaker, a microphone, a display, a key input device, etc.

  Further, the control unit 88 receives, for example, voice data and a control signal for controlling the wireless terminal device 202 received by the key input device from the input / output unit 89. Control unit 88 performs predetermined signal processing on the audio data and control signal received from input / output unit 89 to generate communication data, and outputs the communication data to transmission signal processing unit 87.

  The transmission signal processing unit 87 performs signal processing such as spreading processing in the CDMA (Code Division Multiple Access) system on the communication data received from the control unit 88 or communication data generated by itself, and the digital signal after this signal processing Is output to the wireless transmission unit 84.

  The wireless transmission unit 84 converts the digital signal received from the transmission signal processing unit 87 into an analog signal, converts the frequency of the converted analog signal into a wireless signal, and outputs the radio signal to the circulator 82.

  FIG. 7 is a diagram showing a configuration of a control unit in the radio terminal apparatus according to the embodiment of the present invention.

  Referring to FIG. 7, control unit 88 includes reselection unit 11, measurement unit 12, evaluation value calculation unit (first measurement information acquisition unit) 13, and reception quality information creation unit (second measurement information acquisition unit). 14).

  The evaluation value calculation unit 13 calculates evaluation values of received power and reception quality of radio signals from the radio base station apparatus 101, such as Srxlev and Squal, respectively. The evaluation value calculation unit 13 may be configured to calculate one of Srxlev and Squal.

  The reception quality information creation unit 14 is updated at a cycle shorter than the evaluation value, and creates reception quality information such as CQI indicating the reception quality of the radio signal from the serving base station.

  The reselection unit 11 continuously selects the serving base station, which is the radio base station apparatus 101 selected as the communication partner, in the idle state of its own radio terminal apparatus 202 as the communication partner, or other than the serving base station A cell reselection operation is performed to determine whether a neighboring base station, which is another radio base station apparatus 101, is newly selected as a communication partner.

  The reselection unit 11 uses the reception quality information in determining whether to perform the cell reselection operation.

  That is, in the radio terminal apparatus according to the embodiment of the present invention, information updated at a cycle shorter than the received power information, for example, 3GPP, by using a CQI report that can be reported at a cycle of 5 milliseconds at the shortest. The possibility of the wireless terminal device 202 going out of service is reduced. The CQI report corresponds to MAC (Medium Access Control) or PHY (Physical Layer) of the layer 2 stack.

The CQI report does not directly report the current radio wave condition in each cell, but is a value expressed in 16 levels from 0 to 15 using the following equation using SINR. When CQI = 0, the reception quality of the wireless terminal device 202 is the worst, and when CQI = 15, the reception quality of the wireless terminal device 202 is the best.
CQI = min (max (round ((SINR [dB] +8) /1.892), 0), 15)

  For example, the reselection unit 11 uses the evaluation value and the reception quality information in determining whether to perform the cell reselection operation.

  More specifically, the measurement unit 12 measures a radio signal from the serving base station in the idle state, and starts measuring radio signals from neighboring base stations when the evaluation value of the serving base station satisfies the condition.

  The reselection unit 11 sets the above condition based on the reception quality information. Then, the reselection unit 11 starts the cell reselection operation when the measurement of the neighboring base station is started, and continues to select the serving base station as a communication partner based on at least the evaluation value of the neighboring base station. Then, it is determined whether or not a neighboring base station is newly selected as a communication partner.

  That is, the radio | wireless terminal apparatus 202 performs CQI measurement in parallel with the measurement of a serving cell. As a result, when the radio wave environment of the serving cell deteriorates, measurement of the neighboring cell can be started without waiting for the measurement result of the serving cell, so that cell reselection to the neighboring cell can be performed before going out of service. It becomes possible.

Specifically, the wireless terminal device 202 performs measurement of the neighboring cell when the following formula (B2) including the CQI measurement result is added to the formula (B1) that is the measurement start condition of the neighboring cell. .
Srxlev ≦ SIntraSearchP or Squal ≦ SIntraSearchQ + α × (CQI−β) (B2)

  In this conditional expression, the smaller the CQI, the easier the cell reselection is performed. That is, the reselection unit 11 sets the measurement start condition for the neighboring base station so that the measurement start of the radio signal from the neighboring base station by the measurement unit 12 is accelerated when the reception quality indicated by the reception quality information is deteriorated.

  Radio terminal apparatus 202 may adjust α and β in equation (B2) based on, for example, the number of out-of-service states.

  FIG. 8 is a diagram showing an example of cell reselection in the radio communication system according to the embodiment of the present invention. In FIG. 8, NBC is the radio field intensity of the neighboring cell, that is, the received power of the radio signal transmitted from the neighboring base station at the radio terminal device 202. Other views are the same as in FIG. In FIG. 8, as in FIG. 5, SIntraSearchP and SIntraSearchQ are assumed to be the same value for the sake of simplicity.

  Referring to FIG. 8, it is assumed that wireless terminal apparatus 202 starts serving cell measurement at timing T11 and periodically obtains measurement results, for example, at timings T12 and T14.

  From the timing T11 to the timing T12, the radio terminal 202 receives the radio wave environment from the CQI at the timing T13 when the radio wave intensity of the serving cell gradually decreases and the radio wave intensity of the surrounding cells gradually increases and the difference between the two decreases to some extent. Detect deterioration of the cell and start measuring neighboring cells.

  Thereby, before the radio | wireless terminal apparatus 202 will be in an out-of-service state, cell re-selection to a periphery cell is performed in timing T14.

  FIG. 9 is a diagram showing an example of a cell reselection sequence in consideration of CQI in the wireless communication system according to the embodiment of the present invention.

  Referring to FIG. 9, first, when wireless terminal apparatus 202 determines to newly select wireless base station apparatus 101A as a communication partner, it receives broadcast information transmitted from wireless base station apparatus 101A (step S21). ), The content of the received notification information is stored (step S22). This broadcast information includes neighboring cell information and information for performing cell reselection.

  Next, in order to notify the MME 162 and the like in the core network 301 that the wireless terminal apparatus 202 has moved to a new cell CA, the wireless terminal apparatus 202 executes an attach process that is a terminal registration process (step S23).

  Next, the wireless terminal device 202 stores information for performing CQI measurement acquired from the wireless base station device 101, for example, in the attach process (step S24).

  Next, the wireless terminal device 202 starts measuring the received power of the wireless signal transmitted from the wireless base station device 101A that is a serving base station. That is, the wireless terminal device 202 measures the reception power of the serving cell. For example, the wireless terminal device 202 measures received power using a pilot signal included in the wireless signal. As described above, this measurement cycle is, for example, 0.16 seconds (step S25).

  Next, the wireless terminal device 202 starts CQI measurement (step S26).

  Next, the wireless terminal device 202 calculates the S value, which is the evaluation value of the serving cell, and performs S value determination (step S27).

  When the S value of the serving cell satisfies the predetermined condition, that is, formula (B2) that takes CQI into account (B2) (YES in step S27), radio terminal apparatus 202 uses the frequency indicated by the broadcast information from the neighboring base station indicated by the broadcast information. Measure the received power of the transmitted radio signal. That is, the radio | wireless terminal apparatus 202 measures the reception power of a periphery cell in addition to a serving cell. For example, the wireless terminal device 202 measures received power using a pilot signal included in the wireless signal (step S28).

  Next, the wireless terminal device 202 calculates an S value, which is an evaluation value of a neighboring cell, and performs S value determination (step S29).

  When the S value of the neighboring cell satisfies the predetermined condition (YES in step S29), the wireless terminal apparatus 202 ranks the serving cell and the neighboring cell in the order of good reception power quality, for example, using the measurement result of the serving cell and the neighboring cell. (Step S30).

  Next, when the highest order cell is not the serving cell as a result of the ranking (YES in step S31), the wireless terminal device 202 performs cell reselection to the highest order cell. That is, radio terminal apparatus 202 determines to newly select a radio base station apparatus corresponding to the highest neighboring cell, for example, radio base station apparatus 101B, as a communication partner. And the radio | wireless terminal apparatus 202 receives the alerting | reporting information from the wireless base station apparatus 101B (step S32), and preserve | saves the content of the received alerting | reporting information (step S33).

  Next, in order to notify the MME 162 and the like in the core network 301 that the wireless terminal device 202 has moved to a new cell CB, the wireless terminal device 202 executes an attach process that is a terminal registration process (step S34).

  The wireless terminal device 202 may be configured to use the formula (B2) or the formula (B1) after confirming that the CQI has deteriorated to some extent.

  That is, when the reception quality indicated by the reception quality information is poor in the idle state, for example, after the CQI becomes less than a predetermined threshold, the measurement unit 12 determines that the evaluation value of the serving base station is the formula (B2) or the formula (B1). When conditions such as the above are satisfied, measurement of radio signals from neighboring base stations is started.

  Here, in LTE, radio terminal apparatus 202 cannot perform CQI measurement alone. That is, radio terminal apparatus 202 can perform CQI measurement only after receiving an instruction to start CQI measurement from radio base station apparatus 101 when an RRC connection is established.

  Here, when the radio terminal apparatus 202 newly resides in a cell, it is necessary to perform either or both of an attach process and a tracking area updating procedure (to perform these processes). For this, it is necessary to establish an RRC connection.

  Using this, in the radio communication system according to the embodiment of the present invention, radio base station apparatus 101 instructs radio terminal apparatus 202 to start CQI measurement when an RRC connection is established. As a result, wireless terminal apparatus 202 can perform CQI measurement in an idle state.

  That is, the reception quality information creating unit 14 transmits the radio base station apparatus 101 transmitted from the radio base station apparatus 101 in a process for the own radio terminal apparatus 202 to be in the cell, that is, the radio base station apparatus 101. The reception quality information is created in the idle state according to the instruction included in the information for establishing the communication connection.

  FIG. 10 is a diagram showing an attach process in the wireless communication system according to the embodiment of the present invention. FIG. 10 is a sequence diagram showing in detail the operation of step S23 or step S34 in FIG.

  Referring to FIG. 10, when radio terminal apparatus 202 determines that radio base station apparatus 101 should be selected as a new communication partner, radio terminal apparatus 202 issues an RRC (Radio Resource Control) connection request (RRC Connection Request) to radio base station. It transmits to the station apparatus 101 (step S71).

  Next, the radio base station apparatus 101 receives an RRC connection request from the radio terminal apparatus 202, and transmits RRC connection information (RRC Connection Setup) to the radio terminal apparatus 202 (step S72).

  Next, the radio | wireless terminal apparatus 202 receives RRC connection information from the radio base station apparatus 101, and transmits a RRC connection completion notification (RRC Connection Setup Complete) (step S73).

  Next, the radio base station apparatus 101 receives an RRC connection completion notification from the radio terminal apparatus 202 and transmits an attach request received from the radio terminal apparatus 202 to the MME 162. This attach request is included in an RRC connection completion notification from the wireless terminal device 202, for example. The attach request is information transmitted to request communication permission from the MME 162 because the wireless terminal device 202 wants to newly move to a certain cell (step S74).

  Next, MME 162 transmits an authentication request (Authentication Request) to radio base station apparatus 101 (step S75).

  Next, the radio base station apparatus 101 transmits downlink information to the radio terminal apparatus 202. This downlink information includes, for example, authentication request information from the MME 162 (step S76).

  Next, the wireless terminal device 202 transmits uplink information to the wireless base station device 101. This uplink information includes, for example, authentication response information to the MME 162 (step S77).

  Next, the radio base station apparatus 101 transmits an authentication response to the authentication request received from the MME 162 to the MME 162 (step S78).

  Next, the MME 162 transmits security information (NAS Security Mode Command) to the radio base station apparatus 101 as security processing of a NAS (Non-Access Stratum) layer (step S79).

  Next, the radio base station apparatus 101 transmits downlink information to the radio terminal apparatus 202 (step S80).

  Next, the wireless terminal device 202 transmits uplink information to the wireless base station device 101 (step S81).

  Next, the radio base station apparatus 101 transmits a security completion notification (NAS Security Mode Complete) for the security information received from the MME 162 to the MME 162 (step S82).

  Next, the MME 162 receives a security completion notification from the radio base station apparatus 101, and transmits an attach acceptance to the radio base station apparatus 101 (step S83).

  Next, the radio base station apparatus 101 receives the attach acceptance from the MME 162, and transmits security information (Security Mode Command) to the radio terminal apparatus 202 (step S84).

  Next, the wireless terminal device 202 receives the security information from the wireless base station device 101, and transmits a security completion notification (Security Mode Complete) to the wireless base station device 101 (step S85).

  Next, the radio base station apparatus 101 transmits an RRC (Radio Resource Control) connection reconfiguration instruction (RRC Connection Reconfiguration) to the radio terminal apparatus 202 (step S86).

  Next, the wireless terminal device 202 transmits an RRC connection reconfiguration completion notification (RRC Connection Reconfiguration Complete) to the wireless base station device 101 (step S87).

  Next, the radio base station apparatus 101 receives an RRC connection reconfiguration completion notification from the radio terminal apparatus 202 and transmits an attach completion notification (Attach Complete) (step S88).

  Next, the MME 162 receives an attachment completion notification from the radio base station apparatus 101, and transmits a terminal information release instruction (UE Context Release Command) to the radio base station apparatus 101 (step S89).

  Next, the radio base station apparatus 101 receives a terminal information release instruction from the MME 162 and transmits an RRC connection release request (RRC Connection Release) to the radio terminal apparatus 202. Thereby, the radio | wireless terminal apparatus 202 will be in an idle state (step S90).

  Next, the radio base station apparatus 101 transmits a terminal information release completion notification (UE Context Release Complete) to the MME 162 (step S91).

  FIG. 11 is a diagram showing a tracking area update process in the wireless communication system according to the embodiment of the present invention. FIG. 11 is a sequence diagram showing in detail the operation of step S23 or step S34 in FIG.

  Referring to FIG. 11, when radio terminal apparatus 202 determines that radio base station apparatus 101 should be selected as a new communication partner, radio terminal apparatus 202 issues an RRC (Radio Resource Control) connection request (RRC Connection Request) to radio base station. It transmits to the station apparatus 101 (step S41).

  Next, the radio base station apparatus 101 receives an RRC connection request from the radio terminal apparatus 202, and transmits RRC connection information (RRC Connection Setup) to the radio terminal apparatus 202 (step S42).

  Next, the radio | wireless terminal apparatus 202 receives RRC connection information from the radio base station apparatus 101, and transmits a RRC connection completion notification (RRC Connection Setup Complete) (step S43).

  Next, the radio base station apparatus 101 receives the RRC connection completion notification from the radio terminal apparatus 202 and transmits the tracking area update request received from the radio terminal apparatus 202 to the MME 162. This tracking area update request is included, for example, in the RRC connection completion notification from the wireless terminal device 202. The tracking area update request is information transmitted to request communication permission from the MME 162 because the wireless terminal device 202 wants to newly move to a certain cell (step S44).

  Next, MME 162 transmits an authentication request (Authentication Request) to radio base station apparatus 101 (step S45).

  Next, the radio base station apparatus 101 transmits downlink information to the radio terminal apparatus 202. This downlink information includes, for example, authentication request information from the MME 162 (step S46).

  Next, the wireless terminal device 202 transmits uplink information to the wireless base station device 101. This uplink information includes, for example, authentication response information to the MME 162 (step S47).

  Next, the radio base station apparatus 101 transmits an authentication response to the authentication request received from the MME 162 to the MME 162 (step S48).

  Next, the MME 162 transmits security information (NAS Security Mode Command) to the radio base station apparatus 101 as security processing of a NAS (Non-Access Stratum) layer (step S49).

  Next, the radio base station apparatus 101 transmits downlink information to the radio terminal apparatus 202 (step S50).

  Next, the wireless terminal device 202 transmits uplink information to the wireless base station device 101 (step S51).

  Next, the radio base station apparatus 101 transmits a security completion notification (NAS Security Mode Complete) for the security information received from the MME 162 to the MME 162 (step S52).

  Next, the MME 162 receives a security completion notification from the radio base station apparatus 101, and transmits a tracking area update accept (Tracking Area Update Accept) to the radio base station apparatus 101 (step S53).

  Next, the radio base station apparatus 101 receives the tracking area update acceptance from the MME 162, and transmits security information (Security Mode Command) to the radio terminal apparatus 202 (step S54).

  Next, the wireless terminal device 202 receives security information from the wireless base station device 101, and transmits a security completion notification (Security Mode Complete) to the wireless base station device 101 (step S55).

  Next, the radio base station apparatus 101 transmits an RRC (Radio Resource Control) connection reconfiguration instruction (RRC Connection Reconfiguration) to the radio terminal apparatus 202 (step S56).

  Next, the wireless terminal device 202 transmits an RRC connection reconfiguration completion notification (RRC Connection Reconfiguration Complete) to the wireless base station device 101 (step S57).

  Next, the radio base station apparatus 101 receives the RRC connection reconfiguration completion notification from the radio terminal apparatus 202 and transmits a tracking area update completion notification (Tracking Area Update Complete) (step S58).

  Next, the MME 162 receives the tracking area update completion notification from the radio base station apparatus 101, and transmits a terminal information release instruction (UE Context Release Command) to the radio base station apparatus 101 (step S59).

  Next, the radio base station apparatus 101 receives a terminal information release instruction from the MME 162 and transmits an RRC connection release request (RRC Connection Release) to the radio terminal apparatus 202. Thereby, the radio | wireless terminal apparatus 202 will be in an idle state (step S60).

  Next, the radio base station apparatus 101 transmits a terminal information release completion notification (UE Context Release Complete) to the MME 162 (step S61).

  Regarding messages between the MME 162 and the radio base station apparatus 101, the terminal information release instruction and the terminal information release completion notification are messages according to the S1AP protocol, and all other messages are messages according to the NAS (MME) protocol.

  In the attach process and tracking area update process, RRC connection information is transmitted from the radio base station apparatus 101 to the radio terminal apparatus 202. This RRC connection information includes information necessary for measuring the CQI and transmitting the CQI report to the radio base station apparatus 101, for example, “cqi-ReportConfig” which is an IE (Information Element).

  Radio terminal apparatus 202 performs CQI measurement based on this information after transitioning to the idle state.

  In addition, by adding the IE to the RRC connection release request transmitted when the radio base station apparatus 101 releases the RRC connection with the radio terminal apparatus 202, the radio base station apparatus 101 is explicitly in the idle state. It may be configured to promote CQI measurement.

  More specifically, the radio base station apparatus 101 instructs the radio terminal apparatus 202 to start CQI measurement when the RRC connection is released after completion of the attach process or tracking area update process. As a result, wireless terminal apparatus 202 can perform CQI measurement in an idle state.

  That is, the reception quality information creating unit 14 transmits the radio base station apparatus 101 transmitted from the radio base station apparatus 101 in a process for the own radio terminal apparatus 202 to be in the cell, that is, the radio base station apparatus 101. The reception quality information is created in the idle state according to the instruction included in the information for releasing the communication connection.

[Other setting examples of peripheral cell measurement start conditions]
In the wireless terminal device according to the embodiment of the present invention, the CQI is added to the conditional expression for starting measurement of neighboring cells defined in 3GPP TS36.304. However, the present invention is not limited to this.

  That is, the wireless terminal device 202 is not limited to the configuration that corrects the equation (B1) by CQI, and may determine measurement start of neighboring cells by CQI alone, or by combining CQI and other information. Cell measurement start determination may be performed.

  That is, the measurement unit 12 starts measuring radio signals from neighboring base stations when the condition is satisfied in the idle state.

  The reselection unit 11 sets the above condition based on the reception quality information. Then, the reselection unit 11 starts the cell reselection operation when the measurement of the neighboring base station is started, and continues to select the serving base station as a communication partner based on at least the evaluation value of the neighboring base station. Then, it is determined whether or not a neighboring base station is newly selected as a communication partner.

  Hereinafter, a specific example in which the deterioration of the radio wave environment is detected and the measurement start determination of the neighboring cells is performed from the CQI will be described.

  For example, the wireless terminal device 202 makes a measurement start determination for neighboring cells using the CQI without using the S value. More specifically, the wireless terminal device 202 determines whether to start measurement of neighboring cells based on the CQI calculated by the reception quality information creation unit 14.

  FIG. 12 is a flowchart defining an example of a procedure for determining deterioration of the radio wave environment by the wireless terminal device according to the embodiment of the present invention.

  Referring to FIG. 12, radio terminal apparatus 202 monitors the CQI output from reception quality information creation unit 14. If CQI is equal to or greater than a predetermined threshold (NO in step S201), radio terminal apparatus 202 has its own radio wave environment. It is determined that there is no deterioration, and CQI is continuously monitored.

  On the other hand, when the CQI falls below a predetermined threshold (YES in step S201), the wireless terminal device 202 determines that its own radio wave environment has deteriorated, and starts measuring neighboring cells (step S202).

  Further, for example, the reselection unit 11 sets the measurement start conditions for the radio signals from the neighboring base stations based on the reception quality information and the time elapsed since the reception quality information was updated.

  FIG. 13 is a flowchart defining an example of a procedure for determining deterioration of the radio wave environment by the wireless terminal device according to the embodiment of the present invention.

Referring to FIG. 13, radio terminal apparatus 202 monitors CQI, measures the CQI update elapsed time, and determines deterioration of the radio wave environment according to the following determination formula.
A (T_CQI) × CQI <threshold

  However, A is an arbitrary value. The determination formula is a function of CQI and update elapsed time.

  That is, the wireless terminal device 202 adjusts A according to the elapsed time T_CQI from the timing when the CQI was last updated. Specifically, the wireless terminal device 202 sets the weight of the old information small in the determination formula. That is, the wireless terminal device 202 sets A smaller as the elapsed time T_CQI is larger.

  If the determination formula is not satisfied (NO in step S221), the wireless terminal device 202 determines that its own radio wave environment has not deteriorated and continues to monitor the CQI.

  On the other hand, when the determination formula is satisfied (YES in step S221), the wireless terminal device 202 determines that its own radio wave environment has deteriorated, and starts measuring neighboring cells (step S222).

  Further, for example, the reselection unit 11 sets the measurement start condition for the radio signal from the neighboring base station based on the reception quality information for a plurality of times. Specifically, the reselection unit 11 sets measurement start conditions based on a plurality of times of CQI statistical data.

  FIG. 14 is a flowchart defining an example of a procedure for determining deterioration of the radio wave environment by the wireless terminal device according to the embodiment of the present invention.

Referring to FIG. 14, radio terminal apparatus 202 monitors CQI output from reception quality information creation unit 14, evaluates CQI by performing statistical processing, for example, average processing, on multiple times of CQI, and degrades radio wave environment. Judging. The wireless terminal device 202 determines the deterioration of the radio wave environment, for example, according to the following determination formula.
ΣCQI (t) <threshold

  Radio terminal apparatus 202 is not limited to the above-described determination formula, and may use difference information {CQI (t + 1) −CQI (t)}, for example.

  If the determination formula is not satisfied (NO in step S251), the wireless terminal device 202 determines that its own radio wave environment has not deteriorated and continues to monitor CQI.

  On the other hand, when the determination formula is satisfied (YES in step S251), the wireless terminal device 202 determines that its own radio wave environment has deteriorated, and starts measuring neighboring cells (step S252).

  Here, there is a possibility that only the CQI at a certain timing becomes extremely small because the transmission path characteristics are instantaneously deteriorated due to fading and measurement errors, and the radio wave environment in the wireless terminal device 202 is deteriorated.

  Therefore, as described above, the reselection unit 11 sets measurement start conditions for neighboring cells based on CQIs for multiple times indicating reception quality acquired at different times. Thereby, it is possible to suppress erroneous determination due to instantaneous deterioration of the transmission path characteristics.

  Note that the wireless terminal device 202 may be configured to determine the deterioration of the radio wave environment by combining the evaluation methods described with reference to FIGS. For example, the value after the statistical processing of CQI described in FIG. 14 can be used for each determination formula shown in FIGS.

  FIG. 15 is a diagram illustrating a correspondence between the S value and the CQI and each layer in the communication protocol by the wireless terminal device according to the embodiment of the present invention.

  Referring to FIG. 15, radio terminal apparatus 202 includes, for example, communication having an RRC layer, a PDCP (Packet Data Convergence Protocol) layer, an RLC (Radio Link Control) layer, a MAC layer, a PHY layer, and an RF (Radio Frequency) layer. Operates according to protocol. Here, the RRC layer is the highest layer and the RF layer is the lowest layer.

  That is, the evaluation value calculation unit 13 calculates evaluation values such as Srxlev and Squal based on the measurement result in the idle state of the radio signal from the radio base station apparatus 101 according to the RRC layer among the above layers.

  The reception quality information creating unit 14 receives the reception quality based on the measurement result in the idle state of the radio signal from the radio base station apparatus 101 according to at least one of the MAC layer and the PHY layer lower than the RRC layer among the above layers. Information such as CQI is calculated.

  Then, the reselection unit 11 uses the reception quality information acquired by the reception quality information creation unit 14 in determining whether to perform the cell reselection operation.

  Srxlev and Squal correspond to the RRC layer, that is, the evaluation value calculation unit 13 causes the radio base station apparatus 101 to indicate the RF layer, the PHY layer, the MAC layer, the RLC layer, the PDCP layer, and the RRC as indicated by the arrow R1. Information necessary for calculating Srxlev and Squal is acquired through the layer.

  The CQI corresponds to at least one of the MAC layer and the PHY layer. For this reason, for example, when the CQI corresponds to the MAC layer, the reception quality information creation unit 14 acquires information necessary for calculating the CQI via the RF layer, the PHY layer, and the MAC layer as indicated by an arrow R2. .

  For this reason, CQI does not require time for calculation compared to Srxlev and Squal, and wireless terminal apparatus 202 can be updated in a short cycle.

  As described above, by effectively utilizing lower layer information, it is possible to quickly and appropriately determine cell reselection.

  By the way, with the movement of the wireless terminal device in the idle state, the radio wave environment of the wireless terminal device may deteriorate rapidly, and cell reselection may not be in time in the wireless terminal device, resulting in an out-of-service state. In this case, since the wireless terminal device is in the cell again, it is necessary to re-execute processing such as searching for the frequency of the wireless signal from the wireless base station device, and the increase in power consumption of the wireless terminal device and Various problems such as deterioration of the user's feeling occur.

  On the other hand, in the radio terminal apparatus according to the embodiment of the present invention, reselecting section 11 serves as a serving base station that is radio base station apparatus 101 selected as a communication partner in the idle state of radio terminal apparatus 202. A cell reselection operation is executed to determine whether to continuously select a communication base as a communication partner or to newly select a neighboring base station that is a radio base station apparatus 101 other than the serving base station as a communication partner. The evaluation value calculation unit 13 calculates at least one evaluation value of the reception power and reception quality of the radio signal from the radio base station apparatus 101. The reception quality information creating unit 14 creates reception quality information indicating a reception quality of a radio signal from the serving base station, updated at a cycle shorter than the evaluation value. Then, the reselection unit 11 uses the reception quality information in determining whether to perform the cell reselection operation.

  As described above, the configuration for performing the cell reselection operation using the CQI having an update period shorter than the evaluation value, for example, the S value, can follow a sudden change in the radio wave environment. Cell reselection can be performed quickly.

  Therefore, in the wireless terminal device according to the embodiment of the present invention, it is possible to suppress the occurrence of the out-of-service state in the idle wireless terminal device.

  Moreover, in the radio terminal apparatus according to the embodiment of the present invention, reselection unit 11 uses the evaluation value and the reception quality information in determining whether to perform the cell reselection operation.

  As described above, by using the evaluation value in addition to CQI for determination of execution of the cell reselection operation, the radio wave environment of the wireless terminal device 202 can be grasped in more detail and the execution determination of the cell reselection operation can be performed more appropriately. Can do.

  Further, in the radio terminal apparatus according to the embodiment of the present invention, measurement unit 12 measures a radio signal from the serving base station in the idle state, and from the neighboring base station if the evaluation value of the serving base station satisfies the condition The measurement of the radio signal is started. The reselection unit 11 sets the above condition based on the reception quality information. Then, the reselection unit 11 starts the cell reselection operation when the measurement of the neighboring base station is started, and continues to select the serving base station as a communication partner based on at least the evaluation value of the neighboring base station. Then, it is determined whether or not a neighboring base station is newly selected as a communication partner.

  With such a configuration, it is possible to appropriately set measurement start conditions for neighboring cells in accordance with the reception quality of the wireless terminal device 202 and to appropriately determine whether to perform a cell reselection operation.

  Further, in the radio terminal apparatus according to the embodiment of the present invention, the reselection unit 11 causes the measurement unit 12 to start measurement of radio signals from neighboring base stations earlier when the reception quality indicated by the reception quality information deteriorates. Set the above conditions.

  With such a configuration, measurement start of neighboring cells can be accelerated according to reception quality deterioration of the wireless terminal device 202, so that information for determining whether to perform cell reselection follows a sudden change in radio wave environment. And can get quickly.

  Further, in the radio terminal apparatus according to the embodiment of the present invention, measurement unit 12 can determine the neighboring base station if the evaluation value of the serving base station satisfies the condition when the reception quality indicated by the reception quality information is poor in the idle state. Measurement of radio signal from is started.

  With such a configuration, the neighboring cell measurement start condition using the evaluation value of the serving base station can be set at an appropriate timing according to the degradation of the reception quality of the wireless terminal device 202.

  Moreover, in the radio | wireless terminal apparatus which concerns on embodiment of this invention, the measurement part 12 will start the measurement of the radio signal from a periphery base station, if conditions are satisfied in an idle state. The reselection unit 11 sets the above condition based on the reception quality information. Then, the reselection unit 11 starts the cell reselection operation when the measurement of the neighboring base station is started, and continues to select the serving base station as a communication partner based on at least the evaluation value of the neighboring base station. Then, it is determined whether or not a neighboring base station is newly selected as a communication partner.

  With such a configuration, measurement of a neighboring cell is started by detecting a deterioration in reception quality of the wireless terminal device 202 by CQI without going through the measurement start judgment of the neighboring cell based on the evaluation value of the serving base station. Cell reselection to a cell can be performed quickly.

  Further, in the radio terminal apparatus according to the embodiment of the present invention, reselection section 11 starts measurement of radio signals from neighboring base stations based on the reception quality information and the time elapsed since the reception quality information was updated. Set conditions.

  As described above, the configuration in which the update elapsed time of the information indicating the radio wave environment of the wireless terminal device 202 is used as the measurement start condition of the neighboring cell suppresses misjudgment due to old information, and more appropriately determines whether to perform measurement of the neighboring cell. Can be done.

  Moreover, in the radio | wireless terminal apparatus which concerns on embodiment of this invention, the reselection part 11 sets the measurement start conditions of the radio signal from a periphery base station based on the reception quality information for multiple times.

  With such a configuration, it is possible to suppress misjudgment caused by an instantaneous change in the radio wave environment and more appropriately perform execution judgment of measurement of neighboring cells.

  Also, in the radio terminal apparatus according to the embodiment of the present invention, reception quality information creation section 14 transmits from radio base station apparatus 101 in the process for self radio terminal apparatus 202 to reside in radio base station apparatus 101. In accordance with an instruction included in the information for establishing a communication connection with the radio base station apparatus 101, reception quality information is created in the idle state.

  With such a configuration, information transmitted from the radio base station apparatus 101 can be diverted in the process for the radio terminal apparatus 202 to be in the cell, and the idle radio terminal apparatus 202 can perform CQI measurement. it can.

  Also, in the radio terminal apparatus according to the embodiment of the present invention, reception quality information creation section 14 transmits from radio base station apparatus 101 in the process for self radio terminal apparatus 202 to reside in radio base station apparatus 101. The reception quality information is created in the idle state according to the instruction included in the information for releasing the communication connection with the radio base station apparatus 101.

  With such a configuration, information transmitted from the radio base station apparatus 101 can be diverted in the process for the radio terminal apparatus 202 to be in the cell, and the idle radio terminal apparatus 202 can perform CQI measurement. it can.

  Moreover, in the radio | wireless terminal apparatus which concerns on embodiment of this invention, the evaluation value calculating part 13 is based on the measurement result in the idle state of the radio signal from the radio base station apparatus 101 according to the 1st layer of multiple layers. As the first measurement information based, for example, an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station apparatus 101 is acquired. The reception quality information creation unit 14 performs second measurement information based on a measurement result in an idle state of a radio signal from the radio base station apparatus 101 in accordance with a second layer lower than the first layer among the plurality of layers. For example, reception quality information is acquired. Then, the reselection unit 11 uses the reception quality information acquired by the reception quality information creation unit 14 in determining whether to perform the cell reselection operation.

  In this way, in the communication protocol, the configuration for performing the cell reselection operation execution determination using lower layer information can reduce the acquisition time of information for the cell reselection operation execution determination, A quick and appropriate execution decision of cell reselection can be made. That is, since it is possible to follow a sudden change in the radio wave environment, cell reselection to a neighboring cell can be performed quickly, and the occurrence of an out-of-service state of the wireless terminal device can be suppressed. Therefore, it is possible to suppress the occurrence of the out-of-service state in the wireless terminal device in the idle state.

  From the viewpoint of this layer, the wireless terminal device is not limited to a configuration that creates reception quality information, but may be any configuration that creates information indicating measurement results of radio signals from one or more radio base station devices. .

  In the radio terminal apparatus according to the embodiment of the present invention, the evaluation value corresponds to the RRC layer specified by 3GPP, and the reception quality information corresponds to at least one of the MAC layer and the PHY layer specified by 3GPP.

  With such a configuration, it is possible to suppress the occurrence of an out-of-service state in the idle state by appropriately performing execution determination of the cell reselection operation in the wireless terminal device that operates in accordance with the communication protocol defined in 3GPP. .

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

11 reselection unit 12 measurement unit 13 evaluation value calculation unit (first measurement information acquisition unit)
14 Reception quality information creation unit (second measurement information acquisition unit)
DESCRIPTION OF SYMBOLS 81 Antenna 82 Circulator 83 Wireless receiving part 84 Wireless transmission part 85 Signal processing part 86 Reception signal processing part 87 Transmission signal processing part 88 Control part 89 Input / output part 101A, 101B, 101C Wireless base station apparatus 161 S-GW
162 MME
163 P-GW
202 wireless terminal device 301 core network 302 IP network

Claims (16)

A wireless terminal device capable of communicating with the wireless base station device by transmitting and receiving wireless signals to and from the wireless base station device,
In the idle state, a serving base station that is a radio base station device selected as a communication partner is continuously selected as a communication partner, or a neighboring base station that is another radio base station device other than the serving base station is communicated A reselection unit for executing a reselection operation for determining whether to newly select an opponent,
An evaluation value calculation unit for calculating an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station device;
A reception quality information creation unit for creating reception quality information that is updated in a cycle shorter than the evaluation value and indicates reception quality of a radio signal from the serving base station,
The reselection unit is a wireless terminal device that uses the reception quality information in determining whether to perform the reselection operation.   The radio terminal apparatus according to claim 1, wherein the reselection unit uses the evaluation value and the reception quality information in determining whether to perform the reselection operation. The wireless terminal device further includes:
In an idle state, a radio signal from the serving base station is measured, and when the evaluation value of the serving base station satisfies a condition, a measurement unit for starting measurement of the radio signal from the neighboring base station,
The reselection unit sets the condition based on the reception quality information, and starts the reselection operation when measurement of a radio signal from the peripheral base station by the measurement unit is started, and at least the peripheral base station 3. The method according to claim 1, wherein it is determined whether to continuously select the serving base station as a communication partner or to newly select the neighboring base station as a communication partner based on the evaluation value of a station. Wireless terminal device.   4. The radio according to claim 3, wherein the reselection unit sets the condition so that measurement start of a radio signal from the neighboring base station by the measurement unit is accelerated when reception quality indicated by the reception quality information is deteriorated. Terminal device.   The measurement unit starts measurement of radio signals from the neighboring base stations when the evaluation value of the serving base station satisfies a condition when the reception quality indicated by the reception quality information is poor in an idle state. The wireless terminal device according to claim 3 or claim 4. The wireless terminal device further includes:
In an idle state, when a condition is satisfied, a measurement unit for starting measurement of a radio signal from the neighboring base station is provided,
The reselection unit sets the condition based on the reception quality information, and starts the reselection operation when measurement of a radio signal from the peripheral base station by the measurement unit is started, and at least the peripheral base station 3. The method according to claim 1, wherein it is determined whether to continuously select the serving base station as a communication partner or to newly select the neighboring base station as a communication partner based on the evaluation value of a station. Wireless terminal device.   The radio terminal apparatus according to claim 6, wherein the reselection unit sets the condition based on the reception quality information and a time elapsed after the reception quality information is updated.   The radio terminal apparatus according to claim 6 or 7, wherein the reselection unit sets the condition based on the reception quality information for a plurality of times.   The reception quality information creation unit is configured to establish a communication connection with the radio base station apparatus that is transmitted from the radio base station apparatus in a process for allowing the own radio terminal apparatus to be in the radio base station apparatus. The wireless terminal device according to claim 1, wherein the reception quality information is created in an idle state in accordance with an instruction included in the information.   The reception quality information creating unit is configured to release a communication connection with the radio base station apparatus that is transmitted from the radio base station apparatus in a process for allowing the own radio terminal apparatus to be in the radio base station apparatus. The wireless terminal device according to any one of claims 1 to 9, wherein the reception quality information is created in an idle state in accordance with an instruction included in the information. A wireless terminal device capable of communicating with the wireless base station device by transmitting and receiving wireless signals to and from the wireless base station device and operating according to a communication protocol having a plurality of layers,
A first measurement information acquisition unit for acquiring first measurement information based on a measurement result in an idle state of a radio signal from a radio base station device according to a first layer of the plurality of layers;
2nd measurement for acquiring the 2nd measurement information based on the measurement result in the idle state of the radio signal from a radio base station device according to the 2nd layer lower than the 1st layer among the plurality of layers An information acquisition unit;
In the idle state, a serving base station that is a radio base station device selected as a communication partner is continuously selected as a communication partner, or a neighboring base station that is another radio base station device other than the serving base station is communicated A reselection unit for executing a reselection operation for determining whether to newly select an opponent,
The reselection unit uses the second measurement information acquired by the second measurement information acquisition unit in determining whether to perform the reselection operation. The first layer is an RRC (Radio Resource Control) layer defined by 3GPP (Third Generation Partnership Project),
The wireless terminal device according to claim 11, wherein the second layer is at least one of a MAC (Media Access Control) layer and a PHY (Physical) layer defined by 3GPP. A plurality of radio base station devices;
A communication system comprising a wireless terminal device capable of communicating with the wireless base station device by transmitting and receiving wireless signals to and from the wireless base station device,
The wireless terminal device
In the idle state, a serving base station that is a radio base station device selected as a communication partner is continuously selected as a communication partner, or a neighboring base station that is another radio base station device other than the serving base station is communicated A reselection unit for executing a reselection operation for determining whether to newly select an opponent,
An evaluation value calculation unit for calculating an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station device;
A reception quality information creation unit for creating reception quality information that is updated in a cycle shorter than the evaluation value and indicates reception quality of a radio signal from the serving base station,
The reselection unit uses the reception quality information in determining whether to perform the reselection operation. A plurality of radio base station devices;
A communication system comprising a radio terminal device capable of communicating with the radio base station device by transmitting and receiving radio signals to and from the radio base station device and operating according to a communication protocol having a plurality of layers,
A first measurement information acquisition unit for acquiring first measurement information based on a measurement result in an idle state of a radio signal from a radio base station device according to a first layer of the plurality of layers;
2nd measurement for acquiring the 2nd measurement information based on the measurement result in the idle state of the radio signal from a radio base station device according to the 2nd layer lower than the 1st layer among the plurality of layers An information acquisition unit;
In the idle state, a serving base station that is a radio base station device selected as a communication partner is continuously selected as a communication partner, or a neighboring base station that is another radio base station device other than the serving base station is communicated A reselection unit for executing a reselection operation for determining whether to newly select an opponent,
The reselection unit uses the second measurement information acquired by the second measurement information acquisition unit in determining whether to execute the reselection operation. A communication control method in a wireless terminal device capable of communicating with the wireless base station device by transmitting and receiving wireless signals to and from the wireless base station device,
Calculating an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station device in an idle state;
In idle state, updated in a cycle shorter than the evaluation value, creating reception quality information indicating reception quality of a radio signal from a serving base station that is a radio base station device selected as a communication partner;
Reselection to determine whether to continuously select the serving base station as a communication partner in the idle state or to newly select a neighboring base station other than the serving base station as a communication partner And a step of using the reception quality information in determining whether or not to execute the reselection operation. A communication control program used in a wireless terminal device capable of communicating with the wireless base station device by transmitting and receiving wireless signals to and from the wireless base station device,
Calculating an evaluation value of at least one of reception power and reception quality of a radio signal from the radio base station device in an idle state;
In idle state, updated in a cycle shorter than the evaluation value, creating reception quality information indicating reception quality of a radio signal from a serving base station that is a radio base station device selected as a communication partner;
Reselection to determine whether to continuously select the serving base station as a communication partner in the idle state or to newly select a neighboring base station other than the serving base station as a communication partner A communication control program for executing an operation and using the reception quality information in determining whether to execute the reselection operation.

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