JP2013201502A - Random access control device, radio base station device, management device, and random access control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a better communication system through proper configuration of a random access signal that is transmitted and received for adjusting the timing of transmission from a radio base station device to a radio terminal device before the communication connection is established between the radio terminal device and the radio base station device.SOLUTION: A random access control device 101 comprises: a power limit section 11 for determining an upper limit of power for radio signals transmitted from a radio terminal device 202 to a target base station, which is a target radio base station device, on the basis of prescribed information; and a random access signal selection section 12 for selecting one or more types of random access signals available for the radio terminal device 202 from multiple types of random access signals on the basis of the upper limit determined by the power limit section 11.

Description

  The present invention relates to a random access control device, a radio base station device, a management device, and a random access control program, and in particular, a random access control device, a radio base station device, a management device, and a random access control for setting a random access signal. Regarding the program.

  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, before the wireless terminal device establishes a communication connection with the wireless base station device, RACH (Random Access Channel) transmitted and received between the wireless terminal device and the wireless base station device is 3GPP TS 36.211 V10.4.0 2011.12 (Non-Patent Document 1). The radio base station apparatus adjusts the transmission timing from the radio terminal apparatus to itself using RACH, thereby enabling good communication between itself and the radio terminal apparatus.

3GPP TS 36.211 V10.4.0 2011.12

  A femto base station or a pico base station is often arranged unplanned compared to a macro base station, and activation and deactivation may be dynamically controlled according to increase or decrease of communication load in a communication system. . For this reason, optimal parameter settings regarding RACH, such as transmission timing and transmission power, are not constant and may change.

  If the RACH parameter setting is not appropriate, the wireless terminal device cannot establish a communication connection with the wireless base station device, a delay occurs in establishing the communication connection, and a delay occurs in the handover operation of the wireless terminal device Various problems arise.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to transmit and receive data from a radio base station apparatus that is transmitted and received prior to establishing a communication connection between the radio terminal apparatus and the radio base station apparatus. Random access control apparatus, radio base station apparatus, management apparatus, and random access control capable of constructing good communication system by appropriately setting random access signal for adjusting transmission timing to terminal apparatus Is to provide a program.

  (1) In order to solve the above problem, a random access control device according to an aspect of the present invention is transmitted from a wireless terminal device to a target base station that is a target wireless base station device based on predetermined information. A power limiting unit for determining an upper limit of transmission power of the wireless signal, and the wireless terminal device detected by the target base station to adjust a transmission timing from the wireless terminal device to the target base station. Based on the upper limit determined by the power limiter for a random access signal transmitted from the wireless terminal device prior to establishing a communication connection with a wireless base station device, a plurality of types of random access signals A random access signal selection unit for selecting one or a plurality of types of random access signals that can be used by the wireless terminal device.

  With such a configuration, it is possible to select an appropriate random access signal corresponding to the upper limit of the transmission power of the radio signal transmitted from the radio terminal apparatus to its own radio base station apparatus. Therefore, a good communication system can be constructed by appropriately setting a random access signal. In addition, since the parameters related to the RACH of femto base stations and pico base stations that are often installed unplanned can be automatically set, CAPEX (Capital Expenditure), that is, the cost required for arrangement of radio base station apparatuses, and OPEX (Operational Expenditure), that is, the cost for operating the radio base station apparatus can be reduced.

  (2) Preferably, the random access control device further includes a cell radius information acquisition unit for acquiring cell radius information capable of evaluating a cell radius of the target base station, and the power limiting unit includes the cell The upper limit is determined based on the radius information.

  As described above, the configuration for setting the random access signal of the own radio base station apparatus based on the cell radius of the own radio base station apparatus makes it possible to perform the optimum setting according to the characteristics of the radio base station apparatus. .

  (3) More preferably, the power limiting unit sets the upper limit larger as the cell radius of the target base station is larger.

  With such a configuration, it is possible to appropriately set the upper limit of the transmission power of the radio terminal apparatus according to the size of the cell radius of the own radio base station apparatus and select an appropriate random access signal.

  (4) Preferably, the random access control device further includes a movement information acquisition unit for acquiring failure information based on the number of failures of the movement operation of the wireless terminal device from another wireless base station device to the target base station. The power limiting unit determines the upper limit based on the failure information.

  As described above, the configuration for setting the random access signal of the wireless base station device based on the state of the movement operation of the wireless terminal device to the wireless base station device according to the communication environment of the wireless base station device Optimal settings can be made.

  (5) More preferably, the power limiting unit sets the upper limit larger as the number of failures or the failure rate of the moving operation is larger.

  With such a configuration, it is possible to appropriately set the upper limit of the transmission power of the wireless terminal device based on the failure history of the movement operation of the wireless terminal device to its own wireless base station device and select an appropriate random access signal. it can.

  (6) Preferably, the wireless terminal device repeatedly transmits the random access signal to the wireless base station device until the wireless base station device detects the random access signal, and the random access control device further includes the target A trial number acquisition unit for acquiring the number of transmissions of the random access signal from the wireless terminal device to the target base station until the base station detects the random access signal, and the power limiting unit includes the transmission The upper limit is determined based on the number of times.

  In this way, the configuration for performing the setting related to the random access signal of the own radio base station apparatus based on the detection characteristics of the random access signal from the radio terminal apparatus in the own radio base station apparatus, the communication environment of the radio base station apparatus It is possible to perform optimum settings according to the settings.

  (7) More preferably, the power limiting unit sets the upper limit as the number of transmissions increases.

  With such a configuration, it is possible to appropriately set the upper limit of the transmission power of the wireless terminal device according to the number of transmissions of the random access signal from the wireless terminal device, and to select an appropriate random access signal.

  (8) Preferably, the random access signal selection unit is configured to select the wireless terminal device from a plurality of types of the random access signals based on a CM (Cubic Metric) value determined by the upper limit determined by the power limiting unit. Selects one or more types of random access signals that can be used.

  With such a configuration, it is possible to select an appropriate random access signal corresponding to the magnitude of the CM value.

  Preferably, the random access signal is a random access preamble.

  With such a configuration, an appropriate random access preamble can be selected and an important random access preamble can be detected well in a random access sequence.

  (9) In order to solve the above problem, a radio base station apparatus according to an aspect of the present invention includes the random access control apparatus according to (1) above.

  With such a configuration, each radio base station apparatus can set a random access signal in the radio communication system, so that the determination of the upper limit of the transmission power of the radio terminal apparatus and the processing load of the setting related to the random access signal are distributed. be able to.

  (10) In order to solve the above problems, a management apparatus according to an aspect of the present invention manages one or a plurality of radio base station apparatuses, and includes the random access control apparatus according to (1).

  With such a configuration, the random access signal of each wireless base station device in the wireless communication system can be collectively set in the management device, so the determination of the upper limit of the transmission power of the wireless terminal device and the setting related to the random access signal Can be performed more efficiently.

  (11) In order to solve the above-described problem, a random access control device according to an aspect of the present invention is a random access control program used in a random access control device. A step of determining an upper limit of transmission power of a radio signal transmitted from a radio terminal apparatus to a target base station which is a radio base station apparatus, and for adjusting a transmission timing from the radio terminal apparatus to the target base station Based on the determined upper limit for the random access signal detected by the target base station and transmitted from the wireless terminal device prior to the wireless terminal device establishing a communication connection with the wireless base station device, One or more types of landers that can be used by the wireless terminal device from a plurality of types of random access signals Is a program for executing the steps of selecting an access signal.

  With such a configuration, it is possible to select an appropriate random access signal corresponding to the upper limit of the transmission power of the radio signal transmitted from the radio terminal apparatus to its own radio base station apparatus. Therefore, a good communication system can be constructed by appropriately setting a random access signal. In addition, since the parameters related to the RACH of femto base stations and pico base stations that are often installed unplanned can be automatically set, CAPEX (Capital Expenditure), that is, the cost required for arrangement of radio base station apparatuses, and OPEX (Operational Expenditure), that is, the cost for operating the radio base station apparatus can be reduced.

  According to the present invention, a random access signal for adjusting transmission timing from a radio base station apparatus to a radio terminal apparatus, which is transmitted / received prior to establishing a communication connection between the radio terminal apparatus and the radio base station apparatus, is transmitted. A suitable communication system can be constructed by appropriately performing the setting.

It is a figure which shows the structure of the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the structure of the radio base station apparatus which concerns on embodiment of this invention. It is a figure which shows the random access sequence in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the structure of the control part in the radio base station apparatus which concerns on embodiment of this invention. It is the flowchart which defined an example of the operation | movement procedure at the time of the radio base station apparatus which concerns on embodiment of this invention setting a RACH parameter. It is a figure which shows an example of the acquisition method of the cell radius of the radio base station apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the acquisition method of the cell radius of the radio base station apparatus which concerns on embodiment of this invention. It is the flowchart which defined an example of the operation | movement procedure at the time of the radio base station apparatus which concerns on embodiment of this invention setting a RACH parameter. It is the flowchart which defined an example of the operation | movement procedure at the time of the radio base station apparatus which concerns on embodiment of this invention setting a RACH parameter.

  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. Based on this measurement result, movement of the wireless terminal device to the neighboring cells is started. 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.

  Specifically, in addition to meaning handover, for example, an idle radio terminal device described in 3GPP TS 36.304 V10.3.0 2011.10. This means cell reselection for selecting a radio base station apparatus to be a communication partner based on the measurement result of the radio signal from.

  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 that is a communication partner 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 where communication is not performed” is a state where 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 destination and can communicate with the wireless base station device. This means that communication is in progress.

  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.

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

  Referring to FIG. 1, a wireless communication system 301 is a mobile communication system that complies with, for example, LTE (Long Term Evolution) standardized by 3GPP (Third Generation Partnership Project), and includes femto base stations 101A, 101B, and 101C. A pico base station 101D, a macro base station 201, and a gateway device 203 are provided.

  Hereinafter, each of the femto base stations 101A, 101B, and 101C, the pico base station 101D, and the macro base station 201 may be referred to as a radio base station apparatus 101. In FIG. 1, one macro base station, one pico base station, and three femto base stations are representatively shown, but the combination and number thereof are not limited thereto.

  The femto base stations 101A, 101B, and 101C form femtocells FCA, FCB, and FCC having a radius of several tens of meters, for example. Further, the pico base station 101D forms a picocell PC having a radius of 100 meters to 200 meters. The macro base station 201 forms a macro cell MC having a radius of several kilometers, for example.

  The femto base stations 101A, 101B, and 101C are installed in places where it is difficult for the wireless terminal device 202 to receive radio signals from the macro base station 201 and the pico base station 101D, such as an underground mall, and are respectively located in the femtocells FCA, FCB, and FCC. It is possible to communicate with the wireless terminal device 202 by transmitting and receiving wireless signals to and from the existing wireless terminal device 202.

  The pico base station 101D can communicate with the radio terminal device 202 by transmitting and receiving radio signals to and from the radio terminal device 202 existing in the pico cell PC. The macro base station 201 can communicate with the wireless terminal device 202 by transmitting and receiving wireless signals to and from the wireless terminal device 202 existing in the macro cell MC.

  The gateway device 203 performs relay processing of various communication data transmitted between the femto base stations 101A, 101B, and 101C and the host device 205 in the core network 204.

  The host device 205 is, for example, an MME (Mobility Management Entity), and manages information on the entire wireless communication system 301. For example, the upper device 205 acquires and stores information on each radio base station device in the radio communication system 301.

  Here, the direction from the wireless terminal device 202 to the core network 204 is referred to as an uplink direction, and the direction from the core network 204 to the wireless terminal device 202 is referred to as a downlink direction.

  FIG. 2 is a diagram showing the configuration of the radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 2, radio base station apparatus 101 includes antenna 91, circulator 92, radio reception unit 93, radio transmission unit 94, signal processing unit 95, and control unit 98. The signal processing unit 95 includes a reception signal processing unit 96 and a transmission signal processing unit 97. The signal processing unit 95 and the control unit 98 are realized by a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

  The circulator 92 outputs the radio signal from the radio terminal device 202 received by the antenna 91 to the radio reception unit 93 and outputs the radio signal received from the radio transmission unit 94 to the antenna 91.

  Radio receiving section 93 converts the radio signal received from circulator 92 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 96.

  The received signal processing unit 96 performs signal processing such as despreading in the CDMA (Code Division Multiple Access) method on the digital signal received from the wireless receiving unit 93, and part or all of the digital signal after this signal processing is performed. The data is converted into a predetermined frame format and transmitted to the core network side.

  The transmission signal processing unit 97 performs IFFT (Inverse Fast Fourier Transform) in an OFDM (Orthogonal Frequency Division Multiplex) method on communication data obtained by converting communication data received from the core network side into a predetermined frame format or communication data generated by itself. The digital signal after the signal processing is output to the wireless transmission unit 94.

  The radio transmission unit 94 converts the digital signal received from the transmission signal processing unit 97 into an analog signal, converts the frequency of the converted analog signal into a radio signal, and outputs the radio signal to the circulator 92.

  The control unit 98 exchanges various information with each unit and the core network side in the radio base station apparatus 101.

  FIG. 3 is a diagram showing a random access sequence in the radio communication system according to the embodiment of the present invention.

  Referring to FIG. 3, first, radio base station apparatus 101, for example, the transmission timing and transmission frequency of a random access preamble (hereinafter also referred to as RACH preamble) described in Non-Patent Document 1, the number of usable RACH preambles. The transmission power of the RACH preamble is included in the broadcast information and transmitted to each wireless terminal device 202 (step S101).

  Next, based on the broadcast information received from the radio base station apparatus 101, the radio terminal apparatus 202 selects one of a plurality of types of RACH preambles designated by the radio base station apparatus 101 (Step S102). ), And transmits to the radio base station apparatus 101 (step S103).

  Next, the radio base station apparatus 101 detects the RACH preamble transmitted from the radio terminal apparatus 202, estimates the transmission timing shift of the radio terminal apparatus 202, and calculates a correction value for the transmission timing (step S104). ).

  Next, the radio base station apparatus 101 wirelessly transmits the calculated correction value, the detected RACH preamble number, a temporary C-RNTI (Cell Radio Network Temporary Identifier), and RACH control information indicating the timing at which the RACH message should be transmitted. It transmits to the terminal device 202 (step S105).

  Next, the wireless terminal device 202 corrects its own transmission timing based on the RACH control information received from the wireless base station device 101 (step S106).

  Next, the radio terminal apparatus 202 adds the provisional C to the RACH message including a CR-ID (content reference identifier) for detecting a RACH preamble collision with another radio terminal apparatus 202 in the radio base station apparatus 101. -Transmit to the radio base station apparatus 101 with RNTI. In transmitting this RACH message, for example, HARQ (Hybrid Automatic Repeat Request) is used (step S107).

  Next, the radio base station apparatus 101 receives the RACH message from the radio terminal apparatus 202, and processing according to the upper layer such as registration processing of the radio terminal apparatus 202 is executed (step S108).

  Next, the radio base station apparatus 101 transmits RACH response information including the CR-ID received from the radio terminal apparatus 202, the official C-RNTI, and the like to the radio terminal apparatus 202 (step S109).

  Through the processing as described above, the random access sequence between the wireless terminal device 202 and the wireless base station device 101 is completed.

  For example, in LTE, as described in 3GPP TSG RAN WG1 # 50bis R1-0774514 “Way Forward Proposal on PRACH Sequence Ordering”, 838 RACH preambles are “high” in terms of CM (Cubic Metric) value. And “low”. That is, the CM value varies depending on the bit pattern of the RACH preamble.

  Of the 838 RACH preambles, the “low” group includes the RACH preambles from the zeroth to the 400th, and the “high” group includes the RACH preambles from the 400th to the 837th.

  The radio base station apparatus 101 selects 64 RACH preambles from the above group and causes the radio terminal apparatus 202 to use them.

  More specifically, the radio base station apparatus 101 determines 64 RACH preambles that can be used by the radio terminal apparatus 202 and informs each radio terminal apparatus 202 with broadcast information. Specifically, for example, the radio base station apparatus 101 notifies each radio terminal apparatus 202 only of the heads of 64 consecutive indexes called “Logical root sequence number”.

  Since the radio terminal apparatus 202 can increase the transmission power while suppressing distortion in the amplifier for transmitting a radio signal, the RACH preamble having a smaller CM value can reach a farther radio base station apparatus 101. It is.

[Task]
Here, for example, when the tilt angle of the transmission antenna of the radio base station apparatus 101 is changed and the cell radius is increased, when a RACH preamble having a large CM value is designated to the radio terminal apparatus 202, the radio terminal apparatus 202 The transmission power needs to be increased. Then, the distortion of the transmission radio signal increases, the radio terminal apparatus 202 cannot establish a communication connection with the radio base station apparatus 101, a delay occurs in the establishment of the communication connection, and a delay occurs in the handover operation of the radio terminal apparatus 202. Various problems occur, such as the occurrence.

  Therefore, in the wireless communication system according to the embodiment of the present invention, the above-described problem is solved by the following configuration and operation.

[Configuration and operation]
FIG. 4 is a diagram showing a configuration of a control unit in the radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 4, control unit 98 includes a power limiting unit 11, a random access signal selection unit 12, a cell radius information acquisition unit 13, a movement information acquisition unit 14, and a trial number acquisition unit 15.

  The power limiting unit 11 determines the upper limit of the transmission power of the radio signal transmitted from the radio terminal apparatus 202 to the radio base station apparatus 101 based on the predetermined information.

  The random access signal selection unit 12 selects one or more types of random access signals that can be used by the wireless terminal device 202 from among a plurality of types of random access signals based on the upper limit determined by the power limiting unit 11. To do. For example, the random access signal selection unit 12 selects a random access signal based on a CM (Cubic Metric) value determined by the upper limit determined by the power limiting unit 11.

  Here, the random access signal is, for example, a RACH preamble, and is detected by the radio base station apparatus 101 to adjust the transmission timing from the radio terminal apparatus 202 to the radio base station apparatus 101. The radio terminal apparatus 202 is a radio base station. This signal is transmitted from the wireless terminal device 202 prior to establishing a communication connection with the device 101.

[Detailed operation]
Next, the operation when the radio base station apparatus according to the embodiment of the present invention sets the RACH parameter will be described with reference to the drawings.

  The radio base station apparatus according to the embodiment of the present invention reads and executes 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.

  FIG. 5 is a flowchart defining an example of an operation procedure when the radio base station apparatus according to the embodiment of the present invention sets the RACH parameters.

  In the control unit 98 shown in FIG. 4, the cell radius information acquisition unit 13 acquires cell radius information that can evaluate the cell radius of its own radio base station apparatus 101. More specifically, the cell radius information acquisition unit 13 can evaluate the cell radius of the own radio base station apparatus 101 from the system information registered in the own radio base station apparatus 101 by the communication carrier, for example. Get information, for example, your own maximum transmit power. The cell radius information may be the cell radius value itself.

  Based on the cell radius information acquired by the cell radius information acquisition unit 13, the power limiting unit 11 determines the upper limit of the transmission power of the radio signal transmitted from the radio terminal device 202 to the own radio base station device 101. To do. For example, the power limiting unit 11 sets the upper limit larger as the cell radius of its own radio base station apparatus 101 is larger.

  Specifically, referring to FIG. 5, first, the cell radius of radio base station apparatus 101 is set. For example, the communication carrier sets the cell radius of the newly installed radio base station apparatus 101 (step S1).

  Next, in the control unit 98 of the radio base station apparatus 101, the power limiting unit 11 determines that the RACH preamble is not present when the cell radius of its own radio base station apparatus 101 is less than a predetermined threshold (YES in step S2). The CM value group is set to “high” (step S3). On the other hand, when the cell radius of its own radio base station apparatus 101 is equal to or larger than a predetermined threshold (NO in step S2), the power limiting unit 11 sets the CM value group of the RACH preamble to “low” ( Step S4).

  Next, the random access signal selection unit 12 selects a plurality of types of RACH preambles corresponding to the group set by the power restriction unit 11, and broadcast information indicating the selected content is transmitted to each wireless terminal via the transmission signal processing unit 97. Send to device 202. As a result, transmission / reception of the RACH preamble according to the setting content is performed between the own radio base station apparatus 101 and the radio terminal apparatus 202 (step S5).

  Then, when the cell radius of its own radio base station apparatus 101 is newly changed (YES in step S6), the power limiting unit 11 performs group setting of the CM value of the RACH preamble again (step S2).

  Here, as a method for the radio base station apparatus 101 to acquire its own cell radius, for example, external information of the radio base station apparatus 101, internal information of the radio base station apparatus 101 such as the system information described above, or neighboring cells A method of acquiring the cell radius of its own radio base station apparatus 101 from the measurement result is considered.

  FIG. 6 is a diagram illustrating an example of a cell radius acquisition method of the radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 6, information related to a mobile communication service area is usually managed by a communication carrier. Therefore, the radio base station apparatus 101 acquires cell radius information from the communication carrier.

  Specifically, in the control unit 98 of the radio base station apparatus 101, the cell radius information acquisition unit 13 regularly accesses the server 206 of the communication carrier, and cell radius information of its own radio base station apparatus 101. To get.

  Alternatively, when the cell radius of the radio base station apparatus 101 is changed, the server 206 notifies the radio base station apparatus 101 of the changed cell radius.

  Alternatively, the cell radius information acquisition unit 13 acquires and stores information on the tilt angle of the transmission antenna of the radio base station apparatus 101 and the transmission power of the radio signal. Then, the cell radius information acquisition unit 13 periodically acquires information on the tilt angle and transmission power from the server 206, for example, and compares the information with the stored information. It is determined that the cell radius of base station apparatus 101 has been changed.

  FIG. 7 is a diagram illustrating an example of a cell radius acquisition method of the radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 7, in signal processing unit 95 of radio base station apparatus 101, received signal processing unit 96 measures the received power of the radio signal transmitted by the neighboring base station. The cell radius information acquisition unit 13 is a difference between the transmission power of the radio signal transmitted by the neighboring base station and the received power of the radio signal transmitted by the neighboring base station in the cell formed by the own radio base station apparatus 101. Based on the path loss, the inter-base station distance between its own radio base station apparatus 101 and neighboring base stations is estimated and stored.

  The cell radius information acquisition unit 13 periodically acquires the transmission power of the neighboring base stations and obtains the measurement results of the neighboring base stations by the reception signal processing unit 96 to obtain the path loss, and estimates the distance between the base stations. The cell radius information acquisition unit 13 compares the newly estimated inter-base station distance with the stored inter-base station distance, and determines that the cell radius has been changed if there is a change.

  Specifically, as shown in FIG. 7, when the cell radius is changed, when the femto base station 101F is newly installed in a state where the femto base stations 101A, 101B, and 101C are installed, For example, the transmission power of the femto base stations 101A, 101B, and 101C is changed by the communication carrier, and the path loss changes. As a result, the radii of the cells FCA, FCB, FCC of the femto base stations 101A, 101B, 101C are changed.

  FIG. 8 is a flowchart defining an example of an operation procedure when the radio base station apparatus according to the embodiment of the present invention sets the RACH parameters.

  In the control unit 98 illustrated in FIG. 4, the movement information acquisition unit 14 performs failure information based on the number of failed handover operations of the wireless terminal device 202 from another wireless base station device 101 to its own wireless base station device 101, that is, Acquire information indicating the number of failures or failure rate.

  The power limiting unit 11 determines the upper limit of the transmission power of the radio signal transmitted from the radio terminal device 202 to the radio base station device 101 based on the failure information acquired by the movement information acquisition unit 14. For example, the power limiting unit 11 sets the upper limit as the number of failures or failure rate of the handover operation increases.

  Specifically, referring to FIG. 8, first, in radio base station apparatus 101, a group of RACH preamble CM values is initially set (step S11).

  Next, in the control unit 98 of the radio base station apparatus 101, the random access signal selection unit 12 selects a plurality of types of RACH preambles corresponding to the set group, and transmits broadcast information indicating the selected content to the transmission signal processing unit. 97 to each wireless terminal device 202. As a result, transmission / reception of the RACH preamble according to the setting content is performed between the own radio base station apparatus 101 and the radio terminal apparatus 202 (step S12).

  Next, the movement information acquisition unit 14 counts the number of failed handover operations of the wireless terminal device 202 from the neighboring base station to its own wireless base station device 101 and the number of successes as necessary, for example, for a predetermined period. If the number of failures or the failure rate of the handover operation is less than a predetermined threshold (YES in step S13), the power limiting unit 11 sets the CM value group of the RACH preamble to “high” (step S13). S14). On the other hand, when the number of failures or failure rate is equal to or greater than the predetermined threshold (NO in step S13), the power limiting unit 11 sets the CM value group of the RACH preamble to “low” (step S15). .

  Next, the random access signal selection unit 12 selects a plurality of types of RACH preambles corresponding to the group set by the power restriction unit 11, and broadcast information indicating the selected content is transmitted to each wireless terminal via the transmission signal processing unit 97. Send to device 202. As a result, transmission / reception of the RACH preamble according to the setting content is performed between the own radio base station apparatus 101 and the radio terminal apparatus 202 (step S12).

  Note that the movement information acquisition unit 14 is not limited to the configuration for acquiring failure information based on the number of failures in the handover operation, but may be configured to acquire failure information based on the number of failures for cell reselection.

  FIG. 9 is a flowchart defining an example of an operation procedure when the radio base station apparatus according to the embodiment of the present invention sets the RACH parameters.

  For example, in LTE, power ramping is performed in transmission of the RACH preamble from the wireless terminal device 202. That is, the radio terminal apparatus 202 repeatedly transmits the RACH preamble to the radio base station apparatus 101 until the radio base station apparatus 101 detects the RACH preamble. Also, each time the radio terminal apparatus 202 retransmits the RACH preamble, the radio terminal apparatus 202 gradually increases the transmission power of the RACH preamble for each ramping step.

  In the control unit 98 illustrated in FIG. 4, the trial count acquisition unit 15 performs random access signals from the wireless terminal device 202 to the own wireless base station device 101 until the own wireless base station device 101 detects the random access signal. Get the number of transmissions of.

  The power limiting unit 11 determines the upper limit of the transmission power of the radio signal transmitted from the radio terminal device 202 to the radio base station device 101 based on the number of transmissions acquired by the trial number acquisition unit 15. For example, the power limiting unit 11 sets the upper limit as the number of transmissions increases.

  Specifically, referring to FIG. 9, first, in radio base station apparatus 101, a CM value group of RACH preamble is initialized (step S21).

  Next, in the control unit 98 of the radio base station apparatus 101, the random access signal selection unit 12 selects a plurality of types of RACH preambles corresponding to the set group, and transmits broadcast information indicating the selected content to the transmission signal processing unit. 97 to each wireless terminal device 202. As a result, transmission / reception of the RACH preamble according to the setting content is performed between the wireless base station apparatus 101 and the wireless terminal apparatus 202 (step S22).

  Next, the number-of-trials acquisition unit 15 transmits the RACH preamble by the wireless terminal device 202 until, for example, the number of RACH access attempts of the wireless terminal device 202 in a predetermined period, that is, until the wireless base station device 101 detects the RACH preamble Get the number of times. For example, the trial number acquisition unit 15 reports the number of transmissions from each wireless terminal device 202 and calculates an average value of the number of transmissions. Then, when the RACH access trial count is less than the predetermined threshold (YES in step S23), the power limiting unit 11 sets the CM value group of the RACH preamble to “high” (step S24). On the other hand, when the number of RACH access attempts is equal to or greater than the predetermined threshold (NO in step S23), the power limiting unit 11 sets the CM value group of the RACH preamble to “low” (step S25).

  Next, the random access signal selection unit 12 selects a plurality of types of RACH preambles corresponding to the group set by the power restriction unit 11, and broadcast information indicating the selected content is transmitted to each wireless terminal via the transmission signal processing unit 97. Send to device 202. As a result, transmission / reception of the RACH preamble according to the setting content is performed between the wireless base station apparatus 101 and the wireless terminal apparatus 202 (step S22).

  By the way, a femto base station or a pico base station is often arranged unplanned compared to a macro base station, and the start and stop are dynamically controlled according to increase or decrease of communication load in a communication system. There is also. For this reason, optimal parameter settings regarding RACH, such as transmission timing and transmission power, are not constant and may change. If the RACH parameter setting is not appropriate, the wireless terminal device cannot establish a communication connection with the wireless base station device, a delay occurs in establishing the communication connection, and a delay occurs in the handover operation of the wireless terminal device Various problems arise.

  In addition, if the operator sets the RACH parameters for each femto base station when installing the femto base station, considerable work and cost are required. Further, every time a femto base station is newly installed and the number of femto base stations is increased, not only newly installed femto base stations but also existing surrounding femto base stations must be reset.

  On the other hand, in the radio base station apparatus according to the embodiment of the present invention, power limiting unit 11 is a radio transmitted from radio terminal apparatus 202 to its own radio base station apparatus 101 based on predetermined information. Determine the upper limit of signal transmission power. The random access signal selection unit 12 selects one or more types of random access signals that can be used by the wireless terminal device 202 from among a plurality of types of random access signals based on the upper limit determined by the power limiting unit 11. To do.

  With such a configuration, it is possible to select an appropriate random access signal according to the upper limit of the transmission power of the radio signal transmitted from the radio terminal apparatus 202 to the own radio base station apparatus 101.

  Therefore, the radio base station apparatus according to the embodiment of the present invention can construct a good communication system by appropriately setting the random access signal.

  In addition, since the parameters related to the RACH of femto base stations and pico base stations that are often installed unplanned can be automatically set, CAPEX (Capital Expenditure), that is, the cost required for arrangement of radio base station apparatuses, and OPEX (Operational Expenditure), that is, the cost for operating the radio base station apparatus can be reduced.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the cell radius information acquisition unit 13 acquires cell radius information that can evaluate the cell radius of its own radio base station apparatus 101. Then, the power limiting unit 11 determines the upper limit based on the cell radius information acquired by the cell radius information acquiring unit 13.

  As described above, the configuration for performing the setting related to the random access signal of the own radio base station apparatus 101 based on the cell radius of the own radio base station apparatus 101 makes the optimum setting according to the characteristics of the radio base station apparatus 101. be able to.

  In the radio base station apparatus according to the embodiment of the present invention, power limiting section 11 sets the upper limit larger as the cell radius of its own radio base station apparatus 101 increases.

  With such a configuration, it is possible to appropriately set the upper limit of the transmission power of the radio terminal apparatus 202 according to the size of the cell radius of its own radio base station apparatus 101 and select an appropriate random access signal.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the movement information acquisition unit 14 counts the number of failed movement operations of the radio terminal apparatus 202 from another radio base station apparatus 101 to its own radio base station apparatus 101. Get failure information based on. Then, the power limiting unit 11 determines the upper limit based on the failure information acquired by the movement information acquisition unit 14.

  As described above, the wireless base station apparatus 101 communicates with the wireless base station apparatus 101 according to the configuration in which the setting related to the random access signal of the wireless base station apparatus 101 is performed based on the state of the movement operation of the wireless terminal apparatus 202 to the wireless base station apparatus 101. Optimal settings can be made according to the environment.

  Moreover, in the radio base station apparatus according to the embodiment of the present invention, power limiting section 11 sets the upper limit larger as the number of failure times or failure rates of the movement operation increases.

  With such a configuration, the upper limit of the transmission power of the wireless terminal device 202 is appropriately set based on the failure history of the movement operation of the wireless terminal device 202 to the own wireless base station device 101, and an appropriate random access signal is selected. can do.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the number-of-trials acquisition unit 15 receives the radio base station from the radio terminal apparatus 202 until the radio base station apparatus 101 detects a random access signal. The number of random access signal transmissions to the device 101 is acquired. The power limiting unit 11 determines the upper limit based on the number of transmissions acquired by the trial number acquisition unit 15.

  As described above, the radio base station apparatus 101 is configured to perform the setting related to the random access signal of the own radio base station apparatus 101 based on the detection characteristics of the random access signal from the radio terminal apparatus 202 in the own radio base station apparatus 101. It is possible to make optimum settings according to the communication environment.

  Further, in the radio base station apparatus according to the embodiment of the present invention, power limiting section 11 sets the upper limit larger as the number of transmissions increases.

  With such a configuration, it is possible to appropriately set the upper limit of the transmission power of the wireless terminal device 202 according to the number of transmissions of the random access signal from the wireless terminal device 202 and select an appropriate random access signal.

  Moreover, in the radio base station apparatus according to the embodiment of the present invention, the random access signal selection unit 12 uses a plurality of types of random metrics based on CM (Cubic Metric) values determined by the upper limit determined by the power limiting unit 11. One or a plurality of types of random access signals that can be used by the wireless terminal device 202 are selected from the access signals.

  With such a configuration, it is possible to select an appropriate random access signal corresponding to the magnitude of the CM value.

  Moreover, in the radio base station apparatus according to the embodiment of the present invention, the random access signal is a random access preamble.

  With such a configuration, an appropriate random access preamble can be selected and an important random access preamble can be detected well in a random access sequence.

  In the radio base station apparatus according to the embodiment of the present invention, the power limiting unit 11 is configured to set the CM value group of the RACH preamble to “high” or “low”. Not what you want. The configuration is not limited to a configuration in which two groups can be set, and may be a configuration in which three or more groups can be set.

  In the radio base station apparatus according to the embodiment of the present invention, the random access signal selection unit 12 is configured to select a plurality of types of RACH preambles corresponding to the group set by the power limiting unit 11. However, the present invention is not limited to this. The random access signal selection unit 12 may be configured to select one or more types of RACH preambles from among a plurality of types of RACH preambles corresponding to the group set by the power limiting unit 11.

  In the radio base station apparatus according to the embodiment of the present invention, the power limiting unit 11 is configured to set the RACH preamble group based on the CM value, but the present invention is not limited to this. The power limiting unit 11 is not limited to the CM value, and may be configured based on some index that can determine the upper limit of the transmission power of the wireless terminal device 202.

  In the radio communication system according to the embodiment of the present invention, radio base station apparatus 101 operates as a random access control apparatus. That is, the radio base station apparatus 101 is configured to determine the upper limit of the transmission power of the radio terminal apparatus 202 and to make settings related to its own random access signal. However, the present invention is not limited to this. The random access control device may be a management device for managing one or a plurality of radio base station devices 101. Specifically, the management apparatus for managing the radio base station apparatus 101, such as the gateway apparatus 203 and the higher-level apparatus 205, is the target of determining the upper limit of the transmission power of the radio terminal apparatus 202 and the target radio base station apparatus 101. The base station may be configured to make settings related to the random access signal.

  In this case, in the management device, the power limiting unit determines the upper limit of the transmission power of the radio signal transmitted from the wireless terminal device 202 to the target base station based on the predetermined information.

  Then, the random access signal selection unit selects one or a plurality of types of random access signals that can be used by the wireless terminal device 202 from a plurality of types of random access signals based on the upper limit determined by the power limiting unit. To do.

  With such a configuration, since the setting of the random access signal of each radio base station apparatus 101 in the radio communication system 301 can be performed collectively in the management apparatus, determination of the upper limit of the transmission power of the radio terminal apparatus 202 and random access Settings regarding signals can be performed more efficiently.

  On the other hand, with the configuration in which the random access control apparatus is the radio base station apparatus 101 as in the radio communication system according to the embodiment of the present invention, the setting of the random access signal in the radio communication system 301 is performed by each radio base station apparatus 101. Since this can be performed, it is possible to distribute the determination of the upper limit of the transmission power of the wireless terminal device 202 and the processing load of the setting regarding the random access signal.

  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.

DESCRIPTION OF SYMBOLS 11 Power limit part 12 Random access signal selection part 13 Cell radius information acquisition part 14 Movement information acquisition part 15 Trial number acquisition part 91 Antenna 92 Circulator 93 Wireless reception part 94 Wireless transmission part 95 Signal processing part 96 Reception signal processing part 97 Transmission signal Processing unit 98 Control unit 101 Wireless base station device 101A, 101B, 101C Femto base station 101D Pico base station 201 Macro base station 202 Wireless terminal device 203 Gateway device 204 Core network 205 Host device 301 Wireless communication system

Claims (11)

A power limiting unit for determining an upper limit of transmission power of a radio signal transmitted from a wireless terminal device to a target base station that is a target wireless base station device based on the predetermined information;
The wireless terminal device detects the wireless terminal device to adjust the transmission timing from the wireless terminal device to the target base station, and before the wireless terminal device establishes a communication connection with the wireless base station device, the wireless terminal One or a plurality of types of random access signals that can be used by the wireless terminal device among a plurality of types of random access signals based on the upper limit determined by the power limiter for a random access signal transmitted from a device A random access control device comprising: a random access signal selection unit for selecting The random access control device further includes:
A cell radius information acquisition unit for acquiring cell radius information capable of evaluating the cell radius of the target base station;
The random access control apparatus according to claim 1, wherein the power limiting unit determines the upper limit based on the cell radius information.   The random access control apparatus according to claim 2, wherein the power limiting unit sets the upper limit as the cell radius of the target base station increases. The random access control device further includes:
A movement information acquisition unit for acquiring failure information based on the number of failures of the movement operation of the wireless terminal device from another wireless base station device to the target base station;
The random access control device according to claim 1, wherein the power limiting unit determines the upper limit based on the failure information.   The random access control device according to claim 4, wherein the power limiting unit sets the upper limit as the number of failures or failure rate of the moving operation increases. The wireless terminal device repeatedly transmits the random access signal to the wireless base station device until the wireless base station device detects the random access signal,
The random access control device further includes:
A trial number acquisition unit for acquiring the number of transmissions of the random access signal from a wireless terminal device to the target base station until the target base station detects the random access signal;
The random access control apparatus according to claim 1, wherein the power limiting unit determines the upper limit based on the number of transmissions.   The random access control apparatus according to claim 6, wherein the power limiting unit sets the upper limit to be larger as the number of transmissions is larger.   The random access signal selection unit can use the wireless terminal device among a plurality of types of the random access signals based on a CM (Cubic Metric) value determined by the upper limit determined by the power limiting unit. The random access control apparatus according to claim 1, wherein a plurality of types of random access signals are selected.   A radio base station apparatus comprising the random access control apparatus according to claim 1.   A management apparatus that manages one or a plurality of radio base station apparatuses and includes the random access control apparatus according to claim 1. A random access control program used in a random access control device, the computer,
Determining the upper limit of the transmission power of the radio signal transmitted from the radio terminal device to the target base station which is the target radio base station device based on the predetermined information;
The wireless terminal device detects the wireless terminal device to adjust the transmission timing from the wireless terminal device to the target base station, and before the wireless terminal device establishes a communication connection with the wireless base station device, the wireless terminal Selecting one or a plurality of types of random access signals that can be used by the wireless terminal device from a plurality of types of random access signals based on the determined upper limit for a random access signal transmitted from a device; A random access control program to be executed.

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