JP6245465B2 - Wireless communication apparatus and wireless base station switching method - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a wireless base station switching method for switching a wireless base station to which wireless communication is connected.

  2. Description of the Related Art In recent years, cellular mobile communication systems have been actively studied on technologies for realizing high transmission rate communication using a high-frequency wireless communication band in order to transmit large amounts of data as information becomes multimedia. ing. Cellular mobile communication systems are classified into, for example, LTE (Long Term Evolution), 3G (3rd Generation), W-CDMA (Wideband Code Division Multiple Access) and CDMA2000, and 2G (2nd Generation). There exist communication systems such as GSM (Global System for Mobile Communications) (registered trademark).

  A wireless communication device (hereinafter abbreviated as “wireless terminal”) that can be connected to a plurality of communication methods is connected to a wireless base station device (hereinafter abbreviated as “wireless base station”) to which wireless communication is connected. Measurement of radio quality information (hereinafter referred to as “radio quality information”) and each radio quality information between one or more radio base stations existing around the radio base station using periodic or threshold values To do. The wireless terminal transmits the wireless quality information of the measurement result to the connected wireless base station.

  When the wireless quality information between the wireless terminal and the connected wireless base station falls below a predetermined threshold, the wireless terminal measures the wireless quality information of surrounding wireless base stations and notifies the connected wireless base station. The connected radio base station notifies the radio terminal of a handover instruction to connect to a new radio base station (handover destination) in order to continue radio communication. The wireless terminal can continue the wireless communication by switching the wireless communication connection destination to the handover target wireless base station by executing a handover procedure with the handover target wireless base station specified by the handover instruction. .

  Here, for example, a mobile terminal disclosed in Patent Literature 1 is known as a prior art related to handover for switching a wireless base station to which wireless communication is connected.

  The mobile terminal shown in Patent Document 1 can be connected to a plurality of base stations with different communication schemes, and when it is determined to perform handover, the transmission rate in the current communication scheme (for example, LTE) before the handover is performed. Is changed to a transmission rate in a new communication system (for example, 3G W-CDMA system). After changing to the transmission rate in the new communication method, the mobile terminal generates a quality measurement report result including information related to the handover, and transmits the quality measurement report result to the connection destination base station.

  As a result, the mobile terminal disclosed in Patent Document 1 can stably transmit data even when a handover is performed to a communication network whose transmission rate usable for data transmission is lower than the current rate. A large amount of data is not stored in the buffer, and a large amount of transmission packets can be prevented from staying on the wireless network.

International Publication No. 2013/031114

  In Patent Literature 1, when radio quality information between a mobile terminal and a connection destination base station deteriorates, the mobile terminal receives a handover instruction regarding the new connection destination from the current connection destination base station.

  Here, for example, when the mobile terminal is moving at high speed, the handover destination base station is switched one after another, so that the mobile terminal completes the handover procedure and performs wireless communication with the new connection destination base station. Even if communication is started, it is necessary to execute handover to another base station. That is, when the mobile terminal is moving at high speed, the number of handover procedures increases, and there is a problem that stable data communication becomes difficult.

  In Patent Document 1, the mobile terminal can predict the execution of the handover before executing the handover. However, for example, when the mobile terminal is moving at a high speed, it is not assumed that the number of handovers increases. It is thought that the issues that have been solved are not solved.

  In order to solve the above-described conventional problems, the present invention suppresses an increase in the number of handover procedures even when moving at high speed, for example, and a radio communication apparatus and a radio base that stably realize data communication An object is to provide a station switching method.

The present invention is a wireless communication apparatus connectable to a plurality of wireless base stations including a current communication destination base station and a new communication destination base station, and a wireless unit that communicates with each of the plurality of wireless base stations; , Estimating a moving speed of the wireless communication device based on a measurement unit that periodically measures wireless quality information between each of the wireless base stations and a change amount of the wireless quality information measured periodically A prediction unit that predicts execution of a handover that switches a radio base station that is a radio communication destination of the radio communication device based on the measured radio quality information, and after execution of the handover is predicted a first radio quality information measured on the basis of a second radio quality information measured after the execution condition of predetermined said handover is satisfied, the candidate radio base station before Symbol new was Do passing Shinsaki base station and a estimator to estimate the When the moving speed of the radio communication device is equal to or higher than a predetermined value, the estimation unit determines the candidate radio base station based on the moving speed, the first radio quality information, and the second radio quality information. The radio unit transmits a radio quality measurement report including information related to a handover with the candidate radio base station inferred by the estimation unit to a radio base station of a current radio communication destination, If the moving speed of the radio communication device is less than the predetermined value, the Ru was continued prediction of execution of the handover by the prediction unit, a wireless communication device.

The present invention also relates to a radio base station switching method in a radio communication apparatus connectable to a plurality of radio base stations including a current communication destination base station and a new communication destination base station , wherein the plurality of radio base stations The step of communicating with each of the steps, the step of periodically measuring the wireless quality information between each of the wireless base stations, and the wireless communication based on the amount of change of the wireless quality information measured periodically Estimating the moving speed of a device, and predicting execution of a handover for switching a radio base station of a radio communication destination of the radio communication device based on the measured radio quality information , the radio when the moving speed of the communication device is a predetermined value or more, the and the moving speed, the execution condition of the first radio quality information and a predetermined said handover execution of the handover has been measured after predicted Handover between the steps of the guess candidate radio base station of the new was Do passing Shinsaki base station and the second radio quality information measured and based on after being Tasa, and was estimated the candidate radio base station the radio quality measurement report containing information on, and sending the current wireless communication destination radio base station, and further have a, when the moving speed of the radio communication device is less than the predetermined value, the handover A radio base station switching method that continues the step of predicting execution .

  According to the present invention, for example, even when moving at high speed, an increase in the number of handover procedures can be suppressed, and data communication can be realized stably.

(A) Operation | movement outline | summary figure which shows an example of the procedure of the handover between the radio | wireless terminal of a prior art, and a radio base station, (B) An example of the procedure of the handover between the radio | wireless terminal of this embodiment and a radio base station Operation overview diagram A block diagram showing an example of an internal configuration of a wireless terminal according to the present embodiment FIG. 3 is a sequence diagram illustrating an example of a time-series signaling procedure among the radio terminal, the source radio base station, and the target radio base station according to the present embodiment.

  Hereinafter, embodiments of a wireless communication apparatus and a wireless base station switching method according to the present invention will be described using a wireless terminal as an example of the wireless communication apparatus with reference to the drawings. The mobile communication system of the present embodiment described below includes the wireless terminal of the present embodiment as a mobile body and a plurality of wireless base stations that communicate with the wireless terminal via a wireless communication network.

  In addition to the device category invention, the present invention can also be expressed as a method category invention of a radio base station switching method as an operation in which a radio communication device switches a connection-destination radio base station.

  The wireless terminal is a wireless communication device that can be connected to a plurality of wireless base stations having different communication methods, and is a data communication terminal such as a mobile phone, a smartphone, or a tablet terminal.

  For example, if the communication method is LTE, the radio base station is E-UTRAN (Evolved Universal Terrestrial Radio Access Network) Node B: eNB, and if the communication method is 3G, for example, Node B: NB It is. The radio base station may be an overhang base station (Remote Radio Head: RRH), a relay device (for example, a repeater or a relay node), a femto base station, or a pico base station.

  The mobile communication system of this embodiment to be described below is a 3G system such as the LTE system, W-CDMA system or CDMA2000 system standardized in 3GPP (The 3rd Generation Partnership Project), 2G such as GSM (registered trademark). A system using two or more networks using each mobile communication technology may be used, or a system corresponding to the same communication method may be used.

(Outline of operation of this embodiment)
First, with reference to FIG. 1, an outline of the operation of the wireless terminal of the present embodiment will be described by comparing the related art with the present embodiment. FIG. 1A is a schematic operation diagram illustrating an example of a procedure for handover between a wireless terminal and a wireless base station according to the prior art. FIG. 1B is an operation outline diagram illustrating an example of a procedure for handover between the radio terminal UE and the radio base station according to the present embodiment.

  In FIG. 1 (A) and FIG. 1 (B), the user driving the passenger car CR has a wireless terminal, that is, the wireless terminal is moving at high speed, and the wireless terminal is currently connected to the wireless base station BS1. A description will be given assuming a situation in which wireless communication is started. In FIG. 1A and FIG. 1B, three radio base stations are illustrated for ease of explanation, but the number is not limited to three.

  In FIG. 1A, when the wireless terminal starts connection with the wireless base station BS1, the wireless terminal receives an instruction of a condition (HO condition, HO: handover) for executing a handover (step [1]). In the HO condition, a threshold value (for example, a lower limit value) of radio quality information (for example, received electric field level or SN: Signal to Noise ratio) for executing a handover is designated. The wireless terminal periodically measures the current wireless quality information with the wireless base stations BS1 to BS3, and transmits the measurement result to the currently connected wireless base station BS1.

  Here, when the radio quality information between the radio terminal and the radio base station BS1 falls below a predetermined threshold specified in the HO condition, the radio terminal selects a candidate radio base station as a new handover destination radio base station. Search (step [2]). Specifically, the radio terminal measures radio quality information between the radio base stations BS1 to BS3, and transmits the measurement result to the radio base station BS1 that is the current connection destination (step [2]).

  Based on the measurement result from the wireless terminal, the wireless base station BS1 determines the candidate wireless base station having a good wireless quality as a new handover destination wireless base station as the wireless base station BS2, and The wireless terminal is instructed to perform the handover procedure at (Step [2]).

  In response to an instruction from the radio base station BS1, the radio terminal starts a handover procedure with the new radio base station BS2 as a handover destination (step [3]). When the handover procedure between the radio terminal and the radio base station BS2 is completed, the radio terminal switches the connection-destination radio base station from the radio base station BS1 to the radio base station BS2, and establishes a connection with the radio base station BS2. Wireless communication is started (step [4]). Further, when the wireless terminal starts connection with the wireless base station BS2, the wireless terminal receives an instruction of a condition (HO condition) for executing handover from the wireless base station BS2.

  After a certain period of time has elapsed after the wireless terminal starts wireless communication with the wireless base station BS2, the wireless quality information between the wireless terminal and the wireless base station BS2 has a predetermined threshold specified in the HO condition. If it falls below, the search for a candidate radio base station as a new handover destination radio base station is repeated (step [5]).

  Therefore, in the prior art shown in FIG. 1 (A), when the wireless terminal is moving at high speed, after the wireless base station to which wireless communication is connected is switched from the wireless base station BS1 to the wireless base station BS2, Since the time until the HO condition for executing the handover procedure is shortened, the number of handovers increases. For this reason, it is difficult for the wireless terminal to perform data communication stably.

  Next, in FIG. 1B, when the wireless terminal starts connection with the wireless base station BS1, the wireless terminal receives an instruction of an HO condition for executing a handover (step [1]). The wireless terminal periodically measures the current wireless quality information with the wireless base stations BS1 to BS3, and transmits the measurement result to the currently connected wireless base station BS1.

  Based on the measurement result of the wireless quality information, the wireless terminal uses a predetermined threshold in which the wireless quality information with the currently connected wireless base station BS1 is specified in the HO condition after a certain time (for example, 1.5 seconds). Is predicted (step [2]). Further, the radio terminal measures the radio quality information between the radio base stations BS1 to BS3 after predicting the execution of the handover after a certain time (step [2]).

  Here, when the radio quality information between the radio terminal and the radio base station BS1 falls below a predetermined threshold specified in the HO condition, the radio terminal selects a candidate radio base station as a new handover destination radio base station. Search (step [3]). Specifically, the radio terminal measures radio quality information between the radio base stations BS1 to BS3, and based on the measurement results measured in steps [2] and [3] shown in FIG. In addition, information on the traveling method of the passenger car CR, that is, information on the wireless base station BS3 existing in the moving direction of the wireless terminal is transmitted to the currently connected wireless base station BS1 as information on a new handover destination candidate wireless base station. (Step [3]).

  The radio base station BS1 determines the candidate radio base station as a new handover destination radio base station as the radio base station BS3 based on the information about the candidate radio base station transmitted from the radio terminal, and the radio base station BS3 The wireless terminal is instructed to perform a handover procedure between the terminals (step [3]).

  In response to an instruction from the radio base station BS1, the radio terminal starts a handover procedure with a new handover destination radio base station BS3 (step [4]). When the handover procedure between the radio terminal and the radio base station BS3 is completed, the radio terminal switches the connection-destination radio base station from the radio base station BS1 to the radio base station BS3, and establishes a connection with the radio base station BS3. Wireless communication is started (step [5]). Further, when the wireless terminal starts connection with the wireless base station BS3, the wireless terminal receives an instruction of a condition (HO condition) for executing handover from the wireless base station BS3.

  When a certain period of time has elapsed after the wireless terminal starts wireless communication with the wireless base station BS3, the wireless quality information between the wireless terminal and the wireless base station BS3 has a predetermined threshold specified in the HO condition. If it falls below, the search for a candidate radio base station as a new handover destination radio base station is repeated (step [6]).

  Therefore, in the present embodiment shown in FIG. 1B, since the wireless terminal predicts the execution of handover before a certain time before the execution timing of the handover, even if the wireless terminal is moving at high speed, Based on the amount of change of each radio quality information measured after the HO condition is satisfied, the new handover destination radio base station is not the radio base station BS2 close to the radio terminal, for example, but the moving direction of the radio terminal It is assumed that the radio base station BS3 exists (for example, in the traveling direction). Thereby, the wireless terminal can suppress an increase in the number of handovers, and can stably realize data communication.

(Configuration of wireless terminal)
FIG. 2 is a block diagram illustrating an example of an internal configuration of the radio terminal UE of the present embodiment. The radio terminal UE shown in FIG. 2 includes a radio unit 11 to which a transmission antenna ATX and a reception antenna ARX are connected, a radio control unit 13, a handover prediction unit 15, a movement estimation unit 17, and a candidate radio base station estimation unit 19 A terminal control unit 21, a tone control unit 23 connected to the speaker SP1, a voice control unit 25 connected to the speaker SP2 and the microphone MIC, a display unit 27, and a UI (User Interface) unit 29. . Note that the transmitting antenna and the receiving antenna may be the same antenna.

  The radio unit 11 modulates the transmission data signal output from the radio control unit 13 according to the communication method with any one of the radio base stations BS1 to BS3, and the modulated transmission data signal Is converted into a predetermined high-frequency signal and transmitted from the transmission antenna ATX. Further, the radio unit 11 receives a high-frequency signal transmitted from any one of the radio base stations BS1 to BS3 at the reception antenna ARX, and according to a communication method with any one of the radio base stations. The received high-frequency signal is converted into a baseband received data signal, and the received data signal is demodulated and output to the wireless control unit 13.

  The radio unit 11 receives, for example, a radio quality information measurement setting message (Measurement Configuration) transmitted from the radio base station BS1 and information for measuring radio quality information, and outputs the information to the radio control unit 13. In the radio quality measurement setting message, as an example of a condition (HO condition) for executing handover, the radio terminal UE transmits a radio quality information measurement result report (Measurement Report) to the currently connected radio base station. MR transmission conditions for doing this are described.

  The MR transmission conditions include, for example, information related to an index of radio quality information necessary for executing handover (for example, information indicating that a received electric field level or SN is used as an index) and a received electric field for executing handover. A predetermined level threshold (lower limit) is designated. Further, for example, when the MR transmission condition is satisfied during the data communication using the LTE communication network, the wireless terminal UE may perform a handover after a certain period of time has elapsed since the MR transmission condition is satisfied. Is considered high.

  The information for measuring the radio quality information is, for example, pilot channel information including a reference signal. The radio unit 11 receives position information of the radio terminal UE in GPS (Global Positioning System), a control signal from the radio base station, user data, or a handover instruction signal.

  The wireless control unit 13 includes a wireless quality management unit 13a and a scan management unit 13b, and controls operations necessary for wireless connection such as call connection, authentication, location registration, handover, and roaming.

  The radio quality management unit 13a monitors and manages radio quality information (for example, received electric field level and noise level) necessary for executing handover or roaming, measured by the scan management unit 13b. The radio quality management unit 13a generates a transmission data signal of a measurement result report including radio quality information measured by the scan management unit 13b, or information on a procedure for executing handover or roaming, and outputs the transmission data signal to the radio unit 11 . The radio quality management unit 13a extracts the MR transmission condition from the radio quality information measurement setting message output from the radio unit 11, and the MR transmission condition and the radio quality information periodically measured by the scan management unit 13b. To the handover prediction unit 15 (output).

  The scan management unit 13b has carrier frequency and carrier information for selecting a radio base station for each radio base station BS1 to BS3, and between the radio base stations BS1 to BS3 to which the radio terminal UE can be connected. Periodically measure radio quality information and search for connectable radio base stations. The scan management unit 13b outputs wireless quality information as a search result (measurement result) to the wireless quality management unit 13a.

  The scan management unit 13b periodically measures radio quality information (for example, received electric field level) from a pilot channel including a reference signal received by the radio unit 11, for example. The radio quality information includes the radio quality information of the signal from the radio base station to which the radio terminal UE is currently connected (for example, the radio base station BS1) and each radio base existing around the current radio base station of the connection destination. Radio quality information of the signal from the station.

  The measured value of the radio quality information is RSRP (Reference Signal Received Power) or RSRQ (Reference Signal Received Quality) if the communication method used by the radio terminal UE during radio communication is LTE, and the communication method is UTRA (UMTS Terrestrial Radio Access). ) RSCP (Received Signal Code Power) or Ec / N0, RSSI (Received Signal Strength Indicator) if the communication method is GERAN, and pilot signal power if the communication method is CDMA2000.

  Further, the scan management unit 13b determines whether the MR transmission condition described in the radio quality measurement setting message transmitted from the currently connected radio base station (for example, the radio base station BS1) is satisfied, that is, The radio terminal UE determines whether or not to send a measurement result report of radio quality information to the radio base station of the current connection destination.

  The handover predicting unit 15 predicts time information (for example, indicating how long a HO prediction completion notification described later should be output to the movement estimating unit 17 from the timing when the MR transmission condition is likely to be actually satisfied. 1.5 seconds) as a set value. The predicted time information indicates the time from the timing at which the handover predicting unit 15 predicts the execution of the handover to the timing at which the MR transmission condition is likely to be actually satisfied. The predicted time information is a value defined in advance in the operation of the handover predicting unit 15, but may be changed as appropriate by rewriting the contents of a program that defines the operation of the handover predicting unit 15.

  In response to the notification of the MR transmission condition from the radio quality management unit 13a, the handover prediction unit 15 changes the radio quality information periodically measured by the scan management unit 13b (for example, the radio quality information for each predetermined unit). (Slope) is used to predict when the MR transmission condition is satisfied.

  More specifically, the handover predicting unit 15 elapses a predetermined time (for example, 1.5 seconds) corresponding to the predicted time information based on the amount of change of each radio quality information between the radio base stations BS1 to BS3. Later, it is predicted that there is a high possibility that the received electric field level specified in the MR transmission condition falls below a predetermined threshold value (lower limit value), that is, the possibility of executing a handover is high. If the handover predicting unit 15 predicts that there is a high possibility that the handover will be executed after elapse of a certain time (for example, 1.5 seconds) corresponding to the predicted time information, the HO prediction indicating that the handover prediction has been completed. The completion notification is output to the movement estimation unit 17.

  Therefore, the MR transmission condition is actually satisfied after a lapse of a certain time (for example, 1.5 seconds) corresponding to the prediction time information from the timing when the HO prediction completion notification is output from the handover prediction unit 15 to the movement estimation unit 17. The possibility is likely to increase.

  Note that the handover predicting unit 15 holds the location information of the radio terminal UE received by the GPS receiver when the radio terminal UE holds the map information and road information of the radio base station and further has a GPS receiver. The handover may be predicted to be performed after a certain period of time by comparing the location information on the cell provided by each radio base station.

  The movement estimation unit 17 estimates the movement speed and movement direction of the radio terminal UE based on the amount of change in the radio quality information periodically measured by the scan management unit 13b. The movement estimation unit 17 is a radio base station that is the next handover destination of the radio terminal UE when it is estimated that the estimated movement speed of the radio terminal UE is equal to or higher than a predetermined value, that is, is moving at high speed. An instruction for inferring the candidate radio base station is output to the candidate radio base station estimation unit 19 including the moving speed and moving direction of the radio terminal UE.

  If the movement estimation unit 17 determines that the movement speed of the detected radio terminal UE is less than a predetermined value, that is, does not move at high speed, the movement estimation unit 17 cancels the handover prediction according to the HO prediction completion notification. Then, the handover prediction unit 15 continues the prediction of the handover again.

  The movement estimation unit 17 may calculate a movement distance and a movement direction of the radio terminal UE by calculating a movement distance per unit time of the radio terminal UE using, for example, a GPS receiver, or, for example, a gyro You may obtain | require the moving speed and moving direction of the radio | wireless terminal UE from the inclination or acceleration of the radio | wireless terminal UE using a sensor.

  When the candidate radio base station estimation unit 19 receives the instruction output from the movement estimation unit 17, the radio base station existing around the radio terminal UE at the output timing of the instruction from the movement estimation unit 17 according to the HO prediction completion notification In order to acquire each information of the station and the wireless quality information, the wireless control unit 13 is instructed to search (scan) the wireless base station. The candidate radio base station estimation unit 19 acquires each information (first scan data) of the radio base station and the radio quality information measured by the radio control unit 13 after the execution of the handover is predicted. Further, the candidate radio base station estimation unit 19 acquires each information (second scan data) of the radio base station and the radio quality information measured by the radio control unit 13 in the same manner even after the MR transmission condition is satisfied. To do.

  Candidate radio base station estimation unit 19 is based on the movement speed and movement direction of radio terminal UE output from movement estimation unit 17 and the first scan data and second scan data obtained from radio control unit 13. A candidate radio base station that is a radio base station that is the next handover destination of the radio terminal UE is estimated. That is, the candidate radio base station estimation unit 19 uses the movement speed and movement direction of the radio terminal UE output from the movement estimation unit 17 and the first scan data and the second scan data obtained from the radio control unit 13. Thus, the wireless quality information with each wireless base station at the timing when the handover procedure is completed is calculated.

  Specifically, the candidate radio base station estimation unit 19 increases radio quality information with a radio base station (for example, the radio base station BS3) existing in the moving direction (traveling direction) of the radio terminal UE, By adjusting the radio quality information so as to reduce the radio quality information between the radio base stations (for example, the radio base station BS2) existing in the vicinity, the radio base station at the timing when the handover procedure is completed is adjusted. The wireless quality information is calculated. Note that the candidate radio base station estimation unit 19 may estimate the candidate radio base station using the radio quality information of the first scan data and the second scan data obtained from the radio control unit 13 as they are.

  For example, the first scan data of the radio quality information between the radio base station BS3 and the radio terminal UE 1.5 seconds before the timing at which the handover is started is -80 dB, and the handover is started. It is assumed that the second scan data of the radio quality information between the radio base station BS3 and the radio terminal UE at the timing is −76 dB.

  In this case, the candidate radio base station estimation unit 19 assumes that it takes 1 second from the start of the handover procedure to the completion of the handover procedure, and the moving direction (traveling direction) of the radio terminal UE when the handover procedure is completed The wireless quality information between the wireless base station BS3 and the wireless terminal UE existing in the wireless terminal UE is adjusted so as to increase the wireless quality information of the second scan data, for example, −74 dB (= −76 + ({| −80 | -| (-76) |} / 2).

  Further, the first scan data of the radio quality information between the radio base station BS2 and the radio terminal UE 1.5 seconds before the timing at which the handover is started is −73 dB, and the execution of the handover is started. It is assumed that the second scan data of the radio quality information between the radio base station BS2 and the radio terminal UE at the timing is −77 dB.

  In this case, the candidate radio base station estimation unit 19 assumes that it takes 1 second from the start of the handover procedure to the completion of the handover procedure, and the moving direction (traveling direction) of the radio terminal UE when the handover procedure is completed The radio quality information between the radio base station BS2 and the radio terminal UE existing around the radio base station BS3 existing in is adjusted so as to reduce the radio quality information of the second scan data, for example, −79 dB ( = −77 + ({| −73 | − | (−77) |} / 2).

  Thereby, the candidate radio base station estimation unit 19 replaces the radio base station BS3 existing in the moving direction of the radio terminal UE with the candidate radio base station that is the next handover destination radio base station, based on the calculation result of the radio quality information. A station is estimated and information on the estimation result is output to the radio control unit 13. Note that the candidate radio base station estimation unit 19 may cause the display unit 27 to display information on the estimation result of the candidate radio base station that is the next handover destination radio base station via the terminal control unit 21.

  The terminal control unit 21 is configured using, for example, a processor, and outputs a control signal for controlling the operation of each unit of the radio terminal UE to each corresponding unit. The processor is, for example, a central processing unit (CPU), a micro processing unit (MPU), or a digital signal processor (DSP).

  The tone control unit 23 controls the sound output in the speaker SP1 according to the control signal from the terminal control unit 21, and when there is an incoming signal from any one of the radio base stations BS1 to BS3, a predetermined signal is received. A ring tone is output from the speaker SP1. Further, the tone control unit 23 outputs a buzzer sound or an alarm sound at the speaker SP1 in accordance with a control signal from the terminal control unit 21.

  The voice control unit 25 controls voice output at the speaker SP2 and voice pickup at the microphone MIC in accordance with a control signal from the terminal control unit 21, and receives an incoming call from any one of the radio base stations BS1 to BS3. When there is a signal, the microphone MIC picks up the user's voice and the voice from the other party is output from the speaker SP2.

  The display unit 27 displays display target data on the screen in accordance with a control signal from the terminal control unit 21. For example, the display unit 27 displays information related to the estimation result of the candidate radio base station that is the next handover destination radio base station estimated by the candidate radio base station estimation unit 19.

  The UI unit 29 is a user interface for a user to input an operation on the radio terminal UE, and outputs an operation command signal corresponding to the operation content of the user to the terminal control unit 21. For example, when the wireless terminal UE is a smartphone or a tablet terminal, the UI unit 29 is configured using a touch panel that is arranged on the display unit 27 and can accept an input operation with a user's finger or stylus pen. For example, when the wireless terminal UE is a mobile phone, the UI unit 29 can be configured by using various keys such as a numeric keypad for inputting a telephone number, a telephone key for performing on-hook or off-hook, and a function key. .

(Wireless terminal operation)
Next, regarding time-series signaling between the radio terminal UE of the present embodiment, the radio base station (source radio base station) BS1 that is the current connection destination, and the radio base station BS3 that is the next handover destination, This will be described with reference to FIG. FIG. 3 is a sequence diagram illustrating an example of a time-series signaling procedure among the radio terminal UE, the source radio base station BS1, and the target radio base station BS3 according to the present embodiment.

  For example, the source radio base station BS1 is a radio base station compatible with the LTE communication scheme, and the target radio base station BS3 is a radio base station compatible with the 3G communication scheme. In the description of FIG. 3, the radio base station that is the current connection destination of the radio terminal UE is described as “source radio base station”, and the radio base station that is the new connection destination of the radio terminal UE is “ It is described as “target radio base station”.

  In order to simplify the description of FIG. 3, the radio terminal UE performs scanning processing in steps S18 and S21, that is, performs processing for measuring radio quality information between the radio base station and the radio terminal UE. Although shown, the scan management unit 13b of the wireless control unit 13 may actually perform the scan processing shown in step S18 and step S21 periodically without being limited to the time point of step S18 and step S21.

  Further, in the description of FIG. 3, it is assumed that the MR transmission condition is satisfied at the time of step S20, that is, the radio quality information between the radio terminal UE and the source radio base station BS1 is below a predetermined threshold (lower limit value). . Therefore, it is assumed that the MR transmission condition is not satisfied until the time of step S20, that is, the radio quality information between the radio terminal UE and the source radio base station BS1 does not fall below a predetermined threshold (lower limit value).

  In FIG. 3, the source radio base station BS1 transmits a radio quality information measurement setting message (Measurement Configuration) including an MR transmission condition to the radio terminal UE (S11). When the radio terminal UE receives the radio quality information measurement setting message, the radio quality management unit 13a of the radio control unit 13 extracts the MR transmission conditions described in the radio quality information measurement setting message, and performs handover estimation unit 15 Is notified (output) (S12).

  In response to the notification of the MR transmission condition from the radio quality management unit 13a in step S12, the handover predicting unit 15 changes the amount of radio quality information periodically measured by the scan management unit 13b (for example, radio for each predetermined unit). Based on the inclination of the quality information, it is predicted when the MR transmission condition is satisfied (S13).

  More specifically, the handover predicting unit 15 elapses a predetermined time (for example, 1.5 seconds) corresponding to the predicted time information based on the amount of change of each radio quality information between the radio base stations BS1 to BS3. Later, it is predicted that there is a high possibility that the received electric field level specified in the MR transmission condition falls below a predetermined threshold value (lower limit value), that is, a high possibility of executing a handover (S13). If the handover predicting unit 15 predicts that there is a high possibility that the handover will be executed after elapse of a certain time (for example, 1.5 seconds) corresponding to the predicted time information, the HO prediction indicating that the handover prediction has been completed. A completion notification is output to the movement estimation unit 17 (S14).

  The movement estimation unit 17 estimates the movement speed and movement direction of the radio terminal UE based on the amount of change in the radio quality information periodically measured by the scan management unit 13b (S15). When the movement estimation unit 17 estimates that the movement speed of the radio terminal UE is equal to or higher than a predetermined value, that is, is moving at high speed, the movement estimation unit 17 is a candidate radio base that is a radio base station that is the next handover destination of the radio terminal UE An instruction to infer the station is output to the candidate radio base station estimation unit 19 including the moving speed and moving direction of the radio terminal UE (S16).

  When the candidate radio base station estimation unit 19 receives an instruction from the movement estimation unit 17 in step S16, the candidate radio base station estimation unit 19 includes radios existing around the radio terminal UE at the output timing of the instruction from the movement estimation unit 17 according to the HO prediction completion notification In order to acquire each information of the base station and the wireless quality information, the wireless control unit 13 is instructed to search (scan) the wireless base station (S17).

  When the scan management unit 13b of the radio control unit 13 receives an instruction from the candidate radio base station estimation unit 19 in step S17, the radio quality information between the source radio base station BS1 and the radio terminal UE, and the source radio base station Each radio quality information between other radio base stations existing around BS1 and the radio terminal UE is measured (S18). The scan management unit 13b notifies (outputs) the measured radio quality information to the candidate radio base station estimation unit 19 as first scan data (S19).

  Here, it is assumed that the MR transmission condition is satisfied, that is, the radio quality information between the radio terminal UE and the source radio base station BS1 falls below a predetermined threshold (lower limit value) (S20). After the MR transmission condition is satisfied, the scan management unit 13b of the radio control unit 13 transmits the radio quality information between the source radio base station BS1 and the radio terminal UE and other radio signals existing around the source radio base station BS1. Each radio quality information between the radio base station and the radio terminal UE is measured (S21). The scan management unit 13b notifies (outputs) each measured radio quality information to the candidate radio base station estimation unit 19 as second scan data (S22).

  The candidate radio base station estimation unit 19 includes the moving speed and moving direction of the radio terminal UE obtained from the movement estimation unit 17 in step S16, the first scan data obtained from the radio control unit 13 in step S19, and step S22. In step S23, a candidate radio base station that is a radio base station that is the next handover destination of the radio terminal UE is estimated based on the second scan data obtained from the radio control unit 13 in step S23. That is, the candidate radio base station estimation unit 19 uses the movement speed and movement direction of the radio terminal UE output from the movement estimation unit 17 and the first scan data and the second scan data obtained from the radio control unit 13. Thus, the wireless quality information with each wireless base station at the timing when the handover procedure is completed is calculated.

  Specifically, the candidate radio base station estimation unit 19 increases radio quality information with a radio base station (for example, the radio base station BS3) existing in the moving direction (traveling direction) of the radio terminal UE, By adjusting the radio quality information so as to reduce the radio quality information between the radio base stations (for example, the radio base station BS2) existing in the vicinity, the radio base station at the timing when the handover procedure is completed is adjusted. The wireless quality information is calculated.

  Based on the calculation result of the radio quality information, the candidate radio base station estimation unit 19 uses the radio base station BS3 (target radio base station BS3) existing in the moving direction of the radio terminal UE as the next handover destination radio base station. A candidate radio base station is estimated and information about the estimation result is notified (output) to the radio control unit 13 (S24).

  In response to the notification from the candidate radio base station estimation unit 19 in step S24, the radio quality management unit 13a of the radio control unit 13 performs radio quality information between the source radio base station BS1 and the radio terminal UE, and a new handover. A measurement report (Measurement Report) including radio quality information between the previous target radio base station BS3 and the radio terminal UE is generated (S25). The radio terminal UE transmits the measurement result report (Measurement Report) generated in Step S25 to the source radio base station BS1 (S26).

  When the source radio base station BS1 receives the measurement result report transmitted in step S26, the source radio base station BS1 performs radio communication between the source radio base station BS1 and the target radio base station BS3 that is the new handover destination specified in the measurement result report. Preparation for a handover procedure for switching the connection destination of the terminal UE is started (S27).

  Specifically, the source radio base station BS1 transmits a handover instruction (HO command) for executing a handover with the target radio base station BS3 as a new handover destination to the radio terminal UE (S28), The uplink data (UL: Uplink) transmitted from the radio terminal UE and the downlink data (DL: Downlink) to be transmitted to the radio terminal UE are transferred to the target radio base station BS3 (S29).

  When receiving a handover instruction from the source radio base station BS1 in step S28, the radio terminal UE first uses, for example, a random access channel (RACH) to send a short preamble to the target radio base station BS3. Transmit (S30).

  When the target radio base station BS3 receives the preamble transmitted in step S30, the target radio base station BS3 performs a process of allocating radio resources and communication timing related to the uplink (UP) from the radio terminal UE, and indicates that the allocation process has been performed. A message is transmitted to the radio terminal UE as a response to the preamble transmitted in step S30 (S31).

  When receiving the response transmitted in step S31, the radio terminal UE completes the handover procedure between the radio terminal UE and the target radio base station BS3, and the connection destination of the radio terminal UE is changed from the source radio base station BS1 to the target. After the communication path (path) is changed so as to switch to the radio base station BS3, a notification (RRC Connection Reconfiguration Complete) indicating that the connection state of RRC (Radio Resource Control) is reconfigured is sent to the target radio base. The data is transmitted to the station BS3 (S32). Thereby, the radio terminal UE can stably continue data communication with the source radio base station BS1 with the new target radio base station BS3 switched by the handover.

  As described above, the radio terminal UE of the present embodiment can be connected to a plurality of radio base stations, and periodically measures radio quality information (for example, received electric field level) between the radio base stations BS1 to BS3. The execution of the handover is predicted based on the amount of change in the received electric field level. That is, the radio terminal UE predicts that a predetermined handover execution condition is satisfied after a predetermined time based on the amount of change in the received electric field level.

  The radio terminal UE uses the first radio quality information (for example, the first received electric field level) measured immediately after the execution of the handover is predicted and the second radio measured immediately after a predetermined handover execution condition is satisfied. A candidate radio base station to be a new handover destination is estimated based on the quality information (for example, the second received electric field level). The radio terminal UE transmits a radio quality measurement report (measurement report) including information related to the handover with the estimated candidate radio base station to the radio base station BS1 of the current radio communication destination.

  Therefore, the radio terminal UE predicts handover execution a predetermined time before the timing at which a predetermined handover execution condition is satisfied, and based on the measured amount of change in received electric field level, a new handover destination candidate radio base Guess the station. Thereby, even when the radio terminal UE moves at high speed between cells provided by a plurality of radio base stations, for example, the radio terminal UE suppresses an increase in the number of handover procedures, and the radio base station of the current radio communication destination Data communication can be transferred to the next wireless base station of the wireless communication destination, so that data communication can be realized stably.

  Hereinafter, the configuration, operation, and effect of the above-described radio communication apparatus and radio base station switching method according to the present invention will be described.

  One embodiment of the present invention is a wireless communication apparatus connectable to a plurality of wireless base stations, and a measurement unit that periodically measures wireless quality information with each of the wireless base stations, Based on the radio quality information, a prediction unit that predicts execution of a handover that switches a radio base station that is a radio communication destination of the radio communication device; first radio quality information measured after the execution of the handover is predicted; An estimation unit that estimates a candidate radio base station of a new radio communication destination of the radio communication device based on second radio quality information measured after a predetermined execution condition of the handover is satisfied And a wireless unit that transmits a wireless quality measurement report including information related to a handover with the candidate wireless base station to a wireless base station that is a current wireless communication destination.

  In the configuration described above, the radio terminal UE can be connected to a plurality of radio base stations having different mobile communication systems, and periodically transmits radio quality information (for example, received electric field level) between the radio base stations BS1 to BS3. And the execution of the handover is predicted based on the amount of change in the received electric field level. That is, the radio terminal UE predicts that a predetermined handover execution condition is satisfied after a predetermined time based on the amount of change in the received electric field level.

  The radio terminal UE uses the first radio quality information (for example, the first received electric field level) measured immediately after the execution of the handover is predicted and the second radio measured immediately after a predetermined handover execution condition is satisfied. A candidate radio base station to be a new handover destination is estimated based on the quality information (for example, the second received electric field level). The radio terminal UE transmits a radio quality measurement report (measurement report) including information related to the handover with the estimated candidate radio base station to the radio base station BS1 of the current radio communication destination.

  Therefore, the radio terminal UE predicts handover execution a predetermined time before the timing at which a predetermined handover execution condition is satisfied, and based on the measured amount of change in received electric field level, a new handover destination candidate radio base Guess the station. Thereby, even when the radio terminal UE moves at high speed between cells provided by a plurality of radio base stations, for example, the radio terminal UE suppresses an increase in the number of handover procedures, and the radio base station of the current radio communication destination Data communication can be transferred to the next wireless base station of the wireless communication destination, so that data communication can be realized stably.

  In addition, according to an embodiment of the present invention, the movement estimation that estimates a moving speed of the wireless communication apparatus based on a change amount of the wireless quality information measured periodically in response to completion of prediction of the execution of the handover. A wireless communication device further comprising a unit.

  In the configuration described above, when the execution of the handover is predicted, the radio terminal UE estimates the moving speed of the radio terminal UE based on the amount of change in the received electric field level measured periodically. For example, when the moving speed is not high, that is, when the moving speed of the radio terminal UE is less than a predetermined threshold, it is considered that the radio terminal UE does not need to frequently switch the handover destination radio base station.

  As a result, when the radio terminal UE is not moving at high speed, that is, when the moving speed of the radio terminal UE is less than a predetermined threshold, the radio terminal UE does not guess a candidate radio base station as a new handover destination, The power consumption of the terminal UE can be reduced.

  In one embodiment of the present invention, the estimation unit moves the wireless communication device based on each change amount of the first wireless quality information and the second wireless quality information and a moving direction of the wireless communication device. The second radio quality information between the radio base stations existing in the direction is increased by a predetermined amount, and the second radio quality information between the radio base stations existing around the radio base station existing in the moving direction of the radio communication device is increased. (2) A wireless communication device that reduces wireless quality information by a predetermined amount.

  In the configuration described above, the radio terminal UE increases the second radio quality information (second received electric field level) with the radio base station existing in the moving direction by a predetermined amount, and radios existing around the radio base station. Second radio quality information (second received electric field level) with the base station is decreased by a predetermined amount.

  Thereby, the radio | wireless terminal UE can estimate the candidate radio base station used as a new handover destination with high precision, when the execution conditions of predetermined | prescribed handover are satisfy | filled.

  Moreover, one Embodiment of this invention is a radio | wireless communication apparatus further provided with the display part which displays the information regarding the estimated said candidate radio base station.

  Thereby, the radio | wireless terminal UE can make a user visually recognize the information regarding the candidate radio base station used as a new handover destination.

  Also, an embodiment of the present invention is a radio base station switching method in a radio communication device connectable to a plurality of radio base stations, and periodically measures radio quality information with each of the radio base stations. A step of predicting execution of a handover for switching a radio base station of a radio communication destination of the radio communication device based on the measured radio quality information, and measuring after the execution of the handover is predicted Based on the first radio quality information and the second radio quality information measured after the predetermined execution condition for the handover is satisfied, a candidate radio base station of a new radio communication destination of the radio communication device is estimated. And a step of transmitting a radio quality measurement report including information on handover to the estimated candidate radio base station to the radio base station of the current radio communication destination. It is a wireless base station switching method.

  In the method described above, the radio terminal UE can be connected to a plurality of radio base stations having different mobile communication systems, and periodically transmits radio quality information (for example, received electric field level) between the radio base stations BS1 to BS3. And the execution of the handover is predicted based on the amount of change in the received electric field level. That is, the radio terminal UE predicts that a predetermined handover execution condition is satisfied after a predetermined time based on the amount of change in the received electric field level.

  The radio terminal UE uses the first radio quality information (for example, the first received electric field level) measured immediately after the execution of the handover is predicted and the second radio measured immediately after a predetermined handover execution condition is satisfied. A candidate radio base station to be a new handover destination is estimated based on the quality information (for example, the second received electric field level). The radio terminal UE transmits a radio quality measurement report (measurement report) including information related to the handover with the estimated candidate radio base station to the radio base station BS1 of the current radio communication destination.

  Therefore, the radio terminal UE predicts handover execution a predetermined time before the timing at which a predetermined handover execution condition is satisfied, and based on the measured amount of change in received electric field level, a new handover destination candidate radio base Guess the station. Thereby, even when the radio terminal UE moves at high speed between cells provided by a plurality of radio base stations, for example, the radio terminal UE suppresses an increase in the number of handover procedures, and the radio base station of the current radio communication destination Data communication can be transferred to the next wireless base station of the wireless communication destination, so that data communication can be realized stably.

  While various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention is useful, for example, as a radio communication device and a radio base station switching method that suppresses an increase in the number of handover procedures and stably realizes data communication even when moving at high speed. For example, a mobile phone, a smartphone, or a tablet terminal.

UE radio terminal 11 radio unit 13 radio control unit 13a radio quality management unit 13b scan management unit 15 handover prediction unit 17 movement estimation unit 19 candidate radio base station estimation unit 21 terminal control unit 23 tone control unit 25 voice control unit 27 display unit 29 UI part ATX Transmit antenna ARX Receive antenna

Claims (5)

A wireless communication device connectable to a plurality of wireless base stations including a current communication destination base station and a new communication destination base station ,
A wireless unit that communicates with each of the plurality of wireless base stations;
A measurement unit that periodically measures radio quality information between each of the radio base stations;
A movement estimation unit for estimating a movement speed of the wireless communication device based on a periodically measured change amount of the wireless quality information;
Based on the measured wireless quality information, a prediction unit that predicts execution of a handover for switching a wireless communication destination wireless base station of the wireless communication device;
A first radio quality information, on the basis of a second radio quality information measured after the execution condition of predetermined said handover is satisfied, before Symbol Shin was Do passing measured after the execution of the handover has been predicted comprises a estimator to estimate a candidate radio base station of Shinsaki base station, a,
When the moving speed of the wireless communication device is a predetermined value or more,
The estimation unit estimates the candidate radio base station based on the moving speed, the first radio quality information, and the second radio quality information, and the radio unit is estimated by the estimation unit. A radio quality measurement report including information related to handover with the candidate radio base station is transmitted to the radio base station of the current radio communication destination,
When the moving speed of the wireless communication device is less than a predetermined value,
Wherein Ru is continued prediction of execution of the handover by the prediction unit,
Wireless communication device. The wireless communication device according to claim 1,
The movement estimation unit further estimates a moving direction of the wireless communication device,
The estimation unit estimates the candidate radio base station based on the moving speed and the moving direction, and the first radio quality information and the second radio quality information .
Wireless communication device. The wireless communication device according to claim 1 or 2 ,
The estimation unit is
Based on each change amount of the first radio quality information and the second radio quality information and the movement direction of the radio communication device, the second radio between the radio base station existing in the movement direction of the radio communication device. Increasing the quality information by a predetermined amount, and decreasing the second radio quality information between the radio base stations existing around the radio base station existing in the moving direction of the radio communication device by a predetermined amount;
Wireless communication device. The wireless communication device according to claim 1 or 2,
A display unit for displaying information on the estimated candidate radio base station;
Wireless communication device. A radio base station switching method in a radio communication device connectable to a plurality of radio base stations including a current communication destination base station and a new communication destination base station ,
Communicating with each of the plurality of radio base stations;
Periodically measuring radio quality information between each of the radio base stations;
Estimating a moving speed of the wireless communication device based on a periodically measured change amount of the wireless quality information;
Based on the measured wireless quality information, predicting the execution of handover for switching the wireless communication destination wireless base station of the wireless communication device , and
When the moving speed of the wireless communication device is a predetermined value or more,
Wherein a moving speed, the Xin based and the second radio quality information, a measured after the execution condition of the first radio quality information and a predetermined said handover execution of the handover has been measured after predicted is satisfied a step to estimate the Do through Shinsaki candidate radio base station of the base stations,
The radio quality measurement report including information about the handover between the inferred the candidate radio base station, and further organic and sending the current wireless communication destination radio base station, a,
When the moving speed of the wireless communication device is less than a predetermined value,
Continuing to predict execution of the handover;
Wireless base station switching method.

Images