JP5399860B2 - Base station apparatus, handover control method, and radio communication network system - Google Patents

Description

  The present invention relates to handover control using channel estimation that is performed when a person on a moving body such as an automobile or a train performs wireless communication with a terminal such as a mobile phone while moving, and in particular, a base station of a movement source The present invention relates to a handover control method for switching connection from a device to a destination base station device and a control device using the same.

  One wireless communication means performed between a base station and a terminal is WiMAX (Worldwide Interoperability for Microwave Access). WiMAX is a wireless communication system that provides broadband wireless access standardized based on the IEEE (Institute of Electrical and Electronics Engineers) standard 802.16e, and is expected especially as a high-speed mobile communication system, and a standard has been established. .

  The WiMAX network includes a base station (BS) and a terminal (MS), and the base station and the terminal communicate with each other wirelessly, but the terminal moves (the user who owns the terminal moves). As a result, when the communication state with the base station (serving base station) that is currently receiving the connection service deteriorates when the cell (range where the BS and the MS can wirelessly communicate) is reached, the communication state becomes more stable. Alternatively, it is necessary to switch the connection to a base station (target base station) with a small load.

  As a handover method for switching the connection from the serving base station to the target base station, two types of terminal-initiated handover activated from the terminal and base station-initiated handover activated from the base station are defined.

  The handover procedure between the terminal and the serving base station in the terminal-initiated handover is performed when the appropriate conditions for performing the handover are satisfied, the terminal together with the list of the target base stations to be handed over and the signal level information together with the terminal handover request (MOB_MSHO-REQ) A message is sent to the serving base station, and the serving base station confirms whether the next target base station can provide the service currently provided to the terminal in response to the message, and an appropriate base station that can be the target base station. And a base station handover request (MOB_BSHO-RSP) message including information such as a list of available service levels and the service level. The terminal that has received the base station handover request message transmits a handover completion notification (MOB_HO-IND) message including target base station information (base station ID) to the serving base station if the handover condition is satisfied. To complete the handover procedure with the serving base station. As an appropriate condition for performing the handover, a method based on the CINR (Carrier to Interference plus Noise Ratio) value of the terminal can be considered.

  On the other hand, the handover procedure between the terminal and the serving base station in the base station initiated handover is generally performed for adjusting the load balance of the base station. When handover is performed between the terminal and the serving base station in this case, before the handover is started, the CINR value of the terminal is monitored on the serving base station side, thereby confirming handover related information (service provision status) for the terminal. Do. In addition, the serving base station exchanges handover-related information with respect to the terminal through communication on a backhaul (a line for connecting to the backbone network) with an adjacent base station. The serving base station selects an appropriate target base station by its own algorithm (processing procedure) based on the handover related information for the terminal of its own station and the handover related information for the terminal of the adjacent base station, and sends a BSHO-REQ ( Base station handover request) message. This message includes a handover mode (forced or recommended mode), a list of target base stations, a handover procedure optimization field, an authentication policy, and the like. If the terminal that has received the message determines that the environment is suitable for handover based on the signal level of the target base station, serviceable information, etc., the HO-IND (handover notification) including the target base station ID A handover is notified by sending a message to the serving base station. The subsequent handover procedure is the same as the handover sequence procedure and necessary traffic (number of messages) in the terminal initiated handover.

  FIG. 7 is a block diagram showing an example of the configuration of the conventional base station apparatus as described above. The wireless unit 1 performs wireless communication with a wireless terminal device (not shown) to transmit and receive data. First, processing of the base station apparatus when data is received from the wireless terminal apparatus will be described. Data received by the wireless unit 1 from the wireless terminal device is transmitted to the signal processing unit 2. An FFT (Fast Fourier Transform) unit 21 of the signal processing unit 2 deletes the guide interval (GI) from the input signal, and a plurality of subcarrier signals are reproduced by the Fast Fourier Transform. The channel estimation processing unit 22 accurately estimates the multipath state of the signal received for equalization from the pilot arrangement of the signal reproduced by the FFT unit 21. The demodulation processing unit 23 demodulates the signal whose pilot has been corrected by the channel estimation processing unit 22 into user data. Next, the demodulated data transmitting unit 24 gives the demodulated data (uplink user data) to the demodulated data receiving unit of the control processing unit 3.

  The uplink user data is received by the demodulated data receiving unit 31 of the control processing unit 3, and the uplink user data is supplied to the server 4.

  Next, processing of the base station apparatus when transmitting data to the wireless terminal apparatus will be described. Downlink user data from the server 4 is received by the modulation data receiving unit 27 of the signal processing unit 2 via the data scheduler unit 35 of the control processing unit 3 and supplied to the modulation processing unit 28. In the modulation processing unit 28, the downlink user data is modulated by, for example, the OFDM system, and the next iFFT unit 29 performs inverse fast Fourier transform. Then, a GI is inserted into the output signal and sent to the radio unit 1. Then, it is transmitted from the wireless unit 1 to the wireless terminal device.

Japan Radio Industry Association, “OFDMA Broadband Mobile Wireless Access System (WiMAXTM applied in Japan) ARIB STD-T94 Version 1.4“, [online], March 18, 2009, Japan Radio Industry Association, [October 27, 2009 Day search], Internet (URL: http://www.arib.or.jp/english/html/overview/doc/1-STD-T94v1_4-1p2.pdf and http://www.arib.or.jp/ english / html / overview / doc / 1-STD-T94v1_4-2p2.pdf)

  In a WiMAX communication system, for example, when a plurality of users who have terminals move on a train and the plurality of terminals simultaneously reach the vicinity of a cell boundary, particularly in terminal-driven handover, the serving base station It is expected to make a handover request for As described above, when each terminal independently performs the handover sequence, control message communication is generated by the number of terminals, and the radio traffic is drastically reduced. In addition, the handover between the users cannot be performed smoothly due to the collision between the processes between the users.

  Even in the base station initiated handover, in the method in which the handover instruction is performed based on the CINR value of the terminal, the same problem occurs when a plurality of terminals reach the vicinity of the cell boundary at the same time.

  In view of the problems described above, the present invention provides a base station that can smoothly perform handover of each terminal without causing a decrease in radio traffic even when a plurality of terminals simultaneously reach the vicinity of a cell boundary. The purpose is to provide a device.

  In order to achieve the above object, the present invention provides a base station that performs wireless communication with a plurality of wireless terminal devices that move at the same time, wherein the base station uses each wireless terminal from a signal obtained by wireless communication with each wireless terminal device. The information on the movement of the device is acquired, the wireless terminal devices having similar information on the movement are managed as a group, and the base station is information indicating communication states with the plurality of wireless terminal devices belonging to the group. When a value based on the threshold value is equal to or less than a predetermined threshold, information for specifying a target base station is transmitted to the plurality of wireless terminal apparatuses belonging to the group.

  According to the present invention, the base station apparatus receives data of each wireless terminal apparatus that provides services, acquires information related to movement of each wireless terminal apparatus, and groups wireless terminal apparatuses with similar information regarding movement. When performing handover, the base station side can collectively issue a handover instruction to one group, so that it is not necessary for each wireless terminal device to independently generate a handover sequence, This will reduce traffic drop. Note that the information regarding the movement of each wireless terminal device necessary for grouping is information that can be determined that a plurality of wireless terminal devices are moving in the same way. For example, the moving direction and moving speed of the wireless terminal devices are Conceivable.

  Further, the present invention is characterized in that the information indicating the communication state between the base station and the plurality of wireless terminal devices belonging to the group is an average value of CINR values of the plurality of wireless terminal devices belonging to the group. And

  According to the present invention, when the average CINR value becomes low, the base station apparatus can collectively issue a handover instruction to each radio terminal apparatus belonging to the group.

  Further, the present invention is characterized in that the information specifying the target base station is a base station ID and authentication information.

  According to the present invention, before the base station issues a handover instruction to each wireless terminal device, the target base station displays the number of wireless terminal devices that may be handed over and the authentication information of the wireless terminal device. Therefore, when a handover request is made, the handover can be completed quickly and wireless communication with each wireless terminal device can be started.

  In the present invention, the wireless communication means between the plurality of wireless terminal devices and the base station is WiMAX, and information specifying the target base station is transmitted to the plurality of wireless terminal devices belonging to the group. As a means for transmitting, a message of a multicast CID in which the plurality of wireless terminal devices belonging to the group are designated as receiving terminals is used.

  According to the present invention, it is not necessary for the base station to create a control message including a handover instruction for each wireless terminal device belonging to the group, and by specifying each wireless terminal device as a receiving terminal, a message of one multicast CID can be transmitted. By using it, a plurality of wireless terminal apparatuses belonging to the group can receive the handover instruction and complete the handover, so that a handover instruction can be issued to more wireless terminal apparatuses at a time.

  Further, the present invention provides a handover control method in which a base station that performs radio communication with a plurality of radio terminal devices that move simultaneously performs handover control for the plurality of radio terminal devices, wherein the base station communicates with each radio terminal device. Obtaining information related to movement of each wireless terminal device from a signal obtained by communication; managing each wireless terminal device having similar information related to movement as a group; and the base station and the group belonging to the group Determining whether a value based on information indicating communication states with a plurality of wireless terminal devices is equal to or less than a predetermined threshold, and when the value based on information indicating communication state is equal to or less than a predetermined threshold, Transmitting information specifying a target base station to the plurality of wireless terminal devices belonging to a group, That.

  The present invention also provides a plurality of wireless terminal devices that move, a base station that performs wireless communication with the plurality of moving wireless terminal devices, and a target base station that the plurality of moving wireless terminal devices approach, In the wireless communication network system comprising: the wireless communication means is WiMAX, and the base station calculates a moving speed and a moving direction of each wireless terminal device from a signal obtained by wireless communication with each wireless terminal device. The plurality of wireless terminal devices moving at the same speed in the same direction are managed as one group, and the base station has a CINR value indicating a communication state with the plurality of wireless terminal devices belonging to the group in advance. When the threshold value is less than or equal to the predetermined threshold, the base station ID and authentication information for identifying the target base station are received by the plurality of wireless terminal devices belonging to the group The use of messages of a multicast CID specified as end, and transmitting to the plurality of radio terminal apparatuses belonging to the group

  According to the present invention, even when a plurality of terminals reach the vicinity of a cell boundary at the same time, handover of each terminal can be performed smoothly without causing a decrease in radio traffic.

FIG. 3 is a first block diagram showing an example of a configuration of a base station apparatus of the present invention. FIG. 5 is a first flowchart showing an example of processing in a signal processing unit of the base station apparatus of the present invention. FIG. 5 is a second flowchart showing an example of processing in the control processing unit of the base station apparatus of the present invention. FIG. 3 is a first diagram showing an example of grouping performed by the control processing unit of the base station apparatus of the present invention. FIG. 6 is a second diagram illustrating an example of a handover notification that the base station apparatus of the present invention makes to the target base station. FIG. 4 is a third diagram showing an example of a base station list that the server of the base station apparatus of the present invention has. FIG. 10 is a second block diagram showing an example of the configuration of a conventional base station apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

[First embodiment]
FIG. 1 is a block diagram showing an example of a configuration of a base station apparatus according to the present invention. In addition, about the part which overlaps with FIG. 7, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In FIG. 1, the channel estimation processing unit 22 performs an accurate estimation on the multipath state of the signal received for equalization from the pilot arrangement of the demodulated signal processed by the FFT unit 21 as in the conventional configuration of FIG. A signal subjected to pilot correction is given to the demodulation processing unit 23, and at the same time, an estimated channel estimation result is given to the first wireless terminal device data processing unit 25. The first wireless terminal device data processing unit 25 calculates first wireless terminal device data from the channel estimation result. The first wireless terminal device data is the moving direction and moving speed of the wireless terminal device. As a method for calculating the moving speed of the wireless terminal device, for example, there is a method of obtaining the moving speed of the wireless terminal device based on the maximum Doppler frequency (see JP-A-11-234190). The first wireless terminal device data processing unit 25 gives the calculated first wireless terminal device data to the demodulated data transmission unit 24.

  Similarly to the conventional configuration, the demodulation processing unit 23 demodulates the signal whose pilot has been corrected by the channel estimation processing unit 22 into user data and provides the signal amplitude to the second wireless terminal device data processing unit 26. . The second wireless terminal device data processing unit 26 calculates the received CINR value of the wireless terminal device based on the signal amplitude, and supplies it to the demodulated data transmission unit 24.

  The demodulated data receiving unit 31 in the control processing unit 3 transmits normal uplink user data to the server 4. In addition, data other than normal uplink user data (data calculated by the first wireless terminal device data processing unit 25 and the second wireless terminal device data processing unit 26) is given to the handover user management processing unit 32. The handover user management processing unit 32 lists the received information for each wireless terminal device, and sorts based on the first wireless terminal device data. Specifically, when the moving speed and the moving direction are the same and the moving speed is equal to or higher than a certain speed, the plurality of wireless terminal devices (users having wireless terminal devices) move on a train or bus. A plurality of wireless terminal devices that are determined to be moving by the same means are managed as one group.

  FIG. 4 is an example of grouping performed by the handover user management processing unit 32 of the control processing unit 3 of the base station apparatus of the present invention. Since the reception subframe includes UL-Burst for storing uplink user data, grouping of wireless terminal devices (users having wireless terminal devices) moving in the same moving speed and moving direction is performed using this UL-Burst. .

  In addition, the handover user management processing unit 32 notifies the handover control processing unit 33 to instruct the wireless terminal device to perform handover based on the second wireless terminal device data. Specifically, the determination is made based on CINR values of a plurality of wireless terminal devices managed as one group. Since the higher the CINR value, the better the radio wave condition, it is conceivable to notify when the average value of the CINR value is less than or equal to the threshold value.

  The handover control processing unit 33 that has received notification from the handover user management processing unit 32 that the average value of the CINR values of the wireless terminal devices has become equal to or less than the threshold value refers to the handover group target base station list stored in the server 4 And a control message including information on the target base station by determining the optimum base station as the next base station from the moving direction and moving speed of a plurality of wireless terminal devices managed as one group. Is created for each wireless terminal device, and the data scheduler 35 is instructed to transmit a control message to each wireless terminal device.

  FIG. 6 is a diagram showing an example of a base station list that the server of the base station apparatus of the present invention has. When there are a plurality of base stations adjacent to the serving base station that is currently being served by the wireless terminal device, the most appropriate base station is determined as the target base station from the moving direction, and the ID of the determined base station is determined. Notify the wireless terminal device.

[Second Embodiment]
In the first embodiment described above, the handover control processing unit 33 creates a control message for each wireless terminal device when giving a handover instruction to the wireless terminal device. However, in the second embodiment, the IEEE 802 Using WiMAX using 16 Series, BS and MS are connected by broadcast / multicast, and each wireless terminal device belonging to the first group is defined by one multicast CID. When this is performed for wireless terminal devices, it is not necessary to use a channel for each wireless terminal device, and a handover instruction can be issued to more wireless terminal devices at a time.

[Third embodiment]
In the third embodiment, in addition to the first and second embodiments described above, the target base station is notified of the number of wireless terminal devices that are expected to be handed over in the near future and the authentication information of the wireless terminal devices. To do. As a result, the target base station can acquire information on the wireless terminal device for which a handover request is made in advance, so that when the handover request is received from the wireless device terminal, the handover is quickly completed, and each wireless terminal device Can start wireless communication.

  FIG. 5 is a diagram illustrating an example of handover notification performed by the base station apparatus of the present invention to the target base station. Serving base station X manages users B, D, F, and G moving in the same moving speed and moving direction (moving by train) as one group among users A to G having wireless terminal devices, Monitor the received CINR values of these users. When the average CINR value of each user belonging to the group falls below the threshold, the base station Y is determined as a target base station from the moving direction and moving speed of the wireless terminal device, and a handover instruction is given to the wireless terminal device. At the same time, the target base station Y is notified of the number of wireless terminal devices (users B, D, F, and G) and the authentication information of the wireless terminal device.

  FIG. 2 is a flowchart showing an example of processing in the signal processing unit of the base station apparatus of the present invention. When the signal processing unit 2 receives the reception signal from the wireless unit 1, in step S01, the signal processing unit 2 performs fast Fourier transform on the reception signal, and proceeds to step S02.

  In step S02, channel estimation is performed, and in step S03 based on the channel estimation result, the first wireless terminal device data processing unit 25 calculates the moving speed and moving direction of the user having the wireless terminal device. Further, the signal subjected to the pilot correction in step S02 is given to the demodulation processing unit 23 (step S04).

  When the demodulation processing unit 23 receives the signal, in step S05, the second wireless terminal device data processing unit 26 measures the CINR value of the wireless terminal device from the IQ signal amplitude. Then, the demodulation processing unit 23 demodulates the IQ signal into user data in step S06.

  In step S07, the data from step S03, step S05, and step S06 are collected and supplied to the control processing unit 3.

  Since the processing from step S01 to step S07 is performed for each user when a plurality of users exist in the received frame, the processing is completed for all users in the received frame in step S08. If the process is not completed, the process returns to step S01 to start the process for the next user. If the processing of all users is completed, the processing for the frame in the signal processing unit 2 ends.

  FIG. 3 is a flowchart showing an example of processing in the control processing unit 3 of the base station apparatus of the present invention. When the demodulated data receiving unit 31 receives the uplink user data and the moving speed, moving direction, and CINR value information of the wireless terminal device from the signal processing unit 2 in step S11, the control processing unit 3 determines whether the data is normal uplink user data. Judging. If it is normal upstream user data, it is transmitted to the upstream server (step S12). On the other hand, information (movement speed, movement direction, CINR value) other than normal uplink user data is supplied to the HO (handover) user management processing unit 32 (step S13).

  The HO user management processing unit 32 updates the managed user list based on the received information (step S14). In step S15, the users are sorted based on the moving speed, and the users move at the same speed. Are grouped.

  Next, in step S16, the users who move at the same speed are sorted in the moving direction for each group, and thereby, for example, users who are moving on the same train are identified and managed as one group.

  Since the processing from step S11 to step S16 is performed for each user when a plurality of users exist in the received frame, the processing is completed for all users in the received frame in step S17. If the process has not been completed, the process returns to step S11 to start the process for the next user. If all the users have been processed in step S17, the process proceeds to step S18.

  In step S18, the serving base station calculates an average value for each group for the CINR value that serves as a reference for instructing the MS to perform handover. In step S19, when the average value is equal to or less than the threshold value, the process proceeds to step S20.

  When the average CINR value in the group is equal to or less than the threshold, the HO control processing unit 33 refers to the list of base stations adjacent to the base station stored in advance in the server 4, the MS moving speed, and the moving direction. The most appropriate base station is determined as the target base station, a HO instruction message to be applied to users belonging to the group is generated, and a transmission instruction is issued to the data scheduler unit 35 (step S20). Thereby, the process of the control processing unit 3 for the group in which the average value of the CINR values is equal to or less than the threshold value ends.

<< Deformation, etc. >>
As mentioned above, although an example of the embodiment of the present invention was explained, the present invention is not limited to these contents. As the embodiment, various modifications can be made without departing from the gist of the present invention.

  The present invention can be used for a base station apparatus that gives a handover instruction to a radio terminal apparatus.

DESCRIPTION OF SYMBOLS 1 Radio | wireless part 2 Signal processing part 3 Control processing part 4 Server 21 FFT part 22 Channel estimation processing part 23 Demodulation processing part 24 Demodulated data transmission part 25 1st wireless terminal device data processing part 26 2nd wireless terminal device data processing part 27 Demodulated Data Receiving Unit 28 Modulation Processing Unit 29 iFFT Unit 31 Demodulated Data Receiving Unit 32 Handover User Management Processing Unit 33 Handover Control Processing Unit 35 Data Scheduler Unit

Claims (6)

In a base station that performs wireless communication with a plurality of wireless terminal devices that move simultaneously,
The base station obtains at least information related to the moving direction as information related to movement of each wireless terminal device from a signal obtained by wireless communication with each wireless terminal device, and groups the wireless terminal devices having the same moving direction. Manage as
When the value based on the information indicating the communication state with the plurality of wireless terminal devices belonging to the group is equal to or less than a predetermined threshold value, the base station applies to the plurality of wireless communication terminals belonging to the group based on the moving direction. A base station apparatus that determines a target base station and transmits information for specifying the target base station to the plurality of radio terminal apparatuses belonging to the group.   The information indicating the communication state between the base station and the plurality of wireless terminal devices belonging to the group is an average value of CINR values of the plurality of wireless terminal devices belonging to the group. The base station apparatus as described.   The base station apparatus according to claim 1 or 2, wherein the information specifying the target base station is a base station ID and authentication information. The wireless communication means between the plurality of wireless terminal devices and the base station is WiMAX,
As means for transmitting information identifying the target base station to the plurality of wireless terminal devices belonging to the group, a message of a multicast CID specifying the plurality of wireless terminal devices belonging to the group as receiving terminals is used. The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. In a handover control method in which a base station that performs wireless communication with a plurality of wireless terminal devices that move simultaneously performs handover control on the plurality of wireless terminal devices,
The base station obtaining at least information relating to the moving direction as information relating to movement of each wireless terminal device from a signal obtained by wireless communication with each wireless terminal device;
Managing the wireless terminal devices having the same moving direction as a group;
Determining whether a value based on information indicating a communication state between the base station and the plurality of wireless terminal devices belonging to the group is equal to or less than a predetermined threshold;
Determining a target base station for the plurality of wireless communication terminals belonging to the group based on the moving direction when it is determined that a value based on the information indicating the communication state is equal to or less than a predetermined threshold;
And transmitting information identifying the target base station to the plurality of radio terminals belonging to said group,
A handover control method comprising : A plurality of moving wireless terminal devices;
A base station performing wireless communication with the plurality of moving wireless terminal devices;
In a wireless communication network system comprising a target base station to which the plurality of moving wireless terminal devices approach,
The wireless communication means is WiMAX,
The base station obtains at least information related to the moving direction as information related to movement of each wireless terminal device from a signal obtained by wireless communication with each wireless terminal device, and groups the wireless terminal devices having the same moving direction. Manage as
The base station, when a CINR value indicating a communication state with the plurality of wireless terminal devices belonging to the group falls below a predetermined threshold, a target base for the plurality of wireless communication terminals belonging to the group based on the moving direction determining the station, the base station ID and authentication information for identifying the target base station, by using a message of multicast CID specifying the plurality of wireless terminal devices belonging to the group as a receiving terminal belonging to the group A wireless communication network system, wherein transmission is performed to the plurality of wireless terminal devices.

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