JP6577876B2 - Control device, control method, and program - Google Patents

Description

  The present invention relates to a handover technique in wireless communication.

  In cellular communication, a plurality of base station devices each have a different coverage area, and a terminal device can receive a wireless communication service by connecting to a base station corresponding to the location where the user stays at that time. . The terminal device may move during communication and may leave the coverage area of the currently connected base station device. In this case, the terminal device switches the connection to another base station device having a coverage area including the location of the destination, for example, by executing a handover process in response to the radio quality being lower than a predetermined level, Communication can be continued.

  On the other hand, when the terminal device is moving at a high speed, the handover process performed in response to the radio quality being lower than a predetermined level results in the connection being disconnected before the process ends and the process fails. There can be. On the other hand, Patent Document 1 describes a method of starting a handover process without depending on radio quality from the position of a terminal device, a moving route, and a speed.

JP-A-10-191437

  While the technique described in Patent Literature 1 is effective for a terminal device that moves at high speed, the terminal device that performs low-speed movement can execute the handover process even if the handover process is not necessarily executed. There was a problem of being done.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for enabling a handover process to be executed by an appropriate method for each terminal device.

To achieve the above object, a control apparatus according to the present invention is a control apparatus for controlling a handover of a terminal device that performs wireless communication, a determination unit configured to determine characteristics of the terminal device, depending on the result of the determination A handover method to be executed by the terminal device is selected from a first handover method started in response to the measurement of the radio wave state by the terminal device and a second handover method started without the measurement. select, have a, a selection unit to be executed by the terminal device, the characteristics of the terminal device may include the terminal device adaptable frequency, the selection means, the terminal device is capable of supporting frequencies The second handover method is selected when the number is smaller than the number of frequencies that other terminal apparatuses can handle .

  According to the present invention, it is possible to execute a handover process by an appropriate method for each terminal device.

The figure which shows the structural example of a radio | wireless communications system. The figure which shows the hardware structural example of a control apparatus. The block diagram which shows the function structural example of a control apparatus. The flowchart which shows the flow of the process which a control apparatus performs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Wireless communication system)
FIG. 1 shows a configuration example of a wireless communication system according to this embodiment. The wireless communication system includes, for example, a long term evolution (LTE) base station device and a terminal device. In the present wireless communication system, a wireless communication technology other than LTE may be used. In the example of FIG. 1, only two base station apparatuses and one terminal apparatus are shown, but there may be three or more base station apparatuses or two or more terminal apparatuses. In addition, the plurality of base station apparatuses have a coverage area in which the terminal apparatus can execute handover, that is, a coverage area that overlaps or touches at least part of the coverage area of another adjacent base station apparatus.

  The terminal device performs wireless communication by connecting to one of the base station devices. In the present embodiment, as shown in FIG. 1, the terminal device is assumed to move from the coverage area developed by the first base station device to the coverage area developed by the second base station device. At this time, the terminal apparatus executes a handover for switching the connection destination base station apparatus from the first base station apparatus to the second base station apparatus.

  At this time, in this embodiment, the terminal device performs handover using one of a plurality of handover methods according to the state or characteristics of the terminal device under the control of the control device. That is, the control device determines the state or characteristics of the terminal device, selects a handover method to be executed by the terminal device according to the determination result, and causes the terminal device to execute the handover method. The control device may be provided, for example, in the base station device, or may be provided in a network node that can be accessed by the base station device via a wired line or a wireless line. The control device may be provided in the terminal device. Note that the function of the control device may be realized by a single device, or may be realized by being distributed among a plurality of devices. That is, in the following, a case where there is one control device will be mainly described. However, in practice, the functions of the control device may be shared by a plurality of devices.

  Here, the plurality of handover methods include, for example, a first handover method that is started in response to measurement of the radio wave condition and a second handover method that is started without measurement of the radio wave condition. The first handover method is, for example, a method that is started in response to the radio wave condition being measured in the terminal device, and as a result, the level falls below a predetermined level. The second handover method is, for example, a method for forcibly starting handover at a predetermined timing determined by the control device. Note that the classification of the handover method may be performed based on other criteria different from whether or not the measurement is started by measuring the radio wave condition. For example, the handover method may be classified depending on whether the handover is led by a terminal device, a base station device (network), or a hybrid thereof. For example, the handover method led by the base station device is selected when the base station devices connected to the terminal devices in the system should be collectively controlled, or when there is a high probability that the handover processing will fail according to the judgment by the terminal device. Can be done. Hereinafter, a switching technique between the first handover method and the second handover method will be described.

  Here, the state of the terminal device includes, for example, the moving speed of the terminal device, and the control device is started without measuring the radio wave state of the terminal device when the moving speed of the terminal device exceeds a predetermined value. A second handover method can be selected. According to this, it is possible to prevent an event in which the connection is disconnected before the handover process ends due to the terminal device moving at high speed. For this reason, the predetermined value described above can be set to a speed at which the probability that the handover process will fail exceeds a certain level. Note that the moving speed of the terminal device can be specified according to the time interval of the handover executed by the terminal device or the frequency at a predetermined time interval. That is, the shorter the time interval of the handover executed by the terminal device, and the higher the frequency of handover in the predetermined time interval, the faster the terminal device is expected to move, so according to these values, It is possible to estimate the moving speed of the terminal device. The fact that the handover is executed by the terminal device can be performed, for example, by measuring a handover signal notified from the terminal device to the base station device. Note that, for example, when the terminal device is alternately switching connections with two specific base station devices, it may be considered that the terminal device is merely present at the cell edge and is not moving at high speed. For this reason, the time interval or frequency of handover may be estimated, for example, ignoring the state where the connection is alternately switched between two specific base station apparatuses. Further, in the estimation of the time interval or frequency of handover, the position of the base station apparatus to be connected may be taken into consideration, and the movement path of the terminal apparatus that can be estimated therefrom may be taken into consideration. For example, in the case of a movement in which a route is specified, such as a railway line, a pattern of how a base station to which a terminal device connects transitions can be specified by handover. The moving speed may be estimated from the time interval. Also, since the frequency of handover failures tends to increase during high-speed movement, it may be determined whether the terminal device is moving at high speed from the time interval at which handover failed or the frequency of failure.

  The state of the terminal device includes, for example, the current date and time, and the control device can select the second handover method when the date and time is a predetermined date and time or included in a predetermined period. For example, the control device can select the second handover method that is started without measuring the radio wave condition of the terminal device in the commuting time zone. This prevents, for example, the start of handover at the same time due to the simultaneous deterioration of radio wave conditions caused by a large number of terminal devices moving together on a train or the like, thereby distributing the start timing of handover and thus the processing load. Can be made. For example, when a large number of terminal devices start handover processing at the same time, there will be a relative shortage of control channels that can be used, and handover processing may fail. By distributing the start timing of handover processing, Can prevent failure. In addition, the control device selects the first handover method because the number of terminal devices that may start handover at the same time during weekday days is considered to be significantly smaller than the commuting time zone. You may do it. Note that the control device may select the first handover method on weekends and the second handover method on weekdays, for example, even in the same commuting time zone.

  Further, the state of the terminal device includes, for example, the geographical position of the terminal device, and the control device selects the second handover method when the geographical position of the terminal device is included in a predetermined range. You can also For example, the control device can cause the second handover method to be used particularly by a terminal device staying along a congested train route. Conversely, the control device may cause the terminal device staying along the train line with a low degree of congestion to use the first handover method. As a result, it is possible to prevent handovers from being started all at once due to the deterioration of the radio wave state of a large number of terminal devices at the same time, and to distribute the start timing of the handover and thus the processing load. Further, the control device can select a handover method to be executed by the terminal device according to the geographical position and the date and time. For example, the control device uses the second handover method in the vicinity of a station in an office area during a commuting time zone on weekdays, while the first handover method is used in a residential area or a sightseeing spot even in a similar time zone. You may make it select.

  The state of the terminal device includes the total number of terminal devices including other terminal devices at the geographical location where the terminal device stays, and the control device, when the total number has reached a predetermined level, The second handover method may be selected. For example, certain places such as concerts and fireworks venues are not regularly crowded, but there are places that are not crowded at normal times but are crowded sporadically due to events or the like. In such a case, the control device can select a handover method to be executed by the terminal device according to the actual congestion level, not the time or geographical location. In other words, the control device should be executed by the terminal device when the total number of the terminal device and other terminal devices existing in a predetermined range including the geographical position of the terminal device has reached a predetermined level. As the handover method, the second handover method can be selected. Thereby, it can prevent that many terminal devices start a handover simultaneously.

  In addition, the state of the terminal device includes moving means used by the terminal device, and the control device is the first handover method to be used by the terminal device when the terminal device is moving by the predetermined moving means. Two handover methods may be selected. For example, when the terminal device is moving by a personal moving means such as a private car, even if the moving speed is high, starting the handover process simultaneously with many other terminal devices It is thought not to be. On the other hand, for example, when the terminal device is moving by a moving means that can transport a large number of personnel such as a train, the terminal device performs a handover process at the same time as many other terminal devices. Could start. For this reason, when the terminal device uses a moving means that moves in conjunction with the movement of a large number of other terminal devices, the terminal device uses the second handover method, so that a large number of terminal devices can be used simultaneously. Initiating a handover can be prevented.

  On the other hand, the characteristics of the terminal device include frequencies that can be supported by the terminal device. For example, the number of frequencies (number of bands) that can be supported by the terminal device is the frequency that can be supported by other terminal devices. If the number is less than the number, the second handover method may be selected. That is, it is easy to find a non-congested handover destination frequency if it is a terminal device that can handle many frequencies, while a non-congested handover destination is a terminal device that has few frequencies that can be handled. Probability of not being able to find any frequency increases. For this reason, the control device can reduce the probability that the terminal device will fail to perform handover by handing over a terminal device with a small number of frequencies that can be handled in advance without measuring the radio wave condition in the terminal device. Can be reduced.

  For example, when the second handover method is selected, the control apparatus can notify the terminal apparatus of the timing for executing the handover process (for example, via the base station apparatus). That is, in the first handover method, the radio wave condition is measured by the terminal device, and the handover is started according to the measurement result. Therefore, the terminal device is involved in the handover start. As a result, in the first handover method, it is not necessary to notify the terminal device of the timing for executing the handover. On the other hand, since the second handover method does not depend on the measurement of the radio wave state by the terminal device, it is assumed that the terminal device does not participate in the start of the handover. For this reason, the control device can perform control so as to notify the terminal device of the timing for executing the handover. Note that the control device may perform control so that a plurality of terminal devices are notified of different timings as timings at which handover is to be performed. Thereby, the timing at which the plurality of terminal apparatuses execute the handover can be shifted, and congestion of the control channel due to the concentration of the timing at which the handover is performed can be prevented.

  Note that the control device may perform control so as to notify the terminal device of the selection result when a handover method different from the handover method used by the terminal device during normal operation is selected. In this case, the control device can instruct the terminal device to switch the handover method again when returning to the handover method that is normally used. Note that the control device transmits a predetermined signal at a predetermined cycle to the terminal device, for example, after selecting a handover method different from the handover method used by the terminal device during normal operation and returning to the handover method used during normal operation. Control may be performed as described above. In this case, when a predetermined signal is not received at a predetermined period, the terminal device can recognize that the handover method to be used should be returned to the handover method used at the normal time. Note that the handover method to be used may be notified from the control device to the terminal device by a method other than the method described here.

  In addition, when the notified handover method to be used is different from the handover method used at the normal time, the terminal device may ignore the notification. For example, when the terminal device has already performed handover, or when the terminal device completes the handover process before the notified time, the terminal device itself is notified of the handover according to the state of the terminal device. It may be decided not to use the method. In addition, when ignoring the notified handover method, the terminal device may notify the control device of a notification that denies use of the notified handover method.

  Below, the structure of the control apparatus which performs such a process, and the flow of the process performed are demonstrated in detail.

(Hardware configuration of control device)
FIG. 2 shows a hardware configuration example of the control device. In one example, the control device has a hardware configuration as shown in FIG. 2, and includes, for example, a CPU 201, a ROM 202, a RAM 203, an external storage device 204, and a communication device 205. In the control device, for example, the CPU 201 executes a program that realizes each function of the control device as described above, which is recorded in any of the ROM 202, the RAM 203, and the external storage device 204.

  And a control apparatus controls the communication apparatus 205 by CPU201, for example, and performs communication between a base station apparatus and a terminal device. In addition, in FIG. 2, although the control apparatus has shown the schematic which has the one communication apparatus 205, it is not restricted to this. For example, when the control device is included in the base station device, the control device may include a communication device for communication with another base station device and a communication device with a terminal device. Furthermore, when the control device is included in the terminal device, the control device can include, for example, a communication device for communication with the base station device and a communication device for communication between other terminal devices. When the control device is a network node different from the base station device, the control device has at least a communication device for communicating with the base station device, and further has a communication device with another node. Good.

  Note that the control device may include dedicated hardware that executes each function, or may execute other portions by a computer that executes a part of the hardware and operates the program. All functions may be executed by a computer and a program.

(Functional configuration of control device)
FIG. 3 shows a functional configuration example of the control device. As described above, the control device determines at least one of the state and characteristics of the terminal device, and determines a handover method to be used by the terminal device according to the determination result. And a control apparatus can perform the predetermined | prescribed notification to a terminal device as mentioned above according to the determined handover method. That is, for example, when the second handover method is selected, the control device can notify the terminal device of the selection result and the timing for executing the handover. Each time the handover method to be used changes, the control device may transmit information that can specify the changed handover method to the terminal device, or during the selection of a method that is not a normally used handover method. This signal may be continuously transmitted.

  In order to execute such processing, the control device includes a communication unit 301, a state / characteristic determination unit 302, a handover method determination unit 303, and a notification control unit 304, for example, as shown in FIG. Here, a case where the control apparatus exists on the network side, that is, a case where it is included in the base station apparatus or exists as a network node different from the base station apparatus will be described. However, the control apparatus is included in the terminal apparatus. It may be included. In this case, the control device may not include the notification control unit 304, for example.

  The communication unit 301 performs at least one of wired communication and wireless communication. For example, when the control device is a network node, the communication unit 301 transmits a signal to the base station device and receives a signal from the base station device, for example, via a wired line. In this case, the communication unit 301 can communicate with the terminal device via the base station device. Here, a wireless line may be used for communication between the network node and the base station apparatus. Moreover, when a control apparatus is included in a base station apparatus, the communication part 301 is used in order to communicate between a terminal device and a network node, for example. When the control device is included in the terminal device, the communication unit 301 is used to perform communication with the base station device, for example.

  The state / characteristic determination unit 302 determines at least one of the state and characteristic of the terminal device. In one example, the state / characteristic of the terminal device includes at least one of a moving speed, a date and time, a geographical position, a congestion degree, a moving means used, and a compatible frequency, as described above. The handover method determination unit 303 selects a handover method to be used by the terminal device as described above based on the result determined by the state / characteristic determination unit 302. Note that other states / characteristics of the terminal device may be determined. For example, the remaining battery level of the terminal device may be determined, and the handover method may be selected so as to reduce the number of times handover is performed in the terminal device with a low battery level.

  The notification control unit 304 performs control such as notification of the handover method to be used to the terminal device according to the determination result by the handover method determination unit 303. For example, when the handover method determining unit 303 selects a handover method different from the currently used handover method, the notification control unit 304 notifies the terminal device of the selected handover method. On the other hand, when the handover method determining unit 303 continues to select the currently used handover method, the notification control unit 304 may perform control so that no special notification is sent to the terminal device. In addition, as described above, the notification control unit 304 performs control so that a predetermined signal is continuously transmitted to the terminal device when a method different from the handover method to be used in the normal state is selected. Also good. Note that the notification control unit 304 performs control so as to notify the terminal device of the timing at which handover is to be performed, for example, when the above-described second handover method that is not based on measurement of radio wave conditions is used. At this time, the notification control unit 304 may perform control so that a plurality of terminal devices are notified of different timings as timings at which a handover should be performed.

(Process flow)
Next, the flow of processing executed by the control device will be described with reference to FIG. First, the control device specifies at least one of the state and characteristics of the terminal device by acquiring information about the terminal device from, for example, the terminal device or the base station device, or some network node (S401). Here, the state of the terminal device includes, for example, the moving speed of the terminal device, the current date and time, the geographical position of the terminal device, the degree of congestion in the vicinity of the terminal device, and the moving means used by the terminal device (having the user). In addition, the characteristics of the terminal device include frequencies that can be handled. It should be noted that only a part of these states / characteristics may be specified, or a state / characteristic different from these states / characteristics may be specified.

  Subsequently, the control device determines whether the moving speed of the terminal device specified in S401 exceeds a predetermined value (S402), and if it exceeds the predetermined value (YES in S402), the terminal device uses it. The second handover method is selected as the power handover method (S409). Here, as described above, the second handover method is a method in which the handover process is started without being based on the measurement of the radio wave state by the terminal device. When the moving speed of the terminal device is equal to or lower than the predetermined value (NO in S402), the control device subsequently determines whether the current date and time is included in the predetermined period (S403). Here, it may be determined whether the current date is a predetermined date.

  When the current date and time is included in the predetermined period (YES in S403), the control device selects the second handover method as the handover method to be used by the terminal device (S409). On the other hand, if the current date and time are not included in the predetermined period (NO in S403), the control device subsequently determines whether the geographical location where the terminal device currently exists is included in the predetermined range. Is determined (S404).

  When the current geographical position of the terminal device is included in the predetermined range (YES in S404), the control device selects the second handover method as the handover method to be used by the terminal device (S409). ). On the other hand, when the current geographical position of the terminal device is not included in the predetermined range (NO in S404), the control device subsequently determines that the degree of congestion around the terminal device exceeds a predetermined level. (S405). This determination can be made based on the total number of terminal devices and other terminal devices existing around the terminal devices.

  If the degree of congestion around the terminal device exceeds a predetermined level (YES in S405), the control device selects the second handover method as the handover method to be used by the terminal device (S409). On the other hand, when the degree of congestion around the terminal device is equal to or lower than the predetermined level (NO in S405), the control device subsequently determines that the number of frequencies that can be handled by the terminal device is other terminals around the terminal device. It is determined whether the frequency is less than the number of frequencies that the device can handle (S406). For example, the control device may acquire information on the model of each terminal device or information on capability managed on the network side, and perform this determination based on the acquired information.

  When the number of frequencies that can be supported by the terminal device is smaller than the number of frequencies that can be supported by other terminal devices around the terminal device (YES in S406), the control device is the first handover method that should be used by the terminal device. The second handover method is selected (S409). On the other hand, when the number of frequencies that can be supported by the terminal device is equal to or greater than the number of frequencies that can be supported by other terminal devices around the terminal device (NO in S406), It is determined whether (user) is moving by a predetermined moving means (S407).

  When it is determined that the terminal device (the user) is moving by a predetermined moving means (YES in S407), the control device selects the second handover method as the handover method to be used by the terminal device (S409). . On the other hand, if it is determined that the terminal device (the user) has not moved by the predetermined moving means (NO in S407), the first handover method is selected as the handover method to be used by the terminal device (S408). That is, when all the determinations in S402 to S407 are “NO”, the control device selects the first handover method as the handover method to be used by the terminal device (S408). Here, as described above, the first handover method is a method in which the handover process is started based on the measurement of the radio wave state by the terminal device.

  Note that some of the determinations in S402 to S407 may be omitted, or determinations regarding other states / characteristics may be performed. Further, the order of the determinations in S402 to S407 may be different from the order shown in FIG. 4, and furthermore, in FIG. 4, these determinations are shown to be performed sequentially, but these determinations are performed in parallel. It may be done. In addition, since the specific example of the criterion of S402-S407 is as above-mentioned, for example, detailed description is abbreviate | omitted.

  Thereafter, the control device notifies the selected handover method to the terminal device as necessary (S410). For example, when the terminal apparatus uses the first handover method, the control apparatus is configured to switch the handover method to be used to the second handover method in response to a change in the state of the terminal apparatus. Can notify the terminal device to that effect. Similarly, when the terminal device uses the second handover method, if the handover method to be used is switched to the first handover method, the control device notifies the terminal device to that effect. Also good. Further, when the first handover method is normally used, the control device continues to periodically transmit a predetermined signal during a period when the terminal device determines that the second handover method should be used. Also good. In this case, the terminal device using the second handover method can switch the handover method used by itself to the first handover method in response to the reception of the predetermined signal. In addition, when the second handover method is used, the control device can notify the terminal device of timing information for executing the handover process. Note that different timing information may be notified to a plurality of terminal devices.

  As described above, the control device can dynamically change the handover method to be used by the terminal device based on the state and characteristics of the terminal device. Thereby, for example, in a state where the probability that the handover process based on the measurement of the radio wave state of the terminal device or the entire system is likely to fail is high, by executing the handover process not depending on the measurement result of the radio state, The failure probability can be reduced. In addition, for example, when the probability that the handover process based on the measurement of the radio wave condition fails is low, the wireless terminal executes the handover process based on the measurement of the radio wave condition, thereby performing a highly accurate handover according to the actual radio wave environment. Processing can be executed. As described above, according to the present invention, the radio terminal can flexibly switch the handover method and execute the handover by an appropriate method.

Claims (14)

A control device that controls handover of a terminal device that performs wireless communication,
Determining means for determining characteristics of the terminal device,
Depending on the result of the determination, the terminal device can be selected from a first handover method started in response to measurement of a radio wave state by the terminal device and a second handover method started without using the measurement. Selecting a handover method to be executed by the terminal device,
Have
The characteristics of the terminal device include frequencies that the terminal device can handle,
The selection means selects the second handover method when the number of frequencies that can be supported by the terminal device is smaller than the number of frequencies that can be supported by another terminal device.
Control device comprising a call.   The determination means further determines the state of the terminal device.
  The control device according to claim 1. The state of the terminal device includes a moving speed of the terminal device,
The selection means selects the second handover method when the moving speed exceeds a predetermined value;
The control device according to claim 2 . The determination unit determines the moving speed according to a time interval at which the terminal apparatus executes a handover.
The control device according to claim 3 . The state of the terminal device includes the current date and time,
The selection means selects the second handover method when the date and time is a predetermined date and time or included in a predetermined period;
Control device according to claim 2 in any one of 4, characterized in that. The state of the terminal device includes a geographical position of the terminal device,
The selection means selects the second handover method when the position is included in a predetermined range;
Control device according to any one of claims 2 5, characterized in that. The state of the terminal device includes the total number of the terminal device and other terminal devices existing in a predetermined range including the geographical position of the terminal device,
The selection means selects the second handover method when the total number has reached a predetermined level;
Control device according to any one of claims 2 to 6, characterized in that. The state of the terminal device includes moving means of the terminal device,
The selecting means selects the second handover method when the terminal apparatus is moving by a predetermined moving means;
The control device according to claim 2 , wherein the control device is a control device. The selecting means selects the first handover method when not selecting the second handover method;
The control device according to claim 1 , wherein the control device is a control device. The selection means, when the second handover method is selected, notifies the terminal device of the timing for executing the handover;
The terminal device performs handover at the notified timing,
The control device according to any one of claims 1 to 9, wherein The selection unit determines the timing so that at least two terminal devices out of the plurality of terminal devices execute handover at different timings when the plurality of terminal devices execute the second handover method. To
The control device according to claim 10. The control device is included in a base station device connected before the terminal device executes a handover or a node in a network to which the base station device is connected,
The control device according to claim 1, wherein the control device is a control device. A control method executed by a control device that controls handover of a terminal device that performs wireless communication,
And determining the characteristics of the previous SL terminal device,
Depending on the results of the previous SL judgment, from among the second handover method that is initiated regardless of the measured first handover method is started in response to the measurement of the radio wave condition by the terminal device, the terminal Selecting a handover method to be executed by the apparatus and causing the terminal apparatus to execute the method;
Have
The characteristics of the terminal device include frequencies that the terminal device can handle,
In the selection, when the number of frequencies that can be supported by the terminal device is smaller than the number of frequencies that can be supported by another terminal device, the second handover method is selected.
Control wherein a call. In a computer provided in a control device that controls handover of a terminal device that performs wireless communication,
Determining the characteristics of the terminal device;
Depending on the result of the determination, the terminal device can be selected from a first handover method started in response to measurement of a radio wave state by the terminal device and a second handover method started without using the measurement. Selecting a handover method to be executed by the terminal device, and
A program for executing,
The characteristics of the terminal device include frequencies that the terminal device can handle,
In the selection, when the number of frequencies that can be supported by the terminal device is smaller than the number of frequencies that can be supported by another terminal device, the second handover method is selected.
A program characterized by that .

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