JP4726644B2 - Method for controlling handover of mobile terminal and mobile terminal system - Google Patents

Description

  The present invention relates to a handover control method for a mobile terminal such as a mobile phone, and a handover threshold calculation system for calculating a handover threshold.

  The use of mobile terminals such as mobile phones while traveling in automobiles has caused serious accidents. Because of this situation, the use of mobile terminals while driving is subject to legal restrictions. However, the actual situation is that the use of mobile terminals while driving is still not gone. Also, in public transportation such as trains and buses, the use of mobile terminals, in particular, self-containment of voice calls is required. Voice calls are often refrained due to improved manners, but no situation has been reached in which there is no voice call.

Therefore, it is desirable to impose restrictions on the call while driving a car or using public transportation. For example, as a limitation, control for disconnecting a call without allowing a handover can be considered. On the other hand, when walking or the like, it is necessary to allow handover without imposing restrictions on the call. For example, when a user is crossing a pedestrian crossing and crossing a pedestrian crossing to make a call after a mobile phone has been crossed, The ringing should not be interrupted. As described above, in good faith use while walking, control is required so that handover is performed appropriately and handover is not performed while driving a car or using public transportation.
JP 2005-236487 A JP 2000-197093 A

  In Patent Document 1, a mobile terminal (wireless communication apparatus) has a moving speed measuring unit that measures the moving speed, and determines whether or not to perform handover control based on the measured moving speed. It is disclosed that a determination method and a threshold for setting the threshold are set. Patent Document 1 proposes the use of an accelerometer or GPS mounted on a wireless communication device as a moving speed measuring means. In this way, it is possible to limit handover during high-speed movement by controlling the handover by measuring the moving speed of the mobile body itself.

  Patent Document 2 proposes that the mobile terminal obtains information indicating the moving speed of the mobile terminal from the temporal variation of the reception level from the base station and changes the handover threshold. Has been.

  In Patent Documents 1 and 2, since the mobile terminal itself measures the moving speed of the mobile terminal, it is necessary to add a special means for speed measurement to the mobile terminal. In particular, the installation of an accelerometer and GPS has the problems that the configuration of the mobile terminal is complicated, and the weight and cost are increased. Also, the radio output of the base station is adjusted at different levels in each region, the shielding characteristics differ due to the difference in the density of buildings, and the user does not always move in the radial direction from the base station. For this reason, it is not easy to estimate the moving speed itself from fluctuations in the reception level. Therefore, in practice, there is a problem that handover may not be performed despite the moving speed during walking.

  An object of the present invention is to provide a handover control method and a handover threshold calculation system capable of appropriately determining a handover threshold for determining whether or not handover is possible for each mobile terminal.

An object of the present invention is to have a plurality of exchanges each connected to a plurality of base stations, the exchanges are connected via a signal network, and mobile terminals are mutually connected via the base station and the exchange. In a mobile terminal system capable of communication, a handover control method for controlling handover of the mobile terminal,
Repeat the wireless level measurement request from the base station to the mobile terminal and transmission of the measured radio level from the mobile terminal to the base station a plurality of times between the mobile terminal and the base station. Steps,
In the base station, transmitting the radio level to the exchange,
In the switching center, the level fluctuation value representing the fluctuation of the radio level based on the radio level is calculated, and the level fluctuation value is connected to the threshold value calculation system connected via the signal network or another network. A step of sending
In the threshold value calculation system, the level fluctuation value is stored in a storage device in association with information for specifying the mobile terminal,
In the threshold value calculation system, the level fluctuation value stored in the storage device and associated with the information for identifying the mobile terminal is read, and based on the level fluctuation value and the frequency of appearance for each level fluctuation value Determining a level variation value corresponding to a handover threshold specific to the mobile terminal;
Storing the handover threshold in the storage device in association with information identifying the mobile terminal,
Further, a step of repeatedly performing a radio level measurement request from the base station to the mobile terminal and transmission of the measured radio level from the mobile terminal to the base station between the mobile terminal and the base station. When,
In the base station, transmitting the radio level to the exchange,
In the switching center, a level fluctuation value representing a fluctuation in radio level based on the radio level is calculated, and a handover threshold specific to the mobile terminal is compared with the calculated level fluctuation value, And determining whether or not handover is possible. The method is achieved by a handover control method.

In a preferred embodiment, in the step of determining a handover threshold specific to the mobile terminal,
The graph of the frequency of appearance for each level fluctuation value decreases with a certain slope on the smaller side of the level fluctuation value, and increases with a certain slope on the larger side than the certain range. When indicating such a form, the method includes the step of determining any level fluctuation value within a certain range of the level fluctuation value as the handover threshold. In this embodiment, the handover threshold is the level fluctuation value included in the “valley” portion of the graph indicating the frequency of occurrence of the level fluctuation value. This is a level change that occurs frequently due to the use of the mobile terminal owner, and does not determine the branch point of whether or not handover is possible, but it is a level change that rarely occurs even if the owner uses it. This is because it is estimated that it is more appropriate to decide.

  In a more preferred embodiment, in the step of determining a handover threshold specific to the mobile terminal, when a predetermined reference value of the level fluctuation value is included in the certain range, Determining a level fluctuation value indicating a minimum value of the frequency as the handover threshold value.

In another preferred embodiment, in the step of determining a handover threshold specific to the mobile terminal,
Identifying a peak value of the P-th frequency using a predetermined value P and a (P + 1) -th peak value in the graph showing the frequency of occurrence for each level fluctuation value;
Determining a level fluctuation value whose frequency shows a minimum value in a range between the level fluctuation values indicating the specified peak value as the handover threshold value.

In another preferred embodiment, in the step of determining whether the handover is possible,
The handover threshold is compared with the calculated level fluctuation value only when the plurality of level fluctuation values deteriorate with time.

Also, an object of the present invention is to have a plurality of exchanges each connected to a plurality of base stations, the exchanges are connected via a signal network, and the mobile terminal is connected via the base station and the exchange. In a mobile terminal system capable of mutual communication, a threshold connected to the switching center via the signaling network or another network for calculating a handover threshold for determining whether or not the mobile terminal can be handed over A calculation system,
A storage device that stores a level fluctuation value representing a fluctuation of a radio level based on a radio level measured a plurality of times in the mobile terminal in association with information that identifies the mobile terminal;
The level fluctuation value associated with the information for identifying the mobile terminal stored in the storage device is read, and the mobile terminal is read based on the level fluctuation value and the frequency of appearance for each level fluctuation value. It is achieved by a threshold value calculation system comprising a handover threshold value determining means for determining a level fluctuation value corresponding to a unique handover threshold value.

In a preferred embodiment, the handover threshold determining means includes
The graph of the frequency of appearance for each level fluctuation value decreases with a certain slope on the smaller side of the level fluctuation value, and increases with a certain slope on the larger side than the certain range. When a form such as this is shown, any level fluctuation value in a certain range of the level fluctuation values is determined as the handover threshold.

In a more preferred embodiment, the handover threshold calculation means includes
When a predetermined reference value of the level variation value is included in the certain range, the level variation value indicating the minimum value in the certain range is determined as the handover threshold. .

In another preferred embodiment, the handover threshold calculation means includes
In the graph showing the frequency of appearance for each level fluctuation value, the peak value of the Pth frequency using the predetermined value P and the (P + 1) th peak value are specified, and the specified peak In the range between the level fluctuation values indicating values, a level fluctuation value whose frequency shows a minimum value is determined as the handover threshold value.

  According to the present invention, it is possible to provide a handover control method and a handover threshold calculation system capable of appropriately determining a handover threshold for determining whether or not handover is possible for each mobile terminal. .

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an outline of a mobile phone system to which a handover control method according to the present embodiment is applied. As shown in FIG. 1, this embodiment corresponds to a system configuration of a so-called second generation mobile phone. However, the present invention is not limited to the second-generation mobile phone system, and is also applicable to mobile communication systems such as 3G (third-generation) mobile phone systems or mobile phones using mobile IP. Can be applied.

  As shown in FIG. 1, in this system, a signaling network 12 includes a subscriber home location register (referred to as “HLR”) 14, a gateway mobile telecommunications switching center (referred to as “GMSC”) 16, and mobile within a range. Communication switching centers (referred to as “VMSC”) 18 and 20 are connected. Further, one or more base stations (see reference numerals 22, 24, 26, and 28) are connected to the VMSCs 18 and 20, respectively. In FIG. 1, two VMSCs are illustrated, but it goes without saying that the number of VMSCs is not limited to the illustrated example. The number of BSs connected to each VMSC is also the same.

  In such a mobile phone system, a mobile terminal or mobile station (referred to as “MS”) 30 is connected to the signal network 12 via any BS or VMSC, and communicates with other MSs (not shown). Can communicate with each other. In the example of FIG. 1, the MS 30 is arranged via the BS 24.

  In the present embodiment, the VMSCs 18 and 20 are connected to the level threshold value calculation system 40 via the non-signal data network 42. The HLR 14 is also connected to the level threshold calculation system 40 via the non-signal data network 42. Since each of the VMSCs 18 and 20 or between the HLR 14 and the level threshold value calculation system 40 does not require real-time high-speed data communication and does not increase the load on the signal network 12, a high-speed signal network 12, a relatively slow non-signal data network 42 is used. However, data communication between the VMSCs 18 and 20 and the level threshold value calculation system 40 or between the HLR 14 and the level threshold value calculation system 40 may be realized using the signal network 12. The GMSC 16 is also connected to another network 32. Therefore, the MS 30 can communicate with a terminal connected to another network via the GMSC 16.

  In the present embodiment, the storage device of the HLR 14 stores predetermined information for each subscriber number, as will be described later. Information stored in the HLR 14 is transmitted to the VMSCs 18 and 20 as necessary. Further, as described later, the level threshold value calculation system 40 calculates a handover threshold value for determining whether or not handover is possible for each MS, that is, for each subscriber number. The handover threshold value calculated by the level threshold value calculation system 40 is transmitted to the HLR 14 and stored in the storage device.

  FIG. 2 is a diagram for explaining a conventional handover in a mobile phone system. Here, consider a case where the MS 30 moves from being controlled by a certain BS (for example, BS 24 in FIG. 1) to being controlled by another BS (for example, BS 22). Therefore, hereinafter, for example, the BS is represented as “BS24” and the VMSC is represented as “VMSC18”. Further, the other BS is represented as “BS22” or “other BS22”.

  While the MS 30 is communicating with the VMSC 18 via the BS 24 (step 201), the MS 30 transmits a radio status report to the VMSC 18 via the BS 24 at an appropriate timing (step 202). The VMSC 18 requests the MS 30 to measure the radio level via the BS 24 that is currently in communication (step 203). After measuring the radio level, the MS 30 uses the measured radio level as a level measurement response. , Return to VMSC 18 (step 204).

  If the VMSC 18 refers to the level measurement response and determines that a handover is necessary, the VMSC 18 transmits SB1 to the MS 30 via the other BS 22 that should intervene in communication with the MS 30 after the movement (step 205). At the same time, the switching channel designation is transmitted to the MS 30 via the original BS 24 (step 206). When the SB 2 is transmitted from the MS 30 to the VMSC 18 via the other BS 22, communication between the VMSC 18 and the MS 30 is established via the other BS 22.

  In the present embodiment, as described below, for each MS, a handover threshold value that is a criterion for whether or not handover is possible is calculated based on the actual usage mode of the MS, and the above-described threshold value is calculated based on the threshold value. Decide whether to perform a handover or to disconnect the communication between the VMSC and the MS. Therefore, the MS calculates a threshold value (under test), a mode in which the threshold value is determined and whether or not handover is possible is determined based on the threshold value, and as shown in FIG. As in the past, communication is performed in any one of three modes: a mode in which handover is always permitted (always possible). Therefore, the storage device of the HLR 14 stores information indicating in which mode communication is performed for each MS, that is, for each subscriber number. FIG. 3A is a diagram illustrating an example of a data list stored in the storage device of the HLR 14. As shown in FIG. 3A, the data list record has items such as a subscriber number, authentication information, a general call area number, a handover flag, and a handover threshold. As shown in FIG. 3B, the handover flag may be “0” in the “under test” mode for threshold calculation, “1” in the “restricted” mode, or “always available”. Takes the value “2”. As shown in FIG. 3A, in the present embodiment, a value indicating the mode of operation at the time of handover is stored for each subscriber number.

  Further, as shown in FIG. 3C, in the present embodiment, the handover threshold 302 is either a handover threshold for each subscriber number or a VMSC standard value for each subscriber number. Stored.

  Next, processing and data communication executed in the system when the MS is in the “under test” mode in the present embodiment will be described with reference to FIG. When the MS is in the “testing” mode, the value “0” is stored in the handover flag in the record relating to the subscriber number of the MS in the data list stored in the storage device of the HLR 14.

  Also in FIG. 4, it is considered that the MS 30 is communicating with the VMSC 18 via the BS 24. Although not shown, at the time of outgoing or incoming call of the MS 30, the VMSC 18 acquires the handover flag and the like from the record including the subscriber number of the MS 30 from the HLR 14. Since the value of the handover flag is “0”, the VMSC 18 determines that the MS 30 is in the “under test” mode. As will be described later, when the MS is in the “under test” mode, the handover may be limited using the VMSC standard value, or as in the “always possible” mode. , Always-on handover may be allowed.

  4, steps 401 and 402 are the same as steps 201 and 202 in FIG. When receiving the radio status report, the VMSC 18 executes a measurement request process (step 403). In the measurement request process, the VMSC 18 first reads the number N of times of level measurement in the MS stored in advance in the storage device (not shown) (step 404). The level measurement count N may be stored in the storage device of the VMSC 18, but is not limited thereto. For example, the level measurement count N may be stored in the storage device of the level threshold calculation system 40, and the VMSC 18 may make an inquiry to the level threshold calculation system 40 in response to the start of the measurement request process.

  The VMSC 18 transmits a level deterioration measurement request to the BS 24 (step 405). As a result, the level measurement count N is transmitted to the BS 24 (step 406). In response to receiving the level measurement count N, the BS 24 executes level deterioration measurement processing (step 407). In the level deterioration measurement process, transmission of a level measurement request from the BS 24 to the MS 30 and transmission of a level measurement response from the MS 30 to the BS 24 are repeated N times.

  FIG. 5 is a flowchart showing in more detail the level deterioration measurement process executed in the BS according to the present embodiment. As shown in FIG. 5, the BS 24 reads the measurement interval T of level measurement for the MS 30 stored in advance in the storage device (not shown) (step 501). Alternatively, the level degradation measurement request from the VMSC 18 may include the level measurement interval T as well as the number of measurements N.

  Next, the BS 24 transmits a level measurement request to the MS 30 (step 502) and receives a level measurement response from the MS 30 (step 503). Next, the radio level of the MS 30 included in the level measurement response is stored in the storage device of the BS 24 (step 504). If N measurements have not been completed (No in step 505), the process waits for the level measurement interval T (step 506) and returns to step 502. If it is determined YES in step 505, the BS 24 transmits the level measurement interval T and the N radio levels of the MS 30 stored in the storage device to the VMSC 18 as a level deterioration measurement response (step 505). 507, step 409 of FIG. 4). FIG. 6A is a diagram illustrating an example of N wireless levels stored in the storage device.

  When the VMSC 18 receives the level deterioration measurement response, the VMSC 18 calculates a normalized level fluctuation value (step 410). FIG. 7 is a flowchart showing in more detail the normalization level fluctuation value calculation process executed by the VMSC 18.

  As shown in FIG. 7, when the VMSC 18 receives the level degradation measurement response (step 701), among the received normalized level fluctuation values, the VMSC 18 measures the radio level measured at the first time and the Nth time. A difference from the radio level is calculated, and this is set as level fluctuation (step 702). Next, the VMSC 18 calculates a normalized level fluctuation value corresponding to the level fluctuation for one second based on the level fluctuation calculated in step 702, the measurement interval T during the level degradation measurement response, and the number of times of measurement N (step). 703). This can be achieved by dividing the level variation by the time interval (T × (N−1)). The VMSC 18 stores the record of the recording result file including the subscriber number of the MS 30 and the normalization level fluctuation value in the storage device of the VMSC 18 (step 704). FIG. 6B is a diagram illustrating an example of a record of the recording result file.

  In the present embodiment, the VMSC 18 is capable of storing a predetermined number (a fixed number) of records in the recording result file in the storage device. Therefore, if the storage amount is less than a certain number (No in step 705), the process waits until the next level degradation measurement response is received from the MS 30 or another MS (step 706). On the other hand, if the storage amount exceeds a certain number (Yes in step 705), the VMSC 18 creates a level measurement basic information report including a recording result file in which the certain number of records are stored. Then, this is transmitted to the level threshold value calculation system 40 (step 707, step 411 in FIG. 4). Next, the VMSC 18 deletes the record of the recording result file (step 708).

  When receiving the level measurement basic information report, the level threshold value calculation system 40 refers to the subscriber number of each record, and stores the received normalized level fluctuation value in the storage device in association with the subscriber number ( Step 412). FIG. 6C is a diagram showing an example of the normalized level fluctuation value stored and stored in association with a certain subscriber number. As shown in FIG. 6C, in the level threshold value calculation system 40, the normalized level fluctuation value stored in the VMSC and transmitted to the level threshold value calculation system 40 is accumulated for each subscriber number. In the VMSC, the frequency (number of times) of each normalized level fluctuation value may be stored for each subscriber number.

  When the normalized level fluctuation value is sufficiently accumulated, the level threshold value calculation system 40 executes the handover threshold value determination process for the subscriber number for which the normalized level fluctuation value is sufficiently accumulated. FIG. 8 is a flowchart showing in detail the handover threshold value determining process.

  As shown in FIG. 8, the level threshold value calculation system 40 acquires the normalized level fluctuation value accumulated in association with a certain subscriber number from the storage device (step 801). Next, the level threshold value calculation system 40 aggregates the frequency (number of times) for each normalized level variation value, and creates a graph in which the frequency is a function of the normalized level variation value (step 802).

  Next, the level threshold value calculation system 40 specifies the position in the graph of the normalized level fluctuation value corresponding to the predetermined speed (step 803). In the present embodiment, the “restriction” mode is a case in which, in this embodiment, the user restricts handover while driving a car or a bicycle or getting on a train, but the user is simply walking. The purpose is to allow handover. Therefore, the level threshold value calculation system 40 is statistically based on a reference speed (for example, 10 km / h) that is statistically considered as a boundary between the walking speed of the user and the traveling speed of the bicycle based on the accumulation of the normalized level fluctuation value. The normalization level fluctuation value considered to correspond is determined. Then, in the graph, the frequency indicated by the normalized level fluctuation value and the shape of the surrounding graph are referred to.

  The level threshold value calculation system 40 determines whether or not the position on the graph corresponds to “valley” (step 804). Here, in this embodiment, “valley” means that the change in the frequency (number of times) is constant in a range of a normalization level fluctuation value including a normalization level fluctuation value indicating a position on the graph. On the side that is within the range and smaller than the lower limit of the normalization level fluctuation value range, the frequency (number of times) decreases with a certain slope or more, and the normalization level fluctuation value On the side larger than the upper limit of the range, it means a portion where the frequency (number of times) increases at a certain slope or more. In other words, the valley is a small value within a certain range when it is reduced over a certain slope in the graph and then fluctuates small within a certain range within a certain normalized level fluctuation value and then increases over a certain slope. Corresponds to the fluctuating part. In the range of the constant normalization level fluctuation value, when there is a normalization level fluctuation value that is a frequency (number of times) exceeding the frequency (number of times) that is a small value of the upper limit or the lower limit, It is not equivalent to “valley”.

  If it is determined yes in step 804, the level threshold value calculation system 40 determines the normalized level fluctuation value that minimizes the frequency (number of times) in the above-mentioned “valley” as the subscriber number-specific value. Is stored in the corresponding record in the data list (step 805).

  On the other hand, when it is determined NO in step 804, the level threshold value calculation system 40 causes the frequency (number of times) to be minimized in the next “valley” on the side with the larger normalized level fluctuation value. A normalization level fluctuation value is specified (step 806). The level threshold value calculation system 40 stores the specified normalized level fluctuation value as a subscriber-specific handover threshold value in a corresponding record in the data list (step 807).

  FIG. 9A and FIG. 9B are diagrams for explaining an example of the handover threshold. In step 803 of FIG. 8, if the normalized level fluctuation value corresponding to the predetermined speed and the position on the graph are those indicated by the arrows in FIG. 9A, the position on the graph is “valley”. Equivalent to. Accordingly, the normalized level fluctuation value that minimizes the frequency (number of times) in this “valley” is the handover threshold (step 805 in FIG. 8). On the other hand, when the normalized level fluctuation value corresponding to the predetermined speed and the position on the graph are as shown in FIG. 9B, in the next “valley” on the side where the normalized level fluctuation value is large. The normalization level fluctuation value that minimizes the frequency (number of times) becomes the handover threshold (step 806 in FIG. 8).

  The handover threshold calculated in this way by the level threshold calculation system 40 is transmitted to the HLR 14 via the non-signal data network 42 together with the subscriber number. When the HLR 14 receives the normalization level fluctuation value serving as the handover threshold, the HLR 14 stores the received handover threshold in the handover threshold item in the record specified by the subscriber number in the data list. Thereafter, if handover should be restricted for the MS having the subscriber number, the value of the handover flag is set to “1”.

  Next, processing and data communication executed in the system when the MS is in the “restricted” mode in the present embodiment will be described with reference to FIG. When the MS is in the “restricted” mode, the handover flag “1” and the handover threshold are stored in the record relating to the subscriber number of the MS in the data list stored in the storage device of the HLR 14.

  Also in the example of FIG. 10, it is considered that the MS 30 is communicating with the VMSC 18 via the BS 24. When the MS 30 originates or receives an incoming call, the VMSC 18 acquires the handover flag and the handover threshold from the HLR 14 from the record including the subscriber number of the MS 30. Since the value of the handover flag is “1”, the VMSC 18 determines that the MS 30 is in the “restricted” mode, and determines that the handover is controlled based on the acquired handover threshold.

  10, steps 1001 and 1002 correspond to steps 401 and 402 in FIG. Also, steps 1003 to 1009 are the same as steps 403 to 409 in FIG.

  When receiving the level degradation measurement response from the BS 24, the VMSC 18 calculates the level degradation ratio (step 1010) and compares it with the handover threshold (step 1011). In the course of this process, it is determined whether to perform a handover or to disconnect a call without performing a handover.

  FIG. 11 is a flowchart showing the level deterioration ratio process in detail. As shown in FIG. 11, the VMSC 18 initializes the processing parameter L to “1” (step 1101), and is measured at the Lth time out of the mobile station radio levels included in the received level degradation measurement response. The wireless level is compared with the wireless level measured at the (L + 1) th time (step 1102). If the L-th radio level is equal to or lower than the (L + 1) -th radio level (No in step 1103), it is determined that the deterioration ratio is out of the range and the handover should be performed. In other words, over time, the radio level does not deteriorate, but if it improves, the level deterioration ratio cannot be calculated, and there is a possibility that it is not movement by the vehicle. Admit.

  If it is determined yes in step 1103, the parameter is increased and step 1102 is executed until L is equal to the number of measurements N. If the wireless level has gradually deteriorated from the first wireless level to the Lth wireless level, it is finally determined No in step 1105 and the comparison with the threshold value is performed. move on.

  FIG. 12 is a flowchart showing in detail the comparison processing with the threshold. As shown in FIG. 12, the VMSC 18 calculates a normalized level fluctuation value (steps 1201 and 1202). This corresponds to steps 702 and 703 in FIG. As described above, the VMSC 18 refers to the handover threshold acquired from the HLR 14 when the MS originates or terminates (step 1203), and compares the handover threshold with the calculated normalized level fluctuation value.

  If the normalized level fluctuation value is equal to or less than the handover threshold value (No in step 1204), it is determined that the handover should be performed because the normalized level fluctuation value is within the threshold value. Therefore, after that, the handover process is executed as in the conventional case (see step 205 and subsequent steps in FIG. 2). On the other hand, if the normalized level fluctuation value exceeds the handover threshold (Yes in Step 1204), it is determined that the call should be disconnected. Therefore, the VMSC 18 executes a call disconnection process (not shown) with the MS 30.

  According to the present embodiment, for each subscriber (each subscriber number), the normalization level fluctuation value estimated that the subscriber is moving at the reference speed is used as the handover threshold value indicating whether or not handover is possible. If the normalization level fluctuation value from the MS of the subscriber number is within the handover threshold, the handover is performed, and if it exceeds the range, the call is disconnected. As a result, it is possible to set an appropriate handover threshold according to the usage mode and usage location of the subscriber's MS, and to determine whether or not an appropriate handover is possible.

  By determining whether or not handover is possible using the normalized level fluctuation value at which the movement at the reference speed is estimated for each subscriber as the handover threshold, the following effects can be obtained.

  During a movement at a reference speed or higher, for example, while a car is running, the call is automatically disconnected. Therefore, since the driver is forced to stop the car and talk on the phone, a reduction in traffic accidents is expected. In addition, since the call is automatically disconnected while the train is running, it is expected that the manners in the vehicle will be improved. On the other hand, during a call during walking, a handover is performed, so that it can be used as usual.

  The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, in the above-described embodiment, in the graph of the normalized level variation value and the number of times (frequency), a portion corresponding to “valley” is found, and the normalized level variation value at the position corresponding to “valley” is Although it is determined as the handover threshold specific to the subscriber number, the calculation of the handover threshold is not limited to this. FIG. 13 is a flowchart showing a handover threshold determination process according to another embodiment of the present invention. In FIG. 13, steps 1301 and 1302 are the same as steps 801 and 802 of FIG. 8, respectively, and description thereof is omitted.

  The level threshold value calculation system 40 uses the predetermined value P in the graph of the normalized level fluctuation value and the number of times (frequency) to calculate the Pth peak value and the (P + 1) th peak value. The position to be indicated is specified (step 1303). For example, as “P = 1”, the first peak value and the second peak value are specified. Next, the level threshold value calculation system 40 specifies a normalized level fluctuation value at a position that becomes the minimum value between the two specified peak values (step 1304). Thereafter, the level threshold value calculation system 40 stores the normalized level fluctuation value of the position that is the minimum value in the corresponding record in the data list as the handover threshold value unique to the subscriber number (step 1305).

  In the embodiment, the normalization level fluctuation value of the MS is stored in the mode in which the handover flag is “0: under test”. In this state, the handover may be limited by the default value (VMSC standard value) of the handover threshold, or the handover may be performed without limitation as in the mode in which the handover flag is “2: always available”. May be accepted. For example, in the “under test” mode, when the handover is controlled based on the VMSC standard value, in the measurement request process (step 403 in FIG. 4), the normalization level fluctuation value is calculated (step 410). Then, calculation of the level deterioration ratio (step 1010 in FIG. 10) and comparison with the threshold value (step 1011) are executed. Here, the handover threshold used in step 1011 is a VMSC standard value.

  Further, in a state where the handover threshold specific to the subscriber number of the MS (subscriber individual value) is calculated, the handover flag is basically set to “1: restriction”, and the hand unique to the subscriber number is set. Whether or not handover is possible is determined according to the over threshold. In the present embodiment, the handover flag can be set to “2: always possible” under a certain condition or setting. The certain condition or setting corresponds to an application for always allowing handover and paying a necessary fee. Or it is good also as a structure which enables a hand-over at any time temporarily (in a predetermined period) by a subscriber's application. In this case, the handover flag in the corresponding record of the HLR 14 is updated to “2” at the start of the determined period, and the handover flag in the record is updated to “1” at the end of the period. It should be done.

  In the above embodiment, the normalized level fluctuation value that minimizes the frequency (number of times) in the “valley” is determined as the subscriber-specific handover threshold (see step 805 in FIG. 8). However, the present invention is not limited to this, and when the position on the graph corresponds to “valley”, the normalized level fluctuation value corresponding to the position on the graph may be determined as the handover threshold.

FIG. 1 is a block diagram showing an outline of a mobile phone system to which a handover control method according to the present embodiment is applied. FIG. 2 is a diagram for explaining a conventional handover in a mobile phone system. FIG. 3A is a diagram showing an example of a data list stored in the storage device of the HLR according to the present embodiment, FIG. 3B is a diagram for explaining a handover flag, and FIG. It is a figure explaining a hand-over threshold value. FIG. 4 is a diagram showing processing and data communication executed in the system when the MS is in the “under test” mode in the present embodiment. FIG. 5 is a flowchart showing in more detail the level deterioration measurement process executed in the BS according to the present embodiment. FIG. 6A is a diagram showing an example of N radio levels stored in the BS storage device, and FIG. 6B is a diagram showing an example of a recording result file stored in the VMSC storage device. FIG. 6C is a diagram showing an example of a normalization level fluctuation value related to a certain subscriber number. FIG. 7 is a flowchart showing in more detail the calculation process of the normalized level fluctuation value executed by the VMSC according to the present embodiment. FIG. 8 is a flowchart showing in detail the handover threshold value determining process according to the present embodiment. FIG. 9A and FIG. 9B are diagrams for explaining an example of the handover threshold. FIG. 10 is a diagram showing processing and data communication executed in the system when the MS is in the “restricted” mode in the present embodiment. FIG. 11 is a flowchart showing in detail the level deterioration ratio process according to the present embodiment. FIG. 12 is a flowchart showing in detail the comparison processing with the threshold according to the present embodiment. FIG. 13 is a flowchart illustrating handover threshold determination processing according to another embodiment.

Explanation of symbols

12 Signaling network 14 HLR
16 GMSC
18, 20 VMSC
22, 24, 26, 28 BS
30 MS
40 level threshold calculation system 42 non-signal data network

Claims (9)

Mobile terminals each having a plurality of switching stations to which a plurality of base stations are connected, the switching stations being connected by a signal network, and mobile terminals capable of communicating with each other via the base station and the switching station In the system, a handover control method for controlling handover of the mobile terminal, comprising:
Repeat the wireless level measurement request from the base station to the mobile terminal and transmission of the measured radio level from the mobile terminal to the base station a plurality of times between the mobile terminal and the base station. Steps,
In the base station, transmitting the radio level to the exchange,
The switching center calculates a level fluctuation value representing the fluctuation of the radio level based on the radio level, and the level fluctuation value is connected to the threshold value calculation system connected via the signal network or another network. A step of sending
In the threshold value calculation system, the level fluctuation value is stored in a storage device in association with information for specifying the mobile terminal,
In the threshold value calculation system, the level fluctuation value stored in the storage device and associated with the information for identifying the mobile terminal is read, and based on the level fluctuation value and the frequency of appearance for each level fluctuation value Determining a level variation value corresponding to a handover threshold specific to the mobile terminal;
Storing the handover threshold in the storage device in association with information identifying the mobile terminal,
Further, a step of repeatedly performing a radio level measurement request from the base station to the mobile terminal and transmission of the measured radio level from the mobile terminal to the base station between the mobile terminal and the base station. When,
In the base station, transmitting the radio level to the exchange,
In the switching center, a level fluctuation value representing a fluctuation in radio level based on the radio level is calculated, and a handover threshold specific to the mobile terminal is compared with the calculated level fluctuation value, Determining whether or not the handover is possible,
In the step of determining whether or not handover is possible, if the calculated normalized level fluctuation value is within the handover threshold value, a handover is performed, and the calculated level fluctuation value exceeds the handover threshold value. A handover control method configured to disconnect a call to the mobile terminal when the mobile terminal is present ; Determining a handover threshold specific to the mobile terminal;
The graph of the frequency of appearance for each level fluctuation value decreases with a certain slope on the smaller side of the level fluctuation value, and increases with a certain slope on the larger side than the certain range. 2. The hand according to claim 1, further comprising: determining, as the handover threshold value, any level fluctuation value in a certain range of the level fluctuation values when indicating a form in which the level fluctuation is performed. Over control method. Determining a handover threshold specific to the mobile terminal;
When a predetermined reference value of the level fluctuation value is included in the certain range, the step includes determining a level fluctuation value having a minimum frequency in the certain range as the handover threshold value. The handover control method according to claim 2. Determining a handover threshold specific to the mobile terminal;
Identifying a peak value of the P-th frequency using a predetermined value P and a (P + 1) -th peak value in the graph showing the frequency of occurrence for each level fluctuation value;
2. The method according to claim 1, further comprising: determining, as the handover threshold, a level fluctuation value whose frequency indicates a minimum value in a range between the level fluctuation values indicating the specified peak value. The handover control method described. In the step of determining whether or not handover is possible,
The configuration is such that the handover threshold value is compared with the calculated level fluctuation value only when the plurality of level fluctuation values deteriorate with time. 5. The handover control method according to 4. Mobile terminals each having a plurality of switching stations to which a plurality of base stations are connected, the switching stations being connected by a signal network, and mobile terminals capable of communicating with each other via the base station and the switching station In the system,
A threshold calculation system connected to the switching center via the signaling network or another network for calculating a handover threshold for determining whether or not the mobile terminal can be handed over ;
The threshold calculation system includes:
A storage device that stores a level fluctuation value representing a fluctuation of a radio level based on a radio level measured a plurality of times in the mobile terminal in association with information that identifies the mobile terminal;
The level fluctuation value associated with the information for identifying the mobile terminal stored in the storage device is read, and the mobile terminal is read based on the level fluctuation value and the frequency of appearance for each level fluctuation value. A handover threshold value determining means for determining a level fluctuation value corresponding to a unique handover threshold value,
The switching center calculates a level fluctuation value representing a fluctuation of a radio level based on a radio level measured a plurality of times at the mobile-to-terminal, and receives a handover unique to the mobile terminal received from the threshold value calculation system. Handover availability determination means for determining whether handover is possible by comparing a threshold value with the calculated level fluctuation value,
If the calculated normalization level fluctuation value is within the handover threshold value, the handover feasibility determining means performs a handover, and the calculated level fluctuation value exceeds the handover threshold value. Is a mobile terminal system configured to disconnect a call to and from the mobile terminal . The handover threshold determination means of the threshold calculation system comprises:
The graph of the frequency of appearance for each level fluctuation value decreases with a certain slope on the smaller side of the level fluctuation value, and increases with a certain slope on the larger side than the certain range. 7. The apparatus according to claim 6, wherein when the mode is indicated, any level fluctuation value in a certain range of the level fluctuation value is determined as the handover threshold. Mobile terminal system . The handover threshold calculation means of the threshold calculation system includes :
When a predetermined reference value of the level fluctuation value is included in the certain range, the level fluctuation value indicating the minimum value in the certain range is determined as the handover threshold. The mobile terminal system according to claim 7. The handover threshold calculation means of the threshold calculation system includes :
In the graph showing the frequency of appearance for each level fluctuation value, the peak value of the Pth frequency using the predetermined value P and the (P + 1) th peak value are specified, and the specified peak 7. The movement according to claim 6, wherein a level fluctuation value whose frequency shows a minimum value in a range between the level fluctuation values indicating values is determined as the handover threshold value. Body terminal system .

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