JP4305933B2 - Mobile communication terminal and base station apparatus - Google Patents

Description

  The present invention relates to a mobile communication terminal and a base station apparatus, and more particularly to handover control and standby control in a mobile communication system having a plurality of frequency channels.

  In recent years, mobile communication systems have become widespread, and next-generation mobile communication systems that enable high-speed multimedia communication have been developed. In order to accommodate a large number of users, it is common to construct a mobile communication system in which one communication carrier operates a plurality of frequency channels in the same region. As an example of a mobile communication system having a plurality of frequency channels, there is a W-CDMA (Wideband Code Division Multiple Access) system, and an OFCDM (Orthogonal Frequency and Code Division Multiplexing) system or the like is studied as a next generation communication system. ing. An example of a conventional mobile communication system is shown below.

The W-CDMA system has a communication system standardized by a standardization organization called 3GPP (3rd Generation Partnership Project), and has a configuration as shown in an example of FIG. FIG. 7 is a system configuration diagram showing an example of the configuration of the W-CDMA system.
As shown in FIG. 7, the W-CDMA system is a system that performs wireless communication between a plurality of base stations 71, 72, 73 and mobile communication terminals 74 arranged at a certain interval. Here, the mobile communication terminal 74 generally performs communication by selecting the optimum base station, for example, the base station 71, by measuring the quality of the received signal from each of the base stations 71, 72, 73. . While waiting, information from one base station with the strongest received radio wave, for example, base station 71, is received, but the quality of the received signal from base station 71 deteriorates due to movement of mobile communication terminal 74. If the quality of the received signal from the neighboring base station, for example, the base station 72 is improved, the 3GPP standard “cell selection and cell reselection in the idle mode as described in Non-Patent Document 1” Based on the determination criterion “Cell selection and reselection in idle mode”, the base station that receives the signal is changed to a base station 72 with higher quality.

  On the other hand, when the mobile communication terminal 74 is communicating, generally, continuous communication is realized by using a soft handover function (a function for performing communication simultaneously with a plurality of base stations), which is a feature of the W-CDMA system. is doing. That is, when the quality of the received signals from the communicating base station 71 and the neighboring base stations 72 and 73 changes due to movement of the mobile communication terminal 74, communication with a base station with higher quality is performed. Therefore, the mobile communication terminal 74 is a base station to newly communicate with, for example, the base station 72 based on the determination standard of “Intra-frequency measurements” of the 3GPP standard as described in Non-Patent Document 2. Is transmitted to the base station 71, the base station 71 determines a new base station 72 to communicate with, and notifies the mobile communication terminal 74 of it. As a result, communication is continued without interruption while performing processing for appropriately changing the base station to be communicated from the base station 71 to the base station 72.

  In addition, the mobile communication terminal 74 does not continue the communication by handing over to the base station 72 that communicates in the same frequency 2 GHz band as the base station 71 that is communicating as described above. When switching the communication by selecting a base station 73 having a frequency different from 2 GHz, for example, 800 MHz, the criterion of “Inter-frequency measurements” of 3GPP standard as described in Non-Patent Document 3 is used. Based on the hard handover function (a function for instantaneously switching all the communicating base stations to maintain communication), the communication is performed while the base station 71 is changed from the base station 71 to the base station 73. Communication is continued without interruption.

  However, in the 3GPP standard, when selecting an optimal base station during standby and during communication, the base station to be switched is generally selected based on the reception quality, and the moving speed of the mobile communication terminal 74 is Information on the cell radii of the base stations 71, 72, and 73 is not used. As a result, when the mobile communication terminal 74 moves at high speed during standby or during communication, there is a problem that the frequency of changing the standby base station or the base station with which communication is performed increases. During standby, while the process of changing the base station for receiving information is being performed, the mobile communication terminal 74 cannot receive a call, so the probability of an incoming call failure increases, and the information is received. When the base station to be changed is changed, the current consumption of the mobile communication terminal 74 also increases, and there is a problem that the standby time is shortened. Further, when the mobile communication terminal 74 moves at a high speed, there is a problem that the load on the network increases because the cell to be communicated, that is, the base station, is frequently changed during communication.

Among the problems described above, regarding handover control during communication, there is a technique disclosed in Japanese Patent Laid-Open No. 2002-27522 “Storage medium storing mobile communication terminal and cell selection control program” disclosed in Patent Document 1. . In the technology of Patent Document 1, the mobile communication terminal determines the size of the cell radius of each base station, and based on information such as the moving speed and transmission power of the mobile communication terminal and the required quality of information to be communicated, In this technique, it is determined whether a base station with a large cell radius or a base station with a small cell radius should be selected preferentially, and a base station having the determined cell radius is preferentially selected.
JP 2002-27522 A 3rd Generation Partnership Project; “User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode”, 3GPP TS25.304 V3.14.0, Section 5.2, (2004-03) 3rd Generation Partnership Project; “Radio Resource Control (RRC) protocol specification”, 3GPP TS25.331 V3.18.0, Section 14.1, (2004-03) 3rd Generation Partnership Project; “Radio Resource Control (RRC) protocol specification”, 3GPP TS 25.331 V3.18.0, Section 14.2, (2004-03)

  However, the technique described in Patent Document 1 does not describe a means for determining the cell radius of each base station or a specific means for preferentially selecting an optimal base station, and handover control. Are all performed on the mobile communication terminal side. However, the handover control requires not only the mobile communication terminal side but also the base station side control in practice. Furthermore, on the base station side, it is more efficient to perform handover control such that an optimum base station is selected by combining various conditions based on information received from the mobile communication terminal. Can be improved.

  Therefore, an object of the present invention is to perform handover control on the base station side in which the base station and the mobile communication terminal cooperate to select an optimal base station according to the moving speed of the mobile communication terminal. When the mobile communication terminal moves at high speed, the operation is changed to the optimal base station specified from the station and the communication is continued, and when the mobile communication terminal moves at high speed, the current consumption of the mobile communication terminal is reduced. It is possible to reduce the load on the mobile communication network. Another object of the present invention is to provide a base station during communication when information on the cell radius of each base station can be easily discriminated on the mobile communication terminal side by conditions set in advance in the mobile communication system. It is to enable a mobile communication terminal to perform a part of handover control to be performed and standby control during standby.

The present invention is constituted by the following technical means in order to solve the above-described problems.
The first technical means is a movement for selecting a base station device to be awaited from the plurality of base station devices based on a criterion obtained by applying a predetermined control parameter to reception quality between the plurality of base station devices. a communication terminal acquires the control parameter from the base station apparatus, according to the moving speed of the mobile communication terminal, by updating the reception quality by applying the control parameters, the determination of the said reference Features.

According to a second technical means, in the mobile communication terminal described in the first technical means, the control parameter is obtained from broadcast information from the base station apparatus.

A third technical means is a base station apparatus capable of communicating with the mobile communication terminal described in the first technical means, wherein the control parameter is transmitted to the mobile communication terminal.

A fourth technical means is the base station apparatus according to the third technical means, wherein the control parameter is transmitted to the mobile communication terminal by broadcast information.

  According to the present invention composed of the technical means as described above, handover that preferentially selects an optimal base station according to the moving speed of the mobile communication terminal and the size of the cell radius for each base station. By performing control and standby control, the probability of an incoming call failure can be reduced when the mobile communication terminal is in standby, and consumption is reduced by reducing the frequency of changing the base station that receives information. An increase in current can be prevented. In addition, even when the mobile communication terminal is in communication, it is possible to reduce the frequency of occurrence of handover for changing the base station to communicate, and to reduce the load on both the base station and the mobile communication terminal. Quality can be ensured and a stable mobile communication system can be provided without biasing communication with a specific base station. Furthermore, it is possible to preferentially perform handover control and standby control only for a specific mobile communication terminal among the mobile communication terminals by using unique information that can identify the mobile communication terminal. is there.

An example of an embodiment relating to a mobile communication terminal and a base station apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram showing an example of a cell configuration of a mobile communication system to which the present invention is applied. As shown in FIG. 1, in a mobile communication system, base stations 11, 12,..., 15 each having cells 11z, 12z,..., 15z having various cell radii are arranged in a state where the cells overlap each other. It is configured. Here, the cell radius is determined by various factors such as the transmission power of the base station and the frequency to be used. For example, the larger the base station transmission power, the larger the cell radius and the lower the frequency to be used. However, since the propagation loss is reduced, the cell radius is increased. In the example shown in FIG. 1, the cells 11z, 12z, 13z, and 14z are cells having a small cell radius, and the cell 15z is a cell having a large cell radius.

  The mobile communication terminal performs communication while moving in the overlapping cells as described above. For example, in FIG. 1, the mobile communication terminal includes the cells 11z, 15z, that is, the base station 11, It moves from the position 16 of the communication range of 15 toward the position 17 of the communication range of the cells 13z and 15z, that is, the base stations 13 and 15, via the communication ranges of the cells 14z and 15z, that is, the base stations 14 and 15.

  Each of the base stations 11, 12,..., 15 includes a plurality of reception quality offset values and a handover control unit that performs handover control between the base stations. Here, the reception quality offset value is a handover control parameter used for handover control or a standby control parameter used for standby control, and corresponds to the moving speed of the mobile communication terminal and the cell radius of each base station. This value is set in advance as a value to be used, and is applied to select the optimal base station according to the magnitude of the moving speed, to hand over the communicating base station, or to change the standby base station .

  For example, when a mobile communication terminal in communication moves at a high speed, a base station with a larger cell radius has a larger reception quality offset value, and a base station with a larger cell radius has actually received the mobile communication terminal. As a reception signal having a quality higher than the reception signal quality is received, the base station having a large cell radius is preferentially selected by updating using the reception quality offset value, and handover switching is performed. Control is performed so that handover control does not occur frequently during high-speed movement. 1 does not show the handover control unit 11a and the reception quality offset value 11b (handover control parameter, standby control parameter) only for the base station 11, but the other base stations 12, 13,... Is also provided. In addition, the reception quality offset values provided in the base stations 11, 12,..., 15 may hold the same value, or may hold different values.

  FIG. 2 is a block diagram showing an example of a mobile communication terminal according to the present invention, which is an example of a terminal applied to the mobile communication system as shown in FIG. In FIG. 2, the mobile communication terminal 20 includes at least a communication unit 21 that transmits and receives signals to and from the base station, a signal processing unit 22 that processes transmission and reception signals to and from the base station, and a moving speed of the mobile communication terminal 20 Is provided with a speed detecting unit 23 for detecting the control and a control unit 24 for controlling each unit.

  Here, the control unit 24 includes various operations necessary for mobile communication of the mobile communication terminal 20, including operations related to handover control for switching a base station in communication and operations related to standby cell selection for changing a standby base station. A handover control unit 24a that performs at least the operation related to handover control together with the handover control of the base station, and the standby that controls the operation related to standby control that switches to the optimum base station in the standby state The control part 24b and the base station information detection part 24c which detects the information of each base station are provided. Here, the base station information detection unit 24c receives information specifying each base station (in the case of FIG. 1, base stations 11, 12,..., 15) and base station information including the received signal quality value from each base station. Detection is performed for each base station, and in some cases, detection is performed including information for estimating the cell radius of each base station.

Next, a first reference example of the present invention will be described with reference to the processing flow diagram of FIG. 3, taking the configuration shown in FIGS. 1 and 2 as an example. FIG. 3 is a process flow diagram showing the first embodiment of the present invention. Here, first, it is assumed that the mobile communication terminal 20 exists at the position 16 in FIG. 1 and is in communication with the base station 11.

  First, the mobile communication terminal 20 measures the reception quality of signals received from the communicating base station 11 and the surrounding base stations 12, 13, 14, 15 in the communication unit 21, and identifies each base station. Together with the information, the base station information detecting unit 24c detects the base station information (step S1). Next, the mobile communication terminal 20 measures the movement speed V of the mobile communication terminal 20 in the speed detection unit 23 (step S2). The mobile communication terminal 20 receives information on the base station including the reception quality of each base station 11, 12,..., 15 measured and detected in steps S1 and S2, and information on the moving speed V of the mobile communication terminal 20. Transmit to the base station 11 (step S3).

  The base station 11 that has received the information on the base station including the reception quality of each base station 11, 12,..., 15 and the information on the moving speed V of the mobile communication terminal 20 is the base station 11, 12,. The cell radius of each of the base stations 11, 12,..., 15 included in the base station information received from the mobile communication terminal 20 is determined based on the transmission power of 15 and the information on the frequency to be used. Is grouped into a base station group (base station 15 in the case of FIG. 1) and a base station group (base stations 11 to 14 in the case of FIG. 1) having a small cell radius (step S4). For example, in the case of a mobile communication system using 2 GHz and 800 MHz, the cell radius of a base station using 2 GHz becomes small and the cell radius of a base station using 800 MHz becomes large due to the magnitude of propagation loss. Based on the frequency information, such grouping can be performed immediately.

  Next, the base station 11 determines whether or not the moving speed V of the mobile communication terminal 20 is equal to or higher than a predetermined moving speed threshold Vth1 (step S5). When the moving speed V of the mobile communication terminal 20 is equal to or higher than the moving speed threshold Vth1 (YES in step S5), a base station belonging to a base station group having a large cell radius (see FIG. 1, the reception quality offset value Loff1 is applied to the reception quality of a base station belonging to a base station group having a large cell radius so that the base station 15) can be preferentially selected. Is updated (step S6). For example, when using Ec / N0 (Ratio of energy per modulation bit to the noise spectral density) defined in the 3GPP standard as an indicator of reception quality, it is determined that the higher the value, the better the quality. As the value Loff1, a positive value is set, and by adding the reception quality offset value Loff1 to the reception quality measurement value of the signal of the base station having a large cell radius, the cell radius is apparently It is determined that the reception quality of the large base station is good.

  On the contrary, when Pathloss (path loss) is used as an indicator of reception quality, it is determined that the smaller the value, the better the quality. Therefore, a negative value is set as the reception quality offset value Loff1, and the cell radius is set. By adding the reception quality offset value Loff1 to the measurement value of the reception quality of the signal of the base station having a large value, it is determined that the reception quality of the base station having a large cell radius is apparently good. .

  As described above, as the reception quality offset value Loff1, it is possible to use different positive and negative values according to the way of taking the reception quality index. Also, the absolute value of the offset value can be used as the cell radius. It is possible to make the value proportional to the base station, and further, details will be described in the second embodiment to be described later, but the base station having a large cell radius according to the moving speed of the mobile communication terminal 20 It is also possible to use different values as offset values applied to each of the base station with a small cell radius, and in any case, it is not limited to only one value. It is possible to use.

  Next, the base station 11 determines the optimum base station (a base station having a large cell radius when the mobile communication terminal 20 moves at a high speed) based on the reception quality updated in step S6 (that is, the updated reception signal quality). 15) is selected, handover control to the optimum base station is performed, and information on the selected optimum base station is notified to the mobile communication terminal 20 as handover instruction information (step S7). The mobile communication terminal 20 performs an operation related to handover control to the optimum base station based on the received handover instruction information, and changes the base station to communicate from the base station 11 to the optimum base station (when moving at high speed, the cell radius is By switching while communicating with a large base station 15), communication is continued without interruption (step S8).

  As described above, the communicating base station 11 is based on the received quality offset value Loff1 and the moving speed threshold value Vth1 held as the handover control parameters, the base station information received from the mobile communication terminal 20, and the moving speed V. When the mobile communication terminal 20 moves at a high speed by performing an operation related to the handover operation based on the handover instruction information from the base station 11, the base station having a large cell radius is performed. (In the case of FIG. 1, the base station 15) is preferentially selected, so that the number of handovers can be reduced, reducing the load on the mobile communication terminal 20 and each base station and ensuring the stability of communication. can do.

Next, a second reference example of the present invention will be described with reference to the processing flow diagram of FIG. 4, taking the configuration shown in FIGS. 1 and 2 as an example. FIG. 4 is a process flow diagram showing the second embodiment of the present invention. Here, first, it is assumed that the mobile communication terminal 20 exists at the position 16 in FIG. 1 and is in communication with the base station 11 and moves in the direction of the arrow in FIG.

In the mobile communication system according to the first reference example shown in the processing flow diagram of FIG. 3, when the moving speed V of the mobile communication terminal 20 is equal to or higher than the moving speed threshold Vth1, the reception quality of the base station having a large cell radius is reduced. In the case of the mobile communication system according to the first embodiment, the base station having a large cell radius (see FIG. 5) even when the mobile communication terminal 20 that has moved at high speed is stopped. 1 is communicating with the base station 15), the communication with the base station having a large cell radius is increased, and the mobile communication terminal 20 that is likely to move at high speed is connected to the base station having a large cell radius. There is a possibility that it is biased to communication.

  Therefore, the movement speed threshold value and the reception quality offset value used as the handover control parameter are 2 of the first movement speed threshold value Vth1, the second movement speed threshold value Vth2, the first reception quality offset value Loff1, and the second reception quality offset value Loff2, respectively. When the moving speed V of the mobile communication terminal 20 is higher than the first moving speed threshold value Vth1, the first moving speed threshold value Vth1 capable of preferentially selecting a base station having a large cell radius is applied. On the other hand, when the moving speed V is as low as the second moving speed threshold value Vth2 or less, a second reception quality offset value Loff2 that can preferentially select a base station with a small cell radius can be applied, and thereby An example that avoids biasing communication with the base station will be described as the second embodiment.

  Specifically, first, in step S11 in FIG. 4, processing of each step from step S1 to S6 in FIG. 3 (that is, processing in the range of A1 surrounded by a broken line in the flowchart of FIG. 3) is performed. When the description is repeated, the mobile communication terminal 20 determines the reception quality of the signals received from the communicating base station 11 and the surrounding base stations 12, 13, 14, 15 as the communication unit 21 and the base station information detection unit 24c. And the base station information detector 24c detects the base station information together with information for identifying each base station (step S1). Next, the mobile communication terminal 20 measures the movement speed V of the mobile communication terminal 20 in the speed detection unit 23 (step S2). The mobile communication terminal 20 receives information on the base station including the reception quality of each base station 11, 12,..., 15 measured and detected in steps S1 and S2, and information on the moving speed V of the mobile communication terminal 20. Transmit to the base station 11 (step S3).

  The base station 11 that has received the information on the base station including the reception quality of each base station 11, 12,..., 15 and the information on the moving speed V of the mobile communication terminal 20 is the base station 11, 12,. The cell radius of each base station 11, 12, ..., 15 included in the base station information received from the mobile communication terminal 20 is determined on the basis of the transmission power of 15 and the information on the frequency to be used. The group is divided into a large base station (base station 15 in FIG. 1) group and a base station (base stations 11 to 14 in FIG. 1) group having a small cell radius (step S4). Next, the base station 11 determines whether or not the moving speed V of the mobile communication terminal 20 is equal to or higher than a predetermined first moving speed threshold value Vth1 (step S5).

  When the moving speed V of the mobile communication terminal 20 is equal to or higher than the first moving speed threshold value Vth1 (YES in step S5), base stations belonging to a base station group having a large cell radius so as not to frequently switch base stations for communication. In order to be able to preferentially select (in the case of FIG. 1, the base station 15), the first reception quality offset value Loff1 is applied to the reception quality of the base stations belonging to the base station group having a large cell radius. The reception quality of the base station is updated (step S6).

Thereafter, in the second reference example, processing different from that in the first reference example is performed. That is, the base station 11 determines whether or not the moving speed V of the mobile communication terminal 20 is equal to or less than a predetermined second moving speed threshold value Vth2 (step S12). When the moving speed V of the mobile communication terminal 20 is equal to or lower than the second moving speed threshold Vth2 (YES in step S12), the base stations belonging to the base station group having a small cell radius (FIG. 1) so that the communicating base stations are not biased. In order to be able to preferentially select the base stations 11 to 14), the second reception quality offset value Loff2 is applied to the reception quality of the base stations belonging to the base station group having a small cell radius, The reception quality of the base station is updated (step S13).

  Next, based on the reception quality (that is, the updated reception signal quality) updated in step S6 or step S13 in step S11, the base station 11 selects the optimum base station (when the mobile communication terminal 20 moves at high speed, When the base station 15 has a large cell radius and is moving at a low speed less than or equal to the second moving speed threshold Vth2, the base station having the best reception quality in the moving direction among the base stations 12, 13, and 14 having a small cell radius. 14 and then the base station 13), performs handover control to the optimum base station, and notifies the mobile communication terminal 20 of information on the selected optimum base station as handover instruction information (step S14). ). The mobile communication terminal 20 performs an operation related to handover control to the optimum base station based on the received handover instruction information, and changes the base station to communicate from the base station 11 to the optimum base station (when moving at high speed, the cell radius is When moving at a large base station 15 and at a low speed, the communication is continued without interruption by switching to the base station 14 having a small cell radius and then the base station 13) (step S15).

  As described above, the communicating base station 11 includes the first reception quality offset value Loff1, the second reception quality offset value Loff2, the first movement speed threshold value Vth1, and the second movement speed threshold value that are held as the handover control parameters. When the moving speed V received from the mobile communication terminal 20 using Vth2 is equal to or higher than a predetermined first moving speed threshold Vth1, the received signal quality value for each base station received from the mobile communication terminal 20 is The value updated by adding the first reception quality offset value Loff1 is used as the updated reception signal quality of each base station. On the other hand, the movement speed V received from the mobile communication terminal 20 is a predetermined second movement speed threshold Vth2. In the case of the following, the second received quality offset value Loff2 is added to the received signal quality value for each base station received from the mobile communication terminal 20 The updated value, and updates the received signal quality of each base station, the most updated received signal quality is good base station, so that it is determined that the optimum base station to a handover.

  Thereby, when moving at high speed, a base station having a large cell radius (base station 15 in the case of FIG. 1) is preferentially selected, and when moving at low speed, a base station having a small cell radius (see FIG. 1). In the case of 1, the order of base station 14 and then base station 13) is preferentially selected, so that the number of handovers can be reduced during high-speed movement, and the load on mobile communication terminal 20 and each base station can be reduced. Reduced and ensured communication stability, and handed over from a base station with a large cell radius to a base station with a small cell radius when shifting to low speed movement, without biasing communication with a specific base station As a mobile communication system, stable operation can be performed.

Next, a first embodiment of the present invention will be described with reference to the processing flow diagram of FIG. 5 taking the configuration shown in FIGS. 1 and 2 as an example. FIG. 5 is a process flow diagram showing the first embodiment of the present invention. Here, in the first embodiment, first, the mobile communication terminal 20 is present at the position 16 in FIG. 1, but unlike the first reference example shown in FIG. It is assumed that it is in a state of communicating with the base station 11 or in a state of waiting from the base station 11.

That is, in the mobile communication system according to the first reference example shown in the processing flow diagram of FIG. 3, the case where the mobile communication terminal 20 is in communication has been described. However, the present embodiment shown as the first embodiment is described. The mobile communication terminal 20 can be handed over to an optimal base station when the mobile communication terminal 20 is communicating, and can be changed to a base station that is optimally standby even when the mobile communication terminal 20 is in a standby state. The case where it is possible will be described.

In the first embodiment shown in FIG. 5, first, the mobile communication terminal 20 receives broadcast information from the base station 11 that is communicating or awaiting, so that the base station 11 has a predetermined value. Are acquired as the moving speed threshold value Vth1 and the reception quality offset value Loff1 (step S21). Here, as described above, the moving speed threshold value Vth1 and the reception quality offset value Loff1 are used as a handover control parameter and a standby control parameter, and the mobile communication terminal 20 moves at a high speed above the moving speed threshold value Vth1. The reception quality offset value Loff1 is applied as an offset value for the reception signal quality from the base station having a large cell radius.

  Next, the mobile communication terminal 20 measures the reception quality of the signals received from the communicating base station 11 and the neighboring base stations 12, 13, 14, 15 in the communication unit 21, Together with information specifying each base station, the base station information detection unit 24c detects the base station information (step S22). Furthermore, the mobile communication terminal 20 measures the moving speed V of the mobile communication terminal 20 in the speed detecting unit 23 (step S23).

  Next, the mobile communication terminal 20 determines the base station information including the reception quality of each of the base stations 11, 12,..., 15 measured and detected in step S 22 based on information predetermined for the entire mobile communication system to be applied. From the base station having a large cell radius (base station 15 in the case of FIG. 1), and a base station having a small cell radius (base stations 11 to 14 in FIG. 1). Grouping is performed (step S24). For example, in the case of a mobile communication system using 2 GHz and 800 MHz, in general, a base station using 800 MHz has a smaller propagation loss than a base station using 2 GHz, so the cell radius is increased. be able to. Accordingly, as predetermined information about each base station of the entire mobile communication system, based on information on the frequency used by each base station, base stations using 800 MHz are grouped into a base station group having a large cell radius, and 2 GHz. The base stations using can be grouped into base station groups having a small cell radius.

  Next, the mobile communication terminal 20 determines whether or not the moving speed V of the mobile communication terminal 20 is equal to or higher than the moving speed threshold Vth1 acquired from the base station 11 in Step S21 (Step S25). When the moving speed V of the mobile communication terminal 20 is equal to or higher than the moving speed threshold Vth1 (YES in step S25), the base belonging to the base station group having a large cell radius so that the base station for communication or standby does not frequently switch. In order to be able to preferentially select a station (base station 15 in the case of FIG. 1), the reception quality offset value Loff1 is applied to the reception quality of a base station belonging to a base station group having a large cell radius, The reception quality of the base station is updated (step S26).

  Thereafter, the mobile communication terminal 20 determines whether the mobile communication terminal 20 is in communication or in standby (step S27). When the mobile communication terminal 20 is in a communication state (in the case of communication in step S27), the mobile communication terminal 20 includes the base station reception quality (that is, the updated reception signal quality) updated in step S26. Is transmitted to the communicating base station 11 as handover request information (step S28).

  Based on the base station information including the updated received signal quality received from the mobile communication terminal 20 as the handover request information, the base station 11 determines the optimum base station (if the mobile communication terminal 20 moves at high speed, the cell The base station 15) having a large radius is selected, handover control to the optimum base station is performed, and information on the selected optimum base station is notified to the mobile communication terminal 20 as handover instruction information (step S29). ).

  The mobile communication terminal 20 performs an operation related to handover control to the optimum base station based on the received handover instruction information, and changes the base station to communicate from the base station 11 to the optimum base station (when moving at high speed, the cell radius is By switching while communicating with a large base station 15), communication is continued without interruption (step S30).

  On the other hand, when the mobile communication terminal 20 is in a standby state (in the standby state in step S27), the mobile communication terminal 20 uses the base station information including the reception quality of the base station updated in step S26. If there is a base station with better quality than the base station 11 that is currently waiting (the base station 15 having a large cell radius when the mobile communication terminal 20 moves at a high speed), An operation relating to standby control for changing a station to a base station (for example, base station 15) having good reception quality of standby information from the base station 11 is performed (step S31).

  As described above, the reception quality offset value Loff1 and the moving speed threshold value Vth1 received as the handover control parameter and the standby control parameter from the communicating or standby base station 11, the base station information detected by the mobile communication terminal 20, and the moving speed Based on V, when communication is in progress, handover request information of the mobile communication terminal 20 is transmitted to the base station, and the handover control of the mobile communication terminal 20 itself is performed in cooperation with the base station 11 Thus, when moving at high speed, a base station having a large cell radius (base station 15 in the case of FIG. 1) is preferentially selected, and the number of handovers can be reduced. In addition, the load of each base station can be reduced and the stability of communication can be ensured. The reception quality is preferentially selected as the base station waits for the best optimum base station also becomes possible.

Next, a second embodiment of the present invention, taking as an example the configuration shown in FIGS. 1 and 2, it will be described with reference to process flow diagram of FIG. FIG. 6 is a process flow diagram showing the second embodiment of the present invention. Here, in the second embodiment, first, the mobile communication terminal 20 exists at the position 16 in FIG. 1 and moves in the direction of the arrow in FIG. Unlike the second reference example shown, it is assumed that the mobile station is in communication with the base station 11 or is in a standby state from the base station 11.

That is, in the mobile communication system according to the second reference example shown in the processing flow diagram of FIG. 4, the case where the mobile communication terminal 20 is in a communication state has been described, but this embodiment shown as the second embodiment is described. The mobile communication terminal 20 can be handed over to an optimal base station when the mobile communication terminal 20 is communicating, and can be changed to a base station that is optimally standby even when the mobile communication terminal 20 is in a standby state. The case where it is possible will be described.

Here, also in the second embodiment, as in the case of the second reference example, the moving speed is used to avoid biased to communication or waiting for a particular base station, as the handover control parameters and waiting control parameters As the threshold value and the reception quality offset value, two types of a first movement speed threshold value Vth1, a second movement speed threshold value Vth2, a first reception quality offset value Loff1, and a second reception quality offset value Loff2 are prepared, respectively. When the moving speed V is faster than the first moving speed threshold value Vth1, a base station having a large cell radius can be preferentially selected. On the other hand, when the moving speed V is lower than the second moving speed threshold value Vth2, Makes it possible to preferentially select a base station having a small cell radius.

In the second embodiment shown in FIG. 6, first, the mobile communication terminal 20 receives broadcast information from the base station 11 that is communicating or awaiting, so that the base station 11 has a predetermined value. Are acquired as the first moving speed threshold value Vth1, the second moving speed threshold value Vth2, the first reception quality offset value Loff1, and the second reception quality offset value Loff2 (step S41). Here, the first movement speed threshold value Vth1, the second movement speed threshold value Vth2, and the first reception quality offset value Loff1 and the second reception quality offset value Loff2 are used as a handover control parameter and a standby control parameter as described above. The first reception quality offset value Loff1 is applied as an offset value for the received signal quality from the base station having a large cell radius when the mobile communication terminal 20 is moving at a high speed equal to or higher than the first movement speed threshold Vth1. On the other hand, when the mobile communication terminal 20 is moving at a low speed equal to or lower than the second movement speed threshold Vth2, the second reception quality offset value Loff2 is set to the received signal quality from the base station having a small cell radius. This is applied as an offset value for.

  Next, the mobile communication terminal 20 measures the reception quality of the signals received from the communicating base station 11 and the neighboring base stations 12, 13, 14, 15 in the communication unit 21, Together with information specifying each base station, the base station information detection unit 24c detects the base station information (step S42). Furthermore, the mobile communication terminal 20 measures the movement speed V of the mobile communication terminal 20 in the speed detection unit 23 (step S43).

  Next, the mobile communication terminal 20 determines the base station information including the reception quality of each of the base stations 11, 12,..., 15 measured and detected in step S 42 based on information predetermined for the entire mobile communication system to be applied. From the base station having a large cell radius (base station 15 in the case of FIG. 1), and a base station having a small cell radius (base stations 11 to 14 in FIG. 1). Grouping is performed (step S44).

  Next, the mobile communication terminal 20 determines whether or not the moving speed V of the mobile communication terminal 20 is equal to or higher than the first moving speed threshold Vth1 acquired from the base station 11 in Step S41 (Step S45). When the moving speed V of the mobile communication terminal 20 is equal to or higher than the first moving speed threshold value Vth1 (YES in step S45), a base station group having a large cell radius is used so that frequent switching of communication or standby base stations does not occur. In order to be able to preferentially select the base station to which it belongs (base station 15 in FIG. 1), the reception quality offset value Loff1 is applied to the reception quality of the base station belonging to the base station group having a large cell radius. Then, the reception quality of the base station is updated (step S46).

Further, unlike the first embodiment of FIG. 5 described above, the mobile communication terminal 20 determines whether or not the movement speed V of the mobile communication terminal 20 is equal to or lower than the second movement speed threshold Vth2 acquired from the base station 11 in step S41. Is determined (step S47). When the moving speed V of the mobile communication terminal 20 is equal to or lower than the second moving speed threshold value Vth2 (YES in step S47), base stations belonging to a base station group having a small cell radius (ie, a base station with a small cell radius) are not biased. In the case of FIG. 1, the second reception quality offset value Loff2 is applied to the reception quality of the base stations belonging to the base station group having a small cell radius so that the base stations 11 to 14) can be preferentially selected. Then, the reception quality of the base station is updated (step S48).

  Thereafter, the mobile communication terminal 20 determines whether the mobile communication terminal 20 is in communication or in standby (step S49). When the mobile communication terminal 20 is in communication (when communication is performed in step S49), the mobile communication terminal 20 sets the reception quality (that is, updated reception signal quality) of the base station updated in step S46 or step S48. The information on the base station that is included is transmitted to the communicating base station 11 as handover request information (step S50).

  Based on the base station information including the updated received signal quality received from the mobile communication terminal 20 as the handover request information, the base station 11 determines the optimum base station (if the mobile communication terminal 20 moves at high speed, the cell When the base station 15 has a large radius and is moving at a low speed below the second moving speed threshold Vth2, the base station 14 having the best reception quality in the moving direction among the base stations 12, 13, and 14 having a small cell radius. Next, the base station 13) is selected, and handover control to the optimum base station is performed, and information on the selected optimum base station is notified to the mobile communication terminal 20 as handover instruction information (step S51). .

  The mobile communication terminal 20 performs an operation related to handover control to the optimum base station based on the received handover instruction information, and changes the base station to communicate from the base station 11 to the optimum base station (when moving at high speed, the cell radius is When moving at a low speed, the base station 15 is switched while communicating with the base station 14 having a small cell radius and then the base station 13), thereby continuing the communication without interruption (step S52).

  On the other hand, when the mobile communication terminal 20 is in a standby state (in the standby state in step S49), the mobile communication terminal 20 receives base station information including the reception quality of the base station updated in step S46 or step S48. Based on the base station 11, the base station having better quality than the base station 11 currently waiting (the mobile station 20 has a large cell radius when moving at a high speed, and the mobile station 20 has a small cell radius when moving at a low speed). When the base station 14 and then the base station 13) are present, the base station to be standby is selected as a base station (for example, the base station 15 or the base station 14 and then the base station 14) having good reception quality of the standby information from the base station 11. The operation related to the standby control to be changed to the station 13) is performed (step S53).

  As described above, the first reception quality offset value Loff1, the second reception quality offset value Loff2, the first movement speed threshold value Vth1, and the second reception speed parameter received as the handover control parameter and the standby control parameter from the communicating or standby base station 11 Based on the moving speed threshold Vth2, the base station information detected by the mobile communication terminal 20, and the moving speed V, the moving speed V detected by the mobile communication terminal 20 is the first moving speed threshold Vth1 received from the base station 11. In the case of the above, a value updated by adding the first received quality offset value Loff1 received from the base station 11 to the detected received signal quality value for each base station is set as the updated received signal quality of each base station, The moving speed V detected by the mobile communication terminal 20 is equal to or lower than the second moving speed threshold Vth2 received from the base station 11. If the received signal quality value for each base station is added to the second received quality offset value Loff2 received from the base station 11 and updated, the updated received signal quality of each base station is used as the updated received signal quality. A base station with good quality is determined to be an optimal base station for handover or standby.

  Thereby, when moving at high speed, a base station having a large cell radius (base station 15 in the case of FIG. 1) is preferentially selected, and when moving at low speed, a base station having a small cell radius (see FIG. 1). In the case of 1, the base station 14 and then the base station 13) are preferentially selected, so that the number of handovers in the case of communication during high-speed movement or the change of the base station to wait in the case of waiting is changed. The number of times can be reduced, the load of the mobile communication terminal 20 and each base station is reduced, the stability of the communication is ensured, and the cell radius is large when the communication is in progress when shifting to a low speed movement. Perform handover control from a base station to a base station with a small cell radius, and when waiting, specify the base station by switching from a base station with a large cell radius to a base station with a small cell radius. Without being biased to the base station, it is possible to perform stable operation as a mobile communication system.

  Note that, in the mobile communication system according to the embodiment of the present invention, the base station uses unique information (for example, a telephone number) that can identify each mobile communication terminal, and the mobile communication terminal moves as described above. It is also possible to decide whether or not to perform handover control and standby control so as to select an optimal base station according to the speed V and the cell radius of the base station, and only for the selected specific mobile communication terminal It is also possible to provide a preferentially stable mobile communication service.

  Various methods are conceivable as means for measuring the moving speed V of the mobile communication terminal. For example, a method of detecting the moving speed V using an acceleration sensor, a method of detecting the moving speed V from the frequency / phase information of the received radio signal, a method of obtaining the moving speed V from information of other speed detecting means such as GPS, A method of estimating the moving speed V based on the frequency of handover during communication and the frequency of base station change in standby, a method of acquiring the moving speed V from an external device such as a speedometer of an automobile equipped with a mobile communication terminal, and the like are conceivable.

In addition, as a channel for transmitting various information used for handover and standby control between the base station and the mobile communication terminal, a method using a broadcast channel for transmitting broadcast information or an individual channel message for each mobile communication terminal is used. It is conceivable to use various transmission paths and channels such as methods.
In addition to the method of selecting the best reception quality of each base station received from the mobile communication terminal when selecting the optimal base station for handover, the usage status of each base station (with each mobile communication terminal and A method of selecting an optimal base station by combining various conditions is also conceivable, such as preferentially selecting a base station that is relatively free in consideration of the communication status.
In addition, the definition of handover in this patent includes soft handover and hard handover, and the definition of standby is not only idle mode specified in 3GPP but also communication using common channels such as CELL_PCH, CELL_FACH, URA_PCH, etc. State is also included.
The definition of a base station in this patent includes a base station, a network controller connected to the base station, and a backbone network.

It is a block diagram which shows an example of the cell structure of the mobile communication system applied to this invention. It is a block diagram which shows an example of the mobile communication terminal concerning this invention. It is a processing flowchart which shows the 1st reference example of this invention. It is a processing flowchart which shows the 2nd reference example of this invention. It is a processing flow figure showing the 1st example of the present invention. It is a processing flowchart which shows the 2nd Example of this invention. It is a system configuration diagram showing an example of a configuration of a W-CDMA system.

Explanation of symbols

11, 12, 13, 14, 15 ... base station, 11a ... handover control unit, 11b ... received date quality offset value (handover control parameter, standby control parameter), 11z, 12z, 13z, 14z ... cell with small cell radius, 15z: Cell having a large cell radius, 16, 17: Location of mobile communication terminal, 20 ... Mobile communication terminal, 21 ... Communication unit, 22 ... Signal processing unit, 23 ... Speed detection unit, 24 ... Control unit, 24a ... Handover control , 24b ... standby control unit, 24c ... base station information detection unit, 71, 72 ... base station (2GHz), 73 ... base station (800MHz), 74 ... mobile communication terminal.

Claims (4)

A mobile communication terminal that selects a base station device to be awaited from among the plurality of base station devices based on a criterion obtained by applying a predetermined control parameter to reception quality between the plurality of base station devices,
Obtaining the control parameter from the base station device;
According to the moving speed of the mobile communication terminal, by updating the reception quality by applying the control parameters, the mobile communication terminal, characterized by determining said reference. The mobile communication terminal according to claim 1, wherein
The mobile communication terminal , wherein the control parameter is obtained from broadcast information from the base station apparatus . A communicable base station apparatus and the mobile communication terminal according to claim 1, base station apparatus and transmits the control parameters to the mobile communication terminal. The base station apparatus according to claim 3 , wherein the control parameter is transmitted to the mobile communication terminal by broadcast information .

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