JP4956571B2 - MOBILE COMMUNICATION SYSTEM, ITS CONTROL DEVICE, AND HANDOVER CONTROL METHOD - Google Patents

Description

  The present invention relates to an improvement in a mobile communication system that forms an area by, for example, a microcell system. In particular, the present invention is a technology related to switching of a base station accompanying movement of a mobile terminal, so-called handover (also referred to as handoff).

  Methods for forming an area of a mobile communication system are roughly classified into a macro cell method and a micro cell method. A typical example of the former is a so-called mobile phone system, and each radio area has a radius of several kilometers. On the other hand, for example, the PHS (Personal Handy-phone System) in Japan adopts the latter method, and the area radius is very small, about several hundred meters at most.

  In the microcell system, base stations are frequently added and removed in response to changes in local communication demand. Under such circumstances, the base station is often installed on a per-field basis without a careful plan (also referred to as a station design) such as its installation position or a positional relationship with an adjacent base station. Interference between the resulting areas is avoided by each base station autonomously dealing with it.

  In this type of system, areas are switched by a re-call from a mobile terminal at the time of handover. In a microcell system, handover frequently occurs, so that the terminal is vulnerable to high-speed movement of the terminal. In particular, if communication control after switching of the base station is delayed, communication is interrupted and the communication speed that can be obtained cannot be realized. At present, the performance of the handover largely depends on the capability of the terminal. Therefore, if the high-speed movement performance is to be improved, the cost of the terminal increases, and the cost burden on the user increases.

  In order to support high-speed communication and high-speed movement at low cost, it is a good idea to enhance the network-side processing functions related to handover. For example, estimate the location of the mobile terminal and predict the switching destination base station. This method is being studied. Patent Document 1 uses map information, and Patent Documents 2 and 3 are studying to improve handover performance by using the moving speed of a mobile terminal.

JP 2004-228881 A JP 2000-197093 A JP 2004-235800 A

  Predicting the future location of a mobile terminal on the system side can be a key point for improving handover performance. However, since the base stations are arranged almost unplanned, depending on how the mobile terminal moves, there may be a base station whose connection period ends in a very short time. In the current system, the handover destination base station is predicted without taking this into consideration, so that handover control is executed in a dark cloud, resulting in complicated processing on the system side and increased resource consumption.

  Furthermore, the system tries to perform handover prediction even when the mobile terminal is slow and the processing on the mobile terminal side is sufficient. It has been pointed out that this also puts unnecessary load on the system side and spurs resource consumption. In extreme cases, some kind of countermeasure is required because it may cause the system to run out of processing power when needed.

  The present invention has been made in view of the above circumstances, and its object is to reduce the load on the system side required for handover control and to improve high-speed movement performance at a low cost, its control apparatus, and handover control. It is to provide a method.

  In order to achieve the above object, according to one aspect of the present invention, in a mobile communication system comprising a plurality of base stations each forming a radio zone, and a mobile terminal that switches a connection destination base station by handover accompanying movement A database that associates, for each permutation in which a plurality of base stations are arranged, a frequency in which the permutation occurs in a history of handovers that have occurred in the mobile communication system, and a coverage period of a mobile terminal for each base station A construction means for constructing as the mobile terminal accumulates, a prediction means for predicting a next station, which is a base station to which the mobile terminal is connected next, based on the database, and a connection period between the mobile station and the next station. Estimating means for estimating based on a database, and instructing the mobile terminal to hand over to the next station if the connection period is equal to or shorter than a prescribed maximum period Mobile communication system, comprising an indication means.

  By taking such means, handover control from the system side to the mobile terminal is canceled in a case where the connection period is expected to be excessively long. This is because the moving speed of such a mobile terminal is considered to be not high, so that high-speed handover control is essentially unnecessary. In other words, handover control from the system side is performed only for mobile terminals that move at a certain high speed, and a relatively low-speed mobile terminal switches the area by requesting a re-call. To implement. As described above, since it is possible to intelligently determine whether or not to perform handover prediction based on the connection period, it is possible to prevent unnecessary use of system resources and to reduce the load on the system side.

  According to the present invention, it is possible to provide a mobile communication system, a control apparatus thereof, and a handover control method capable of reducing the load on the system side required for handover control and improving high-speed movement performance at low cost.

1 is a system diagram showing an embodiment of a mobile communication system according to the present invention. The functional block diagram which shows the control apparatus G11 of FIG. The figure which shows an example of the adjacent base station information 44a in 1st Embodiment of this invention. The block diagram which shows the function with which the main-control part 45 of FIG. 2 is equipped. The figure which shows an example of the process sequence in control apparatus G11 in 1st Embodiment of this invention. The figure which shows an example of arrangement | positioning of a base station, and the movement path | route of a mobile terminal. The figure which shows an example of the adjacent base station information 44a in 2nd Embodiment of this invention. The figure which shows an example of the relationship between the staying period in the base station of a mobile terminal, and a moving speed. The figure which shows an example of the determination result of the moving speed of the mobile terminal PS. The figure which shows an example of the process sequence in control apparatus G11 in 2nd Embodiment of this invention.

  FIG. 1 is a system diagram showing an embodiment of a mobile communication system according to the present invention. This system is formed with a communication network 100 and control devices G11 and G12 connected thereto as a core. The communication network 100 is, for example, a private network of a carrier, and specifically, a packet communication network such as an IP (Internet Protocol) network, an IP-VPN (IP-Virtual Private Network) connection service, or an ISDN (Integrated Service Digital Network). Etc. The communication network 100 is connected to the Internet 300 via the gateway 200. In addition, the communication network 100 is provided with a server device 400 for remotely controlling the control devices G11 and G12 and providing various communication services.

  The control device G11 accommodates the base station CS11 via an individual line. The control device G12 accommodates the base station CS12 via another individual line. That is, the base stations CS11 and CS12 are under the control of different control devices. Of course, each control device G11, G12 accommodates a plurality of base stations as well as the base stations CS11, CS12. The plurality of base stations are distributed and accommodated in one of the control devices G11 and G12.

  Each base station including CS11 and CS12 forms a radio zone, and accommodates mobile terminals PS (PS11 and PS12) located in the radio zone via a radio channel. As the mobile terminals PS11 and PS12 move, they hand over between radio zones and switch base stations to be connected. The control devices G11 and G12 can form a communication link with each other via the communication network 100, and the mobile terminals PS11 and PS12 may communicate with each other via the link. Furthermore, the mobile terminals PS11 and PS12 can access the Internet 300 via the gateway 200.

  In addition to this, the system of FIG. 1 is provided with a relay unit for connecting a personal computer (PC) or a fixed telephone (TEL) to the control devices G11 and G12. In particular, if voice call software is installed, a PC can be used as a telephone. Furthermore, an access point (not shown) compliant with a wireless LAN (Local Area Network) standard may be connected to the control devices G11 and G12.

  The control devices G11 and G12 perform various controls such as exchange processing or protocol conversion between opposing devices (such as the gateway 200 and the control device of the communication partner) in order to realize end-to-end communication between communication terminals. Bear. The control devices G11 and G12 specify signals (digital signals such as audio data, video and image data, data for performing various services, etc.) communicated via the base station via the communication network 100. Process according to the communication type.

  FIG. 2 is a functional block diagram showing the control device G11 of FIG. The control device G12 has the same configuration. The control device G11 includes a packet switch unit 41, a base station interface unit 42, a network interface unit 43, a memory 44, and a main control unit 45. Among these, the base station interface unit 42 performs an interface process for accommodating the base station CS11 (and a subordinate base station not shown) via an individual line. The network interface unit 43 performs interface processing with the communication network 100.

  Each of the base station interface unit 42 and the network interface unit 43 has a function of exchanging IP packets, and these IP packets are exchanged via the packet switch unit 41. Various operations inside the apparatus including packet switching are comprehensively controlled by the main control unit 45, and programs and various setting data for the operations are stored in the memory 44.

  FIG. 3 is a diagram illustrating an example of a database stored in the memory 44. That is, the memory 44 stores the adjacent base station information 44a in the storage area. The adjacent base station information 44a basically indicates the frequency, frequency, or probability of occurrence of the permutation in the history of handovers that occurred in the mobile communication system for each permutation in which three base stations under the control of each control device are arranged. It is the associated database. This database is constructed while being updated as the history of handovers of a plurality of mobile terminals passing through the base station is accumulated over time. The adjacent base station information 44a can also be shared in a synchronized state between the control devices G11 and G12.

  For example, when 5 base stations of A station, B station, C station, D station, and E station are connected to the control device, it consists of a plurality of base stations such as two, three, four or five. Permutations can be considered. In the adjacent base station information 44a according to this embodiment, a permutation composed of three of these base stations is considered. The reason for this is that in the handover prediction, “the base station that is currently communicating”, “the base station that was connected immediately before the base station that is currently communicating”, and “the base station that is currently communicating” This is because it is reasonable to consider the three "probable base stations". Of course, a permutation of four or more base stations can also be considered. In this way, although the database is enlarged, the possibility of more accurate handover prediction is increased.

  A permutation of base stations caused by a handover indicates that base stations included in the permutation are adjacent to each other. Therefore, the adjacent base station information 44a is a database indicating the relative positional relationship of base stations. The probability indicated in the adjacent base station information 44a indicates the possibility of being selected as a handover destination in the future when handover is performed from the base station before the handover to the base station currently communicating, and is sorted in descending order of numerical value for each base station. Is done.

  For example, if there are a plurality of base stations CS11, CS12, CS13, and CS14, a permutation in which three base stations are arranged in sequence is a permutation (CS11, CS12, CS13), (CS11, CS12) obtained from these three base stations. , CS14), (CS11, CS13, CS12), (CS11, CS13, CS14), (CS11, CS14, CS12), (CS11, CS14, CS13), (CS12, CS11, CS13), (CS12, CS11, CS14) ), (CS12, CS13, CS11), (CS12, CS13, CS14), (CS12, CS14, CS11), (CS12, CS14, CS13), (CS13, CS11, CS12), (CS13, CS11, CS14), (CS13, CS12, CS11), (CS13, CS1 , CS14), (CS13, CS14, CS11), (CS13, CS14, CS12), (CS14, CS11, CS12), (CS14, CS11, CS13), (CS14, CS12, CS11), (CS14, CS12, CS13) ), (CS14, CS13, CS11), (CS14, CS13, CS12). For example, in the permutation (CS12, CS11, CS14), the first is the base station CS12, the second is CS11, and the third is CS14.

When the mobile terminal PS repeats the handover to the base station, a permutation in which the connection destination base stations are arranged in order, for example, (CS11, CS14, CS12) → (CS14, CS12, CS13) is successively generated. The adjacent base station information 44a associates the generated probability, frequency, or number of times for each permutation. The probability means frequency in a broad sense, and the occurrence frequency, occurrence frequency, or occurrence frequency may be associated with each permutation in the adjacent base station information 44a.
There are also permutations that cannot occur depending on the arrangement of base stations. For example, it is conceivable that base stations that are located apart from each other are not included in the same permutation no matter how much time elapses. For such permutations, it is not necessary to provide a data storage area in the memory 44.

  By using the adjacent base station information 44a, it is possible to predict a base station that can be a partner for the next handover. For example, if the next handover destination of the mobile terminal handed over from CS11 to CS14 is the permutation having the highest probability among a plurality of permutations (CS11, CS14, CS12), (CS11, CS14, CS13), the third destination It can be selected as a base station.

  In FIG. 3, the order of [immediate base station], [base station], and [candidate base station] corresponds to the passage of time. The [candidate base station] may be selected as the next handover destination when the mobile terminal performs handover from [previous base station: base station before handover] to [base station: currently communicating base station]. Indicates a base station. This possibility is indicated by the probability (or the number of selections) associated with the accumulation of the handover history, and FIG. 3 shows a state of sorting in order of the base stations with the highest probability. For example, when the mobile terminal hands over from the base station CS12 to CS11, the candidate base station having the highest possibility as the next handover destination is the base station CS13, and the probability is 55%.

  In FIG. 3, only one base station that is closest in time to [base station] is shown as the immediately preceding base station. For example, the base station CS11 may have been handed over in the order of CS14 → CS15 → CS12 → CS11. Among these, the probability of the combination with the previous base station CS12 is registered in the adjacent base station information 44a. ing. On the other hand, the history of a plurality of previous base stations can be converted into data as information corresponding to the immediately preceding base station. In other words, the probability of the combination of CS14 → CS15 → CS12 → CS11 can be stored in a database, and the format of the adjacent base station information 44a can be freely changed in response to this.

  Furthermore, in this embodiment, the concept of a stay period is introduced, and a database is created in conjunction with the adjacent base station information 44a in FIG. The stay period is the connection period of the mobile terminal to each base station, or an average value thereof. The period from the completion of the handover to the base station to the completion of the handover to the next base station, that is, the in-service period In other words.

  FIG. 4 is a block diagram showing functions provided in the main control unit 45 of FIG. The main control unit 45 includes a database construction unit 45a, a handover prediction unit 45b, a connection period estimation unit 45c, a handover control unit 45d, a link formation unit 45e, and a speed determination unit 45f. These are processing functions realized by arithmetic processing of a CPU (Central Processing Unit) based on instructions described in a program stored in the memory 44.

  In FIG. 4, the database construction unit 45a constructs the adjacent base station information 44a of FIG. 3 with the accumulation of the history of handover that has occurred in the mobile communication system. The handover predicting unit 45b refers to the handover rate indicated in the adjacent base station information 44a and predicts the base station having the highest probability as the next handover destination base station (next station) of the mobile terminal PS in communication. .

  The connection period estimation unit 45c estimates the connection period between the mobile terminal and the next station with reference to the stay period described in the adjacent base station information 44a. The handover control unit 45d instructs the mobile terminal PS to perform handover to the next station if the estimated connection period is a value equal to or less than a predetermined length. That is, in this embodiment, the handover of the mobile terminal PS is realized under the initiative of the control device, but an instruction for that is given to the mobile terminal PS only when the stay period is not excessively long.

  In particular, the handover control unit 45d has a value for which the estimated connection period is equal to or shorter than a predetermined length (longest period) and is equal to or longer than a specified length (shortest period) different from this. Only, the mobile terminal PS is instructed to perform handover to the next station. For example, if the longest period is 300 seconds and the shortest period is 10 seconds, the system-initiated handover control is performed only when the connection period is within this range.

  In particular, if the connection period is shorter than the shortest period, this is notified to the handover predicting unit 45b. In response to this, the handover predicting unit 45b predicts a base station (next station) that can be the next connection destination of the next station with reference to the handover rate of the adjacent base station information 44a. The handover control unit 45d instructs the mobile terminal PS to perform handover to the next station.

  The link forming unit 45e forms, prior to the handover, a link for continuing communication between the mobile terminal in communication and its counterpart on the individual line of the base station predicted as the connection destination of the handover. As a result, a communication path between the mobile terminal in communication and its counterpart is secured in advance. Next, the operation of the above configuration will be described separately for the first and second embodiments. The operation of the speed determination unit 45f will be described in detail in the second embodiment.

[First Embodiment]
FIG. 5 is a diagram illustrating an example of a processing procedure in the control device G11. FIG. 6 is a diagram illustrating an example of the arrangement of base stations and the movement route of a mobile terminal. In FIG. 6, it is assumed that base stations CS11, CS13, and CS14 develop wireless zones A11, A13, and A13, respectively, and the mobile terminal PS11 moves along the road R1.

  In FIG. 5, when the mobile terminal PS11 reaches the radio zone A13 of the base station CS13, the received power from the currently connected base station CS11 decreases, and handover control is started. Then, in FIG. 5, the control device G11 predicts the handover destination base station (next station) of the mobile terminal PS (step F101). In this step, the control device G11 determines the handover rate of the adjacent base station information 44a from the history of the currently connected base station (CS11) of the mobile terminal PS and the previously connected base station (assumed CS12). To predict the next station. According to the adjacent base station information 44a of FIG. 3, the handover rate to the base station CS13 is the highest.

  However, under the situation of FIG. 6, it is conceivable that the mobile terminal PS11 immediately enters the range of the radio zone A13 and performs a handover process to the base station CS14. In such a geographical situation, the staying period of the mobile terminal PS at the base station CS13 is statistically shortened. Furthermore, if the moving speed of the mobile terminal PS11 is high, the next handover process starts immediately, so that only the processing load increases. That is, it does not make much sense to perform a handover prediction to the base station CS13.

  Therefore, in this embodiment, in the next step of FIG. 5, it is determined whether or not the staying period at the next station CS13 is equal to or shorter than a specified value (step F102). For example, if this specified value is 20 seconds (20 s), according to the adjacent base station information 44a, the stay period of the base station CS13 is 10 seconds, and it is determined Yes in this determination block.

  Then, the processing procedure moves to the next step, and the control device G11 predicts the next handover destination base station (next station) based on the relationship between the base station CS11 and the base station CS13 (step F103). . According to the adjacent base station information 44a, since there is the highest possibility of transition to the base station CS14, the base station CS14 is predicted as the next station. Therefore, the control device G11 omits the handover to the base station CS13 and instructs the mobile terminal PS to perform the handover to the next station, the base station CS14 (step F104). This procedure is indicated by arrows (1) to (3) in FIG.

  Thereafter, the control device G11 performs connection processing of the individual line with the base station CS14, and the control device G11 enters a state of waiting for the handover of the mobile terminal PS so that the base station can be switched immediately. When the handover between the mobile terminal PS and the base station CS14 is started, since a link is already formed on the individual line, communication can be started immediately. On the other hand, if the stay period is longer than the specified value in Step F102 (No), handover control to the next station (CS13) is executed without omitting the base station.

  As described above, in this embodiment, in the mobile communication system based on the autonomous distributed installation of base stations, adjacent base station information is constructed based on the handover history of the mobile terminal, and this adjacent base station information is used. To perform handover prediction. When the adjacent base station information is constructed, the time during which the mobile terminal is connected to each base station (stay period) is also stored. If the predicted connection period to the next station is less than or equal to the specified value, the next station is excluded from the handover destination, and the next handover destination base station (next next station) is predicted.

  Accordingly, unnecessary handover control can be suppressed, and high-speed handover control can be realized without wasting system resources. In this way, selecting a base station to be handed over and skipping a base station that does not need to be handed over is performed by a base station having a short stay period in a base station arrangement under a geographical condition as illustrated in FIG. It is particularly advantageous in cases where it occurs.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In this embodiment, a processing procedure mainly including the speed determination unit 45f of FIG. 4 will be described in detail. The speed determination unit 45f determines the movement speed of the mobile terminal PS in three stages of high speed, medium speed, and low speed, for example, by threshold determination using a prescribed threshold. The handover predicting unit 45b predicts a handover to the next station only for a mobile terminal (high-speed mobile terminal) whose moving speed is determined to be high by the speed determining unit 45f. The handover control unit 45d gives a handover instruction to the next station to this high-speed mobile terminal.

  FIG. 7 is a diagram showing an example of adjacent base station information 44a in this embodiment. In the adjacent base station information in FIG. 7, an index used as a reference for determining the moving speed of the mobile terminal PS is registered in association with each base station. Here, the stay period at the base station is used as an index. For example, in the base station CS12, 20 seconds (20 s) is registered as a high-speed determination criterion, and 330 seconds (330 s) is registered as a low-speed determination criterion. This means that for the base station CS12, the moving speed of a mobile terminal whose stay period is 20 seconds or less is considered high speed, and the moving speed of the mobile terminal of 330 seconds or more is considered low speed. A mobile terminal that does not satisfy either condition, that is, a mobile terminal whose stay period is between 20 seconds and 330 seconds is considered to move at medium speed.

  FIG. 8 is a diagram illustrating an example of a relationship between a staying period of a mobile terminal at a base station and a moving speed. In the graph of FIG. 8, the horizontal axis represents the stay period at the base station, and the vertical axis represents the ratio of the number of mobile terminals. This graph can be created based on statistics of the staying period of the mobile terminal in the base station. It can be determined that the longer the staying period, the slower the moving speed, and the shorter the staying period, the faster the moving speed. As an example, a high-speed mobile terminal may be a terminal held by a passenger traveling on a bullet train, a medium-speed mobile terminal may be a person who moves by bicycle or car, and a low-speed mobile terminal may be a pedestrian. People who move at low speeds can vary greatly in speed, which is reflected in the graph.

  FIG. 9 is a diagram illustrating an example of the determination result of the moving speed of the mobile terminal PS. In this embodiment, the speed determination unit 45f determines the moving speed of the mobile terminal PS to be controlled prior to handover prediction. For example, paying attention to the mobile terminal PS11, in the table of FIG. 9, the serving base station is CS11, and the stay period of the immediately preceding base station is 10 s (10 seconds). If this is applied to the adjacent base station information 44a in FIG. 7, the immediately preceding base station is CS12, and the moving speed is classified as high speed with a stay period of 20 seconds as a threshold. Accordingly, in FIG. 9, the mobile terminal PS11 is classified as high speed.

  If the staying period in the radio zone is excessively long like the mobile terminal PS12, the terminal is classified as low speed. If it is not classified as either high speed or low speed, the mobile terminal is classified as medium speed. As described above, in the second embodiment, the moving speed of the mobile terminal is roughly calculated using the stay period of the base station in the radio zone as a key, and the handover control method is changed based on the result.

  The result classified into one of high speed, medium speed, and low speed is specified in the form of a flag or the like in the call information related to each mobile terminal. For example, the call information related to the low-speed mobile terminal indicates that it is a low-speed mobile terminal in association with the terminal identification information (terminal ID or the like). The system refers to this flag and removes the mobile terminal once classified as low speed from the target of subsequent handover prediction. That is, the low-speed mobile terminal is excluded from the target of the high-speed handover process, so that resource consumption can be saved.

  FIG. 10 is a diagram illustrating an example of a processing procedure in the control device G11 in this embodiment. When the handover control is started, the control device G11 refers to the call information of the processing target mobile terminal PS (step F200) and determines the moving speed of the mobile terminal PS (step F201). The low-speed mobile terminal (Yes in Step F201) is excluded from the target of handover prediction (Step F205), and enters a state of waiting for a normal handover.

  If the speed is not at least low (No in Step F201), the control device G11 acquires the stay period of the mobile terminal PS in the immediately preceding base station from the adjacent base station information 44a (Step F202). From the stay period obtained here or from the call information flag, the control device G11 re-determines the speed of the mobile terminal PS (step F203).

  If medium speed is determined in this step, handover prediction is performed in a normal form. That is, prediction to the next station is performed using the adjacent base station information, and a handover instruction to the next station is given from the system side to the mobile terminal PS. On the other hand, for the high-speed mobile terminal PS (No in step F203), prediction to the next station is performed, and handover prediction is performed using a method specialized for high-speed movement (step F204).

  As described above, in the second embodiment, the neighboring base station information 44a is managed together with the staying period of the mobile terminal, and a threshold value based on the staying period is provided so that the mobile terminal with a short staying period can be operated at high speed. A mobile terminal with a long period of time is classified as low speed, and a terminal that is neither of them is classified as medium speed. Based on the results, terminal-driven handover control (low speed: no prediction control for the next station), normal handover prediction control (medium speed: prediction to the next station driven by the system), high-speed handover control (high-speed: system (Prediction to the next station by the initiative) is carried out according to the moving speed.

  If the staying period in the wireless zone is longer than a certain value, it is determined that the moving speed of the terminal is low, the handover predictive control is stopped, and the terminal initiated handover process is started. If it is not subject to handover prediction, autonomous handover control is continued during communication. As a result, the system load is reduced, and handover control of other high-speed mobile terminals is stably realized.

  Even with such control, it is possible to suppress handover prediction to a terminal (such as a pedestrian) whose movement speed is slow and does not require high-speed handover processing, and the processing load on the system side can be reduced. Further, for a terminal on a vehicle moving at a high speed such as a Shinkansen, it becomes possible to perform high-speed handover control with skipping of the base station, and the effect of reducing the processing load is further increased.

  As described above, according to these embodiments, it is possible to reduce the load on the system side required for handover control, and thus it is possible to improve the high-speed movement performance at a low cost, its control apparatus, and handover A control method can be provided.

  The present invention is not limited to the above embodiment. For example, in the adjacent base station information 44a in FIG. 7, the stay period of the high-speed mobile terminal and the stay period of the low-speed mobile terminal are managed, but the index that is a criterion for determining the moving speed of the terminal is not limited to these. . In the second embodiment, the moving speed of the terminal is managed in three stages of low speed, medium speed, and high speed. However, it can be managed in two stages, or conversely, in four or more stages.

  Furthermore, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 100 ... Communication network, 200 ... Gateway, 300 ... Internet, 400 ... Server apparatus, G11, G12 ... Control apparatus, CS11, CS12 ... Base station, PS11, PS12 ... Mobile terminal, PC ... Personal computer, TEL ... Fixed telephone, 41 ... Packet switch part, 42 ... Base station interface part, 43 ... Network interface part, 44 ... Memory, 44a ... Neighboring base station information, 45 ... Main control part, 45a ... Database construction part, 45b ... Handover prediction part, 45c ... Connection Period estimation unit, 45d ... handover control unit, 45e ... link formation unit, 45f ... speed determination unit

Claims (13)

In a mobile communication system comprising a plurality of base stations each forming a radio zone and a mobile terminal that switches a connection destination base station by handover accompanying movement,
For each permutation in which a plurality of base stations are arranged, a database that associates the frequency of permutation in the history of handovers that occurred in the mobile communication system and the mobile terminal's coverage period for each base station Construction means to build with accumulation,
Prediction means for predicting a next station, which is a base station to which the mobile terminal is connected next, based on the database;
Estimating means for estimating a connection period of the mobile terminal with the next station based on the database;
A mobile communication system comprising: instruction means for instructing the mobile terminal to perform handover to the next station if the connection period is equal to or shorter than a prescribed maximum period. The said instruction | indication means instruct | indicates the hand-over to the said next station to the said mobile terminal, if the said connection period is below the said longest period and more than a prescribed shortest period. Mobile communication system. If the connection period is shorter than the shortest period, the prediction means predicts a next station that is a base station to which the next station is connected based on the database,
The mobile communication system according to claim 1, wherein the instructing unit instructs the mobile terminal to perform a handover to the next station. Further, a speed determination means for determining the moving speed of the mobile terminal in at least three stages of high speed, medium speed, and low speed with reference to a predetermined threshold from the history of the period of the mobile terminal to each base station. With
The predicting means predicts the next station for a medium speed mobile terminal whose moving speed is determined to be medium by the speed determining means,
The mobile communication system according to claim 1, wherein the instructing unit instructs the medium-speed mobile terminal to perform a handover to the next station. The prediction means predicts a next station which is a base station of a next connection destination of the next station for a high speed mobile terminal determined to have a high movement speed by the speed determination means,
The mobile communication system according to claim 4, wherein the instructing unit instructs the high-speed mobile terminal to perform handover to the next station. The plurality of base stations are connected to the mobile communication system via individual lines, respectively.
2. The link forming means for forming a link for continuing communication between the mobile terminal and its counterpart on the individual line of the next station prior to the handover. The mobile communication system described. A control device that accommodates a plurality of base stations that accommodates mobile terminals that move by handing over between radio zones of a mobile communication system via individual lines, respectively,
For each permutation in which a plurality of base stations are arranged, a database that associates the frequency of permutation in the history of handovers that occurred in the mobile communication system and the mobile terminal's coverage period for each base station Construction means to build with accumulation,
Prediction means for predicting a next station, which is a base station to which the mobile terminal is connected next, based on the database;
Estimating means for estimating a connection period of the mobile terminal with the next station based on the database;
A control apparatus comprising: instruction means for instructing the mobile terminal to perform handover to the next station if the connection period is equal to or shorter than a prescribed maximum period. The said instruction | indication means instruct | indicates the hand-over to the said next station to the said mobile terminal, if the said connection period is below the said longest period and more than a prescribed | regulated shortest period, Control device. If the connection period is shorter than the shortest period, the prediction means predicts a next station that is a base station to which the next station is connected based on the database,
8. The control apparatus according to claim 7, wherein the instructing unit instructs the mobile terminal to perform handover to the next station. Further, a speed determination means for determining the moving speed of the mobile terminal in at least three stages of high speed, medium speed, and low speed with reference to a predetermined threshold from the history of the period of the mobile terminal to each base station. With
The predicting means predicts the next station for a medium speed mobile terminal whose moving speed is determined to be medium by the speed determining means,
8. The control apparatus according to claim 7, wherein the instructing unit instructs the medium-speed mobile terminal to perform handover to the next station. The prediction means predicts a next station which is a base station of a next connection destination of the next station for a high speed mobile terminal determined to have a high movement speed by the speed determination means,
The control device according to claim 10, wherein the instruction unit instructs the high-speed mobile terminal to perform handover to the next station. 8. The apparatus according to claim 7, further comprising link forming means for forming a link for continuing communication between the mobile terminal and its counterpart on the individual line of the next station prior to the handover. The control device described. A handover control method implemented in a control apparatus that accommodates a base station that accommodates a mobile terminal that moves by handover between radio zones of a mobile communication system in the radio zone,
For each permutation in which a plurality of base stations are arranged, the control device associates the frequency of the permutation in the history of handovers that occurred in the mobile communication system and the coverage period of the mobile terminal for each base station Constructing a database as the history accumulates;
The control device predicts a next station, which is a base station to which the mobile terminal is connected next, based on the database;
The controller estimates a connection period of the mobile terminal with the next station based on the database;
A handover control method comprising: instructing the mobile terminal to perform a handover to the next station when the control apparatus has a connection period equal to or shorter than a predetermined maximum period.

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