JP2012060342A - Control station, program, and base station selection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent a radio interference without adding a new infrastructure.SOLUTION: A control station is for selecting a base station to be connected with a mobile terminal from among a plurality of subordinately connected base stations. A terminal altitude indicating the altitude of the mobile terminal is received from the mobile terminal via any of the plurality of base stations, base station altitudes of the base stations subordinate to the control station are acquired, and a base station having a small absolute value of the difference between the terminal altitude and the base station altitude is preferentially selected.

Description

  The present invention relates to a mobile communication system that performs wireless communication between a terminal and a plurality of base stations existing in the vicinity, such as a mobile phone system, and more particularly to selection of a base station that performs wireless communication with a terminal. .

  When a terminal of this type of mobile communication system is on a high-rise building in a cell or on a hill with good visibility, not only the radio wave from the base station of the cell but also the radio wave from the base station of another cell reaches the terminal. Sometimes. Similarly, not only radio waves from the base station of the cell but radio waves from base stations of other cells installed at different altitudes may reach the terminal. In such a case, radio interference may occur when a plurality of base stations use the same frequency. For example, as shown in FIG. 8, it is assumed that the terminal is on a small hill and there are three base stations A, B, and C around the hill. Since the terminal is located at a high place, it is easy to see the terminal from any base station, radio waves arrive from any base station, and each base station tries to establish paths A, B, and C with radio waves of the same frequency f1. Then, radio wave interference occurs. At this time, there is confusion as to which route the communication should be established on the terminal side. As a result, there is an effect that the call is interrupted or the call is disconnected in the worst case.

  As a technique for solving such radio interference, for example, there is a method (picocell) in which a small base station is installed in a building and the base station in the building is not used for interference without using an external base station. . According to this technology, it is necessary to secure the installation cost and the transmission path to the small base station in order to install the small base station.

  Patent Document 1 describes a method for preventing interference by constructing an electromagnetic shield in a building. However, after constructing an electromagnetic shield in the building, a new obstacle may be generated between the building and the base station, and the radio wave arrival route before the obstacle may be blocked. In this case, in order to enable wireless communication inside and outside the building, it is necessary to change the radio wave arrival route. However, this method re-installs the electromagnetic shield on the wall surface, floor surface, ceiling surface, etc. of the building. It is difficult to realize.

  Patent Document 2 states that “when a mobile phone captures a base station located far from the mobile phone as a communication base station, the mobile phone appropriately receives a signal transmitted from the base station captured as the communication base station. On the other hand, a base station captured as a communication base station may not be able to properly receive a signal transmitted from a mobile phone, resulting in a decrease in communication quality. For the purpose of solving the “problem” (0005), it is described that a base station whose distance from a mobile communication terminal exceeds a threshold is excluded from communication partners when the mobile communication terminal exists at a reference altitude or higher. In this patent document, there is no mention about the altitude of the base station, and there is no description of referring to the altitude of the base station when selecting the base station.

JP2002-21216 JP2004-40368

  In view of the above situation, the problem to be solved by the present invention is to effectively prevent radio wave interference without requiring new infrastructure.

  As one aspect of the present invention, a control station that selects a base station to be connected to a mobile terminal from a plurality of base stations connected under its control, moves through any of the plurality of base stations. A terminal altitude acquisition means for receiving a terminal altitude indicating the altitude of the terminal from the mobile terminal, a base station altitude acquisition means for acquiring a base station altitude of a base station under the control station, and the terminal altitude acquisition means Provided is a control station comprising selection means for preferentially selecting a base station having a small absolute value of a difference between an acquired terminal altitude and a base station altitude acquired by the base station altitude acquiring means. .

  Further, according to another aspect of the present invention, any one of the plurality of base stations is provided in a computer of a control station that selects a base station to be connected to a mobile terminal from among a plurality of base stations connected under its control. A terminal altitude acquisition procedure for receiving a terminal altitude indicating the altitude of the mobile terminal from the mobile terminal, a base station altitude acquisition procedure for acquiring a base station altitude of a base station under the control station, and the terminal A program for executing a selection procedure for preferentially selecting a base station having a small absolute value of the difference between the terminal altitude acquired by the altitude acquiring means and the base station altitude acquired by the base station altitude acquiring means provide.

  Further, according to another aspect of the present invention, in a method for a control station to select a base station to be connected to a mobile terminal from among a plurality of base stations connected under the control, the terminal altitude indicating the altitude of the mobile terminal From the mobile terminal via one of a plurality of base stations connected to the control station, the terminal altitude acquisition stage acquired by the control station, and the control of the base station altitudes of the plurality of base stations Priority is given to the base station with a small absolute value of the difference between the base station altitude acquisition stage acquired by the station, the terminal altitude acquired at the terminal altitude acquisition stage, and the base station altitude acquired at the base station altitude acquisition stage. And a selection step of selecting the base station. A base station selection method is provided.

  According to the present invention, the altitude difference between the terminal altitude acquired by the altitude sensor provided on the terminal side and the base station altitude previously stored in the database or appropriately acquired by the altitude sensor provided in the base station is controlled. By using it as an index when a station selects a base station, it is possible to perform communication with improved quality without radio wave interference.

1 is a block diagram of a mobile communication system 1 according to an embodiment of the present invention. 2 is a block diagram of a control station 2. FIG. 2 is a block diagram of a base station 3. FIG. 4 is a block diagram of a terminal 4. FIG. 5 is a flowchart for explaining an operation of selecting a base station 3 connected to a terminal 4 in the control station 2. 6 is a flowchart for further explaining the operation of step S9 in FIG. 5. 6 is a diagram for explaining an example of a base station selection operation by a control station 2. FIG. It is a figure for demonstrating the condition where the terminal is in a high place and the electromagnetic wave from several base stations arrives.

  A mobile communication system 1 according to an embodiment of the present invention will be described. As shown in FIG. 1, the mobile communication system 1 includes a control station 2, base stations 3A, 3B, 3C, and a terminal 4. The base stations 3A, 3B, and 3C have the same configuration, and are hereinafter collectively referred to simply as the base station 3. For convenience of explanation, the number of base stations under the control station 2 is three, but the present invention is not limited to this, and it is applicable to those skilled in the art that the present invention can also be applied to a case where four or more base stations are under the control. It will be self-evident.

  The control station 2 is a device that controls the base stations 3A, 3B, and 3C. The base stations 3A, 3B, and 3C are connected downstream of the control station 2, and a host device (not shown) is connected upstream. Connected to a mobile communication network and a public switched telephone network. As shown in FIG. 2, the control station 2 includes a control unit 21, a database 22, an upstream data processing unit 23, a downstream data processing unit 24, and switches 25A, 25B, and 25C.

  The control unit 21 controls the operation of the control station 2. The database 22 is a storage device that stores the identification information of each base station in association with altitude information indicating the altitude of the location of the base station, that is, the altitude of the base station. For example, data having a structure as shown in Table 1 is stored in the database 22. Has been. Hereinafter, the altitude information of the base station may be referred to as the base station altitude. The value stored as the base station altitude in the database 22 may be a value measured in advance at the installation position of the base station. Alternatively, each base station is provided with a means for acquiring altitude information such as an altitude sensor and a GPS receiver, and is acquired by an altitude sensor and a GPS receiver according to a predetermined trigger and transmitted to the control station. It may be a value.

  When the reception level and terminal altitude of the terminal 4 are received via the base stations 3A, 3B, 3C and the switches 25A, 25B, and 25C, the control unit 21 compares the reception level between the base stations, and compares the terminal altitude and the database. 22, the base station altitude of each base station registered in advance is compared. The terminal altitude is information indicating the altitude of the current position of the terminal 4. Based on the comparison result, the control unit 21 selects switches 25A, 25B, 25C so that the reception level from the terminal 4 is relatively high and the terminal altitude is close to the base station altitude registered in the database. To control.

  The base station 3 will be described with reference to FIG. The base station 3 includes a wireless unit 31, a baseband processing unit 32, a CPU 33, a wired transmission path interface unit 34, and an antenna 35. The radio unit 31 converts a baseband signal into radio or converts radio into a baseband signal. The baseband processing unit 32 processes voice, data, and control signals in order to perform wireless communication with the terminal. The CPU 33 controls the entire base station 3. A wired transmission path interface (I / F) unit 34 is an interface device for connecting to the control station 2 via a wired transmission path. The antenna 35 is an antenna for transmitting and receiving radio waves with the terminal 4 to perform wireless communication.

  As the base station altitude to be registered in the database 22 of the control station 2, it is conceivable to register the base station altitude obtained by surveying in the database 22. The surveying method is not particularly limited. This method is suitable for a base station that basically does not move once installed, such as a base station of a macro cell.

  As another method, the base station 3 includes means for measuring the current position of the base station such as an altitude sensor 36 and a GPS (Global Positioning System) receiver 37 in addition to the above-described units, and a predetermined trigger. Accordingly, the altitude sensor 36 and the GPS receiver 37 measure the base station altitude and longitude and latitude, and the measurement result is notified to the control station 2 via the wired transmission line I / F unit 34. It can be considered that the base station altitude is registered in the database 22 in association with the identification information of the base station. The altitude sensor 36 measures the current altitude of the base station, the GPS receiver 37 measures the longitude and latitude, and the CPU 33 receives the base station altitude information including the base station altitude via the wired transmission I / F unit 34. Is notified to the control station 2. Examples of the positioning of the base station altitude and the like, and the trigger for notification to the control station 2 include when the base station is turned on and when communication with the mobile terminal is started at regular intervals. This method is suitable when a general user determines the installation location of a base station, such as a femtocell, picocell, or microcell base station.

  The terminal 4 will be described with reference to FIG. The terminal 4 includes a wireless unit 41, a baseband processing unit 42, an altitude sensor 43, an operation unit 44, a CPU 45, a display unit 46, an audio processing unit 47, an antenna 48, and a GPS receiver 49. The radio unit 41 converts a baseband signal into radio or converts radio into a baseband signal. The baseband processing unit 42 processes voice, data, and control signals. The altitude sensor 43 is a sensor for measuring the altitude of the current position of the terminal 4. The altitude sensor 43 is preferably a highly accurate pressure sensor using MEMS (Micro Electro Mechanical System) technology. By using this type of sensor, measurement in units of several centimeters becomes possible. The operation unit 44 is a keyboard, a pointing device, or the like for inputting numbers and characters. The CPU 45 controls the entire terminal 4. The display unit 46 is a display device such as a liquid crystal display device or an organic EL (Electro-Luminescence) display device. The audio processing unit 47 is a group of devices for inputting and outputting audio such as a microphone and a speaker. The antenna 48 is an antenna for performing radio communication with the base station 3 by transmitting and receiving radio waves. The GPS receiver 49 acquires the current longitude and latitude of the terminal 4 in cooperation with a GPS satellite (not shown).

  In order for the control station 2 to grasp the terminal location information and the communication state with the base station 3, control signals are exchanged between the base stations 3 A, 3 B, and 3 C and the terminal 4. When transmitting the terminal position to the base station 3, the terminal 4 measures the position information indicating the current vertical position of the terminal 4, that is, the terminal altitude by the altitude sensor 43 and the current horizontal direction of the terminal 4. Position information indicating the position is measured by the GPS receiver 49, and these measurement results are sent to the baseband processing unit 42 via the CPU 45 and sent out as an RF signal from the radio unit 41.

  The base station 3 that has received the RF signal by the antenna 35 converts the RF signal into a baseband signal by the radio unit 31 and converts it to a control signal, voice information, data, and the like by the baseband processing unit 32. The CPU 33 extracts the position information of the terminal 4 including the terminal altitude from the control signal and transmits it to the control station 2 via the wired transmission path I / F unit 34.

  The operation of the control station 2 when selecting one of the base stations 3A, 3B, 3C based on the terminal altitude, the reception level, and the base station altitude will be described with reference to FIG. The operation of the control station 2 will be further described. When the switches 25A, 25B, and 25C receive reports on the reception levels between the base stations 3A, 3B, and 3C and the terminal 4 (step S1), the control unit 21 compares the reported reception levels with each other. (Step S2), and the base station having the strongest reception level with the terminal 4 is extracted from the base stations 3A, 3B, and 3C (Step S3). Next, the control unit 21 obtains a difference between the reception level of the base station having the strongest reception level and the reception level of another base station (step S4), and compares this difference with a predetermined threshold (step S5). Thus, base stations whose difference is less than the threshold are extracted. As a result, one or a plurality of base stations with high reception levels are extracted from the base stations under the control station 2. Next, the control unit 21 confirms the radio wave transmission status between each of the extracted base stations 3 and the terminal 4 (step S6), and the base station that has extracted the interfering base stations in steps S3 and S6 (Step S7). If a plurality of base stations remain as candidates even at this stage, the control unit 21 selects a base station based on the terminal altitude of the terminal 4 and the extracted base station altitude of the base station (step S8).

  Step S8 will be described in more detail with reference to FIG. 6. First, the control unit 21 acquires position information including the current terminal altitude of the terminal 4 via any of the base stations under the control station 2. (Step S11). This process may be completed simultaneously with step S1. Next, the base station altitudes of the base stations extracted in steps S3 and S6 excluding the base station excluded in step S7 are acquired from the database 22 (step S12), and these base station altitudes and in step S11 The absolute value of the difference from the acquired current terminal altitude is obtained (step S13). Finally, a base station is selected such that the absolute value of the difference between the base station altitude and the terminal altitude is minimized (step S14).

  Here, the following situation shown in FIG. 7 is assumed. The base station 3A is installed at an altitude of 10 m and a distance to the terminal 4 of 5 km. The base station 3B is installed at an altitude of 70 m and a distance to the terminal 4 of 10 km. The base station 3C is installed at a position where the altitude is 0 m and the distance to the terminal is 2 km. The base station altitudes of the base stations 3A, 3B, 3C are registered in the database 22 in the form shown in Table 1. The terminal 4 is currently at an altitude of 60 m.

  The distances from the base stations 3A, 3B, and 3C to the terminal 4 are 5 km, 10 km, and 2 km, respectively. The base station 3C is the closest to the terminal, and the base station 3B is the farthest from the terminal. There is an obstacle 51 such as a building between the terminal station 3A and the base station 3A. Similarly, there is an obstacle 52 between the terminal 4 and the base station 3C. Assume that the terminal 4 and the terminal 4 communicate with each other at the same level of radio wave intensity. It is assumed that there is no interference with any base station. Assume that other base stations under control of the control station 2 have weak radio field strength for wireless communication with the terminal 4.

  Under such circumstances, the control station 2 operates as follows in accordance with the flowcharts of FIGS. First, with reference to FIG. 5, each of the base stations 3A, 3B, and 3C and the terminal 4 exchange with the same level of radio wave intensity, and the radio wave intensity of the other base stations is weak. In ~ S3, base stations 3A, 3B, and 3C are extracted as base stations having the strongest radio wave intensity. Since the radio wave intensity of the base stations 3A, 3B, and 3C is the same, the base stations 3A, 3B, and 3C are extracted in steps S4 to S6. Since interference does not occur between the base stations 3A, 3B, and 3C, the base stations 3A, 3B, and 3C remain extracted even after steps S7 and S8, and step S9 is performed for these three base stations. Applied.

  Next, with reference to FIG. 6, the step S9 in the above situation will be described. The terminal altitude of the terminal 4 = 60 m is acquired in advance at the time of step S1 or at the stage of step S11. From the table, base station altitude of base station 3A = 10 m, base station altitude of base station 3B = 70 m, and base station altitude of base station 3C = 0 m. Among these base station altitudes, the base station 3B has the smallest absolute value of the difference from the terminal altitude = 60 m. Therefore, in step S13, the control station 2 selects the base station 3B and turns on the switch 25B. The base station 3B is connected to the upstream data processing unit 23 and the downstream data processing unit 24, and the switches 25A and 25C are turned off.

  As mentioned above, although this invention was demonstrated according to embodiment, the above-mentioned embodiment and Example are illustrations and this invention is not limited to these. For example, in the above-described embodiment, the terminal includes the altitude sensor, but the altitude sensor may be omitted and the terminal altitude measured by GPS may be used. Alternatively, a database storing an electronic map including contour data is provided inside the control station 2 or on the network, and altitude information corresponding to the longitude / latitude information acquired by the GPS receiver of the terminal is acquired from the database. Thus, the terminal altitude may be acquired. Even in this case, an altitude sensor is not required for the terminal.

  Part or all of the above embodiments and examples can be described as the following supplementary notes, but are not limited thereto.

(Appendix 1)
In a control station that selects a base station to be connected to a mobile terminal from a plurality of base stations connected under its control,
A terminal altitude acquisition means for receiving a terminal altitude indicating the altitude of the mobile terminal from any of the plurality of base stations;
Base station altitude acquisition means for acquiring the base station altitude of a base station under the control station;
Selecting means for preferentially selecting a base station having a small absolute value of the difference between the terminal altitude acquired by the terminal altitude acquiring means and the base station altitude acquired by the base station altitude acquiring means. Control station.

(Appendix 2)
The control station according to appendix 1, further comprising means for extracting a part of the plurality of base stations based on a reception level from the mobile terminal prior to the selection.

(Appendix 3)
Prior to the selection, check the radio wave transmission status between each of the plurality of base stations and the mobile terminal, and if there is any interference, the base station is removed from the base station to be selected The control station according to any one of appendix 1 and appendix 2, further comprising means for excluding.

(Appendix 4)
As the base station altitude acquisition means, the base station altitude is obtained by receiving the base station altitude of the desired base station from the database for storing the base station identification information and the base station altitude of the base station in association with each other. 4. The control station according to any one of supplementary notes 1 to 3, further comprising means for acquiring.

(Appendix 5)
Supplementary notes 1 to 3, wherein the base station altitude acquiring means includes means for acquiring the base station altitude by receiving the base station altitude of the base station from a base station including means for measuring the altitude. The control station according to any one of appendix 4.

(Appendix 6)
From among a plurality of base stations connected under its control, to a computer of a control station that selects a base station to be connected to a mobile terminal,
A terminal altitude acquisition procedure for receiving a terminal altitude indicating the altitude of the mobile terminal from any of the plurality of base stations,
A base station altitude acquisition procedure for acquiring a base station altitude of a base station under the control station;
A selection procedure for preferentially selecting a base station having a small absolute value of a difference between the terminal altitude acquired by the terminal altitude acquiring unit and the base station altitude acquired by the base station altitude acquiring unit. program.

(Appendix 7)
The program according to appendix 6, further comprising executing a procedure of extracting a part of the plurality of base stations based on a reception level from the mobile terminal prior to the selection.

(Appendix 8)
Prior to the selection, check the radio wave transmission status between each of the plurality of base stations and the mobile terminal, and if there is any interference, the base station is removed from the base station to be selected The program according to any one of Supplementary Note 6 and Supplementary Note 7, wherein the program further causes the procedure to be excluded to be executed.

(Appendix 9)
As the base station altitude acquisition procedure, the base station altitude is obtained by receiving the base station altitude of the desired base station from the database for storing the base station identification information and the base station altitude of the base station in association with each other. 9. The program according to any one of appendix 6 to appendix 8, wherein the program is executed.

(Appendix 10)
Supplemental Note 6: As the base station altitude acquisition procedure, a procedure for acquiring the base station altitude is executed by receiving the base station altitude of the base station from a base station having means for measuring altitude. Thru | or the program in any one of attachment 9.

(Appendix 11)
A control station according to any one of appendix 1 to appendix 5 or a recording medium storing the program according to any one of appendix 6 to appendix 10, and a computer operating according to the program, a plurality of base stations, A mobile communication system comprising a mobile terminal comprising means for measuring the terminal altitude of the mobile terminal.

(Appendix 12)
The mobile communication system according to appendix 11, wherein the means for acquiring the terminal altitude of the mobile terminal is a pressure sensor using MEMS (Micro Electro Mechanical System).

(Appendix 13)
In a method in which a control station selects a base station to be connected to a mobile terminal from a plurality of base stations connected under its control,
A terminal altitude acquisition step in which the control station acquires a terminal altitude indicating the altitude of the mobile terminal from the mobile terminal via any of a plurality of base stations connected to the control station;
A base station altitude acquisition step in which the control station acquires base station altitudes of the plurality of base stations;
A selection step of preferentially selecting a base station having a small absolute value of a difference between the terminal height acquired in the terminal height acquisition step and the base station height acquired in the base station height acquisition step. Base station selection method.

(Appendix 14)
The base station selection method according to supplementary note 13, further comprising: extracting a part of the plurality of base stations based on a reception level from the mobile terminal prior to the selection.

(Appendix 15)
Prior to the selection, check the radio wave transmission status between each of the plurality of base stations and the mobile terminal, and if there is any interference, the base station is removed from the base station to be selected The base station selection method according to any one of Supplementary note 13 and Supplementary note 14, further comprising a step of excluding.

(Appendix 16)
In the base station altitude acquisition step, the base station altitude is obtained by receiving the base station altitude of the desired base station from a database for storing the base station identification information and the base station altitude of the base station in association with each other. The base station selection method according to any one of Supplementary Note 13 to Supplementary Note 15, which is obtained.

(Appendix 17)
In the base station altitude acquisition step, the base station altitude is acquired by receiving the base station altitude of the base station from a base station provided with means for measuring the altitude. The base station selection method according to any one of the above.

DESCRIPTION OF SYMBOLS 1 Mobile communication system 2 Control station 3A, 3B, 3C Base station 4 Terminal 21 Control part 22 Database 23 Uplink data processing part 24 Downlink data processing part 25A, 25B, 25C Switch 31, 41 Radio | wireless part 32, 42 Baseband processing part 33, 45 CPU
34 Wired transmission path interface unit 35, 48 Antenna 36, 43 Altitude sensor 37, 49 GPS receiver 44 Operation unit 46 Display unit 47 Audio processing unit

Claims (10)

In a control station that selects a base station to be connected to a mobile terminal from a plurality of base stations connected under its control,
A terminal altitude acquisition means for receiving a terminal altitude indicating the altitude of the mobile terminal from any of the plurality of base stations;
Base station altitude acquisition means for acquiring the base station altitude of a base station under the control station;
Selecting means for preferentially selecting a base station having a small absolute value of the difference between the terminal altitude acquired by the terminal altitude acquiring means and the base station altitude acquired by the base station altitude acquiring means. Control station.   2. The control station according to claim 1, further comprising means for extracting a part of the plurality of base stations based on a reception level from the mobile terminal prior to the selection.   Prior to the selection, check the radio wave transmission status between each of the plurality of base stations and the mobile terminal, and if there is any interference, the base station is removed from the base station to be selected The control station according to claim 1, further comprising means for excluding the control station.   As the base station altitude acquisition means, the base station altitude is obtained by receiving the base station altitude of the desired base station from the database for storing the base station identification information and the base station altitude of the base station in association with each other. 4. The control station according to claim 1, further comprising means for acquiring.   2. The base station altitude acquisition means, comprising: means for acquiring the base station altitude by receiving the base station altitude of the base station from a base station provided with means for measuring altitude. 5. The control station according to claim 4. From among a plurality of base stations connected under its control, to a computer of a control station that selects a base station to be connected to a mobile terminal,
A terminal altitude acquisition procedure for receiving a terminal altitude indicating the altitude of the mobile terminal from any of the plurality of base stations,
A base station altitude acquisition procedure for acquiring a base station altitude of a base station under the control station;
A selection procedure for preferentially selecting a base station having a small absolute value of a difference between the terminal altitude acquired by the terminal altitude acquiring unit and the base station altitude acquired by the base station altitude acquiring unit. program.   A control station according to any one of claims 1 to 5 or a recording medium storing the program according to claim 6, a computer operating according to the program, a plurality of base stations, and a mobile terminal thereof A mobile communication system comprising a mobile terminal comprising means for measuring terminal altitude.   8. The mobile communication system according to claim 7, wherein the means for acquiring the terminal altitude of the mobile terminal is a pressure sensor using MEMS (Micro Electro Mechanical System). In a method in which a control station selects a base station to be connected to a mobile terminal from a plurality of base stations connected under its control,
A terminal altitude acquisition step in which the control station acquires a terminal altitude indicating the altitude of the mobile terminal from the mobile terminal via any of a plurality of base stations connected to the control station;
A base station altitude acquisition step in which the control station acquires base station altitudes of the plurality of base stations;
A selection step of preferentially selecting a base station having a small absolute value of a difference between the terminal height acquired in the terminal height acquisition step and the base station height acquired in the base station height acquisition step. Base station selection method.   The base station selection method according to claim 9, further comprising: extracting a part of the plurality of base stations based on a reception level from the mobile terminal prior to the selection.

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