JP2005184729A - Radio communication system and roaming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of conducting stable roaming. <P>SOLUTION: The radio communication system conducts radio communications between a mobile terminal MT and access points AP 1 and 2. The system comprises a location detecting device 1000 for detecting the location of the mobile terminal and a roaming determination device 2000 for determining whether an access point to be connected to the mobile terminal is changed or not based on the location of the mobile terminal detected by the location detecting device. The system conducts roaming based on instruction from the roaming determination device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless communication technique, and more particularly to a technique effective when applied to roaming such as a wireless communication system such as a wireless LAN (Local Area Network).

  Hereinafter, “roaming” is defined as “changing the access point to which the mobile terminal is connected”.

  In a conventional technology, in a wireless communication system including a plurality of access points typified by a wireless LAN and a plurality of portable terminals, the portable terminal has one access point having the highest reception strength among the plurality of access points. Select as the connection destination. Since the reception strength at the mobile terminal changes from moment to moment, if there are a plurality of access points having the same reception strength, the mobile terminal roams one after another to the access point having the highest reception strength. Under this circumstance, both the mobile terminal and the access point allocate enormous computing resources to the connection destination changing process, so that the throughput of the wireless communication system decreases. In addition, when most of the mobile terminals in the system are connected to the access point having the highest reception intensity at the same time, the communication load may be concentrated, and the communication waiting state of the mobile terminal may become extremely long. Furthermore, since the roaming destination is changed every moment depending on the state of reception strength, there is a possibility that roaming frequently occurs. Since communication is not possible during roaming, this also causes a decrease in throughput.

  An object of the present invention is to provide a technique that enables stable roaming without depending on a change in a reception state of a radio wave received by a mobile terminal when an access point to which the mobile terminal is connected is changed. .

  In the present invention, an area managed by each access point is specified. Then, the position of the terminal is measured and roaming is performed by determining which area it belongs to.

  Furthermore, when the position is measured, if a wireless LAN system is used, the position can be reliably measured even indoors.

  One aspect of the present invention is a system that performs wireless communication between a mobile terminal and an access point. This system includes a position detection device that detects the position of a mobile terminal, and a roaming determination device that determines whether to change an access point to which the mobile terminal is connected based on the position of the mobile terminal detected by the position detection device With. Then, roaming is performed based on an instruction from the roaming determination device.

  In a preferred aspect, the apparatus further comprises a position detection base station, the position detection base station measures the reception timing, reception intensity, or reception direction of the radio wave from the mobile terminal, and the position detection device detects the position of the mobile terminal from the measurement result. Is detected. In this way, the position of the portable terminal can be known stably even indoors, as compared to measuring the position using GPS (Global Positioning System) or the like. Therefore, it is suitable for application to an indoor wireless LAN or the like.

  The roaming determination device may include a storage device that stores information defining an area controlled by the access point. Furthermore, the roaming determination apparatus may include a storage device that stores information for specifying a mobile terminal belonging to the area corresponding to the area controlled by the access point.

  As a timing for position measurement, it may be configured to periodically output a signal for position detection. However, since communication throughput decreases, another plan is to limit the boundary of the area under the jurisdiction of the access point. It is conceivable that a device for instructing the portable terminal to transmit a radio wave for position detection is arranged in the vicinity. That is, the position detection is performed in an area where there is a high possibility of roaming.

  It is desirable that at least one position detection base station be arranged in the area controlled by the access point. Further, in consideration of the accuracy of position measurement, it is desirable that at least three position detection base stations are arranged in the area controlled by the access point.

  In a wireless communication system according to another aspect of the present invention, in a system that performs wireless communication between a mobile terminal and an access point, a position detection base station that receives a signal from the mobile terminal and measures reception timing; A position detection device that calculates the position of the mobile terminal using the reception timing, and a roaming determination device that determines whether to change the access point to which the mobile terminal is connected based on the position of the mobile terminal.

  When the position detection base station, the position detection device, and the roaming determination device are connected through a network of the same protocol, the entire system can be managed and controlled collectively. Furthermore, the access point is also connected by a network, and the roaming command from the roaming determination device may be sent to the mobile terminal via the access point. The access points can be arranged one-dimensionally, two-dimensionally, or three-dimensionally.

  One-dimensional is suitable when the mobile terminal moves along a predetermined route such as a belt conveyor. Two-dimensional corresponds to a case where a plurality of areas are provided on a floor with a building. Three-dimensional is a case where an access point is arranged in the height direction in a building with a colonnade or the like.

The roaming method of the present invention is a roaming method for managing a change of an access point to which a mobile terminal is connected, comprising a plurality of access points and a plurality of position detection base stations, and a plurality of position detection base stations. Receiving a signal from the mobile terminal and obtaining at least one measurement data of reception timing, reception intensity, and reception direction;
A second step of calculating the position of the mobile terminal from received data;
A third step of determining an access point to which the mobile terminal is connected based on the position of the mobile terminal;
A fourth step of instructing the portable terminal to connect to the determined access point.

  Further, the third step uses a table in which an access point, an area ID of an area managed by the access point, area information for specifying a physical range of the area, and an ID of a mobile terminal located in the area are associated. Can be done.

  According to the present invention, since roaming is performed based on the location information of the terminal, stable roaming is possible. Further, since the position detection technology of the wireless LAN system is used, it is possible to accurately detect the position indoors, and further, the position detection and roaming can be managed in an integrated manner.

  FIG. 1 is an overall view of a wireless LAN system to which the present invention is applied.

  MT is a portable terminal and is assumed to be carried by a user. AP1 and AP2 indicate wireless LAN access points (base stations). The access point AP1 is the master AP of the mobile terminal in the area 1 (AP serving as the communication destination of the mobile terminal), and the access point AP2 is the master AP of the mobile terminal in the area 1. Each access point transmits and receives information to and from the mobile terminal MT by radio waves, as in a normal wireless LAN. LS1 to LS4 are position detection base stations. The access point and the position detection base station are connected to the position detection device 1000 and the roaming determination device 2000 via the network 3000. In FIG. 1, areas 1 and 2 are areas divided by a wall 6000, but can be managed on the system by coordinates of four corners of a room partitioned by the wall 6000 as described later. Note that 5000 is a door, and 4000 is an area in which RFID described later is laid.

  In this system, the position of the mobile terminal MT can be detected. That is, the position detection base stations LS1 to LS8 receive a signal from the mobile terminal MT. Alternatively, the mobile terminal MT receives signals from the position detection base stations LS1 to LS8. The reception timing of these signals can be sent to the position detection apparatus 1000 via the network 3000 for processing, and the position of the portable terminal MT can be calculated by obtaining the propagation time difference. For LS2, LS3, LS6, and LS7, connection lines to the network 3000 are omitted in the figure. Details of reception timing generation and a position calculation method are disclosed in, for example, Japanese Patent Publication No. 2002-014152.

  Regarding the timing for measuring the position, for example, an RFID or the like is arranged in a region 4000 near the boundary between the area 1 and the area 2, and the mobile terminal MT detects that it has entered this region. It is possible to detect a position by sending a signal for position detection at the timing of the trigger. Or it is good also as sending the signal for position detection periodically using the timer given to portable terminal MT.

  FIG. 2 shows a configuration of the position detection base station LS1 of the present invention (LS1 to LS8 may have the same configuration). A signal (for example, a spread spectrum signal) received by the antenna 201 is subjected to reception processing at a high / intermediate frequency and baseband signal demodulation processing by a signal reception unit 202. The signal processed by the signal reception unit 202 is input to the delay profile generation unit 203. The delay profile generation unit 203 calculates a correlation value between the received signal and the PN code for each reception timing, and creates a delay profile indicating a value corresponding to the correlation value at each reception timing. From this delay profile, the reception timing generation unit 204 forms reception timing using a method such as comparison with a threshold level. The formed reception timing is sent to the position detection apparatus 1000 via the interface 205 and the network 3000 together with information (terminal ID, MAC address, etc.) specifying the mobile terminal MT that has transmitted the reception timing.

  FIG. 3 is a block diagram showing the configuration of the access points AP1 and AP2 of the present invention. A CPU 301, a main storage device 302, a transmission buffer 303, a reception buffer 304, a wireless LAN controller 305, a modem unit 306, an antenna 307, and an internal bus 308 are included. The wireless LAN controller 305 holds a cell ID, a master flag, its own MAC address, and a registration table 309 as data. The registration table 309 holds a pair of a MAC address and a parent MAC address. The MAC address held here is the MAC address of the wireless terminal when registration from a wireless terminal existing in the communication area of the AP is accepted, and the parent MAC address is the MAC address of the AP. . This registered data may be deleted after a predetermined time.

  In response to an instruction from a roaming determination device (to be described later), the wireless LAN controller 305 instructs the mobile terminal MT to roam to perform roaming and rewrites the registration table. In other words, the MAC address of the roaming mobile terminal is deleted from the roaming source access point registration table, and the roaming mobile terminal MAC address is added to the roaming destination access point registration table. A roaming command and information for specifying a new master AP (for example, a cell ID, a MAC address of the master AP, etc.) are transmitted from the antenna 307 to the portable terminal to be roamed.

  Data transmitted from the access point AP is sent from the main storage 302 to the transmission buffer 303 via the internal bus 308 and the wireless LAN controller 305 by the CPU 301. The data sent to the transmission buffer 303 is added with an area ID and a master flag by the wireless LAN controller 305, and the modulation / demodulation unit 306 is connected to a wireless terminal or an adjacent master AP in its communication area according to the contents of the registration table 309. And transmitted from the antenna 307. Further, the data received by the antenna 307 is sent to the reception buffer 304 by the wireless LAN controller 305 via the modem unit 306. When the received data is addressed to itself, the data is sent to the main storage device 302 via the wireless LAN controller 305 and the internal bus 308 and processed by the CPU 301. If the destination of the received data is not addressed to itself, the contents of the registration table 309 pass through the transmission buffer 303, the wireless LAN controller 305, the modem unit 306, and the antenna 307 to the wireless terminal or the adjacent master AP in the communication area. And sent again.

  FIG. 4 is a block diagram showing the configuration of the portable terminal (wireless terminal) MT of the present invention. The CPU 401, the main storage device 402, the transmission buffer 403, the reception buffer 404, the wireless LAN controller 405, the modem unit 406, the antenna 407, and the internal The bus 408 is configured. The wireless LAN controller 405 holds its own MAC address and own cell ID. Here, the own area ID is changed from the existing area ID to a new area ID by an instruction from the access point during roaming.

  Data transmitted from the wireless terminal is sent from the main storage device 402 to the transmission buffer 403 via the internal bus 408 and the wireless LAN controller 405 by the CPU 401. The data sent to the transmission buffer 403 is transmitted by the wireless LAN controller 405.

  FIG. 5 is a block diagram showing the configuration of the position detection apparatus 1000 of the present invention. A network I / F unit 501 is an interface between the network 3000 and the position detection device 1000. A user I / F unit 504 is an interface between the position detection device 1000 and its operator, and serves as an interface to a display device, a keyboard, and the like. The control unit 502 performs generation and analysis of signals transmitted / received via the network 3000, transmission / reception control, and position calculation of the mobile terminal MT. Details of the position calculation are disclosed in, for example, Japanese Patent Publication No. 2002-243827. The detected position is sent to the roaming determination device 2000 via the network 3000, and it is determined whether roaming is necessary. The storage device 503 stores system base station information and mobile station information.

  FIG. 6 is a block diagram showing the configuration of the roaming determination apparatus 2000 of the present invention. A network I / F unit 601 is an interface between the network 3000 and the position detection apparatus 1000. The control unit 602 is sent from the position detection device 1000 via the network 3000, from the set of the MAC address of each mobile terminal (or a terminal ID or the like if the mobile terminal can be specified) and the position information, By searching for area information in the roaming table 603, the area where a specific mobile terminal is located can be detected. Roaming is required if the area at the previous position measurement and the current area are different. Then, the MAC address of the master AP that manages the area is specified, and the MAC address of the mobile terminal that is the connection partner is notified to the specified master AP.

  FIG. 7 is an example of a roaming table. Here, it is a table showing AP # that is the ID number of each access point, the area ID that each access point has jurisdiction, the coordinate system that defines the area, and the mobile terminal ID that belongs to each area. In this example, the area is defined two-dimensionally, a rectangular area is assumed, and each area has coordinates of four vertices of the rectangle as data. However, as another example, a triangular or other polygonal area shape may be used, or a circular area defined by center coordinates and a radius may be used. In the case of a circular area, the areas can overlap each other. It is also possible to define a three-dimensional area. In the case of the three-dimensional case, it can be a rectangular parallelepiped area shape defined by data of eight vertices. In this case, it is preferable to arrange a plurality of access points in the height direction.

  In this example, the table has a single configuration, but may be divided as a first table that defines areas and a second table that manages terminals.

  In FIG. 7, the example which pinpoints the position of a portable terminal was shown by keeping the coordinate which shows the range of an area as a table. As another example, it may be configured to have mathematical formula data indicating the boundary line of the area and to determine which side of the boundary line the mobile terminal is present.

  FIG. 8 is a flowchart showing an outline of the roaming procedure of the present invention.

  In 801, a plurality of position detection base stations LS receive signals from the mobile terminal MT and measure the reception timing. At this time, a signal from any portable terminal MT is specified.

  In 802, each position detection base station LS transmits a signal reception timing and a portable terminal ID that is a signal transmission source to the position detection apparatus 1000.

  In 803, the position detection apparatus 1000 that has obtained the reception timing from the position detection base station LS detects the position information of the mobile terminal MT. For example, the position information may be identified by a method in which the mobile terminal periodically emits a beacon to notify its own position. In addition, an RFID or the like is installed at a specific location in the area where the system is arranged, and when the mobile terminal passes near the specific location, it is configured to emit a signal for specifying its own location as a trigger. You can also. As already described, the position detection base stations LS1 to LS4 can receive the signal from the mobile terminal MT and calculate the position of the mobile terminal MT from the reception timing. These position calculation methods are disclosed in, for example, Japanese Patent Publication No. 2002-014152. In the above embodiment, the position detection device 1000 calculates the position of the mobile terminal according to the reception timing detected by the mobile terminal MT. However, the position calculation can also be performed inside the terminal MT. However, in this case, the processing on the mobile terminal side becomes heavy.

  In 804, the position detection apparatus 1000 transmits the portable terminal ID and its position information to the roaming determination apparatus 2000 via the network 3000. Information acquired by the roaming determination device 2000 from the position detection device is information (for example, a MAC address, an ID number, etc.) for specifying the mobile terminal and position information. As the position information, absolute coordinates or relative coordinates defined in the system setting area can be considered. Here, the position detection device 1000 and the roaming determination device 2000 are connected as separate devices (servers) via the network 3000, but may be configured as the same server.

  In 805, the roaming determination device 2000 refers to the management table in the storage device 603 and detects in which area the mobile terminal is present. If the detected combination of area ID and portable terminal ID is different from the combination of area ID and portable terminal ID recorded on the table, the table is rewritten and a roaming instruction is issued.

  In 806, the roaming determination device 2000 instructs the mobile terminal MT to roam via the access point. At this time, it may be instructed only to an access point that becomes a new master AP, or may be instructed to all access points. It is more efficient to instruct only the master AP.

  Receiving the instruction in 807, the mobile terminal MT rewrites its own cell ID in its own wireless controller and roams to a new master AP.

  Upon receiving the response from the mobile terminal in 808, the new master AP rewrites the registration table in its own wireless LAN controller.

  The mobile terminal MT is instructed to roam, and the roaming is completed at 605.

  The present invention is suitable for roaming in a communication system such as a wireless LAN.

The system block diagram in the Example of this invention. The block diagram of the portable terminal of this invention. The block diagram of the access point of this invention. The block diagram of the base station for position detection of this invention. The block diagram of the position detection apparatus of this invention. The block diagram of the roaming judgment apparatus of this invention. The table figure of the roaming table of this invention. The flowchart which shows the roaming procedure of this invention.

Explanation of symbols

MT: mobile terminal AP1, AP2: access point (base station)
LS1 to LS4: base stations for position detection
1000: Position detection device
2000: Roaming judgment device
3000: Network
4000: An area where RFID is laid.
5000: Door

Claims (13)

In a system that performs wireless communication between a mobile terminal and an access point,
A position detection device for detecting the position of the mobile terminal;
A roaming determination device for determining whether to change an access point to which the mobile terminal is connected based on the position of the mobile terminal detected by the position detection device;
With
A wireless communication system that performs roaming based on an instruction from the roaming determination device. Equipped with a base station for position detection,
The position detection base station measures the reception timing of radio waves from the mobile terminal,
The wireless communication system according to claim 1, wherein the position detection device detects a position of the mobile terminal from the reception timing.   The wireless communication system according to claim 2, wherein the roaming determination device includes a storage device that stores information defining an area controlled by the access point.   The wireless communication system according to claim 3, wherein the roaming determination device includes a storage device that stores information for identifying a mobile terminal belonging to the area corresponding to the area controlled by the access point.   4. The wireless communication system according to claim 3, wherein a device for instructing the portable terminal to transmit a radio wave for position detection is arranged near a boundary of an area controlled by the access point.   The radio communication system according to claim 3, wherein at least one position detection base station is arranged in a region controlled by the access point.   4. The wireless communication system according to claim 3, wherein at least three position detection base stations are arranged in an area controlled by the access point. In a system that performs wireless communication between a mobile terminal and an access point,
A base station for position detection that receives a signal from the mobile terminal and measures reception timing;
A position detection device that calculates the position of the mobile terminal using the reception timing;
A wireless communication system comprising: a roaming determination device that determines whether to change an access point to which the mobile terminal is connected based on a position of the mobile terminal.   The wireless communication system according to claim 8, wherein the position detection base station, the position detection device, and the roaming determination device are connected by a network of the same protocol.   The wireless communication system according to claim 9, wherein the access point is connected via the network, and a roaming command from the roaming determination device is sent to the mobile terminal via the access point.   The wireless communication system according to claim 8, wherein the access points are arranged one-dimensionally, two-dimensionally, or three-dimensionally. A roaming method for managing changes of access points to which a mobile terminal is connected,
Prepare multiple access points and multiple base stations for position detection,
A first step in which the plurality of position detection base stations receive signals from the mobile terminal and obtain at least one measurement data of reception timing, reception intensity, and reception direction;
A second step of calculating the position of the mobile terminal from the received data;
A third step of determining an access point to which the mobile terminal is connected based on the position of the mobile terminal;
And a fourth step of instructing the portable terminal to connect to the determined access point.   The third step is a table in which an access point, an area ID of an area managed by the access point, area information for specifying a physical range of the area, and an ID of a mobile terminal located in the area are associated with each other. The roaming method according to claim 12 performed using

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