JP2005086439A - Handover processing system, radio base station and radio communications terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption, size and weight in a handover processing system, a radio base station and a radio communication terminal. <P>SOLUTION: In the handover processing system, the radio base station is provided with a remote communication relay processor and a local communication relay processor. The radio communication terminal performing radio communication with the radio base station is provided with a remote communication processor, a local communication processor, a handover necessity judging part and a communication processing control unit operating the local communication processor and making it perform radio communication by a local communication radio communication protocol instead of radio communication by a remote communication radio communication protocol, which is performed with a radio base station as a handover source till then, when the handover necessity judging part judges necessity of handover and making the remote communication processor retrieve a radio base station as a handover destination by using the remote communication radio communication protocol. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a handover processing system, a wireless base station, and a wireless communication terminal. For example, when handover is performed between a plurality of AP (access point) devices corresponding to wireless LAN (wireless local area network) standards such as IEEE802.11b. It is suitable for application to.

  The wireless LAN includes a wireless communication terminal (for example, a notebook computer as a client terminal) that performs wireless communication by mounting a LAN card for wireless LAN, and various servers that perform wired communication by mounting a LAN card for wired LAN. Is relayed using the AP device.

  The AP device is a relay device that performs standard conversion (protocol conversion) between the wireless LAN communication standard and the wired LAN communication standard, and performs relay processing in the data link layer of the OSI reference model.

Non-Patent Document 1 below describes a two-wave simultaneous communication type wireless LAN card in which two independent wireless communication circuits are incorporated in one PC card. In this two-wave simultaneous communication type wireless LAN card, as shown in FIG. 2, one of the two systems mounted on one PC card (MT) 3 is connected to any AP device ( While maintaining communication with the handover source AP device 1, the wireless communication circuit of the other system searches for another AP device (handover destination AP device) 2, thus realizing a smooth handover even while moving There is a possibility.
“Route develops wireless LAN card of“ 2 cards per card ”for smoother handover between base stations” http://www.watch.impress.co.jp/internet/www/article/2002/0225 /root.htm Announcement: 2002/02/25 Search: 2002/09/19

  By the way, there are various communication protocols for wireless LAN, but because of the relationship of using CSMA / CA (including carrier sense) as a medium access control method, each communication terminal (for example, wireless attached to a notebook personal computer or the like) In principle, it can be said that a relatively large transmission power is required, for example, the LAN card needs to detect a carrier transmitted by another communication terminal. If the transmission power is large, there is a problem that the power consumption is large.

  The two-wave simultaneous communication type wireless LAN card of Non-Patent Document 1 is equivalent to the fact that two such wireless LAN cards are practically mounted. Therefore, the power consumption is large, and the size of the wireless LAN card is also included. Is inevitably large and heavy.

  In order to solve this problem, in the first aspect of the present invention, when wireless communication is performed using a wireless communication protocol for remote communication for performing communication via a network, a wireless base station that relays the communication is switched. In the handover processing system, (1) the wireless base station includes a remote communication relay processing unit for processing the wireless communication protocol for remote communication, and (2) wireless communication for local communication for performing communication not via the network. A local communication relay processing unit that processes the protocol, and (3) a wireless communication terminal that performs wireless communication with the wireless base station includes a remote communication processing unit that processes the wireless communication protocol for remote communication; ) A local communication processing unit for processing the wireless communication protocol for local communication; and (5) the remote A handover necessity determination unit that determines whether or not a handover is necessary by monitoring communication quality of the communication processing unit, and (6) when the handover necessity determination unit determines that a handover is necessary, the local communication processing unit To perform wireless communication using the local communication wireless communication protocol instead of the wireless communication using the remote communication wireless communication protocol that has been performed between the handover source wireless base station and the remote communication processing. The communication unit includes a communication processing control unit that searches for a handover destination radio base station using the remote communication radio communication protocol.

  In the second aspect of the present invention, when a predetermined wireless communication terminal communicates with a wireless communication protocol for remote communication for performing communication via a network, the wireless base station relays the communication in (1) A remote communication relay processing unit for processing the wireless communication protocol for remote communication; and (2) a local communication relay processing unit for processing a wireless communication protocol for local communication for performing communication not via a network. 3) When the radio base station becomes the handover source radio base station of the radio communication terminal, the radio communication with the radio communication terminal that has been performed by the remote communication relay processing unit using the radio communication protocol for remote communication is replaced. In addition, the local communication relay processing unit performs wireless communication using the local communication wireless communication protocol. To.

  Furthermore, in the third aspect of the present invention, when communicating with a wireless communication protocol for remote communication for performing communication via a network by wireless communication with a predetermined wireless base station, a wireless base station that relays the communication is provided. In the wireless communication terminal to be switched, (1) a remote communication processing unit for processing the wireless communication protocol for remote communication, and (2) local communication for processing a wireless communication protocol for local communication for performing communication not via the network. A processing unit; (3) a handover necessity determination unit that determines whether or not a handover is necessary by monitoring communication quality of the remote communication processing unit; and (4) the handover necessity determination unit determines whether a handover is necessary. If so, the local communication processing unit is operated to perform so far with the handover source radio base station. In addition to performing wireless communication using the local communication wireless communication protocol instead of the wireless communication using the remote communication wireless protocol, the remote communication processing unit uses the remote communication wireless communication protocol to perform the handover destination wireless communication. And a communication processing control unit for searching for a base station.

  As described above, according to the present invention, it is possible to reduce power consumption, size, and weight while realizing smooth handover with short interruption time.

(A) Embodiments Hereinafter, embodiments of a handover processing system, a radio base station, and a radio communication terminal according to the present invention will be described.

(A-1) Configuration of Embodiment FIG. 3 shows an example of the overall configuration of the communication system 10 of the present embodiment.

  In FIG. 3, the communication system 10 includes three AP devices 11 to 13 and a communication terminal 14.

  Among these, the AP devices 11 to 13 basically perform protocol conversion between a wireless LAN communication protocol (for example, IEEE802.11b) and a wired LAN communication protocol (for example, IEEE802.3). It is a relay device that performs relay processing in the data link layer of the OSI reference model. For example, in uplink communication when communicating with a server on the Internet via an AP device, a MAC frame wirelessly transmitted from the communication terminal 14 on the client side according to the communication protocol for wireless LAN is transmitted to the AP device ( For example, after the MAC header is changed by the relay processing in 12), the MAC header is transmitted to a wired LAN (not shown), and the payload (IP packet) of the MAC frame is transmitted to the Internet via a router (not shown). Delivered to the server above.

  In this sense, the communication protocol for wireless LAN such as IEEE802.11b is a communication protocol for remote communication on the premise of communication via a network (in this case, via a wired LAN or the Internet). I can say that.

  Each AP apparatus 11 to 13 provides an independent cover area. That is, the AP device 11 provides the cover area E1, the AP device 12 provides the cover area E2, and the AP device 13 provides the cover area E3.

  The center of the cover area E1 is EC1, the center of the cover area E2 is EC2, and the center of the cover area E3 is EC3. In principle, the size of the cover area is determined by the distance (wireless communication distance) by which the wireless signal transmitted by each AP device (for example, 11) is effectively received by the communication terminal (for example, 14). The distance may vary under the influence of surrounding radio wave environment. In general, as the communication terminal 14 moves away from any center (for example, EC2) at the closest position, the reception power decreases, communication quality decreases, and normal reception cannot be continued. By monitoring the value of received power, the rate of occurrence of transmission errors (for example, BER), the communication terminal 14 can recognize that it is located far from the center and that handover is necessary. is there.

  The respective cover areas E1 to E3 do not necessarily have to overlap in the manner shown in the figure, but the presence of overlap is an essential precondition in order to perform smooth handover that is important in the present embodiment. It becomes. For example, the hatched area in FIG. 3 corresponds to the over buffer lap of the cover area E1 and the cover area E2.

  The frequency channels used by adjacent AP devices (for example, the AP devices 11 to 13 are adjacent to each other) can be the same or different.

  If an overlap is provided after using the same frequency channel in the adjacent AP device, radio interference will occur in the overlap part. For example, public places where many people gather, such as stations and hotel lobbies In the case of wireless LAN services that are often provided in highly functional places, etc., they are used while moving with a laptop computer, etc., so there are some areas where such radio wave interference occurs. This is because there is a high possibility that it will not be a big problem. However, in order to perform the smooth handover described above, it is necessary that radio wave interference does not occur in the overlap region.

  In addition, when the communication terminal 14 is a communication terminal with poor mobility such as a stationary personal computer, the occurrence of such radio wave interference may be a serious problem. Coincidentally, if the place where the communication terminal 14 is installed is an overlap area, there is a possibility that the change of the installation place of the communication terminal 14 (change of the layout in the office) or the like may be forced. is there.

  Therefore, in the present embodiment, the description will proceed mainly on the assumption that adjacent AP devices use different frequency channels.

  For example, in the IEEE802.11a (5.2 GHz band) which is a communication protocol for wireless LAN, four frequency channels are prepared, but in the IEEE802.11b (2.45 GHz band) described above, as shown in FIG. Fourteen frequency channels are prepared.

  The communication terminal 14 that performs remote communication via the AP device (for example, 12) may be any mobile communication terminal. For example, a notebook personal computer may be used.

  When the communication terminal 14 is located in the cover area E2 as illustrated, the remote communication of the communication terminal 14 is relayed by the AP device 12.

  However, when the communication terminal 14 moves from the position shown in the figure along, for example, the arrow D1, it moves away from the nearest center EC2, so that a decrease in the received power, an increase in the rate of occurrence of transmission errors, etc. are detected, and the necessity of handover Will be recognized. In the case of movement along the arrow D1, there are 12 handover source AP apparatuses that no longer communicate with the communication terminal 14 due to this handover, and conversely, the handover destination that communicates with the communication terminal 14 due to this handover. There are 11 AP devices. However, in actuality, the communication terminal 14 determines which AP apparatus to select as a handover destination AP apparatus from among a plurality of AP apparatuses (for example, 11 to 13), as a result of the handover destination search process performed by the communication terminal 14. Dependent. Details of the handover destination search process will be described later.

  An example of the internal configuration of the AP device 12 is shown in FIG. The internal configuration of the AP devices 11 and 13 is the same as this.

(A-1-1) Internal Configuration Example of AP Device In FIG. 4, the AP device 12 includes a remote communication relay unit 20, a local communication relay unit 21, a control unit 22, a storage unit 23, and a handover support unit. 24.

  Among these, the remote communication relay unit 20 performs protocol conversion between a wireless LAN communication protocol (for example, IEEE802.11b) and a wired LAN communication protocol (for example, IEEE802.3), and the data link described above. This is the part that performs relay processing at the layer. A normal AP device also has a function corresponding to the remote communication relay unit 20.

  Note that the communication terminal (for example, 14) that is executing the handover does not receive the relay process by the remote communication relay unit 20.

  The local communication relay unit 21 is a part that performs protocol conversion between the wireless communication protocol for local communication and the communication protocol for wired LAN (here, IEEE802.3) and performs relay processing in the data link layer. However, the local communication relay unit 21 performs such relay processing only when any communication terminal (for example, 14) performs a handover.

  Various wireless communication protocols for local communication can be used. Here, it is assumed that Bluetooth is used.

  Bluetooth is a protocol mainly intended to be used for communication between a personal computer and its peripheral devices, or between a personal computer and a mobile phone, and is not supposed to deliver data to a remote server or the like by relay processing. Therefore, as a medium access control method, TDMA / TDD is used in which a slave Bluetooth terminal transmits data (Bluetooth packet) by polling using a time slot specified from the master Bluetooth terminal.

  Here, the AP device 12 (or the local communication relay unit 21) corresponds to the master Bluetooth terminal, and the communication terminal 14 corresponds to the slave Bluetooth terminal.

  When assuming remote communication by relay processing, it is often more efficient to use a competitive communication protocol such as CSMA / CA, whereas local communication without relay processing is assumed. In this case, it is often more efficient to use a non-competing communication protocol such as polling TDMA / TDD.

  As described above, the general Bluetooth does not involve a relay process, but the local communication relay unit 21 executes the relay process.

  Note that since the format of the packet (Bluetooth packet) used in Bluetooth is different from the format of the MAC frame, the content of the relay processing performed by the local communication relay unit 21 is the same as the relay processing performed by the remote communication relay unit 20 Naturally it will be different.

  Various functions of the remote communication relay unit 20 and the local communication relay unit 21 can be realized by various implementations. However, as an example, the various functions can also be realized by implementation as shown in FIG.

  In FIG. 11, ANT 60 is an antenna for transmission / reception, LNA 61 is a low noise amplifier used for reception, PA 63 is a power amplifier used for transmission, BPF 64 is a band pass filter for transmission, BPF 62 is a band pass filter for reception, RF65 is a high-frequency circuit including a modulation function and a demodulation function for a wireless communication protocol for remote communication such as IEEE802.11b, and BB66 is a baseband circuit for the wireless communication protocol.

  Similarly, ANT67 is a transmission / reception antenna, LNA68 is a low noise amplifier used for reception, PA70 is a power amplifier used for transmission, BPF71 is a bandpass filter for transmission, and BPF69 is a bandpass filter for reception. , Bluetooth 72 is a module for processing the Bluetooth protocol.

  Further, the I / F 73 is an interface circuit, and a module (not shown) for executing relay processing is arranged on the right side of the I / F 73.

  As a module for processing the Bluetooth protocol, a CMOS one-chip module has already been commercialized. Further, since the frequency bands of Bluetooth and IEEE802.11b are the same, a system composed of ANT, LNA, BPF, and PA can be shared by Bluetooth and IEEE802.11b. In, it is not shared.

  The control unit 22 shown in FIG. 4 corresponds to a CPU (central processing unit) of the AP device 12 in terms of hardware, and can correspond to various programs such as an OS (operating system) in terms of software. is there.

  The storage unit 23 is a storage resource configured by various memories such as a RAM (Random Access Memory) and an EEPROM. Generally, the AP device is not equipped with a hard disk, but if necessary, a hard disk may be equipped as a part of the storage unit 23.

  The handover handling unit 24 is a part that performs various processes necessary for handover.

  When the AP device 12 is a handover destination, it is not necessary to perform special processing, but when it is a handover source, processing is necessary.

  When the AP device 12 is a handover source of the communication terminal 14, in the uplink direction, the communication terminal 14 that has been transmitting the MAC frame until then transmits the Bluetooth packet.

  In the relay processing related to the uplink communication, when the communication terminal 14 places and transmits an IP packet in the payload of the Bluetooth packet, the handover corresponding unit 24 of the AP device 12 receives the IP packet from the received Bluetooth packet. The packet is taken out, added with a MAC header, and transmitted to the wired LAN. When the IP header is not included in the payload of the Bluetooth packet, a destination IP address and a source IP address are separately provided. It is necessary to inform the AP device 12 of information related to the above and generate an IP header in the AP device 12.

  The handover corresponding unit 24 executes these processes.

  Of course, the processing opposite to the upward direction is performed for the downward direction.

  On the other hand, the internal configuration of the communication terminal 14 that performs remote communication via an AP device such as the AP device 12 is as shown in FIG.

(A-1-2) Internal Configuration Example of Communication Terminal In FIG. 1, the communication terminal 14 includes a remote communication unit 30, a local communication unit 31, a control unit 32, a storage unit 33, an operation unit 34, A display unit 35 and a handover processing unit 36 are provided.

  Among these, the remote communication unit 30 corresponds to the remote communication relay unit 20, the local communication unit 31 corresponds to the local communication relay unit 21, the control unit 32 corresponds to the control unit 22, and the storage unit 33 stores the storage. Since it corresponds to the unit 23, detailed description thereof is omitted.

  However, when the communication terminal 14 is a notebook personal computer or the like, the storage unit 33 usually includes a hard disk.

  Further, since the communication terminal 14 is an end terminal, it is not necessary for the remote communication unit 30 or the local communication unit 31 to perform a relay process that is executed by the AP device 12.

  The remote communication unit 30 is a part that processes a wireless communication protocol for remote communication such as IEEE802.11b and wirelessly transmits (or receives) a MAC frame to the AP device, and the local communication unit 21 is a Bluetooth protocol (or It is a part that processes (other wireless communication protocols for local communication) and transmits (or receives) a Bluetooth packet.

  In the handover, the remote communication unit 30 also stops the wireless communication for remote communication that has been performed until then according to the control from the handover processing unit 36 and searches for a handover destination AP device (the handover It has a function of collecting various information necessary for the pre-search process.

  Details of the handover destination search process and the processes before and after the handover destination search process will be described later.

  The local communication unit 31 is a part that starts wireless communication for remote communication in accordance with control from the handover processing unit 36 during handover. This wireless communication is performed by the remote communication unit 30 except during handover. When the local communication unit 31 performs this wireless communication at the time of handover, the remote communication unit 30 can collect various types of information necessary for the handover destination search process while continuing the remote communication.

  Various functions of the remote communication unit 30 and the local communication unit 31 can be realized by various implementations. However, as an example, the various functions can also be realized by the implementation shown in FIG.

  12, the meanings of ANT, LNA, PA, BPF, BB, Bluetooth, and I / F are the same as those in FIG.

  The implementation example of FIG. 12 is different from FIG. 11 in that only one system (that is, a system configured by the components 50 to 54) configured from ANT, LNA, PA, and BPF is provided. This one system is shared by a communication using a wireless communication protocol for remote communication (here, IEEE 802.11b) and a communication using a wireless communication protocol for local communication (here, Bluetooth). As described above, since the frequency bands of Bluetooth and IEEE802.11b are the same, such sharing is possible.

  In an actual implementation, the components 50 to 58 shown in FIG. 12 are mounted on, for example, a LAN card (PC card) for wireless LAN, and the LAN card is mounted on the communication terminal 14 that is a notebook computer. Is likely to become a form. In any case, since the user U1 usually carries a notebook computer with the LAN card attached when moving, the above-mentioned one system is shared between Bluetooth and IEEE802.11b, and the effect of reducing the weight is great. .

  The operation unit 34 shown in FIG. 1 is a part operated by a user U1 who uses the communication terminal 14. In the case of a notebook personal computer, for example, a pointing device such as a tracking ball, a keyboard, and the like are included in the operation unit 34.

  The display unit 35 corresponds to a display device (for example, an LCD (liquid crystal display device)) that displays a screen for the user U1 to view, and constitutes a user interface together with the operation unit 34.

  The handover processing unit 36 is a part that plays a central role in various processes related to handover. For example, when determining the necessity of handover based on various information (received power, BER value, etc.) obtained from the remote communication unit 30, or when performing the handover, the local communication unit 31 and the remote communication unit 30 are It is this handover processing unit 36 that controls.

  In the control when the handover is performed, as described above, the local communication unit 31 performs wireless communication for remote communication that has been performed by the remote communication unit 30 until then, and the remote communication unit 30 includes each frequency channel. The received power is checked multiple times. The handover processing unit 36 also selects a handover destination AP device based on the inspection result.

  The operation of the present embodiment having the above configuration will be described below with reference to the flowchart of FIG. The flowchart of FIG. 10 shows the contents of the handover destination search process and the processes before and after it, and includes steps S10 to S16.

  FIG. 8 and FIG. 9 show the operations of steps S10 to S16 from another viewpoint. FIG. 8 includes steps P1 to P7.

(A-2) Operation of Embodiment As is apparent from FIG. 3, the communication terminal 14 freely moves on the cover areas E1 to E3 as the user U1 moves. Due to this movement (for example, movement along the direction of the arrow D1), as the communication terminal 14 is further away from any center (for example, EC2) at the closest position, the received power decreases and the communication quality decreases. The normal reception cannot be continued. Here, as shown in FIG. 3, it is assumed that the communication terminal 14 is located in the cover area E2 provided by the AP device 12 and is moving in the direction of the arrow D1.

  In FIG. 10, the value of received power, the rate of occurrence of transmission errors (for example, BER), etc. are monitored, and by detecting that these values have exceeded a predetermined threshold value, for example, When the handover processing unit 36 recognizes the necessity of the handover (S10), the handover processing unit 36 causes the local communication unit 31 to perform wireless communication for remote communication that has been performed by the remote communication unit 30 until then. (S11) The remote communication unit 30 is made to check the received power related to the beacon frame of each frequency channel a plurality of times (S12). The processing from step S12 to subsequent step S14 corresponds to the handover destination search processing described above.

  Step P1 in FIG. 8 is a state before the communication terminal (MT) 14 recognizes the necessity of the handover, and the communication terminal 14 performs wireless communication with the AP device 12 using the remote communication unit 30. In the next step P2, the communication terminal 14 recognizes the necessity of handover and causes the local communication unit 31 to execute wireless communication for remote communication. In step P3, the remote communication unit 30 causes the remote communication unit 30 to receive power related to the beacon frame of each frequency channel. Are inspected multiple times.

  Specifically, at this time, the wireless communication protocol used for wireless communication for remote communication is changed from IEEE802.11b to Bluetooth. With this change, the remote communication unit 30 of the communication terminal 14 can be set to an unused state in which no processing is performed while the remote communication is continued. Therefore, the remote communication unit 30 is used for searching for a handover destination. can do. The ability to continue remote communication is effective for shortening the interruption time during which communication is interrupted and realizing a smooth handover.

  Here, since the same communication terminal 14 executes wireless communication by IEEE802.11b and Bluetooth using the same frequency band (2.4 GHz band) in parallel at the same time, the influence of radio wave interference may occur. Unavoidable. In particular, when paying attention to the medium access method, the remote communication unit 30 or the remote communication relay unit 20 that detects the carrier of the Bluetooth packet stops the transmission of the MAC frame according to CSMA / CA, so that the wireless on the IEEE802.11b side It can be inferred that there is a high possibility that the throughput will decrease due to communication.

  However, remote communication at the time of handover is performed using a Bluetooth packet, and since the MAC frame at the time of handover is used for searching for a handover destination, the Bluetooth side is given priority in terms of throughput. It can be said that sacrificing the MAC frame side is reasonable and efficient as a whole.

  For example, if the frequency bands are not overlapped by using IEEE802.11a instead of IEEE802.11b, it is difficult to share the system and the implementation as shown in FIG. 12 is difficult. Although there are some disadvantages, such a decrease in throughput can be completely eliminated.

  In step S13 following step S12, the quality of the received beacon frame is inspected. In this inspection, beacon frames of all frequency channels (14 in the case of IEEE 802.11b) possessed by the wireless communication protocol for remote communication are sequentially received, and the received electric field and communication quality are detected. At this time, beacon frames of the same frequency channel are received several times in succession, and statistical processing is performed to ensure the detection accuracy of the received electric field and communication quality (for example, BER). As an example, the data may be received three times in succession and an average value thereof may be taken.

  When the beacon frames for all frequency channels are received three times and the average of the values indicating the received electric field and communication quality is obtained, the beacon frame transmission source (AP device) corresponding to the average value indicating the most preferable is handed over It is selected as the previous AP device (S14). The larger the value of the received electric field or the smaller the BER, the higher the possibility that high quality wireless communication can be performed after handover, which is preferable.

  Here, it is assumed that the AP device 11 is selected as the handover destination AP device.

  When the AP device 11 is selected as the handover destination, the communication terminal 14 receives the beacon frame transmitted by the AP device 11 again according to the frequency channel corresponding to that corresponding to the AP device 11, and the profile of the AP device 11. After understanding the above, a “re-association” packet is transmitted to the AP apparatus 11 to establish a communication relationship (S15).

  After the communication relationship between the communication terminal 14 and the AP device 11 is established, a handover procedure in a higher layer is executed (S16). In this procedure, the session of the handover source AP device (here, 12) and the communication partner (this communication partner corresponds to, for example, the CN 85 shown in FIG. 13) is released on the wired network side, and the handover destination AP Switching to a session with the device 11 is performed. Various methods may be used for this procedure.

  For example, if a switch that supports handover processing such as that used in third-generation mobile systems is employed on the wired network side, handover with a very short interruption time becomes possible. Further, even if such a switch is not used, there is a possibility that a handover can be realized with an interruption time of about 40 msec as discussed in IEEE802.11f.

  The processes in FIG. 8 corresponding to steps S13 to S16 in FIG. 10 are steps P4 to P7.

  In Step P4, handshaking with the AP device 11 selected as the handover destination is performed. In Step P5, wireless communication (IEEE802.11b) by the remote communication unit 30 is started with the AP device 11 as the handover destination. In step P6, the wireless communication (Bluetooth) by the local communication unit 31 with the handover source AP apparatus 12 is terminated. In step P7, the wireless communication by the remote communication unit 30 to the AP device 11 is continued.

  FIG. 9 shows that a communication terminal (MT) 14 during handover searches and selects a handover destination AP device 11 while performing wireless communication with the handover source AP device 12 via Bluetooth, and performs handshaking with the selected AP device 11. It is shown that.

  In FIG. 10, after the execution of step S16 is completed, the process returns to step S10, and the loop of steps S10 to S16 is repeated each time a handover is required as the communication terminal 14 moves.

  As described above, if the frequency channels used by adjacent AP devices are the same, the AP device 11 that is the destination of the communication terminal 14 along the arrow D1 direction is also the source AP device. Since the same frequency channel as 12 is used, as shown in FIG. 6, the handover destination AP device (here, 11) can be specified with an actual measurement value of about 60 msec to 200 msec as shown in FIG. As assumed in the present embodiment, when the frequency channel used by each adjacent AP device is different, for example, as shown in FIG. 7, it takes about 1.5 seconds.

  FIG. 7 is based on the assumption of Mobile Internet Service (MIS). The beacon period of each frequency channel is 30 msec, the beacon is received three times or more and the required time per frequency channel is obtained in order to obtain the above average value. About 100 msec.

(A-3) Effect of Embodiment According to the present embodiment, a wireless communication protocol for remote communication using CSMA / CA and a wireless communication protocol for local communication using TDMA / TDD can be used at the time of handover. Since remote communication can be continued, the interruption time at the time of handover is short.

  Moreover, compared with the two-wave simultaneous communication type wireless LAN card of Non-Patent Document 1 incorporating two wireless communication circuits for processing a wireless communication protocol for remote communication using CSMA / CA, the power consumption is small. The size and weight of the device can be reduced.

(B) Other Embodiments Regardless of the above-described embodiments, the present invention can be configured as shown in FIGS.

  FIG. 13 showing an example of MIS shows a configuration of a portion corresponding to the above-described wired LAN and the Internet, which are not shown in FIG. An ISP (Internet Service Provider) network 80 is a part of the Internet, and an MT (FA) 84 is an MT (Mobile Terminal) having an FA (Foreign Agent) function and corresponds to the communication terminal 14. AP 82 corresponds to the AP device 12, and AP 83 corresponds to the AP device 11. Further, CN 85 indicates a communication partner that communicates with the MT (FA) 84 via the ISP network 80, the virtual home network 81, or the like.

  In FIG. 14 showing an example of roaming in IEEE 802.11, the STA 88 is a wireless LAN device, but corresponds to the communication terminal 14. AP 86 corresponds to the AP device 12, and AP 87 corresponds to the AP device 11. The Portal 89 is a device that serves as a connection point with other networks in the wireless LAN system, and can specifically support routers, gateways, and the like. Further, IAPP-MOVE is one of signal names used at the time of handover defined in IEEE 802.11.

  FIG. 15 shows an example of handover in IEEE 802.11. The meaning of terms is basically the same as in FIG.

  FIG. 16 shows a configuration example of a DS (Distribution System) similar to the core network of IMT-2000. It is also preferable to perform the handover of the present invention under such a DS configuration.

  In the above embodiment, a notebook personal computer is assumed as the communication terminal 14. However, in the present invention, any communication terminal can be used as long as the communication terminal has mobility.

  In the above embodiment, the same AP device (for example, 12) corresponds to a wireless communication protocol for remote communication (for example, IEEE802.11b) and a wireless communication protocol for local communication (for example, Bluetooth). An AP device (wireless LAN radio base station) that performs relay processing according to IEEE 802.11b and an AP device (Bluetooth radio base station) that performs relay processing according to Bluetooth may be prepared separately.

  In this case, the Bluetooth wireless base station may be installed at a different location from the wireless LAN wireless base station and connected on the wired network side. In the operation in this case, the communication terminal (14) that desires the handover first communicates with a nearby Bluetooth radio base station, and establishes the communication by temporarily performing a handover to the Bluetooth radio base station. Thereafter, a new handover is performed to the wireless LAN base station.

  According to this, by arranging the Bluetooth radio base station in a place where handover is likely to occur (for example, in the vicinity of the overlap), the Bluetooth cover area can be smaller than that in the above embodiment. Therefore, the transmission power of Bluetooth can be further reduced.

  Therefore, the price of the component for the wireless communication protocol for local communication (here, Bluetooth) on the communication terminal 14 side is reduced, or the wireless communication protocol for remote communication (for example, IEEE802.11b) and local communication are used. It is possible to reduce radio interference of the wireless communication protocol.

  In addition, by repeatedly installing the wireless base station of the wireless LAN and the wireless base station of Bluetooth, when the communication terminal 14 is handed over from one wireless base station to the next wireless base station for the wireless LAN, the middle is set to Bluetooth. Therefore, a linear seamless handover is possible in a linear arrangement.

  For this reason, even when the overlap does not exist in the cover area provided by the wireless LAN radio base station, there is a cover area provided by the Bluetooth radio base station between the cover area and the cover area. Can achieve a smooth handover with almost no downtime.

  In the above embodiment, the communication application is not mentioned, but the present invention can be applied to any communication application. For example, the present invention can be applied to various communication applications such as file transfer using FTP, electronic mail using SMTP, and IP telephone using VoIP technology.

  However, for example, communication applications such as file transfer by FTP and e-mail by SMTP do not require such high real-time performance, and even if the interruption time is long at the time of handover, the effect is small, but an IP phone using VoIP technology In communication applications that require high real-time performance, such as a long interruption time during handover is likely to have a significant impact on call quality. Therefore, the present invention is a communication that requires such high real-time performance. This is particularly effective when applied to an application.

  In the above description, the present invention is realized mainly by hardware, but the present invention can also be realized by software.

It is the schematic which shows the structural example of the principal part of the communication terminal used with the communication system which concerns on embodiment. It is the schematic which shows an example of the conventional handover. It is the schematic which shows the example of whole structure of the communication system which concerns on embodiment. It is the schematic which shows the structural example of the principal part of AP apparatus used with the communication system which concerns on embodiment. It is the schematic which shows the arrangement | sequence of the frequency channel of IEEE802.11b. FIG. 6 is an explanatory diagram of operations at the time of handover in the embodiment. FIG. 6 is an explanatory diagram of operations at the time of handover in the embodiment. FIG. 6 is an explanatory diagram of operations at the time of handover in the embodiment. FIG. 6 is an explanatory diagram of operations at the time of handover in the embodiment. It is a flowchart which shows the content of the handover destination search process in embodiment, and the process before and behind it. It is the schematic which shows the example of mounting regarding embodiment. It is the schematic which shows the example of mounting regarding embodiment. It is a schematic explanatory drawing of other embodiment. It is a schematic explanatory drawing of other embodiment. It is a schematic explanatory drawing of other embodiment. It is a schematic explanatory drawing of other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Communication system, 11-13 ... Access point apparatus (AP apparatus), 14 ... Communication terminal, 20 ... Remote communication relay part, 21 ... Local communication relay part, 22, 32 ... Control part, 23, 33 ... Storage part, 24 ... Handover corresponding part, 30 ... Remote communication part, 31 ... Local communication part, 34 ... Operation part, 35 ... Display part, 36 ... Handover processing part, E1 to E3 ... Cover area, EC1 to EC3 ... (of the cover area) center.

Claims (3)

In a handover processing system for switching a radio base station that relays communication when wireless communication is performed using a wireless communication protocol for remote communication for performing communication via a network,
The radio base station is
A remote communication relay processing unit for processing the wireless communication protocol for remote communication;
A local communication relay processing unit for processing a wireless communication protocol for local communication for performing communication not via a network;
A wireless communication terminal that performs wireless communication with the wireless base station
A remote communication processing unit for processing the wireless communication protocol for remote communication;
A local communication processing unit for processing the wireless communication protocol for local communication;
By monitoring the communication quality of the remote communication processing unit, a handover necessity determination unit that determines whether a handover is necessary,
When the handover necessity determination unit determines whether the handover is necessary, the local communication processing unit is operated to perform wireless communication with the wireless communication protocol for remote communication that has been performed with the handover source wireless base station. Communication control for causing the remote communication processing unit to search for a handover destination radio base station using the remote communication wireless communication protocol instead of performing wireless communication using the local communication wireless communication protocol. And a handover processing system. When a predetermined wireless communication terminal is communicating with a wireless communication protocol for remote communication for performing communication via a network, in a wireless base station that relays the communication,
A remote communication relay processing unit for processing the wireless communication protocol for remote communication;
A local communication relay processing unit for processing a wireless communication protocol for local communication for performing communication not via a network;
When the radio base station is a handover source radio base station of the radio communication terminal, instead of the radio communication with the radio communication terminal that the remote communication relay processing unit has been performing with the radio communication protocol for remote communication until then, The wireless base station, wherein the local communication relay processing unit performs wireless communication using the local communication wireless communication protocol. When communicating with a wireless communication protocol for remote communication for performing communication via a network by wireless communication with a predetermined wireless base station, in a wireless communication terminal that switches a wireless base station that relays the communication,
A remote communication processing unit for processing the wireless communication protocol for remote communication;
A local communication processing unit for processing a wireless communication protocol for local communication for performing communication not via a network;
By monitoring the communication quality of the remote communication processing unit, a handover necessity determination unit that determines whether a handover is necessary,
When the handover necessity determination unit determines whether the handover is necessary, the local communication processing unit is operated to perform wireless communication with the wireless communication protocol for remote communication that has been performed with the handover source wireless base station. Communication control for causing the remote communication processing unit to search for a handover destination radio base station using the remote communication wireless communication protocol instead of performing wireless communication using the local communication wireless communication protocol. A wireless communication terminal.

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