JP2006333360A - Radio communications system, radio terminal, and network generation method for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly constitute a network having the optimum topology where collision of packets is not generated among the networks, in the case where the control station is switched and the controlled stations isolated from the covering area of the new control station exist. <P>SOLUTION: In the radio communications system, where only one radio terminal among a plurality of radio terminals generates a network as the control station and the other radio terminals are taking part into the same network as the controlled stations, when the control station is switched to a new control station, the controlled station in the new network generated by the new control station generates a new dependent network controlled by the new network; and when the controlled station that participates in the dependent network exists, the controlled station, having generated the dependent network, operates as the control station. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique in which one of a plurality of wireless terminal devices generates a network as a control station, and another wireless terminal device participates in the network as a slave station.

  In recent years, a wireless communication system that performs data communication using a wireless transmission path between devices arranged at a short distance has been used as a highly portable network system that is not restricted by a communication cable. It is rapidly spreading due to the improvement of transmission speed, the spread of mobile terminals, and the emergence of applications suitable for mobile communications.

  In particular, as a method for wirelessly connecting computer devices at a relatively short distance, for example, a wireless LAN (Local Area Network) system using radio waves such as 2.4 GHz and 5 GHz bands is widely used.

  Further, not only computer peripheral devices but also consumer devices such as digital cameras and digital video cameras, and demands for wireless communication for connecting devices such as printers and mobile phones are increasing. Currently, these are generally connected by a wired cable such as USB or IEEE1394, but wireless connection has also been proposed as a method by which a user can easily connect these devices.

  For example, Bluetooth is known as a wireless communication method between devices at such a very short distance. Such a system is different from a wireless LAN and is intended for wireless connection in the surrounding environment of a person, which is considered to be about 10 meters at most. It is distinguished from a wireless LAN, and is a WPAN (Wireless Personal Area Network). is called.

  At present, standards for the WPAN are being developed as a group of IEEE802.15 standards, and specifications regarding network topology configuration and media access protocols are defined in the IEEE802.15.3 standard.

  The feature of WPAN when compared with wireless LAN is that each terminal station does not operate on a pre-built infrastructure, but a network is dynamically configured according to the execution status of devices and applications. is there.

  For example, in a wireless LAN infrastructure mode, each terminal station operates according to an access protocol controlled by a control station called an access point, and this access point generally has a predetermined radio station that performs its role. It is.

  On the other hand, in a piconet that is a wireless network in WPAN, a control station called PNC (Piconet coordinator) controls media access of each terminal, and a fixed radio station is not necessarily a PNC. That is, the WPAN wireless station is classified into a station having a PNC function and a station not having a PNC function, and any one of the stations having the PNC function actually generates a piconet as a PNC and controls it.

  FIG. 5 is a sequence diagram showing a piconet generation procedure in WPAN. In FIG. 5, it is assumed that there are two terminals, DEV1 and DEV2, as WPAN devices having a PNC function. Each terminal DEV1 and DEV2 may be any terminal device such as a computer device, a digital camera, a digital video camera, a printer, or a mobile phone, as long as it operates as a WPAN device having a PNC function.

  First, when power is turned on (501), DEV1 sequentially scans available frequency channels in order to determine whether or not a WPAN piconet already exists in its surrounding environment (502). If the piconet does not yet exist at this point, DEV1 having the PNC function determines that it needs to become a PNC. In this way, DEV1 selects an optimum channel from the available frequency channels (503), and starts transmitting the beacon frame 510 periodically on that channel. When transmission of this beacon frame 510 begins, DEV1 becomes a PNC as a control station, and a new piconet is generated (504).

  Also, if a piconet already exists in WPAN, the PNC that is the control station of the piconet periodically sends out a beacon frame, so DEV1 detects the beacon frame, and the piconet controlled by the PNC Try to participate. It should be noted that DEV1 has a PNC function but does not necessarily have to operate as a PNC. If another station is already operating as a PNC, it is only necessary to participate in the subordinate.

  Next, when power is turned on in DEV2 (505), DEV2 scans the frequency channel for a certain period of time in order to detect whether or not there is a piconet in the vicinity of its own station, as in DEV1 ( 506). At this time, since DEV1 has already generated a piconet as a control station, it receives the beacon frame 510 from DEV1, and DEV2 detects the piconet controlled by DEV1 (507). Here, when DEV2 participates in this piconet, DEV2 transmits a participation request command 511 to DEV1, which is the control station of the piconet, and a participation permission command 512 is returned from DEV1 to DEV2 in response to the request. (508).

  At this time, the participation request command 511 transmitted from DEV2 holds data indicating various functions of DEV2, and DEV1, which is the control station, detects various functions of newly joined DEV2 at this time. be able to. The participation permission command 512 returned from DEV1 to DEV2 holds the device ID newly assigned to DEV1 by DEV1.

  With the operation as described above, in WPAN, one of the devices constituting the piconet autonomously becomes a control station to construct a network, and data transmission 512 is possible.

  In WPAN, a TDMA (Time Division Multiple Access) method is adopted as a media access method. In this TDMA system, a terminal that wants to secure a data communication path requests the control station to allocate a communication band in advance.

  FIG. 6 is a diagram for explaining the principle of the TDMA access method in WPAN. As shown in FIG. 6, the time axis is defined as a super frame 603 that starts with a beacon 601 periodically transmitted by the PNC, and each super frame 603 has a time slot that is a period in which each terminal can use for wireless communication. It is divided into 602. The communication band that can be used by the terminal station is thus secured as a time slot on the time axis, and during that period, devices other than the terminal designated as the transmitting terminal are prohibited from transmitting radio frames.

  Each such time slot has its start time and time slot length specified in a beacon frame from the control station, and further, a source terminal (Source) and a destination terminal (Destination) in the time slot Is specified.

  Furthermore, in WPAN, a slave station participating in a certain piconet has a function of generating subordinate piconets hierarchically. In this case, the slave station that generated the dependent piconet behaves as a control station in the dependent piconet, but behaves as a slave station controlled by the control station in the parent piconet in the parent piconet. being called. With the function of operating as a dependent piconet, it is possible in WPAN to operate a plurality of piconets coexisting without causing radio frame collision with each other.

  However, when there are a plurality of independent piconets in geographical vicinity, these piconets operate asynchronously with respect to each other in time, so that the communication coverage areas of the plurality of independent piconets overlap. In existing devices, radio signals arrive asynchronously from the respective piconets, and there is a risk of radio frame collision.

  Further, in the access protocol based on the TDMA scheme, such a radio frame collision causes a significant decrease in data transfer throughput.

  In order to avoid such a decrease in throughput, in the dependent piconet in WPAN, the operations of the parent piconet and the dependent piconet are synchronized via the dependent PNC. For this reason, as described above, frame collision does not occur unlike a case where a plurality of independent piconets are arranged side by side.

  FIG. 7 is a diagram illustrating a relationship between a parent piconet and a dependent piconet. FIG. 8 is a diagram showing the operation timing of the parent piconet and the subordinate piconet.

  In FIG. 7, PNC1 is a control station of the parent piconet 701 and accommodates a plurality of terminals. Of these, DEV2 is a slave station in the parent piconet, but operates as a control station in the subordinate piconet 702, and therefore also has a role as PNC2.

  In FIG. 8, the superframe 802 of the parent piconet is managed by a beacon frame 801 periodically transmitted from PNC1. When a time slot that can be used by the subordinate piconet is assigned in the super frame 802, the subordinate PNC2 transmits a beacon frame 803 at the start of the time slot. On the other hand, since the slave stations in the subordinate piconet operate in synchronization with the beacon frame 803, the parent piconet and the subordinate piconet can collide with each other without sharing the communication path. Here, the time slot of the subordinate piconet in the superframe 802 in the parent piconet is designated by the beacon frame 801 of the parent piconet, and each time slot in the superframe in the subordinate piconet is designated by the beacon frame 803 of the subordinate piconet. .

  Further, in WPAN, a terminal that is already operating as a control station has a function of changing its role as a control station to other slave stations, which is called a PNC handover function. Here, there are mainly two conditions for the occurrence of PNC handover in WPAN. The first condition is that the slave station that newly joined the piconet has a function to operate as a PNC and has a higher function than the current PNC. The functions listed here include security support and battery operation. The priority is defined in IEEE802.15.3 as a standard for AC power supply driving or the maximum number of terminals that can be accommodated.

  The second condition for PNC handover to occur is when the current PNC wishes to leave the piconet. For example, the PNC battery may be insufficient, or the PNC may want to stop wireless communication because the PNC does not already hold data to be communicated. In such a case, generally, after the replacement of the control station is completed, the original control station stops its function.

  FIG. 9 is a sequence diagram showing an operation of PNC handover processing in WPAN. In the example shown in FIG. 9, it is assumed that there are DEV1 as a control station and DEV2 and DEV3 as slave stations.

  First, when DEV1 that wishes to switch control stations selects DEV2 as an appropriate terminal that becomes a new control station (901), DEV1 transmits a control station replacement request command 910 to DEV2. Next, in order to change the control station without interrupting the operation of the piconet, information necessary for piconet management such as a terminal information notification 911, a bandwidth allocation information notification 912, and a power management information notification 913 related to the piconet is provided. Transmit to DEV2.

  When the preparation for accepting that DEV2 having received all the piconet management information becomes a control station is completed (902), a control station replacement acceptance command 914 is transmitted to DEV1. As a result, when DEV1 receives the control station replacement acceptance command 914, “a control station replacement occurs”, “a new control station is DEV2,” “ The timing at which control station replacement occurs is arranged as information, and is notified to all terminals in the piconet.

  Therefore, when DEV3 receives this beacon frame 915, it can be detected that the control station is switched (903). Thereafter, until the control station replacement time (904), DEV1 continues to periodically transmit the beacon frame 915 as a control station, and after the control station replacement occurs, DEV2 that newly becomes the control station transmits the beacon frame 916. Take over.

  The above-described piconet generation process, subordinate piconet function, control station replacement process, etc. allow the WPAN system equipment to autonomously construct an optimal wireless network topology for the application and dynamically re-activate it in response to changes in usage patterns. It is a function necessary for construction. In this way, in a WPAN communication system equipped with an autonomous network topology configuration function between devices, optimal configuration of the topology is important for efficient data communication. No specific algorithm for efficiently constructing an optimal topology using these WPAN functions has been provided.

  FIG. 10 is a diagram showing a topology change in the WPAN system when a control station change occurs. In FIG. 10, consider a case where the control station is switched from the first terminal 1001 serving as the control station to the second terminal 1002.

  When the control station is switched from the first terminal 1001 to the second terminal 1002 in accordance with the PNC handover process, the communication area of the piconet changes from the old piconet 1010 to the new piconet 1020 in FIG. As a result, the fourth terminal 1004 leaves the new piconet cover area 1020. Here, the fourth terminal 1004 that has left the piconet scans a frequency channel that can be used in accordance with the piconet generation sequence already described with reference to FIG. 5 in order to detect whether or not there is a piconet in the vicinity. .

  However, since the fourth terminal 1004 cannot receive the beacon frame transmitted by the second terminal 1002 which is a new control station, the fourth terminal 1004 determines that there is no piconet in which it can participate after scanning for a certain period of time. As a control station, an independent piconet 1030 different from the new piconet 1020 is generated.

  In such a case, since the piconet 1020 and the piconet 1030 operate independently and asynchronously, if the third terminal 1003 exists at a position where the cover areas of both the piconet overlap, the third terminal 1003 There is a possibility that frames transmitted from two piconets collide.

  Therefore, a technique for reconstructing an optimal network topology is required in WPAN in the case where the control station is switched as shown in FIG.

Thus, as a technique for reconfiguring a communication network in which a terminal station newly becomes a control station in a wireless communication system, for example, Patent Document 1 is cited. Patent Document 1 discloses a configuration in which a sub-master station controls a network on behalf of a master station when the master station is abnormal. Patent Document 2 shows that another station that cannot receive the beacon signal from the master base station operates as a new master station.
Japanese Patent Laid-Open No. 6-104979 JP-A-8-139723

  However, in the above-described conventional WPAN communication system, when a control station is switched, a child station that leaves the coverage area of the new control station autonomously generates a new second independent piconet. Therefore, there is a problem that data packets transmitted asynchronously from the first and second independent piconets collide with each other, and the throughput of data transmission in the WPAN network decreases.

  The present invention has been made in order to solve the above-described problems. When a control station is switched and there is a slave station that has left the coverage area of a new control station, packet collision between networks does not occur. The objective is to quickly construct a network with an optimal topology.

  The present invention is a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station, and another wireless terminal device participates in the network as a slave station, and determines the replacement of the control station And a generation unit that generates a subordinate network subordinate to the new network in response to the determination by the determination unit, and participates in the subordinate network. When a slave station exists, the slave station that generated the subordinate network operates as a control station of the subordinate network.

  The present invention is also a wireless terminal device in a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station, Determining means for determining replacement of the control station; and generating means for generating a subordinate network in which a child station of the new network generated by the new control station is subordinate to the new network in accordance with the determination by the determining means; When there are slave stations participating in the subordinate network, the substation network operates as a control station of the subordinate network.

  Furthermore, the present invention is a network generation method of a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station, When a control station switches to a new control station, a child station of the new network generated by the new control station generates a subordinate network subordinate to the new network, and there are substations participating in the subordinate network The slave station that generates the subordinate network operates as a control station of the subordinate network.

  The present invention is also a network generation method for a wireless terminal device in a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station. When the control station is replaced with a new control station, a subordinate network subordinate to the new network generated by the new control station is generated, and when there are slave stations participating in the subordinate network, It operates as a network control station.

  According to the present invention, when a change of a control station occurs and there is a child station that has left the coverage area of a new control station, a network having an appropriate topology that does not cause a packet collision between networks can be quickly established. By configuring, it is possible to prevent a situation in which data transfer is interrupted, and to maintain good data transfer throughput in the network.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. Note that the wireless terminal device in this embodiment may be any device that operates as a WPAN device having a PNC function, and is a terminal device such as a computer device, a digital camera, a digital video camera, a printer, or a mobile phone.

  FIG. 1 is a diagram illustrating an example of a configuration of a piconet in the first embodiment. As shown in FIG. 1, the initial piconet is composed of terminals 101-104. Here, it is assumed that the first terminal 101 currently operates as a control station, and the second terminal 102 takes over the role of the control station from the first terminal 101 by PNC handover.

  In this state, when a PNC handover occurs from the first terminal 101 to the second terminal 102, the coverage area of the piconet is changed from the old piconet 110 having the first terminal 101 as a control station to the new terminal 102. The cover area changes to a new piconet 120 serving as a control station.

  FIG. 2 is a sequence diagram illustrating operations of the terminals 101 to 104 according to the first embodiment. First, it is assumed that a data stream has already been established between the third terminal 103 and the fourth terminal 104, and data transmission 210 is being performed between these two terminals 103 and 104.

  In accordance with the normal PNC handover procedure described above, the first terminal 101 which is the current control station transmits a control station replacement request command 211 to the second terminal 102 to which the role of the control station is transferred. When the second terminal 102 accepts the replacement request, the second terminal 102 responds by transmitting a control station replacement acceptance command 212 to the first terminal 101.

  The first terminal 101 that has accepted the transfer of the control station has a control station change in the beacon frame 213 transmitted by itself, the new control station is the second terminal 102, and Timing information at the time when the switching of the control station occurs is arranged as data, and is notified to all the terminals 102 to 104 in the piconet. Thereafter, the control station is switched between the first terminal 101 and the second terminal 102 at the notified timing (201).

  Thus, after the function of the control station is transferred from the first terminal 101 to the second terminal 102, the first terminal 101 turns off the power and leaves the piconet 110 (202). On the other hand, the second terminal 102 becomes a new control station and starts transmitting the beacon frame 214. Thereafter, all the beacon frames 214 that control the operation of the new piconet 120 are transmitted by the second terminal 102 that has newly become a control station.

  At this point, as shown in FIG. 1, third terminal 103 stays within the coverage area of new piconet 120, but fourth terminal 104 leaves the coverage area of new piconet 120. That is, the third terminal 103 can receive the beacon frame 214 transmitted from the second terminal 102 (203), but the fourth terminal 104 cannot receive the beacon frame 214 (204).

  The first embodiment is characterized in that, at this point, the third terminal 103 requests the second terminal 102, which is a new control station, to generate a dependent piconet. Specifically, when the third terminal 103 transmits a dependent piconet generation request command 215 to the second terminal 102 which is a new control station, and the second terminal 102 acknowledges this, the second terminal 102 It responds by transmitting a dependent piconet generation permission command 216 to the third terminal 103, and further assigns a time slot (bandwidth assignment) that can be used by the dependent piconet.

  The third terminal 103 permitted to generate the dependent piconet (205) thereafter periodically transmits a beacon frame 217 for controlling the dependent piconet. Before the change of the control station, the third terminal 103 and the fourth terminal 104 performed data communication with each other. At this time, as shown in FIG. 1, the coverage area of the dependent piconet 130 is the fourth terminal. 104 can be accommodated.

  On the other hand, as a result of the switching of the control station, the fourth terminal 104 that has left the cover area of the piconet 120 scans a frequency channel that can be used for a certain period of time in order to search for the existence of a piconet that the user can participate in. (206). In the conventional piconet, since the third terminal 103 does not generate a dependent piconet, the fourth terminal 104 generates a new independent piconet from itself after a predetermined time scan, which is caused by the second terminal 102. This has caused a frame collision with the existing piconet 120.

  However, in the first embodiment, as described above, since the third terminal 103 generates the dependent piconet 130 in the area where the fourth terminal 104 can be accommodated, the fourth terminal 104 searching for the piconet. Can receive the beacon frame 217 from the third terminal 103 (207). As a result, the fourth terminal 104 participates in the subordinate piconet 130 generated by the third terminal 103 (208), and continues the data transmission 218 by the stream established with the third terminal 103. Is possible.

  In the first embodiment, when the control station replacement occurs, if both the third terminal 103 and the fourth terminal 104 remain in the cover area of the new piconet 120, both of them are normally operated after the control station replacement. Therefore, the third terminal 103 that has generated the dependent piconet 130 may perform processing such as terminating the dependent piconet 130 after a certain period of time has elapsed.

  In this case, the criteria for determining whether or not to terminate the dependent piconet 130 include, for example, that the fourth terminal 104 has not left the original piconet 110 and that the dependent piconet 130 generated by the third terminal 103 is newly added. It is possible to make a judgment by using such information.

  As described above, according to the first embodiment, when a control station is switched and a new piconet is generated, a terminal of the new piconet generates a dependent piconet subordinate to the new piconet, thereby performing data transmission. Even when the partner terminal is outside the coverage area of the new piconet, the partner terminal can participate in the subordinate piconet and data transmission can be continued.

  Next, Embodiment 2 according to the present invention will be described in detail with reference to the drawings. The network configuration of the piconet in the second embodiment is the same as that shown in FIG. 1 used in the first embodiment.

  The third terminal 103 and the fourth terminal 104 in the second embodiment intercept data transmission between the first terminal 101 and the second terminal 102 in advance, and the second terminal 102 that becomes a new control station. It is characterized by having a step of determining whether or not the local station can receive the transmission signal from the mobile station.

  As shown in FIG. 6, in the TDMA access protocol used in WPAN, a transmission terminal (Source) and a reception terminal (Destination) that perform data transmission using each time slot are designated in advance. Also, these time slot usage information is held as time slot information in the beacon frame transmitted from the control station, and each terminal is the time slot that the local station may transmit based on this information. Or, it is determined where the time slot that the local station has to intercept and the TDMA protocol is executed.

  In normal operation, a terminal station that is not specified as a transmission source or a transmission destination in each time slot enters a power saving mode during the time slot period, thereby suppressing unnecessary wireless module operations and reducing battery life. It can also be increased.

  However, by intercepting communications in these time slots, it is also possible to use this history as a reference for determining whether or not the local station can receive transmission signals from other terminals. By using this, Example 2 has a greater effect.

  FIG. 3 is a sequence diagram illustrating operations of the terminals 101 to 104 according to the second embodiment. As shown in FIG. 3, it is assumed that the third terminal 103 and the fourth terminal 104 perform data transmission 310, and that the first terminal 101 and the second terminal 102 also perform data transmission 311. . At this time, if the third terminal 103 and the fourth terminal 104 intercept a time slot in which the source terminal is designated as the second terminal 102 and the destination terminal is designated as the first terminal 101, the source terminal becomes the source. It is assumed that the third terminal 103 can receive the transmission frame from the second terminal 102, but the fourth terminal 104 cannot receive the transmission frame. Further, the third terminal 103 and the fourth terminal 104 store the result of intercepting the transmission frame from the second terminal 102 as a history (303).

  Thereafter, as in the first embodiment, the control station is switched between the first terminal 101 and the second terminal 102 in accordance with a normal PNC handover procedure (control station replacement request command 312 and control station replacement acceptance command 313). Occurs, the third terminal 103 and the fourth terminal 104 that have received the beacon frame 314 from the first terminal 101, which is the current control station, determine the new control station from the information held in the beacon frame 314. 2 is detected. Then, the third terminal 103 can determine that the own station is included in the coverage area of the second terminal 102 from the result of intercepting the stored transmission frame from the second terminal 102, Further, the fourth terminal 104 can determine from the result of intercepting the stored transmission frame from the second terminal 102 that its own station has left the coverage area of the second terminal 102. (304).

  As in the first embodiment, the control station is switched between the first terminal 101 and the second terminal 102 (301). When the first terminal 101 leaves the piconet 110 (302), The third terminal 103 promptly generates a dependent piconet by the dependent piconet generation request command 315 and the dependent piconet generation permission command 316 (305). Further, the fourth terminal 104 also immediately starts the scan process (306) after the control station change, and when receiving the beacon frame 317 transmitted by the third terminal 103, it can join the subordinate piconet (307), It is possible to continue the data transmission 318 using the stream established with the terminal 103.

  As described above, according to the second embodiment, transmission frames from other terminals are stored as a history, and when a change of the control station occurs, a dependent piconet is generated based on the history, whereby data The partner terminal during transmission can join the subordinate piconet and data transmission can be continued.

  Next, Embodiment 3 according to the present invention will be described in detail with reference to the drawings. The network configuration of the piconet in the third embodiment is the same as that shown in FIG. 1 used in the first embodiment.

  FIG. 4 is a sequence diagram illustrating operations of the terminals 101 to 104 according to the third embodiment. First, it is assumed that a data stream has already been established between the third terminal 103 and the fourth terminal 104, and data transmission 420 is being performed between these two terminals.

  Further, data transmission 421 is also executed between the first terminal 101 and the second terminal 102, and the time slot in the data transmission 421 is set to the third terminal 103 and the fourth terminal similarly to the second embodiment. By intercepting the terminal 104, the third terminal 103 recognizes that it is within the coverage area of the second terminal 102, and the fourth terminal 104 recognizes that it is outside the coverage area of the second terminal 102 ( 403).

  Thereafter, as in the first embodiment, the control station is switched between the first terminal 101 and the second terminal 102 in accordance with a normal PNC handover procedure (control station replacement request command 422 and control station replacement acceptance command 423). When the first terminal 101 that has accepted the transfer of the control station occurs, the change of the control station occurs in the beacon frame 424 transmitted by itself, and the new control station becomes the second terminal 102. That is, the timing information at the time when the switching of the control station occurs is arranged as data and notified to all terminals in the piconet.

  At this time, when it is detected from the content of the beacon frame 424 that the fourth terminal 104 leaves the coverage area of the second terminal 102 which becomes a new control station (404), the third data communication partner is the third data communication partner. In order to notify the terminal 103 that he / she has left the new piconet, a leave notification command 425 is transmitted.

  On the other hand, as a result of receiving the beacon frame 424, the third terminal 103 detects that it stays in the cover area of the new piconet (404), and from the fourth terminal 104, which is a data communication partner for stream communication, When the withdrawal notification command 425 is received, the withdrawal of the communication partner is detected (405).

  Here, the change of the control station occurs (401), the first terminal 101 leaves the piconet 110 (402), and the beacon frame 426 from the second terminal 102, which is a new control station, is transmitted to the third terminal 103. Receive. At this time, when the third terminal 103 transmits a dependent piconet generation request 427 to the second terminal 102 and receives the dependent piconet generation permission command 428, the third terminal 103 starts transmitting its own beacon frame 429, Generate a dependent piconet.

  On the other hand, when the fourth terminal 104 receives this beacon frame 429 during the scanning process (408), it joins the subordinate piconet generated by the third terminal 103 (410). Thereby, since the data transmission 430 between the third terminal 103 and the fourth terminal 104 is restored, the stream transmitted between these two terminal devices can be continuously communicated without interruption.

  As described above, according to the third embodiment, when a change of the control station occurs, if the counterpart terminal that is transmitting data leaves the new piconet, the attribute piconet is generated by the withdrawal notification from the counterpart terminal. The partner terminal can participate in the subordinate piconet and data transmission can be continued.

  In the above-described embodiment, the case where one terminal is outside the cover area of the new control station has been described as an example. However, it goes without saying that the present invention can also be applied when a plurality of terminals are outside the cover area. Yes. In that case, a plurality of subordinate piconets are generated and the respective data transmissions can be continued.

  Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it can be applied to a device composed of a single device (for example, a copier, a facsimile machine, etc.). May be.

  Another object of the present invention is to supply a recording medium that records software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus uses the recording medium as a recording medium. Needless to say, this can also be achieved by reading and executing the stored program code.

  In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium storing the program code constitutes the present invention.

  As a recording medium for supplying the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like is used. be able to.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

FIG. 3 is a diagram illustrating an example of a configuration of a piconet in the first embodiment. FIG. 6 is a sequence diagram illustrating operations of terminals 101 to 104 according to the first embodiment. It is a sequence diagram which shows operation | movement of the terminals 101-104 in Example 2. FIG. It is a sequence diagram which shows operation | movement of the terminals 101-104 in Example 3. FIG. It is a sequence diagram showing the production | generation procedure of the piconet in WPAN. It is a figure for demonstrating the principle of the TDMA access system in WPAN. It is a figure which shows the relationship between a parent piconet and a subordinate piconet. It is a figure which shows the operation timing of a parent piconet and a subordinate piconet. It is a sequence diagram which shows the operation | movement of the PNC handover process in WPAN. It is a figure which shows the topology change in a WPAN system when the replacement of a control station occurs.

Explanation of symbols

101 First terminal (DEV1)
102 Second terminal (DEV2)
103 Third terminal (DEV3)
104 Fourth terminal (DEV4)
110 piconet 120 new piconet 130 subordinate piconet

Claims (9)

A wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station,
Determining means for determining replacement of the control station;
Generating means for generating a subordinate network in which a slave station of the new network generated by the new control station is subordinate to the new network in accordance with the determination by the determining means;
A wireless communication system, wherein when there is a slave station participating in the subordinate network, the substation generating the subordinate network operates as a control station of the subordinate network.   The wireless communication according to claim 1, wherein the slave station that has generated the subordinate network terminates the subordinate network if no substation participates in the subordinate network while a predetermined time elapses. system. A wireless terminal device in a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station,
Determining means for determining replacement of the control station;
Generating means for generating a subordinate network subordinate to the new network generated by the new control station according to the determination by the determining means;
A radio terminal apparatus that operates as a control station of the subordinate network when there are slave stations participating in the subordinate network.   4. The wireless terminal device according to claim 3, wherein when there is no slave station participating in the subordinate network during a predetermined time, the subordinate network is terminated. A network generation method for a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station,
When the control station is replaced with a new control station, a slave station of the new network generated by the new control station generates a subordinate network subordinate to the new network;
A network generation method of a wireless communication system, wherein a child station that has generated the subordinate network operates as a control station of the subordinate network when there is a substation participating in the subordinate network. A wireless terminal device network generation method in a wireless communication system in which one of a plurality of wireless terminal devices generates a network as a control station and another wireless terminal device participates in the network as a slave station,
When the control station is replaced with a new control station, generate a subordinate network subordinate to the new network generated by the new control station;
A method for generating a network of a wireless terminal device, wherein when there are slave stations participating in the subordinate network, the substation network operates as a control station of the subordinate network.   A program for causing a computer to execute the network generation method of the wireless communication system according to claim 5.   A non-transitory computer-readable storage medium storing a program for causing a computer to execute the wireless terminal device network generation method according to claim 6.   A computer-readable recording medium on which the program according to claim 7 or 8 is recorded.

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