Electronic device having communication function

Technical Field

0001The present invention relates to a communication processing apparatus, a communication processing system and a communication processing method, and also to a computer program. More particularly, the invention relates to a communication processing apparatus, a communication processing system, a communication processing method and a computer program which can easily and quickly switch a master device that functions as a communication routing device or a control device for use in wireless communication represented by, for example, Bluetooth®.

0002This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2002-292333, filed October 4, 2002, the entire contents of which are incorporated herein by reference.

Background Art

0003Bluetooth has been attracting attention as means for achieving short-distance wireless communication. Various devices compliant with Bluetooth have been developed and on the market.

0004Systems for wireless communication by means of Bluetooth have no directivity and high transmissivity. They are therefore advantages over the conventional infrared communication system such as IrDA (Infrared Data Association). To use high-directivity communication by means of, for example, IrDA, the devices between which to accomplished communication should be appropriately positioned to face each other. Such positioning is unnecessary in any communication system that employs Bluetooth.

0005Bluetooth SIG Inc. controls the standards of Bluetooth. The details of the standards are available to any person. In any communication utilizing Bluetooth, a device called "master" that controls the communication transmits, by broadcasting, a device detection message for detecting the devices that exist around the master.

0006The master can detect any device (slave) that exists around it and has received the device-detecting message, when it receives a response message transmitted from the device that can communicate with it.

0007To establish communication with the device thus detected, the master identifies the device on the basis of the ID information that is contained in the response message. The communication with this device is thereby established.

0008In Bluetooth, each device is assigned with ID information called "Bluetooth-device address," which is used to identify the device. Since the ID information is unique to the device, it is utilized in various processes such as the management of the device.

0009In Bluetooth, a network composed of a master and slaves is called "piconets." In the piconet, up to seven slaves can belong to one master. All devices of the piconet are synchronized in terms of frequency axis (frequency hopping pattern) and time axis (time slot).

0010A plurality of piconets may be connected to one another, thus constituting a larger network, which is called "scatter net."

0011In Bluetooth, specification which is called "profile" is defined for each service item, in connection with the data to be transmitted and received by wireless communication and the procedure of wireless communication. The service that each device can provide is described according to the profile.

0012PAN (Personal Area Network) profile describes the method of communication between the slaves of a piconet. Any device of the piconet configured on the basis of the PAN profile can transmit and receive various data items in the piconet, which is one network. It is planned that, in a scatter net, too, any device can transmit and receive various data items because the scatter net is also a network. This network can be a network based on IP (Internet Protocol).

0013In the process of constructing such a network, it is necessary to determine which device should be the master, which device should be a slave, and which service should be used to achieve communication. It is the master that determines these, by acquiring the information about the devices existing around it, from the above-mentioned response message or the like, and in accordance with the instructions of the user.

0014When the master is removed from the piconet, the slaves can no longer communicate with one another through the master in the piconet. The communication must be stopped, and it is necessary to set one of the slaves as master, thereby constructing a new piconet.

0015At present, one of the devices is not automatically set as master. It needs to be set as such manually by the user. Hence, the user is bothered to set a new master when the piconet ceases to exist due to the removal of the master from the network, the power running-out of the master battery, or the like. Unless the user set a slave as new master, no communication can be accomplished between the other slaves in the network. The communication may be interrupted for a long time.

Disclosure of Invention

0016An object of the present invention is to provide a novel communication processing apparatus, communication processing system and communication processing method that can solve the problems of the prior art described above, and also to provide a computer program.

0017Another object of the invention is to provide a communication processing apparatus, a communication processing system and a communication processing method, in which a new master can be set immediately after the master is removed from a piconet, thereby reducing to a minimum the interruption of communication between the devices that constitute the piconet, and also to provide a computer program.

0018Still another object of the present invention is to provide a communication processing apparatus, a communication processing system and a communication processing method, and also to provide a computer program. In the apparatus, system and method, the master evaluates a slave for its aptitude for use as master, on the basis of the performance parameter supplied from the slave, selects the slave having the highest possibility, as next master, i.e., backup master, and transmits the information of the backup master to every slave. Thus, when the master is removed from the piconet, the slaves can be connected to the backup master immediately, thereby resuming the communication in the piconet.

0019To attain the objects described above, a communication processing apparatus according to the present invention acts as a master in a wireless communication network that comprises at least one slave which communicates through the master. The apparatus is characterized by having: a data-receiving means for receiving data from each of the slaves that are devices constituting the wireless communication network, wherein capabilities of data processing for each item of evaluation are set as performance parameters in the data; a data-processing means for performing a process of figuring out aptitude for a master based on the performance parameters received from the slave and a process of determining one slave as a backup master that is a candidate for next master based on the aptitude; and a data-transmitting means for transmitting backup-master information containing address information and synchronization information, to each slave of the wireless communication network, the address information corresponding to the backup master determined by the data-processing means.

0020In the communication processing apparatus according to this invention, the performance parameters include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity, all pertaining to the slave, and the data-processing means is configured to figure out the mater aptitude based on at least one of the performance parameters.

0021In the communication processing apparatus according to the invention, the performance parameters may include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity, all pertaining to the slave, and the data-processing means may be configured to figure out the mater aptitude by performing an operation in which a weight coefficient is applied to at least one of the performance parameters.

0022In the communication processing apparatus according to the invention, the performance parameters may include a data item representing whether the slave can be a master, and the data-processing means may be configured to figure out the master aptitude only for the slave whose data item represents to be a master.

0023In the communication processing apparatus according to this invention, the wireless communication network is a wireless communication network that performs Bluetooth communication, and the data-receiving means may be configured to perform a process of receiving packets, each being a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP) and containing the performance parameters.

0024In communication processing apparatus according to the present invention, the wireless communication network is a wireless communication network that performs Bluetooth communication, and the data-transmitting means is configured to perform a process of transmitting packets, each being a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP) and containing the backup-master information.

0025In the communication processing apparatus according to this invention, the performance parameters are stored in a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP), and the data-processing means may be configured to perform a process of acquiring the performance parameters from the BNEP packets.

0026In the communication processing apparatus according to the invention, the data-processing means may be configured to perform a process of storing the backup-master information in a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP). The backup-master information includes address information corresponding to the backup master and synchronization information.

0027In the communication processing apparatus according to the invention, the data-processing means further generates a backup-master activation request packet that requests for activation of the backup master, and the data-transmitting means may be configured to perform a process of transmitting the backup-master activation request packet to the backup master.

0028In the communication processing apparatus according to this invention, the data-processing means may be configured to perform a process of storing type information (Target UUID) in the backup-master activation request packet, the type information showing whether the master should be set as a NAP (Network Access Point) or a GN (Group Ad-hoc Network).

0029In the communication processing apparatus according to the invention, the data-processing means may figure out master aptitudes for the slaves, based on the performance parameters received from the slaves, and generates a packet containing a list that contains the address information items of the slaves and synchronization information, the list showing the address information items in the order of the master aptitudes of the respective slaves, and the data-transmitting means is configured to perform a process of transmitting the packet containing the list, to the slaves constituting the wireless communication network.

0030In the communication processing apparatus according to the present invention, the data-processing means further generates a packet to be transmitted to the backup master, the packet containing a list that contains address information of the slaves that are devices constituting the wireless communication network and synchronization information, and the data-transmitting means may be configured to perform a process of transmitting the packet containing the list, to the backup master.

0031Another communication processing apparatus according to this invention acts as a slave in a wireless communication network that comprises a master which controls communication and at least one slave which communicates through the master. This apparatus is characterized by having: a data-processing means for generating a packet containing data set as performance parameters that are the performance values obtained of each slave; a data-transmitting means for transmitting the packet generated by the data-processing means, to the master; a data-receiving means for receiving backup-master information from the master, the backup-master information including address information corresponding to a backup master and synchronization information; a memory means for storing the backup-master information received by the data-receiving means; and a connection control means for performing a process of connecting the slaves to the backup master in accordance with the backup-master information stored in the memory means.

0032In this communication processing apparatus, the data-processing means is configured to generate a packet that contains data containing performance parameters of each slave. The performance parameters include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity.

0033In the communication processing apparatus according to the invention, the data-processing means is configured to set values for the performance parameters that are data-processing performance items evaluated of each slave, in accordance with reference values set in common in the wireless communication network.

0034In the communication processing apparatus according to this invention, the data-processing means may be configured to generate a packet storing data in which performance parameters are set. The performance parameters include a data item representing whether the slave can be set as master.

0035In the communication processing apparatus according to the present invention, the wireless communication network is a wireless communication network that performs Bluetooth communication, and the data-receiving means may be configured to perform a process of generating packets, each being a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP) and containing the performance parameters.

0036In the communication processing apparatus according to the invention, the data-processing means may be configured to perform a process of storing the performance parameters in a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP).

0037In the communication processing apparatus according to this invention, the backup-master information is information containing a list that contains address information of a plurality of devices and synchronization information, the devices being candidates for backup master, and the connection control means may perform a process of connecting the slaves to the backup master, in the order described in the list.

0038A communication processing system according to the present invention functions in a wireless communication network that comprises a master which controls communication and at least one slave which communicates through the master. The system is characterized by comprising: a master which sets a backup master as a candidate for next master, on the basis of data containing performance parameters that are data-processing performance items evaluated of each slave, and which supplies backup-master information about the backup master to each slave; and slaves which perform a process of figuring out data-processing performance items evaluated of each slave in the form of performance parameters and transmitting to the master, and which performs a process of receiving the backup-master information from the master and storing the backup-master information in a memory means. Each of the slaves is configured to determine the next master on the basis of the backup-master information after disconnected from the master, and to perform a connection process thereafter.

0039In the communication processing system according to this invention, the performance parameters include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity, all pertaining to the slave, and the master is configured to figure out a mater aptitude based on at least one of the performance parameters transmitted from each slave.

0040In the communication processing system according to the invention, the performance parameters include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity, all pertaining to the slave, and the master may be configured to figure out the mater aptitude by performing an operation in which a weight coefficient is applied to at least one of the performance parameters.

0041In the communication processing system according to the present invention, the master is configured to perform a process of storing the backup-master information in a BNEP packet generated in accordance with Bluetooth network encapsulation protocol (BNEP) and transmitting the BNEP packet to the slaves. The backup-master information includes address information corresponding to the backup master and synchronization information.

0042In the communication processing system according to the invention, the master may be configured to perform a process of transmitting a backup-master activation request packet to the backup master. The backup-master activation request packet requests for activation of the backup master.

0043In the communication processing system according to the present invention, the master may be configured to perform a process of figuring out aptitude for a master based on the performance parameters received from the slave, generating a packet containing a list and transmitting the packet to the slaves. The list contains synchronization information and showing device-address information items in the order set in accordance with the master aptitudes.

0044In the communication processing system according to the invention, the master may be configured to perform a process of generating a packet containing a list and transmitting the packet to the backup master. The list contains synchronization information and address information items of the slaves that are devices constituting the wireless communication network.

0045A master-controlling method according to the present invention is designed for use in a communication processing apparatus which is to act as a master in a wireless communication network that comprises at least one slave which communicates through the master. The method is characterized by having: a data-receiving step of receiving data from each of the slaves that are devices constituting the wireless communication network, wherein capabilities of data processing for each item of evaluation are set as performance parameters in the data; a data-processing step of performing a process of figuring out aptitude for a master based on the performance parameters received from the slave and a process of determining one slave as a backup master that is a candidate for next master based on the master aptitude; and a data-transmitting step of transmitting backup-master information containing address information and synchronization information, to each slave of the wireless communication network, the address information corresponding to the backup master determined by the data-processing means.

0046In the master-controlling method according to the invention, the performance parameters include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity, all pertaining to the slave, and the data-processing step is to figure out the mater aptitude based on at least one of the performance parameters.

0047A master-connection method according to the present invention is designed for use in a communication processing apparatus which is to act as a slave in a wireless communication network that comprises a master which controls communication and at least one slave which communicates through the master. The method is characterized by having: a data-processing step of generating a packet containing data set as performance parameters that are the performance values obtained of each slave; a data-transmitting step of transmitting the packet generated in the data-processing step, to the master; a data-receiving step of receiving backup-master information from the master, the backup-master information including address information corresponding to a backup master and synchronization information; a storing step of storing the backup-master information received in the data-receiving step; and a connection-controlling step of performing a process of connecting the slaves to the backup master in accordance with the backup-master information stored in the storing step.

0048In the master-connection method according to this invention, the data-processing step is to generate a packet that contains data containing performance parameters of each slave. The performance parameters include at least one of data items of remaining battery power, CPU performance, memory resource and RSSI, i.e., electric-field intensity, all pertaining to the slave.

0049A computer program according to the present invention is designed to control a communication processing apparatus which is to act as a master in a wireless communication network that comprises at least one slave which communicates through the master. The computer program is characterized by describing: a data-receiving step of receiving data from each of the slaves that are devices constituting the wireless communication network, wherein capabilities of data processing for each item of evaluation are set as performance parameters in the data; a data-processing step of performing a process of figuring out aptitude for a master based on the performance parameters received from the slave and a process of determining one slave as a backup master that is a candidate for next master based on the master aptitude; and a data-transmitting step of transmitting backup-master information containing address information and synchronization information, to each slave of the wireless communication network. The address information corresponds to the backup master determined in the data-processing step.

0050Another computer program according to this invention is designed to perform a process of connecting a communication processing apparatus which is to act as a slave in a wireless communication network that comprises a master which controls communication and at least one slave which communicates through the master. This program is characterized by describing: a data-processing step of generating a packet containing data set as performance parameters that are the performance values obtained of each slave; a data-transmitting step of transmitting the packet generated in the data-processing step, to the master; a data-receiving step of receiving backup-master information from the master, the backup-master information including address information corresponding to a backup master and synchronization information; a storing step of storing the backup-master information received in the data-receiving step; and a connection-controlling step of performing a process of connecting the slaves to the backup master in accordance with the backup-master information stored in the storing step.

0051The present invention concerns a wireless communication network comprising a master that performs a communication control process and at least one slave that performs communication via the master. In the network, each slave figures out performance parameters that are its performance values and transmits the performance parameters to the master. The master selects a backup master as a candidate for the next master, on the basis of the performance parameters transmitted from the slave. The master then performs a process of supplying backup-master information containing synchronization information and the address of the backup master selected. Hence, each slave can determine the next master from the backup-master information, even if the master is removed from the network. Thus, the slave can be immediately connected to the next master, and the user need not select a backup master. This shortens the interruption of communication between the slaves and make it possible to connect the slaves to the new master efficiently.

0052In the present invention, the performance parameters are the data-processing performance items evaluated of each slave, such as the remaining battery power, CPU performance, memory resource and RSSI (electric-field intensity). On the basis of these information items the master can select a slave as backup master, which can cope with the operating condition of the network.

0053According to the invention, the backup-master information the master sends to the slaves contains the synchronization information about the backup master. Therefore, at least a part of the process of establishing synchronization necessary for the reconstruction of the network need not be carried out. This makes it possible to reconstruct the network efficiently within a short time.

0054In the present invention, backup-master information that is a list showing devices in the descending order of their master aptitudes may be transmitted to the slaves. Then, the slaves can have information about a plurality of backup masters. Namely, each slave can acquire the information of the other devices that constitute the piconet. Thus, if any slave cannot be connected to the backup master having the highest master aptitude when the master is removed from the piconet, because the backup master has been already removed from the piconet, it may be connected to the backup mater that has the second highest master aptitude.

0055According to the invention, a slave list may be transmitted the backup master. Then, in accordance with the slave list, the device selected as new master can be connected to the slaves, one after another, after the master is disconnected from the slaves. Each slave need not perform any process to connect it to the master. The device selected as new master can use the Bluetooth-device addresses (BD ADDRs) contained in the slave list and also the synchronization information, all transmitted from the previous master. The new master can therefore efficiently establish connection with the slaves. In the piconet thus set anew, the slaves can communicate with one another through the new master.

0056The computer program according to the invention can be provided as data that can be read by general-purpose computer systems that can execute various programs. The program can be provided in the form of a recording medium such as a CD, an FD or an MO or via a communication medium such as a network. Once a computer system has read this program, it can carry out processes described in the program.

0057The system implementing this invention is a logical assembly of various components. All components of the system are not necessarily arranged within the same housing.

0058The other objects of the invention and the advantages achieved by the invention will be more apparent from the embodiments that will be described below with reference to the accompanying drawings.

Brief Description of Drawings

0059<ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 is a diagram showing an example of a network that implements communication that uses Bluetooth;</li><li>FIG. 2 is a diagram illustrating a Bluetooth module;</li><li>FIG. 3 is a diagram explaining a Bluetooth-device address;</li><li>FIG. 4 is a diagram explaining a communication processing apparatus that has the Bluetooth module;</li><li>FIG. 5 is a diagram depicting the process sequence of setting up a piconet that comprises a device A set as master and devices B to G used as slaves;</li><li>FIG. 6A and FIG. 6B are diagrams explaining a BNEP packet;</li><li>FIG. 7 is a diagram representing the format of an expansion header to be set in the BNEP packet;</li><li>FIG. 8 is a diagram showing examples of performance parameters that the slaves may transmit to the master;</li><li>FIG. 9A is a diagram depicting an expansion type for the expansion header set in a packet to be transmitted, the header containing performance parameters, and FIG. 9B is a diagram showing a payload;</li><li>FIG. 10 is a diagram showing a list of backup masters (BMs) which may be selected, each in accordance with its master aptitude based on performance parameters;</li><li>FIG. 11 is a diagram representing the process sequence, starting with the transmission of backup-master (BM) information from the master to a slave, and ending with the use of a backup master as master;</li><li>FIG. 12A and FIG. 12B are diagrams illustrating an example of a packet of backup-master (BM) information, which is to be transmitted;</li><li>FIG. 13A and FIG. 13B are diagrams illustrating an example of a backup-master activation notice (BM Activation);</li><li>FIG. 14A and FIG. 14B are diagrams illustrating an example of a packet of net trigger notification (NET Trigger), which is to be transmitted;</li><li>FIG. 15 is a diagram depicting the sequence of spontaneously or forcibly disconnecting the slave having the backup-master information from the previous master and then connecting the same to the new master in accordance with the backup-master information;</li><li>FIG. 16 is a flowchart explaining the principle of the process that the master performs to select a backup master and notify the selection thereof;</li><li>FIG. 17 is a flowchart explaining the principle of the process that a slave performs to select a backup master and notify the selection thereof;</li><li>FIG. 18A and FIG. 18B are diagrams illustrating an example of a packet to be transmitted, which is a BNEP packet containing a list of backup-master (BM) information items;</li><li>FIG. 19 is a diagram representing the process sequence in which a backup master is connected to each slave in accordance with a list; and</li><li>FIG. 20A and FIG. 20B are diagrams illustrating an example of a BNEP packet to be transmitted, which contains a slave list.</li></ul>

Best Mode for Carrying out the Invention

0060A communication processing apparatus, a communication processing system, a communication processing method, and a computer program, all according to this invention, will be described in detail with reference to the accompanying drawings.

0061A communication system will be first described with reference to FIG. 1. The system comprises a piconet that is a wireless communication network based on Bluetooth standards. In the system, various types of data are exchanged between the communication processing apparatuses that constitute the piconet.

0062As described above, the communication using Bluetooth is carried out in a network (piconet) that comprises a device called master, which controls the communication, and a plurality of devices called slaves, which receive and transmit data through the master. In accordance with Bluetooth, Bluetooth-device addresses are allocated to the devices, each identifying one device. Any device that is to transmit or receive data is identified with the Bluetooth-device address.

0063The piconet comprising a master and slaves can have up to seven slaves for the master. All devices belonging to the piconet are synchronized in terms of frequency axis (frequency hopping pattern) and time axis (time slot).

0064FIG. 1 shows a piconet that comprises a personal computer (PC) 101 used as master and some other devices used as slaves, i.e., a personal computer (PC) 121, a mobile telephone 122, a PDA (Personal Digital Assistant) 123 and a video camera 124.

0065The piconet comprising one master and a plurality of slaves can be used as an independent network not connected to any external network (in ad-hoc mode). Alternatively, it can be connected to any other network, such as the Internet or other piconets, via the master (in infrastructure mode).

0066The piconet is called "personal area network (PAN)." Each slave is called "PANU (PAN user)." The piconet may be connected to an external network (in infrastructure mode). In this case, the master makes routing of communication packets between the slaves of the piconet, thus accomplishing packet exchange between the slaves, and also exchanges packets with the external network. Thus, the master is called "NAP (Network Access Point)." The piconet may not be connected to any external network (in ad-hoc mode). If this is the case, the master makes routing of communication packets between the slaves of the piconet. Thus, it is called "GN (Group Ad-hoc Network)."

0067Bluetooth defines specification known as "profile," for any data to be transmitted or received by wireless communication, and for the procedure of wireless communication. The profile describes the service that each device can provide. The PAN (Personal Area Network) profile describes a method of achieving communication between the slaves of a piconet. The devices belonging to the piconet constituted on the basis of the PAN profile can transmit and receive various types of data, using the piconet as a network.

0068The personal computer (PC) 101, personal computer (PC) 121 as a slave, mobile telephone 122, PDA (Personal Digital Assistant) 123 and video camera 124, all shown in FIG. 1, incorporate a Bluetooth module each. They can transmit and receive various data items to and from one another, by means of wireless communication based on the Bluetooth standards.

0069The devices, i.e., the master and the slaves, have a Bluetooth module that carries out wireless communication based on the Bluetooth standards. More specifically, the module adopts a time-division multiplex system that uses a 2.4-GHz ISM band to perform wireless communication by means of frequency hopping spectrum diffusion in the ISM band.

0070The configuration of the Bluetooth module will be described, with reference to FIG. 2. A CPU 201 loads the control program stored in a ROM 202 into a RAM 203 and then controls a Bluetooth module 200 as a whole. The CPU 201 functions as a data-processing means or a communication control means. The CPU 201 to the RAM 203 are connected to one another by a bus 205. To the bus 205, there is connected a flash memory 204.

0071The flash memory 204 stores, for example, the names of the Bluetooth devices set as master and slaves in the piconet, the Bluetooth-device addresses unique to the Bluetooth devices, and the like.

0072The Bluetooth-device addresses are 48-bit indentifiers, each being specific, or unique, to one Bluetooth device. Hence, they are used in various processes relating to the management of the Bluetooth devices.

0073To establish the devices synchronous in the piconet, for example, all slaves must have acquired the information about the frequency-hopping pattern of the master. Each slave figures out the frequency-hopping pattern beforehand, on the basis of the Bluetooth-device address of the master.

0074To be more specific, a Bluetooth-device address consists of a 24-bit low-address part (LAP), an 8-bit upper-address part (UAP), and a 16-bit non-significant address part (NAP), i.e., the remaining 16 bits, as is illustrated in FIG. 3. Twenty-eight (28) bits, i.e., entire LAP (24 bits) and the lowest 4 bits of the UAP, are used to figure out the frequency-hopping pattern.

0075Each slave can figure out a frequency-hopping pattern from the 28-bit part of the Bluetooth-device address of the master and a Bluetooth clock notified by the master. Note that the Bluetooth-device address of the master has been acquired by the paging performed to establish the intra-piconet synchronization.

0076Referring to FTG. 2 again, the flash memory 204 stores a link key and the like. The link key authenticates Bluetooth devices that are to communicate with one another after the intra-piconet synchronization is established, or encrypts the data to be transmitted. The link key is supplied to the CPU 20, whenever necessary.

0077An input/output interface 206 controls the input and output of the data supplied in accordance with the instructions from the CPU 201 and also the input and output of the data supplied from a base-band control unit 207.

0078The base-band control unit 207 performs various controls and various processes. The controls the unit 207 performs includes the control of a transceiver 208, the control of a link, the control of packets, the control of logic channels, and the control of security. The processes the unit 207 performs includes error-correction encoding and decoding and data randomizing. The unit 207 converts the data supplied from the input/output interface 206, into analog data, which is output to the transceiver 208. The unit 207 also converts a signal supplied from the transceiver 208, into digital data. The digital data thus obtained is output to the input/output interface 206.

0079The transceiver 208 comprises a GFSK (Gaussian Frequency Shift Keying) modulation unit, a GFSK demodulation unit, a spectrum-diffusion unit, an inverse spectrum-diffusion unit or a hopping synthesizer unit, and the like. It performs various processes on a signal supplied from the base-band control unit 207 and supplies the signal processed to an antenna 209. It performs various processes on a signal supplied from the antenna 209, too, and outputs the signal processed to the base-band control unit 207.

0080The GFSK modulation unit of the transceiver 208 selects the high-band component of the data supplied from the base-band control unit 207, by using a filter, and performs frequency modulation, or primary modulation, on the high-band component, generating data. The data, thus generated, is output to the spectrum-diffusion unit. The spectrum-diffusion unit switches the carrier frequency on the basis of the frequency-hopping pattern which has been figured out by using 28 bits i.e., entire LAP (24 bits) and the lowest 4 bits of the UAP, as indicated above, and which has been notified from the hopping synthesizer unit. The spectrum-diffusion unit then performs spectrum diffusion on the data it has received, and outputs the data to the antenna 209. In Bluetooth, the spectrum-diffusion unit is designed to cause frequency hopping every 625 microseconds, thereby to transmit data.

0081The inverse spectrum-diffusion unit of the transceiver 208 performs the hopping of the receipt frequency, in accordance with the frequency-hopping pattern notified from the hopping synthesizer unit. Thus, the inverse spectrum-diffusion unit acquires, for example, a signal transmitted from the slave with which the transceiver is communicating. The inverse spectrum-diffusion unit performs inverse spectrum-diffusion on the signal acquired, thus reproducing the signal transmitted from the slave, and output this signal to the GFSK demodulation unit. The GFSK demodulation unit effects GFSK demodulation on the signal supplied from the inverse spectrum-diffusion unit, generating data. The data is output to the base-band control unit 207.

0082The transceiver 208 uses the 2.4-GHz band and transmits the signal that has undergone spectrum diffusion, from the antenna 209. The transceiver 208 outputs the signal received from the antenna 209, to the inverse spectrum-diffusion unit.

0083Each of the communication processing apparatuses that constitute the piconet has a module of the same configuration as the Bluetooth module 200 shown in FIG. 2. Each communication processing apparatus carries out the processes described above, thus accomplishing data communication.

0084The communication processing apparatuses constituting the piconet, i.e., the devices each having a Bluetooth module of the type described above, will be described with reference to FIG. 4. FIG. 4 is a block diagram showing a personal computer that is an example of a communication processing apparatus that acts as master or a slave in the piconet. The configuration shown in FIG. 4 will be explained below.

0085A CPU (Central Processing Unit) 301 performs various processes in accordance with the programs stored in a ROM (Read Only Memory) 302, an HDD 304, or the like. Namely, it works as a data-processing means or a communication control means. A RAM 303 stores, if necessary, the programs and data that the CPU 301 executes and uses. The CPU 301, ROM 302, RAM 303 and HDD 304 are connected to one another by a bus 305.

0086To the bus 305, an input/output interface 306 is connected. To the input/output interface 306 there are connected an input unit 307, an output unit 308, a communication unit 309, and a drive 310. The input unit 307 comprises a keyboard, switches, buttons, and a mouse, which are operated by the user. The output unit 308 comprises an LCD or a CRT, speakers and the like. The communication unit 309 is the Bluetooth module described with reference to FIG. 2 and functions as a means for transmitting and receiving data. The drive 310 can hold a removable recording medium 311, such as a magnetic disc, an optical disc, an opt-magnetic disc, or a semiconductor memory, and can read and write data in and from the removable recording medium 311.

0087Shown in FIG. 4 is a personal computer (PC), which is an example of a communication processing apparatus that may be used as master or a slave in the piconet illustrated in FIG. 1. The communication processing apparatus used as master or a slave in the piconet is not limited to PCs, nevertheless. As seen from FIG. 1, the communication processing apparatus can be a mobile communication terminal such as a mobile telephone or a PDA, a video camera, or any other type of an information-processing apparatus. That is, the device has a unique hardware configuration and carries out processes by using the hardware configuration.

0088As will be detailed below, the communication processing apparatus that works as master in this invention needs to have data-receiving means, a data-processing means, and a data-transmitting means. The data-receiving means receives, from each slave, the data containing performance parameters that represent the data-processing performance items evaluated of the slave. The data-processing means figures out the master aptitude of each slave from the performance parameter it has received from the slave. Based on the master aptitudes thus figured out for all slaves, the data-processing means selects one slave as a backup master, i.e., the next master. The data-transmitting means transmits, to all slaves, the backup-master information containing the address information and synchronization information about the backup master determined by the data-processing means. These components are the hardware items that are illustrated in FIG. 2 and FIG. 4. The processes that the components perform will be explained below in detail.

0089The communication processing apparatus according to the invention, used as a slave, is set as one that comprises a data-processing means, a data-transmitting means, data-receiving means, a memory means and a connection control means. The data-processing means generates a packet containing performance parameters that represent the data-processing performance items evaluated of the slave. The data-transmitting means transmits the packet generated by the data-processing means, to the master. The data-receiving means receives, from the master, backup-master information containing the address information and synchronization information about a device that corresponds to a backup master. The memory means stores the backup-master information that the data-receiving means has received. The connection control means connects the slave to the backup master in accordance with the backup-master information that the memory means has stored. These components are the hardware items that are illustrated in FIG. 2 and FIG. 4. The processes that the components perform will be explained below in detail.

0090In a piconet of the type that comprises one master and a plurality of slaves as is illustrated in FIG. 1, each communication processing apparatus, used as either as master or a slave, performs a sequence of setting a network, as will be described below. The sequence starts with the process of setting one of the slaves set in the piconet, as a backup master (BM), i.e., a candidate for the master, and ends with the process of making the backup master takes over the master function from the master if the master is removed from the network, to control the communication between the slaves belonging to the same piconet.

0091FIG. 5 is a diagram depicting the process sequence of setting up a piconet that comprises a device A set as master and devices B to G used as slaves.

0092First, in Step S 11, the device B functioning as a slave transmits an inquiry by broadcasting. The broadcast transmission of the inquiry is the first-stage process that the master performs to establish the intra-piconet synchronization after determining that slaves exist around it. At this time, however, it is not clear whether a master exists in the piconet. This is why the device B functioning as a slave acts as a provisional master and transmits the inquiry by broadcasting. That is, the inquiry is transmitted by broadcasting, in order to confirm the existence of the master and to acquire the address of the master (i.e., Bluetooth-device address: BD-Address) and also synchronization information transmitted from the master.

0093In Step S12, the device A, which acts as master and which has received the inquiry, supplies its address (i.e., Bluetooth-device address: BD-Address), clock information and the like to the device B. The clock information servers to achieve synchronous communication between the master and any slave.

0094Next, in Step S 13, the device B functioning as a slave performs paging to the device A that is acting as master. The paging is the second-stage process that is performed to establish the intra-piconet synchronization. This process accomplishes synchronization between the master and a specific slave, that is, between the device B and the device A in this instance.

0095"Paging" is a process of first designating a specific Bluetooth device to demand that Bluetooth communication be started, and then transmitting and receiving various data items to establish the synchronization. More precisely, the master and the slave exchange their attribute information items (FHS packets). The master and the slave are rendered synchronous in terms of frequency axis and time axis, on the basis of the attribute information items exchanged.

0096In the piconet, the master and the slave that carry out Bluetooth communication between them have a clock (Bluetooth clock) each. The slave needs to make its clock comply with the clock of the master (i.e., Bluetooth clock). It is paging that causes the clock of the slave to comply with that of the master. The paging is effected in three phases. The first phase is page-transmitting. The second phase is page-scanning. The third phase is page-responding. The paging, thus effected, adjusts the clock of the master and the clock of the slave to each other, establishing the synchronization. At this time, the device B and the device A operate in synchronism, acting as master and a slave, respectively. However, the device A has been set as master. A process is, therefore, performed to cause the devices A and B to operate in synchronism, respectively as master and a slave. This process is called "master-slave conversion."

0097Then, in Step S14, a process is performed between the master (device A) and the slave (device B), which have been made to operate in synchronism, by using SDP (Service Device Protocol). SDP determines service that is effective at this time. SDP is a protocol that searches for the function or service that the master and slave, used as communication processing apparatuses in the piconet, can provide. SDP can therefore determine the service that the master and slave can provide, such as reproduction of music data, access to the network, or the like. Any apparatus that has a Bluetooth module stores, in a database, the information about the service it can offer, reads this service information from the database, and provide the service information.

0098Next, in Step S 15, the process of setting up security is carried out between the master (device A) and the slave (device B). To be more specific, the security setup process is to set a link key that manages the mutual security of the master (device A) and slave (device B). The link key is applied to authenticate the master and the slave, both being Bluetooth devices that communicate with each other, and to encrypt the data to be transmitted or received from and to either Bluetooth device.

0099Hitherto, the above-mentioned sequence of processes is performed between the master and each slave in the piconet, thus achieving inquiring and paging to set a communication environment for the master and each slave. Once the communication environment is so set, SDP determines the service information and sets the link key, thereby establishing security in preparation for the communication between the master and the slave. Thereafter, the master first activates the service when it receives a communication request for the service selected by the slave, and then starts the process of establishing the communication.

0100After the preparation process, the communication is effected in the piconet, through the master. After the use of the service any slave provides is started, the master (device A) may be removed from the network or the power may run out in the battery. In this event, the slaves can no longer communicate with one another via the master. To resume the communication between the slaves, the user needs to set a new master, or reconstruct the piconet.

0101To resume the communication, the following steps S16 et seq. are carried out in the present invention: <ul id="ul0002" list-style="none" compact="compact"><li>(1) Process of acquiring performance parameters, or performance information, from the slaves, by means of the master.</li><li>(2) Process of setting the next master, or backup master (BM), on the basis of the performance parameters acquired from the slaves.</li><li>(3) Process of supplying the backup-master (BM) information to each slave.</li></ul>

0102These processes will be described below in detail. In the sequence diagram of FIG. 5, the master (device A) performs a BNEP setup process for the slave (device B) that has completed the synchronization, the security setup and the SDP process.

0103BNEP stands for "Bluetooth Network Encapsulation Protocol." This protocol makes it possible to transfer Ethernet packets in the form of capsules on the Bluetooth L2CAP. BNEP packets are packets that are used as control packets or data packets to be transmitted by using BNEP.

0104BNEP packets have the configuration shown in FIG. 6A and FIG. 6B. FIG. 6A represents the BNEP packet and the header affixed to the BNEP packet. FIG. 6B depicts the configuration of the BNEP packet.

0105In the header to the BNEP packet, a BNEP type and an extension flag are set. The BNEP type may be [CONTROL] or the like, which indicates that the packet is a [GENERAL ETHERNET] packet, a [COMPRESSED ETHERNET] or a control packet. The extension flag is information that indicates whether the BNEP packet has an extension header (1 = header existing, 0 = header not existing). A header that accords with the BNEP type follows the extension flag. Further, an extension header is added, if any. A payload that accords with the BNEP type is stored, next to the extension flag.

0106FIG. 6B illustrates an example of a payload. The BNEP packet comprises a destination address, a source address, a networking protocol type, an extension header, if any, and a payload. The destination address and the source address are, for example, Bluetooth-device addresses (BD addresses). The networking protocol type is, for example, a protocol type that accords with the Ethernet.

0107In the present invention, each slave in the piconet transmits a BNEP packet (or control packet) to the master, the packet containing the performance parameter representing the performance value of the slave. The master evaluates the master aptitude that the slave has, from the performance parameter it has received from the slave. From the master aptitude thus evaluated, the master then determines whether the slave can be used as next master and determines which slave should be used as a backup master (BM).

0108FIG. 7 shows the format of the extension header that is added to the BNEP packet. The extension header contains an extension type, an extension flag, an extension length and a payload (extension payload). The extension type represents the type of transmission of a performance parameter or the type of transmission of a backup-master information and the like. The extension flag indicates whether the packet has any other extension header (1 = header existing, 0 = header not existing). The extension length represents the length of the extension header. A control packet, for example, can be added, as an extension header, to any other BNEP packet.

0109FIG. 8 shows examples of performance parameters to be transmitted from a slave to the master in the network (i.e., piconet). The performance parameters are values evaluated of the slave. They can be used as indicators to determine whether the data-processing performance items of the slave enable the slave to be selected as master.

0110In the examples shown in FIG. 8, the remaining battery power, the CPU performance, the memory resource, the electric-field intensity (RSSI: Radio Signal Strength Indicator), and the information showing whether the slave can be set as master are the data-processing performance items that are used as performance parameters. The performance parameters include parameter identifiers 0 x 01 to 0 x 05, respectively. Note that "0 x" means that each parameter identifier is a hexadecimal number.

0111Of the performance parameters, the remaining battery power to the RSSI may have a value ranging from 0 x 00 to 0 x FF (1 byte = 256 possible values) on the basis of the parameter-evaluation reference values held in slaves. These parameters may indicate the lowest performance = 00, and the highest performance = FF.

0112More precisely, the remaining battery power is set as a performance parameter having value FF indicating the highest performance, if the slave is connected to an AC power supply and is therefore continuously supplied with electric power. The slave may use a rechargeable battery, a cell or the like. In this case, the performance parameter ranges from 00 to FF in accordance with the power that remains in the battery, cell or the like. These reference values are held, as common data, in all slaves. Alternatively, the master may hold the reference values and may supply them, when necessary, to the slaves.

0113The CPU performance is a performance parameter that is set in accordance with the type and operating clock frequency of the CPU. This performance parameter has a specific value set, also in accordance with the data common to all slaves.

0114The memory resource is a performance parameter that is set in accordance with the storage capacity which remains in the flash memory and RAM provided in the slave and which can be effectively used. This performance parameter has a specific value set also in accordance with the data common to all slaves.

0115The electric-field intensity (RSSI) is a performance parameter that is set in accordance with the electric-field intensity (RSSI) determined from the condition of the Bluetooth communication between the slave and the master. This performance parameter has a specific value that is set also in accordance with the data common to all slaves.

0116The master aptitude, or master-aptitude information, is a performance parameter that has a specific value if the slave cannot be set as master because it cannot make routing of packets between the other slaves or because the user has set it as a slave that cannot be used as master. If the slave can be used as master, the master aptitude has another specific value indicating that the slave can be set as master. This performance parameter may have a value ranging from 0 x 00 to 0 x FF. Alternatively, it may have the value indicating that the slave can be used as master, or the value indicating that the slave cannot be used as master.

0117As described above, the piconet comprising one master and a plurality of slaves can be an independent network (in ad-hoc mode) that is not connected to any external networks, or a network (in infrastructure mode) that is connected to any other network, such as the Internet or another piconet, through the master. While the piconet remains connected to any other network (in infrastructure mode), the master makes routing of packets between the slaves constituting the piconet, thus achieving the packet exchange within the piconet, and also accomplishing packet exchange with the external networks. Thus, the master is called "NAP (Network Access Point)." While the piconet remains an independent network (in ad-hoc mode), not connected to the external networks, the master makes routing of packets between the slaves constituting the piconet. In this case, the master is called "GN (Group Ad-hoc Network)."

0118The master may be connected to any other network, thus functioning as a NAP, or may not be connected to any other network, thus functioning as a GN only. The information showing whether the master can function as a NAP or function as a GN only can be set as master-aptitude information. In this case, the master-aptitude information has one of the following four performance-parameter values: <ul id="ul0003" list-style="none" compact="compact"><li>(a) Non-master aptitude</li><li>(b) Master aptitude, either as NAP and GN</li><li>(c) Master aptitude, as GN only</li><li>(d) Master aptitude, as NAP only</li></ul>

0119FIG. 8 shows the remaining battery power, CPU performance, memory resource, electric-field intensity (RSSI: Radio Signal Strength Indicator) and master aptitude, i.e., the information items that are exemplified as performance parameters. Only some of these information items may be applied. Otherwise, information items other than these may be applied.

0120To transmit the information representing the values of these performance parameters to the master, an extension header (see FIG. 8) descried with reference to FIG. 7 is added to a BNEP packet. The parameter identifiers (PARAMs) and the values (indices) of the performance parameters are incorporated, as a payload, into the extension header. The BNEP packet is then transmitted to the master.

0121The extension type and payload of the extension header of a packet which is to be transmitted and which contains the performance parameters will be described, with reference to FIG. 9A and FIG. 9B.

0122As FIG. 9A shows, the extension type is set to [BNEP Extension Control], which indicates that a control packet should be transmitted.

0123As 9B depicts, the payload (Extension Payload) contains head data and subsequent data. The head data consists of [NET PARAM] and [PARAMNUM]. [NET PARAM] indicates that the payload contains performance parameters to be transmitted, and [PARAMNUM] represents the number of parameters contained in the payload. The subsequent data consists of different performance parameters, each composed of a parameter identifier (PARAM) and a performance parameter value (INDEX). These performance parameters may be transmitted in the form of an ordinary control packet.

0124As seen from FIG. 9B, the number (PARAMNUM) of parameters to be transmitted is [0 x 05] for the head data, indicating that the payload contains five parameters. The data item [0 x 01] [0 x 2C] follows [0 x 05]. As is clear from FIG. 8, [0 x 01] is the remaining battery power, and [0 x 2C] is the value of the performance parameter for the remaining battery power.

0125Further, [0 x 02] [0 x C3] indicates that the value of the performance parameter of the CPU performance is [0 x C3]; [0 x 03] [0 x 38] indicates that the value of the performance parameter of the memory resource is [0 x 38]; and [0 x 04] [0 x 8A] indicates that the value of the performance parameter of RSSI is [0 x 8A]. Moreover, [0 x 05] [0 x 01] is data that is a response to the inquiry of whether the slave can be set as master. For example, [0 x 01] indicates that the slave can be master that can function as both NAP and GN.

0126Referring to the sequence diagram of FIG. 5 again, the device B working as a slave transmits a control packet to the master (device A). The extension header of the control packet contains a payload that consists of the above-mentioned performance parameters. Upon receipt of the control packet, the master (device A) starts performing the service assigned to it. Namely, the master performs the process of establishing communication (Step S 17).

0127Steps S11 to S17 are carried out for all the slaves provided in the piconet. That is, the above-described procedure is performed between the devices B to G functioning as slaves, on the one hand, and the master (device A), on the other. The master accumulates the values of the performance parameters of each slave existing in the piconet. When a new slave may join the piconet, the same procedure is executed, and the master acquires performance parameters from the new device added to the piconet. Any slave device may change in operating condition. In this case, the slave device transmits a control packet or BNEP packet, the extension header of which contains the performance parameters updated, to the master.

0128In accordance with the performance parameter acquired from the slaves, the master sets one of the slaves, as a backup master (BM), or a candidate for master.

0129The process of setting a slave as a backup master (BM) will be explained below. Assume that the master has already acquired the parameters, i.e., the remaining battery power to the master aptitude, from all slaves.

0130First, any slave whose master aptitude is negative is rejected as a backup-master (BM) candidate. The remaining slaves, each having an affirmative master aptitude, are compared in terms of the other performance parameters. In other words, the master first figures out the master aptitudes of these slaves based on the performance parameters it has received from the slaves and then selects one of the slaves as backup master, i.e., the next master, in accordance with the master aptitudes figured out.

0131More specifically, weight coefficients (α to δ) are assigned to (1) remaining battery power to (4) RSSI, respectively. The weight coefficients are applied to figure out the master aptitude of each slave from the parameters (1) to (4) acquired. The master aptitude of the slave (device B), B(BM), for example, is figured out as expressed by the following equation:<maths id="math0001" num=""><math display="block"><mrow><mtext>B(BM) = αB1 + βB2 + γB3 + δB4</mtext></mrow></math><img file="EP1548985A1_D0001.tif" /></maths> where B1, B2, B3 and B4 are (1) remaining battery power, (2) CPU performance, (3) memory resource and (4) RSSI of the slave (device B).

0132The master aptitudes C(BM) to G(BM) of the other slaves, i.e., devices C to G, are figured out in the same way as that of the slave (device B). The master can adjust the weight coefficients α to δ, to select one slave as backup master, in accordance with the operating condition of the network.

0133After figuring out the master aptitudes of all slaves, the master selects one of the slaves, which has the highest of the master aptitudes B(BM) to G(BM) figured out, as backup master (BM). At the same time, the master generates a list that shows the slaves in the descending order of their master aptitudes (i.e., possibility as being used as backup master (BM)).

0134FIG. 10 shows such a list. This list shows the slaves arranged in the descending order of the master aptitude. The list contains the address (Bluetooth device (BD) address), page scan mode that is connection information and clock offset information of each slave. These information items have been acquired in the inquiry process and the paging process, both included in the sequence illustrated in FIG. 5.

0135The master figures out master aptitudes for the slaves, based on the performance parameters it has acquired from the slaves. The master selects, as backup master (BM), the slave for which the highest master aptitude has been obtained. Next, the master transmits the information concerning the backup master (BM), or the slave thus selected, to each slave.

0136FIG. 11 shows the sequence that begins with the transmission of the backup-master (BM) information from the master to the slaves and ends with the transition of master function to the backup master. With reference to the sequence diagram, the processes constituting this sequence will be described in detail.

0137In Step S21 shown in FIG. 11, the master transmits the information about the device for which the highest master aptitude has been figured out and which has been therefore selected as backup master (BM), to each slave. Thus, the master notifies BM selection to the slaves. The backup-master (BM) information is transmitted to the slaves, as a data item contained in a BNEP control packet.

0138The configuration of the BNEP control packet containing the backup-master (BM) information will be explained with reference to FIG. 12.

0139As FIG. 12A shows, [BNEP CONTROL] is set in the BNEP type (BNEP Type), indicating that the packet is a control packet.

0140As FIG. 12B depicts, [NET BM SELECTION] is set in the BNEP payload, indicating that the backup master (BM) information is being transmitted. In the BNEP payload, [NET BM SELECTION] is followed by Bluetooth-device address (BD ADDR), page scan mode (PageScanMode), clock offset (ClockOffset), and connection backoff time (Connect Backoff Time). The Bluetooth-device address is the address of the slave selected as backup master (BM). The page scan mode is information that must be used to make the slaves operate in synchronism with the backup master (BM). The connection backoff time causes the slaves to make connection requests (Page) at different times to the backup master (BM), i.e., the new master. The control packet may be transmitted in the form of an extension header that is added to the BNEP packet.

0141The connection backoff time (Connect Backoff Time) sets different backoff times to the slaves so that the slaves may not make connection requests at the same time. Nevertheless, the backoff time need not be notified to each slave if backoff times based on random numbers are set to the slaves. In this case, the slaves will not be connected to the master at the same time.

0142In Step S21 shown in the sequence diagram of FIG. 11, the backup-master information is transmitted to all slaves. The master (device A) may be soon removed from the piconet thereafter. In this case, in Step S22, the master transmits a backup-master activation notice (BM Activation) to the device B that has been selected as backup master.

0143A configuration that the packet containing the backup-master activation notice (BM Activation) may have will be described, with reference to FIG. 13A and FIG. 13B.

0144As FIG. 13A shows, [BNEP Control] is set in the BNEP type (BNEP Type), indicating that the packet is a control packet.

0145As FIG. 13B depicts, [NET BM Activation] is set in the BNEP payload (BNEP Payload), indicating the transmission of a backup-master activation notice. Further, [Target UUID] is set in the BNEP payload, following [NET BM Activation]. [Target UUID] is type information that shows whether the master should be as a NAP (Network Access Point) or a GN (Group Ad-hoc Network). This control packet may be transmitted in the form of an extension header that is added to the BNEP packet.

0146As indicated earlier, a NAP (Network Access Point) is the master in a network (piconet) that is connected to any other network (in infrastructure mode). The NAP makes routing of packets between the slaves in the piconet. That is, it performs packet exchange within the piconet. In addition, the NAP effects packet exchange between the piconet and any external network connected to the piconet. If the piconet is independent, not connected to any external network (in Ad-hoc mode), the master functions as a GN (Group Ad-hoc Network) to make routing of communication packets between the slaves within the piconet.

0147Referring the sequence diagram of FIG. 11 again, the master (device A) transmits the backup-master information again to each slave just before the master is removed from the piconet. This is because a new slave may be incorporated into the piconet and the master (device A) may therefore receive performance parameters from the new slave and figure out master aptitudes for all existing slaves. Thus, the master sends the latest, or updated backup-master information to all slaves. Moreover, the master transmits a notice of net trigger (NET Trigger), informing that it will stop offering service as master.

0148A configuration of the notification of the net trigger (NET Trigger) will be described with reference to FIG. 14A and FIG. 14B.

0149As illustrated in FIG. 14A, [BNEP Control] is set in the BNEP type (BNEP Type), indicating that the packet is a control packet.

0150As shown in FIG. 14B, [NET Trigger] is set in the BNEP payload (BNEP Payload), indicating the transmission of a notice of the net trigger (NET Trigger). Further, [BD ADDR], [PageScanMode], [ClockOffset], [Target UUID] and [Delay before reconnect] are set in the BNEP payload, following [NET Trigger]. [BD ADDR] is the Bluetooth-device address of the backup master (BM) selected. [PageScanMode] is information that must be used to make the slaves operate in synchronism with the backup master (BM). [Target UUID] is type information that shows whether the master should be as a NAP (Network Access Point) or a GN (Group Ad-hoc Network). [Delay before reconnect] causes the slaves to make connection requests (Pages) at different times to the backup master (BM), i.e., the new master. This control packet may be transmitted in the form of an extension header that is added to the BNEP packet.

0151Like the connection backoff time (Connect Backoff Time) described above, [Delay before reconnect], or connection delay time, sets different backoff times to the slaves so that the slaves may not make connection requests at the same time. Nevertheless, the backoff time need not be notified to each slave if backoff times based on random numbers are set to the slaves. In this case, the slaves will not be connected to the master at the same time.

0152Next, in Step S24, each slave is disconnected (Disconnect) from the master (device A) which will be removed from the piconet, if the net trigger (NET Trigger) or the like has notified that the master will be removed from the piconet. If the net trigger has not notified the eventual removal of the master, no apparent disconnection of slaves will be performed when the power supply to the master is abruptly turned off. In this case, an ordinary timeout signal is generated, which indicates that the slaves have been disconnected from the master. If the master is abruptly removed from the piconet, the net trigger (NET Trigger) may not be notified in some cases.

0153In these cases, each slave has received the backup-master (BM) information transmitted to it in Step S21, i.e., the step of setting the piconet. Each slave can therefore perform paging (Page) to the backup master (BM) on the basis of the information it has received. The backup-master (BM) information contains synchronization information. Thus, each slave can be efficiently connected to the backup master, without carrying out the process of initially establishing synchronization.

0154The sequence of spontaneously or forcibly disconnecting the slave having the backup-master information from the previous master and then connecting the same to the new master in accordance with the backup-master information will be explained with reference to FIG. 15.

0155The sequence diagram of FIG. 15 illustrates how the device B operates as master when it receives the master activation notice from the device A after the previous master (device A) is removed from the piconet and then the device B is selected as backup master.

0156In Step S31, the slaves (device C to device G) perform paging (Page) to the new master (device B). In the ordinary connection process, the slaves must transmit an inquiry to search for the master and must acquire prescribed synchronization information, as has been described with reference to FIG. 5. In this case, the slaves have received the backup-master information from the previous master (in Steps S21 to S23 shown in FIG. 11). That is, they have acquired the address of the device B set as backup master and the synchronization information. The slaves can therefore communicate with the master by carrying out paging (Page); they need not transmit an inquiry. In the paging, the master and each slave exchange their attribute information items (i.e., FHS packets). The attribute information items, thus exchanged, render the master and the slave synchronous in terms of frequency axis and time axis.

0157Next, in Step S32, the slaves (device C to device G) transmit BNEP packets to the new master (device B), notifying performance parameters to the new master. This process is similar to Step S 16 of the process sequence of FIG. 5. The slaves transmit performance parameters shown in FIG. 8 to the new master, in the form of packets that have the configurations described with reference to FIG. 6, FIG. 7 and FIG. 9.

0158Thereafter, the new master figures out master aptitudes for the slaves, based on the performance parameters received, in the same way as has been explained above. The new master selects one of the slaves as next backup master (BM). The new master then notifies the address of the slave selected as next backup master to the other slaves, together with the synchronization information of this slave.

0159In the piconet, the master thus selects one slave as backup mater, i.e., candidate for the next master, in accordance with the performance parameters it has received from the slaves. The master then notifies the address and synchronization information of the backup master, as backup-master information, to the slaves. From the backup-master information, the slaves can determine which device is the next master. Hence, synchronization can be immediately secured between the new master and the slaves, on the basis of the address information and synchronization information, both contained in the backup-master information. This minimizes the interruption of communication between the devices that constitute the piconet when the master device is removed from the piconet.

0160In the process sequence of FIG. 15, no steps are illustrated between Step S31 and Step S32. Nonetheless, the SDP (Service Device Protocol) process and the security-setup process are carried out after Step S31 and before Step S32.

0161The process of selecting a backup master and notifying the backup master selected will be described in detail. More precisely, the steps performed by the master will be described with reference to the flowchart of FIG. 16, and the steps performed in a slave will be described with reference to the flowchart of FIG. 17.

0162FIG. 16 is a flowchart explaining the gist of the process that the mater carries out in the piconet. First, in Step S101, the master receives performance parameters from each slave. The parameters represent the various performances of the slave, such as the remaining battery power, the CPU performance and the like.

0163In Step S102, the master determines whether it has received performance parameters from all slaves. If it has received the parameters from all slaves, the master evaluates the master aptitude of each slave on the basis of the performance parameters it has received from the slave. To be more specific, the master adjusts weight coefficients in accordance with the operating condition of the network, applies them to the various performance indicators of each slave, such as the remaining battery power and the CPU performance, and figures out mater aptitudes for each slave, from the performance indicators thus weighted. Then, in Step S 103, the master selects the slave having the highest mater aptitudes, as backup master.

0164In Step S 104, the master transmits the information of the backup master, i.e., the slave selected in accordance with its master aptitude, to the slaves. That is, the master transmits the address information and synchronization information of the backup master to the slaves. The master carries out the process shown in this flowchart, every time it receives performance parameters from any new slave or any existing slave. The master can, therefore, select a slave that can most appropriately operate as backup master in the present operating condition of the network.

0165How each slave operates in the piconet will be described, with reference to FIG. 17. In Step S201, the slave transmits performance parameters to the master. This step is to transmit the parameters representing the various performance items of the slave, such as the remaining battery power and the CPU performance, and contained in the extension header of a BNEP packet.

0166Next, in Step S202, the slaves receive backup-master information from the master. This information is stored into the memory unit provided in the slave. In Step S203, the slave determines whether it has been disconnected from the master. The slave may be spontaneously disconnected from the master when it receives a net trigger from the master (in Step S23 shown in FIG. 11) or disconnected due to an event on the part of the master, e.g., the power running-out of the battery or the removal of the master from the network. The operating condition of the slave may change, changing the performance parameters thereof. If this happens, Step S201 may be carried out.

0167In any case where the slave is disconnected from the master, it goes to Step S204. In Step S204, the slave performs the paging (Page) with respect to the backup master that is the new master. Thus, the backup master functions as master of the piconet.

0168Further, in Step S205, the slave transmits its performance parameters to the new master.

0169As described above, the slave receives the address information and synchronization information of the backup master from the backup master and holds them as backup-master information. From the backup-master information, the slave can determine which device is the next master after the master is removed from the piconet. This enables the slave to be connected to the new master and operate in synchronism therewith efficiently.

0170In the instance described above, the backup-master information that the master gives the slaves is concerned with only the device that has the highest master aptitude. Instead, the information may be a list showing the devices in the descending order of master aptitude. Once each slave has received this list as backup-master information, it acquires information about the other devices constituting the piconet. Thus, if any slave cannot be connected to the backup master having the highest, master aptitude because this backup master has been removed from the piconet prior to the master, it can be connected to the backup master that has the second highest master aptitude.

0171A configuration of a BNEP packet, which contains the backup-master information provided in the form of such a list and which is to be transmitted to the slaves, will be described with reference to FIG. 18A and FIG. 18B.

0172As FIG. 18A shows, [BNEP Control] is set in BNEP type (BNEP Type), indicating that the packet is a control packet.

0173As FIG. 18B depicts, [NET BM LIST] and [LIST NUM] are set in the BNEP payload (BNEP Payload). [NET BM LIST] shows that the information to be transmitted is a list of backup masters (BMs). [LIST NUM] represents the number of the backup masters (BMs) shown in the list. Sets of data items [BD ADDR], [PageScanMode], [ClockOffset] and [Connect Backoff Time] are set in BNEP payload (BNEP Payload), after the [NET BM LIST] and [LIST NUM]. These data-item sets correspond to the backup masters shown in the list, respectively. The data items of each set are arranged in the order they are mentioned. [BD ADDR] represents the Bluetooth-device addresses of the backup masters (BMs). [PageScanMode] is information that enables the slaves to operate in page scan mode (PageScanMode), namely in synchronism with any backup master (BM). [Connect Backoff Time] makes the slaves to transmit connection requests (Pages) at different times to the backup master (BM), i.e., the new master. This control packet may be transmitted in the form of an extension header that is added to the BNEP packet.

0174In the embodiment described above, a slave performs the connection process with respect to the new master, i.e., the backup master. Instead, the backup master may carry out the connection process in accordance with the list, with respect to a slave. That is, the backup master may transmit the slave information about the slaves provided in the piconet so that it may be connected to a slave after the previous master is removed from the piconet.

0175The sequence of the connection process the backup master performs will be explained, with reference to FIG. 19.

0176The sequence diagram of FIG. 19 illustrates the steps that are performed after the device A, which is the existing master, selects the device B as backup master in accordance with the performance parameters.

0177In Step S51, the device A, or existing master, transmits to the device B, or backup master, a BNEP packet that contains a slave list (Slave List).

0178A configuration that the BNEP packet containing the slave list may have will be described with reference to FIG. 20A and FIG. 20B.

0179As seen from FIG. 20A, [BNEP Control] is set in the BNEP type (BNEP Type), indicating that the packet is a control packet.

0180As FIG. 20B shows, [NET SLAVES LIST] and [LIST NUM] are set in the payload (BNEP Payload). [NET SLAVES LIST] indicates that the list is a slave list. [LIST NUM] represents the number of slave information items to be transmitted in the form of a list. Sets of data items [BD ADDR], [PageScanMode], [ClockOffset] and [Connect Backoff Time] are set in the payload (BNEP Payload), after the [NET SLAVES LIST] and [LIST NUM]. These data-item sets correspond to the slaves shown in the list, respectively. The data items of each set are arranged in the order they are mentioned. [BD ADDR] represents the Bluetooth-device addresses of the slaves. The next data items, [PageScanMode], are information that enables the backup master to operate in synchronism with the slaves. [Connect Backoff Time] makes the new master to transmit connection requests to the slaves at different times. This control packet may be transmitted in the form of an extension header that is added to the BNEP packet.

0181The new master may set the connection backoff time (Connect Backoff Time) by itself. In this case, the connection backoff time need not be contained, as notification data, in the BNEP packet.

0182The description will be further made, with reference to the process sequence shown in FIG. 19 again. In Step S51 in the sequence diagram of FIG. 19, the above-mentioned slave list is transmitted to the backup master (device B). When the master (device A) is thereafter removed from the piconet, it transmits a backup-master activation notice (BM Activation) to the device B that has been selected as a backup master, in Step S52. The backup-master activation notice (BM Activation) has the configuration described with reference to FIG. 13. If any new slave is added to the piconet, the list data is updated to contain the information about the new slave and is transmitted to the backup master (device B).

0183Next, in Step S53, a disconnection process (Disconnect) is carried out to disconnect the master (device A) from the slaves. This disconnection is either a spontaneous one or a forced one made by the master.

0184After the master is disconnected from the slaves, the device B, i.e., new master, performs the process of connecting itself to the slaves (devices C to G), one after another on the basis of the slave it has received. As new master, the device B can efficiently establish connection with each slave, by using the address, i.e., Bluetooth-device address (BD ADDR), and the synchronization information, which are contained in the slave list transmitted from the previous master (device A).

0185In the piconet thus set anew, the slaves start communication with the new master.

0186The present invention has been described in detail, with reference to a specific embodiment. Nonetheless, it is obvious that any person skilled in the art can modify or replace the embodiment without departing from the scope and spirit of this invention. That is, the embodiment describe above is nothing more than an example of the invention. To understand the gist of this invention, the claims set forth at the end of this specification should be considered.

0187The sequence of processes, described above, can be implemented by the use of hardware or software, or both. To perform the process sequence by using software, a program describing the sequence may be installed in a dedicated hardware element, or a memory, incorporated in a computer, or may be installed into a computer that can perform various processes.

0188The program may be recorded beforehand in, for example, a hard disc or a ROM (Read Only Memory) that is a recording medium. Alternatively, the program may be temporarily or permanently stored (recorded) in a removable recording medium such as a flexible disc, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto Optical) disc, a DVD (Digital Versatile Disc), a magnetic disc, a semiconductor memory or the like. The removable recording medium may be provided in the form of so-called "package software."

0189The program may be installed into the computer, read from such a removable recording medium as specified above. Otherwise, it may be transferred to the computer from a download site, either by wireless or via a network such as a LAN (Local Area Network) or the Internet. The computer receives the program thus transferred. The program can be installed in the recording medium, e.g., a hard disc, provided in the computer.

0190According to the present invention, various processes can be performed not only sequentially in the order described above, but also in parallel or independently, depending on the performances of the devices that carry out them or in accordance with necessity. The system implementing this invention is a logical assembly of various components. All components of the system are not necessarily arranged within the same housing.

0191The present invention is not limited to the embodiment that has been described with reference to the drawings. It would be obvious to anyone skilled in the art that various changes and modification can be made without departing the scope and spirit represented by the claims set forth at the end of this specification.

Industrial Applicability

0192As has been described, the present invention relates to a wireless communication network that comprises a master that performs a communication control process and one or more slave that can communicate via the master. Each slave transmits its various data-processing abilities, in the form of various performance parameters, to the master. The master selects one of the slaves as a candidate for the next master, on the basis of the performance parameters transmitted from the slaves. The master gives each slave the backup-master information that contains the address and synchronization information, both concerning the slave selected. From the backup-master information, each slave can determine which slave is the next master and can be immediately connected to the next master when the master is removed from the network. Hence, the user of the master need not select a slave as next master. In addition, the interruption of communication between the slaves can be shortened, and the slaves can be connected to the new master quickly and efficiently.

0193In accordance with this invention, performance parameters are the data-processing performance items evaluated of each slave, such as the remaining battery power, CPU performance, memory resource and RSSI (electric-field intensity). On the basis of these information items, the master can select a slave as backup master, which can cope with the operating condition of the network.

0194According to this invention, the backup-master information the master sends to the slaves contains the synchronization information about the backup master. Therefore, at least a part of the process of establishing synchronization necessary for the reconstruction of the network need not be carried out. This makes it possible to reconstruct the network efficiently within a short time.

0195In the present invention, backup-master information that is a list showing devices in the descending order of their master aptitudes may be transmitted to the slaves. Then, the slaves can have information about a plurality of backup masters. Namely, each slave can acquire the information of the other devices that constitute the piconet. Thus, if any slave cannot be connected to the backup master having the highest master aptitude when the master is removed from the piconet, because the backup master has been already removed from the piconet, it may be connected to the backup mater that has the second highest master aptitude.

0196According to this invention, a slave list may be transmitted the backup master. Then, in accordance with the slave list the device selected as new master can be connected to the slaves, one after another, after the master is disconnected from the slaves. Each slave need not perform any process to connect itself to the master. The device selected as new master can use the Bluetooth-device addresses (BD ADDRs) contained in the slave list and also the synchronization information, all transmitted from the previous master. The new master can therefore efficiently establish connection with the slaves. In the piconet thus set anew, the slaves can communicate with one another through the new master.