Abstract:
In a communication system having at least two piconets, each having at least one device communicating using a single radio resource and a piconet coordinator controlling the device, a connecting method for communications amongst the device and the piconet coordinators of the other piconets. A router device, which is located in an overlapping area of at least two piconets and is connected with the piconet coordinators, requests connection to the piconet coordinator connected with the adjacent piconet coordinators of the overlapping piconets. Upon receiving the message of the connection permit from a piconet coordinator, the router device requests connection to the adjacent piconet coordinator. Upon receiving the message of the connection permit, the device connects with the adjacent piconet coordinator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2004-2702 filed on Jan. 14, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of The Invention  
         [0003]     The present invention generally relates to a method for connecting (linking) at least two networks. More concretely, the present invention pertains to a method for connecting a plurality of networks forming a wireless personal area network (WPAN).  
         [0004]     2. Description of The Related Art  
         [0005]     A wireless personal area network (WPAN) wirelessly interconnects devices, such as computers and peripherals, mobile phones, and home appliances, in a short range of 10 m, supporting communications among the devices and thus providing various services. The WPAN has been developed to implement networks among the devices with the development of personal mobile digital devices such as laptop computers and personal digital assistants (PDAs). The WPAN has distinctive features including short range, compactness, low-power, usability (that is, when a user approaches to the WPAN, synchronization is automatically performed), and less interference.  
         [0006]      FIG. 1  illustrates configuration of the WPAN (piconet). Referring to  FIG. 1 , the WPAN includes a piconet coordinator (PNC) and at least one device (DEV). The PNC is selected among the DEVs forming the WPAN. A network including the PNC  100  and the DEVs  110  through  114  in the WPAN refers to a piconet. The piconet covers a range where the DEVs are located or a range of about 10 m in which the DEVs can move. When a particular DEV needs to communicate data with another DEV in the piconet, the particular DEV requests that the PNC  100  allocate of radio resources for the data communication. The PNC  100  allocates the radio resources to the requested DEV. The PNC  100  allocates one radio resource at a specific time interval.  
         [0007]      FIG. 2  illustrates another configuration of the piconet. Referring to  FIG. 2 , one piconet overlaps with the other piconet in the WPAN to extend the range of the data communication. In general, each piconet  220  and  222  communicates data using dedicated radio resources. Specifically, PNCs  200  and  202  select one available channel among 16 channels. DEVs and PNCs of the piconet  220  or  222  communicate with each other using the selected channel. Since the piconets  220  and  222  communicate using the dedicated radio resources, the piconets  220  and  222  do not have information on radio resources of the adjacent piconet. Consequently, the communication between the piconets of the WPAN is infeasible.  
       SUMMARY OF THE INVENTION  
       [0008]     To address the above problems and disadvantages of the conventional arrangement, an exemplary aspect of the present invention is to provide a system and method for connecting piconets forming a wireless personal area network (WPAN) for communications.  
         [0009]     Another exemplary aspect of the present invention is to provide a system and method enabling other devices to perform some functions of a router device when the router device consumes considerable power.  
         [0010]     Still another exemplary aspect of the present invention is to provide a system and method capable of varying a data reception period depending on the amount of data received from a piconet coordinator to the router device.  
         [0011]     In view of the above exemplary aspects and features of the present invention, there is provided an exemplary embodiment of a method for a router device to connect the piconet coordinators in a communication system comprising at least two piconets each comprising at least one device communicating using a single radio resource and a piconet coordinator controlling the device. The method comprises the steps of requesting connection with a second piconet coordinator of an overlapping piconet by a first router device which is located in the overlapping area of the at least two piconets and is connected with a first piconet coordinator of the at least two piconets, requesting connection to the first piconet coordinator when a message indicating connection permit is received, and connecting with the second piconet coordinator when a message indicating connection permit is received.  
         [0012]     Consistent with the another aspect of the present invention, in a communication system comprising at least two piconets each comprising at least one device communicating using a single radio resource and a piconet coordinator controlling the device, a system in which the device connects the piconet coordinators comprises a first router device connected with a first piconet coordinator, located in an overlapping area of the at least two piconets, sequentially requesting connection to a second piconet coordinator and the first piconet coordinator, and connecting with the second piconet coordinator when a message indicating a connection permit is received, the first piconet coordinator transmitting a message indicating the connection permit in response to the request from the router device, and the second piconet coordinator transmitting a message indicating the connection permit in response to the connection request from the router device and connecting with the device. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0013]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying figures in which:  
         [0014]      FIG. 1  illustrates a configuration of a WPAN;  
         [0015]      FIG. 2  illustrates overlapping piconets in the WPAN;  
         [0016]      FIG. 3  illustrates connections between a DEV located in an overlapping area of two piconets and PNCs;  
         [0017]      FIG. 4  illustrates a message sequence chart for the connections of the DEV located in the overlapping area of  FIG. 3 ;  
         [0018]      FIG. 5  illustrates connections between a DEV located in an overlapping area of three piconets and PNCs according to another exemplary embodiment of the present invention;  
         [0019]      FIG. 6  illustrates a message sequence chart for the connections of the DEV located in the overlapping area of  FIG. 5 ;  
         [0020]      FIG. 7  illustrates the consequent connection of  FIG. 6 ;  
         [0021]      FIG. 8  illustrates a reception period of beacons transmitted to PNCs from the DEV according to an exemplary embodiment of the present invention; and  
         [0022]      FIG. 9  illustrates a reception period of beacons transmitted to PNCs from the DEV according to an exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0023]     Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying figures, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below in order to explain the present invention by referring to the figures.  
         [0024]      FIG. 3  illustrates connections of piconets forming a wireless personal area network (WPAN), devices (DEVs), and a piconet coordinator (PNC) in each piconet according to an exemplary embodiment of the present invention. Hereinafter, a communication system including at least two piconets refers to an extended piconet.  
         [0025]     An extended piconet of  FIG. 3  includes a first piconet  320  controlled by a first PNC  300  and a second piconet  322  controlled by a second PNC  302 . The first PNC  300  communicates with DEVs in the first piconet  320  using dedicated radio resources. The DEVs allocated with radio resources from the first PNC  300  communicate with each other. The second PNC  302  also communicates with DEVs in the second piconet  322  using dedicated radio resources. It is assumed that the dedicated radio resource for the first piconet  320  is channel  1  and that the dedicated radio resource for the second piconet  322  is channel  4 .  
         [0026]     A particular DEV of the extended piconet may be located in area where at least two piconets overlap, as shown in  FIG. 3 . That is, the DEV  310  is located in the overlapping area of the first and second piconets  320  and  322 . Hereinafter, an overlapping area of at least two piconets refers to a router area, and a DEV in the router area refers to a router device (R-DEV). If a particular DEV is located in or moves into the router area, the particular DEV serves as the R-DEV. The following descriptions are made on a case when the DEV  310  moves into the router area and serves as the R-DEV.  
         [0027]     The R-DEV  310  searches available radio resources in the router area and discovers the channel  1  for the first piconet  320  and the channel  4  for the second piconet  322 . The R-DEV  310  is able to obtain the number of communicable piconets and PNCs by searching the available radio resources. The R-DEV  310  selects an initial piconet for data communication using the searched radio resources. It is assumed that the R-DEV  310  initially communicates data with the second PNC  302 .  
         [0028]     The R-DEV  310  sends a router function request message to the second PNC  302 . The following Table 1 shows an example of the router function request message.  
                                     TABLE 1                       2   1   1   3 × Connection list size                   Header   Command   Connection list   Coordinator information       field   frame identifier   size   for connection            Header   Payload                  
 
         [0029]     In Table 1, the number denotes a byte, and the command frame identifier indicates the router function request message. The connection list size represents the number of radio resources searched in the router area. The connection list size excludes the radio resources used in the piconet which the R-DEV is to initially communicate with. Hence, the connection list size of the R-DEV  310  of  FIG. 3  becomes ‘1’ by excluding the channel  4  of the second piconet  322  from the searched two radio resources. The coordinator information for connection represents information on the second PNC  302  of the second piconet  322  when the R-DEV  310  is to connect with the second piconet  322 . An example of the coordinator information for connection is shown in the following Table 2.  
                                                 TABLE 2                                   2   1                                        Coordinator ID   Channel number   Reserved                      
 
         [0030]     In Table 2, the coordinator ID represents an identifier of the PNC to be connected. The channel number represents a radio channel number used by the PNC. Referring back to  FIG. 3 , the coordinator ID is ‘1’ and the channel number is ‘1’. Table 2 is organized in correspondence with the piconet to be connected with the R-DEV.  
         [0031]     Upon receiving the router function request message, the second PNC  302  sends a router function response message to the R-DEV  310 . The following Table 3 shows an example of the router function response message.  
                                     TABLE 3                       2   1   1   3 × Connection list size                   Header   Command frame   Result   Coordinator information       field   identifier   size   For result            Header   Payload                  
 
         [0032]     Table 3, the result size is the same as the connection list size, that is, it represents the number of piconets to be connected, which is contained in the router function request message. The coordination information for result represents results with respect to each piconet to be connected. The following Table 4 shows an example of the coordinator information for result.  
                                                 TABLE 4                                   2   1                                        Coordinator ID   Channel number   Status                      
 
         [0033]     In Table 4, the status represents connection status of the piconet to be connected. The following Table 5 shows an example of the status.  
                   TABLE 5                       Status   Meaning                   000   Connection permit       001   Connection reject       010   Connection hold       111   Reserved                  
 
         [0034]     In Table 5, the connection permit denotes that the second PNC  302  permits connection of the R-DEV  310 . The connection reject denotes that the second PNC  302  rejects connection of the R-DEV  310  (the R-DEV  310  does not need to perform the same function if an existing device links the first PNC  300  and the second PNC  302 ). The connection hold denotes that the R-DEV  310  does not need current connection with the first PNC  300  and the second PNC  302  but may need the connection afterward.  
         [0035]     In order to create the router function response message, the second PNC  302  has to pre-store information on the existing DEV performing the router function. The second PNC  302  determines whether to permit or to reject the connection with respect to the DEV requesting the router function based on the pre-stored information. The following Table 6 shows an example of a information (connection information) table stored in the second PNC  302 .  
                               TABLE 6                                   Coordinator ID   Channel   Router ID                           ox0003   channel 5   ox0003           ox0007   channel 14   ox0007           .   .   .           .   .   .           .   .   .                      
 
         [0036]     In Table 6, the second PNC  302  is connected with a third PNC using channel  5  via a R-DEV  3  and with a seventh PNC using channel  14  via a R-DEV  7 . The second PNC  302  permits connection function of the R-DEV  310  based on Table 6. When delivering information on the connection permit, the connection information table is updated so as to contain information on the permitted R-DEV. When delivering information on the connection hold to the R-DEV, the second PNC  2  stores information on the R-DEV. The information may be stored in the same storage as with Table 6 or in a separate storage. A certain identifier is attached to the information for the separate storage. Hence, the second PNC  302  is able to allow the R-DEV to serve as the router.  
         [0037]     The following Table 7 shows an example of the router function request message sent from the second PNC  302  to the R-DEV  310 . As shown in  FIG. 3 , the PNC can send the router function request message to the R-DEV.  
                                             TABLE 7                       2   1   1   2 × Router list size                   Header   Command frame   Router list   Router ID       field   identifier   size            Header       Payload                  
 
         [0038]     The router list size represents the number of the R-DEV requesting the router function, and the router ID represents an identifier of the R-DEV requesting the router function.  
         [0039]     Upon receiving the connection reject or connection hold message, the R-DEV  310  aborts the connection attempt with respect to the first PNC  300  and attempts to communicate with the second PNC  302  or the DEVs in the second piconet  322 . The following descriptions are made with respect to when the R-DEV  310  receives the connection permit message or the router function request message. The R-DEV  310  sends a router function allowance request message to the first PNC  300 . The R-DEV  310  changes to the radio channel used in the first piconet  320  so as to send the router function allowance request message to the first PNC  300 . Upon receiving the router function allowance request message, the first PNC  300  sends a router function allowance response message.  
         [0040]     The first PNC  300 , which also stores information as shown in Table 6, determines the response for the router function allowance request message based on Table 6. If the connection function for the R-DEV  310  is allowed, the first PNC  300  sends the router function allowance response message indicating the allowance. If the connection function is not allowed, the first PNC  300  sends the router function allowance message indicating the disapproval. For the transmission of the router function allowance response message indicating the allowance, the first PNC  300  updates the Table 6. Specifically, the first PNC  300  adds information to the Table 6 that the second PNC  302  using the channel  4  is being connected via the R-DEV  310 .  
         [0041]     Upon receiving the router function allowance response message, the R-DEV  310  changes to the radio channel used in the second piconet  322 . A connection message is sent to the second PNC  302  through the changed radio channel. Upon receiving the connection message, the second PNC  302  deletes the information on the R-DEV  310  from the connection information table when the connection message contains information indicating the disapproval of the connection function.  
         [0042]      FIG. 4  illustrates a sequence of the message transmitted among the first PNC  300 , the second PNC  302 , and the R-DEV  310 , which is described below.  
         [0043]     The R-DEV  310  sends the router function request message to the second PNC  302  at step S 400 . Upon receiving the router function request message, the second PNC  302  sends the router function response message to the R-DEV  310  at step S 402 . The information contained in the router function response message is generated as aforementioned with reference to  FIG. 3 .  
         [0044]     The R-DEV  310  sends the router function allowance request message to the first PNC  300  at step S 404 . Upon receiving the router function allowance request message, the first PNC  300  sends the router function allowance response message to the R-DEV  310  at step S 406 . The information contained in the router function allowance response message is generated as aforementioned with reference to  FIG. 3 . Upon receiving the router function allowance response message, the R-DEV  310  sends the connection message to the second PNC  302  at step S 408 .  
         [0045]      FIG. 5  illustrates three piconets according to another exemplary embodiment of the present invention. Referring to  FIG. 5 , a first PNC  500  manages the first piconet  520 , a second PNC  502  manages the second piconet  522 , and a third PNC  504  manages the third piconet  524 . The first piconet  520  uses channel  1 , the second piconet  522  uses channel  4 , and the third piconet  524  uses channel  5  for communication. A fourth R-DEV  510  serves to interconnect the first through third PNCs  500 ,  502 , and  504 . The following Table 8 shows an example of the information (connection information) table stored in the second PNC  502 .  
                               TABLE 8                                   Coordinator ID   Channel   Router ID                           ox0001   channel 1   ox0004           ox0003   channel 5   ox0004           .   .   .           .   .   .           .   .   .                        
         [0046]     Still referring to  FIG. 5 , a fifth R-DEV  512  moves into the router area between the second piconet  522  and the third piconet  524 . The fifth R-DEV  512  performs the same functions as the R-DEV  310  of  FIG. 3 . The fifth R-DEV  512  sends a router function request message to the second PNC  502 . Upon receiving the router function request message, the second PNC  502  sends a router function response message to the fifth R-DEV  512 . It is assumed that the router function response message indicates the connection permit. After sending such a router function response message, the second PNC  502  updates the connection information table, which is shown by way of example in the following Table 9.  
                               TABLE 9                                   Coordinator ID   Channel   Router ID                           ox0001   channel 1   ox0004           ox0003   channel 5   ox0004           ox0003   channel 5   ox0005                      
 
         [0047]     The fifth R-DEV  512  sends a router function allowance request message to the third PNC  504 . Upon receiving the router function allowance request message, the third PNC  504  sends a router function allowance response message to the fifth R-DEV  512 . If the router function allowance response message indicates the connection permit, the second PNC  502  maintains the information as shown in Table 9.  
         [0048]     Referring to  FIG. 5 , the fourth R-DEV  510  consumes more power than the other DEVs. Hence, it is necessary that the other DEVs perform some functions of the fourth R-DEV  510 .  FIG. 6  illustrates the other DEVs performing some functions of the fourth R-DEV  510  that consumes considerable power, which is described below in detail.  
         [0049]     Referring to  FIGS. 5 and 6 , the fourth R-DEV  510  sends a connection release request message to the first through third PNCs  500 ,  502 , and  504  at step S 600 . Upon receiving the connection release request message, the first through third PNCs  500 ,  502 , and  504  look up the stored connection information table to obtain information on a R-DEV of which connection is held. The first PNC  500  obtains, from Table 5, information on the sixth R-DEV  514  of which connection is held.  
         [0050]     The first PNC  500  sends a router function request message to the sixth R-DEV  514  at step S 602 . Upon receiving the router function request message, the sixth R-DEV  514  retrieves information on a connectable piconet. As a result of the retrieval, the sixth R-DEV  514  obtains information on the third PNC  504 . The sixth R-DEV  514  sends a router function allowance request message to the third PNC  504  based on the obtained information at step S 604 . Upon receiving the router function allowance request message, the third PNC  504  sends a router function allowance response message to the sixth R-DEV  514  at step S 606 .  
         [0051]     The sixth R-DEV  514  sends a connection message to the first PNC  500  at step S 608 . It is assumed that the connection message contains information on the connection permit. Upon receiving the connection message, the first PNC  500  sends a connection release message to the fourth R-DEV  510  at step S 610 . Then, the first PNC  500  deletes, from the connection information table, the information instructing that the fourth R-DEV  510  is connected with the third PNC  504  using the channel  5 . The fourth R-DEV  510  sends the received connection release message to the second and third PNCs  502  and  504  at step S 612 . Upon receiving the connection release message, the second and third PNCs  502  and  504  delete the information indicating that the fourth R-DEV  510  is connected with the third PNC  504  using the channel  5 . The following Table 10 shows an example of the connection information table of which some information is deleted by the second PNC  502 .  
                               TABLE 10                                   Coordinator ID   Channel   Router ID                           Ox0001   channel 1   ox0004           ox0003   channel 5   ox0005                      
 
         [0052]      FIG. 7  illustrates connections of the R-DEVs after transmitting the messages of  FIG. 6 . Referring to  FIG. 7 , the fourth R-DEV  510  is disconnected with the third PNC  504 . Instead, the sixth R-DEV  514  is connected with the third PNC  504 . The fourth R-DEV  510  interconnects the first PNC  500  and the second PNC  502 . The fifth R-DEV  512  interconnects the second PNC  502  and the third PNC  504 . The sixth R-DEV  514  interconnects the third PNC  504  and the first PNC  500 . Such connections allow the fourth R-DEV  510  through the sixth R-DEV  514  to consume substantially the same power for the communication.  
         [0053]      FIG. 8  illustrates synchronization for data transmission among two PNCs and a R-DEV connected with the two PNCs according to an exemplary embodiment of the present invention. Referring to  FIG. 8 , the R-DEV has to receive a frame carrying sync information from each PNC to acquire synchronization. The PNCs append the sync information to a beacon period of the frame and transmit the frame. The beacon period also contains information on data amount (size) to be transmitted to the R-DEV from the PNCs. The R-DEV, which is connected with the at least two PNCs, needs to change to a channel corresponding to each PNC to acquire synchronization. The more frequently the channel changes, the more power the R-DEV consumes. According to an embodiment of the present invention, channel change period varies depending on a piconet device.  
         [0054]     Still referring to  FIG. 8 , the PNCs are divided into a master PNC and a slave PNC. The master PNC receives a router function request message from the R-DEV, and the slave PNC receives a router function allowance request message from the R-DEV. The R-DEV receives by one frame a beacon transmitted from the master PNC. Meanwhile, the R-DEV receives by two frames a beacon transmitted from the slave mater PNC.  
         [0055]      FIG. 9  illustrates a beacon reception period that varies depending on the type of the PNC. The R-DEV receives, per frame, the beacons from the master PNC, and receives every two frames, the beacons from the slave PNC. The R-DEV obtains information on data to be received from the PNCs by use of the beacons. The R-DEV sends to the slave PNC the data received from the master PNC as shown in  FIG. 9 . Since the R-DEV does not receive the beacons transmitted from the slave PNC every frame, the power consumption is reduced.  
         [0056]     Disadvantageously, the R-DEV may receive more data from the slave PNC than from the master PNC. To prevent such a disadvantage, the slave PNC occasionally checks the data amount to be transmitted to the R-DEV. If the data amount to be transmitted exceeds a predetermined amount, exchange of the master PNC and the slave PNC is requested of the R-DEV. Information on the exchange request is conveyed using a certain period of the beacon. Upon receiving the information, the R-DEV exchanges the master and slave PNCs. The beacon reception period of the master PNC is a frame in this embodiment but a user may vary the beacon reception period variously. It should be appreciated that the beacon reception period of the master PNC is shorter than that of the slave PNC.  
         [0057]     In light of the foregoing, in the WPAN including at least two piconets, the DEVs in different piconets are interconnected so that communications are feasible between the piconets. Since some functions of the DEV serving to interconnect the piconets are performed by the other DEVs, power consumption reduces remarkably.  
         [0058]     While the embodiments of the present invention have been described, additional variations and modifications of the embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims shall be construed to include both the above embodiments and all such variations and modifications that fall within the spirit and scope of the invention.