Abstract:
The present invention is to provide a method and apparatus for multiplexing a sync node and a gateway of a wireless sensor network, which is capable of allowing communication of the wireless sensor network to be normally performed by multiplexing paths of the sync node and the gateway of the wireless sensor network even in the case where any one of the sync node and the gateway abnormally operates and by transmitting upstream data and downstream data through a path selected among the duplexed paths according to characteristics of the wireless sensor network.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2010-0124632, filed on Dec. 8, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wireless sensor network, and more particularly, to a path multiplexing apparatus in a wireless sensor network. 
     2. Description of the Prior Art 
     Referring to  FIG. 1 , a wireless sensor network (WSN) may be configured to include: a sensor field  100  which includes a group of sensor nodes; a sync node  102  which transmits upstream data which are information collected by the sensor nodes of the sensor field  100  to a gateway  104  and transmits downstream data from the gateway  104  to the sensor nodes of the sensor field  100 ; and a gateway  104  which routes the upstream data which are information transmitted from the sync node  102  to transmit the upstream data to a server  106  through a wide band communication network and transmits the downstream data from the server  106  to the sync node  102 . 
     As described above, in the wireless sensor network, the upstream data from the sensor nodes of the sensor field  100  are transmitted to the server  106  through a single path formed by the sync node  102  and the gateway  104 , and the downstream data from the server  106  are also transmitted to the sensor nodes of the sensor field  100  through the single path formed by the sync node  102  and the gateway  104 . 
     In this manner, since only the single path exists between the sensor field  100  including a plurality of the sensor nodes and the server  106 , in the case where one of the sync node  102  and the gateway  104  abnormally operates, there is a problem in that the entire wireless sensor network fails to operate. 
     SUMMARY OF THE INVENTION 
     The present invention is to provide a method and apparatus for multiplexing a sync node and a gateway of a wireless sensor network, which is capable of allowing communication of the wireless sensor network to be normally performed by multiplexing paths of the sync node and the gateway of the wireless sensor network even in the case where any one of the sync node and the gateway abnormally operates and by transmitting upstream data and downstream data through a path selected among the duplexed paths according to characteristics of the wireless sensor network. 
     According to an aspect of the present invention, there is provided a path multiplexing apparatus in a wireless sensor network including: a master apparatus; a slave apparatus; and a control module, wherein the control module selectively transmits any one of data supplied by the master apparatus and the slave apparatus to a next system according to control signals supplied by the master apparatus and the slave apparatus, wherein in an activated state, the master apparatus supplies a control signal for allowing data of the master apparatus to be output and monitors an operation state of the slave apparatus, and in the case where the slave apparatus abnormally operates, the master apparatus supplies a reset signal to the slave apparatus, and wherein in an inactivated state, the slave apparatus monitors an operation state of the master apparatus, and in the case where the master apparatus abnormally operates, the slave apparatus is transitioned into an activated state to supply a reset signal to the master apparatus and supply a control signal for allowing data of the slave apparatus to be output to the control module. 
     According to the present invention, even in the case where any one of the sync node and the gateway of the wireless sensor network abnormally operates, it is possible to allow the communication of the wireless sensor network to be normally performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of a conventional wireless sensor network. 
         FIG. 2  is a diagram illustrating a configuration of a wireless sensor network according to an embodiment of the present invention. 
         FIG. 3  is a diagram illustrating a configuration of a path multiplexing apparatus according to an embodiment of the present invention. 
         FIG. 4  is a diagram illustrating a detailed configuration of a control module of  FIG. 3 . 
         FIG. 5  is a table listing functions of control signals according to an embodiment of the present invention. 
         FIG. 6  is a flowchart illustrating processes of a master apparatus according to an embodiment of the present invention. 
         FIG. 7  is a flowchart illustrating processes of a slave apparatus according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the present invention, even in the case where any one of a sync node and a gateway abnormally operates, communication of a wireless sensor network is allowed to be normally performed by duplexing paths of the sync node and the gateway of the wireless sensor network. 
     [Configuration of Wireless Sensor Network] 
     The configuration of the wireless sensor network according to an embodiment of the present invention will be described with reference to  FIG. 2 . 
     The wireless sensor network is configured to include: a sensor field  200  which includes a group of sensor nodes; a master sync node  202  and a slave sync node  204  which receive upstream data from the sensor nodes of the sensor field  200  to transmit the upstream data to a sync node control module  206 , receive downstream data from a gateway control module  208  to transmit the downstream data to the sensor nodes of the sensor field  200 , and transmits a control signal to the sync node control module  206 ; a sync node control module  206  which receives the control signal and the upstream data from the master sync node  202  and the slave sync node  204  and selects the upstream data from any one of the master sync node  202  and the slave sync node  204  to transmit the upstream data to the master gateway  210  and the slave gateway  212 ; a master gateway  210  and a slave gateway  212  which receives the upstream data from the sync node control module  206  to transmit the upstream data to a server  214 , receives the downstream data from the server  214  to transmit the upstream data to the gateway control module  208 , and transmits the control signal to the gateway control module  208 ; and a gateway control module  208  which receives the control signal and the downstream data from the master gateway  210  and the slave gateway  212  and selects the downstream data from any one thereof to transmit the downstream data to the master sync node  202  and the slave sync node  204 . 
     [Configuration of Duplexing Apparatus] 
     The configuration of the path duplexing apparatus according to an embodiment of the present invention will be described in detail with reference to  FIG. 3 . 
     [Path Duplexing Apparatus for Gateway] 
     The path duplexing apparatus for a gateway according to the present invention includes a master gateway  210 , a slave gateway  212 , and a gateway control module  208 . 
     First, the upstream data are input to each of the master gateway  210  and the slave gateway  212 . The upstream data are transmitted to the server as the next system by an activated gateway among the master gateway  210  and the slave gateway  212 . 
     In addition, the gateway control module  208  selectively outputs the downstream data from an activated gateway among the master gateway  210  and the slave gateway  212  to transmit the downstream data to the sync node as the next system. 
     During the normal operation, the master gateway  210  periodically supplies a first active signal to the slave gateway  212  to inform that the master gateway  210  normally operates, and the master gateway  210  monitors a second active signal from the slave gateway  212  to check whether or not the slave gateway  212  normally operates. In the case where it is determined that the slave gateway  212  does not normally operate, the master gateway  210  supplies a second reset signal to the slave gateway  212  to reset the slave gateway  212 . 
     In addition, during the normal operation, the master gateway  210  is selectively activated according to the operation state of the slave gateway  212  to output the upstream data and the downstream data received by the master gateway  210 . Particularly, the master gateway  210  supplies a control signal (K, /CLR) for allowing the downstream data received by the master gateway  210  to be selectively output according to the state thereof and the downstream data to the gateway control module  208 . 
     Next, the master gateway  210  is reset according to a first reset signal supplied by the slave gateway  212 . 
     In addition, during the normal operation, the slave gateway  212  periodically supplies the second active signal to the master gateway  210  to inform that the slave gateway  212  normally operates, and the slave gateway  212  monitors the first active signal from the master gateway  210  to check whether or not the master gateway  210  normally operates. In the case where it is determined that the master gateway  210  does not normally operates, the slave gateway  212  supplies the first reset signal to the master gateway  210  to reset the master gateway  210 . 
     In addition, during the normal operation, the slave gateway  212  is selectively activated according to the operation state of the master gateway  210  to output the upstream data and the downstream data received by the slave gateway  212 . Particularly, the slave gateway  212  supplies a control signal (J, /PRE) for allowing the downstream data received by the slave gateway  212  to be selectively output according to the state thereof and the downstream data to the gateway control module  208 . 
     Next, the slave gateway  212  is reset according to a second reset signal supplied by the master gateway  210 . 
     [Path Duplexing Apparatus for Sync Node] 
     The path duplexing apparatus for a sync node according to the present invention includes a master sync node  202 , a slave sync node  204 , and a sync node control module  206 . 
     First, the downstream data are input to each of the master sync node  202  and the slave sync node  204 . The downstream data are transmitted to the sensor nodes of the sensor field  200  as the next systems by an activated sync node among the master sync node  202  and the slave sync node  204 . 
     In addition, the upstream data are input to each of the master sync node  202  and the slave sync node  204 . The upstream data are supplied to the sync node control module  206 , and the sync node control module  206  transmits the upstream data to the master gateway  210  and the slave gateway  212  as the next systems by an activated sync node among the master sync node  202  and the slave sync node  204 . 
     During the normal operation, the master sync node  202  periodically supplies the first active signal to the slave sync node  204  to inform that the master sync node  202  normally operates, and the master sync node  202  monitors the second active signal from the slave sync node  204  to check whether or not the slave sync node  204  normally operates. In the case where it is determined that the slave sync node  204  does not normally operates, the master sync node  202  supplies the second reset signal to the slave sync node  204  to reset the slave sync node  204 . 
     In addition, during the normal operation, the master sync node  202  is selectively activated according to the operation state of the slave sync node  204  to output the upstream data and the downstream data received by the master sync node  202 . Particularly, the master sync node  202  supplies a control signal (K, /CLR) for allowing the upstream data thereof to be selectively output according to the state thereof and the upstream data to the sync node control module  206 . 
     Next, the master sync node  202  is reset according to the first reset signal supplied by the slave sync node  204 . 
     In addition, during the normal operation, the slave sync node  204  periodically supplies the second active signal to the master sync node  202  to inform that the slave sync node  204  normally operates, and the slave sync node  204  monitors the first active signal from the master sync node  202  to check whether or not the master sync node  202  normally operates. In the case where it is determined that the master sync node  202  does not normally operates, the slave sync node  204  supplies the first reset signal to the master sync node  202  to reset the master sync node  202 . 
     In addition, during the normal operation, the slave sync node  204  is selectively activated according to the operation state of the master sync node  202  to output the upstream data and the downstream data received by the slave sync node  204 . Particularly, the slave sync node  204  supplies a control signal (J, /PRE) for allowing the upstream data received by the slave sync node  204  to be selectively output according to the state thereof and the upstream data to the sync node control module  206 . 
     Next, the slave sync node  204  is reset according to the second reset signal supplied by the master sync node  202 . 
     [Configuration of Control Module] 
     Since the configuration and operations of the gateway control module  208  are the same as those of the sync node control module  206 , only the configuration and operations of one control module will be described in detail. 
     Referring to  FIG. 4  illustrating the configuration of the control module according to the present invention, the control module includes an oscillator  400 , a JK flip-flop  402 , and a MUX  404 . The oscillator  400  supplies a driving clock of the JK flip-flop  402 . The JK flip-flop  402  receives control signals from the master apparatus  300  through /CLR and K ports and receives control signals from the slave apparatus  302  through /PRE and J ports to output an output Q as a selection signal of the MUX  404 . The MUX  404  selectively outputs the data from the master apparatus or the slave apparatus according to the selection signal output from the JK flip-flop  402 . In other words, in the case where the control module is the gateway control module  208 , the MUX  404  selectively outputs one of the downstream data supplied by the master gateway  210  and the slave gateway  212 . In the case where the control module is the sync node control module  206 , the MUX  404  selectively outputs one of the upstream data supplied by the master sync node  202  and the slave sync node  204 . 
     [Control Signal and Output State of Control Module] 
     The operation of the control module and the output states of the MUX  404  with respect to the control signals will be described with reference to  FIG. 5 . 
     First, the first operation state denotes a state where the master apparatus is activated and the slave apparatus is inactivated in the state where the master apparatus and the slave apparatus normally operate. In this case, the master apparatus supplies an H signal through the K port and supplies the H signal through the /CLR port, and the slave apparatus supplies an L signal through the J port and supplies the H signal through the /PRE port. Therefore, the JK flip-flop  402  is allowed to output a selection signal L. In this case, the MUX  404  selectively outputs the data from the master apparatus according to the selection signal L. 
     Next, the second operation state denotes a state where the activated master apparatus abnormally operates, so that the slave apparatus inactivated in the normal operation state becomes activated. In this case, the master apparatus supplies an X signal through the K port and supplies the X signal through the /CLR port, and the slave apparatus supplies the H signal through the J port and supplies the L signal through the /PRE port. Therefore, the JK flip-flop  402  is allowed to output a selection signal H. In this case, the MUX  404  selectively outputs the data from the slave apparatus according to the selection signal H. Herein, the X signal denotes an H signal or an L signal. 
     Next, the third operation state denotes a state where the master apparatus which abnormally operates is reset by the first reset signal from the slave apparatus to be allowed to normally operate but it is transitioned into an inactivated state and the slave apparatus is maintained in the activated state. In this case, the master apparatus supplies the L signal through the K port and supplies the H signal through the /CLR port, and the slave apparatus supplies the H signal through the J port and supplies the H signal through the /PRE port. Therefore, the JK flip-flop  402  is allowed to output the selection signal H. In this case, the MUX  404  selectively outputs the data from the slave apparatus according to the selection signal H. 
     Next, the fourth operation state denotes a state where the activated slave apparatus abnormally operates, so that the master apparatus which normally operates and is inactivated is transitioned into an activated state. In this case, the master apparatus supplies the H signal through the K port and supplies the L signal through the /CLR port, and the slave apparatus supplies the X signal through the J port and supplies the X signal through the /PRE port. Therefore, the JK flip-flop  402  is allowed to output the selection signal L. In this case, the MUX  404  selectively outputs the data from the master apparatus according to the selection signal L. 
     As described above, the control modules selectively output any one of the data from the master apparatus and the slave apparatus according to the control signals supplied by the master apparatus and the slave apparatus. 
     Now, a process where the master apparatus and the slave apparatus supply different control signals according to the operation states will be described in detail. Herein, the master apparatus denotes the master sync node  202  or the master gateway  210 , and the slave apparatus denotes the slave sync node  204  or the slave gateway  212 . 
     [Operation of Master Apparatus] 
     Operations of the master apparatus are described with reference to  FIG. 6 . 
     After the master apparatus is reset (Step S 500 ), the master apparatus proceeds into an activated state to output a control signal (K port: H, /CLR port: H) so that the data of the master apparatus are output (Step S 502 ). In this case, after the slave apparatus is also reset, the slave apparatus outputs a control signal (J port: L, /PRE port: H) so that the data of the master apparatus are selectively output. 
     In this state, the master apparatus checks whether or not the master apparatus normally operates (Step S 504 ). If it is determined that the master apparatus normally operates, the master apparatus monitors the reception state of the second active signal in order to check whether or not the slave apparatus normally operates while outputting the first active signal with a predetermined period (Step S 506 ). 
     If it is determined that the second active signal is not normally received (Step S 508 ), the master apparatus transmits the second reset signal to the slave apparatus and outputs the control signal (K port: H, the /CLR port: L) so that the data of the master apparatus are output (Step S 510 ). 
     If it is determined that the master apparatus does not normally operates, the master apparatus cannot output the first active signal (Step S 512 ). In this case, the abnormal operation of the master apparatus is sensed by the slave apparatus which monitors the first active signal, so that the first reset signal is supplied to the master apparatus. 
     If the first reset signal is received, the master apparatus performs resetting. If the normal operation is performed due to the resetting, the master apparatus proceeds into an inactivated state to output the first active signal with a predetermined period and to change the control signal (K port: L, /CLR port: H) so that the data of the slave apparatus are output, and the master apparatus monitors the reception state of the second active signal of the slave apparatus (Step S 522 ). 
     If the second active signal is not normally received, the master apparatus proceeds into an activated state to change the control signal (K port: H, /CLR port: L) so that the data of the master apparatus are output and to transmits the second reset signal to the slave apparatus (Step S 526 ). 
     After the second reset signal is transmitted, the master apparatus checks the reception state of the second active signal (Step S 528 ). If the reception state of the second active signal is normal, the master apparatus determines that the slave apparatus normally operates and changes the control signal (K port: H, /CLR port: H) for the control module according to the control signal (the J port: L, /PRE port: H) of the slave apparatus which is reset to be in the inactivated state so that the data of the master apparatus are output (Step S 530 ). 
     [Operation of Slave Apparatus] 
     Now, operations of the slave apparatus are described with reference to  FIG. 7 . 
     After the slave apparatus is reset (Step S 600 ), the slave apparatus proceeds into an inactivated state to output a control signal (J port: L, /PRE: H) so that the data of the master apparatus are output (Step S 602 ). In this case, after the master apparatus is also reset, the master apparatus outputs a control signal (K port: H, /CLR port: H) so that the data of the master apparatus are selectively output. 
     Next, the slave apparatus checks whether or not the slave apparatus normally operates (Step S 604 ). If it is determined that the slave apparatus normally operates, the slave apparatus monitors the first active signal of the master apparatus while outputting the second active signal with a predetermined period (Step S 616 ). 
     If it is determined that the slave apparatus does not normally operates, the slave apparatus cannot output the second active signal (Step S 606 ). In this case, the abnormal operation is sensed by the master apparatus which monitors the second active signal, so that the second reset signal is supplied to the slave apparatus. 
     If the second reset signal is received (Step S 608 ), the slave apparatus performs resetting (Step S 610 ). If the normal operation is performed due to the resetting (Step S 612 ), the slave apparatus is inactivated to output the second active signal with a predetermined period and to change the control signal (J port: L, /PRE: H) so that the data of the master apparatus are output, and the slave apparatus monitors the operation state of the master apparatus based on the reception state of the first active signal of the master apparatus (Steps S 602 , S 604 , and S 616 ). 
     During the time when the slave apparatus monitors the reception state of the first active signal while outputting the second active signal with a predetermined period (Step S 616 ), if the first active signal is not normally received, the slave apparatus determines that the master apparatus abnormally operates (Step S 618 ), and the slave apparatus proceeds into an activated state to change the control signal (J port: H, /PRE: L) so that that data of the slave apparatus are output and to transmit the first reset signal to the master apparatus, and the slave apparatus monitors whether or not the first active signal of the master apparatus is normally received (Steps S 620  and S 622 ). 
     After the first reset signal is transmitted, if the slave apparatus normally receives the first active signal, the slave apparatus determines that the master apparatus normally operates. After that, in the case where the slave apparatus is in an abnormal state, in order to allow the data of the master apparatus to be output at the same time when the slave apparatus is reset by the master apparatus, the slave apparatus changes the control signal (J port: H, /PRE port: H) for the control module (Step S 626 ).