Abstract:
The present invention provides a method for finding a backup node for a node in a sensor network. Firstly, determining a node which is in a state of waiting for being an agent node among a plurality of nodes adjacent to the node to be backed up for using the agent node to find the backup node. The states of waiting for being backed up is that the quantity of electricity of the node to be backed up drops below a preset value. According to the present invention, the node to be backed up does not need to communicate with a large number of nodes. It only needs to determine an agent node among the adjacent notes to do the substantial search for a backup node.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a data network, particularly to a sensor network capable of reasonably managing energy consumption. 
         [0002]    The possible application environments of sensor networks are very extensive, such as physiological monitoring, environmental monitoring (air, water, soil, etc.), condition-triggered maintenance, intelligent space, military uses, stock management, and other work unsuitable for human beings to do. 
         [0003]    A sensor network generally comprises a set or sets of sensors (also referred to as nodes in a sensor network) connected by wire or wireless means for jointly or separately doing specific work. Each sensor of the sensor network normally has one or more of the following functions: inducing, storing, transmitting, relaying, accepting query, triggering events, and processing data, etc. 
         [0004]    Since sensors of the sensor network are small, inexpensive, easy to be disposed and increasingly strong in function, the sensor network becomes more and more popular. But, with these special characteristics mentioned above, the energy use and storage of sensors have increasingly become an important problem. How to maximize the working time of sensors without affecting the efficiency of sensors and sensor networks has become a topic of heated discussion. 
         [0005]    The US patent application (Pub. No. US 2003/0063585A1; applicant: the US Honeywell Inc.; and inventor Mohamed F. Younis) has disclosed a method for managing energy consumption of sensor network. Firstly, dividing the sensors of the sensor network into plurality of groups according to a specific rule, and each group has a sensor acting as a gateway for transmitting data of each sensor to a control node. Then, setting up a route table for each group in a corresponding gateway, and setting up a relatively smaller rout table at each sensor node, so as to consume minimum energy. After that, monitoring the available energy of each sensor. Finally, re-setting up the route table according to the variation of the available energy of each sensor. 
         [0006]    The US patent application has reduced, to a certain extent, energy consumption of each group of sensors. However, each group of sensors has a sensor used as a gateway for coordinating the work of all the sensors in the group, if the gateway is damaged (it is quite possible for it to be damaged under some adverse circumstances), it would greatly affect the efficiency of the group and even the entire sensor network. Further, since the gateway serves as the core of the entire group of sensors, all the sensors need to communicate with the gateway to finish the work, which would inevitably increase the quantity of communication within the group, and, thus, increase the energy consumption of the group, particularly increase the energy consumption of some relay nodes. 
         [0007]    Therefore, both a new sensor network and a new method for managing energy consumption in a sensor network are needed, so as to make it possible for the sensor network to maximize the life of sensors without affecting the efficiency of the sensors and the sensor network. 
       OBJECT AND SUMMERY OF THE INVENTION 
       [0008]    One of the objects of the present invention is to maximize the life of sensors without affecting the efficiency of the sensors and the sensor network, to provide a new sensor, a new sensor network, and a new method for managing energy consumption in a sensor network. 
         [0009]    The present invention has provided a method for finding a backup node for a node within a sensor network. Firstly, determining that the node is in a state to be backed up. Then, determining an agent node among a plurality of nodes adjacent to the node to be backed up, so that the agent node seeks the backup node on behalf of the node to be backed up. Furthermore, the data of the node to be backed up can be transmitted to the backup node. 
         [0010]    One embodiment of the present invention shows that the state to be backed up is that the quantity of electricity of the node to be backed up decreases below a pre-set value, and, then, the node to be backed up itself does not need to communicate with a lot of nodes in order to find for itself a backup node. It needs only to determine an agent node, among the adjacent nodes, to pursue the substantial search of the backup node. Since the agent node is in the vicinity of the node, the determining process will not consume too much energy of the node. Meanwhile, since the node to be backed up does not pursue the substantial search, it further saves energy. Besides, since the finally found backup node is normally somewhere around the node, it would reduce energy consumption for the agent node in the vicinity of the node to be backed up. 
         [0011]    The present invention also provides a sensor is one of a plurality of nodes of a sensor network, and it comprises a detecting means for detecting whether the sensor is waiting to be backed up, and a determining means for determining, when the sensor is to be backed up, an agent node among a plurality of nodes adjacent to the node, so that the agent node seeks the backup node on behalf of the node to be backed up. 
         [0012]    The present invention provides, in addition, a sensor network, and the sensor network comprises a plurality of sensor nodes including a first sensor and a second sensor. The first sensor includes a detecting means for detecting whether the sensor is to be backed up, and a determining means for determining, when the sensor is waiting to be backed up, an agent node among a plurality of nodes adjacent to the node, and requesting the second sensor to find a backup node for it; the second sensor includes a communication means for finding a backup node for the first sensor at the request from the first sensor. 
         [0013]    The other objects and achievements of the present invention will be made more evident and the present invention be more comprehensively understandable by the following description and claims with reference to the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention is explained in detail by way of embodiments and with reference to the drawings, which comprises: 
           [0015]      FIG. 1  is a schematic block view of the components of a sensor according to one embodiment of the present invention; 
           [0016]      FIG. 2  is a schematic view of the system of a sensor network according to one embodiment of the present invention; and 
           [0017]      FIG. 3  is a flow chart of communication of a sensor network according to one embodiment of the present invention. 
       
    
    
       [0018]    The same reference numbers in the figures indicate the similar or identical features and functions. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  is a schematic block view of the components of a sensor according to one embodiment of the present invention. Means  100  includes a communication means  110 , a sensor means  130 , a detecting means  150 , a determining means  160 , and a power supply (not shown in the Fig.). The power supply provides energy needed for the sensor to do its work. It is non-rechargeable or rechargeable. 
         [0020]    Means  100  also includes a storing means  120  and a CPU  140 . 
         [0021]    Means  100  can be a node of a sensor network, in which the functions of some means (e.g. detecting means  150  and determining means  160 ) can be performed through software. As far as those skilled in the art, the means included in means  100  can be realized by a plurality of conventional means as long as their combination can perform the function of the present invention. 
         [0022]    Sensor means  130  is used for inducing the surrounding environment. For example, a particular change in the surrounding environment will trigger a particular function of the sensor. The induced message can be transmitted through communicating means  110  for processing, and also can processed, to an extent, by CPU  140 , and then stored in the storing means  120 ; and, of course, it is also directly stored in the storing means  120 . 
         [0023]    Communicating means  110  is used for transmitting environmental message induced by the sensor, such as message induced by sensor means  130 ; also for transmitting message stored in storing means  120 , which may be relayed from other sensors; the a means is also used for receiving other message received from other sensors, such as an inquiry request. 
         [0024]    Storing means  120  is used for storing message, which may be the environment message induced by the sensor means  130  or message which communicating means  110  receives from other sensors. 
         [0025]    Detecting means  150  is used for detecting whether the sensor is in a state of waiting for being backed up, a state which can be pre-set by a sensor manufacturer or a sensor network system manufacturer. For example, storing means  120  of the sensor has been 80% full, or the quantity of electricity of the sensor has dropped below a pre-set value. 
         [0026]    Determining means  160  is used for determining, when the sensor is a state of waiting for being backed up, an agent node among a plurality of nodes adjacent to the node, so that the agent node seeks the backup node on behalf of the node to be backed up. 
         [0027]    CPU  140  is used for coordinating the work of the other components (e.g. detecting means  150  and determining means  160 ) of the sensor according to the pre-stored commands of the sensor. Of course, the CPU can also process some more complex data if necessary. 
         [0028]      FIG. 2  is a schematic view of the system of a sensor network according to one embodiment of the present invention, and  FIG. 3  is a flow chart of communication of a sensor network according to one embodiment of the present invention. The sensor network comprises a plurality of sensors, including sensor  100 , in which nodes  1 - 9  can communicate (one-hop) with sensor  100 , while multi-hop communication is needed for the other nodes to communicate with sensor  100 . Each sensor in the sensor network has one or more of the following functions: inducing, storing, transmitting, replaying, accepting request, event triggering, and data processing, etc. 
         [0029]    According to  FIGS. 2 and 3 , when sensor  100  detects that it itself is a state of waiting for being backed up, say its quantity of electricity drops to a pre-set value (TH1, for example 25% of its total electricity quantity storage capacity), sensor  100  has found an agent node (AN) among the nodes adjacent to it, it transmits to the agent node a request (M 1 ), requesting it to communicate with the available nodes (ALAN) for finding a backup node (BN) for the sensor  100 . 
         [0030]    The adjacent nodes (NN) may include all nodes that can directly communicate (i.e. one-hop) with sensor  100 . To reduce communication performed for finding the agent node, the agent node may be one of the adjacent nodes that have performed one-hop communication most recently with the sensor  100 . Of course, if sensors are relatively densely distributed within an area, the adjacent nodes may include one that can carry on multi-hop communication with the sensor  100 . 
         [0031]    Request M 1  sent by the sensor  100  may be in the format as follows: 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 Message type sender   Receiver  Content 
               
             
          
           
               
                 M 1 
                 Sensor 100 
                 RN 
                 Function 
                 ALAN 
                 Capability 
               
               
                   
               
             
          
         
       
     
         [0032]    The “function” in the message M 1  is used for indicating the functions of sensor  100 , e.g. temperature inducing, sound inducing and brightness inducing, storing function, etc., and data processing function, etc. 
         [0033]    The “capability” in message M 1  is used for indicating the capabilities and states of the various levels of the functions of sensor  100 , e.g. the capability of inducing key data, the capability of inducing general data, the quantity of the various data stored in the storage, etc. The key data include those nodes which change relatively rapidly, and are more important to decision making. 
         [0034]    “ALAN” in Message M 1  serves as a list of the available backup nodes. The available nodes list may include the nodes in the newest route table  230  of sensor  100  that can perform direct communication (i.e. one-hop), such as nodes  3 - 7 . Of course, the available nodes list may also include the nodes in the new route table  220  (route table  220  becomes route table  230  after it is updated) of sensor  100  that can perform direct communication, such as nodes  1 - 5 . The available nodes list may also include nodes  8  and  9 , and sensor  100  receives message only from nodes  8  and  9 . In this embodiment, the “ALAN” includes nodes  1 - 9 . 
         [0035]    Another ALAN creating method is that sensor  100  sends particular message to all nodes reachable by further communicating, requesting these nodes to reply to determine their availability. These nodes may include inactive nodes, existing as backup nodes. The backup nodes are activated by the particular message to participate in the following discussion organized by the agent node. The discussion mode may be any one of the existing modes. 
         [0036]    Of course, if the sensors are relatively densely distributed within an area, the available nodes may also include those nodes which can perform multi-hop communication with sensor  100 . 
         [0037]    The process for determining the agent node as follows: firstly, the sensor  100  sends request M 1  to a node (RN) of the adjacent nodes (NN). Secondly, the node RN estimates the quantity of electricity needed to perform the searching backup node according to the available nodes list within the request M 1  (ALAN). Thirdly, if the quantity of electricity of node RN is larger than the sum quantity of electricity and a particular threshold value, the node RN sends a confirmation message M 2  to the sensor  100  to indicate that the node (RN) becomes an agent node (AN), otherwise, the RN sends a re-selecting message M 3  to the sensor  100  for requesting sensor  100  to select another node among its adjacent nodes as its agent node. The sensor  100  can repeat the process until an agent node is found among adjacent nodes of the sensor  100 . In this embodiment, node  2  is selected as the agent node for the sensor  100 . 
         [0038]    The confirmation message M 2  sent by node RN may be in the format as follows. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Message type 
                 sender 
                 Receiver 
                 Content 
               
               
                   
                   
               
             
             
               
                   
                 M2 
                 RN 
                 Sensor 100 
                 Confirmation: AN 
               
               
                   
                   
               
             
          
         
       
     
         [0039]    The re-selecting message M 3  sent by node RN may be in the format as follows. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Message type 
                 Sender 
                 Receiver 
                 Content 
               
               
                   
                   
               
             
             
               
                   
                 M3 
                 RN 
                 Sensor 100 
                 Re-selecting AN 
               
               
                   
                   
               
             
          
         
       
     
         [0040]    After node  2  is selected as an agent node of sensor 100 , a discussion is organized in all the available nodes according to the ALAN list for selecting a suitable backup node. The discussion mode may be any one of the existing modes of discussion. The basic principle is to consider whether the function, capability and quantity of electricity of the available node of the candidate backup nodes can replace sensor  100 . At the beginning of the discussion, node  2  may send a message M 4  to node  1  and nodes  3 - 9  to inform them the function and capability of sensor  100 . During the whole discussion, avoid the sensor  100  if multi-hop communication is needed among the nodes participating in the discussion. 
         [0041]    Message M 4  sent by node AN may be in the format as follows: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                 Message type 
                 Sender 
                 Receiver 
                 Content 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 M4 
                 AN 
                 ALAN 
                 Function of 
                 Capability of 
               
               
                   
                   
                   
                 sensor 100 
                 sensor 100 
               
               
                   
               
             
          
         
       
     
         [0042]    After discussion, node  4  is determined as the backup node (BN)) of sensor  100 . Of course, the result of the discussion may also determining of any other available qualified node (including node  2 ) as the backup node of sensor  100 . 
         [0043]    Then, node  4  sends a message M 5  to sensor  100  for requesting the function and/or data of sensor  100 , e.g. temperature inducing function of sensor  100 . 
         [0044]    Message M 5  sent by backup node (BN, node  4 ) may be in the format as follows: 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                 Message type 
                 Sender 
                 Receiver 
                 Content 
               
               
                   
               
             
             
               
                 M5 
                 BN 
                 Sensor 100 
                 Requesting backup data/function 
               
               
                   
               
             
          
         
       
     
         [0045]    Upon receiving message M 5  sent from node  4 , sensor  100  sends the data and/or function to the node  4  to be backed up, and puts itself in a power-saving state. The sending process may also be done in two steps. In the first step, the general data and/or function are transferred to backup node (BN, node  4 ), and when the quantity of electricity of sensor  100  further drops to a lower lever, the key data and/or function are transferred to the backup node (BN, node  4 ). 
         [0046]    After the backup, sensor  100  no longer induces the temperature variation, and node  4  performs sensor  100 &#39;s temperature inducing instead. 
         [0047]    Finally, agent node (AN, node  2 ) or backup node (BN, node  4 ) may also send a notice message M 6  to the nodes (e.g. available nodes ALAN) that has communicated with sensor  100 , informing it that sensor  100  is in a power-saving state and that its function and/or data are processed by the backup node (BN, node  4 ), so that it could adopt corresponding measures, such as one for updating their route table. 
         [0048]    Message M 6  sent by agent node (AN, node  2 ) may be in the format as follows: 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                 Message type 
                 Sender 
                 Receiver 
                 Content 
               
               
                   
               
             
             
               
                 M6 
                 AN 
                 ALAN 
                 Sensor 100 has been backed up by 
               
               
                   
                   
                   
                 BN (node 4) 
               
               
                   
               
             
          
         
       
     
         [0049]    If the sensor network has a control center, the agent node (AN, node  2 ) or backup node (BN, node  4 ) may also send a notice message M 7  to the control center for informing the control center that sensor  100  is in a power-saving state and that its function and/or data are to be processed by the backup node (BN, node  4 ). 
         [0050]    Message M 7  sent by agent node (AN, node  2 ) may be in the format as follows: 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                 Message type 
                 Sender 
                 Receiver 
                 Content 
               
               
                   
               
             
             
               
                 M7 
                 AN 
                 Control center 
                 Sensor 100 has been backed 
               
               
                   
                   
                   
                 up by BN (node 4) 
               
               
                   
               
             
          
         
       
     
         [0051]    In a sensor network, various nodes may be of different level of importance. By virtue of the present invention, the nodes of minor importance may seek a backup node for a node of importance, so as to reduce the communication burden of the node of importance and prolong their life of performance. Of course, every node may be selected to be as a backup node by an adjacent node according to given principles. 
         [0052]    The present invention has been described above in combination with the embodiments. It is evident that those skilled in the art can obviously make all sorts of substitutions, modifications and changes on the basis of what has been described above. For that matter, all substitutions, modifications and changes of the nature should be in the spirit, and fall within the scope, of the claims of the present invention.