Abstract:
A method and system of enhancing an operational lifetime of a wireless network is provided, which includes monitoring a link quality between node elements of the wireless network, periodically collecting information regarding the link quality between node elements of the wireless network, and reconfiguring a network topology of the wireless network based on the collected information.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is related to U.S. patent applications entitled “Method and System for Time Synchronization in Communication Networks”(Attorney Docket No. 11403/5501), “Method and System for Providing Acknowledged Broadcast and Multicast Communication” (Attorney Docket No. 11403/5502), “Method and System for Providing an Energy Efficient Exchange of Information in Wireless Networks” (Attorney Docket No. 11403/5503), “Method and System for Providing Interference Avoidance and Network Coexistence in Wireless Systems” (Attorney Docket No. 11403/5504), “Method and System for Reliable Data Transmission in Wireless Networks” (Attorney Docket No. 11403/5505), “Method and System to Reduce Delay and/or Energy Consumption in a Multi-Hop Wireless System” (Attorney Docket No. 11403/5506), “Method and System for Providing a Modified Time Division Multiple Access (TDMA) for Reduced Delay” (Attorney Docket No. 11403/5507), “Method and System for Providing Reliable Communication with Redundancy for Energy Constrained Wireless Systems” (Attorney Docket No. 11403/5508), “Method and System to Reconfigure a Network to Improve Network Lifetime Using Most Reliable Communication Links” (Attorney Docket No. 11403/5510). The disclosure of each of the foregoing related applications is hereby incorporated by reference herein in its entirety. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to a method and system for reconfiguring a communications network, including, for example, a wireless communications network, to improve network lifetime using the most reliable communication links.  
       BACKGROUND INFORMATION  
       [0003]     In wireless systems, it may be more energy efficient to use reliable links for communication, particularly, when mounting network node elements in ad-hoc wireless communications networks.  
         [0004]     Battery operated wireless systems may communicate more if reliable links are used because such links may reduce errors in the communication, lost communications, retries, etc. The quality of the wireless links, however, may change dynamically and may also depend on environmental changes. In particular, the link quality may change significantly over time due to, for example, newly deployed system elements, new systems deployed that use the same wireless channel, or movement of physical obstacles (e.g., furniture or metal cabinets in offices), etc.  
         [0005]     The 23 rd  Conference of the International Electronic and Electrical Engineers (IEEE) Communications Society held in Hong Kong Mar. 7 to 11, 2004 (Infocom 2004) proposed an Optical Orthoganl Codeword (OOC) scheme to gather link quality, for an energy-efficient system in a purportedly very energy-efficient manner.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides a method and system for reconfiguring a communications network, including, for example, a wireless communications network, to improve network lifetime using the most reliable communication links.  
         [0007]     An exemplary embodiment and/or exemplary method of the present invention may periodically update the link quality information of a wireless communications network, and based on this information make changes to the network topology (if required) to improve, enhance and/or prolong the network life.  
         [0008]     According to an exemplary embodiment and/or exemplary method of the present invention, certain quality characteristics of the wireless links are collected periodically and the network topology of wireless nodes is changed (if required) so that the most reliable links are used. Consequently, errors in communication may be reduced, lost communications or retransmissions may be minimized, and longer uninterrupted communications may be achieved.  
         [0009]     An exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, the method including monitoring a link quality between node elements of the wireless network, periodically collecting information regarding the link quality between node elements of the wireless network, and reconfiguring a network topology of the wireless network based on the collected information.  
         [0010]     Another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, in which the information regarding the link quality includes a measured signal strength.  
         [0011]     Yet another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, in which the information regarding the link quality includes an error rate.  
         [0012]     Still another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, in which the information regarding the link quality includes an retransmission rate.  
         [0013]     Yet another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, in which the network topology is reconfigured so that a link quality of an established communication path between the node elements is maximized.  
         [0014]     Still another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, in which the established communication path is a preferred established communication path.  
         [0015]     Yet another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, the method including detecting a shift in an adverse environmental condition that affects the link quality between node elements of the wireless network.  
         [0016]     Still another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, the method including detecting a change in node elements of the wireless network, and updating the collected information based on the detected change in node elements.  
         [0017]     Yet another exemplary embodiment and/or exemplary method of the present invention is directed to a method of enhancing an operational lifetime of a wireless network, in which at least one node element of the wireless network is energy constrained.  
         [0018]     An exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, which includes a plurality of network node elements configured to communicate via communication links arranged accordingly to a network topology, an arrangement to monitor a link quality between each of the plurality of network node elements, an arrangement to periodically collect information regarding a link quality of the communication links, and an arrangement to reconfigure the network topology based on the collected information.  
         [0019]     Another exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, in which at least one of the plurality of network elements is battery operated.  
         [0020]     Yet another exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, in which the information regarding the link quality of the communication links include at least one of a measured signal strength, an error rate, and a retransmission rate.  
         [0021]     Still another exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, in which the network topology is reconfigured so that a link quality of an established communication path between the node elements is maximized.  
         [0022]     Yet another exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, in which the established communication path is a preferred established communication path.  
         [0023]     Still another exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, which includes an arrangement to detect a shift in an adverse environmental condition that affects the link quality between at least two of the plurality of network node elements.  
         [0024]     Another exemplary embodiment and/or exemplary method of the present invention is directed to a wireless network, which includes an arrangement to detect a change in the plurality of network node elements, and an arrangement to update the collected information based on the detected change of the plurality of network node elements.  
         [0025]     An exemplary embodiment and/or exemplary of the present invention is directed to a method of improving an operational aspect of a wireless network, the method including monitoring a reliability of a communication path between each of a plurality of devices of the wireless network, periodically collecting information regarding the reliability of the communication links, and reconfiguring a network topology of the wireless network based on the collected information so that an expected reliability of an established communication path between the plurality of devices is maximized. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  shows an exemplary wireless network that includes a base station and seven network nodes, and an adverse environmental condition located within the exemplary wireless network.  
         [0027]      FIG. 2  shows an exemplary network topology for the exemplary wireless network of  FIG. 1  prior to reconfiguration of network topology, in which the devices of the exemplary wireless network are arranged according to a predetermined preference for communicating with each other.  
         [0028]      FIG. 3  shows the exemplary wireless network of  FIG. 1  having undergone a change in link quality between network devices, which resulted from a shifting of the adverse environmental condition within the exemplary wireless network.  
         [0029]      FIG. 4  shows an exemplary network topology for the exemplary wireless network of  FIG. 2 , which underwent a reconfiguration to accommodate the change in link quality between the first node and the fifth node, and the change in link quality between the base station and the sixth and seventh nodes.  
         [0030]      FIG. 5  shows an exemplary method of enhancing an operational lifetime of the exemplary wireless network of  FIG. 1 , in which the network topology of the exemplary wireless network is changed to accommodate changing network conditions so that the most reliable links between the nodes are used. 
     
    
     DETAILED DESCRIPTION  
       [0031]      FIG. 1  shows an exemplary wireless network  100 , which includes a base station BS, a first node  101 , a second node  102 , a third node  103 , a fourth node  104 , a fifth node  105 , a sixth node  106 , and a seventh node  107 . In this regard, the base station BS and seven network nodes  101  through  107  may be referred collectively as the “devices” of the exemplary wireless network  100 . Here, it is assumed that at least some of the devices of the exemplary wireless network  100  are capable of communicating with each other, and measuring characteristics of a communications channel between devices. In particular, it is assumed that at least some of the devices of the exemplary wireless network  100  can measure a link quality between the base station BS and neighboring nodes, or between the nodes themselves. It is also assumed that at least some of the devices of the exemplary wireless network  100  are capable of determining a preferred communication path to communicate with other devices.  
         [0032]      FIG. 1  further shows an adverse environmental condition  999  existing within the exemplary wireless network  100 . In particular,  FIG. 1  shows the adverse environmental condition  999  existing between the base station BS and the seventh node  107 , and between the base station BS and the sixth node  106 , which may prevent the establishment of a reliable link between the base station BS and the seventh node  107  or between the base station BS and the sixth node  106 . In this regard, the environmental condition may be, for example, a physical object that blocks the signal path between the base station BS and the seventh node  107 , and between the base station BS and the sixth node  106 .  
         [0033]      FIG. 2  shows an exemplary network topology  150 A for the exemplary wireless network  100  of  FIG. 1  prior to a reconfiguration of the network topology  150 A, in which the devices of the exemplary wireless network  100  are arranged according to predetermined preference for communicating with each other. In particular, the exemplary network topology  150 A shows the devices of the exemplary wireless network  100  arranged in a hierarchical manner to indicate a preferred path of communication between the devices. In this regard, a line between two devices indicates that a preferred communications link is established. For example, the line displayed between the base station BS and the first node  101  indicates a preferred communication link is established between the base station BS and the first node  101 , and the line displayed between the first node  101  and the fifth node  105  indicates that a preferred communication link is established between the first node  101  and the fifth node  105 . Accordingly, if the base station BS and the first node  101  wish to communicate with each other, they simply send a message directly to one another. Likewise, if the first node  101  and the fifth node  105  wish to communicate with each other, they too simply send a message directly to one another.  
         [0034]     It is noted, however, that a line is not displayed between the base station BS and the fifth node  105 . Accordingly, if the base station BS or the fifth node  105  wish to communicate with each other, they must communicate indirectly via the first node  101 . That is, if the base station BS wishes to communicate a message to the fifth node  105 , the base station BS sends the message intended for the fifth node  105  to the first node  101  via the preferred communication link established between the base station BS and the first node  101 , and the first node  101  upon receiving the message intended for the fifth node  105  forwards the message to the fifth node  105  via the preferred communication link established between the first node  101  and the fifth node  105 . Likewise, if the fifth node  105  wishes to communicate a message to the base station BS, the fifth node  105  sends the message intended for the base station BS to the first node  101  via the preferred communication link established between the fifth node  105  and the first node  101 , and the first node  101  upon receiving the message intended for the base station BS forwards the message to the base station BS via the preferred communication link established between the first node  101  and the base station BS. Hence, the base station BS and the fifth node  105  do not communicate their messages directly, but rather indirectly via the first node  101 . It is noted here that the base station BS and the fifth node  105  communicate indirectly via the first node  101 , even if it is possible to established a direct communication link between the base station BS and the fifth node  105 , since it has been previously determined that if a communication link were established between the base station BS and the fifth node  105 , such a communication link was considered to be unacceptably reliable.  
         [0035]     As a further example of the hierarchically arranged network topology  150 A indicating the preferred path of communication, the line displayed between the base station BS and the third node  103  indicates that a preferred communication link is established between the base station BS and the third node  103 , the line displayed between the third node  103  and the sixth node  106  indicates that a preferred communication link is established between the third node  103  and the sixth node  106 , and the line displayed between the sixth node  106  and the seventh node  107  indicates that a preferred communication link is established between the sixth node  106  and the seventh node  107 . Accordingly, if the base station BS and the third node  103  wish to communicate with each other, they simply send a message directly to one another. Likewise, if the third node  103  and the sixth node  106  wish to communicate with each other, they too simply send a message directly to one another. Likewise still, if the sixth node  106  and the seventh node  107  wish to communicate with each other, they too simply send a message directly to one another.  
         [0036]     It is noted, however, that a line is not displayed between the third node  103  and the seventh node  107 , and that a line is not displayed between the base station BS and the sixth node  106  or between the base station BS and the seventh node  107 . Accordingly, if the base station BS and the seventh node  107  wish to communicate with each other, they must communicate indirectly via the third node  103  and the sixth node  106 . That is, if the base station BS wishes to communicate a message to the seventh node  107 , the base station BS sends the message intended for the seventh node  107  to the third node  103  via the preferred communication link established between the base station BS and the third node  103 , and the third node  103  upon receiving the message intended for the seventh node  107  forwards the message to the sixth node  106  via the preferred communication link established between the third node  103  and the sixth node  106 , and the sixth node  106  upon receiving the message intended for the seventh node  107  forwards the message to the seventh node  107  via the preferred communication link established between the sixth node  106  and the seventh node  107 . Likewise, if the seventh node  107  wishes to communicate a message to the base station BS, the seventh node  107  sends the message intended for the base station BS to the sixth node  106  via the preferred communication link established between the seventh node  107  and the sixth node  106 , and the sixth node  106  upon receiving the message intended for the base station BS forwards the message to the third node  103  via the preferred communication link established between the sixth node  106  and the third node  103 , and the third node  103  upon receiving the message intended for the base station BS forwards the message to the base station BS via the preferred communication link established between the third node  103  and the base station BS. Hence, the base station BS and the seventh node  107  do not communicate their messages directly, but rather indirectly via the third node  103  and the sixth node  106 .  
         [0037]     It is also noted that the base station BS and the sixth node  106  communicate indirectly via the third node  103 , despite the relatively close physical arrangement, due to, for example, the existence of the adverse environmental condition  999  arranged between the base station BS and the sixth node  106 , which prevents the establishment of a reliable link between the base station BS and the sixth node  106 . Likewise, the base station BS and the seventh node  107  communicate indirectly via the third node  103  and the sixth node  106  despite the relatively close physical arrangement due to, for example, the existence of the same adverse environmental condition  999 , which is also arranged between the base station BS and the seventh node  107  and therefore prevents the establishment of a reliable link between the base station BS and the seventh node  107 . It is also noted here that the adverse environmental condition  999  may be transitory. That is, the adverse environmental condition  999  may disappear or shift to a new location within the exemplary wireless network  100 .  
         [0038]      FIG. 3  shows the exemplary wireless network  100  of  FIG. 1  having undergone a change in link quality between network devices, which resulted from a shifting of the adverse environmental condition  999  within the exemplary wireless network  100 . In particular, the adverse environmental condition  999  shifted from being arranged between the base station BS and the sixth and seventh nodes  106 / 107  to being arranged between the first node  101  and the fifth node  105 , which affected the link quality between the base station BS and the sixth and seventh node  106 / 107 , and also the link quality between the first node  101  and the fifth node  105 . In particular, with the change in adverse environmental condition  999 , an improved link quality characteristics may be detected between the base station BS and the sixth node  106 , and between the base station BS and the seventh node  107 . Moreover, with the change in adverse environmental condition  999 , poorer link quality characteristics may be detected between the first node  101  and the fifth node  105 . In this regard, the change in link quality was detected, for example, by a periodic collection of information regarding certain quality characteristics of the wireless links between the devices so that based on this collected information, the network topology of wireless nodes may be configured such that the most reliable links between the nodes are used.  
         [0039]      FIG. 4  shows an exemplary network topology  150 B for the exemplary wireless network  100  of  FIG. 2 , which underwent a reconfiguration to accommodate the change in link quality between the first node  101  and the fifth node  105 , and the change in link quality between the base station BS and the sixth and seventh nodes  106 / 107 . In particular, the exemplary network topology  150 B also shows that the line previously displayed between the first node  101  and the fifth node  105  is now removed indicating that a preferred communication link is no longer established directly between the first node  101  and the fifth node  105 , and that a line was added between the second node  102  and the fifth node  105  indicating that a preferred communication link is now established directly between the second node  102  and the fifth node  105 . According, if the base station BS and the fifth node  105  wish to communicate with each other, then must now communicate indirectly via the second node  103  rather than the first node  101 . Likewise, the exemplary network topology  150 B also shows that the line previously displayed between the sixth node  106  and the seventh node  107  is now removed indicating that a preferred communication link is no longer established directly between the sixth node  106  and the seventh node  107 , and that a line was added between the base station BS and the seventh node  107  indicating that a preferred communication link has been established directly between the base station BS and the seventh node  107 . Accordingly, if the base station BS and the seventh node  107  wish to communicate with each other, they simply send a message directly to one another, rather than via the third node  103 .  
         [0040]     It is noted that although the adverse environmental condition  999  no longer exists between the base station BS and the sixth node  106 , as shown in  FIG. 3 , the exemplary network topology  150 B has not been reconfigured with respect to the preferred communication relationship between the base station and the sixth node  106 . That is, the base station BS and the sixth node  106  do not establish a preferred communication link directly, but rather, continue to communicate indirectly via the third node  103 . This is because the removal of the adverse environmental condition  999  between the base station BS and the sixth node  106  does not necessarily mean that a direct communication link between the base station BS and the sixth node  106  is the most reliable link. Rather, another indirect path may still prove to be the most reliable, which in this instance, is the combination of the preferred communication link established between the sixth node  106  and the third node  103 , and the preferred communication link established between the third node  103  and the base station BS.  
         [0041]      FIG. 5  shows an exemplary method  500  of enhancing an operational lifetime of the exemplary wireless network  100  of  FIG. 1 , in which the network topology of the exemplary wireless network  100  is changed to accommodate changing network conditions so that the most reliable links between the nodes are used. The following steps S 501  to S 504  of the exemplary method  500  are described below.  
         [0042]     In step S 501 , information is periodically collected regarding a link quality between the devices of the exemplary wireless network  100 . For example, information regarding a link quality between the base station BS and each of the seven network nodes  101  to  107 , and/or between the network nodes themselves, is collected periodically and analyzed to determine which links are, or should be, the most reliable, and which links are, or are likely to be, the least reliable.  
         [0043]     In step S 502 , the network topology of the exemplary wireless network  100  is reconfigured based on the collected information. For example, if it is determined from the collected information that a certain link previously considered to be the most reliable now becomes relatively unreliable, due to, for example, a negatively affecting change in an adverse environmental condition, or that a certain link previously considered to be relatively unreliable now becomes the most reliable, due to, for example, a positively affecting change in an adverse environmental condition, the network topology of the exemplary wireless network  100  may be reconfigured to accommodate these changed conditions. In particular, the established preferred communication links may be adjusted to reflect the change in link quality.