Energy Efficient Wireless Sensor Network, Node Devices for the Same and a Method for Arranging Communications in a Wireless Sensor Network
First Claim
1. A wireless sensor network (100) comprisinga first headnode (101)a first subnode (102) adapted to communicate with the first headnode (101), thus making the first headnode (101) and the first subnode (102) members of a first cluster (103)a second headnode (111) anda second subnode (112) adapted to communicate with the second headnode (111), thus making the second headnode (111) and the second subnode (112) members of a second cluster;
- characterized in thatthe first headnode (101) is adapted to select a first frequency for use in wireless communications within the first cluster (103)the first subnode (102) is adapted to communicate with the first headnode (101) on said first frequency, using a time slotted channel access scheme to allow also other nodes to communicate with the first headnode (101) on said first frequencythe second headnode (111) is adapted to find out the first frequency selected by the first headnode (101), and to select a second frequency—
different from said first frequency—
for use in wireless communications within the second clusterthe second subnode (112) is adapted to communicate with the second headnode (111) on said second frequency, using a time slotted channel access scheme to allow also other nodes to communicate with the second headnode (111) on said second frequency andfor communicating information from the first cluster (103) to the second cluster, the first headnode (101) is adapted to find out the second frequency selected by the second headnode (111) and to communicate with the second headnode (111) on said second frequency, using the same time slotted channel access scheme as said second subnode (112).
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Abstract
A wireless sensor network, a node device thereof and a method for arranging communications therein are presented. A first frequency is used in wireless communication of information between a headnode and subnodes of a first cluster (103) using a time slotted channel access scheme. A headnode of a second cluster (113) known the first frequency and selects a second, different frequency for use in wireless communication of information within said second cluster (113) using a time slotted channel access scheme. The headnode of the first cluster (103) is informed about the second frequency selected for the second cluster (113). Information from the headnode of said first cluster (103) to the headnode of said second cluster (113) is communicated on said second frequency, using the same time slotted channel access scheme as other nodes in said second cluster (113).
225 Citations
51 Claims
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1. A wireless sensor network (100) comprising
a first headnode (101) a first subnode (102) adapted to communicate with the first headnode (101), thus making the first headnode (101) and the first subnode (102) members of a first cluster (103) a second headnode (111) and a second subnode (112) adapted to communicate with the second headnode (111), thus making the second headnode (111) and the second subnode (112) members of a second cluster; -
characterized in that the first headnode (101) is adapted to select a first frequency for use in wireless communications within the first cluster (103) the first subnode (102) is adapted to communicate with the first headnode (101) on said first frequency, using a time slotted channel access scheme to allow also other nodes to communicate with the first headnode (101) on said first frequency the second headnode (111) is adapted to find out the first frequency selected by the first headnode (101), and to select a second frequency—
different from said first frequency—
for use in wireless communications within the second clusterthe second subnode (112) is adapted to communicate with the second headnode (111) on said second frequency, using a time slotted channel access scheme to allow also other nodes to communicate with the second headnode (111) on said second frequency and for communicating information from the first cluster (103) to the second cluster, the first headnode (101) is adapted to find out the second frequency selected by the second headnode (111) and to communicate with the second headnode (111) on said second frequency, using the same time slotted channel access scheme as said second subnode (112). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
where Prx=power consumption of a node in receiving mode, Eb=sum of energy used to transmit a transmission frame at a first transmission power level and energy used to transmit a frame of data at a second transmission power level, lower than said first transmission power level, Ts(h)=network scanning interval for headnodes Ts(s)=network scanning interval for subnodes and ns=number of subnodes per each headnode.
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15. A wireless sensor network according to claim 2, characterized in that:
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each of said first headnode (101) and second headnode (111) is adapted to transmit a full time stamp (843) indicating absolute time in each network beacon signal and a short time stamp (847) indicating a number of least significant bits of absolute time in cluster beacon signals transmitted on the cluster frequency of the headnode, each node of the wireless sensor network is adapted to read time stamps from received beacon signals and to adjust an internal clock of the node to match a time reference indicated in said time stamps.
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16. A wireless sensor network according to claim 15, characterized in that each of said first headnode (101) and second headnode (11) is adapted to transmit a time accuracy indicator (844, 848) together with a time stamp, said time stamp accuracy indicating at least one of number of hops between nodes from a reference time source and time since the node transmitting said time stamp has received a time reference.
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17. A wireless sensor network according to claim 1, characterized in that
each of the first (101) and second (111) headnode is adapted to announce, in a transmitted beacon signal, a current load situation (837) in their clusters, and a node device of said wireless sensor network is adapted to associate as a subnode to one of the clusters of the first (101) or second (111) headnode, or establish itself as a headnode of a new cluster, depending on how loaded the first (101) and second (111) headnode announced their clusters to be. -
18. A wireless sensor network according to claim 1, characterized in that at least one of the first (101) and second (111) headnodes is a sink node (104) adapted to collect information from other nodes in the wireless sensor network and to act as a gateway to at least one of another system and another network.
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19. A wireless sensor network according to claim 1, characterized in that as node devices (101, 102, 104, 111, 112) it comprises devices adapted to selectively act as either headnodes or subnodes, and devices adapted to act as subnodes only, said device that are adapted to act as subnodes only not being capable of routing or data aggregation.
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20. A wireless sensor network according to claim 1, characterized in that as node devices (101, 102, 104, 111, 112) it comprises exclusively devices adapted to selectively act as either headnodes or subnodes.
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21. A node device (101, 102, 104, 111, 112, 1101) for a wireless sensor network, comprising:
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a wireless transceiver (1151) adapted to exchange information with other node devices on a communications frequency according to a time slotted channel access scheme, and a controller unit (1141) adapted to control the wireless transceiver (1151), characterized in that the controller unit (1141) is adapted to selectively tune the wireless transceiver (1151) to a first frequency for receiving cluster beacon signals (321, 322) from a cluster headnode and to a second frequency for receiving network beacon signals (331, 332), and the controller unit (1141) is additionally adapted to detect, which parts of a multipart beacon signal (321, 322, 331, 332) were successfully received, and to use said detection for deriving an estimate of a distance between the node device and the device that transmitted said beacon signal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A method for arranging communications in a wireless sensor network, characterized in that it comprises:
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selecting a first frequency for use in wireless communications between a headnode and subnodes of a first cluster (103) communicating information between the nodes of said first cluster (103) on said first frequency, using a time slotted channel access scheme informing a headnode of a second cluster (113) about the first frequency selected for the first cluster (103), and selecting a second frequency—
different from said first frequency—
for use in wireless communications within said second cluster (113)communicating information between the nodes of said second cluster (113) on said second frequency, using a time slotted channel access scheme and informing the headnode of the first cluster (103) about the second frequency selected for the second cluster (113) and communicating information from the headnode of said first cluster (103) to the headnode of said second cluster (113) on said second frequency, using the same time slotted channel access scheme as other nodes in said second cluster (113). - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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Specification