JP2008244756A - Power saving system for wireless sensor network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power saving system for a wireless sensor network capable of reducing a communication data amount and the number of transmitting times and performing the power saving of a battery by shortening an RF communication time being a factor of power consumption and accordingly shortening a CPU processing time during communication. <P>SOLUTION: The power saving system for a wireless sensor network includes a network configuration by multi-stage connection used in a wide range space, configured by providing one gateway node (GN) as a top and connecting a router node (RN) having a relay function or a sensor node (SN) having no relay function at its subordinate position, wherein each node is given a unique address which is determined by the number of maximum slave nodes (C<SB>max</SB>), the number of maximum routers (R<SB>max</SB>) and the number of maximum hops (D<SB>max</SB>) for communication by radio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention saves a wireless sensor network using a network that wirelessly transmits information from sensors distributed in buildings, factories, hospitals, etc. to servers, controllers, etc., which are central control / management devices. The present invention relates to an electric power system.

  In recent years, wireless sensor networks have been used and applied in a wide range of fields from building environment measurement to medical care, not limited to the field of building automation maintenance and management.

  The wireless sensor network, for example, measures the temperature and humidity of the rooms on each floor of the building using temperature and humidity sensors, and sends temperature and humidity data to server devices in the central control room to adjust the temperature and humidity appropriately. Energy saving can be implemented by automatically turning on / off the room lighting based on information from the lighting sensor and preventing equipment failure based on information from the acceleration / strain sensor. The latest network system.

  This wireless sensor network is expected to save space for sensor nodes (hereinafter referred to as SN) having a measurement function using attached sensors and router nodes (hereinafter referred to as RN) having a relay function in addition to the measurement function. Advantages of portability, portability, and ease of installation (no wiring).

One element for realizing these advantages is power saving by applying a battery such as a button battery to SN and RN. When SN and RN are operated continuously, for example, The reality is that they are changed as often as once a month.
nothing special

  As described above, in the conventional wireless sensor network, it is necessary to frequently replace the SN and RN batteries, so that maintenance is troublesome and power saving of the battery is still a problem to be solved. Yes.

  The factors that cause the SN and RN to consume power are, first, between RN (= PN: parent node) ⇔ SN (= CN: child node), RN (= PN: parent node) ⇔ RN (= CN: child) Node), gateway node (hereinafter referred to as GN) (= PN: parent node) ⇔ RN or SN (= CN: child node) RF communication, secondly during communication and RF communication interference and jamming radio waves, etc. Communication retry by third, thirdly, CPU processing during RF communication between RN-SN, RN-RN, GN-RN or SN, and fourth, CPU processing during sensing in SN and RN, etc. In order to achieve this, it is necessary to shorten the RF communication time and CPU processing time.

  Therefore, the present invention was created in view of the existing circumstances as described above, and by shortening the RF communication time which is a factor of power consumption, the CPU processing time during communication is also shortened. Therefore, an object of the present invention is to provide a power saving system for a wireless sensor network that can reduce the amount of communication data and the number of transmissions, and can save battery power.

The power saving system for a wireless sensor network according to the present invention has a gateway node (GN) as a vertex and a router node (RN) having a relay function or a sensor node (SN) having no relay function under the gateway node (GN). A network configuration with multi-stage connection used in a wide space formed by connecting nodes, and for wireless communication, each node has a maximum number of child nodes (C _max ), a maximum number of routers (R _max ), and a maximum hop The above-mentioned problem was solved by giving a unique address determined by a number (D _max ).

In addition, the maximum number of child nodes (C _max ), the maximum number of routers (R _max ), and the maximum number of hops (D _max ) that each node has in common are set to preset values after the gateway node is operated. However, the above-mentioned problem has been solved by making it possible to change it by software and making it possible to autonomously support a linear tree structure or a cluster tree structure according to the maximum number of routers set.

  Furthermore, with respect to the time synchronization method, the GN or RN serving as the parent node (PN) implements the master clock, and the RN or SN serving as the child node (CN) is mounted with the slave clock, so that the CN has time information and The amount of time difference between the time information held by the PN is calculated and synchronized with the time of the master clock, so that the time information held by each of the PN and CN or all nodes (RN or SN) other than the GN and GN The above-mentioned problem has been solved by using a method of transmitting at least once within an allowable error time between the master clock and the slave clock and superimposing them on the transmission frame of the measurement data.

  For network configuration, create a group for each node, set the time zone for communication for each group to which each node belongs and the time zone for communication between nodes belonging to the same group. The above-mentioned problem was solved by adopting a method that operates autonomously regardless of the network configuration of the tree.

In addition, the group number formula for the cluster tree is
G _GN = 1,
_{G OWN = (G PN -1)} × R max + n + 1; n = 1, ..., R max
age,
On the other hand, the group number calculation formula at the time of linear tree is
G _GN = 1,
G _OWN = G _PN +1
(Where G _GN : group number when GN is a parent node, G _PN : group number of parent node, G _OWN : group number when its own node is a parent node) Solved the problem.

  In addition, all functions (CPU unit, RF unit, sensor unit) other than the clock function are put to sleep while measurement by the sensor and measurement data transmission / reception, time synchronization information transmission / reception, network construction, and frame transfer by the relay function are not performed. When the measurement is performed by the sensor, the RF unit is set to sleep, and when the frame transfer is performed by the relay function, the sensor unit is set to sleep. Settled.

  According to the present invention, by shortening the RF communication time that is a factor of power consumption, the CPU processing time at the time of communication is also shortened, so the amount of communication data and the number of transmissions can be reduced, and the battery The power saving can be achieved.

In other words, it is used in a wide space where one gateway node (GN) is the apex, and a router node (RN) having a relay function or a sensor node (SN) having no relay function is connected to the top node. Each node has a network configuration with multi-stage connection, and for wireless communication, each node is determined by a maximum number of child nodes (C _max ), a maximum number of routers (R _max ), and a maximum number of hops (D _max ). Since addresses are assigned, for example, regarding the transmission of data between nodes, the values of the operation parameters such as the maximum number of child nodes, the maximum number of routers, and the maximum number of hops are all common to each node constituting the cluster tree network. And a cluster tree structure with a maximum number of routers of 2 or more, or linear transmission of data between nodes Each node composing the tree network has the same number of parameters for the maximum number of child nodes, the maximum number of routers, and the maximum number of hops, and the maximum number of routers is 1, so that the CPU processing time during communication is Can be shortened, and the amount of communication data and the number of transmissions can be reduced. This data means measurement data and operation parameters.

  In this way, when communicating with a target node from a uniquely determined communication address, when the communication partner is a parent node or a child node, direct communication is possible and direct transmission is possible, and direct communication is not possible. In this case, it is only necessary to transmit data to a parent node or a child node having a relay function.

  Further, if the destination address is not addressed to itself, the node receiving the transmitted frame determines the transfer destination using the shortest path in the tree structure, and transmits data to the transfer destination. By doing so, the data is carried to the target node through the shortest path on the tree.

Further, the maximum number of child nodes (C _max ), the maximum number of routers (R _max ), and the maximum number of hops (D _max ) that each of the nodes has in common are set to preset values after the gateway node operates. However, it can be changed by software, and depending on the maximum number of routers that can be set, it is possible to autonomously support a linear tree structure or cluster tree structure. The amount of data and the number of transmissions can be reduced.

  As for the time synchronization method, the GN or RN serving as the parent node (PN) implements the master clock, and the RN or SN serving as the child node (CN) is mounted with the slave clock, so that the CN has time information and The amount of time difference between the time information held by the PN is calculated and synchronized with the time of the master clock, so that the time information held by each of the PN and CN or all nodes (RN or SN) other than the GN and GN Is transmitted at least once within the allowable error time between the master clock and the slave clock, and is superimposed on the measurement data transmission frame, so that the number of data transmissions can be reduced.

  In addition, for the network configuration, create a group of each node, set the time zone for communication for each group to which each node belongs and the time zone for communication between nodes belonging to the same group, respectively, Since a system that operates autonomously is employed regardless of the network configuration of the linear tree, data transmission can be eliminated. Moreover, by applying this method, interference during RF communication with other nodes can be reduced, and the number of data transmissions due to retries can be reduced.

Also, the group number calculation formula at the time of cluster tree is
G _GN = 1,
_{G OWN = (G PN -1)} × R max + n + 1; n = 1, ..., R max
age,
On the other hand, the group number calculation formula at the time of linear tree is
G _GN = 1,
G _OWN = G _PN +1
By performing the above grouping, the time zone in which each group can communicate can be time-divided. As a result, in other groups, no node communication occurs, so that the nodes in the group can reliably communicate.

  In addition, since communication of nodes belonging to the same group is also time-shared, there is no node that performs communication at the same time in the entire system.

  In addition to this, all functions (CPU unit, RF unit, sensor unit) other than the clock function sleep while measurement by the sensor and measurement data transmission / reception, time synchronization information transmission / reception, network construction, and frame transfer by the relay function are not performed. When the measurement is performed by the sensor, the RF unit is set to sleep. When the frame transfer by the relay function is performed, the sensor unit is set to sleep, so the RF communication time is reduced. In addition to the reduction in the CPU operation time, the battery power can be saved by sleeping the RF unit, the CPU unit, and the sensor unit outside the operation time.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

The wireless sensor network power saving system according to the present invention is a two-dimensional network configuration mainly used in a wide space, that is, a so-called ZigBee cluster tree configuration, and mainly used in a narrow space. The _{maximum of} the operation parameters (C _max , R _max , D _max , etc) that are changed based on the setting parameters on the network browser are mutually independent from the linear tree configuration that is a one-dimensional network configuration. It is switched autonomously according to the number of routers (R _max ).

  When configuring a network using a plurality of wireless communication nodes, a node is a vertex, and a node having a relay function or a node not having a relay function is connected to the node. At this time, a node as a vertex is a gateway node (GN), a node having a relay function is a router node (RN), and a node having no relay function is a sensor node (SN). Further, the node (GN) of the vertex (= 0th layer) is set as the parent node: PN. The RN or SN of the lower layer (= first layer) connected to this parent node: GN is defined as a child node: CN. For wireless communication, each node is assigned an address with a number that does not overlap with 0, 1, 2,.

  In the wireless sensor network in this embodiment, each node (RN or SN) transmits, for example, data measured by the sensor to the GN as sensing data (uplink communication: GN ← RN or SN). Also, communication-related operation parameters are transmitted from the GN to each node (RN or SN) (downward communication: GN → RN or SN).

  First layer parent node: Since RN or SN can be connected to the lower layer (second layer) under the RN, if the RN has a child node under the RN, the RN is the parent to the child node. Become a node.

  Node with relay function: Node under RN (lower layer): Node with further relay function: RN is connected as a child node, so multi-stage connection (multi-hop) is possible, thereby comprising multiple wireless communication nodes Wireless network can be constructed.

Next, as shown in FIG. 8, a configuration example of the wireless sensor network in the operation parameters: C _max = 4, R _max = 2 and D _max = 3 will be described.

When configuring a network using this wireless communication node, the total number of CNs (RN or SN) that can be connected to one PN (= GN or RN) is the _maximum number of child nodes: C _max . Further, among C _max , the total number of nodes having relay functions: RN is set to the maximum number of router child nodes: R _max (C _max ≧ R _max ). Also, assuming that the hierarchy of one GN is 0, the number of connection stages from this GN to the SN that can be connected via the relay node: RN is the maximum number of layers (= hops): _Dmax . C _max and R _max are constant values in all layers of the network regardless of the cluster tree configuration and the linear tree configuration, and thus do not change regardless of the layer position.

Here, the case of R _max ≧ 2 corresponds to the cluster tree configuration, and the case of R _max = 1 corresponds to the linear tree configuration described above. The cluster tree configuration is a network configuration suitable for use in a two-dimensional space such as an office or a crop field. On the other hand, the linear tree configuration is a network configuration suitable for use in a one-dimensional space whose long side is extremely long with respect to the short side, such as a tunnel or a plastic house.

In addition, each of the network configurations described above is determined by operation parameters: C _max , R _max , D _max , and each node has a unique address determined by operation parameters: C _max , R _max , D _max Is granted. In addition, since the operation parameters: C _max , R _max , and D _max can be changed by software even after the GN is activated, it is possible to correspond to the linear tree structure or the cluster tree structure. Can be done flexibly.

  Specifically, the cluster tree configuration will be described. As shown in FIG. 1, the GN of the address 0 in the hierarchy d = 0 is set as a data collection node, for example, the address 1 having a relay function in the hierarchy d = 1. 14 RNs and two SNs of addresses 27 and 28 not having a relay function are arranged.

  Further, four RNs of addresses 2, 7, 15, and 20 having a relay function and four SNs of addresses 12, 13, 25, and 26 having no relay function are arranged in the hierarchy d = 2.

  Further, 16 SNs of addresses 3, 4, 5, 6, 8, 9, 10, 11, 16, 17, 18, 19, 21, 21, 22, 23, 24 that do not have a relay function in the hierarchy d = 3 are obtained. Arranged. At this time, the RN also has an SN function.

The specific node address calculation formula for the inter-node transmission of data (measurement data, operation parameters, etc.) in the cluster tree configuration as described above is as follows:
C _skip (d) = (1+ (C _max −R _max ) − (C _max × R _max ^{(Dmax−d−1)} )) / (1−R _max ): d = 0,..., (D _max −1 )
A _GN = 0
A _RN (d) = A _PN + 1 + C _skip (d−1) × (n−1): d = 1,..., D _max , n = 1 _,.
A _SN (d) = A _PN + C _skip (d−1) × R _max + n: d = 1,..., D _max , n = 1,..., (C _max −R _max )
Here, C _max is the maximum number of child nodes, R _max is the maximum number of routers, and D _max is the maximum number of hops. A _GN is a gateway node address, A _RN is a router node address, A _SN is a sensor node address, and A _PN is a parent node address.

In this cluster tree configuration, operation parameters: C _max , R _max , D _max are common to all nodes, and the maximum number of routers R _max is 2 or more.

  When attention is paid to two points between the upper node and the lower node, the upper side is referred to as a parent node (PN) and the lower side is referred to as a child node (CN).

For example, if C _max = 4, R _max = 2, D _max = 3, and the GN hierarchy d = 0, the skip value is C _skip (0) = 1 + 4-2-4 × 2 ^(3-0-1) / (1-2) = 13. Similarly, when d = 1, C _skip (1) = 5, and when d = 2, C _skip (2) = 1.

Since the calculation of the address of RN is A _PN = A _GN = 0 when d = 1, A _RN (1) = 0 + 1 + C _skip (0) × (n−1) = 1 + 13 × (n−1) Here, since n is 1 or 2, A _RN (1) = 1 when n = 1, and A _RN (1) = 14 when n = 2. When d = 2, A _PN = A _RN = 1 or 14, and when A _PN = 1, A _RN (2) = 1 + 1 + C _skip (1) × (n−1) = 2 + 5 × (n−1) It becomes. Here, when n = 1, A _RN (2) = 2, and when n = 2, A _RN (2) = 7. Similarly, when d = 2, A _PN = 14, and when n = 1, A _RN (2) = 15, and when n = 2, A _RN (2) = 20. Similarly, when d = 3, A _PN = A _RN (2) = 2, 7, 15, and 20, and when A _PN = 2 and n = 1, A _RN (3) = 3. When n = 2, A _RN (3) = 4. Further, when A _PN = 7 and n = 1, A _RN (3) = 8, and when n = 2, A _RN (3) = 9. Further, when A _PN = 15 and n = 1, A _RN (3) = 16, and when n = 2, A _RN (3) = 17. Further, when A _PN = 20 and n = 1, A _RN (3) = 21, and when n = 2, A _RN (3) = 22. Here, since d = 3 = D _max , A _RN (3) operates as a sensor node, not as a router node, and invalidates the relay function.

In addition, since the SN address calculation is A _PN = A _GN = 0 when d = 1, A _SN (1) = 0 + C _skip (0) × 2 + n = 0 + 13 × 2 + n = n + 26 and C _max −R _max = Since 4-2 = 2, n = 1 or 2. Therefore, _ASN (1) = 1 + 26 = 27 when n = 1, and _ASN (1) = 2 + 26 = 28 when n = 2. Further, when d = 2, A _PN = A _RN (1) = 1, 14, and when A _PN = 1 and n = 1, A _SN (2) = 12, and when n = 2, A _SN ( 2) = 13. Further, when A _PN = 14 and n = 1, A _SN (2) = 25, and when n = 2, A _SN (2) = 26. In addition, when d = 3, A _PN = A _RN (2) = 2, 7, 15, and 20, and when A _PN = 2 and n = 1, A _SN (3) = 5, n When A = 2, A _SN (3) = 6. When A _PN = 7 and n = 1, A _SN (3) = 10, and when n = 2, A _SN (3) = 11. Further, when A _PN = 15 and n = 1, A _SN (3) = 18, and when n = 2, A _SN (3) = 19. When A _PN = 20 and n = 1, A _SN (3) = 23, and when n = 2, A _SN (3) = 24.

  In this way, the operating parameters are transmitted from the GN at address 0 in the hierarchy d = 0 to the RNs at addresses 1 and 14 and SNs at addresses 27 and 28 in the hierarchy d = 1, and the RN at address 1 in the hierarchy d = 1. From the RN of the address 14 in the hierarchy d = 2 to the SNs of the addresses 12 and 13, respectively, and the RN of the address 14 in the hierarchy d = 1 to the RN of the addresses 15 and 20 in the hierarchy d = 2, The operating parameters are transmitted to the SNs of addresses 25 and 26, respectively. Further, the operation parameter is transmitted from the RN of the address 2 in the hierarchy d = 2 to the SNs of the addresses 3, 4, 5 and 6 in the hierarchy d = 3, and from the RN of the address 7 in the hierarchy d = 2 to the hierarchy d. Operation parameter is transmitted to the SNs of addresses 8, 9, 10, and 11 at = 3, and the operation parameter is transmitted from the RN at address 15 at the layer d = 2 to the SNs of addresses 16, 17, 18, and 19 at the layer d = 3. And the operation parameters are transmitted from the RN of the address 20 in the hierarchy d = 2 to the SNs of the addresses 21, 22, 23, and 24 in the hierarchy d = 3.

  On the other hand, the measurement data is transmitted from the SNs of addresses 3, 4, 5 and 6 in the hierarchy d = 3 to the RN of the address 2 in the hierarchy d = 2 and the addresses 8, 9, 10 and 11 in the hierarchy d = 3. SN is transmitted to the RN of the address 7 in the hierarchy d = 2, and is transmitted from the SN of the addresses 16, 17, 18 and 19 in the hierarchy d = 3 to the RN of the address 15 in the hierarchy d = 2, and the hierarchy d = 3. Is transmitted from the SN of the addresses 21, 22, 23, and 24 to the RN of the address 20 in the hierarchy d = 2. The measurement data is transmitted from the RN of addresses 2 and 7 in the hierarchy d = 2 and the SN of addresses 12 and 13 to the RN of address 1 in the hierarchy d = 1, and addresses 15 and 20 in the hierarchy d = 2. RN and SN of addresses 25 and 26 are transmitted to RN of address 14 in layer d = 1. Further, the measurement data is transmitted from the RN of the addresses 1 and 14 in the hierarchy d = 1 and the SN of the addresses 27 and 28 to the GN of the address 0 in the hierarchy d = 0.

  As shown in FIG. 2, the linear tree configuration is such that the GN at the address 00 in the hierarchy d = 0 is a data collection node, for example, one RN of the address 10 having a relay function in the hierarchy d = 1, Each of the three SNs of the addresses 11, 12, and 13 having no relay function is arranged, one RN of the address 20 having the relay function in the layer d = 2, and addresses 21, 22, and 23 having no relay function Each of the three SNs is arranged, and four SNs of addresses 30, 31, 32, and 33 having no relay function are arranged in the hierarchy d = 3. At this time, the RN also has an SN function.

The node address calculation formula for inter-node transmission of data (measurement data, operation parameters, etc.) in the above linear tree configuration is as follows:
C _skip = fixed value A _GN = 0
A _RN (d) = d × C _skip : d = 1,..., D _max
A _SN (d) = A _RN (d) + n: d = 1,..., D _max , n = 1 _,.

Here, C _skip takes a fixed value without depending on the hierarchy d. Also in the linear tree configuration, the operation parameters: C _max , R _max , D _max are common to all nodes, and the maximum number of routers R _max is 1.

For example, when the operation parameters are C _max = 4, R _max = 1, and D _max = 3, the C _skip value in the linear tree configuration is a constant value regardless of the hierarchy d. If the fixed value is set to 10, when d = 1, A _RN (1) = 1 × C _skip = 1 × 10 = 10, and when d = 2, A _RN (2) = 20, d = 3 In this case, A _RN (3) = 30. Here, since d = 3 = D _max , A _RN (3) operates as SN, not RN. The fixed value can be changed according to the environment, for example, the number of child nodes (CN).

In addition, since the SN address calculation is A _SN (d) = A _RN (d) + n = d × C _skip + n, when d = 1, A _SN (1) = 1 × 10 + n = 10 + n and n = 1 When A _SN (1) = 11, n = 2, A _SN (1) = 12, and when n = 3, A _SN (1) = 13. When d = 2, A _SN (2) = 21 when n = 1, A _SN (2) = 22 when n = 2, and A _SN (2) = 23 when n = 2. When d = 3, A _SN (3) = 31 when n = 1, A _SN (3) = 32 when n = 2, and A _SN (3) = 33 when n = 3.

  In this way, the operating parameters are transmitted from the GN at address 0 in the hierarchy d = 0 to the RN at address 10 and the SNs at addresses 11, 12, and 13 in the hierarchy d = 1, and the address 10 at the hierarchy d = 1. The operating parameters are transmitted from the RN to the RN of the address 20 in the hierarchy d = 2 and the SNs of the addresses 21, 22, 23, respectively, and from the RN of the address 20 in the hierarchy d = 2 to the addresses 30, 31, The operating parameters are transmitted to 32 and 33 SNs.

  On the other hand, the measurement data is transmitted from the SN of the addresses 30, 31, 32, and 33 in the hierarchy d = 3 to the RN of the address 20 in the hierarchy d = 2, and the RN and the addresses 21 and 22 of the address 20 in the hierarchy d = 2. 23 from the SN of address 10 and SNs of addresses 11, 12, and 13 to the GN of address 0 in layer d = 0.

  In addition, types of measurement data to be communicated include sensing data, time synchronization information, and network configuration. By reducing time synchronization information, the number of times of data transmission of the network configuration, and transmission time, power saving is achieved. .

  By implementing a master clock in the GN or RN serving as the parent node (PN) and a slave clock in the RN or SN serving as the child node (CN), the time information possessed by the CN and the time information possessed by the PN In order to calculate the amount of misalignment and synchronize with the time of the master clock, the time information of each between the PN and CN or between all nodes (RN or SN) other than GN and GN, between the master clock and the slave clock The method of transmitting at least once within the allowable error time is superimposed on the measurement data transmission frame.

  As for the network configuration, as shown in FIG. 3 in the case of a cluster tree and as shown in FIG. 4 in the case of a linear tree, each node is grouped, and communication is performed for each group to which each node belongs. A possible time zone and a time zone during which communication is possible between nodes belonging to the same group are set, and the system operates autonomously regardless of the network configuration. That is, the measurement data cannot be simultaneously sent to the GN, and the communication timing is changed or the communication time is divided.

In this case, the group number calculation formula at the time of the cluster tree, _G GN = 1 The GN _{group, G OWN = (G PN -1} ) as the own group _{× R max + n + 1;} n = 1, ..., with _{R max} is there. On the other hand, the group number calculation formula at the time of the linear tree is G _GN = 1 for the GN group and G _OWN = G _PN +1 for its own group. These are the group calculation formulas for the RN having child nodes among the nodes that communicate directly with the GN. Here, G _GN is the group number of GN, G _PN is the group number of the parent node, and G _OWN is the group number when the own node is the parent node.

In the group number calculation formula at the time of the cluster tree, for example, since the group number of the RN located at d = 1 is R _max = 2, G _OWN = (1-1) × 2 + n + 1 = n + 1, and n = When it is 1, G _OWN = 1 + 1 = 2, and when n = 2, G _OWN = 2 + 1 = 3. The group number of the RN located at d = 2 is G _OWN = (2-1) × 2 + n + 1 = 2 + n + 1 = n + 3 when G _PN = 2, and G _OWN = 1 + 3 = 4 when n = 1 When G = 2, G _OWN = 2 + 3 = 5. In addition, when G _PN = 3, G _OWN = (3-1) × 2 + n + 1 = 4 + n + 1 = n + 5, when n = 1, G _OWN = 1 + 5 = 6, and when n = 2, G _OWN = 2 + 5 = 7 .

On the other hand, G _GN = 1 in the group number calculation formula for the linear tree. At this time, if C _max = 4, R _max = 1, and D _max = 3, the group number of the RN located at d = 1 from G _OWN = _GPN +1 is G _PN = G _GN = 1. G _OWN = 1 + 1 = 2. Also, the group number of the RN located at d = 2 is G _PN = 2 and _therefore G _OWN = 2 + 1 = 3.

In addition, all functions (CPU unit, RF unit, sensor unit) other than the clock function are put to sleep while measurement by the sensor and measurement data transmission / reception, time synchronization information transmission / reception, network construction, and frame transfer by the relay function are not performed. When the measurement is performed by the sensor, the RF unit is set to sleep. When the frame transfer is performed by the relay function, the sensor unit is set to sleep.
For example, it becomes active only during SN sensing and communication, and enters a sleep state in other time zones. Moreover, it becomes active only at the time of RN sensing and communication, and also becomes active during a time zone in which subordinate nodes communicate. In other time zones, the sleep mode is set. In particular, since power consumption is the largest in wireless communication, it is convenient to stop transmission / reception of radio waves in this way when unnecessary.

  In addition, as a time synchronization function when sending sensor information, LTSP (Lightweight Time Sync Protocol) is adopted, and a child node (CN) is synchronized with a parent node (PN) as shown in FIG. As shown in FIG. 6, there are two cases: RN / SN is synchronized with GN. For example, in order to prevent an error of 1 second between the nodes, synchronization correction is required twice a day.

  As shown in FIG. 5, when synchronizing with the parent node (PN), the measurement data + time information is sent from the lower node A to the node B, and only the time information is sent from the node B to the node A. On the other hand, only the measurement data is sent from the node B to the node C and from the node C to the upper GN.

  As shown in FIG. 6, when synchronizing with GN, measurement data + time information is sent from node A in the lower order to node B and node C and GN in the higher order, respectively. On the other hand, only time information is sent in the order of the node C and the node B and the node A in the lower order from the GN in the higher order.

The operation parameters are time information during the time synchronization operation, but are distributed to all the subordinate nodes from the GN at the time of the change notification of the operation parameters. Therefore, a large number of operation parameters (C _max , R _max , D _max , etc) flows as data.

As a specific time synchronization method by LTS, as shown in FIG. 7, if time synchronization between a parent node (PN) and a child node (CN) is a transmission time Ts and a reception time Tr, By averaging using the payload: L _CN (Ts) and the payload: L _CN (Ts), L _PN (Tr), L _PN (Ts), the difference value with respect to the parent node (PN) becomes O _CN = (L _PN ( Ts) −L _CN (Tr) + L _PN (Tr) −L _CN (Ts)) / 2, and time synchronization correction is performed based on this value. In this method, time synchronization between the parent node (PN) and child node (CN) (indicated by 1 in the figure) and time synchronization between GN and RN / SN (indicated by 2 in the figure) ) Or any one of them can be selected.

  Next, an example of use and operation of the best mode of the present invention configured as described above will be described.

  First, the cluster tree configuration will be described.

  As shown in FIG. 1, operating parameters are transmitted from the GN at address 0 in the hierarchy d = 0 to the RNs at addresses 1 and 14 and SNs at addresses 27 and 28 in the hierarchy d = 1, and the hierarchy d = 1. Operating parameters are transmitted from the RN of address 1 to the RNs of addresses 2 and 7 and SNs of addresses 12 and 13 in the layer d = 2, and from the RN of address 14 in the layer d = 1 to the layer d = 2 The operation parameters are transmitted to the RNs of the addresses 15 and 20 and the SNs of the addresses 25 and 26, respectively. Further, the operation parameter is transmitted from the RN of the address 2 in the hierarchy d = 2 to the SNs of the addresses 3, 4, 5 and 6 in the hierarchy d = 3, and from the RN of the address 7 in the hierarchy d = 2 to the hierarchy d. Operation parameter is transmitted to the SNs of addresses 8, 9, 10, and 11 at = 3, and the operation parameter is transmitted from the RN at address 15 at the layer d = 2 to the SNs of addresses 16, 17, 18, and 19 at the layer d = 3. And the operation parameters are transmitted from the RN of the address 20 in the hierarchy d = 2 to the SNs of the addresses 21, 22, 23, and 24 in the hierarchy d = 3.

  On the other hand, the measurement data is transmitted from the SNs of addresses 3, 4, 5 and 6 in the hierarchy d = 3 to the RN of the address 2 in the hierarchy d = 2 and the addresses 8, 9, 10 and 11 in the hierarchy d = 3. SN is transmitted to the RN of the address 7 in the hierarchy d = 2, and is transmitted from the SN of the addresses 16, 17, 18 and 19 in the hierarchy d = 3 to the RN of the address 15 in the hierarchy d = 2, and the hierarchy d = 3. Is transmitted from the SN of the addresses 21, 22, 23, and 24 to the RN of the address 20 in the hierarchy d = 2. The measurement data is transmitted from the RN of addresses 2 and 7 in the hierarchy d = 2 and the SN of addresses 12 and 13 to the RN of address 1 in the hierarchy d = 1, and addresses 15 and 20 in the hierarchy d = 2. RN and SN of addresses 25 and 26 are transmitted to RN of address 14 in layer d = 1. Further, the measurement data is transmitted from the RN of the addresses 1 and 14 in the hierarchy d = 1 and the SN of the addresses 27 and 28 to the GN of the address 0 in the hierarchy d = 0.

  Next, a linear tree configuration will be described.

  As shown in FIG. 2, operating parameters are transmitted from the GN at address 0 in the hierarchy d = 0 to the RN at address 10 and the SNs at addresses 11, 12, and 13 in the hierarchy d = 1, and the hierarchy d = 1. Operating parameters are transmitted from the RN of the address 10 in the hierarchy d = 2 to the RN of the address 20 in the hierarchy d = 2 and the SNs of the addresses 21, 22, 23, respectively, and from the RN of the address 20 in the hierarchy d = 2 to the hierarchy d = 3 The operating parameters are transmitted to the SNs at addresses 30, 31, 32, and 33.

  On the other hand, the measurement data is transmitted from the SN of the addresses 30, 31, 32, and 33 in the hierarchy d = 3 to the RN of the address 20 in the hierarchy d = 2, and the RN and the addresses 21 and 22 of the address 20 in the hierarchy d = 2. 23 from the SN of address 10 and SNs of addresses 11, 12, and 13 to the GN of address 0 in layer d = 0.

  As shown in FIG. 5, when synchronizing with the parent node (PN), the measurement data + time information is sent from the lower node A to the node B, and only the time information is sent from the node B to the node A. On the other hand, only the measurement data is sent from the node B to the node C and from the node C to the upper GN.

The operation parameters are time information during the time synchronization operation, but are distributed to all the subordinate nodes from the GN at the time of the change notification of the operation parameters. Therefore, a large number of operation parameters (C _max , R _max , D _max , etc) flows as data.

  As shown in FIG. 6, when synchronizing with GN, measurement data + time information is sent from node A in the lower order to node B and node C, and GN in the upper order, respectively. On the other hand, only time information is sent in the order of the node C and the node B and the node A in the lower order from the GN in the higher order.

  The power saving system of the wireless sensor network according to the present invention can be used and applied not only in the field of building automation maintenance management and the like but also in a wide range of fields from measurement of building environment to medical treatment.

It is explanatory drawing which shows the content of a cluster tree structure. It is explanatory drawing which shows the content of a linear tree structure. It is explanatory drawing which shows the other example of a cluster tree structure. It is explanatory drawing which shows the other example of a linear tree structure. It is explanatory drawing in the case of synchronizing with a parent node. It is explanatory drawing in the case of synchronizing with GN. (A) shows an example of the flow of time synchronization between a parent node (GN or RN) and a child node (RN or SN), and time synchronization between all nodes (RN or SN) other than GN and GN. Explanatory drawing, (b) is explanatory drawing which shows an example of the time synchronization by a LTSP system, and a vertical axis | shaft represents a time axis. It is explanatory drawing which shows the specific structural example of the wireless sensor network by a cluster tree structure.

Explanation of symbols

GN ... Gateway node RN ... Router node SN ... Sensor node d ... Hierarchy Cskip (d): Address skip value in layer d in the cluster tree structure Cskip: Address skip value in linear tree structure Cmax: Maximum number of child nodes Rmax: Maximum number of router child nodes Dmax: Maximum number of hops

Claims (6)

Multi-stage connection used in a wide space consisting of one gateway node (GN) at the top and a router node (RN) with relay function or sensor node (SN) without relay function connected under it Each node has a unique address determined by the maximum number of child nodes (C _max ), the maximum number of routers (R _max ), and the maximum number of hops (D _max ). A wireless power saving system for a wireless sensor network. The maximum number of child nodes (C _max ), the maximum number of routers (R _max ), and the maximum number of hops (D _max ) that each of the above nodes have in common are the values set in advance even after the gateway node operates. The wireless sensor network power-saving system according to claim 1, wherein the wireless sensor network can be changed by software and can autonomously support a linear tree structure or a cluster tree structure in accordance with a set maximum number of routers.   Regarding the time synchronization method, the master clock is installed in the GN or RN serving as the parent node (PN), and the slave clock is implemented in the RN or SN serving as the child node (CN). In order to calculate the amount of deviation from the time information that it has and synchronize with the time of the master clock, the time information that each has between PN and CN or between all nodes (RN or SN) other than GN and GN, The wireless sensor network power-saving system according to any one of claims 1 to 3, wherein a transmission method is performed at least once within an allowable error time between a master clock and a slave clock, and is superimposed on a transmission frame of measurement data.   For the network configuration, create a group of each node, set the communication time zone for each group to which each node belongs and the communication time zone between nodes belonging to the same group. The wireless sensor network power saving system according to any one of claims 1 to 3, wherein a system that operates autonomously regardless of a network configuration is employed. The group number formula for the cluster tree is
G _GN = 1,
_{G OWN = (G PN -1)} × R max + n + 1; n = 1, ..., R max
age,
On the other hand, the group number calculation formula at the time of linear tree is
G _GN = 1,
G _OWN = G _PN +1
(Here, G _GN : Group number when GN is a parent node, G _PN : Group number of parent node, G _OWN : Group number when its own node is a parent node)
The power saving system of the wireless sensor network according to claim 4.   All functions (CPU part, RF part, sensor part) other than the clock function are set to sleep while measurement by the sensor and measurement data transmission / reception, time synchronization information transmission / reception, network construction, and frame transfer by the relay function are not performed. 6. The method according to claim 1, wherein when the measurement is performed by the sensor, the RF unit is set to sleep, and when the frame transfer is performed by the relay function, the sensor unit is set to sleep. Wireless sensor network power saving system.

Images