WO2013155657A1

WO2013155657A1 - Routing arrangement in a wireless sensor network

Info

Publication number: WO2013155657A1
Application number: PCT/CN2012/074098
Authority: WO
Inventors: Fei YIN; Zhenhong Li; Haifeng Wang; Honglin Hu; Zhi YUAN
Original assignee: Renesas Mobile Corp
Current assignee: Renesas Electronics Corp
Priority date: 2012-04-16
Filing date: 2012-04-16
Publication date: 2013-10-24
Anticipated expiration: 2014-10-16

Abstract

An arrangement for wireless sensor networks, wherein a mobile device connected to a mobile communication net work can be used for transmitting sensor measurements to a gateway by replacing a node of a wireless sensor network by the mobile device. In the arrangement a mo bile device receives a temporary address from the node and after preparations exchanges the address so that the information sent by child nodes of the replaced node will be received at the mobile device.

Description

ROUTING ARRANGEMENT IN A WIRELESS SENSOR NETWORK FIELD OF THE INVENTION

The invention relates to radio communication devices .

BACKGROUND OF THE INVENTION

Wireless sensor networks are used for gathering and communicating different types of information for various kinds of uses. For example, a network of thermometers may be used for controlling the temperature in a determined area or space. In wireless sensor networks the information gathered by the sensor is submitted to the next device by using telecommunication means. Typically these means are short distance means and the information is eventually sent to a gateway that sends the information to a server or other device of the user of the information. The gateway may use wireless or wired communication; however, many times the gateway is also wireless. In a common configuration the sensor acts as a routing device and sends the gathered information to a next sensor that sends the information further. Typically this forms a tree topology, wherein the parent acts as a hotspot that sends the information to the gateway. The hotspot may comprise additional communication means as the gateway may be far located.

As the sensors are wireless they have limited energy resources. When the sensor runs out of energy it dies and has to be replaced or charged somehow. The problem with this arrangement is that the sensors that are acting as a bridge between the hotspot and the node sending the information also need to spend energy for communication of other sensors. Furthermore, the hotspot node transmits all transmissions from the sen- sors. When the number of nodes in a sensor network is high the hotspot requires a lot of energy for communi- cation. Thus, it is possible that the hotspot runs out of energy and dies.

In prior art solutions this problem is solved by searching a hotspot or providing additional energy resources. The node that has noticed the death of the hotspot will send a broadcast message requesting a new hotspot. If there are no other hotspots available the communication is not possible. In certain configurations, for example in configurations using solar energy, a node or hotspot may sometimes be recovered later .

SUMMARY

The invention discloses an arrangement for wireless sensor networks, wherein a mobile device connected to a mobile communication network can be used for transmitting sensor measurements to a gateway by replacing a node of a wireless sensor network by the mobile device. In the arrangement the mobile device receives a temporary address from the node and after replacement preparations exchanges the address so that the information sent by child nodes of the replaced node will be received at the mobile device.

The devices in a wireless sensor network are arranged to perform measurements. The results are then transmitted wirelessly from the devices to, for example, a server that is arranged to collect and store measurement results for later use. Typically this data is transmitted from a sensor device to another until a so called hot spot node is reached. The hot spot node is arranged to submit all the measurements to a gateway through which the data is communicated to the server. According to the invention at least one node in such a network is replaced by a mobile mobile device in the coverage area of the wireless sensor network. In an embodiment of the invention an apparatus used as a node in a wireless sensor network comprises a transceiver for transmitting data in a wireless sensor network, wherein the node is configured to route data received with the network connection in accordance with a routing table stored in the node, a processor for executing at least one computer program and a memory for storing the routing table, program code and data of the at least one computer program. The node is configured to detect a mobile device with a transceiver for transmitting data in a wireless sensor network and to instruct the detected mobile device to temporarily replace the node in routing the received wireless sensor network data.

In a further embodiment of the invention the node is configured to allocate a temporary network address for the mobile device. The node may be configured to exchange the network address of the node with the temporary address of the mobile device. After that, the exchange messages from the wireless sensor network are directed to the mobile device instead of the node. In a further embodiment of the invention the node is configured to submit the routing table to the mobile device. In order to save energy it is possible to con^¬ figure the node to change into a sleeping mode after the exchange. The node may be woken up by receiving a wake up message from the mobile device, wherein the message comprises the exchanged temporary address. The wake up message is sent, for example, when the mobile device is leaving the network. In a further embodiment of the invention a timer is configured to expire after a certain period of sleep. Upon expiration the node may check if the mobile device is still operating as a replacement .

In an embodiment of the present invention a mobile device with a transceiver for transmitting data in a wireless sensor network is detected by an appara- tus, such as a node of a wireless sensor network, configured to route data in the wireless sensor network in accordance with a routing table. The node instructs the detected mobile device to temporarily replace the node for routing data in a wireless sensor network. In an embodiment of the invention the node further allocates a temporary address for the mobile device. The allocated temporary address is then exchanged so that the mobile device is using the original address of the node and the node is using the temporary address allocated for the mobile device. During the exchange the original address information is stored for a later restoring procedure. In an embodiment of the invention the routing table of the node is submitted to the mo- bile device.

In a further embodiment of the invention the node is changed into a sleep mode after finishing the exchange. The sleeping node may be woken up by receiv^¬ ing a wake up message when the mobile device is leav- ing the wireless sensor network or, for example, by expiration of a timer.

In an embodiment of the invention the above described method is implemented as a computer program that is embodied on a computer readable medium. The computer program is configured to carry out the method when executed in a computing device such as the appa^¬ ratus described above.

In an embodiment of the invention an apparatus, such as a mobile device, having at least one con- ventional network connection, such as a second or third generation mobile communication network, a wireless local area network, LTE (Long Term Evolution) , LTE-Advanced, or similar is used. In addition to the conventional network the mobile device comprises a transceiver for the wireless sensor network. The transceiver may be shared with one or more conven^¬ tional networks. The mobile device further comprises a processor for executing at least one computer program, a memory for storing a routing table and program code and data of the at least one computer program. The mobile device is configured to temporarily replace a de- vice routing data in a wireless sensor network by receiving data using the transceiver and by forwarding the received data by using at least one network connection. The mobile device is configured to receive a request, for example in the form of a beacon message, for the temporary replacement and respond to the request. The mobile device may be configured to advertise the replacement when detecting a wireless sensor network. In a replacement procedure according to the present invention the mobile device is configured to receive a temporary address from an apparatus in the wireless sensor network. The temporary address is ex^¬ changed later during the replacement procedure; how^¬ ever, the mobile device saves the temporary address for later use. The later use may be, for example, a wake up message to the node of the wireless sensor network that has been replaced. As the mobile device is the only one that knows the temporary address the risk of false wake ups is very low.

In an embodiment of the invention a request for replacing a device routing data in a wireless sen^¬ sor network is received by a mobile device. The mobile device is then configured in accordance with the re^¬ quest; however, the device may also be configured in such way that it waits after receiving the request as there may also be other devices responding to the request. If the device hears a response to the request it stays silent. If it responds to the message, it will start routing wireless sensor network messages in accordance with the configuration. In an embodiment the possibility for replacement is advertised. When a mobile device detects a wireless sensor network that it can serve, it sends an advertisement broadcast. When a mobile device receives a request for replacement, it decides whether to respond to the message or not. For example, it may listen to other devices for their possible response. If other devices respond, the mobile device will ignore the response. If it cannot hear any other responses and is capable of acting as a replacement, it will respond to the request. After responding to the request it will receive a temporary address from a node of a wireless sensor network. Dur- ing the replacement procedure it may receive a routing table. Then it will exchange addresses with the node of the sensor area network. The mobile device will store the address for later use, such as for waking up the node if it is turned into a sleeping mode.

In an embodiment of the invention the above described method is implemented as a computer program that is embodied on a computer readable medium. The computer program is configured to carry out the method when executed in a computing device such as the appa- ratus described above.

In an embodiment of the invention a system comprising a base station of a mobile communication network, at least one mobile device and at least one wireless sensor network node is used. In an embodiment of the invention the mobile communication network is an LTE or LTE-Advanced network and the mobile device is a user equipment capable of communicating with such a network.

The embodiments described above provide a mechanism for replacing a node of a wireless sensor network. This will save energy of the replaced node as it can be turned into a sleep mode or at least the need for routing communication from child nodes is reduced as they will communicate directly to the mobile device that will send the information to the gateway. The above mentioned embodiments are capable of performing the replacement without changes in the network topology of the wireless sensor network. Thus, a parent node being replaced need not inform child nodes about the replacement as child nodes may continue using the previous address. This reduces energy consump- tion and improves the operating time of the wireless sensor network.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

Fig. 1 is a block diagram of an embodiment according to the present invention,

Fig. 2 is a flowchart of an embodiment according to the present invention, and

Fig. 3 is an illustration of a frame structure according to an embodiment of the present invention .

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Figure 1 discloses a block diagram of an embodiment according to the present invention. In the embodiment two different networks are used. The mobile communication network comprises a base station 10 and two mobile devices 11 and 12. The network may be any type of mobile network, such as an LTE-network (Long Term Evolution) . Devices 11 and 12 are capable of com- municating with a base station from a distance. The maximum distance varies according to the characteris- tics and configuration of the used network. In the case of device 11 it is illustrated that the device comprises a processor 13, a memory 14, a transceiver for communicating with wireless sensor network 15 and a network connection 16 for communicating with the base station 10. The corresponding components are also arranged to device 12; however, they are not drawn for the sake of clarity. Nodes A - H typically have a processor, a memory and a transceiver; however, they often do not have an additional network connection but communicate only by using the transceiver wireless sensor network. The hotspot node X comprises an additional network connection that can be any type of network connection. If the node X does not perform any measurements it is possible to use a device similar to mobile devices 11 and 12.

The second network is a wireless sensor network arranged into a form of a tree. The wireless sensor network comprises nodes A - H and a hotspot node X The wireless sensor network is configured in a manner that the child nodes always send all communications to the parent until node X is reached. Node X is capable of sending the information, for example, to a mobile communication network via a gateway. As hotspot node X is responsible for forwarding all messages received from nodes A - H, the energy consumption of node X is higher than in nodes A - H and it often runs out of energy.

In the following it will be explained how the replacement procedure according to the present invention is implemented. For example, in figure 1 the traffic passed through node X can be reduced with an arrangement wherein the node X is replaced by a mobile device, such as a UE in a LTE network. It can be seen from the figure that nodes A and B start sending all their information to mobile device 11. In figure 1 it is further illustrated that node A is replaced by a mobile device 12. Thus, nodes C and D start sending their information to the mobile device 12. In the embodiment according to figure 1 these replacements are performed in a manner that the nodes A and B do not know that node X has been replaced. Correspondingly, nodes C and D do not know that node A has been replaced by the mobile device 12. The above described replacements can occur simultaneously.

Figure 2 discloses a signaling chart accord- ing to an embodiment of the present invention. The embodiment discloses signaling wherein the replacement procedure according to the present invention is initiated by the hotspot node, such as the node X in figure 1. In the chart the first signal 20 is sent from a child node, such as the node A of figure 1, to the node X. The signal comprises ordinary communication in accordance with the purpose of the node A. Then node X detects that its residual energy is lower than a threshold and it broadcasts signal 21. The broadcast signal 21 comprises a beacon for finding a UE (User Equipment} by using corresponding power P_ex, which can guarantee that the UE can communicate with the node X and the node A successfully with normal wireless sensor network transmission power P₀. All of the UEs that listened and received this broadcasted beacon will set a timer and count down according to the signal noise ratio and delay. The UE whose timer expires the earliest will send an ACK (acknowledgment), signal 22, to the node X, while the other UEs which are hearing the ACK will keep silent. Thus, the UE that responded to the beacon will replace node X.

After node X has received the acknowledgement signal, it allocates a temporary address to the UE by using temporary connection signaling, signal 23. The UE sends an acknowledgment signal 24 as a response. Then node X sends a configuration message to the UE, signal 25. This message includes in this embodiment the 16-bit short address and routing table of node X, and any other relevant information, or other information with which the communication can be routed during the temporary replacement. The UE responds to the sig- nal by sending an acknowledgement signal 26. After receiving signal 26, the node X changes to the sleep mode, but it keeps the configuration message, such as the short address and routing table. At the corresponding time the UE sets the received 16-bit address as its short address and starts using the routing table received from node X. This makes the UE a duplication of node X. For activating node X later, the UE does not release the temporary address.

During communication node A sends a signal 27 that is intended to be received by node X; however, as it is replaced by the UE, the signal 27 is not re^¬ ceived by the node X as it is in the sleep mode. The UE then sends the message carried by signal 27 in signal 28 to the mobile network so that it can be trans- mitted to the final destination.

The signaling disclosed in figure 2 is only an exemplary embodiment. The signaling may vary depending on the implementation requirements. Furthermore, the functionality provided by the present inven- tion may also be initiated by the UE. For example, when the UE notices that it can receive transmissions from a wireless sensor network, it may send a broadcast advertising the possibility of the replacement procedure. It is possible that one or more sensors transmit a response to the broadcast. In the signaling according to figure 2 the node X was replaced; however, as can be seen from figure 1, nodes A and B may be re^¬ placed as well. Thus, there may be a need for further signaling if nodes A and B are not aware of the route from node X to the mobile network.

Figure 3 discloses a signaling chart according to an embodiment of the present invention. The signaling of figure 3 is used when the UE is leaving the area and cannot serve the wireless sensor network anymore. The signal 30 comprises ordinary data transmission. Then the UE is about to leave the area. The UE reuses the temporal address and activates the node X by sending a leaving message, signal 41. This message includes identification of the UE. The node X sends an acknowledgement message, signal 32, to the UE and reuses the 16-bit short address and the routing table. The node A continues sending signals comprising ordinary data, signal 33. As can be seen from the figure, the node X receives and forwards the signal and the UE remains silent. The node A does not need to make any changes as it needs not be aware of the replacement .

The signaling described in figure 2 and 3 may be altered if the replacement procedure is applied to a node such as node A in figure 1 and node A is also a node making measurements. Typically the results of these measurements are sent to node X, or to the UE that has replaced node X as disclosed in figure 1. It is the nature of the measurement that dictates if the results must be sent immediately or if it is possible to temporarily store them in the node and send when replacement of the node is terminated and communication is continued as in the normal situation.

The above mentioned method may be imple^¬ mented as computer software which is executed in a network element, such as the network element disclosed above. When the software is executed in a computing device it is configured to perform the above described inventive method in order to facilitate discovery re^¬ sources in a mobile communication network. The software is embodied on a computer readable medium so that it can be provided to the computing device.

As stated above, the components of the exemplary embodiments can include a computer readable me- dium or memories for holding instructions programmed according to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein. The computer readable medium can include any suitable medium that participates in providing instructions to a processor for execution. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, transmission media, and the like. Non-volatile media can include, for example, optical or magnetic disks, magneto-optical disks, and the like. Volatile media can include dynamic memories, and the like. Transmission media can include coaxial cables, copper wire, fiber optics, and the like. Transmission media can also take the form of acoustic, optical, electromagnetic waves, and the like, such as those generated during radio frequency (RF) communications, infrared (IR) data communications, and the like. Common forms of computer-readable media can include, for example, a floppy disk, flexible disk, hard disk, magnetic tape, any other suitable magnetic medium, CD-ROM, CD+R, CD+RW, DVD, DVD-RAM, DVD+RW, DVD+R, HD DVD, HD DVD-R, HD DVD-RW, HD DVD-RAM, Blu-ray Disc, any other suitable optical medium, RAM, PROM, EPROM, FLASH-EPROM, any other suitable memory chip or cartridge, carrier wave or any other suitable medium from which a computer can read.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

Claims

WHAT IS CLAIMED IS :

1. An apparatus comprising:

a transceiver for transmitting data in a wireless sensor network, wherein said apparatus is configured to route data received with said network connection in accordance with a routing table stored in said apparatus ;

a processor for executing at least one computer program; and

a memory for storing said routing table, program code and data of said at least one computer program; wherein said apparatus is configured to detect a mobile device with a transceiver for transmitting data in a wireless sensor network and to instruct said detected mobile device to temporarily replace said apparatus in routing said received wireless sensor network data .

2. An apparatus according to claim 1, wherein said apparatus is configured to allocate a temporary network address for said mobile device.

3. An apparatus according to claim 2, wherein said apparatus is configured to exchange the network address of said apparatus with said temporary address of said mobile device.

4. An apparatus according to claim 1 or 2, wherein said apparatus is configured to submit said routing table to said mobile device.

5. An apparatus according to any of preceding claims 1 - 4, wherein said apparatus is configured to change into a sleeping mode after said exchange.

6. An apparatus according to claim 5, wherein said apparatus is configured to receive a wake up mes^¬ sage from said mobile device, wherein said message comprises said exchanged temporary address.

7. An apparatus according to any of preceding claims 1 - 6, wherein said apparatus is configured to detect said mobile device by sending a broadcast signal requesting replacement.

8. A method comprising:

detecting a mobile device with a transceiver for transmitting data in a wireless sensor network by an apparatus configured to route data in said wireless sensor network in accordance with a routing table; and instructing said detected mobile device to temporarily replace said apparatus for routing data in a wireless sensor network.

9. A method according to claim 8, wherein the method further comprises allocating a temporary address for said mobile device.

10. A method according to claim 9, wherein the method further comprises exchanging the address of said apparatus with said temporary address of said mo^¬ bile device.

11. A method according to any of preceding claims 8 - 10, wherein the method further comprises submitting said routing table to said mobile device.

12. A method according to any of preceding claims 8 - 11, wherein the method further comprises changing into a sleep mode.

13. A method according claim 12, wherein the method further comprises receiving a wake up message.

14. A method according to any of preceding claims 8 - 12, wherein said detecting further comprises sending a broadcast signal requesting replacement .

15. A computer program comprising code adapted to carry out the following when executed on a data-processing system:

16. A computer program according to claim 15, wherein said computer program is stored on a computer readable medium.

17. An apparatus comprising:

a transceiver for transmitting data in a wireless sensor network, wherein said apparatus is configured to route data received with said transceiver in accordance with a routing table stored in said apparatus; at least one network connection;

a processor for executing at least one computer program; and

a memory for storing said routing table and program code and data of said at least one computer program;

wherein said apparatus is configured to temporarily replace a device routing data in a wireless sensor network by receiving said data using said transceiver and by forwarding said data by using said at least one network connection.

18. An apparatus according to claim 17, wherein said at least one network connection comprises a mobile network connection.

19. An apparatus according to claim 18, wherein said mobile network connection is an LTE- connectio .

20. An apparatus according to any of preceding claims 17 - 19, wherein said at least one network connection comprises a wireless local area network connection .

21. An apparatus according to any of preceding claims 17 - 20, wherein said apparatus is config^¬ ured to receive a request for said temporary replacement and respond to the request.

22. An apparatus according to any of preceding claims 17 - 21, wherein said apparatus is configured to advertise the replacement when detecting a wireless sensor network.

23. An apparatus according to any of preceding claims 17 - 22, wherein said apparatus is configured to receive a temporary address from an apparatus in said wireless sensor network.

24. An apparatus according to claim 23, wherein said apparatus is configured to exchange said temporary address with the address of said apparatus in said wireless sensor network.

25. An apparatus according to claim 24, wherein the apparatus is further configured to send a wake up message to said apparatus in said wireless sensor network by using said temporary address.

26. A method comprising:

receiving a request for replacing a device routing data in a wireless sensor network by a mobile device; configuring said mobile device in accordance with the request;

routing wireless sensor network messages in accordance with said configuration.

27. A method according to claim 26, wherein the method further comprises advertising replacement when detecting a wireless sensor network.

28. A method according to claim 25 or 26, wherein the method further comprises receiving a request for said temporary replacement and responding to the request.

29. A method according to any of preceding claim 26 - 28, wherein the method further comprises receiving a temporary address from an apparatus in said wireless sensor network.

30. A method according to any of preceding claims 26 - 29, wherein the method further comprises exchanging said temporary address with the address of said apparatus in said wireless sensor network.

31. A method according to claim 30, wherein the method further comprises submitting a wake up message to said apparatus in said wireless sensor network by using said temporary address.

32. A computer program comprising code adapted to carry out the following when executed on a data-processing system:

routing wireless sensor network messages in accordance with said configuration.

33. A computer program according to claim 32, wherein said computer program is stored on a computer readable medium,

34. A system comprising:

a mobile communication network comprising at least one base station connected to a core network;

at least one apparatus according to any of claims 1 - 7 ; and

at least one apparatus according to any of claims 17 - 25.

35. A system according to claim 34, wherein said mobile communication network is an LTE network.