WO2013071478A1

WO2013071478A1 - A method and an apparatus for assisting operation of a wireless sensor network

Info

Publication number: WO2013071478A1
Application number: PCT/CN2011/082163
Authority: WO
Inventors: Zhenhong Li; Haifeng Wang; Honglin Hu; Ying Hu; Lianhai SHAN
Original assignee: Renesas Mobile Corporation
Priority date: 2011-11-14
Filing date: 2011-11-14
Publication date: 2013-05-23

Abstract

The invention concerns a method and an apparatus for assisting operation of a wireless sensor network. The method comprises receiving first data from a first wireless sensor network node of a wireless sensor net- work, the first data being intended for a second wire- less sensor network node of the wireless sensor net- work; receiving a first acknowledgement in response to the first data from the second wireless sensor network node; and transmitting transmission termination sig- naling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node.

Description

A METHOD AND AN APPARATUS FOR ASSISTING OPERATION OF A

WIRELESS SENSOR NETWORK

FIELD OF THE INVENTION

The invention relates to a Wireless Sensor Networks (WSN) . More particularly, the invention concerns a method and an apparatus for assisting opera^¬ tion of a wireless sensor network.

BACKGROUND OF THE INVENTION

A wireless sensor network (WSN) is a network that consists of spatially distributed sensors that monitor physical or environmental conditions, for ex^¬ ample motion, temperature or sound. The wireless sen^¬ sor network is built of wireless sensor network nodes, where each node is connected to one or more sensors. Each node is typically equipped with a radio trans^¬ ceiver, a microcontroller, a circuitry for interfacing with the sensor (s) and an energy source (for example a battery) .

The topology of a wireless sensor network may vary, being for example a belt-shaped topology, a lin^¬ ear topology, a star topology etc. Figure 1 discloses a simplified wireless sensor network with a linear to^¬ pology. The network includes a sink node 106 and sev- eral nodes 100-104. For example, data to be trans^¬ ferred from the WSN node 100 to the sink node 106 is performed such that the node 100 first transmits the data to the node 102, the node 102 then transmits the same data to the node 104 etc. This will go on until the data reaches the sink node 106. The sink node 106 will forward the data for further processing.

WSN topologies, for example, the belt-shaped topology and the linear topology, may have certain special features such as long delay, unique routing, and a large number of hops from WSN nodes to the sink node .

When a WSN node is far from the sink node, i.e. node 100, it will transmit its information to the sink node via a significant number of hops, and this will cause energy consumption for each of the nodes and a long transmission delay. Furthermore, sensor nodes close to the sink node would forward data more than the nodes far from the sink node and their energy will be exhausted more quickly, which will at some point cause a disconnection problem for the wireless sensor network.

It would be beneficial to solve or at least alleviate the above drawbacks and to provide a solu- tion which would reduce energy consumption and/or transmission delay in a wireless sensor network.

SUMMARY OF THE INVENTION :

According to a first aspect of the invention, there is provided a method, comprising receiving with an apparatus, first data from a first wireless sensor network node of a wireless sensor network, the first data being intended for a second wireless sensor net^¬ work node of the wireless sensor network; receiving, with the apparatus, a first acknowledgement in re^¬ sponse to the first data from the second wireless sen^¬ sor network node; and transmitting, with the apparatus, transmission termination signaling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node.

In one embodiment, the method further com^¬ prises transmitting, with the apparatus, the first da^¬ ta received from the first wireless sensor network node to a cellular base station. In one embodiment, after transmitting trans^¬ mission termination signaling, the method further comprises: receiving, with the apparatus, second data from the first wireless sensor network node; transmit- ting, with the apparatus, a second acknowledgement to the first wireless sensor network node in response to receiving the second data; and transmitting, with the apparatus, the second data received from the first wireless sensor network node to the cellular base sta- tion.

In one embodiment, the method further com^¬ prises transmitting, with the apparatus, a leaving signaling message to the first wireless sensor network node, the signaling message indicating to the first wireless sensor network node to initiate recovery sig^¬ naling with the second wireless sensor network node.

According to a second aspect of the invention, there is provided an apparatus comprising a wireless sensor network transceiver configured to receive first data from a first wireless sensor network node of a wireless sensor network, the first data being intended for a second wireless sensor network node of the wire^¬ less sensor network; to receive a first acknowledge^¬ ment in response to the first data from the second wireless sensor network node; and to transmit trans^¬ mission termination signaling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node.

In one embodiment, the apparatus further com- prises a cellular transceiver configured to transmit the first data received from the first wireless sensor network node to a cellular base station.

In one embodiment after transmitting trans^¬ mission termination signaling, the wireless sensor network transceiver is configured to receive second data from the first wireless sensor network node and to transmit a second acknowledgement to the first wireless sensor network node in response to receiving the second data; wherein the cellular transceiver is configured to transmit the second data received from the first wireless sensor network node to the cellular base station.

In one embodiment, the wireless sensor net^¬ work transceiver is configured to transmit a leaving signaling message to the first wireless sensor network node, the signaling message indicating to the first wireless sensor network node to initiate recovery sig^¬ naling with the second wireless sensor network node.

According to third aspect of the invention, there is provided a modem comprising the apparatus of the second aspect of the invention.

According to fourth aspect of the invention, there is provided user equipment comprising the appa^¬ ratus of the second aspect of the invention.

According to a fifth aspect of the invention, there is provided a system comprising a wireless sen- sor network node comprising a first wireless sensor network node configured to send first data to a second wireless network node and a second wireless network configured to send a first acknowledgement to the first wireless sensor network node in response to re- ceiving the first data; an apparatus configured to re^¬ ceive the first data from the first wireless sensor network node and the first acknowledgement from the second wireless sensor network node; wherein the appa^¬ ratus is configured to transmit transmission termina- tion signaling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node.

In one embodiment, the apparatus is config^¬ ured to transmit the first data received from the first wireless sensor network node to a cellular base station . In one embodiment, the first wireless sensor network node is configured to send second data to the second wireless sensor network node; the apparatus is configured to receive the second data from the first wireless sensor network node; and the apparatus is configured to transmit a second acknowledgement to the first wireless sensor network node in response to re^¬ ceiving the second data and to transmit the second da^¬ ta received from the first wireless sensor network node to the cellular base station.

In one embodiment, the apparatus is config^¬ ured to transmit a leaving signaling message to the first wireless sensor network node, the signaling mes^¬ sage indicating to the first wireless sensor network node to initiate recovery signaling with the second wireless sensor network node; and the first wireless sensor network node is configured to receive the leav^¬ ing signaling message and to transmit recovery signal^¬ ing message to the second wireless sensor network node for instructing the second wireless sensor network node to return back to its normal working state.

In one embodiment, the network topology of the wireless sensor network node is belt-shaped or linear. The embodiments of the invention described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined to^¬ gether to form a further embodiment of the invention.

The benefits of at least some embodiments of the invention are related to reduced energy consump- tion of the wireless sensor network nodes and reduced transmission delay 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, illus^¬ trate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

Fig. 1 discloses a simplified wireless sensor network with a linear topology;

Fig. 2 illustrates a user equipment assisted wireless sensor network according to one embodiment of the invention;

Fig. 3 is a flow diagram illustrating user equipment assisted packet transmission process accord- ing to one embodiment of the invention;

Fig. 4 is a block diagram illustrating a method performed by an apparatus according to one em^¬ bodiment of the invention;

Figs. 5A and 5B illustrate a comparison be- tween a normal situation in a wireless sensor network using CSMA-CA and a user equipment assisted situation in a wireless sensor network according to one embodiment of the invention; and

Fig. 6 is a block diagram illustrating an ap- paratus according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS:

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

Figure 2 illustrates a user equipment as^¬ sisted wireless sensor network according to one embodiment of the invention. The wireless sensor network comprises multiple wireless sensor network nodes 200- 204 and a sink node 206. In this exemplary embodiment, WSN node 202 is within the range of user equipment 208 having an interface for communicating with WSN nodes. Instead of using a hop-by-hop method to transfer data from node 202 to node 204 and further to the sink node 206, the user equipment 208 transmits data received from the WSN node 202 to a base station 210 via its cellular interface. The base station may be a base station or a similar network element of any wireless network or a wireless telephone network, for example a base station of a Global System for Mobile Communica^¬ tions (GSM) network, Wideband Code Division Multiple Access (WCDMA) network, Long Term Evolution (LTE) etc.

In the embodiment disclosed in Figure 2, data is transmitted only in one direction, as indicated with arrow 212, and the topology of the WSN is belt- shaped or linear. In other embodiments, the topology of the wireless sensor network may be other than the belt-shaped or linear.

Figure 3 is a flow diagram illustrating user equipment assisted packet transmission process accord^¬ ing to one embodiment of the invention. A wireless sensor network (WSN) comprises a plurality of WSN nodes 300, 304, 306, 308. The number of WSN nodes is not limited to the number disclosed in Figure 3. In this example, one of the WNS nodes is a sink node 308. A sink node in a WNS is a node which receives data (for example, sensor data) from other WNS nodes and forwards the data for further processing.

In the embodiment disclosed in Figure 3 user equipment 302 is equipped with a wireless WSN inter^¬ face (in addition to a cellular interface) with which it is able to communicate also with WNS nodes which are within the range of the wireless communication in^¬ itiated via the wireless WSN interface (as generally disclosed in Figure 2) . In other words, the user equipment 302 is able to monitor/hear WSN channels. A block 312 illustrates that the user equip^¬ ment 302 listens to data transmissions of WSN nodes within its WSN communication range. In this embodiment, the user equipment 302 learns that the WNS node 300 sends a data frame 314 to the WSN node 304, and that the WSN node 304 sends an acknowledgement frame 316 to the WSN node 300 in response to receiving the data frame. The data frame is intended to be delivered to the WSN sink node 308 hop-by-hop through the chain of the WNS nodes.

However, before the WSN node 304 starts send^¬ ing the data frame to the next-hop node, the user equipment 302 broadcasts termination signaling 318 and instructs the WNS node 304 to cease receiving any frames except beacon frames. Instead of broadcasting the user equipment 302 may perform the transmission as a unicast transmission to the WSN node 304. When the WSN node 304 receives the termination signaling, it enters to an idle state where it listens only to peri- odical beacon frames. In other words, the WSN node 304 does not receive or hear any data frames from the WSN node 300 after receiving the termination signaling from the user equipment 302. However, if the WSN node 304 itself has data frames (for example, sensor data from its own sensor (s) ) to be transmitted to the next hop node, i.e. the WSN node 306, the WSN node 304 will return to a normal working state for the duration of the data transmission. However, in this state, the WSN node 304 still remains not to receive any data frames from the WSN node 302 except the periodical beacon frames .

In a block 320 the user equipment 302 continues to listen/overhear data frames sent by the WSN node 300. The WSN node 300 sends 322 a new data frame or data frames. While the WSN node 304 does not re^¬ ceive them as instructed, the user equipment 302 re^¬ ceives them and sends 324 an acknowledgement frame to the WSN node 300. When the WSN node 300 sends the data frame, it may not know the user equipment 302 is re^¬ ceiving the data frame and acknowledging it back to the WSN node 300. Thus, in one embodiment, the user equipment poses towards the WSN node 300 as if it was the WSN node 304. After sending 324 the acknowledge- ment frame, the user equipment 302 forwards 326 all the received data frames from the WSN node 300 to a base station 310 of a cellular telephone network. The data sent by the user equipment 302 to the base sta^¬ tion 310 may also comprise data that identifies the final recipient (i.e. the entity to which the data should be forwarded) for the base station 310. The base station 310 then transmits them to an appropriate server for further processing (not disclosed in Figure 3) .

At some point, the user equipment 302 is leaving 328 the area within which it can receive and transmit information from/to the WSN node 300. Before leaving the area, the user equipment 302 sends 330 leaving signaling to the WSN node 300, the leaving signaling indicating to the WSN node 300 to initiate recovery signaling with the WSN node 304. In response to receiving the leaving signaling, the WSN node 300 sends 332 a recovery beacon signal to the WSN node 304 to instruct the WSN node 304 to return to its normal working state. After receiving the recovery beacon signal from the WSN node 300, the WSN node 304 exits the idle state where it listened only to the periodi^¬ cal beacon frames. When the WSN node 300 sends 334 da^¬ ta frames again, the WSN node 304 again receives them, acknowledges 336 them, and transmits 338 them wire- lessly to its next hop node (WSN node 306 in this ex^¬ ample) . The next hop node acknowledges 340 the re^¬ ceived data frames back to the WSN node 304. Finally the data frames reach after steps 342 and 344 the WSN sink node 308, which either processes the received in^¬ formation by itself or forwards the information for further processing to another entity.

When an apparatus, for example, user equip- ment of a cellular network as disclosed in the embodi^¬ ment of Figure 3, is used to terminate data transmis^¬ sion of a wireless sensor network, this will reduce energy consumption of the wireless sensor network nodes, since less data need to be transmitted by the wireless sensor network nodes. Nodes that are closer to the sink node transmit more data frames as nodes farther from the sink node. At some point, this may lead to a disconnection problem when operating power of these closer nodes run out. When user equipment is used to terminate the data transmission, less data need to be transmitted between the wireless sensor network nodes. Furthermore, when the apparatus is also used to forward the detected data frames to a base station of a cellular network, this will reduce trans- mission delay of the wireless sensor network since the data frames need not be transmitted in the wireless sensor network hop-by-bop through the chain the nodes.

In another embodiment, the user equipment 302 does not send the data frame 314 received from the WSN node 300 via its cellular interface to the base sta^¬ tion. Instead, the WSN node 304 sends the data frame to its next hop node, the WNS node 306. Thus, the user equipment 302 does not send the termination signaling message to the WSN node 304 immediately after receiv- ing. Instead, it waits a predetermined time before sending the message to the WSN node 304. In another embodiment, the user equipment 302 may, for example, overhear that the WSN node 304 sends the data frame 314 further to its next hop node, the WSN node 306. After learning this, the user equipment 302 may send the termination signaling message to the WSN node 304.

A data frame sent by the WSN nodes and the user equipment comprises, for example, measured sensor data. It may also comprise other information pieces that need to be sent further. Furthermore, it is evi^¬ dent that the data frame may comprise also other piec^¬ es of data, for example, identification data (relating to sender and/recipient ) etc. The data frame may also identify a server that it used to further process the data frame .

Although Figure 3 and its description teach that only a single data frame is transmitted at a time, one or more data frames may be simultaneously trans- mitted. Furthermore, the messaging structure with which data is actually sent may be any appropriate structure .

Figure 4 is a block diagram illustrating a method performed by an apparatus according to one em- bodiment of the invention.

In step 400 the apparatus receives a data frame from a first wireless sensor network (WNS) node. The intended recipient of the data frame is a second WSN node, which in response to receiving the data frame, sends an acknowledgement frame to the first WSN node. The apparatus receives or overhears also this acknowledgement frame, step 402. After overhearing the acknowledgement frame, the apparatus transmits termi^¬ nation signaling to the second WSN node, instructing the second WSN to cease receiving all other frames ex^¬ cept beacon frames. The transmission may be imple^¬ mented e.g. by broadcasting or unicasting the termination signaling.

In step 406 the apparatus determines whether a new data frame has been received from the first WSN node. If no data frames are received and the apparatus does not leave (408) the coverage area within which the first WSN node is reachable, the apparatus remains in the data frame waiting mode.

If a data frame is received from the first WSN node, the processing proceeds to step 410, where the apparatus sends an acknowledgement frame to the first WSN node. In step 412 the apparatus transmits all the received data frames from the first WSN node to a cellular base station. In one embodiment, the ap^¬ paratus poses towards the first WSN node as if it was the second WSN node. In another embodiment, the appa^¬ ratus may indicate to the first WSN node its real identity.

In step 414 the apparatus again determines whether it is leaving the coverage area within which the first WSN node is reachable. If the apparatus is not leaving the area, processing returns back to step 406. If the apparatus is leaving the area, it trans^¬ mits leaving signaling to the first WSN node, step 416. When the first WSN node receives the leaving signaling from the apparatus, it is able to initiate sending re^¬ covery signaling towards the second WSN node.

Figure 4 illustrates an exemplary embodiment of a method according to the invention. Other embodiments of the invention may include only a portion of the steps disclosed in Figure 4. For example, another embodiment of the invention may be formed by steps 400, 402 and 404. In this embodiment the apparatus does not send the data frame received at step 400 to the cellu^¬ lar base station. Instead, the second WSN node sends it to its next hop node. Yet another embodiment of the invention may be formed by steps 400, 402, 404, 406, 410 and 412. Yet another embodiment of the invention may be formed by steps 400, 402, 404 and 412.

When an apparatus, for example, user equip^¬ ment of a cellular telephone network, is used to ter- minate data transmission of wireless sensor network, this will reduce energy consumption of the wireless sensor network nodes, since less data need to be transmitted by the wireless sensor network nodes. Fur^¬ thermore, when the apparatus is also used to forward the detected data frames to a base station of a cellu^¬ lar network, this will reduce transmission delay of the wireless sensor network. This will also bring a quality of service guarantee for wireless sensor net^¬ work emergency information transmissions.

Figures 5A and 5B illustrate a comparison be^¬ tween a normal situation in a wireless sensor network using Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA) and a user equipment assisted sit^¬ uation in a wireless sensor network according to one embodiment of the invention.

In the traditional algorithm, wireless net^¬ work sensor (WNS) nodes use the Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA) algorithm for channel contention access. Figure 5A illustrates a normal situation where a node 6 is listening beacon signals 500 at certain intervals. The time interval 506 between is called as a superframe. When a node 5 sends a data frame 502 to the node 6, the node 6 re^¬ sponds to the node 5 with an acknowledgement frame 504 The nodes delay for a random units of backoff periods (reference 508) in the range 0 to (2^BE -1) , where BE is a backoff exponent, which relates to how many backoff periods a device shall wait before attempting to ac- cess a channel. After the delay, if a Clear Channel Assessment (CCA) (reference 514) in two slots shows that the channel is idle, the node can contend it suc^¬ cessfully, as indicated with reference 512. Otherwise, the node will perform a new backoff period or declare the channel access failure. CW in the Figure 5A is the contention window length. It defines the number of backoff periods that need to be clear of channel ac^¬ tivity before the transmission can commence. This value may be initialized to two before each transmis- sion attempt and reset to two each time.

Figure 5B shows a user equipment assisted scenario. The user equipment acts as a gateway user equipment and it need not execute the CSMA-CA algo^¬ rithm. Instead, it just uses the channel preemptively, and will access the channel with the highest priority without any back-off period (non-CSMA) . Without any back-off period, the gateway user equipment has the highest priority for transmitting the termination signaling. The gateway user equipment transmits, for ex- ample broadcasts or unicasts, the transmission termi^¬ nation signaling on this channel immediately after re^¬ ceiving an acknowledgement frame from the node 6. Thus the next hop sensor nodes cannot contend the channel successfully for data transmission, as indicated with reference 518, and the energy consumption of the nodes will be reduced.

Figure 6 is a block diagram illustrating an apparatus according to one embodiment of the invention. The apparatus 600 comprises a wireless sensor network (WSN) transceiver 602 configured to receive first data from a first wireless sensor network node of a wire^¬ less sensor network, the data being intended for a second wireless sensor network node of the wireless sensor network, to receive a first acknowledgement in response to the first data from the second wireless sensor network node, and to transmit transmission termination signaling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node. The apparatus 600 may also comprise a cellular transceiver 604 configured to transmit the first data received from the first wireless sensor network node to a cellular base station. The apparatus 600 may naturally comprise one or more elements not disclosed in Figure 6, for exam^¬ ple, one or more controllers, one or more memories, an antenna, a display etc.

In one embodiment, the apparatus 600 dis- closed in Figure 6 is embodied as a modem. In another embodiment, the apparatus 600 disclosed in Figure 6 is embodied as a user equipment of a cellular telephone network .

The embodiments of the invention have been described using belt-shaped or linear topology as an example topology. The invention is not limited only to these wireless sensor network topologies. Instead, any other wireless sensor network topology may also be used .

The embodiments of the invention described hereinbefore in association with Figures 2-6 may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention. Furthermore, although Figures 2 and 3 illus^¬ trate that the user equipment listens frame transmis^¬ sions only from one wireless sensor network node. In another embodiment the user equipment may overhear transmissions from multiple wireless sensor network nodes simultaneously and transmit data frames to the base station from multiple wireless sensor network nodes .

Furthermore, although in the above embodiment it has been disclosed that the user equipment send re^¬ ceived data frame to a cellular base station, in an^¬ other embodiment, another network entity receiving a wireless transmission from the user equipment may be used instead of the cellular base station. The wire- less connection between the user equipment and the en^¬ tity may be, for example, a WLAN (Wireless Local Area Network) connection or any other wireless connection.

The exemplary embodiments of the invention can be included within any suitable device, for exam- pie, including any suitable servers, workstations, PCs, laptop computers, PDAs, Internet appliances, handheld devices, cellular telephones, wireless devices, other devices, and the like, capable of performing the proc^¬ esses of the exemplary embodiments, and which can com- municate via one or more interface mechanisms, includ^¬ ing, for example, Internet access, telecommunications in any suitable form (for instance, voice, modem, and the like) , wireless communications media, one or more wireless communications networks, cellular communica- tions networks, 3G communications networks, 4G commu^¬ nications networks Public Switched Telephone Network (PSTNs) , Packet Data Networks (PDNs) , the Internet, intranets, a combination thereof, and the like. It is to be understood that the exemplary em^¬ bodiments are for exemplary purposes, as many varia^¬ tions of the specific hardware used to implement the exemplary embodiments are possible, as will be appre- ciated by those skilled in the hardware art(s) . For example, the functionality of one or more of the com^¬ ponents of the exemplary embodiments can be imple^¬ mented via one or more hardware devices, or one or more software entities such as modules.

The exemplary embodiments can store informa^¬ tion relating to various processes described herein. This information can be stored in one or more memories, such as a hard disk, optical disk, magneto-optical disk, RAM, and the like. One or more databases can store the information regarding cyclic prefixes used and the delay spreads measured. The databases can be organized using data structures (e.g., records, tables, arrays, fields, graphs, trees, lists, and the like) included in one or more memories or storage devices listed herein. The processes described with respect to the exemplary embodiments can include appropriate data structures for storing data collected and/or generated by the processes of the devices and subsystems of the exemplary embodiments in one or more databases.

All or a portion of the exemplary embodiments can be implemented by the preparation of one or more application-specific integrated circuits or by inter^¬ connecting an appropriate network of conventional com^¬ ponent circuits, as will be appreciated by those skilled in the electrical art(s).

As stated above, the components of the exem^¬ plary embodiments can include computer readable medium or memories according to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein. 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, in- eluding but not limited to, non-volatile media, vola^¬ tile 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 also can 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. Com^¬ mon forms of computer-readable media can include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other suitable magnetic medium, a CD-ROM, CDRW, DVD, any other suitable optical medium, punch cards, paper tape, optical mark sheets, any oth^¬ er suitable physical medium with patterns of holes or other optically recognizable indicia, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other suitable memory chip or cartridge, a carrier wave or any other suit- able 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. A method, comprising:

receiving, with an apparatus, first data from a first wireless sensor network node of a wireless sen- sor network, the first data being intended for a sec^¬ ond wireless sensor network node of the wireless sen^¬ sor network;

receiving, with the apparatus, a first acknowledgement in response to the first data from the second wireless sensor network node; and

transmitting, with the apparatus, transmission termination signaling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node.

2. The method according to claim 1, the method further comprises:

transmitting, with the apparatus, the first data received from the first wireless sensor network node to a cellular base station.

3. The method according to claim 1 or 2, wherein after transmitting transmission termination signaling, the method further comprises:

receiving, with the apparatus, second data from the first wireless sensor network node;

transmitting, with the apparatus, a second ac^¬ knowledgement to the first wireless sensor network node in response to receiving the second data; and

transmitting, with the apparatus, the second data received from the first wireless sensor network node to the cellular base station.

4. The method according to any of claims 1 - 3, the method further comprising:

transmitting, with the apparatus, a leaving signaling message to the first wireless sensor network node, the signaling message indicating to the first wireless sensor network node to initiate recovery sig^¬ naling with the second wireless sensor network node.

5. An apparatus, comprising:

a wireless sensor network transceiver configured to receive first data from a first wireless sensor network node of a wireless sensor network, the first data being intended for a second wireless sensor net^¬ work node of the wireless sensor network; to receive a first acknowledgement in response to the first data from the second wireless sensor network node; and to transmit transmission termination signaling instruct- ing the second wireless sensor network node to cease receiving data from the first wireless sensor network node .

6. The apparatus of claim 5, further compris^¬ ing :

a cellular transceiver configured to transmit the first data received from the first wireless sensor network node to a cellular base station.

7. The apparatus of claim 5 or 6, wherein af^¬ ter transmitting transmission termination signaling, the wireless sensor network transceiver is configured to receive second data from the first wireless sensor network node and to transmit a second acknowledgement to the first wireless sensor network node in response to receiving the second data; wherein the cellular transceiver is configured to transmit the second data received from the first wireless sensor network node to the cellular base station.

8. The apparatus of any of claims 5 - 7, wherein the wireless sensor network transceiver is configured to transmit a leaving signaling message to the first wireless sensor network node, the signaling message indicating to the first wireless sensor net^¬ work node to initiate recovery signaling with the second wireless sensor network node.

9. A modem comprising an apparatus of any of claims 5-8.

10. User equipment comprising an apparatus of any of claims 5-8.

11. A computer program comprising code adapted to perform the method of any of claim 1 - 4 when executed by an apparatus .

12. The computer program according to claim 11, wherein said computer program is embodied on a computer readable medium.

13. A system comprising:

a wireless sensor network comprising a first wireless sensor network node configured to send first data to a second wireless network node and a second wire^¬ less network configured to send a first acknowledge^¬ ment to the first wireless sensor network node in re- sponse to receiving the first data;

an apparatus configured to receive the first data from the first wireless sensor network node and the first acknowledgement from the second wireless sensor network node;

wherein the apparatus is configured to transmit transmission termination signaling instructing the second wireless sensor network node to cease receiving data from the first wireless sensor network node.

14. The system according to claim 13, wherein the apparatus is configured to transmit the first data received from the first wireless sensor network node to a cellular base station.

15. The system according to claim 13 or 14, wherein :

the first wireless sensor network node is config^¬ ured to send second data to the second wireless sensor network node;

the apparatus is configured to receive the second data from the first wireless sensor network node; and the apparatus is configured to transmit a second acknowledgement to the first wireless sensor network node in response to receiving the second data and to transmit the second data received from the first wire^¬ less sensor network node to the cellular base station.

16. The system according to any of claims 13 - 15, wherein:

the apparatus is configured to transmit a leaving sig^¬ naling message to the first wireless sensor network node, the signaling message indicating to the first wireless sensor network node to initiate recovery sig^¬ naling with the second wireless sensor network node; and

the first wireless sensor network node is configured to receive the leaving signaling message and to trans^¬ mit recovery signaling message to the second wireless sensor network node for instructing the second wireless sensor network node to return back to its normal working state.

17. The system according to any of claims 13 16, wherein the network topology of the wireless sensor network node is belt-shaped or linear.