WO2012148395A1

WO2012148395A1 - Sensor node operational modes

Info

Publication number: WO2012148395A1
Application number: PCT/US2011/034243
Authority: WO
Inventors: Anton Nicholas Clarkson; Neel Banerjee; David R. Otis Jr.
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2011-04-28
Filing date: 2011-04-28
Publication date: 2012-11-01

Abstract

A sensor node collects sensor data. The sensor node stores sensor data in a first mode, and operates in a second mode in response to determining that the sensor node has been disturbed from an emplacement. The second mode includes uploading sensor data stored prior to operating the sensor node in the second mode.

Description

SENSOR NODE OPERATIONAL MODES BACKGROUND

[0001] Sensor networks can be used to collect and store data from sensor nodes. However, stored data can be lost when a deployed sensor is disturbed, such as when a deployed wireless sensor node is stolen and removed from the sensor network. Beyond the cost of replacing the stolen sensor node, lost data can require a data collection test to be re-run at substantial additional cost. Furthermore, lost data can be invaluable and/or irreplaceable.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0002] FIG. 1 is a block diagram of an architecture of a sensor network system including a sensor node and command node according to an example.

[0003] FIG. 2 is a block diagram of a sensor node and command node according to an example.

[0004] FSG. 3 is a flowchart of a sensor node method according to an example.

[0005] FIG. 4 is a flowchart of a command node method according to an example.

[0006] FIG. 5 is a flowchart based on operation of a sensor node system according to an example.

[0007] The present examples will now be described with reference to the accompanying drawings. In the drawings, like reference numbers may indicate identical or functionally similar elements.

DETAILED DESCRIPTION

[0008] In wireless sensor networks, each sensor node has a limited amount of power stored in its battery. Transmitting collected sensor data consumes this power and, thus, shortens the time in which the sensor node can operate without being recharged. Storing collected sensor data at the sensor node without continuously or periodically transmitting can help conserve sensor node battery power. [0009] However, the sensor data stored at the sensor node may be lost if the sensor Is stolen, removed without authorization, or otherwise disturbed from its location. A sensor node is provided that stores collected data in one mode and then, upon detecting removal from its location, the sensor wirelessiy transmits the stored sensor data so as to reduce the risk of lost data due to a stolen or removed sensor. The uploaded sensor data may be prioritized such that higher priority data is uploaded before lower priority data. A removed sensor node can transmit information associated with its location, to aid in recovery of the sensor node for retrieving stored sensor data from the sensor node. A removed sensor node can operate in a power savings mode including reduced sensor function to increase available power for communication of stored data.

[0010] FIG. 1 is a block diagram of an architecture of a sensor network system 100 including sensor nodes 102-1 10 and command node 1 18 according to an example. Sensor nodes 102-1 10 are positioned in the field and communicate with a sensor network 1 16. A command node 1 18 communicates with the sensor network 1 16. Sensor nodes 102-1 10 also can communicate directly to each other, and directly to the command node 1 18. The command node 1 18 can include the functionality of a sensor node.

[001 1] Each sensor node 102-1 10 is empiaced. For example, disturbed sensor node 1 10 is originally positioned at a node emplacement 1 12. The node emplacement position can be associated with a known geographical location, and the location can be associated with data from the corresponding sensor node 102-1 10. A node emplacement provides a stable, reliable, and stationary reference point from which valid sensor data can be collected by a sensor node. In alternate examples, a sensor node can be empiaced in a mobile platform, such that the senor node is stable and stationary with respect to the emplacement for collecting valid sensor data, although the mobile platform can be non-stationary. An emplacement can provide a reliable reference point for collecting valid sensor data.

[0012] It is possible to determine that sensor nodes 102-1 10 are disturbed from their emplacement positions. For example, disturbed sensor node 1 10 can use an accelerorneter or other sensor within the node to detect unexpected acceleration such as the node being picked up, moved, or otherwise disturbed from an emplacement in which the sensor node was deployed/positioned to collect sensor data. Alternate detection can be used, such as a sound, pressure, GPS, or light sensor associated with a sensor node 102-1 10 to detect that the sensor node 102-1 10 is disturbed from its emplacement/deployment. Sensor nodes can include equipment to sense ground acceleration signals, position, temperature and other environmental conditions, and sensor-head orientation against gravity vector. Such equipment can be used to detect emplacement/deployment disturbances. Furthermore, command node 1 18 can monitor sensor nodes 102-1 10 and determine that a node has been disturbed. For example, command node 1 18 can determine a disturbance based on quality control data or other information generated by the node (e.g., without requiring a separate sensor that is used for disturbance detection) Sensor nodes 102-1 10 similarly can determine a disturbance based on collected sensor data, with or without feedback from command node 1 18.

[0013] The disturbed sensor node 1 10 can enter a theft mode based on the determination that it has been disturbed. Deployment disturbances include disturbances that threaten stored data, such as attempts to tamper with a sensor node even though the sensor node remains positioned at its deployment. The theft mode includes uploading stored sensor data 1 14. The stored sensor data 1 14 can be uploaded to the command node 1 18, to the sensor network 1 18, and/or to another sensor node 102-108. The disturbed sensor node 1 10 can use wireless communication 120 to transmit the stored sensor data 1 14, and any other data such as sensor node status data. Thus, stored sensor data 1 14 can be retrieved from disturbed sensor node 1 10 before the disturbed sensor node 1 10 loses communication with the sensor network 1 16 or other sensor nodes 102-108 and command node 1 18.

[0014] FIG. 2 is a block diagram 200 of a sensor node 202, sensor network 214, and command node 216 according to an example. Sensor node 202 is in communication with sensor network 214 and command node 218.

[0015] Sensor node 202 includes sensor module 206, data storage module 208, processor module 210, and transceiver module 212. Sensor node 202 collects sensor data 204 at sensor module 206. Sensor module 208 can be an accelerometer, for example. Sensor data 204 is stored by the sensor node 202 at data storage module 208. Data storage module 208 can be a non-volatile memory such as flash memory, hard disk or solid-state drive (SSD), for example. The processor module 210 can determine that the sensor node 202 has been disturbed from its deployment, and operate the sensor node 202 in theft mode in response to the determination. The processor module 210 can be one or more processors such as a microprocessor, for example. Transceiver module 212 can transmit stored sensor data 224 from data storage module 208 (e.g., after validating operation of the sensor node 202 in theft mode). The transceiver module 212 can be a radio transmitter and receiver operable with a wireless local area network (WLAN), for example.

[0016] Transceiver module 212 can also transmit quality control information 228, which can be a subset of sensor data, or a representation or summary associated with sensor data. Quality control information 228 can be calculated by processor module 210 based on incoming sensor data 204 and/or previously stored sensor data that is stored in the data storage module 208. Quality control information 228 can be periodically generated by sensor module 206, and can be derived from collected sensor data 204 and/or from stored sensor data 224 in data storage module 208. For example, quality control information 228 can include a statistical summary of the sensor data, such as peak amplitude and/or root mean square (RMS) of the sensor data and other statistical representations of aggregate sensor data. Quality control information 228 can be a reduced precision representation that is used by survey control to verify that a sensor node sensed a response to test data, e.g., sensed seismic data in response to vibroseis sweeps or dynamite shots used to generate vibrational activity. Thus, quality control information 228 can inform survey control whether it would be desirable to re-fire the shot, without needing to offload or analyze stored sensor data 224 from the sensor node 202. Quality control information 228 can provide a "snapshot" of statistical sampling, updated periodically and more frequently (e.g., every second) compared to offloading of stored sensor data 224 from the sensor node 202. The quality control information 228 can be grouped prior to upload (e.g., grouped into multi-second chunks), to balance wireless communication overhead and latency of data transmission of the quality control information 228.

[0017] Sensor node 202 can evaluate communication connection 234, and reconnect or use a different connection to maintain and/or strengthen communication. Communication, including upload of stored sensor data 224, can be based on the type of network. Communication can be with an access point including command node 218 in an infrastructure-based network, or with other nearby nodes in an ad-hoc or mesh-based-network.

[0018] An infrastructure-based network can use Point Coordination Function (PCF), a Media Access Control (MAC) technique used in IEEE 802.1 1 - based wireless local area networks (WLANs). PCF resides in an Access Point (AP), to coordinate the communication within the Basic Service Set (BSS). The normal PCF polling scheme can be dynamically modified to provide priority airtime to sensor nodes in theft mode, to increase the potential amount of stored sensor data 224 collected from the stolen sensor node before the stolen sensor node travels out of communication range. Once a sensor node travels out of range of the associated access point, the sensor node 202 can evaluate communication connection 234 and attempt to associate to the next best connection and/or access point/node. The sensor node 202 can identify itself to the connection as a stolen node and continue the upload process.

[0019] Sensor node 202 can operate in a mesh network, such as when sensor node 202 includes a listening wireless network interface (e.g., transceiver module 212). A stolen node operating in theft mode can broadcast a message indicating that it is operating in theft mode, and connect to the highest signal strength responding node (e.g., another sensor node 202 or a command node 216) that is not also operating in theft mode. Once the connection is in place, the stolen sensor node operating in theft mode uploads stored sensor data to the responding node. The stored sensor data 224 can be tagged as coming from a stolen sensor node, and stored by the responding node to its data storage module. As the stolen sensor node travels past other sensor nodes, the stolen sensor node opportunistically repeats this connecting process by connecting to the highest signal strength node and uploading stored sensor data.

[0020] Sensor network support infrastructure can aid in the physical recovery of stolen nodes by providing locating services. While the sensor node is in communication range of other sensor nodes or sensor network support infrastructure, various techniques such as signal timing/triangu!ation can be used. Furthermore, a sensor node can include GPS sensors to determine absolute position independently of or in conjunction with the sensor network support infrastructure. Thus, the sensor node can rely on support infrastructure and node equipment without a need for additional dedicated theft deterrent locating devices to be installed on the sensor node.

[0021] Command node 218 includes processor module 218, transceiver module 220, and central storage module 222. Processor module 218 can determine that the quality control information 228, received by transceiver module 220 from the sensor node 202, indicates a deployment disturbance. Processor module 218 also can generate feedback 230 in response to the determination. Feedback 230 can include feedback regarding whether the sensor node 202 has been disturbed and/or stolen, and feedback regarding a value of sensor data 204 based on associated quality control info 228 or actual sensor data. Transceiver module 220 can transmit validation 232, to validate whether sensor node 202 has been disturbed. For example, validation 232 can be negative, based on information that indicates sensor node 202 is being serviced such that sensor node 202 should not operate in theft mode in response to a disturbance. A validation threshold for determining a disturbance can be based on sensor node location. For example, sensor nodes located at a periphery of the sensor layout can be associated with an increased sensitivity for theft, due to the increased likelihood of interlopers wandering into the periphery of the survey area. Central storage module 222 stores data offloaded from the sensor node 202, e.g., stored sensor data 224 and other data such as node status information, quality control info 228, etc.

[0022] The command node 216 can prioritize which sensor nodes are to upload their data and in what priority, in the event of multiple sensor nodes being operated in theft mode at the same time. The communication used by the stolen sensor nodes, and/or other factors such as their location with respect to the network infrastructure, may only support one sensor node transmitting at a time. The command node 216 can prioritize network bandwidth 236 available to the sensor nodes. Priority can be based on information regarding the relative value 226 of the stored sensor data 224 in each sensor node 202, such that the command node 216 can allocate bandwidth to ensure that the sensor node 202 with the highest value of stored sensor data 224 is transmitted.

[0023] Sensor data 204 (e.g., raw/collected data sensed by sensor module 206) and stored sensor data 224 (e.g., sensor data 204 that has been processed/digitized and/or stored at data storage module 208) can be associated with a relative value. The relative value can be used for prioritizing uploading of the stored sensor data 224, and can be used for other purposes such as determining whether to store collected sensor data at the sensor node 202, or discard sensor data before or after it has been stored at the sensor node 202 or the command node 216. Sensor node 202 can transmit stored sensor data 224 when the sensor node is disturbed, by beginning with any sensor data marked as high value. Prioritizing the uploading of sensor data based on a relative value can be omitted in alternate examples, and can increase the likelihood that high- value data is successfully uploaded and stored outside the sensor node 202 when the sensor node 202 is stolen and unrecovered.

[0024] The relative value of sensor data can be determined by the sensor node 202, by the command node 216, or a combination. In an example, sensor node 202 transmits quality control information 228 to command node 216, and command node 216 provides feedback 230 to sensor node 202 that indicates whether the sensor data 204 associated with the quality control information 228 should be marked as high value. Value can be determined based on data trends, marking large amplitudes in the data as high value while ignoring random noise data. Sensor or QC data from adjacent sensor nodes can be compared to identify trends in the sensor data.

[0025] in an example, the sensor node 202 can process collected sensor data 204 using the processor module 210 to assign a relative value 226 to the sensor data 204. Alternatively, the node may be instructed that portions of the sensor data 204 and stored sensor data 224 are high or low value based on quality control information 228 or other data such as partial trace data that is uploaded to command node 218. Sensor data 204 collected during certain time periods (e.g., during times associated with test events) may also be designated as high value based on when source signals (vibroseis sweeps or dynamite shots) were made, independent of whether the sensor data itself was judged to be non-ordinary. Feedback 230 can be periodically sent to the sensor node 202 to prepare the sensor node 202 for a theft contingency. The sensor node 202 can store the relative value 228, and the feedback 230, as well as the raw sensor data 204, while keeping track of memory locations of high value stored sensor data 224. High value, low value, and gradations between these extremes can be used at various granularities to characterize the value of the sensor data 204, as appropriate to the type of data.

[0026] The relative value of sensor data 204 can be determined based on the raw sensor data, based on environmental conditions associated with sensor data collection such as the time of day, weather, or climate data, or based on other factors such as geographical location of deployment of the sensor node 202. Conditions and/or factors can be measured by a sensor node, communicated by the network to/from the sensor node, or communicated by a command node to/from the sensor node. The relative value of data assigned to multiple sensors can be determined based on the valuation of sensor data from one sensor. For example, the relative value of a time slice of stored sensor data from multiple sensor nodes can be decided based on sensor data associated with another selected sensor node. A command node can receive sensor data or QC information from the selected sensor node that looks interesting or otherwise shows a distinction based on processing analysis, and the command node can provide feedback 230 to sensor node 202 and other sensor nodes. The feedback 230 can indicate that the associated time slice of sensor data from the sensor node 202 (and the other sensor nodes, e.g., sensor nodes within geographical proximity to sensor node 202) should be marked high value. The decision of which sensor nodes to send this high value feedback 230 can be based on sensor nodes that are deployed spatially similar to the other sensor node, or sensor nodes that are spatially similar to the survey stimulus source (e.g., vibroseis truck), or some other methods.

[0027] The relative value of sensor data 204 for sensor node 202 can be determined based on sensor data from multiple sensor nodes. A trend in quality control information 228 from multiple sensor nodes can be detected, and a relative value can be assigned to the sensor data of a sensor node at the center of the trend area.

[0028] FSG. 3 is a flowchart of a sensor node method 300 according to an example. In step 310, sensor data is stored at a sensor node emplaced to collect sensor data in a first mode. In step 320, it is determined that the sensor node has been disturbed from its emplacement. For example, the sensor node and/or a command node determines that an interloper lifts the sensor node and carries it away. In step 330, the sensor node is operated in a second mode in response to the determining, including uploading sensor data stored prior to operating the sensor node in the second mode. Thus, the valuable stored data within the stolen sensor node can be retrieved before contact with the stolen sensor node is lost. In an alternate example, a relative value can be assigned to the sensor data to prioritize uploading of the sensor data based on the relative value. The prioritized uploading can increase the likelihood that valuable data is retrieved before communication with the node is lost.

[0029] FSG. 4 is a flowchart of a command node method 400 according to an example. In step 410, the command node receives quality control information associated with a sensor node. In step 420, it is determined whether the quality control information indicates a disturbance of the sensor node from an emplacement. For example, the command node can determine that quality control information associated with a sensor node is consistent with acceleration associated with an interloper lifting the sensor node and carrying it away. In step 430, the command node generates mode transition feedback in response to the determination, and the mode transition feedback is transmitted to the sensor node in step 440. For example, a sensor node associated with the quality control information can be operated in theft mode based on receiving the transmitted theft mode feedback. In step 450, the command node receives sensor data (e.g., from the sensor node operating in theft mode) in response to the mode transition feedback transmitted in step 440. In step 480, the command node stores the received sensor data corresponding to operation of the sensor node prior to mode transition. The command node can be a sensor node that is not operating in theft mode.

[0030] FIG. 5 is a flowchart based on operation 500 of a sensor node system according to an example. Blocks, and portions of blocks, in FIG. 5 can be omitted in alternate examples (e.g., valuing data samples, reducing power consumption, validating theft mode, broadcasting location, uploading based on high value, causing recorded data to be unavailable, evaluating signal strength, checking for and establishing other connections, and sleeping). Operation 500 of the sensor node system includes normal mode 502 and theft mode 504. In block 510, a sensor node collects sensor data and generates quality control information. In block 512, the sensor node and/or a command node (including a grouping of sensor nodes acting together) can determine the informative value of a present sample of sensor data, or assign/modify a value of a previous sample. The value determination can be based on feedback from survey control (e.g., a command node or other sensor node) provided in block 514. In block 518, the sensor node and/or the command node determines if the sensor node is disturbed. The disturbance determination can be based on feedback from survey control provided in block 514. If the disturbance determination is negative, the sensor node can sleep until a next sample is ready per block 518. For example, the sensor node can enter a reduced-power state, reducing power to or powering down sensor, storage, processor, and/or transceiver modules while sleeping. If the disturbance determination is positive, the sensor node is operated in theft mode 504.

[0031] In block 520 of theft mode 504, the sensor node reduces power consumption. The sensor node enters a reduced power mode to preserve battery life. This mode can turn off functionality within the node, including functionality not associated with data collection and collected data storage, location detection, and/or communications. In step 522, the sensor node validates the determination of theft mode, based on feedback (e.g., validation) from sua'ey control at block 514. The sensor node uses the wireless network to notify survey control of an indication of theft, and waits for a response (e.g., feedback). The response may either be a positive response that the sensor node is being stolen or a negative response that the sensor node is being collected for standard servicing. If the validation at block 522 is negative, it is determined whether the node is still deployed in block 524. If not still deployed (e.g., the node is removed from deployment to be serviced), the node can power down in block 528 to facilitate servicing. If the node is still deployed, the node can sleep until next sample is ready in block 518.

[0032] If the theft mode is validated in block 522, or if a timeout expires without receiving feedback from survey control, the sensor node can broadcast its present location in block 528. The broadcast of the location can aid in physical recovery of the sensor node. The location information can be an absolute location based on GPS data, or relative position based on other wireless devices that the node defects.

[0033] In block 530, the sensor node uploads sensor data, starting with any high value sensor data that has been tagged. Sensor data is uploaded either directly to central storage if connected to an infrastructure-based network, or uploaded to other nearby nodes if in an ad-hoc or mesh network.

[0034] In block 532, the sensor node determines if there is more data remaining to be uploaded. The sensor node can determine if an acknowledgment has been received in response to data that has been uploaded, and check whether stored data, e.g., high value data, has been acknowledged as uploaded. If no data remains to be uploaded, the sensor node can cause the recorded data to be unavailable.

[0035] In block 534, if no more data is to be uploaded, the sensor node operating in theft mode can encrypt its data, erase it, purposely corrupt it, or otherwise cause the stored sensor data to become unavailable to an interloper, for the purpose of assuring that the interloper cannot use the recorded data. Thus, the dataset remains completely proprietary to the survey owner. This may also provide a disincentive to those who are motivated to steal the sensor node to obtain its data. In alternate examples, the collected sensor data can be encrypted before, during or after it is stored, such that the stored data is made unavailable throughout the process. In block 538, the sensor node periodically broadcasts its location, so that it may be located and recovered. Additionally, information can be collected and stored at the sensor node during the theft mode after determining that no more data is to be uploaded, which may provide travel information regarding the interloper who has taken the sensor node.

[0036] If more data remains to be uploaded in block 532, the theft mode 504 proceeds to block 538 and the sensor node evaluates the signal strength associated with communication by the sensor node. For example, a sensor node operating in theft mode 504 is likely being carried away by an interloper, such that the sensor node will see variations in signal strength associated with a connection to the sensor network, a command node, or another sensor node. Accordingly, the sensor node can evaluate the signal strength of multiple connections (e.g., in a locality and/or over time), and determine if the signal strength is acceptable. If acceptable, the sensor node proceeds to block 530 and continues uploading stored sensor data.

[0037] If the sensor node determines that the signal strength is poor at block 538, theft mode 504 proceeds to block 540 and the sensor node checks for other connections for uploading data (e.g., connection to an access point/command node, connection to another sensor node that is not operating in theft mode, and/or connection to the sensor network). If no other connection is found, the sensor node can sleep for a duration (preconfigured or dynamically determined based on circumstances experienced by the sensor node) at block 542, and wake to check for other connections at block 540. Thus, the sensor node can conserve power when out of signal range, while checking for a signal in case the stolen sensor node is carried within range of a communication signal, or if survey control has dispatched a recovery team to the node's last location. If another connection is found in block 540, the sensor node can establish a new connection in block 544 and proceed to broadcast its location at block 528 and upload data at block 530. [0038] Thus, stored sensor data can be collected from stolen nodes while those nodes are still in communication range. By tagging high value data segments, sensor data of high value can be extracted from the sensor node in a minimal amount of time. Furthermore, stolen nodes can be located using other nodes or existing network infrastructure, while the stolen node is still within communication range, without needing additional hardware cost for dedicated theft detection devices to be added to the sensor nodes.

[0039] Various aspects of the various examples can be implemented by firmware, hardware, machine readable instructions (including a non-transitory computer readable storage medium having instructions stored therein), or a combination thereof. For example, a processor module or sensor node can implement machine readable instructions to provide the features described herein. The breadth and scope of the present features should not be limited by any of the above-described examples, but should be defined only in accordance with the following claims and their equivalents.

Claims

WHAT IS CLAIMED SS: 1 . A method, comprising:

storing sensor data at a sensor node emplaced to collect the sensor data in a first mode;

determining that the sensor node has been disturbed from its emplacement; and

operating the sensor node in a second mode in response to the determining, wherein the second mode includes uploading sensor data stored prior to operating the sensor node in the second mode.

2. The method of claim 1 , further comprising prioritized uploading of sensor data.

3. The method of claim 2, further comprising periodically uploading quality control information associated with the sensor data, and assigning a relative value to the sensor data based on feedback received in response to the quality control information.

4. The method of claim 1 , further comprising:

requesting a validation of the determining; and

returning to the first mode if a negative validation response is received.

5. The method of claim 1 , further comprising:

evaluating a wireless signal strength associated with a communication connection; and

connecting to the sensor network based on the evaluating, wherein the connecting includes a command node or another sensor node that is not operating in the second mode.

6. A sensor node comprising:

a sensor module to collect sensor data in a first mode;

a data storage module to store the sensor data in the first mode; a processor module to determine that the sensor node has been disturbed from an emplacement, and to transition the sensor node to a second mode in response to the determination; and

a transceiver module to upload, in response to transition to the second mode, sensor data stored in the first mode.

7. The sensor node of claim 8, wherein the processor module is to prioritize the upload of the sensor data.

8. The sensor node of claim 8, wherein the processor module is to prioritize the upload of the sensor data based on an environmental condition.

9. The sensor node of claim 6, wherein the processor module is to cause the stored sensor data to be unavailable in response to acknowledgment of upload of the stored sensor data.

10. The sensor node of claim 6, wherein the data storage module is to store data from another sensor node that is operating in the second mode.

1 1 . A command node, comprising:

a transceiver module to receive quality control information associated with a sensor node;

a processor module to determine whether the quality control information indicates a disturbance of the sensor node from an emplacement, and to generate mode transition feedback in response to the determination, wherein the transceiver module is to transmit the mode transition feedback to the sensor node; and

a storage module to store sensor data received by the transceiver module from the sensor node in response to the mode transition feedback, wherein the stored sensor data corresponds to operation of the sensor node prior to mode transition.

12. The command node of claim 1 1 , wherein the processor module is fo generate value feedback to prioritize the sensor data.

13. The command node of claim 1 1 , wherein the transceiver module is to transmit, to a plurality of sensor nodes, value feedback associated with a priority of the sensor data associated with the sensor node.

14. The command node of claim 1 1 , wherein the mode transition feedback is based on whether the node is being serviced.

15. The command node of claim 1 1 , wherein the transceiver module is to prioritize network bandwidth allocated for sensor data to be received in response to the mode transition feedback.