WO2015009138A2

WO2015009138A2 - A system and method for managing sleeping mode of wireless nodes in a wireless sensor network

Info

Publication number: WO2015009138A2
Application number: PCT/MY2014/000128
Authority: WO
Inventors: Reza Khoshdelniat; Gopinath Rao Sinniah; Zeldi Suryady BIN KAMALURRADAT; Usman Sarwar
Original assignee: Mimos Berhad
Priority date: 2013-07-18
Filing date: 2014-05-28
Publication date: 2015-01-22
Also published as: MY176826A; WO2015009138A3

Abstract

The present invention relates to a system and method for managing the sleeping mode of wireless sensor nodes (110) in a wireless sensor network for managing sleeping schedule of the wireless sensor nodes (110) during an event or crisis. The wireless sensor network comprises of at least one gateway and a plurality of wireless sensor node (110), wherein each wireless sensor node (100) includes a critical stage management module (111) and sleeping schedule management module (112) for managing sleeping mode during an event or crisis.

Description

A SYSTEM AND METHOD FOR MANAGING SLEEPING MODE OF WIRELESS NODES IN A WIRELESS SENSOR NETWORK

FIELD OF INVENTION

The present invention relates to a system and method for managing sleeping mode of wireless nodes in wireless sensor networks during an event or crisis. More particularly, the system and method includes a self-profiling technique based on sensor reading to manage the sleeping mode. BACKGROUND OF THE INVENTION

Wireless sensor networks have limited power resources which are used to power the sensor devices. Due to the power resource limitations, several Media Access Control (MAC) protocols and sleeping schedules have been developed and used in wireless sensor networks to reduce the power consumption.

An example of such method is disclosed in WO Publication No. 2012/064178 A1 which relates to a method for use in managing at least two sensor nodes in a wireless sensor network comprising the step of scheduling the active and sleeping time for the sensor based on the type of traffic at said sensor nodes; characterized in that, the scheduling the active and sleeping time step further comprising the steps of determining the type of traffic threshold as low (LA) or high active (HA) determining the status of the nodes based on the traffic threshold, reducing the active time of at least one of the nodes from normal active to low active when traffic is low and increasing the active time of at least one of the nodes from normal active to high active when traffic is high. The node is maintained at normal active time if the traffic is determined as normal. However, the triggering of the node will not be sufficient as the node is required to adjust its sampling rate and active period with the event and also requires the other nodes in the network to adjust their sleeping schedule with the node monitoring the event so they can route the messages to the gateway or destination node.

In another example, US Publication No. 2011/0191695 A1 discloses a method for maintaining wireless network response time while saving wireless adapter power. The method is used to reduce the power consumption of a wireless communication hardware device; power conservation scheduling algorithms can be implemented. Reoccurring events including DTIM intervals and Listen intervals can be scheduled as awake times. Similarly expected response intervals can be scheduled as awake times based on information, such as round trip time, that can be passed together with data to be transmitted. The wireless communication hardware device can be placed into a 'doze' state unless it is transmitting data, or unless it is expecting a transmission during one of the scheduled awake times. However, the triggering of the node depends on the expected response time for transmission of the scheduled information, whereby the sensor node does not response automatically based on the critical event that occurs.

Therefore, there is a need to provide a system and method for managing the sleeping mode of the wireless sensor nodes during an event or crisis that address the above mentioned drawbacks. SUMMARY OF INVENTION

A system (100) for managing sleeping mode of wireless sensor nodes (110) in a wireless sensor network comprises of at least one gateway, and a plurality of wireless sensor nodes (110); wherein the system (100) is characterised in that each wireless sensor node (110) includes a critical stage management module ( 11) to define critical stages, a sampling rate and an active period timing; and a sleeping schedule management module (112) to determine the critical stage and changes the sleeping schedule based on the critical stage.

Preferably, a method for managing the sleeping mode of wireless sensor nodes (110) in a wireless sensor network includes the steps of comparing sensor reading of a wireless sensor node (110) with predefined critical stage thresholds; determining the critical stage if the sensor reading reaches any level of threshold; determining the active period based on the critical stage if the reading continuously repeated for a number of times; determining the respective sampling rate based on the critical stage; comparing a new sensor reading with the predefined critical stage thresholds for by the wireless sensor nodes (110); modifying the sleeping schedule based on the sensor reading; increasing active period and sampling rate when the wireless sensor node (110) detects and event and enters a critical stage; determining the routing wireless sensor node (110) in a routing path to the destination wireless sensor node (110) or gateway; sending a triggering message to the neighbouring wireless sensor nodes (110), wherein the message is used to enable the neighbouring wireless sensor node (110) to shift from sleep mode to active mode; changing the active period by the neighbouring wireless sensor nodes (110) based on the critical stage defined in the message; triggering the other wireless sensor nodes (110) in the network by the neighbouring wireless sensor node (110) to shift to active mode; and forwarding the triggering message to the other wireless sensor nodes (110) in the routing path to change the active period of the wireless sensor nodes (110) in the routing path based on the critical stage defined in the message. Preferably, sending a Critical Situation Cancel message from the wireless sensor node (110) to its neighbouring wireless sensor nodes (1 0) if the wireless sensor node (110) monitoring the event moves back to the normal sleeping schedule, wherein the Critical Situation Cancel message is the message that triggers the event to shift to normal sleeping schedule.

Preferably, forwarding the Critical Situation Cancel message from the neighbouring wireless sensor node (110) in the route that receives the Critical Situation Cancel message to the other wireless sensor nodes (110) in the routing path.

Preferably, triggering message includes the critical stage defined in the wireless sensor node (110) and the destination address of the data messages which can be the network gateway or other wireless sensor node (110) in the network. Preferably, replying an acknowledgement message to the wireless sensor node (110) initiating the critical situation by the neighbouring wireless sensor node (110) after receiving the triggering message.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates a wireless sensor network according to an embodiment of the present invention. FIG.2 illustrates a system (100) for managing sleeping mode of wireless sensor nodes (1 0) in a wireless sensor network according to an embodiment of the present invention. FIG. 3 illustrates critical stages and its corresponding active mode in time domain.

FIGS. 4-7 illustrate wireless sensor nodes (110) shifting from a critical stage to another critical stage. FIG. 8 illustrates a method for managing sleeping mode of wireless sensor nodes

(110) of a wireless sensor network according to an embodiment of the present invention.

DESCRIPTION OF THE PREFFERED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail. FIG. 1 shows a wireless sensor network comprises of a gateway and a plurality of wireless sensor nodes. The gateway is used to connect the wireless sensor network to another network. The plurality of wireless sensor nodes (110) is interconnected to each other for relaying sensor readings to the gateway or a destination wireless sensor node (110). Each wireless sensor node includes a system (100) for managing the sleeping mode during an event or crisis.

FIG. 2 shows the system (100) for managing sleeping mode of wireless sensor nodes (110) in a wireless sensor network according to an embodiment of the present invention. The system (100) includes a critical stage management module (111) and a sleeping schedule management module (112). The critical stage module

(111) is used to define critical stages and its corresponding sampling rate and active period timing. The critical stages are defined based on the application and the type of wireless sensor node (110) utilized in the system (100). The critical stages depend on the type of wireless sensor node (110) used and the environment that the wireless sensor node (110) is deployed as well as the application. For example, in an aluminium factory monitoring application where the temperature in certain parts of the factory is very high, the temperature sensor obtains a reading of 30°C which consider as a normal level and when the reading obtained is 100°C, the highest critical stage level is reached. In this example, the temperature sensor is the wireless sensor node (110).The other critical stages in between is defined based on the number of critical stages required for the application. For example, if 10 critical stage is required, then the critical stages (CS) for temperature sensor are Normal 30°C, 38°C, 46°C, 52°C, 60°C, 68°C, 70°C, 84°C, 92°C, and 100°C. In another example of application of home monitoring, the temperature sensor defined its normal stage when the sensor reading reaches 23°C and when the sensor reading reaches 50°C, critical stage level is defined. Sleeping schedule management module (112) is used to determine the critical stage and therefore changes the sleeping schedule of the wireless network based on the critical stage. FIG. 3 shows illustrates critical stages and its corresponding active mode in time domain. When the wireless sensor node (110) is in sleep mode and an event happens, the system (100) sends an interrupt to the wireless sensor node (110) wherein the interrupt is triggered when the critical stage has been reached. Later on, the wireless sensor node (110) shifts from sleep mode to active mode, and determines its critical stage. When the wireless sensor node (110) follows a normal sleeping schedule, a timer in the wireless sensor node (110) is responsible for monitoring the sleeping schedule. Each critical stage includes a threshold which indicates the critical stage whereby if a sensor reading reaches the threshold, it defines the critical stage for that wireless sensor node (110). Every critical stage is assigned with a respective sampling rate and active time period. Each critical stage has a higher sampling rate and a longer active period as compared to the critical stage below it. In other words, the active time and the sampling rate depends on the level of the critical stage, wherein the higher the level of the critical stage, the longer active period and the higher sampling rate of the wireless sensor node (110).

FIGS. 4-7 illustrate wireless sensor nodes (110) shifting from a critical stage to another critical stage. The wireless sensor nodes (110) shift when the sensor reading reaches a different time threshold whereby the time threshold indicates the level of the critical stage. The wireless sensor nodes (110) reconfigure its active period and sampling rate based on the new critical stage due to the changes of the critical stage. The wireless sensor node (110) detects an event whereby the sensor readings are reaching the threshold of critical stage 1 as shown in FIG. 4. Therefore the wireless sensor node (110) increases its active period and sampling rate to a first active period and first sampling rate. In FIG. 5 the sensor reading initially reached the critical stage 1 and therefore the wireless sensor node (110) enters the critical stage 1. At the next active period, the sensor reading does not reach the critical stage threshold, and thus the wireless sensor node (110) shifts back to the normal sleeping schedule. In FIG. 6, the sensor reading increases and the wireless sensor node (110) enters the critical stage 1 . At the next active period, the sensor reading increases and the wireless sensor node (110) enters the critical stage 2 wherein the wireless sensor node (110) increases its active period and sampling rate to a second active period and second sampling rate from the first active period and the first sampling rate. The sensor reading reaches the highest threshold as shown in FIG. 7. Thus, the wireless sensor node (110) enters the highest critical stage and continuously active with high sampling rate.

FIG. 8 shows a method for managing sleeping mode of the wireless sensor node (110) in a wireless sensor network (100) according to an embodiment of the present invention. In step 210, the wireless sensor node (110) compares the sensor reading with the predefined critical stage thresholds. If the sensor reading reaches any level of threshold as in decision 211 , the wireless sensor node (110) determines the critical stage based on the threshold reached as in step 222. Otherwise, the method returns to step 210. In decision 223, if the reading continuously repeated for a number of times at the next active period, the active period is determined based on the critical stage as in step 224. Otherwise, the method returns to step 210. In step 225, the sampling rate is determined based on the critical stage. In step 226, the wireless sensor node (110) compares a new sensor reading with the predefined critical stage thresholds. If the sensor reading does not reach a different level of threshold as in decision 227, the method returns to step 226. If the sensor reading reaches a different level of threshold as in decision 227, the method continues to decision 228 wherein if the new sensor reading is below the critical threshold, the wireless sensor node (110) follows the normal sleeping schedule as in step 229. When the wireless sensor node (110) monitoring the event moves back to the normal sleeping schedule, the wireless sensor node (110) sends a Critical Situation Cancel (CS_Cancel) message to its neighbour wireless sensor node (110) as in step 230. The CS_Cancel message is a message that triggers the event to shift to normal sleeping schedule. Next, the neighbouring wireless sensor node (110) in the route that receives the CS_Cancel message forwards the CS_Cancel message to the other wireless sensor nodes (110) in the route as in step 231.

However, if the new sensor reading is above the critical threshold, the method returns to step 222.

Meanwhile, after the sampling rate and active period of the critical stage have been determined as in step 224 and 225, the wireless sensor nodes (110) determine the routing path of the wireless sensor node (110) in the route to the destination wireless sensor node (110) or gateway as in step 232. Next, in step 233, a triggering message is sent to the neighbouring wireless sensor nodes (110) in the routing path. The triggering message enables the neighbouring wireless sensor node (110) to shift from sleep mode to active mode. Then, the wireless sensor node (110) monitoring the event sends a Critical Situation Request (CS_Req) message to its neighbouring wireless sensor node (110) as in step 234. The CS_Req message includes the critical stage defined in the node and the destination address of the data messages which can be the network gateway or other nodes in the network. When the neighbouring wireless sensor nodes (110) receive the CS_Req message, the neighbouring wireless sensor nodes (110) change its active period and sampling rate based on the critical stage defined in the message as in step 235. Later on, the neighbouring wireless sensor nodes (110) reply the wireless sensor node (110) initiating the critical situation with a Critical Situation Acknowledgement (CS_Ack) message as in step in step 236. The CS_Ack message indicates that the neighbouring wireless sensor nodes (110) acknowledge the critical situation request. The neighbouring wireless sensor node (110) triggers the other wireless sensor nodes (110) in the routing path to shift to active mode by forwarding a CS_Req message to the other wireless sensor nodes (110) in the routing path. Thus, the CS_Req message is forwarded to all of the wireless sensor nodes (110) in the routing path to the destination wireless sensor node (110) or the network gateway is reached as in step 237.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

A system (100) for managing sleeping mode of wireless sensor nodes (110) in a wireless sensor network comprises of:

a) at least one gateway, and

b) a plurality of wireless sensor nodes (110);

wherein the system (100) is characterised in that each wireless sensor node (110) includes:

i. a critical stage management module (111) to define critical stages, a sampling rate and an active period timing; and ii. a sleeping schedule management module (112) to determine the critical stage and changes the sleeping schedule based on the critical stage.

A method for managing the sleeping mode of wireless sensor nodes (110) in a wireless sensor network includes the steps of:

a) comparing sensor reading of a wireless sensor node (110) with predefined critical stage thresholds;

b) determining the critical stage if the sensor reading reaches any level of threshold;

c) determining the active period based on the critical stage if the reading continuously repeated for a number of times;

d) determining the respective sampling rate based on the critical stage; e) comparing a new sensor reading with the predefined critical stage thresholds for by the wireless sensor nodes (110);

f) modifying the sleeping schedule based on the sensor reading;

g) increasing active period and sampling rate when the wireless sensor node (110) detects an event and enters a critical stage;

h) determining the routing wireless sensor node (110) in a routing path to the destination wireless sensor node (110) or gateway;

i) sending a triggering message to the neighbouring wireless sensor nodes (110), wherein the message is used to enable the neighbouring wireless sensor node (110) to shift from sleep mode to active mode; j) changing the active period by the neighbouring wireless sensor nodes (110) based on the critical stage defined in the message; k) triggering the other wireless sensor nodes (110) in the network by the neighbouring wireless sensor node (110) to shift to active mode; and

I) forwarding the triggering message to the other wireless sensor nodes (110) in the routing path to change the active period of the wireless sensor nodes (110) in the routing path based on the critical stage defined in the message.

3. The method for managing the sleeping mode of wireless sensor nodes (110) in wireless sensor networks as claimed in claim 2, wherein sending a Critical Situation Cancel message from the wireless sensor node (110) to its neighbouring wireless sensor nodes (110) if the wireless sensor node (110) monitoring the event moves back to the normal sleeping schedule, wherein the Critical Situation Cancel message is the message that triggers the event to shift to normal sleeping schedule.

The method for managing the sleeping mode of wireless sensor nodes (110) in wireless sensor networks as claimed in claim 3 further includes forwarding the Critical Situation Cancel message from the neighbouring wireless sensor node (110) in the route that receives the Critical Situation Cancel message to the other wireless sensor nodes (110) in the routing path.

The method for managing the sleeping mode of wireless sensor nodes (110) in wireless sensor networks as claimed in claim 2, wherein triggering message includes the critical stage defined in the wireless sensor node (110) and the destination address of the data messages which can be the network gateway or other wireless sensor node (110) in the network.

The method for managing the sleeping mode of wireless sensor nodes (110) in wireless sensor networks as claimed in claim 2, wherein replying an acknowledgement message to the wireless sensor node (110) initiating the critical situation by the neighbouring wireless sensor node (110) after receiving the triggering message.