Sensor Networks Home Assignment(CS704D)

Prepared ByPoulami ChowdhuryCse,7th SemesterRoll No. 13000110055Techno IndiaNovember, 2013

Presentation Topic

Surveillance system application using WSN

WIRELESS SENSOR NETWORK(WSN)

A Wireless Sensor Network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations and to cooperatively pass their data through the network to a main location. 

The development of wireless sensor networks was motivated by military applications such as battlefield surveillance.Today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and so on.

MOTES

A very low cost low power computer.Monitors one or more sensors.A Radio Link to the outside world.Are the building blocks of Wireless Sensor Networks (WSN).Sensor nodes depend on batteries for energy, which get depleted at a fast rate .

WSN ArchitectureThe WSN is built of "nodes" – from a few to several hundreds or even thousands, where each node is connected to one (or sometimes several) sensors. Each such sensor network node has typically several parts: a radio  transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting.

WSN Applications WSN has various applications in the following fields:

WSN ApplicationsToday, WSNs are more and more used in the commercial and industrial areas for e.g. environmental monitoring, habitatmonitoring, healthcare, process monitoring andsurveillance. The monitoring capability is the central feature of a WSN and the services offered by a WSN can be classified into three major categories: monitoring, alerting, and information “On-Demand”.Sensing and processing activities or communication with other nodes consumes a lot of energy.In WSNs, the primary objective is to increase the network lifetime while keeping delays reasonably low.

Surveillance ApplicationsThe general objective of such an application is to alert the military command and control unit in advance to the occurrence of events of interest in hostile regions.APPLICATION REQUIREMENTS :

Longevity: The mission of a surveillance applicationtypically lasts from a few days to several months. Due to the confidential nature of the mission and the inaccessibilityof the hostile territory, it may not be possible to manually replenish the energy of the power constrainedsensor devices during the course of themission. Hence, the application requires energy-awareschemes that can extend the lifetime of the sensor devices,so that they remain available for the duration ofthe mission.

Surveillance ApplicationsAdjustable Sensitivity: The system should have an adjustable sensitivity to accommodate different kinds of environments and security requirements.

Stealthiness: It is crucial for military surveillance systems to have a very low possibility of being detected and intercepted. Miniaturization makes sensor devices hard to detect physically; however, RF signals can be easily intercepted if sensor devices actively communicate during the surveillance stage.

Effectiveness: The precision in the location estimate, and the latency in reporting an event are the metrics that determine the effectiveness of a surveillance system. Accuracy and latency are normally considered important metrics of tracking performance.

Surveillance Applications Assumptions

WSNs consist of a number of sensing nodes which are distributed in a wide area. The base station (sink), which collects data from other nodes, interacts with a user (someone interested in monitoring the activity). Sinks have more advanced features than sensing nodes in terms of data transmission and processing capabilities, memory size and energy reserves.There can be multiple sinks for a network so that there is no single point of failure. Energy dissipation is a major factor in WSNs during communication among the nodes. Energy should be saved, so that the batteries do not get drained quickly.

Surveillance Applications Assumptions

The transmission mode plays an important role in WSNs. Nodes can take a single-hop or multi-hop path depending upon the type of network topology chosen for transmitting data to other nodes in the network.

The sensor nodes can be mobile or static depending on the application.

In surveillance applications, sensor nodes are oftenplaced in unattended areas. Therefore, the networkshould be self-organizing and self-creating.

Energy Efficient Surveillance System : Concepts

1. An unmanned plane deploys motes from the air.

2. Motes are air-droppable, self-organize into an Ad Hoc network on reaching land.

3. Motes establish sentry service to conserve energy, remain active for a period of time as a sentry.

4. Some motes go to sleep to save energy.

5. When a tank enters into surveillance area, active motes wakes up other motes and relay the detection back to the base station.

MAC Protocols and Their Performance in Surveillance ApplicationsA properly designed MAC protocol allows the nodes to access the channel in a way to save energy and support QOS.

Sensor-MAC (SMAC)The SMAC protocol uses periodic listening and sleeping schemes to prolong the network lifetime. In SMAC, nodes use ‘sync’ packets to exchange their schedules.The neighbouring nodes build virtual clusters to reduce the communication delay. In a virtual cluster, nodes have the same schedule and the nodes which exist in more than one cluster carry multiple schedules. Due to the different schedules, the probability of wake-up of these nodes becomes higherthan for other nodes which results in energy wastage.

SMACSMAC uses a fixed duty cycle, but in surveillance applications the occurrence of events can vary. Due to the fixed duty cycle, a node will consume most of its energy in idle state when the traffic load fluctuates.If we change the duty cycle with respect to high trafficload and the network experiences low traffic load, thenode will waste its energy in idle listening .While on the other hand, if we adapt the duty cyclesto low traffic load and the traffic load then increases,the communication delay will increase too, which leadsto a decrease in QOS. The protocol is most suitablewhen the traffic load remains constant.

Timeout-MAC (TMAC)

TMAC protocol introduces the timeout value to finish the active period of a node .If a node does not hear anything within the period corresponding to the time-out value, it allows the node to go into sleep state.The TMAC protocol solves the early sleeping problem, introduced in SMAC, using two methods: “Future Request To Send” (FRTS) and “Taking Priority onFull Buffers”.The performance of TMAC in surveillance applications is better compared to SMACwhen there is fluctuation in traffic loads. In TMAC, the nodes send their queued packets at the beginning ofeach frame which increases the traffic load. At high traffic loads, the transmission suffers from delay andnetwork QOS decreases.

Traffic Aware Energy Efficient MAC (TEEM)

TEEM uses the same technique to save energy as used in SMAC but instead of a fixed duty cycle, it makes the duty cycle adaptive according to the traffic information. The SMAC protocol divides the listen period into three parts Sync, RTS and CTS.In TEEM, the listen period consists of Syncdata and Syncnodata. The first part of the listen period in TEEM contains data while the other part contains no data.Both parts are used for synchronization.it gives more sleeping time to nodes than SMAC and TMAC.It provides one hop forwarding per transmission cycle which increase the transmission delay in multi-hop networks and decrease the network’s QoS. TEEM MAC is a good choice in small networks because thereare fewer chances of retransmission.

TEEM : Working PrincipleEach node will listen in the first Syncdata part of its listen periodwhether someone has data to transfer or not. If there is no data in the Syncdata part then it will send its ownsync packet in the Syncnodata part. The TEEM protocol combines the Sync and RTS packets into onepacket called SyncRTS. Whenever a node wants tocommunicate with another node, it sends the SyncRTSpacket in its Syncdata part. The destination node receives the packet and starts the communication, while the other nodes synchronize themselves with a SyncRTS packet and go into sleep mode.

Distributed Energy Aware MAC (DEMAC)

The DEMAC protocol uses a TDMA (Time Division Multiple Access) scheme to access the medium. DEMAC treats the nodes with respect to their energy level and it gives more time slots to a node that has less energy than other nodes.The DEMAC protocol uses a threshold value for the energy level of a node. If a node’s energy level decreases below the threshold value, it allows the node to go into a selection phase.In the selection phase, neighbouring nodes exchange their energy levels. The lower the energy level, the more time slots are assigned to a node, which gives it more sleeping time than other nodes.

DEMAC : Contd.It gives better QoS than contention-based protocols. It provides collision-free communication because each node haspre-assigned time slots.DEMAC uses an election process which can increase the delay incommunication. The nodes which are near to the sink will get weaker than other nodes because they are more involved in processing or forwarding the data to the sink than others.In this situation, the election process will occur frequently, especially in a dense network with high traffic load, which decreases the QoS.

Power Aware Cluster TDMA (PACT)

PACT is a TDMA-based protocol used for large multi-hop WSNs.PACT uses adaptive duty cycles with respect to the traffic load. It uses passive clustering in which a small number of nodes participating in the data forwarding are called cluster heads and gateways.

These nodes are elected with respect to their energy level. Nodes which are members of more than one cluster can be elected as gateways. The gateway nodes allow communication between clusters while a cluster head interacts with member nodes and then transfer data to the sink.It provides collision-free communication.

It decreases the communication delay through passive clustering, which improves the QoS support. On the other hand, each node has to listen to mini slots or control packets from other nodes in order to get the control information. This may lead to some energy consumption.

Lightweight MAC ProtocolLightweight Medium Access Protocol (LMAC) is a TDMA-based protocol which tries to minimize the transceiver state switches (from low-power state toreceive or transmit state) and adapt the switching-stateto traffic fluctuation. It allows the nodes to sleep when there is no data to transfer. The LMAC protocol is based on Eyes Medium Access Protocol (EMAC).The EMAC protocol is a TDMA-based protocol in which each node has one slot to transmit the data in a frame. Similarly to EMAC, LMAC also allows thenodes one possible time slot in a frame.It gives one time slot to each node to control it.It provides collision-free communication by ensuring that no node can select the same time slots that are in use by its neighbours within a two-hop distance.Each node has to listen in the control section of each frame which may lead to waste of energy.

Comparisons of MAC Protocols

TinyOSTinyOS is

open-source operating system.wireless embedded sensor networks.component-based architecture.

Developed at UCB in collaboration with Intel ResearchCurrent Stable Version is 1.1.15Main Ideas –

Low complexityConserve power – sleep as frequently as possible

Written in nesC – next generation C compiler.TinyOS 2.0 (T2) released on 6/11

Energy Efficient Surveillance System (EESS): Concepts

1.Implemented on top of TinyOS.2. Time Synchronization component is responsible for synchronizing the mote clocks with that of the base station. 3. Localization component is responsible for ensuring that each mote is aware of its location. 4. Routing component establishes routes for motes to exchange information and to communicate with the base station. 5. Sentry service component is responsible for power management. -- selects a subset of motes as “sentries” to monitor events.

-- remaining motes stay in low-power state until event occurs .-- sentries awaken motes to occurrence of an event.

6. Group management component is responsible for collaborative detection and tracking.

-- dynamically organizes the motes into groups to enable collaborative tracking. 

EESS:Time-Driven System Design

StartStart

Time-Driven System Design1. Phase I: Basic Initialization-- Time synchronization: synchronization beacon broadcast by base station at the beginning of each initialization cycle; timer drift rectified by a new system cycle.-- Diffusion Tree Creation: setting up reverse route to the base station. -- Dynamic reconfiguration: synchronization message from base station contains control parameters.2. Phase II : Neighbor Discovery-- each mote sends “Hello” message to neighbor 3. Phase III : Sentry Selection -- internal node of the diffusion tree, non-sentry neighbors or not covered by a sentry.4. Phase IV : Status Report 5. Phase V : Power Management, Event Tracking & Reporting 

EESS: Proactive Power Management

1. Sentry mote sends out beacons periodically.

2. Non-sentry stays awake until it receives a beacon.

3. Upon receiving a beacon, non-sentry mote goes to

sleep for a specified amount of time.

4. Non-sentry mote wakes up when timer expires and

waits for the next sleep beacon.

5. Sleep – wake cycle for neighbors proceed in a lock-

step fashion.

EESS: Reactive Power Management

1. Sentry mote doesn’t send out sleep beacons.

2. Transition between sleep and awake is timer-driven.

3. Non-sentry motes remains asleep for “awake-

Duration” time.

4. Non-sentry mote sleeps for “sleep Duration” time.

5. Non-sentry mote remains awake for longer duration

if sentry mote sends an awake beacon.

Surveillance systemThe proposed idea is to useWSN in the surveillance of an organization or building.EXISTING TECHNIQUESa). Surveillance using Cameras.b). Surveillance using biometrics.PROPOSED SYSTEMThe system uses transponder embedded in the objects identity card. It simply recognizes the transponder signal and then sends it to the central database server which checks for the domain of the object and take a decision from the identity embedded on the ID card.The system has two basic portions.A) Sensors.B) Database Server

Surveillance systemA)Sensor portion has further two partsi.ReaderThe RFID reader portion has a motion detector which tells the reader about the presence of a person/object in the room it also tells the number of persons.The deployment of the readers can be varied with the nature of the deployment environment. For example if our interrogating area is highly risky then our deployment will be dense. It means density (d) is directly proportional to the risk (r). If we know that the interrogating area is the risky one, then we increase the density of the reader.But density is inversely proportional to the threats (t).This equation shows that if we increase the density of the reader then the number of threats will be decreased.

Surveillance system

ii.TransponderIt is a transmitter, which transmit the information stored in them. In the proposed case the information about the object will bestored in the transponder. It is a chip imbedded in the card of the object. The transponders used by the system are called as RFID.

Surveillance system

B) DATABASE SERVERAll the readers are connected with the central database server. This check for the domain of the object, if it finds some sort of threat then it follows the Standard Procedure as perorganization.The designing of database system is a very careful process. Because a small mistake in the database can allow the imposters to penetrate in the organization. Proposed System is a very low cost system. As reliability of proposed system is much better than the conventional ones.

Battlefield Surveillance using WSN

Sensor nodes are deployed randomly (e.g., via aerial deployment) and are expected to self-organize to form a multi-hop network. A sensor node is capable of sensing some physical phenomenon (e.g., detect tank vibrations or sniper gun noise ), processing the sensed data and communicating the observed measurements to fusion nodes, also called micro-servers. Detection and tracking of moving objects has been identified as a well-suited application.The target is estimated via triangulationThe major limitation of this work is that sensor readings are assumed to be not influenced by noise, which is quite unrealistic for real world deployments.

Battlefield Surveillance using WSN

Collaborative Signal Processing in Sensor Networks Under some simplifying assumptions, e.g., zero-mean Gaussian distributed noise model and linear sensor measurement model; it was shown that the performance of particle filter using 4-bit adaptive encoding was comparable to the particle filter using 16-bit fixed encoding. The goal is to design and implement a hybrid sensor network based system for the detection, classification and tracking of moving targets.The system uses a large number of inexpensive tiny sensors to increase network coverage and a limited number of micro-servers, which performs the resource-intensive tasks. The system is implemented using off-the-shelf sensor and micro-server nodes.

Traffic Surveillance using WSN

Traffic surveillance systems provide the data used by Intelligent Transportation Systems (ITS). The disadvantages of inductive loop detectors have led to the search for a reliable and cost-effective alternative system.FlexibleEasy of installationRemote maintenanceLow costHighly accurate

ConclusionSensor networks are perhaps one of the fastest growing areas in the broad wireless ad hoc networking field.The research in sensor networks is flourishing at a rapid pace and still there are many challenges to be addressed such as:

1.Energy Conservation - Nodes are battery powered with limited resources while still having to perform basic functions such as sensing, transmission and routing.2.Sensing - Many new sensor transducers are being developed to convert physical quantity to equivalent electrical signal and many new development is anticipated.3.Communication - Sensor networks are very bandwidth-limited and how to optimize the use of the scarce resources and how can sensor nodes minimize the amount of communication. 4.Computation - Here, there are many open issues in what regards signal processing algorithms and network protocols.