Wireless Sensor Network: A Promising Approach for Distributed Sensing Tasks

WIRELESS NETWORK Wireless Local Area Network – connection through APs to the wider Internet. Wireless Metropolitan Area Networks – Connects several wireless LANs Wireless Wide Area Network – Covers Large areas Wireless Personal Area Network – Interconnects devices in a short span

A WIRELESS SENSOR NETWORK (WSN) Sensor Node: A sensing subsystem for data acquisition from the physical surrounding environment A processing subsystem for local data processing and storage A wireless communication subsystem for data transmission

Sensor Node Architecture

CHARACTERISTICS of WSN Energy harvesting Ability to cope with node failures Mobility of nodes Communication failures Ease of use

APPLICATIONS OF WSN Security and Surveillance – military command, control, communications, computing, intelligence, surveillance, reconnaissance and targeting systems Environmental Monitoring – sensing volcanoes, oceans, glaciers, forests – Air pollution monitoring – Landslide detection Health Applications – monitor patient physiological data Smart buildings – Smart Home – Windows are also attached with vibratory sensors connected to police to against thief Agriculture Applications – Greenhouse monitoring Structural monitoring – bridges, flyovers, tunnels, buildings – No need to physical visits

ENABLING TECHNOLOGIES Operating systems – eCos (embedded configurable operating system) – uC/OS (Micro-Controller Operating Systems ) – LiteOS, Contiki, TinyOS Hardware standards Radio, Battery, Microcontroller, Analog circuit, and Sensor Interface

WSN Network Topologies Star Topology Mesh Topology

SECURITY REQUIREMENTS AND COUNTERMEASURES FOR WSN Authentication – Originality of a packet and ensure that data is unchanged (data authentication) Secrecy – Ensuring the privacy of sensed data Countermeasures – digital signature – shared secret key

Sensing task assignment via sensor selection for maximum target coverage in WSNs

Introduction of WSNs Sensor Nodes + – Small size, cheap – (Computation, Energy, communication) Long time Monitoring – Environment, event detection Assigning Tasks

Energy consumption model of sensing Signal sampling conversion of physical signals to electrical ones analog to digital conversion and spectrum analyzer operating on A/D outputs. affecting parameters: – the distance between a sensor and target with a quadratic relation (e s =Theta(r s 2 )) – the number of covered targets

Task assignment and sensor selection Sensing task as an optimization problem – attempt to find near optimal solutions – Nodes which are out of range will be turned off.

Assumptions and problem formulation Set of Sensor nodes “S” Set of Targets “Z” Active x s =1 and otherwise x s =0 Targ(s), NBR(s)

Assumptions and problem formulation Energy consumption of the sensing operation Energy consumption of node s related to the sampling rate and number of covered targets

Assumptions and problem formulation

Distributed algorithms for NUM-CS

Set x s = 0 Send sleep state and DHDPKT to neighbors Break 2. Upon receiving a DHDPKT from any neighbor node: Update the corresponding entry in the neighbor table containing the list of covered targets of neighbor nodes.

Extension for dynamic movements of targets A sensor node detects a target has moved out of its sensing range. A sensor node detects a target has entered into its sensing range.

Dynamic DHD-CS Initialization: Run DHD CS at least one time so that each node reaches a sensing range.

Results

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