Oct 23, 2008

Differentiated Surveillance with Wireless Sensor Network

In computer science and telecommunications, wireless sensor networks are an active research area with numerous workshops and conferences arranged each year. And a bigger part of this
research is focused on how the energy consumption can be reduced further. Networks where nodes are heterogeneous and the coverage requirements are also different for nodes, we can exploit this feature to obtain a lower energy usage there. 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. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, health care applications, home automation, and traffic control.

Sensor Network:
A sensor is a device the produces a measurable response to a change in physical condition such as temperature or chemical condition such as concentration, like temperature sensor, humidity
sensor etc.

Specialty and Difference of Sensor Network:
Network topology is not fixed in sensor networks. Power is an expensive resource in these networks Nodes are connected by wireless links and a large number of sensors are deployed.
Addressing scheme for sensor nodes are also different from ad-hoc networks. Sensor network is used for data aggregation where data flow from multiple sources to a single destination. There
can generally be huge amount of redundancy in data traffic. The bigger problem is sensor nodes are prone to failure very often.

Energy Aware Routing:
Energy saving is crucial for sensornets. Network lifetime depends on energy management policy. Communication is the most expensive activity. To maintain an energy aware routing schedule, possible goals include:
• Lowest energy route
• Route via highest available energy
• Distribute energy burden evenly
• Lowest routing overhead.
To reduce energy consumption, Destination Initiated Routing is performed. A directional flooding is followed that determine various routes (based on location).The energy metrics are
collected along the way where every route has a probability of being chosen which is inversely proportional to its energy cost. The choice of path is made locally at every node for every packet.

Differentiated Surveillance:
Sensornets are used for surveillance in many areas. Environmental hazard exploration, Military tracking, Battle fields, Earthquake response, Biomedicine 2etc are some of them. Human presence is risky in these cases, so wireless sensor is used instead. Different areas or situation may need different degree of coverage, for example: Security sensitive area, areas susceptible to environmental hazards, in case of biomedicine, more risk prone areas etc. By differentiated surveillance, we indicate providing different degrees of sensing coverage for different nodes.