Research & Development

Smart Sensor Networks
The basic goals of a smart sensor network generally depend upon the application, but the following tasks are common to many networks.

1. Determine the value of some parameter at a given location: In an environmental network, one might one to know the temperature, atmospheric pressure, amount of sunlight, and the relative humidity at a number of locations. This example shows that a given sensor node may be connected to a number of different types of sensors, each with a different sampling rate and range of allowed values.
2. Detect the occurrence of events of interest and estimate parameters of the detected event(s): In the traffic sensor network, one would like to detect a vehicle moving through an intersection and estimate the speed and direction of the vehicle.
3. Classify a detected object: Is a vehicle in a traffic sensor network a car, a mini-van, a light truck, a bus, etc.
4. Track an object: In a military sensor network, track an enemy tank as it moves through the network.

In these four tasks, an important requirement of the sensor network is that the required data be disseminated to the proper end users. In some cases, there are fairly strict time requirements on this communication. For example, the detection of an intruder in a surveillance network should be immediately communicated to the police so that action can be taken.

Sensor network requirements include the following:

1. Large number of (mostly stationary) sensors: Networks of 10,000 or even 100,000 nodes are envisioned, so scalability is a major issue.
2. Low energy use: Since in many applications the sensor nodes will be placed in a remote area, service of a node may not be possible. In this case, the lifetime of a node may be determined by the battery life, thereby requiring the minimization of energy expenditure.
3. Network self-organization: Given the large number of nodes and their potential placement in hostile locations, it is essential that the network be able to self-organize; manual configuration is not feasible. Moreover, nodes may fail (either from lack of energy or from physical destruction), and new nodes may join the network. Therefore, the network must be able to periodically reconfigure itself so that it can continue to function.
4. Collaborative signal processing: To improve the detection performance, it is often quite useful to fuse data from multiple sensors. This data fusion requires the transmission of data and control messages so it may put constraints on the network architecture.
5. Querying ability: A user may want to query an individual node or a group of nodes for information collected in the region. Depending on the amount of data fusion performed, it may not be feasible to transmit a large amount of the data across the network. Instead, various local sink nodes will collect the data from a given area and create summary messages. A query will be directed to the sink node nearest to the desired location.

Sensor types and system architecture:

With the coming availability of low cost, short range radios along with advances in wireless networking, it is expected that smart sensor networks will become commonly deployed. In these networks, each node will be equipped with a variety of sensors, such as acoustic, seismic, infrared, still/motion video camera, etc. These nodes may be organized in clusters such that a locally occurring event can be detected by most of, if not all, the nodes in a cluster. Each node will have sufficient processing power to make a decision, and it will be able to broadcast this decision to the other nodes in the cluster. One node may act as the cluster master, and it may also contain a longer range radio using a protocol such as IEEE 802.11, Bluetooth, or use Bluetronix proprietary routing algorithms.

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