Smart Sensor Network

Smart Sensor NetworksUniversidad de Sonora!Dr. Victor H. Benitez

Introductionsingle sensors vs sensor networks

They have limited applications and uses; for instance, if a system should measure several variables, e.g., temperature, pressure, and flow rate, at the same time in the application, single-sensor systems are insufficient. • They cannot tolerate a variety of failures which may take place unexpectedly. • A single sensor cannot guarantee timely delivery of accurate information all of the time because it is inevitably affected by noise and other uncertain disruptions. These limitations are critical when a system requires highly reliable and timely information.

Replicated sensor systems areapplicable not only because microfabrication technology enables production of various microsensors at low manufacturing cost, but also because micro sensors can be embedded in a system with replicated deployment. These redundantly deployed sensors enable a system to improve accuracy and tolerate sensor failure, i. e., distributed microsensor arrays and networks (DMSA/DMSN) are built from collections of spatially scattered microsensor nodes. Each node has the ability to measure the local physical variable within its accuracy limit, process the raw sensory data, and cooperate with its neighboring nodes.

IntroductionSmart Sensors

Sensors incorporated with dedicated signal-processing functions are called intelligent, or smart, sensors. The main roles of dedicated signal processing functions are to enhance design flexibility and realize new sensing functions.

To support the requirements of distributed sensor networks, sensors must possess greater functionality than simply gathering data and blindly transmitting the data to a centralized sensor node. Intelligent sensors are an extension of traditional sensors to those with advanced learning and adaptation capabilities. The system must also be re-configurable and perform the necessary data interpretation, fusion of data from multiple sensors and the validation of local and remotely collected data. Intelligent sensors therefore contain embedded processing functionality that provides the computational resources to perform complex sensing and actuating tasks along with high level applications.

The functions of an intelligent sensor system can be described in terms of compensation, information processing, communications and integration. The combination of these respective elements allow for the development of intelligent sensors that can operate in a multi-modal fashion as well conducting active autonomous sensing.

IntroductionArchitecture

IntroductionDesign Considerations

Fault tolerance: Over time, sensor nodes may fail or be blocked due to lack of power, physical damage or environmental interference. The failure of sensor nodes, however, should not affect the overall operation of the sensor network. Thus, fault tolerance or reliability is the ability to sustain sensor network functionality despite likely problems.

Accuracy improvement: Redundancy of information can reduce overall uncertainty and increase the accuracy with which events are perceived. Since nodes located close to each other are combining information about the same event, fused data improve the quality of the event information.


Accuracy improvement: Redundancy of information can reduce overall uncertainty and increase the accuracy with which events are perceived. Since nodes located close to each other are combining information about the same event, fused data improve the quality of the event information.

Timeliness: Sensor networks can provide the processing parallelism that may be needed to achieve an effective integration process, either at the actual speed that a single sensor could provide, or at even faster operation speed.

Network topology: A large number of nodes deployed throughout the sensory field should be maintained by carefully designed topology because any changes in sensor nodes and their deployments affects the overall performance.


Energy consumption: Since each wireless sensor node is working with a limited power source, the design of power-saving protocols and algorithms is a significant issue for providing longer lifetime of sensor network systems.Lower cost: Despite the use of redundancy, a distributed microsensor system obtains information at lower cost than the equivalent information expected from a single sensor because it does not require the additional cost of functions to obtain the same reliability and accuracy.

Scalability: The coverage area of a sensor network system depends on the transmission range of each node and the density of the deployed sensors. The density of the deployed nodes should be carefully designed to provide a topology appropriate for the specific application.

IntroductionSensor Network Architecture

Four different configurations of wireless sensor networks: (a) single hop with clustering, (b) multihop with clustering, (c) single hop without clustering, and (d) multihop without clustering. BS – base station

Diseño de una Smart Sensor Network

Consideraciones Técnicas

ZigbeeHardware Radio

XBee Series 1 hardware!These radios use a microchip made by Freescale to provide simple, standards-based!point-to-point communications, as well as a proprietary implementation of mesh!networking.

There are two basic varieties of XBee radio physical hardware

XBee Series 2 hardware!The Series 2 uses a microchip from Ember Networks that enables several different!flavors of standards-based ZigBee mesh networking. Mesh networking is the heart!of creating robust sensor networks, the systems that can generate immensely rich!data sets or support intricate human-scale interactions.


Both the Series 1 and Series 2 radios are available in two different transmission powers,!regular and PRO. The regular version is called simply an XBee. The XBee-PRO radio has !more power and is larger and more expensive.


Serie 1 vs Serie 2

ZigbeeHardware Antenna

Whip or wire antenna!This is just what it sounds like—a single piece of wire sticking up from the body!of the radio. It’s simple and offers omnidirectional radiation, meaning the maximum !transmission distance is pretty much the same in all directions when its wire is !straight and perpendicular to the module.! ! Chip antenna!The chip antenna is a flat ceramic chip that’s flush with the body of the XBee. That makes !it smaller and sturdier, but those advantages come at a price. Chip antennas have !a cardioid (heart-shaped) radiation pattern, meaning that the signal is attenuated in many !directions. It is used where mechanical stress to the wire antenna might!break it,

PCB antenna!Introduced with the XBee-PRO S2B, the PCB antenna is printed directly on the!circuit board of the XBee. It is composed of a series of conducting traces laid out!in a fractal pattern. The PCB antenna offers many of the same advantages (and!disadvantages) as the chip antenna with a much lower cost to manufacture.! U.FL connector!This is the smaller of the two types of external antenna connectors. More often!than not, an external antenna is not needed: it is an additional expense if a simple!wire antenna will do. However, when your radio is going to live on the inside of a!metal box then the antenna will need to live on the outside. That way the signal is!not attenuated by the enclosure.


PCB antenna!Introduced with the XBee-PRO S2B, the PCB antenna is printed directly on the!circuit board of the XBee. It is composed of a series of conducting traces laid out!in a fractal pattern. The PCB antenna offers many of the same advantages (and!disadvantages) as the chip antenna with a much lower cost to manufacture.!! U.FL connector!This is the smaller of the two types of external antenna connectors. More often!than not, an external antenna is not needed: it is an additional expense if a simple!wire antenna will do. However, when the radio is going to live on the inside of a!metal box then the antenna will need to live on the outside. That way the signal is!not attenuated by the enclosure.

RPSMA connector!The RPSMA connector is just a different type of socket from the U.FL connector.!It’s bigger and bulkier


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Smart Sensor Network