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Planning Wireless Sensor Network Systems

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The ability to track objects and people throughout a given area or building using Wireless Sensor Networks or WSN is highly desirable for gathering information that can be effectively used for operations management and local logistics. Such information can increase business system and process efficiency by an order of magnitude, revealing not only how processes actually flow, but also providing information on how they can be improved. Tracking objects and people can also be used to maintain process flow, ensuring that the best form is used by the organization. In addition, such technology could also serve as a more sophisticated form of the more familiar RFID or Radio Frequency Identification systems that can monitor the location of objects and people and provide more exact coordinates through techniques such as Angle of Arrival or Arrival or AoA, Approximate Point in Triangle or APIT, and Centroid (rather than simple proximity as is used in RFID systems today).

WSN Energy Costs

Using cutting edge technology however, is not without its risks. The additional higher energy cost must be analyzed prior to deploying such a system on a per node basis. Once the total energy cost per node has been determined, the number of nodes that can fit within the budget can be established. Then, based upon the number of nodes available, the network can be designed with node placement carefully selected and tested prior to final deployment. The risk with this method is that there may not be enough nodes to cover the building and stay within budget, in which case a partial WSN or Wireless Sensor Network can be installed with plans to complete the network when budgetary constraints allow for it. A second option would be to purchase and install all nodes now, then apply power to only a portion of the network with plans to power up the entire network when budgetary constraints allow. However, in either case, powering the WSN is expensive and must be considered before purchase and deployment.

Wireless Sensor Networks
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Investment Cost and Justification

Unlike simple RFID systems, each WSN node includes onboard processors, coprocessors, accelerometers, magnetometers, and/or other components that add to the total cost of the WSN hardware. Using such robust hardware, each node is able to process sensor information locally before sending the information to the central monitoring station. This design eliminates the common dependency of the central monitoring station as a single point of failure, enabling each node to process and house a limited amount of information in the event that the central monitoring station is not available. The trade off however, is the increased risk of higher investment cost for the system.

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Hardware Size Considerations

The large number of components required for local processing of gathered sensor information increases overall size of each network node substantially. This aspect must be carefully considered because not only will people need to wear a node for purposes of tracking and monitoring operational processes, objects will also need to have WSN nodes attached. If some objects that require monitoring and tracking are smaller than the WSN nodes, this could pose and issue, decreasing the usefulness and narrowing the application of a very expensive investment. The larger node size also leaves out the option for covert monitoring if there are plans to use the WSN system for security purposes in the future. In this case the company would have to rely upon the continuing miniaturization and trend toward nanotechnology that could enable a WSN future upgrade to nodes that are considerably smaller than current technology allows (which increases the total cost of investment).

WSN Security

WSN system security must also be addressed to ensure that this valuable system is not subject to vulnerabilities that allow outside penetration of the organization’s network through the WSN. For a newer technology such as a WSN we must consider both standard security practices (those that cover the most common, simple attacks), and the more complex attacks that focus on niche areas created by the installation and operation of a WSN. For the wireless network aspect of the WSN, protecting transmissions using industry standard WPA2 with AES and frequent key exchange to eliminate the vulnerabilities associated with static keys. The WSN radios must be configured such that transmissions and reception have just enough power to reach the neighboring nodes and not enough power to transmit outside the building. All log information stored on each node must be encrypted in storage, especially for nodes that are worn by employees. A policy must be implemented requiring that all nodes remain in the building at all times, which will decrease the risk of data loss due to stolen nodes. The central monitoring station must be hardened, with strict file permissions, and two-factor authentication using a biometric such as fingerprint or retina scan combined with a password that is secured through a centrally managed directory service such as Microsoft Active Directory. The central monitoring system must also be configured with a host-based firewall and IDS along with encryption configured for the database and file system used to handle and store WSN information.

Building Wireless Sensor Networks: with ZigBee, XBee, Arduino, and Processing
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Final Thoughts

The risk associated with cutting edge technology is almost always much higher than with established technologies however, there are usually, as in the case of WSN technologies, extensive benefits that substantially offset the costs. Though proper budgetary planning, system design, and security measures, the organization can reap substantial benefits (especially with regard to logistical improvements) from the moment a WSN is installed.

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