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A8E_EE-Times-Eur_2-375x10-875_A8.qxd 4/1/13 2:0 NAVIGATION & GEOLOCATION Fig. 2: Overview of nanotron’s swarm API commands. Efficient geolocation using swarm radio By Gunter Fischer, Thomas Förste and Frank Schlichting In wir eless sens or networks the concept of a swarm is used to illustrate how individuals in a group interact. Individuals in a swarm need to know their position relative to each other. Nanotron has added location-awareness to wireless sensor networks so that the swarm members can measure the distance between each-others, and are able to make decisions using this information. Communication and location awareness together are enabling a whole new category of geolocation applications. Collision avoidance (CAS) - to mention just one of them – is introduced in this article to illustrate the benefits of an extended swarm approach. The swarm platform technology Low power swarm radios – autonomous 2.4 GHz Chirp Spread Spectrum wireless nodes – are the basic swarm building blocks – see figure 1. They are able to broadcast and exchange messages while monitoring distances to other individuals in the swarm which are the key capabilities that allow for coordinated swarm behavior. Each individual in a wireless swarm consists of a swarm radio that is controlled by a host through its application interface (API). There are several categories of API commands – see figure 2. The RangeTo <node ID> command for instance returns the distance to another node. The quality of location-awareness depends on two basic criteria: accuracy and latency. Accuracy is the difference between measured and true distance. Usually it could be characterized by a fixed off-set and the spread of results as shown in figure 3. Latency specifies the time Fig. 1: The swarm radio mini from nanotron. required to obtain a ranging result. It has a strong impact on the real-time character of the application. Short messages and quick responses help to minimize latency thus maximizing throughput. A typical swarm radio requires 1.8 milliseconds of air time for executing a SDS-TWR cycle, nanotron’s patented Symmetrical Double-Sided Two Way Ranging. To broadcast its ID it only requires 350 microseconds. The maximum obtainable range of the swarm radios determines how far apart individuals in the swarm are still able to interact. Maximum range is highly dependent on the application environment. Under ideal line-of-sight conditions range might exceed 500 meters; however, in reality it often will be much shorter due to obstacles, reflections, interference from other radio signals, antenna miss-alignment etc. Figure 4 shows a real world example with one swarm radio inside a car and the other carried by a person. Range could be extended by placing the antenna on the outside of a car or by having the antenna installed on a hard-hat instead of on a belt. Dr. Gunter Fischer is Field Application Engineering Manager responsible for application support for nanotron’s swarm business. He can be reached at g.fischer@nanotron.com. Dr. Thomas Förste is Vice President of Sales and Marketing at nanotron Technologies. His email address is t.foerste@nanotron.com. Dr. Frank Schlichting is Director of Product Management for the swarm product line at nanotron. He can be reached at f.schlichting@nanotron.com. Surface Mount (and Plug In) Transformers and Inductors See Pico’s full Catalog immediately www.pic oel ect r onic s. com Low Profile from .18"ht. Audio Transformers Impedance Levels 10 ohms to 250k ohms, Power Levels to 3 Watts, Frequency Response ±3db 20Hz to 250Hz. All units manufactured and tested to MIL-PRF-27. QPL Units available. Power & EMI Inductors Ideal for Noise, Spike and Power Filtering Applications in Power Supplies, DC-DC Converters and Switching Regulators Pulse Transformers 10 Nanoseconds to 100 Microseconds. ET Rating to 150 Volt Microsecond, Manufactured and tested to MIL-PRF-21038. Multiplex Data Bus Pulse Transformers Plug-In units meet the requirements of QPL-MIL-PRF 21038/27. Surface units are electrical equivalents of QPL-MIL-PRF 21038/27. DC-DC Converter Transformers Input voltages of 5V, 12V, 24V And 48V. Standard Output Voltages to 300V (Special voltages can be supplied). Can be used as self saturating or linear switching applications. All units manufactured and tested to MIL-PRF-27. 400Hz/800Hz Power Transformers 0.4 Watts to 150 Watts. Secondary Voltages 5V to 300V. Units manufactured to MIL-PRF-27 Grade 5, Class S (Class V, 1550C available). Delivery-Stock to one week for sample quantities PICO Electronics, Inc. 143 Spar ks Ave. Pel ham, N. Y. 10803 E Mail: info@picoelectronics.com www.picoelectronics.com Pico Representatives Germany ELBV/Electronische Bauelemente Vertrieb E mail: info@elbv.de Phone: 0049 (0)89 4602852 Fax: 0049 (0)89 46205442 England Ginsbury Electronics Ltd. E-mail: rbennett@ginsbury.co.uk Phone: 0044 1634 298900 Fax: 0044 1634 290904 www.electronics-eetimes.com Electronic Engineering Times Europe July/August 2013 37


EETE JULAUG 2013
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