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Geolocation implementation through swarm radio

Posted: 26 Jul 2013 ?? ?Print Version ?Bookmark and Share

Keywords:Collision avoidance? CAS? swarm platform? nanotron? wireless network?

Communication and location awareness together are paving the way for a whole new category of geolocation applications. Collision avoidance (CAS)to mention just one of them C will be introduced in this paper illustrating the benefits of the extended swarm approach.

The swarm platform technology
Low power swarm radios C autonomous 2.4GHz chirp spread spectrum wireless nodes C are the basic swarm building blocks (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 behaviour.

Figure 1: Low power swarm radios: swarm radio mini from nanotron.

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 (figure 2). The RangeTo command for instance returns the distance to another node.

Figure 2: Overview of nanotron's swarm API commands.

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 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 minimise latency thus maximising throughput. A typical swarm radio requires 1.8ms 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.

Figure 3: Ranging accuracy is characterized by offset and spread. The actual distances are 50, 100 and 150m respectively.

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 500m; however, in reality it often will be much shorter due to obstacles, reflections, interference from other radio signals, antenna miss-alignment etc.

Figure 4: Range measured between a pedestrian with a swarm radio mini and another swarm radio mounted onto the dashboard of a passenger car.

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 on a belt.

Collision avoidance solution
There is a need for automatic collision avoidance in mining. In order to prevent accidents a reliable alarm is required whenever vehicles come too close to people, assets or other vehicles. The swarm geolocation technology is well-suited for implementing such collision avoidance solutions (CAS).

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