Location Technology



Radio Frequency Identification

RFID is a generic technology concept that refers to the use of radio waves to identify objects (Auto-ID Center, 2002). All labels or RFID tags have a chip and an antenna. The chip is used to store information about objects as a unique serial number. The antenna enables the chip to communicate both data and receive electromagnetic energy to power the chip when the chip reader radiates. The RFID chip is part of a range of technologies for recognition and identification such as barcodes, biometrics, magnetic tapes, optical cards, smart cards, etc. RFID is considered a significant improvement on the standard bar code label, which should be read by scanners "line of sight." The barcode labels can be damaged, bent, or stained, while passive RFID tags do not suffer these limitations. Several passive RFID chips can be read simultaneously. They are the passive RFID cards (without batteries), the semi-passive RFID tags and the active tags powered by a battery. The active tags are used in some cases by RTLS systems or real-time tracking systems.


A Real-Time Location System (RTLS) is a system that uses radio frequency signals received from transmitters of active tags to locate them in real-time. RTLS is based on wireless devices such as active RFID tags that transmit a wireless signal that receivers forward to a location calculation engine (software). It uses different types of algorithms, such as the time delay of arrival (TDOA), received signal strength (RSS) and Fingerprint to determine the location of the object or the person to follow


IEEE 802.11 is a standard developed for wireless LAN / WLAN, under Part 15 of FCC rules. The "WiFi" precisely defines the 802.11 group a, b, g, n, and many others. This protocol is widely used in laptops, phones, televisions and a host of everyday consumer electronics. In this protocol, the 2.4 GHz and now 5.8 GHz ISM bands are increasingly used.

802.11b uses Carrier Sense Multiple Access''''with collision avoidance (CSMA / CA) as the access method to improve the reliability of data transmissions. The standard uses CCK modulation technique, which is a variation on CDMA. It supports point-to-multipoint configurations. The standard also includes WiFi Security WiFi Protected Access or WPA and WEP recently.

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mesh network

The mesh network technology is gradually maturing and cannot be ignored as a future family of wireless networking technologies. While the first large-scale deployments of mesh networks are still in their infancy, feasibility laboratory testing has demonstrated a sufficient benefit to motivate new experiments.

With this type of architecture, the traditional access points are connected by radio links. They are authenticated and permitted to phase links with other access points in a routing table. If one of them fails, the others will move traffic out of the failed points. Therefore, the network formed is very reliable. The architecture is also able to absorb the traffic peaks with a dynamic load balancing.

In a mesh network, it is possible to shorten the distance between nodes, greatly increasing the quality of the link. By reducing the distance by a factor of two, the resulting signal is at least four times more powerful at the receiver, more reliable connections without additional power output by individual nodes. In a mesh network, you can extend the reach, add redundancy and improve the overall reliability of the network by simply adding more nodes.

Transmission option

In some architecture, the use of two frequency bands prevents interference and increase throughput. Signal reception uses the 2.4 GHz band (802.11b). Signal transmission is performed using the 5 GHz band (802.11a), recently open to the public and can be used indoor or outdoor. Although it was developed for data relay, a mesh network can also be used for voice. However, the algorithms should be established to limit the number of hops between nodes to avoid receiving latency periods too high.


Traditionally, RF waves were defined for the radio frequencies from a few kHz to 300 GHz. Over time, the RF has become synonymous with wireless signals at high frequency, low frequency radio signals with wavelengths below the far infrared (~ 300GHz). Microwaves are radio frequency the highest in the HF band, resulting in frequencies above 1 GHz.

The microwaves pass easily through Earth's atmosphere. That is why they are used for broadcast transmissions. Bandwidth in the microwave spectrum is much greater than in the rest of the radio spectrum standard.

The Wireless LAN, Bluetooth and IEEE 802.11g, b and n, also use microwaves in the ISM bands. Metropolitan networks (MANs), WiMAX and IEEE 802.16 are designed to operate between 2 GHz and 11 GHz.

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Wireless sensor networks consist of clusters of devices using sensor technologies deployed in a specific area. They communicate data wirelessly to a central system. Sensor networks continuously monitor the physical, chemical processes or magnetic properties, using the existing communications infrastructure.

A software layer for processing and data management allows building industrial, government or military applications.

Wireless sensor networks based on emerging technologies such as wireless communication technologies, information technology, semiconductors, MEMS, microsystems technology and embedded micro-sensors.

Wireless sensor networks have the potential to revolutionize telecommunications in a way similar to what we call the Internet of things by offering a wide range of different applications some of which remain to be discovered. Sensor networks have a huge potential for applications in various fields, including:

  • Environment and health: ocean temperature, collecting information on patients' conditions
  • Management of critical industrial areas: monitoring of oil containers, checking the concentration of chemicals and gases
  • Warehouse management and supply chain monitoring and historical states of the goods with the conditions of critical conservation
  • Military applications: surveillance and recognition

A wireless sensor network consists of many tiny sensor nodes, each equipped with a radio transceiver, a microprocessor and a number of sensors. These nodes are capable of independently forming a network through which sensor readings can be propagated. Each node has an autonomous processing capacity, data can be processed as they pass through the network.

Given the limitations of the equipment and the physical environment and levels of high demands with which the nodes must operate, algorithms and protocols must be designed to provide strong and efficient energy consumption. The design of the physical layer and communication technologies and the information coding still represent significant challenges for this new technology.

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