This technology allows the instant connections of voice and information between multiple devices in real time.
This technology allows the instant connections of voice and information between multiple devices in real time.

BlueTooth (2)


BlueTooth is a standard used in radio links of short-range, intended to replace the wired connections between electronic devices, such as cell phone,.
personal digital assistants (PDAs), computers and many other features.
BlueTooth technology can be used at home, at the office, in the car, etc..

This technology allows the instant connections of voice and information between multiple devices in real time.
The transmission mode used ensures protection against interference and security in sending information.

Main features :
• hardiness
• low complexity
• low consumption
• low price

The BlueTooth is a small chip that works in a globally available frequency band. Communication can make point to point or multipoint.
This technology allows the instant connections of voice and information between multiple devices in real time.








How does it work ?


All devices must be equipped with a chip (transceiver) which emits and receives the 2.4 GHz frequency that is available in the world (with a few variations of bandwidth in different countries).
In addition to information, there are three channels of voice.

Information can be exchanged until 1 second megabits (2 megabits a second in the second generation of this technology).
A scheme of \frequency hopping\ allows the devices to communicate inclusive in the regions where there are large electromagnetic interference.









The standard BlueTooth operates in the 2.4 GHz band
The standard BlueTooth operates in the 2.4 GHz band

Frequency bands


The BlueTooth standard works in the 2.4 GHz band. Although worldwide, this band is available, the width of the Strip may differ in some countries.
It is the frequency of the scientific and medical industries 2.45 GHz band (ISM *).
The beaches of bandwidth in Europe and the United States are between 2,400 to 2.483,5 MHz and they cover a part of the France and the Spain.
The beaches of bandwidth to the Japan are between 2,471 to 2,497 MHz.
If the system can be used anywhere in the world is parcaque radio transmitters cover 2,400 and 2,500 MHz and it is possible to select the appropriate frequency.
This ISM is open to all radio systems and must take into account interference from baby monitors, controls for the gates of garages, wireless phones and ovens microwave.

Industrielless, scientific and medical radio bands were originally reserved internationally for the use of electromagnetic fields for industrial, scientific and medical purposes.
In general, communications equipment must accept any interference generated by the ISM equipment.

Power
Transmission equipment are classified into 3 groups according to the level of emission power.
Equipment recipient must have a sensitivity of at least 70 dBm and the admissible error rate must be minor or equal to 0.1%.0





Device power mW (dBm) class range (approximate)
Class 1 100 mW (20 dBm) 100 meters
Class 2 2.5 mW (4 dBm) 10 meters
Class 3 1 mW (0 dBm) 1 meter




the BlueTooth chip consumes 1 to 100 mW
the BlueTooth chip consumes 1 to 100 mW

The chip


It will be incorporated into portable devices and battery powered, it's why she must have a very limited consumption (up to 97 times less than a mobile phone).
If devices BlueTooth don't exchange information, they establish a waiting to save energy. Transmission power which is used is 1 mW with a range of 10 m, 100 mW for a range up to 100 m.

Scope of application
The connections have a maximum range of 10 meters, but using amplifiers it is possible to reach up to 100 meters, but with a slight distortion.
It must be remembered that these devices have been created to be used in closed environments and short distance.








This figure shows the set of protocols BlueTooth
This figure shows the set of protocols BlueTooth

Protocols


Different applications can work with different sets of protocols.
The figure on the right shows all the protocols :

Interference
If we look at the interference with other devices, it is necessary to pay attention to those who work in the same band.
For example, similarly he forbade it to use mobile phones in aircraft, it is possible to prohibit the use of any other device that integrates a chip BlueToothbecause it can interfere with navigation elements.

But this can be a problem because it was designed to maintain a constant communication, even moving and inside briefcases, and it can work without the user is in misses








The structure is called a piconet and in a slightly more complex version, a Scatternet.
The structure is called a piconet and in a slightly more complex version, a Scatternet.

BlueTooth networking


The versatility of the design technology BlueTooth allows easy preparation and layout of networks between different devices with Bluetooth.
BlueTooth has been designed to work in a multiuser environment.
The standard sets out two types of configurations, which can extend to a considerable number of items to develop networks and networks below.
The structure that manages this technology consists, in the simplest form of a piconet and in a slightly more complex structure, a Scatternet.

Up to eight users or devices can form a \\Pico\\ and even ten piconets can coexist in the same coverage area.
Knowing that each link is codified and protected from parasites and the loss of the link, BlueTooth can be considered like a very safe short range wireless network.
The Pico network consists of several devices that are in the same radio coverage where they share the same channel and it is between two and eight of these units.
Each device is based on the standard IEEE 802.19 pour le WLAN, tandis que le Scatternet qui est formé par la connexion d'un pico-réseau avec un l'autre , possède un maximum d'interconnexions de dix Piconets.


The reason why the Scatternet was introduced is to solve the problem of the low bandwidth available to each user of a piconet if they find a large amount of connected units.
Performance, together and individually a Scatternet users is better than all users have when they are in the 1 MHz channel.






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