Ad hoc Network.
Ad Hoc network is a decentralized wireless network used for communication for a limited time period.
A piconet is a Ad hoc using Bluetooth technology. One device act as a Master and others act as slaves.
It is a device to device connectivity protocol used for short distance communication.
It employs the 2.4 GHz unlicensed ISM band, the same as 802.11b wireless.
Bluetooth employs a Frequency Hopping method. In this method the signal is switched from one channel to another in accordance with a pre-established pseudo-random pattern.
Master Slave Model.
Bluetooth establish a master slave model for communication. Master device connects 07 slave.Master allocates frequency channel to its slave.
Every Bluetooth device has unique 48 bit address which provides identification over piconet.
Creating a Bluetooth connection is a three step procedure.
- Inquiry: If both devices are unknown to each other,the first device will broadcast a message to discover new device.
- Paging: In this procedure they transfer their ID details 48 bit BD_ADDR.
- Connection: After completing paging process they enter into connection mode.
Bonding:When devices pair up, they share their addresses, names, and profiles, and usually store them in memory. The also share a common secret key, which allows them to bond whenever they’re together in the future.
The technology was developed by an Ericsson-led consortium, including Toshiba, IBM, Nokia and Intel. In early January 2000, the technology was further promoted by the Bluetooth Special Interest Group (SIG) comprised of 1371 member companies.They introduced different versions.
Three classes of Bluetooth devices
• Class 1 – 100 m ≤ 20 dBm power
• Class 2 – 10m ≤ 4 dBm power
• Class 3 – 10 cm @ 0 dBm power
Some modules are only able to operate in one power class, while others can operate in multiple.