It enables wireless communication in defined range that replaces the need of electronic devices. Bluetooth contains RF transceiver that lies at physical layer of OSI model. There are almost 79 bluetooth channels spaced at the rate of 1MHz. Physical layer use spread spectrum technique that makes it easy to transfer voice and data over short distance while creating wireless PANs.
The standard of bluetooth is based on the mode of master/slave operation. The term “piconet” refers to connection of network to one or more devices within its range. Almost ten pinconets can coexist within a range (range is 255 when in parked mode). Master device can establish connection to seven or more active slave devices. Devices in the range of piconet have 3 bits logical address for eight devices. These devices in parked mode are synchronized properly as they do not contain any physical address in the mode of piconet.
However, master device can only connect to a single device in a given moment, then it quickly switches to other active slave devices to establish connection with them simultaneously. Bluetooth enables only two piconets linked with one another in wide range network. This network is called “scattenet” that acts as a bridge between these two connected piconets.
Connection Establishment:
It is a complicated process to establish a network between two bluetooth devices. Before this, you need to ensure about some security measures that are as follow:
- Passive mode
- Inquiry about access points
- Access point service discovery
- Paging where you should synchronize with active access points
- Establishing a channel with access point
- Pairing using PIN (security)
- Network usage
In the normal state, a device works in the passive mode that listens about the network in which device attempts to connect with it. Whenever, you need to establish a connection with any active device, it begins with the phase of inquiry. In the inquiry phase, master device sends inquiry request to all devices within its access points. When any slave device receives request, it replies with its address.
Master device selects address and synchronizes with the device that uses technique known as paging. The process of paging involves synchronization of frequency and clock with access point. In the next phase, a link is created that allows master device to enter the phase of service discovery of access point using protocol named as service discovery protocol. After that, master device establishes a communication channel with access point with the use of L2CAP protocol.
Sometimes an additional channel called RFCOMM is established to provide the access of virtual port in case of extra services requirements. For example, different highway navigation programs work on the base of GPS bluetooth device that is satellite-based system. Satellite-based geo location system finds the geographical co-ordinates of a vehicle or mobile device. In addition, access point contains the system of pairing that is security mechanism. It gives access to authorize users only with the use of encryption key commonly called personal information number (PIN). Access point has feature of effective security mechanism that is known as pairing. It restricts the access of unauthorized users due to strong measures of protection. The process of paring is performed with the use of encryption key called PIN (Personal Information Number).
Bluetooth is the low cost, simple, and convenient way of enabling computer devices to communicate with each other. It is becoming the most widespread and functional device of present age.