Technology Made Simple - Bluetooth

Imagine attending a phone call without looking for the phone in your pocket or bag. Imagine your keyboard, mouse, monitor connected to the CPU without any wires. A decade back it was imagination. Bluetooth has changed this imagination to reality.

Bluetooth is the new technology that is significantly changing the way we interact with machines. Bluetooth is a short-range radio technology aimed at simplifying communication among network devices and between devices and the network. Bluetooth uses short-range radiolinks to replace cables between computers (or any other Bluetooth Device) and their connected units. Many companies had been trying to utilize this technology on a commercial scale but it was Erricsson Mobile Communication that started the project named Bluetooth in 1994. Today virtually any digital device can be part of the Bluetooth system. The dynamic connectivity-nature of Bluetooth makes it possible for this system to replace USB, and it is an improvement on Plug-and-Play-systems.

How it works
Each Bluetooth device has a small radio microchip that operates in a globally available frequency band (2.402 GHz to 2.480 GHz). Each radio chip has a Software controlled identity code (address), which ensures that the devices remain connected to a particular device (its master). Bluetooth devices will have a master unit and one or more slave units. For example if you have a Bluetooth enabled PC with the mouse, monitor, keyboard and all other plug-in devices Bluetooth enabled, the CPU will act as the master and the other devices as the slaves. All communication among the devices is through the Master unit. There is no direct communication among slave units. If slaves wish to communicate with each other directly they can establish a new connection with one of the devices acting as a Master.
When Bluetooth – enabled devices come in range of one another, a piconet is established. In other words an electronic conversation takes place between the devices to determine whether they have data to share or whether one needs to control the other. This is automatically done by the devices and the user dosen’t have to press a button or give a command. Once the conversation occurs the personal-area network (PAN) or piconet, is established. Range of the piconet may vary from 1 to 10 meters. Once the piconet is established, the members of the network randomly hop frequencies in unison so that they stay in touch with one another and avoid other piconets that may be operating in its vicinity.
Let us consider a real life example for better understanding. You have a state of the art living room with Bluetooth enabled devices. There is a music system with a DVD player, a satellite TV receiver and a Television; there is a cordless telephone; and a PC (personal computer). All these devices are Bluetooth enabled. Each of these systems forms their own piconet to communicate between the main unit and the peripherals. The cordless telephone has a transmitter in the base and another in the handset. The base and the handset are able to identify each other by their address (Software controlled identity code). When the base is turned on, it sends radio signals asking for response from any unit with an address in a particular range. Since the handset has an address in that particular range sought by the base, it responds, and a network between the base and the handset is formed with the base as the master and the handset the slave. The computer and music system go through similar exercise and establish network in the address range, which is pre-defined by the manufacturer. Once the network is established, the system begins to talk among themselves. Each piconet hops randomly through the available frequencies, so all the piconets are completely separated from one another. Thus the living room has three separate piconets, each made up of devices that know the address of the transmitters it should listen to and the address of the receiver it should talk to.
Technically speaking, in order to establish new piconets the procedure of inquiry and paging are used. The inquiry procedure enables a unit to discover which units are in range, and what their device addresses are. With the paging procedure, an actual connection is established. Only the Bluetooth device address is required to establish a network.
As in our example of the state of the art living room, the three piconets can communicate with each other using their Bluetooth address. For example you can send a message from the PC to the phone or from the phone to the music system and so on.

Scope and Advantage of Bluetooth
Bluetooth has certain advantages and disadvantages over other wireless technologies. Major advantage of Bluetooth is that it is designed as a short range, low power, and a low cost standared. Technologies like WiFi and HomeRF (i.e. 802.11) is not practically able to fit into products the size of a headset. Bluetooth operates using 2.5mW of power, compared to 100mW for WiFi.
Users of Bluetooth technology do not encounter any legal obstacles since Bluetooth operates in the unlicensed 2.4 GHz ISM band. This offers users the advantage of not having to obtain license from the local communication authority.Bluetooth is capable of transmitting and receiving data at a mere 720 kbps. This is quite low compared to 54 mbps of WiFi network. The limit on its transmitting and receiving rate makes it unsuitable for creating a wireless LAN.