Bluetooth Technology

As innovative ideas are introduced along with the technological boom, our communication methods are becoming more and more easier. We have seen devices communicating each other with the help of wires, cables, radio-signals, wireless and also infrared signals. Apart from these physical connections, there are also some protocols (a set of commands and responses) that should be obeyed by the devices so as to stream their data. These protocols include

• The amount of data that should be sent at a time.

• The meaning of the bits that are sent and received.

• Whether the data that was sent is the data that is received.

These complexities have been lightened up to generate a new method of connecting devices called Bluetooth. As the method is wireless and automatic and needs only less power for its working, it can be called as the simplest form of connecting two devices. The devices can also be connected from quite a long distance.

Infrared and Bluetooth – Comparison

Till recently we were using infrared radiations for the transfer of data. But as this technology can only be used to communicate between two devices at a time, it clearly is a disadvantage. But in Bluetooth, you can connect multiple devices at the same time and share data with them as well. Infrared uses light-waves at lower frequencies than the human eye can receive and interpret, they have to be used to pair the devices using the “line of sight technology”. The best example is the use of a remote control to change the channels in your television. You have to point the remote at the television and then only you can operate it. Bluetooth on the other hand uses radio-frequency signals and hence can be used to pair the devices by standing anywhere near the range of radio signal.

But these two disadvantages can also turn out to be more advantageous than Bluetooth. As Bluetooth can be used to pair multiple devices at a time there are possibilities of interference by other Bluetooth devices. But since infrared has a “one-to-one” technology the intended message sent by the transmitter will surely be received by and only by the receiver.

Bluetooth Standards

Just like any other device, bluetooth also requires a physical standard and a protocol standard. As the physical standard, it provides agreement with the radio-frequency standard. For the protocol standard agreement has been made on the time at which the bits are to be sent, and the amount of bits that are sent, and also whether the sent message is same as the one’s received.
Bluetooth can pair upto a maximum of 8 devices at a time within a radius of 10 meters. The signals propagated can penetrate through walls and so can be used in different rooms as well.

Bluetooth Networking

As mentioned earlier, Bluetooth works on radio-frequency signals. An international agreement has been made for the use of industrial, scientific and medical devices (ISM), to set aside a frequency band between 2.402 GHz and 2.480 GHz for Bluetooth. But the same frequency has been used by many other types of equipment. So, special ideas have been implemented so as to avoid interference between them.
For avoiding interference, low power signals are propagated from the device (10mW). This is the reason that the range of Bluetooth device is restricted to a maximum of 10 meters. This will avoid the interference between your PC and portable telephone. Even if 8 devices are used in a 10 meter radius, they do not interfere. The possibility for more than one device to transmit the same frequency at the same time will be neglected. The method is called “Spread Spectrum Frequency Hopping”, by which a device will use almost 79 individual randomly chosen frequencies which are destined for a particular range. The rate of change of these frequencies will be changing from one to another on a regular basis.
In bluetooth, the Spread Spectrum Frequency Hopping method has the frequencies changing almost 1600 times/second. This means that, a lot of devices can use a part of the frequency spectrum. Any of the two devices do not have the same frequency at a certain time. So, this method assures that there will not be any interference of the Bluetooth devices with any other devices. As time slicing occurs, it restricts the interference to a fraction of a second.

So far, we have discussed about the range of a Bluetooth network and the method of avoiding interference. Now, it is time to discuss the transmission and reception of data, determination of the transmitter and receiver and also transfer of signals. For this a method called Bluetooth Piconets is used.

Bluetooth Piconets

Piconets actually refer to the process called Personal Area Network (PAN), in which a network is created between all the devices which have Bluetooth facility with the range of transmission and reception. This method is started automatically by the devices and does not need a command from the user. Once a PAN is established the devices tend to change their frequencies so that they avoid other piconets in the same range and also communicate with the devices in the same network.

For Bluetooth devices using a network, consider a room filled with Bluetooth compatible devices like a PC, cordless telephone, a satellite equipped TV receiver, a head set and so on. Before forming a network the transmitter of a device (eg. cordless telephone) will have a particular address among a range of addresses it has established for a particular type of device. When the device is turned on the radio signals will be sent to all the devices searching for the same address as that of the receiver. When it finds that the receiver (headset) has the same address a small network is formed. All the other devices go through the same routines making networks with its pair. All the devices within each network talks with each other and thus a communication is established. The frequencies keep changing for each network so that they are kept separated. Even if interference occurs between two or more networks, it will not happen for more than a fraction of a second. This can be corrected by software’s designated for this method.

Bluetooth Security Problems

As this technology deals with wireless networks, there are more probabilities of hacking of your Bluetooth device such that the information transmitted or received by you may be intercepted. Since we are working with radio waves there are more chances of remote accessing and spying.
Here are some usual types of bluetooth hacking.

• The user may receive data within your range without his permission. The user may not know what the message is and may add the contact to his address book. This will allow him to send messages that will be automatically received by the device as the address has already been saved. This type of hacking is called Bluejacking.

• Another hacking includes remote access of a user’s phone including its features. This enables the hacker to easily place calls and send text messages without the user’s knowledge. This type of a security problem is called Bluebugging.

• Car Whisperer is one of the latest hacking methods in which hackers transmit and recieve audio from a bluetooth enabled car stereo.

Overcoming Bluetooth Hacking

The manufacturers of Bluetooth have introduced an option called “Trusted Devices” where the user exchanges data after asking permission. Permission is asked even if the user receives the data. It is the user’s responsibility to decide whether the data that he is receiving is from a known person. When he reaches a zone where there are a lot of Bluetooth devices, he can also turn is device to “non-discoverable” mode and thus avoid connecting with other Bluetooth enabled devices entirely.