Before you start
Objectives: Learn what is infrared wireless connection and its specifics, and what is Bluetooth and its specifics.
Prerequisites: no prerequisites.
Key terms: Bluetoots, devices, Infrared, mode, light, signal, uses, distance, IrDA, network, PAN, wireless
Infrared technology uses light waves that are just passed the visible light spectrum. The light used comes from three regions. One region is the near infrared which is the light wave closest to the color red. Also, there is intermediate infrared, and there is also far infrared. Infrared technology uses pulses of light to send signals trough the air. It can operate in two different modes. One mode is “Line of Sight”. In this mode, devices which communicate must be lined up together, so that they are pointing to each other. If the devices are not lined up correctly, then the signal won’t hit the receiver on the other end. Line of Sight mode has a limitation of about 1 meter in distance between devices. Also, if anything is between two devices, the light won’t be able to reach the receiver. The second mode in which infrared can run is the Diffuse mode, also called scatter mode. In this mode, instead of sending a narrow beam of light, the light is more like a wave that’s fairly broad. In this mode, we can have devices that are not lined up together, and they’ll still be able to communicate. However, again if there are obstacles in the way, the signal may not be able to get to the receiving end. Also, with diffuse mode the distance between devices can be little greater, but they still have to be in the same room and without anything between them. Infrared is typically used with small devices such as remote control units, PDAs and some older mobile phones. Infrared data transfer rate can go up to 4Mbps. Also, infrared networks are insecure since the signal can be easily intercepted (it is not encrypted).
Bluetooth is the standard of the IEEE 802.15 committee. It uses radio waves on the 2.45 GHz range. Bluetooth is usually used for communication between devices in short ranges. Depending on the implementation the distance between devices can range from 1 to 100 meters. With Bluetooth data can be sent around obstacles and even trough them. There are several specifications of Bluetooth, and the latest one is Bluetooth 4.0 (at the time of writing this article). Bluetooth devices set up a Personal Area Network (PAN). PAN is similar to the ad-hoc wireless network, but the difference is that we have one device which acts as the master device and additional devices that are slave devices. PAN network can have up to 255 slave devices. Bluetooth is typically used for devices that are in close proximity. It is often used on PDAs, mobile phones, tablets, printers, keyboards, etc. Bluetooth uses a 128-bit encryption to protect the signal. When compared to IrDA, Bluetooth is more often implemented.