· Infrared technology uses diffuse light reflected at walls, furniture etc. or a directed light if a line of sight (LOS) exists between sender and receiver.
· Infrared light is the part of the electromagnetic spectrum, and is an electromagnetic form of radiation. It comes from the heat and thermal radiation, and it is not visible to the naked eyes.
· In infrared transmission, senders can be simple light emitting diodes (LEDs) or laser diodes. Photodiodes act as receivers.
· Infrared is used in wireless technology devices or systems that convey data through infrared radiation. Infrared is electromagnetic energy at a wave length or wave lengths somewhat longer than those of red light.
· Infrared wireless is used for medium and short range communications and control. Infrared technology is used in instruction detectors; robot control system, medium range line of sight laser communication, cordless microphone, headsets, modems, and other peripheral devices.
· Infrared radiation is used in scientific, industrial, and medical application. Night vision devices using active near infrared illumination allow people and animals to be observed without the observer being detected.
· Infrared transmission technology refers to energy in the region of the electromagnetic radiation spectrum at wavelength longer than those of visible light but shorter than those of radio waves.
· Infrared technology allows computing devices to communicate via short range wireless signals. With infrared transmission, computers can transfer files and other digital data bidirectional.
· The main advantage of infrared technology is its simple and extremely cheap senders and receivers which are integrated into nearly all mobile devices available today.
· No licenses are required for infrared and shielding is very simple.
· PDAs, laptops, notebooks, mobile phones etc. have an infrared data association (IrDA) interface.
· Electrical devices cannot interfere with infrared transmission.
· Disadvantages of infrared transmission are its low bandwidth compared to other LAN technologies.
· Limited transfer rates to 115 Kbit/s and we know that even 4 Mbit/s is not a particular high data rate.
· Their main disadvantage is that infrared is quite easily shielded.
· Infrared transmission cannot penetrate walls or other obstacles.
· Typically, for good transmission quality and high data rates a LOS (Line of site), i.e. direct connection is needed.
· Almost all networks use radio waves for data transmission, e.g., GSM at 900, 1800, and 1900 MHz, DECT at 1880 MHz etc. Radio transmission technologies can be used to set up ad-hoc connections for work groups, to connect, e.g., a desktop with a printer without a wire, or to support mobility within a small area.
· The two main types of radio transmission are AM (Amplitude Modulation) and (FM) Frequency Modulation.
· FM minimizes noise and provides greater reliability. Both AM and FM process sounds in patterns that are always varying of electrical signals.
· In an AM transmission the carrier wave has a constant frequency, but the strength of the wave varies. The FM transmission is just the opposite; the wave has constant amplitude but a varying frequency.
· Usually the radio transmission is used in the transmission of sounds and pictures. Such as, voice, music and television.
· The images and sounds are converted into electrical signals by a microphone or video camera. The signals are amplified, and transmitted. If the carrier is amplified it can be applied to an antenna.
· The antenna converts the electrical signals into electromagnetic waves and sends them out or they can be received. The antenna consists commonly of a wire or set of wires.
· Advantages of radio transmission include the long-term experiences made with radio transmission for wide area networks (e.g. microwave links) and mobile cellular phones.
· Radio transmission can cover larger areas and can penetrate (thinner) walls, plants, furniture etc.
· Additional coverage is gained by reflection.
· Radio typically does not need a LOS (Line of Site) if the frequencies are not too high.
· Higher transmission rates (e.g. 54 Mbit/s) than infrared (directed laser links, which offer data rates well above 100 Mbit/s).
· Radio transmission can be interfered with other senders, or electrical devices can destroy data transmitted via radio.
· Bluetooth is simple than infrared.
· Radio is only permitted in certain frequency bands.
· Shielding is not so simple.
· Very limited ranges of license free bands are available worldwide and those that are available are not the same in all countries.
· A lot harmonization is going on due to market pressure.