Discuss today's wireless devices and wireless transmission media.
In the past, we have discussed these devices in separate categories, such as pagers, e-mail handhelds, personal digital assistants (PDAs), cellular telephones, and smart phones. Today, however, new devices, generally called smart phones, combine the functions of these devices. The capabilities of these new devices include cellular telephony, Bluetooth, Wi-Fi, a digital camera, global positioning system (GPS), an organizer, a scheduler, an address book, a calculator, access to e-mail and short message service, instant messaging, text messaging, an MP3 music player, a video player, Internet access with a full-function browser, and a QWERTY keyboard. Microwave transmission systems are widely used for high-volume, long-distance, point-to-point communication. Communicationsatellites are used in satellite transmission systems. The three types of satellite are geostationary earth orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO). Radio transmission uses radio-wave frequencies to send data directly between transmitters and receivers. Infrared light is red light not commonly visible to human eyes. The most common application of infrared light is in remote-control units for televisions and VCRs. Infrared transceivers are being used for short-distance connections between computers and peripheral equipment and LANs. Many portable PCs have infrared ports, which are handy when cable connections with peripheral equipment are not practical.