Guest Author - Cathy Spearmon
The presence of wireless services has no doubt illustrated the progression of technology and a new era of telecommunications. Though wireless technologies have been used for more than a century, in the form of radios, it birth actually took place in the 19th century when “the father of radio”, Guglielmo Marconi, introduced wireless technology to the world.
In 1894, Marconi experimented with radio waves (Hertzian Waves), in order to produce and detect radio waves over long distances. In 1896, Marconi achieved his objective and obtained a patent, establishing the Wireless Telegraph and Signal Company Limited, the first radio manufacturers in the world. By 1901, signals were being received across the Atlantic. And, by 1905, the first wireless distress signal was sent through the use of Morse Code. Wireless technology has proven itself to a most valuable and reliable form of communication.
Wireless networking, also called wireless LAN, was introduced in 1971 when networking met radio communications at the University of Hawaii. This bi-directional star topology consisted of seven computers spread out among the four islands to communicate with a computer located on the island of Oahu without the use of telephone lines. This marked the beginning of what we now know as the wireless network or wireless LAN.
Wireless networking, the ability for two or more computers to communicate with each other using standard network protocols without the use of network cabling, relies greatly on electromagnetic (infrared and radio) airwaves to receive and transmit data. It is usually implemented as an extension to an existing network or as an alternative to a wired LAN. Wireless networks have gained increased popularity in a number of markets, including health care, retail, manufacturing and warehousing, even classrooms and homes.
Wireless networks consist of several components, which include a wireless network interface card (PC card in a laptop and an ISA or PCI adapter in a desktop computer) and a transceiver, also known as an access point. A centrally located access point transmits and receives signals to and from the surrounding computers utilizing the interface cards. Data passes back and forth via the interface cards allowing computers within the wireless network to communicate directly with one another for file and printer sharing. However, they may not be able to access wired LAN resources without having one of the computers, equipped with special software, act as a bridge to the wired LAN.
Infrared, laser, narrowband microwave and spread-spectrum are common signal methods used in standard wireless networks.
By far the fastest wireless technology, but the least reliable because its signal can drop with the smallest obstruction or distraction is the infrared technology. This technology uses an infrared beam to carry signal and data to and from computers, printers, PDAs and other wireless devices. It has the ability to transmit data a high rate due to its large bandwidth. There are four types of infrared technology: line-of-site, reflective, scatter and broadband optical telepoint. Line-of-site networks work only when two devices are adjacent from each other. Any obstruction or excessive distance between the two devices can keep the signal from passing successfully. A reflective network works similar to a mirror. The signals sent to the transceivers are reflected and passed on to the receiving device. The scatter infrared network works only in areas no more than 100 feet with a slow signal transmission, bouncing off walls and ceiling eventually hitting the receiving device. Lastly, broadband optical teleport networks are indeed the fastest of the four infrared technologies. This type of network is capable of transmitting high quality multimedia, like voice, graphics and data, which makes it comparable to a wired network.
Laser is similar to infrared. However, it requires a direct line-of-sight. Any object getting in the way of its line-of-sight will break the laser and inhibits the transmission.
Laser is much more sensitive to outside interferences that infrared.
Narrowband microwave is similar the broadcasting of a radio station. The broadcast range is about 5000sq meters, but cannot go through load-bearing or steel walls. Licensed by the FCC, narrowband microwave uses the 18.82 to 19.205GHz of the radio spectrum.
Becoming the standard for wireless networks, spread-spectrum radio technology is the most reliable signal method available. Offering the best combination of performance and feature, there are two types of spread-spectrum technology: frequency hopping and direct sequence.
Frequency hopping divides frequencies into hops, hence the name, frequency hopping. The sequence of the hops does several things. First, the blocks of data are transmitted on different frequencies known to its intended receiver. When the receiver acquires the signal, it positions the block into the correct order. Because the frequencies hop at inconsistent times and frequencies, the built-in security prevents hacking.
By way of the direct sequence method, messages are coded by means of digitizing. It utilizes a multi-pattern to characterize each original bit within the message. Despite the fact that it does not efficiently utilize bandwidth, transmissions are fitting for bandwidth sharing as it presents an enhanced signal-to-noise ratio compared to that of narrowband transmissions.