Wireless Local Area Networks
A wireless local area network (LAN) is a flexible data communications system implemented as an extension to, or as an alternative for, a wired LAN. It uses radio frequency (RF) technology, to transmit and receive data over the air, minimizing the need for wired connections. A wireless LAN system can combine data connectivity with user mobility.
The data to be transmitted is modulated onto the radio waves, called carriers, and then are removed from the carriers at the other end by what is called a transceiver. End users in a wireless local area network access the network through adapters such as PC cards in laptop notebook computers. And PCI cards in desktop computers.
These cards provide the interface linking the network operating system (NOS) and the airwaves by means of an antenna. The wireless connection is clear to the network operating system as well as to those using the network, and it supports applications such as electronic mail (e-mail), access to shared peripherals, and access to multi-user databases and applications. Wireless LANs have gained popularity in areas such as the health-care, retail, manufacturing, warehousing and academia markets (Kurose, 2003).
Some widely known wireless technology in use in devices includes, cameras, automobiles, security systems, and kitchen appliances. Wireless LANs use electro magnetic airwaves (radio or infrared) to transmit information from one point to another without relying on any physical connection (Dean, 2000). Radio waves often are referred to as radio carriers because they simply perform the function to delivering energy to a remote receiver. Networking firms have a range of technologies to choose from when constructing wireless LANs. All technology comes with its own set of advantages and limitations. A narrowband radio system transmits and receives data on a specific radio frequency. Any unwanted crosstalk between communication channels is evaded by carefully designating different users on different channel frequencies. (Kurose, 2003)
The commonly used wireless systems used is the spread-spectrum technology, which is a wideband radio frequency technique developed by the military for use in reliable, secure communication systems. This technology is developed to substitute bandwidth effectiveness for security, reliability, and integrity (Dean, 2000). More bandwidth is consumed than in the case of narrowband transmission, but the end result produces a signal that is louder and easier to detect. If the receiver is not on the right frequency, a spread-spectrum signal looks like background noise. The two types of spread-spectrum radio are frequency hopping and direct sequence. (Behrouz, 2004)
Frequency-hopping spread-spectrum (FHSS) is a method that uses a narrow band carrier that changes frequencies in a distinct pattern. The signal hops to a variety of frequencies, with the exact sequence of...