Wireless Fidelity Research Paper

Wireless Fidelity

In the last few years the world has undergone a tremendous and unprecedented technological change with the attack of the Information Technology revolution. Earlier it was e-mail that changed the way people communicate, and then online shopping became the order of the day, gradually online banking caught up and the list goes on and on. The new trend, Wi-Fi, or Wireless Fidelity, allows you to connect to the Internet from your couch at home, a bed in a hotel room or at school, all without wires. As author Harold Davis nicely puts, "Wi-Fi is a wireless technology just like a mobile phone and Wi-Fi enabled computers send and receive data indoors and out; anywhere within the range of a base station. Wi-Fi certification means that you will be able to connect anywhere there are other Wi-Fi CERTIFIED products -- whether you are at home, the office, school and other public areas equipped with a Wi-Fi Access Point device" (35). Customers with the capability to tap into wireless Internet networks at certain universities and Starbucks coffee shops in US will soon be able to browse the Web in a very inexpensive way using the wireless internet technology

Wi-Fi WLAN use radio technologies called IEEE 802.11b or 802.11a to provide secure, reliable, fast wireless connectivity. Michael Galagher notes that, "A Wi-Fi WLAN can be used to connect computers to each other, to the Internet, and to wired networks (which use IEEE 802.3 or Ethernet)" (120). Wi-Fi WLANs operate in the unlicensed 2.4 and 5 GHz radio bands, with an 11 Mbps (802.11b) or 54 Mbps (802.11a) data rate or with products that contain both bands (dual band), so they can provide real-world performance similar to the basic 10BaseT wired Ethernet networks used in many networked environments.

Competition has already driven down the costs of deploying 802.11b networks which can now be deployed by businesses to give their employees mobility within the business. Home users can buy 802.11b kit to extend their DSL or cable broadband Internet access wirelessly to the entire house. James LaRocca points out that, "In universities and schools a wireless network can allow computers to be integrated more effectively into teaching as classes no longer need to be held in computer lab" (48).

In September of 1999, the Institute of Electrical and Electronic Engineers (IEEE) ratified the specification for IEEE 802.11b, also known as Wi-Fi. IEEE 802.11b defines the physical layer and media access control (MAC) sublayer for communications across a shared, wireless local area network (WLAN). As Theodore Rappaport states, "At the physical layer, IEEE 802.11b operates at the radio frequency of 2.45 gigahertz (GHz) with a maximum bit rate of 11 Mbps. It uses the direct sequence spread spectrum (DSSS) transmission technique. At the MAC sublayer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol" (35). A wireless station with a frame to transmit first listens on the wireless medium to determine if another station is currently transmitting (this is the carrier sense portion of CSMA/CA). If the medium is being used, the wireless station calculates a random backoff delay. Only after the random backoff delay elapses can the wireless station again listen for a transmitting station. By instituting a random backoff delay, multiple stations that are waiting to transmit do not end up trying to transmit at the same time (this is the collision avoidance portion of CSMA/CA).

Collisions can occur and, unlike with Ethernet, they might not be detected by the transmitting nodes. Therefore, 802.11b uses a Request to Send (RTS)/Clear to Send (CTS) protocol with an Acknowledgment (ACK) signal to ensure that a frame is successfully transmitted and received.

The 802.11b frequency can be broken down into a few components. As confirmed by James in Geier in his book Wireless Networrking Handbook, "IEEE 802.11b wireless networking consists of the following components: Stations, Wireless acess points, and ports" (127). A station is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client. Wireless clients can communicate directly with each other or through a wireless access point. Wireless clients are mobile.

In his book Deploying Wireless LANS, Gilbert Helt informs that "A wireless access point is a wireless network node that acts as a bridge between station and a wired network. Wireless access points contain at least one interface that connects the wireless access point to an existing wired network (such as an Ethernet backbone) as well as a wireless network device with which it creates wireless connections with stations" (58). A wireless access point is similar to a cellular phone network's base station. Wireless clients communicate with both the wired network and other wireless clients through the wireless access point. However, Wireless access points are not mobile and act as peripheral bridge devices that extend a wired network.

A port is a channel of a device that can support a single point-to-point connection. For IEEE 802.11b, a port is an association, a logical entity over which a single wireless connection is made. A typical wireless client with a single wireless network adapter has one port and can support only one wireless connection. A typical wireless access point has multiple ports and can simultaneously support multiple wireless connections. The logical connection between a port on the wireless client and the port on a wireless access point is as Brian Cater says " a point-to-point bridged LAN segment--similar to an Ethernet-based network client that is connected to an Ethernet switch" (217).

Cyrus Peikari informs that "The IEEE 802.11 has defined two operating modes: Ad hoc mode and Infrastructure mode. In ad hoc mode, also known as peer-to-peer mode, wireless clients communicate directly with each other (without the use of a wireless access point)" (123). Two or more wireless clients who communicate using ad hoc mode form an Independent Basic Service Set (IBSS). Ad hoc mode is used to connect wireless clients when a wireless access point is not present. In infrastructure mode, there is at least one wireless access point and one wireless client. The wireless client uses the wireless access point to access the resources of a wired network.

When a wireless adapter is turned on, it begins to scan across the wireless frequencies for wireless access points and other wireless clients in ad hoc mode. Assuming that the wireless client is configured to operate in infrastructure mode, the wireless adapter chooses a wireless access point with which to connect.