WiFi (Wireless Fidelity) - Wireless Local Area Networking

            WiFi is primarily a local area networking (LAN) technology designed to provide in-building broadband coverage. It is based on IEEE 802.11 specification. This tutorial gives you a basic understanding on WiFi.

           WiFi stands for Wireless Fidelity. It is based on the IEEE 802.11 family of standards and is primarily a local area networking (LAN) technology designed to provide in-building broadband coverage. Current WiFi systems support a peak physical layer data rate of 54 Mbps and typically provide indoor coverage over a distance of 100 feet.

           WiFi has become the de facto standard for last mile broadband connectivity in homes, offices, and public hotspot locations. Systems can typically provide a coverage range of only about 1,000 feet from the access point.

WiFi is Half Duplex

        All WiFi networks are contention-based TDD systems, where the access point and the mobile stations all vie for use of the same channel. Because of the shared media operation, all WiFi networks are half duplex.

Radio Signals

     Radio Signals are the keys, which make WiFi networking possible. These radio signals transmitted from WiFi antennas are picked up by WiFi receivers, such as computers and cell phones that are equipped with WiFi cards. Whenever, a computer receives any of the signals within the range of a WiFi network, which is usually 300 — 500 feet for antennas, the WiFi card reads the signals and thus creates an internet connection between the user and the network without the use of a cord.

WiFi Cards

         You can think of WiFi cards as being invisible cords that connect your computer to the antenna for a direct connection to the internet.

WiFi Hotspots

        A WiFi hotspot is created by installing an access point to an internet connection. The access point transmits a wireless signal over a short distance. It typically covers around 300 feet. When a WiFi enabled device such as a Pocket PC encounters a hotspot, the device can then connect to that network wirelessly.

       The 802.11 standard is defined in several specifications of WLANs. It defines an over-the-air interface between a wireless client and a base station or between two wireless clients.

There are several specifications in the 802.11 families −

·        802.11 − This pertains to wireless LANs and provides 1 - or 2-Mbps transmission in the 2.4-GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS).

·        802.11a − This is an extension to 802.11 that pertains to wireless LANs and goes as fast as 54 Mbps in the 5-GHz band. 802.11a employs the orthogonal frequency division multiplexing (OFDM) encoding scheme as opposed to either FHSS or DSSS.

·      802.11b − The 802.11 high rate WiFi is an extension to 802.11 that pertains to wireless LANs and yields a connection as fast as 11 Mbps transmission (with a fallback to 5.5, 2, and 1 Mbps depending on strength of signal) in the 2.4-GHz band. The 802.11b specification uses only DSSS. Note that 802.11b was actually an amendment to the original 802.11 standards added in 1999 to permit wireless functionality to be analogous to hard-wired Ethernet connections.

·        802.11g − This pertains to wireless LANs and provides 20+ Mbps in the 2.4-GHz band.

Access Protocols

   IEEE 802.11 wireless LANs use a media access control protocol called Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). While the name is similar to Ethernet's Carrier Sense Multiple Access with Collision Detection (CSMA/CD), the operating concept is totally different.

Quality of Service (QoS)

        There are plans to incorporate quality of service (QoS) capabilities in WiFi technology with the adoption of the IEEE 802.11e standard. The 802.11e standard will include two operating modes, either of which can be used to improve service for voice −

• WiFi Multimedia Extensions (WME) − Mandatory
• WiFi Scheduled Multimedia (WSM) − Optional

Security

          Security has been one of the major deficiencies in WiFi, though better encryption systems are now becoming available. Encryption is optional in WiFi, and three different techniques have been defined. These techniques are given here −

Wired Equivalent Privacy (WEP)

          An RC4-based 40-or 104-bit encryption with a static key.

Wired Equivalent Privacy (WEP)

      This is a new standard from the WiFi Alliance that uses the 40 or 104-bit WEP key, but it changes the key on each packet. That changing key functionality is called the Temporal Key Integrity Protocol (TKIP).

Disadvantage

      There are a few issues that are assumed to be the cause of the sluggish adoption of WiFi technology −

·        Security Problems − Security concerns have held back WiFi adoption in the corporate world. Hackers and security consultants have demonstrated how easy it can be to crack the current security technology known as wired equivalent privacy (WEP) used in most WiFi connections. A hacker can break into a WiFi network using readily available materials and software.

·      Compatibility and Interoperability − One of the major problems with WiFi is its compatibility and interoperability. For example, 802.11a products are not compatible with 802.11b products. Due to different operating frequencies, 802.11a hotspots would not help an 802.11b client. Due to lack of standardization, harmonization, and certification, different vendors come out with products that do not work with each other.