What is Wi-Fi ?

WiFi stands for Wireless Fidelity. WiFiIt 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.

Wireless

iFi offers remarkably higher peak data rates than do 3G systems, primarily since it operates over a larger 20 MHz bandwidth, but WiFiWiFi systems are not designed to support high-speed mobility.

One significant advantage of WiFi over WiMAX and 3G is its wide availability of terminal devices. A vast majority of laptops shipped today have a built-in WiFi interface. WiFi interfaces are now also being built into a variety of devices, including personal data assistants (PDAs), cordless phones, cellular phones, cameras, and media players.

Wi-Fi – Working Concepts

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.

Radio Signals
Access points, consisting of antennas and routers, are the main source that transmit and receive radio waves. Antennas work stronger and have a longer radio transmission with a radius of 300-500 feet, which are used in public areas while the weaker yet effective router is more suitable for homes with a radio transmission of 100-150 feet.

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 Cards
WiFi cards can be external or internal. If a WiFi card is not installed in your computer, then you may purchase a USB antenna attachment and have it externally connect to your USB port, or have an antenna-equipped expansion card installed directly to the computer (as shown in the figure given above). For laptops, this card will be a PCMCIA card which you insert to the PCMCIA slot on the laptop.

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.

Most hotspots are located in places that are readily accessible to the public such as airports, coffee shops, hotels, book stores, and campus environments. 802.11b is the most common specification for hotspots worldwide. The 802.11g standard is backwards compatible with .11b but .11a uses a different frequency range and requires separate hardware such as an a, a/g, or a/b/g adapter. The largest public WiFi networks are provided by private internet service providers (ISPs); they charge a fee to the users who want to access the internet.

WiFi Hotspots

Hotspots are increasingly developing around the world. In fact, T-Mobile USA controls more than 4,100 hotspots located in public locations such as Starbucks, Borders, Kinko’s, and the airline clubs of Delta, United, and US Airways. Even select McDonald’s restaurants now feature WiFi hotspot access.

Any notebook computer with integrated wireless, a wireless adapter attached to the motherboard by the manufacturer, or a wireless adapter such as a PCMCIA card can access a wireless network. Furthermore, all Pocket PCs or Palm units with Compact Flash, SD I/O support, or built-in WiFi, can access hotspots.

Some Hotspots require WEP key to connect, which is considered as private and secure. As for open connections, anyone with a WiFi card can have access to that hotspot. So in order to have internet access under WEP, the user must input the WEP key code.

WiFi systems are the half duplex shared media configurations, where all stations transmit and receive on the same radio channel. The fundamental problem of a radio system is that a station cannot hear while it is sending, and hence it is impossible to detect a collision. Because of this, the developers of the 802.11 specifications came up with a collision avoidance mechanism called the Distributed Control Function (DCF).s o

Wi-Fi – 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.

WiFi Protected Access (WPA)
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).

IEEE 802.11i/WPA2
The IEEE is finalized the 802.11i standard, which is based on a far more robust encryption technique called the Advanced Encryption Standard. The WiFi Alliance designate products that comply with the 802.11i standard as WPA2.

However, implementing 802.11i requires a hardware upgrade.

Wi-Fi – Major Issues

There are a few issues that are assumed to be the cause behind 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.

Billing Issues − WiFi vendors are also looking for ways to solve the problem of back-end integration and billing, which have dogged the roll-out of commercial WiFi hotspots. Some of the ideas under consideration for WiFi billing such as per day, per hour, and unlimited monthly connection fees.