What is wifi ? How it's working?

Introduction to Wi-Fi Technology

Wi-Fi is a technology that has revolutionized the way we network computers and electronic devices together, making wired connections unnecessary. This said, Wi-Fi and its terminology can be confusing. Knowing the basics of how it works and what it all means will help you make effective use of Wi-Fi in your own computer setup.

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. WiFi 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.

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.

There are equipment vendors who market WiFi mesh configurations, but those implementations incorporate technologies that are not defined in the standards.

Channel Bandwidth

The WiFi standards define a fixed channel bandwidth of 25 MHz for 802.11b and 20 MHz for either 802.11a or g networks.

The Technology Behind Wi-Fi

Wi-Fi uses a radio technology known as 802.11, which can transmit data over short distances using high frequencies. 802.11 operates on either 2.4GHz or 5GHz depending on its type. The network’s central point is the access point, which is a router with transmitting antennas which route the transfer of data.

Typically, the range of this Wi-Fi access point to any Wi-Fi capable devices is about 300 feet outdoors and 150 feet indoors. This estimated range does not take into account any obstructions which may block the signal, including walls, solid objects or trees. The more obstructions in the signal’s path from the base station, the shorter the range will be.

Modes of Wi-Fi Network Operation

Wi-Fi Hardware:-

Wireless broadband routers commonly used in home networks serve (along with their other functions) as Wi-Fi access points. Similarly, public Wi-Fi hotspots utilize one or more access points installed inside the coverage area.

Small Wi-Fi radios and antennas are embedded inside smartphones, laptops, printers, and many consumer gadgets enabling them to function as network clients. Access points are configured with network names that clients can discover when scanning the area for available networks. 

Wi-Fi Hotspots:-

Hotspots are a kind of infrastructure mode network designed for public or metered access to the Internet. Many hotspot access points utilize special software packages for managing user subscriptions and limiting Internet access accordingly.

Wi-Fi Network Protocols:-

Wi-Fi consists of a data link layer protocol that runs over any of several different physical later (PHY) links. The data layer supports a special Media Access Control (MAC) protocol that uses collision avoidance techniques (technically called Carrier Sense Multiple Access with Collision Avoidance or CSMA/CA to help handle many clients on the network communicating at once.

Wi-Fi supports the concept of channels similar to those of televisions. Each Wi-Fi channel utilizes a specific frequency range within the larger signal bands (2.4 GHz or 5 GHz). This allows local networks in close physical proximity to communicate without interfering with each other. Wi-Fi protocols additionally test the quality of the signal between two devices and adjust the connection’s data rate down if needed to increase reliability. The necessary protocol logic is embedded in specialized device firmware pre-installed by the manufacturer.

Common Issues With Wi-Fi Networks

Security - Network traffic sent across Wi-Fi networks passes through open air making it prone to snooping from malicious strangers. Several kinds of security technology have been added to Wi-Fi over the years to help address this problem, although some work better than others.

Health concerns - Some people claim that extensive exposure to wireless radio signals like those from Wi-Fi networks cause headaches, nausea and other physical issues. Many industry experts assure the public that Wi-Fi is safe, but controversy persists as claims one way or the other are difficult to prove.

Signal range - A basic Wi-Fi network with one wireless access point reaches at most only a few hundred feet (100m or less) in any direction. Expanding the range of a Wi-Fi network requires installing additional access points configured to communicate with each other, which becomes expensive and difficult to support, especially outdoors. As with other wireless protocols, signal interference (from other wireless devices, or from physical obstructions such as walls) can lower the effective range of Wi-Fi and its overall reliability.

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.