What is Wi-Fi?
Wi-Fi is the name of a popular wireless
networking technology that uses radio waves to provide wireless high-speed Internet
and network connections.
Wireless networks operate using radio
frequency (RF) technology, a frequency within the electromagnetic spectrum associated
with radio wave propagation. When an RF current is supplied to an antenna, an
electromagnetic field is created that then is able to propagate through space.
The cornerstone of a wireless network is a
device known as an access point (AP). The primary job of an access point is to
broadcast a wireless signal that computers can detect and "tune"
into.
The radios used for Wi-Fi communication are
very similar to the radios used for walkie-talkies, cell phones and other
devices. They can transmit and receive radio waves, and they can convert 1s
and 0s into radio waves and convert the radio waves back into 1s and 0s.
But Wi-Fi radios have a few notable
differences from other radios:
- They transmit at frequencies of 2.4 GHz or 5 GHz. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequency allows the signal to carry more data.
- They use 802.11 networking standards, which come in several flavors:
- 802.11a transmits at 5 GHz and can move up to 54 megabits of data per second. It also uses orthogonal frequency-division multiplexing (OFDM), a more efficient coding technique that splits that radio signals into several sub-signals before they reach a receiver. This greatly reduces interference.
- 802.11b is the slowest and least expensive standard. For a while, its cost made it popular, but now it's becoming less common as faster standards become less expensive. 802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complementary code keying (CCK) modulation to improve speeds.
- 802.11g transmits at 2.4 GHz like 802.11b, but it's a lot faster -- it can handle up to 54 megabits of data per second. 802.11g is faster because it uses the same OFDM coding as 802.11a.
- 802.11n is the most widely available of the standards and is backward compatible with a, b and g. It significantly improved speed and range over its predecessors. For instance, although 802.11g theoretically moves 54 megabits of data per second, it only achieves real-world speeds of about 24 megabits of data per second because of network congestion. 802.11n, however, reportedly can achieve speeds as high as 140 megabits per second. 802.11n can transmit up to four streams of data, each at a maximum of 150 megabits per second, but most routers only allow for two or three streams.
- 802.11ac is the newest standard as of early 2013. It has yet to be widely adopted, and is still in draft form at the Institute of Electrical and Electronics Engineers (IEEE), but devices that support it are already on the market. 802.11ac is backward compatible with 802.11n (and therefore the others, too), with n on the 2.4 GHz band and ac on the 5 GHz band. It is less prone to interference and far faster than its predecessors, pushing a maximum of 450 megabits per second on a single stream, although real-world speeds may be lower. Like 802.11n, it allows for transmission on multiple spatial streams -- up to eight, optionally. It is sometimes called 5G Wi-Fi because of its frequency band, sometimes Gigabit Wi-Fi because of its potential to exceed a gigabit per second on multiple streams and sometimes Very High Throughput (VHT) for the same reason.
- Other 802.11 standards focus on specific applications of wireless networks, like wide area networks (WANs) inside vehicles or technology that lets you move from one wireless network to another seamlessly.
- Wi-Fi radios can transmit on any of three frequency bands. Or, they can "frequency hop" rapidly between the different bands. Frequency hopping helps reduce interference and lets multiple devices use the same wireless connection simultaneously.
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