The Basics of Wi-FiWireless Fidelity, or Wi-Fi, allows a device to communicate wirelessly over a network. It’s one of the most popular versions of wireless networking, and it is commonly used to connect laptops, smartphones and tablets to the Internet. With a Wi-Fi-enabled device, you can connect to the Internet as long as you are within range of an access point, often referred to as a hotspot.
The term itself is a trademark of the Wi-Fi alliance, which is a trade association of companies that produce Wi-Fi products. They use the term as the consumer-facing brand for the IEEE 802.11 standard, along with its various flavors. Even though Wi-Fi is the brand name and 802.11 is the technical standard, the terms are often used synonymously, even though this isn’t completely accurate.
The IEEE StandardsThe Institute of Electrical and Electronics Engineers (IEEE) is a nonprofit, standard-setting body that oversees the 802.11 wireless standards. IEEE 802.11 is maintained by the IEEE LAN/MAN Standards Committee, the same working group that oversees other networking standards such as Ethernet, Bluetooth and WiMax. (Find out more about Bluetooth in What is the difference between Bluetooth and Wi-Fi?)
The IEEE is responsible for all the variants of 802.11. There is one 802.11 standard, but it has several versions and has undergone a number of amendments. Each version of the standard is referred to in the form of "IEEE 802.11" followed by the year that version of the standard was published. Thus, the current version is referred to as "IEEE 802.11-2007" because it was published in 2007. The original version of Wi-Fi was published back in 1997, so it’s referred to as "IEEE 802.11-1997."
The actual protocols behind these standards get updated through an amendment. These are represented by lower-case letters following 802.11. Well-known amendments include 802.11a, 802.11b, 802.11g, and 802.11.n. What is confusing is that people will refer to the "802.11b standard" even though it is actually an amendment to the standard.
A Few More ConceptsWi-Fi uses radio waves, just like cellphones do. To simplify, you can think of Wi-Fi as being similar to two-way radio communication, where a wireless adapter translates digital data into a radio signal and transmits it using an antenna. The access point receives the radio signal, decodes it, and sends it to the Internet via a (usually) physical connection. To receive data, the process works in reverse. In short, it’s all converting the digital bits (1s and 0s) into radio waves. What is important to appreciate is the greater the "wave" of a radio wave, the more data it can encode. So, some radio frequencies can inherently carry more info than others.
Wi-Fi is characterized by the frequency at which it transmits data - either within the 2.4 GHz or 5 GHz band. The 5 GHz band is able to carry more data. Besides its lower capacity, the 2.4 GHz band is also problematic in that it gets interference from things like cordless phones and microwaves.
Wi-Fi ModulationAnother defining characteristic of Wi-Fi is the modulation technique. Without getting into too much detail, here is a quick overview:
- Direct-sequence spread spectrum (DSSS) is a modulation technology that essentially spreads radio waves around. This helps to reduce interference from other devices.
- Orthogonal frequency-division multiplexing (OFDM) sends a number of small waves at a slow speed so that each wave contains part of the signal. OFDM is more efficient and results in greater throughput.
How 802.11 Protocols DifferThe 802.11 family has six main specifications:
- IEEE 802.11-1997
- IEEE 802.11a
- IEEE 802.11b
- IEEE 802.11g
- IEEE 802.11n
- IEEE 802.11ac
This was the original standard. It is sometimes referred to as 802.11 legacy. It used DSSS (as well as another modulation technique called frequency-hopping spread spectrum (FHSS)) and operated over the 2.4 GHz band. It could only transmit at 1-2 Mbps and has therefore been rendered obsolete.
802.11a is second protocol for this standard, and it came out in 1999. It operates at the 5 GHz band and uses OFDM. It provides theoretical throughput of 54 Mbps, which in practice comes out to 20 Mbps or so.
802.11b also came out in 1999 as it was developed alongside 802.11a. It operates at the 2.7 GHz band and uses DSSS. Its max throughput is 11 Mbps.
802.11g was introduced in 2003. It operates with a 2.4 GHz band like 802.11 but uses OFDM, bringing its max throughput is 54 Mbps.
If your mind is spinning by now, you aren’t alone. In 2003, ammendments "a" through "g" were combined into one version. This was called 802.11REVma while it was still being developed. It was finally approved in 2007, and was renamed IEEE 802.11-2007
IEEE 802.11n came out in 2009. It can use both 2.4 GHz and 5 GHz bands, uses OFDM, and can use multiple antennas (referred to a multiple-input multiple-output (MIMO)). The data transfer rate for this protocol is much larger than the ones that came before it - up to 300 Mbps.
The future of the 802.11 standard lies in IEEE 802.11ac, which came out in 2011 but, at the time of writing, is still in draft form. It uses the 5 GHz band and aims at transmitting at 1 Gbps.
Putting It All Together - A Short HistoryHow did we get into this alphabet soupt? As is so common in technology, Wi-Fi is a story of the struggle between technical superiority and industry marketing. The most common amendments have been 802.11.b and 802.11g, but as we’ve discussed, these aren’t the best in terms of performance.
802.11b started getting really popular in late 2000-2001. Both 802.11a and 802.11b were in development at the same time. Many people made the logical assumption that 802.11b wasn’t a second (and better) version, but was really just cheaper.
To be fair, 802.11a isn’t perfect. Its higher frequency shortened its range and made it more difficult for signals to penetrate walls. Still, it was supposed to be the standard given that it operated in the 5 GHz band at much higher speeds. What you ended up seeing were devices manufactured as 802.11a/b, which isn’t an official spec, but instead reflected that the two different technologies were packed together in a single router.
By the time 802.11g was hitting stride in 2002-2003, 802.11b was so popular that it needed to maintain backward compatibility, so 802.11g operated at the 2.4 GHz band as well. Even worse, it had to degrade to 802.11b if there was a single .b device on the network! The industry’s answer was dual-band tri/mode devices that supported both 802.11b/g and 802.11a on the access point.
802.11a, b and g have been huge commercial successes, but needs changed from when they were originally released. With more and more video, voice and other multimedia traffic going across the wires, their throughput just doesn’t cut it. 802.11n wasn’t formally approved until 2009, but devices using MIMO started appearing years earlier. If you go to buy a wireless router, the box will often claim that the transmission speed for 802.11n is 300 Mbps, but there are technical issues with this, again, mostly due to congestion issues in the 2.4 GHz band. Once again, the solution for most is to buy the tri/mode device, but this time for 802.11n combined with 802.b/g.
What to Do?This takes us to the present day. What we’ve learned is that we have 802.11.a, 802.11.b, 802.11.g and 802.11.n, although ammendments a, b and g have been wrapped up in the 802.11-2007 standard. With 802.11n, 802.11a is all but obsolete.
Unfortunately, there is no easy answer as to what is the "best." It all depends on what type of devices you have accessing your network. It’s easy to get fast speeds if you are just connecting a laptop in-house. In this case, 802.11n will do the trick. But for larger situations where there are many different devices, there probably has to be some support for 801.11b/g.
And it’s not going to get less complicated. The cycle continues, and 802.11ac is on the way. For more on this, read 802.11ac: Wireless Gigabit LAN.