Wireless LAN networks are composed of devices that communicate with each other wirelessly using air (space) as the communication medium. There are two types of wireless networks - adhoc networks and infrastructure networks.
In an adhoc network the different wireless devices communicate peer to peer. In an infrastructure type wireless network, all the devices connect to an access point which in turn connects to a wired network.
The most popular WLAN standard today is IEEE 802.11 commonly known as "Wi-Fi". As all WLAN types use air (space) as the communication medium, the distinction is based on frequency bands and modulation techniques used.
The most common frequency bands used by WiFi are 2.4 GHz and 5 GHz. Of these 2.4 GHz is a crowded frequency band because lots of household equipments also use the same band (E.g. microwave ovens, baby monitors, bluetooth devices, cordless phones, amateur radio). Hence WLANs operating in this band often experience interference from these equipments.
The 5GHz ones have the advantage of less interference because this frequency band is relatively un-crowded. But the disadvantage is that higher frequency waves are absorbed more easily by walls and obstacles and hence the range is reduced.
| Standard | Frequency (GHz) | Max. Data Rate (Mbps) | Max. Outdoor Range (m) | Modulation |
|---|---|---|---|---|
| IEEE 802.11a | 5 | 54 | 100 | OFDM |
| IEEE 802.11b | 2.4 | 11 | 140 | DSSS |
| IEEE 802.11g | 2.4 | 54 | 140 | OFDM, DSSS |
| IEEE 802.11n | 2.4 / 5 | 300* | 250 | OFDM |
* The IEEE 802.11n uses MIMO (Multiple Input Multiple Output) antennas and can achieve speeds up to 600 Mbps theoretically. But in practical situations under best conditions, 300 Mbps is the highest speed achieved. The fastest products in market are those using n mode (IEEE 802.11n)
Most wireless adapters and access points these days support multiple frequency bands (2.4/5) and multiple modes (a/b/g/n). Dual band bi mode devices usually support 2.4/5 and a/b. Dual band trimode devices support 2.4/5 and a/b/g modes. Single band trimode devices support 2.4 GHz band and b/g/n modes.
At the time of this writing there are faster standards which are still under development and not yet marketed.
| Standard | Frequency (GHz) | Max. Data Rate (Mbps) |
|---|---|---|
| IEEE 802.11ac | 5 | 500 - 1000 |
| IEEE 802.11ad | 2.4/5/60 | 7000 |
With the advent of HD displays, there is a need for increased data rate on wireless networks. The newer ac and ad standards aim to achieve this. They operate in higher frequencies and have higher speeds, but the range is reduced because of higher frequencies. These are well suited for small areas that need high data rate such as a conference room that has high speed devices and HD displays connected wirelessly.
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