Wireless routers use the IEEE802.11 standards to communicate with user's computers. These standards were developed by the IEEE (Institute of Electronic and Electrical Engineers) which is a nonprofit making organization. IEEE (often pronounced as eye-triple-E) has developed many different communications standards to make sure devices from different vendors can communicate with each other.
The first design began in 1990 and it took 7 years to be completed. It uses the 2.4 GHz radio band for communication. Users do not need a license to use this band in most countries. This is one of the reasons that this standard has become so popular. The standard specifies the communication between wireless client and the access points. It also defines the optional use of encryption. However, there are some well-known security weaknesses in this standard and the maximum speed is only 2 Mbps. This version is obsolete now.
To overcome the shortcomings of the first design, IEEE workgroups have developed new IEEE802.11 standards. They differentiate these newer standards by appending a letter behind the 802.11. Although there are large numbers of new standards, only four standards have products in the market now. They are IEEE802.11a, IEEE802.11b, IEEE802.11g, and IEEE802.11n.
Before 2003, the most popular standard was the IEEE802.11b. Under this standard, the data transfer rate is improved to 11 Mbps and the range to 100 m while still using the 2.4 GHz radio band. Access points and network cards using this standard are inexpensive. Devices from different vendors are extremely compatible with each other. Installation is easy and there is widespread use in small offices and homes. As the standard is slower than 11a and 11g, 11b products have been phasing out of the market in recent years. However, there are still a large number of 11b devices in use today.
On the other hand, IEEE802.11a offers much higher speed (up to 54 Mbps). It uses the 5 GHz radio band so it avoids interference from electronic devices (such as microwave ovens, cordless phones, etc.). A wireless signal spectrum is presented in Fig. 4. However, this radio band is not available for unlicensed use in all countries. Another problem is that IEEE802.11a devices are not backward compatible to the slower IEEE802.11b. This problem may be a barrier deterring organizations which already have IEEE802.11b devices from deploying 802.11a.