Basics of Wi-Fi

Over the past two decades, the demand for wireless service has grown at an extraordinary pace. The industry has grown from pagers, and  cellular phones  to Personal Communication Systems (PCS) and wireless local area networks (WLANs), providing services that deliver voice, data, and video in real time.  For some time, wireless communications have been evolving from voice and low data rate services towards high bit rate services like video-telephony and multimedia). In addition, wireless-in-house communications with a high degree of mobility are also emerging rapidly. Wi-Fi Access Points are being installed in almost every conceivable location from public areas such as airports, coffee bars to private homes and even on the masts of boats.

The performance of wireless communication systems depends on the radio wave transmission path between the transmitter and the receiver. Unlike their wired counterparts whose distance limitations and data rates are fully understood due to the use of specific standards and controlled media, distance limitation (i.e. the range) and data rates of Wi-Fi networks are more difficult to determine.  They interact with the environment through which they propagate by means of reflection, refraction and scattering, hence their (almost) random nature. It is essential to understand the propagation characteristics for a proposed WLAN before deployment.

802.11a and 802.11b are some of the oldest the Wi-Fi standards and operate on the 5GHz and 2.4GHz frequencies respectively. It could be said that 802.11b was the standard that popularized Wi-Fi, and many legacy devices still utilize this standard today. The biggest differentiators between these original standards from a practical standpoint are speed and range. 802.11a enables speeds of up to 54Mbit/s but the shorter wavelength isn’t as effective at penetrating walls and other obstructions making it less feasible for home networks. 802.11b is limited to 11Mbit/s of throughput, but the 2.4GHz frequency handles signal degradation better.

802.11g combined the benefits of its predecessors, offering 54Mbit/s using a 2.4GHz radio. An additional benefit of using 802.11g is the backward compatibility with 802.11b client devices, though using an 802.11b device on an 802.11g network will reduce the data rate for all clients to 11Mbit/s.

802.11n is the current Wi-Fi standard, and supports the use of both 2.4GHz and 5GHz bands. This ability to use both sets of frequencies is known as MIMO (Multiple-Input Multiple-Output). The key benefits to using 802.11n devices are data rates up to 600MBit/s, and some additional security features. 802.11n offers backward compatibility, though for performance reasons these features are optional, and are not always enabled.