802.11 WIRELESS TECHNOLOGY OVERVIEWThe IEEE standard 802.11 wireless technology, also known as Wi-Fi, has been widely popular for wireless networking and has set the bar for users' expectations with other wireless technologies. Wi-Fi technology has the advantage of reaching great distances, typically a range of around 100ft. In addition to excellent range, Wi-Fi has been very successful with computer networking because it is not dependent upon a line of sight between the transmitter and computer. This means that the access point can be placed in a single location of a building and provide signal coverage to multiple rooms. Users with a wireless network available at home or their place of work are most likely using an access point that uses 802.11 wireless technology.
Since Wi-Fi can cover multiple rooms and floors of a building, there is the potential for interference when used in environments with multiple access points or other devices that emit radio frequencies. For example, in an office environment where several access points may be installed, interference between the signals can crowd the frequency band resulting in decreased performance. This interference may also prevent some users from accessing the network. The 802.11 standard has undergone many revisions and improvements since the initial release in 1997.
Deploying a wireless connectivity solution within a data center application allows users to conveniently access the network and the information stored within the data center. This is critical in applications where users must be mobile, such as a teacher who needs move her laptop around the classroom to help students. Providing a wireless connectivity solution allows the teacher to maintain their connection to the data center and the Internet from any point within the room without a long cable connection.
- 802.11 - The original 802.11 wireless technology specification was released in 1997 and only provided for a signaling data rate of up to a 2Mbps, which was very slow in comparison to modern technologies. This initial release used the 2.4GHz band to broadcast signals. This technology is now obsolete due to the slow speed and limited range.
- 802.11b - The 802.11b specification was released in 1999 as a revision to the original specification. This specification raised the signaling data rate to 11Mbps. 802.11b also used the 2.4GHz band to broadcast signals and was backwards compatible with the original standard. This standard was widely adopted and was the first major wireless local network standard. Many computers, laptops and desktops were retrofitted with 802.11b network interface cards (NICs). One of the drawbacks to 802.11b was that the technology was susceptible to interference from other devices operating in the 2.4GHz band, i.e. microwave ovens, cordless phones, baby monitors, etc.
- 802.11a - The 802.11a specification was also released in 1999. This specification uses the 5GHz band to broadcast signals and was not compatible with earlier standards. The 802.11a specification supported a signaling data rate of up to 54Mbps. The disadvantage of using the 5GHz band was a limitation of the overall effective range. In theory, the higher frequency signals are more readily absorbed into solid objects, such as walls, which is the major contributing factor in limiting the overall effective range.
- 802.11g - The 802.11g specification was released in 2003. This specification uses the 2.4GHz band to broadcast signals and is backwards compatible with the 802.11b specification. Commonly devices that are compatible with this standard are referred to as 802.11b/g. The 802.11g specification supports a signaling data rate of up to 54Mbps. In the instance where an 802.11g device is communicating with an 802.11b device, connection speeds will be limited to 11Mbps.
- 802.11n - The 802.11n specification was released in 2009. This specification uses both the 2.4GHz and 5GHz bands to broadcast signals, which allows backwards compatibility with the 802.11b/g and 802.11a standards. The 802.11n specification supports a signaling data rate of up to 300Mbps. In the instance where an 802.11n device is communicating with a device that supports a different standard, 802.11b/g or 802.11a, then communication will be limited to the fastest common speed.
- 802.11ac and 802.11ad - 802.11ac and 802.11ad are proposed specifications which will improve upon 802.11n. 802.11ac is expected to be released in late 2012 and gain popularity by 2015. 802.11ac will use the 5GHz band to broadcast signals and will theoretically support a signaling data rate of up to 1Gbps. The 802.11ac specification will be backwards compatible with 802.11n. 802.11ad is also expected to be released in late 2012 and gain popularity by 2015. 802.11ad will use the 60GHz band to broadcast signals and will theoretically support a signaling data rate of up to 7Gbps. The 802.11ad will not be compatible with the previous 802.11 specifications.
802.11x Specification Comparison
|Number of Antennae||Signaling Rate||Channel Bandwidth||Frequency||Approx. Range (Indoor/Outdoor)|
|802.11||2 per Radio||2Mbps||20Mhz||2.4GHz||66/330ft|
|802.11b||2 per Radio||11Mbps||20Mhz||2.4Ghz||115/390ft|
|802.11a||2 per Radio||54Mbps||20Mhz||5GHz||125/460ft|
|802.11g||2 per Radio||11-54Mbps||20Mhz||2.4GHz||125/460ft|
|802.11n||4 per Radio||300Mbps||20/40Mhz||2.4/5GHz||230/820ft|
Wireless Access Point Diagram - EDU Environment
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