What exactly is 802.11 and how does it pertain to a WiFi Hotspot?

The 808.11 specification defines the requirements for computer wireless digital communications.

What exactly is 802.11?

Well - according to Webopedia 802.11 is:

802.11 refers to a family of specifications developed by the IEEE for wireless LAN technology. 802.11 specifies an over-the-air interface between a wireless client and a base station or between two wireless clients in a wireless networking environment. The IEEE accepted the specification in 1997.

There are several specifications in the 802.11 family:

802.11 -- applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS).

802.11a -- an extension to 802.11 that applies to wireless LANs and provides up to 54 Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing (OFDM) encoding scheme rather than FHSS or DSSS.

802.11b (also referred to as 802.11 High Rate or Wi-Fi) -- an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet.

802.11g -- applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band.

802.11n -- applies to wireless LANs and provides 100+ Mbps in the 2.4 GHz band. This is the new kid on the block as it was just ratified in January 2006 by the IEEE.

As you can see the different "versions" of 802.11 are specifications as to how the over-the-air wirless network is supposed to work - so the 802.11 is actually a set of documents which define how the wireless network communications protocols work.

So - how does the above relate to wireless hotspots?

When wireless communications between computers first started there were no "standard" specifications for the method used to transmit the information using radio communications.  Different manufacturers had different "ideas" of how to "best" implement the communications.  It was apparent at a very early stage in the development of the technology that Standards were needed if the different equipment manufacturer's equipment was to work together - otherwise you would have to use a specific manufacturer's equipment to "connect" to the specific wireless network. This is not a viable solution as different manufacturers would develop different functionality in their equipment which is not conducive to the development of general wireless communications use.

The current version of the 802.11 specification in use today is the 802.11b and 802.11g protocols - the 2.4-GHz 11-Mbps and 20+ Mbps specifications.  These two protocols are very simular in that they both operate in the 2.4-GHz frequency range with the major difference in the transmission protocol used for the communications.  Both use DSSS for the actual data transmission method but the 802.11g uses a different data-packing algorythm than the 802.11b protocol so is able to "pack" about five times the information within the same transmission.  The ability to send more information within the same transmission allows more data to be sent in the same amount of time.

To a lesser extent is the 802.11a protocal usage for wireless communications.  The protocol allows 20+ Mbps but since the equipment operates in the 5.4 - 5.8 GHz range the actual transmission range is reduced over the range of the equipment operating within the 2.4-GHz range.  The reduction in range has to do with the effective radiation of the radio signal and the signal's antenuation through air and materials.  Typically the higher the operating frequency the more signal loss experienced.  A second limitation is the fact the equipment operating within the higher frequency range does not have the same sensitivity than the equipment operating within the 2.4-GHz range - mostly due to the limitations of commercial grade electronics.

Even with the limitations of the 802.11a equipment it is being used in "back-haul" applications - basically the point-to-point communications between a base-station location and an 802.11b/g access point location.  Part of the reason to use a configuration as just described would be to allow all of the 802.11b/g channels to be used for the general location without having to define a channel in the 802.11b/g range for the back-haul link.  Configuring a wireless network in such a manner allows more access points in a given area since there are more radio channels available for use in the 802.11b/g communications.  Given some countries limit the number of radio channels available for use in the 802.11b/g systems the use of 802.11a for point-to-point communications can make a substancial difference in the total number of client connections possible in a given area of coverage!

The new kid on the block - the 802.11n specification will add even greater useful data throughput in the world of wireless computer networking.  The specification calls for up to about 500-Mbps throughput (in one direction) so the actual usable throughput should be around 100+ Mbps.  The throughput for 802.11n will be equivelent to a wired 100BaseT network! 

Of course the 802.11n specification was just ratified January 2006 so it will be interesting to follow the development of the actual hardware implementations to see if it indeed meets these lofty goals....

Stay tuned!

Author: Gary N. McKinney