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Wireless Network Standards - 802.11a, 802.11b, 802.11g, 802.11n, 802.16

The following describes the current defined wireless protocol standards.

802.11a

This standard was approved in 1999 with the IEEE committee. It specifies a maximum data rate of 54 Mbps using 5.15 GHz - 5.35 GHz and 5.725 GHz - 5.825 GHz unlicensed bands in the United States. The advantage of 802.11a is higher throughput however the cell coverage is smaller and additional access points will be needed. There is much less interference from devices such as cell phones, microwaves and commercial devices using the 2.4 GHz band.

There are 23 non-overlapping channels with the current 802.11h specification. Some Cisco devices support both 2.4 GHz and 5 GHz transmitters on the same access point. The modulation scheme used with 802.11a is OFDM which is effective, allowing higher data rates and minimizes affects of interference. An advantage of 802.11a is the continued deployment around the world however each country specifies number of channels and frequencies with the 5 GHz band. It is a good practice to separate neighbor channels with non-neighbor assignments.

80.11b

This standard was approved in 1999 with the IEEE committee. It specifies a maximum data rate of 11 Mbps using the 2.412 GHz - 2.484 GHz unlicensed band in the United States. That band experiences a lot of interference from commercial devices using that frequency. The standard in the United States specifies 11 channels with a bandwidth of around 80 MHz at 5 MHz per channel.

The United States allocates 3 non-overlapping channels of 1, 6 and 11 with center frequency separation of 25 MHz per channel. The modulation scheme used with 802.11b is Direct Sequence Spread Spectrum (DSSS) with CCK which has characteristics that minimize affects associated with interference. 802.11b transmit speeds include 1, 2, 5.5 and 11 Mbps.

802.11g

This standard was approved in 2003 with the IEEE committee. It specifies a maximum data rate of 54 Mbps using the same 2.4 GHz band as 802.11b. The 802.11g standard is most popular around the United States with high throughput, increased coverage and less cost. The same interference occurs however with the 2.4 GHz band. The 802.11g is compatible with 802.11b standard and assigns the same 11 channels with 1, 6 and 11 as non-overlapping. The modulation scheme used with 802.11g is OFDM with higher data rates specified. 802.11g specification has transmit speeds including 6, 9, 12, 18, 24, 36 and 48 Mbps.

802.16

This is a wireless standard focused on MAN implementations allowing home and office seamless wireless access from devices anywhere across a metropolitan city with line of sight distances of around 27 miles and speeds of 120 Mbps. The point to multipoint specification operates in the 10 - 66 GHz range. There is an 802.16a specification with mesh topologies and non line of sight that describes frequencies from the licensed and unlicensed 2 GHz and 11 GHz band at a speed of 70 Mbps. The key issue with any MAN implementation and all fixed wireless has to do with interference and frequency your equipment is assigned. The unlicensed frequencies will of course be vulnerable to interference from similar devices across the city.

802.11n

This new standard specifies faster rates of 600 Mbps between access points and 1000 Mbps from access point to network switch increasing throughput from the current 100 Mbps.

WiFi Alliance Forum

Tests and certifies manufacturer wireless products for conformity with specific wireless standards. Devices that have been certified interoperable can be deployed in mixed multi vendor environments.


Shaun Hummel is the author of Cisco Wireless Network Design Guide and has a web site focused on information technology solutions, online technical interviews and certifications.

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