Wireless Network Standards - 802.11a, 802.11b, 802.11g, 802.11n, 802.16
By Shaun Hummel
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.
More Networking Protocols and Standards:
• Remote Control Protocols
• A Simple Description of the IPv6 Header and Datagram
• Video Streaming Protocols
• The OSI Physical Layer
• IGRP (Interior Gateway Routing Protocol)
• TCP/IP Utilities
• IP Addressing and Subnetting
• The OSI Application Layer
• IPv6 Payload Length Field and Jumbograms
• Network Switches
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