IEEE 802.11g IEEE 802.11g StandardStandard

Tim WellsMicrocomputer Networks (CIS362)

Thursday, April 28, 2005

What is 802.11g?

IEEE Standard 802.11g is the latest Wireless Networking

Standard that was created to increase range and speed while

being compatible with the popular 802.11b.

Going Back In History…

Before 802.11g There was: 802.11 802.11b 802.11a

IEEE 802.11

Standard approved 1997

Max Data Rate 1-2 Mbps

Modulation DSSS

Frequency 2.4 GHz

802.11 had limited success due to low speeds and high prices.

IEEE 802.11b

Standard approved 1999

Max Data Rate 11 Mbps

Modulation DSSS + CCK

Frequency 2.4 GHz

802.11b greatly improved speed while maintaining compatibility with 802.11. 802.11b products received mainstream recognition as the first wireless products with acceptable speeds, affordable prices, and universal compatibility. More than 95% of todays WLAN infrastructure includes 802.11b products.

IEEE 802.11a

Standard approved 1999

Max Data Rate 54 Mbps

Modulation OFDM

Frequency 5.2 GHz

802.11a greatly increased speed, but decreased range. Even though the 802.11a standard was adopted in 1999, the first 802.11a products were not available until late 2001. 802.11a had a limited market response because of its incompatibility with 802.11b, shorter range, and higher costs.

IEEE 802.11g

Standard approved 2003

Max Data Rate 54 Mbps (108 Mbps*)

Modulation OFDM + CCK

Frequency 5.2 GHz

802.11g increased speed and range while maintaining compatibility with 802.11b. Even though 802.11g was not officially approved by IEEE until June 2003, products conforming to the draft were made available in late 2002.

* With Atheros Super G

What is CCK?

Complementary Code Checking Was incorporated into DSSS beginning with

802.11b to increase efficiency. CCK is a “single carrier” system, meaning that

all data is transmitted by modulating a single radio frequency or carrier.

What is OFDM?

Orthogonal Frequency Division Multiplexing Was first implemented in 802.11a. OFDM is a “multi-carrier” modulation scheme. Data is split up among several closely spaced

“subcarriers” or frequencies, increasing reliability and speed

Range Comparison

802.11g Operating Modes

802.11g Operating Modes

Can 802.11g really get up to 108 Mbps?

Yes, with Atheros’ Super G the maximum possible data rate is 108

Mbps, but the typical end user throughput is only 60+ Mbps

How does Atheros’ Super G make it faster?

Frame bursting This allows a transmitting device to send

multiple frames at once in a “burst”.

How does Atheros’ Super G make it faster?

Fast Frames Fast Frames allows more information into

each Frame

How does Atheros’ Super G make it faster?

Compression Link-level hardware compression utilizes the

connection more efficiently and maximizes bandwidth.

Dynamic Turbo Dynamic Turbo can give a significant boost in

bandwidth when required by demanding applications. It can trigger and double the apparent bandwidth by using 2 channels as one, without the user’s involvement.