IEEE 802.11g-2003

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IEEE 802.11g-2003 or 802.11g, is an amendment to the IEEE 802.11 specification that extended throughput to up to 54 Mbit/s using the same 2.4 GHz band as 802.11b. This specification under the marketing name of Wi-Fi has been implemented all over the world. The 802.11g protocol is now Clause 19 of the published IEEE 802.11-2007 standard.

Contents 1 Descriptions 2 Adoption 3 Comparison chart 4 See also 5 References

[edit] Descriptions

802.11g was the third modulation standard for Wireless LAN. It works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mbit/s, or about 19 Mbit/s net throughput (identical to 802.11a core, except for some additional legacy overhead for backward compatibility). 802.11g hardware is fully backwards compatible with 802.11b hardware. Details of making b and g work well together occupied much of the lingering technical process. In an 11g network, however, the presence of a legacy 802.11b participant will significantly reduce the speed of the overall 802.11g network.

The modulation scheme used in 802.11g is orthogonal frequency-division multiplexing (OFDM) copied from 802.11a with data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbit/s, and reverts to CCK (like the 802.11b standard) for 5.5 and 11 Mbit/s and DBPSK/DQPSK+DSSS for 1 and 2 Mbit/s. Even though 802.11g operates in the same frequency band as 802.11b, it can achieve higher data rates because of its heritage to 802.11a.

[edit] Adoption

The then-proposed 802.11g standard was rapidly adopted by consumers starting in January 2003, well before ratification, due to the desire for higher speeds, and reductions in manufacturing costs. By summer 2003, most dual-band 802.11a/b products became dual-band/tri-mode, supporting a and b/g in a single mobile adapter card or access point.

Despite its major acceptance, 802.11g suffers from the same interference as 802.11b in the already crowded 2.4 GHz range. Devices operating in this range include: microwave ovens, Bluetooth devices, baby monitors and, in the United States, digital cordless telephones, which can lead to interference issues. Additionally, the success of the standard has caused usage/density problems related to crowding in urban areas. To prevent interference, there are only three non-overlapping usable channels in the U.S. and other countries with similar regulations (channels 1, 6, 11, with 25MHz separation), and four in Europe (channels 1, 5, 9, 13, with only 20MHz separation). Even with such separation, some interference due to side lobes exists, though it is considerably weaker.

[edit] Comparison chart

Wireless local area network standards  view • talk • edit 

802.11 Protocol	Release[1]	Freq. (GHz)	Typ throughput (Mbit/s) [citation needed]	Max net bitrate (Mbit/s)	Modulation	rin. (m)	rout. (m)
–	Jun 1997	2.4	00.9	002	DSSS	~20	~100
a	Sep 1999	5	23	054	OFDM	~35	~120
b	Sep 1999	2.4	04.3	011	DSSS	~38	~140
g	Jun 2003	2.4	19	054	OFDM	~38	~140
n	~ Nov 2009	2.4 5	130[2]	600[3]	OFDM	~70	~250[4]
y	Nov 2008	3.7	23	054	OFDM	~50	~5000

[edit] See also

• IEEE 802.11
• IEEE 802.11b-1999
• IEEE 802.11n
• List of WLAN channels
• OFDM system comparison table
• Spectral efficiency comparison table
• Wi-Fi

[edit] References

• "IEEE 802.11g-2003: Further Higher Data Rate Extension in the 2.4 GHz Band" (pdf). IEEE. 2003-10-20. http://standards.ieee.org/getieee802/download/802.11g-2003.pdf. Retrieved on 2007-09-24.