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Wi-Fi generations

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Generation	Visual	IEEE standard	Adopted	Maximum link rate (Mbit/s)	Radio frequency (GHz)
—	—	802.11	1997	1–2	2.4
—	—	802.11b	1999	1–11	2.4
—	—	802.11a	1999	6–54	5
—	—	802.11g	2003		2.4
Wi-Fi 4		802.11n	2009	6.5–600	2.4, 5
Wi-Fi 5		802.11ac	2013	6.5–6933	5[a]
Wi-Fi 6		802.11ax	2021	0.4–9608	2.4, 5
Wi-Fi 6E					6[b]
Wi-Fi 7		802.11be	2024[c]	0.4–23,059	2.4, 5, 6
Wi-Fi 8[1][2]	—	802.11bn		100,000	2.4, 5, 6

IEEE 802.11g-2003 or802.11g is an amendment to the IEEE 802.11 specification that operates in the 2.4GHz microwave band. The standard has extended link rate to up to 54Mbit/s using the same 20 MHzbandwidth as802.11b uses to achieve 11 Mbit/s. This specification, under the marketing name ofWi‑Fi, has been implemented all over the world. The 802.11g protocol is now Clause 19 of the publishedIEEE 802.11-2007 standard, and Clause 19 of the publishedIEEE 802.11-2012 standard.

802.11 is a set ofIEEE standards that govern wireless networking transmission methods. They are commonly used today in their802.11a,802.11b, 802.11g,802.11n,802.11ac and802.11ax versions to provide wireless connectivity in the home, office and some commercial establishments.

802.11g is fully backward compatible with 802.11b, but coexistence of the two methods creates a significant performance penalty.

802.11g is the third modulation standard forwireless LANs. It works in the 2.4 GHz band (like802.11b) but operates at a maximum raw data rate of 54 Mbit/s. Using theCSMA/CA transmission scheme, 31.4 Mbit/s^[3] is the maximum netthroughput possible for packets of 1500 bytes in size and a 54 Mbit/s wireless rate (identical to802.11a core, except for some additional legacy overhead for backward compatibility). In practice, access points may not have an ideal implementation and may therefore not be able to achieve even 31.4 Mbit/s throughput with 1500 byte packets. 1500 bytes is the usual limit for packets on the Internet and therefore a relevant size to benchmark against. Smaller packets give even lower theoretical throughput, down to 3 Mbit/s using 54 Mbit/s rate and 64 byte packets.^[3] Also, the available throughput is shared between all stations transmitting, including the AP so both downstream and upstream traffic is limited to a shared total of 31.4 Mbit/s using 1500 byte packets and 54 Mbit/s rate.

802.11g hardware is fully backward compatible with 802.11b hardware. Details of making b and g work well together occupied much of the lingering technical process. In an 802.11g network, however, the presence of a legacy 802.11b participant will significantly reduce the speed of the overall 802.11g network, as airtime needs to be managed byRTS/CTS transmissions and a "back off" mechanism.^[4] Some 802.11g routers employ a back-compatible mode for 802.11b clients called 54g LRS (Limited Rate Support).^[5]

The modulation scheme used in 802.11g isorthogonal frequency-division multiplexing (OFDM) copied from802.11a with data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbit/s, and reverts toCCK (like the 802.11b standard) for 5.5 and 11 Mbit/s andDBPSK/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 better modulation from 802.11a.

Of the 52 OFDM subcarriers, 48 are for data and 4 arepilot subcarriers with a carrier separation of 0.3125 MHz (20 MHz/64). Each of these subcarriers can be aBPSK,QPSK, 16-QAM or 64-QAM. The total bandwidth is 22 MHz with an occupied bandwidth of 16.6 MHz. Symbol duration is 4microseconds, whichincludes a guard interval of 0.8 microseconds. The actual generation and decoding of orthogonal components is done in baseband using DSP which is then upconverted to 2.4 GHz at the transmitter. Each of the subcarriers could be represented as a complex number. The time domain signal is generated by taking an InverseFast Fourier transform (IFFT). Correspondingly the receiver downconverts, samples at 20 MHz and does an FFT to retrieve the original coefficients. The advantages of usingOFDM include reduced multipath effects in reception and increased spectral efficiency.^[6]

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 mid-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.^{[citation needed]}

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 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 25 MHz separation), and four in Europe (channels 1, 5, 9, 13, with only 20 MHz separation). Even with such separation, some interference due toside lobes exists, though it is considerably weaker.

Notes:

• Not all channels are legal to use in all countries. In particular, no countries in the world permit the use of channel 14 for 802.11g. Channels 12 and 13 are avoided in the United States due to a misinterpretation of regulations.
• Overlaps noted with an asterisk (*) indicate overlap only in the 22 MHz width, while 802.11g only requires 20 MHz (the actual occupied bandwidth is even lower, 16.25 MHz). As a result, such overlaps have minimal performance implications.

Click on "show".

• Clear channel assessment attack
• List of WLAN channels
• OFDM system comparison table
• Spectral efficiency comparison table
• Wi-Fi
• Super G (wireless networking)
• Xpress technology

• "IEEE 802.11g-2003: Further Higher Data Rate Extension in the 2.4 GHz Band"(PDF).IEEE. 2003-10-20. Archived fromthe original(PDF) on July 23, 2004. Retrieved2007-09-24.

[[ja:IEEE 802.11#IEEE 802.11g]]

• IEEE 802.11

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