IEEE 802.11g-2003
This articleneeds additional citations forverification.(February 2017) |
Generation | IEEE standard |
Adopted | Maximum link rate (Mb/s) |
Radio frequency (GHz) |
---|---|---|---|---|
Wi-Fi 8 | 802.11bn | expected 2028[1] | 100 000[2] | 2.4, 5, 6[3] |
Wi-Fi 7 | 802.11be | expected 2024 | 0.4–23 059 | 2.4, 5, 6[4] |
Wi-Fi 6E | 802.11ax | 2021 | 0.4–9608[5] | 2.4, 5, 6[a] |
Wi-Fi 6 | 2.4, 5 | |||
Wi-Fi 5 | 802.11ac | 2013 | 6.5–6933 | 5[b] |
Wi-Fi 4 | 802.11n | 2009 | 6.5–600 | 2.4, 5 |
(Wi-Fi 3)* | 802.11g | 2003 | 6–54 | 2.4 |
(Wi-Fi 2)* | 802.11a | 1999 | 5 | |
(Wi-Fi 1)* | 802.11b | 1999 | 1–11 | 2.4 |
(Wi-Fi 0)* | 802.11 | 1997 | 1–2 | 2.4 |
*Wi‑Fi 0,1,2,and3are named by retroactive inference. They do not exist in the official nomenclature.[6][7][8] |
IEEE 802.11g-2003or802.11gis an amendment to the IEEE 802.11 specification that operates in the 2.4GHzmicrowave band. The standard has extended link rate to up to 54Mbit/susing the same 20 MHzbandwidthas802.11buses 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 802.11-2007standard, and Clause 19 of the publishedIEEE 802.11-2012standard.
802.11is a set ofIEEEstandards that govern wireless networking transmission methods. They are commonly used today in their802.11a,802.11b,802.11g,802.11n,802.11acand802.11axversions 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.
Descriptions[edit]
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/CAtransmission scheme, 31.4 Mbit/s[9]is the maximum netthroughputpossible for packets of 1500 bytes in size and a 54 Mbit/s wireless rate (identical to802.11acore, 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.[9]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/CTStransmissions and a "back off" mechanism.[10]Some 802.11g routers employ a back-compatible mode for 802.11b clients called 54g LRS (Limited Rate Support).[11]
The modulation scheme used in 802.11g isorthogonal frequency-division multiplexing(OFDM) copied from802.11awith 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+DSSSfor 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.
Technical description[edit]
Of the 52 OFDM subcarriers, 48 are for data and 4 arepilot subcarrierswith a carrier separation of 0.3125 MHz (20 MHz/64). Each of these subcarriers can be aBPSK,QPSK,16-QAMor 64-QAM.The total bandwidth is 22 MHz with an occupied bandwidth of 16.6 MHz. Symbol duration is 4microseconds,whichincludesa 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 usingOFDMinclude reduced multipath effects in reception and increased spectral efficiency.[12]
MCS index(read as little endian) | RATE bits R1-R4 | Modulation type |
Coding rate |
Data rate (Mbit/s) |
---|---|---|---|---|
11 | 1101 | BPSK | 1/2 | 6 |
15 | 1111 | BPSK | 3/4 | 9 |
10 | 0101 | QPSK | 1/2 | 12 |
14 | 0111 | QPSK | 3/4 | 18 |
9 | 1001 | 16-QAM | 1/2 | 24 |
13 | 1011 | 16-QAM | 3/4 | 36 |
8 | 0001 | 64-QAM | 2/3 | 48 |
12 | 0011 | 64-QAM | 3/4 | 54 |
Adoption[edit]
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,Bluetoothdevices, 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 lobesexists, though it is considerably weaker.
Channels and frequencies[edit]
![](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/NonOverlappingChannels2.4GHz802.11-en.svg/330px-NonOverlappingChannels2.4GHz802.11-en.svg.png)
Channel | Center frequency (GHz) |
Span (GHz) |
Overlapping channels |
---|---|---|---|
1 | 2.412 | 2.401–2.423 | 2, 3, 4, 5* |
2 | 2.417 | 2.406–2.428 | 1, 3, 4, 5, 6* |
3 | 2.422 | 2.411–2.433 | 1, 2, 4, 5, 6, 7* |
4 | 2.427 | 2.416–2.438 | 1, 2, 3, 5, 6, 7, 8* |
5 | 2.432 | 2.421–2.443 | 1*, 2, 3, 4, 6, 7, 8, 9* |
6 | 2.437 | 2.426–2.448 | 2*, 3, 4, 5, 7, 8, 9, 10* |
7 | 2.442 | 2.431–2.453 | 3*, 4, 5, 6, 8, 9, 10, 11* |
8 | 2.447 | 2.436–2.458 | 4*, 5, 6, 7, 9, 10, 11, 12* |
9 | 2.452 | 2.441–2.463 | 5*, 6, 7, 8, 10, 11, 12, 13* |
10 | 2.457 | 2.446–2.468 | 6*, 7, 8, 9, 11, 12, 13* |
11 | 2.462 | 2.451–2.473 | 7*, 8, 9, 10, 12, 13* |
12 | 2.467 | 2.456–2.478 | 8*, 9, 10, 11, 13, 14* |
13 | 2.472 | 2.461–2.483 | 9*, 10, 11, 12, 14* |
14 | 2.484 | 2.473–2.495 | 12, 13 |
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.
Comparison[edit]
Click on "show".
Frequency range, or type |
PHY | Protocol | Release date[14] |
Frequency | Bandwidth | Stream data rate[15] |
Allowable MIMOstreams |
Modulation | Approximate range | |||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Indoor | Outdoor | |||||||||||
(GHz) | (MHz) | (Mbit/s) | ||||||||||
1–7GHz | DSSS[16], |
802.11-1997 | June 1997 | 2.4 | 22 | 1, 2 | — | DSSS, |
20 m (66 ft) | 100 m (330 ft) | ||
HR/DSSS[16] | 802.11b | September 1999 | 2.4 | 22 | 1, 2, 5.5, 11 | — | CCK,DSSS | 35 m (115 ft) | 140 m (460 ft) | |||
OFDM | 802.11a | September 1999 | 5 | 5, 10, 20 | 6, 9, 12, 18, 24, 36, 48, 54 (for 20MHz bandwidth, divide by 2 and 4 for 10 and 5MHz) |
— | OFDM | 35 m (115 ft) | 120 m (390 ft) | |||
802.11j | November 2004 | 4.9, 5.0 [B][17] |
? | ? | ||||||||
802.11y | November 2008 | 3.7[C] | ? | 5,000 m (16,000 ft)[C] | ||||||||
802.11p | July 2010 | 5.9 | 200 m | 1,000 m (3,300 ft)[18] | ||||||||
802.11bd | December 2022 | 5.9, 60 | 500 m | 1,000 m (3,300 ft) | ||||||||
ERP-OFDM[19] | 802.11g | June 2003 | 2.4 | 38 m (125 ft) | 140 m (460 ft) | |||||||
HT-OFDM[20] | 802.11n (Wi-Fi 4) |
October 2009 | 2.4, 5 | 20 | Up to 288.8[D] | 4 | MIMO-OFDM (64-QAM) |
70 m (230 ft) | 250 m (820 ft)[21] | |||
40 | Up to 600[D] | |||||||||||
VHT-OFDM[20] | 802.11ac (Wi-Fi 5) |
December 2013 | 5 | 20 | Up to 693[D] | 8 | DL MU-MIMOOFDM (256-QAM) |
35 m (115 ft)[22] | ? | |||
40 | Up to 1600[D] | |||||||||||
80 | Up to 3467[D] | |||||||||||
160 | Up to 6933[D] | |||||||||||
HE-OFDMA | 802.11ax (Wi-Fi 6, Wi-Fi 6E) |
May 2021 | 2.4, 5, 6 | 20 | Up to 1147[E] | 8 | UL/DL MU-MIMOOFDMA (1024-QAM) |
30 m (98 ft) | 120 m (390 ft)[F] | |||
40 | Up to 2294[E] | |||||||||||
80 | Up to 5.5Gbit/s[E] | |||||||||||
80+80 | Up to 11.0Gbit/s[E] | |||||||||||
EHT-OFDMA | 802.11be (Wi-Fi 7) |
Dec 2024 (est.) |
2.4, 5, 6 | 80 | Up to 11.5Gbit/s[E] | 16 | UL/DL MU-MIMOOFDMA (4096-QAM) |
30 m (98 ft) | 120 m (390 ft)[F] | |||
160 (80+80) |
Up to 23Gbit/s[E] | |||||||||||
240 (160+80) |
Up to 35Gbit/s[E] | |||||||||||
320 (160+160) |
Up to 46.1Gbit/s[E] | |||||||||||
UHR | 802.11bn (Wi-Fi 8) |
May 2028 (est.) |
2.4, 5, 6, 42, 60, 71 |
320 | Up to 100000 (100Gbit/s) |
16 | Multi-link MU-MIMOOFDM (8192-QAM) |
? | ? | |||
WUR[G] | 802.11ba | October 2021 | 2.4, 5 | 4, 20 | 0.0625, 0.25 (62.5kbit/s, 250kbit/s) |
— | OOK(multi-carrier OOK) | ? | ? | |||
mmWave (WiGig) |
DMG[23] | 802.11ad | December 2012 | 60 | 2160 (2.16GHz) |
Up to 8085[24] (8Gbit/s) |
— | 3.3 m (11 ft)[25] | ? | |||
802.11aj | April 2018 | 60[H] | 1080[26] | Up to 3754 (3.75Gbit/s) |
— | singlecarrier, low-power single carrier[A] | ? | ? | ||||
CMMG | 802.11aj | April 2018 | 45[H] | 540, 1080 |
Up to 15015[27] (15Gbit/s) |
4[28] | OFDM,singlecarrier | ? | ? | |||
EDMG[29] | 802.11ay | July 2021 | 60 | Up to 8640 (8.64GHz) |
Up to 303336[30] (303Gbit/s) |
8 | OFDM,singlecarrier | 10m (33ft) | 100m (328ft) | |||
Sub 1 GHz (IoT) | TVHT[31] | 802.11af | February 2014 | 0.054– 0.79 |
6, 7, 8 | Up to 568.9[32] | 4 | MIMO-OFDM | ? | ? | ||
S1G[31] | 802.11ah | May 2017 | 0.7, 0.8, 0.9 |
1–16 | Up to 8.67[33] (@2MHz) |
4 | ? | ? | ||||
Light (Li-Fi) |
LC (VLC/OWC) |
802.11bb | December 2023 (est.) |
800–1000 nm | 20 | Up to 9.6Gbit/s | — | O-OFDM | ? | ? | ||
(IrDA) |
802.11-1997 | June 1997 | 850–900 nm | ? | 1, 2 | — | ? | ? | ||||
802.11 Standard rollups | ||||||||||||
802.11-2007 (802.11ma) | March 2007 | 2.4, 5 | Up to 54 | DSSS,OFDM | ||||||||
802.11-2012 (802.11mb) | March 2012 | 2.4, 5 | Up to 150[D] | DSSS,OFDM | ||||||||
802.11-2016 (802.11mc) | December 2016 | 2.4, 5, 60 | Up to 866.7 or 6757[D] | DSSS,OFDM | ||||||||
802.11-2020 (802.11md) | December 2020 | 2.4, 5, 60 | Up to 866.7 or 6757[D] | DSSS,OFDM | ||||||||
802.11me | September 2024 (est.) |
2.4, 5, 6, 60 | Up to 9608 or 303336 | DSSS,OFDM | ||||||||
|
See also[edit]
- Clear channel assessment attack
- List of WLAN channels
- OFDM system comparison table
- Spectral efficiency comparison table
- Wi-Fi
- Super G (wireless networking)
- Xpress technology
Notes[edit]
References[edit]
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