IEEE 802.11g-2003

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, and Clause 19 of the published IEEE 802.11-2012 standard.

802.11 is a set of IEEE standards that govern wireless networking transmission methods. They are commonly used today in their 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac versions to provide wireless connectivity in the home, office and some commercial establishments. Wi-Fi 3 is an unofficial retronym for 802.11g[1].


802.11g is the third modulation standard for wireless LANs. It works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mbit/s. Using the CSMA/CA transmission scheme, 31.4 Mbit/s[2] is the maximum net throughput possible for packets of 1500 bytes in size and a 54 Mbit/s wireless rate (identical to 802.11a 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.[2] 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 backwards 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. Some 802.11g routers employ a back-compatible mode for 802.11b clients called 54g LRS (Limited Rate Support).

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.

Technical description

Of the 52 OFDM subcarriers, 48 are for data and 4 are pilot subcarriers with a carrier separation of 0.3125 MHz (20 MHz/64). Each of these subcarriers can be a BPSK, QPSK, 16-QAM or 64-QAM. The total bandwidth is 22 MHz with an occupied bandwidth of 16.6 MHz. Symbol duration is 4 microseconds, which includes 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 Inverse Fast Fourier transform (IFFT). Correspondingly the receiver downconverts, samples at 20 MHz and does an FFT to retrieve the original coefficients. The advantages of using OFDM include reduced multipath effects in reception and increased spectral efficiency.

MCS index RATE bits Modulation
Data rate
13 1101 BPSK 1/2 6
15 1111 BPSK 3/4 9
5 0101 QPSK 1/2 12
7 0111 QPSK 3/4 18
9 1001 16-QAM 1/2 24
11 1011 16-QAM 3/4 36
1 0001 64-QAM 2/3 48
3 0011 64-QAM 3/4 54


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.

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 to side lobes exists, though it is considerably weaker.

Channels and frequencies

2.4 GHz Wi-Fi channels (802.11b,g WLAN)
802.11b/g channels in 2.4 GHz band
IEEE 802.11g channel to frequency map [3]
Channel Center frequency Channel width Overlapping channels
1 2.412 GHz 2.401 GHz - 2.423 GHz 2,3,4,5
2 2.417 GHz 2.406 GHz - 2.428 GHz 1,3,4,5,6
3 2.422 GHz 2.411 GHz - 2.433 GHz 1,2,4,5,6,7
4 2.427 GHz 2.416 GHz - 2.438 GHz 1,2,3,5,6,7,8
5 2.432 GHz 2.421 GHz - 2.443 GHz 1,2,3,4,6,7,8,9
6 2.437 GHz 2.426 GHz - 2.448 GHz 2,3,4,5,7,8,9,10
7 2.442 GHz 2.431 GHz - 2.453 GHz 3,4,5,6,8,9,10,11
8 2.447 GHz 2.436 GHz - 2.458 GHz 4,5,6,7,9,10,11,12
9 2.452 GHz 2.441 GHz - 2.463 GHz 5,6,7,8,10,11,12,13
10 2.457 GHz 2.446 GHz - 2.468 GHz 6,7,8,9,11,12,13
11 2.462 GHz 2.451 GHz - 2.473 GHz 7,8,9,10,12,13
12 2.467 GHz 2.456 GHz - 2.478 GHz 8,9,10,11,13,14
13 2.472 GHz 2.461 GHz - 2.483 GHz 9,10,11,12,14
14 2.484 GHz 2.473 GHz - 2.495 GHz 12,13
Note: Not all channels are legal to use in all countries.

See also


  • "IEEE 802.11g-2003: Further Higher Data Rate Extension in the 2.4 GHz Band" (pdf). IEEE. 2003-10-20. Retrieved 2007-09-24.


  1. ^ Kastrenakes, Jacob (2018-10-03). "Wi-Fi now has version numbers, and Wi-Fi 6 comes out next year". The Verge. Retrieved 2018-12-28.
  2. ^ a b c Jun, Jangeun; Peddabachagari, Pushkin; Sichitiu, Mihail (2003). "Theoretical Maximum Throughput of IEEE 802.11 and its Applications" (PDF). Proceedings of the Second IEEE International Symposium on Network Computing and Applications. Archived (PDF) from the original on 2014-03-20.
  3. ^
  4. ^ "Official IEEE 802.11 working group project timelines". January 26, 2017. Retrieved 2017-02-12.
  5. ^ "Wi-Fi CERTIFIED n: Longer-Range, Faster-Throughput, Multimedia-Grade Wi-Fi® Networks" (registration required). Wi-Fi Alliance. September 2009.
  6. ^ a b On IEEE 802.11: Wireless LAN Technology
  7. ^ The complete family of wireless LAN standards: 802.11 a, b, g, j, n
  8. ^ The Physical Layer of the IEEE 802.11p WAVE Communication Standard: The Specifications and Challenges
  9. ^ a b Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice
  10. ^ "802.11n Delivers Better Range". Wi-Fi Planet. 2007-05-31.
  11. ^ "IEEE 802.11ac: What Does it Mean for Test?" (PDF). LitePoint. October 2013.
  12. ^ 802.11aj-2018 - IEEE Standard for Information Technology--Telecommunications and information exchange between systems Local and metropolitan area networks--Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 3: Enhancements for Very High Throughput to Support Chinese Millimeter Wave Frequency Bands (60 GHz and 45 GHz)
  13. ^ "802.11ad - WLAN at 60 GHz: A Technology Introduction" (PDF). Rohde & Schwarz GmbH. November 21, 2013. p. 14.
  14. ^ 802.11ad Antenna Differences: Beamsteering, Gain and Range
  15. ^ "Understanding IEEE 802.11ad Physical Layer and Measurement Challenges" (PDF).
  16. ^ 802.11aj Press Release
  17. ^ "An Overview of China Millimeter-Wave Multiple Gigabit Wireless Local Area Network System".
  18. ^ "An Overview of China Millimeter-Wave Multiple Gigabit Wireless Local Area Network System".
  19. ^ IEEE 802.11ay: 1st real standard for Broadband Wireless Access (BWA) via mmWave
  20. ^ Sun, Rob; Xin, Yan; Aboul-Maged, Osama; Calcev, George; Wang, Lei; Au, Edward; Cariou, Laurent; Cordeiro, Carlos; Abu-Surra, Shadi; Chang, Sanghyun; Taori, Rakesh; Kim, TaeYoung; Oh, Jongho; Cho, JanGyu; Motozuka, Hiroyuki; Wee, Gaius. "P802.11 Wireless LANs". IEEE. pp. 2, 3. Archived from the original on 2017-12-06. Retrieved December 6, 2017.
  21. ^ a b 802.11 Alternate PHYs A whitepaper by Ayman Mukaddam
  22. ^ Lee, Wookbong; Kwak, Jin-Sam; Kafle, Padam; Tingleff, Jens; Yucek, Tevfik; Porat, Ron; Erceg, Vinko; Lan, Zhou; Harada, Hiroshi (2012-07-10). "TGaf PHY proposal". IEEE P802.11. Retrieved 2013-12-29.
  23. ^ Sun, Weiping; Choi, Munhwan; Choi, Sunghyun (July 2013). "IEEE 802.11ah: A Long Range 802.11 WLAN at Sub 1 GHz" (PDF). Journal of ICT Standardization. 1 (1): 83–108. doi:10.13052/jicts2245-800X.125.
IEEE 802.11b-1999

IEEE 802.11b-1999 or 802.11b, is an amendment to the IEEE 802.11 wireless networking specification that extends throughput up to 11 Mbit/s using the same 2.4GHz band. A related amendment was incorporated into the IEEE 802.11-2007 standard.

802.11 is a set of IEEE standards that govern wireless networking transmission methods. They are commonly used today in their 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac versions to provide wireless connectivity in the home, office and some commercial establishments. Wi-Fi 1 is an unofficial retronym for 802.11b.

Motorola Defy

The Motorola Defy, also known as Motorola Defy A8210 & MB525, was an Android-based smartphone from Motorola. It filled a niche market segment, by being one of the few small, IP67 rated smartphones available. It was water resistant, dust resistant, and has an impact-resistant screen. The phone was launched unlocked in Germany, France, Italy, Hungary, India, Thailand, Spain, the UK, Turkey, Romania and Greece under various networks and was distributed exclusively by a number of carriers, including T-Mobile in the United States, Telus in Canada, and Telstra and Optus in Australia. An updated version of the original MB525, Defy+ (MB526) is also available.

Phase-shift keying

Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication.

Any digital modulation scheme uses a finite number of distinct signals to represent digital data. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data. This requires the receiver to be able to compare the phase of the received signal to a reference signal – such a system is termed coherent (and referred to as CPSK).

CPSK requires a complicated demodulator, because it must extract the reference wave from the received signal and keep track of it, to compare each sample to. Alternatively, the phase shift of each symbol sent can be measured with respect to the phase of the previous symbol sent. Because the symbols are encoded in the difference in phase between successive samples, this is called differential phase-shift keying (DPSK). DPSK can be significantly simpler to implement than ordinary PSK, as it is a 'non-coherent' scheme, i.e. there is no need for the demodulator to keep track of a reference wave. A trade-off is that it has more demodulation errors.

IEEE 802.11 network PHY standards
range /
PHY Protocol Release
Frequency Bandwidth Stream data rate[5] Allowable
MIMO streams
Modulation Approximate
Indoor Outdoor
(GHz) (MHz) (Mbit/s)
1-6GHz DSSS/FHSS[6] 802.11-1997 Jun 1997 2.4 22 1, 2 N/A DSSS, FHSS 20 m (66 ft) 100 m (330 ft)
HR-DSSS[6] 802.11b Sep 1999 2.4 22 1, 2, 5.5, 11 N/A DSSS 35 m (115 ft) 140 m (460 ft)
OFDM 802.11a Sep 1999 5 5/10/20 6, 9, 12, 18, 24, 36, 48, 54
(for 20MHz bandwidth,
divide by 2 and 4 for 10 and 5 MHz)
N/A OFDM 35 m (115 ft) 120 m (390 ft)
802.11j Nov 2004 4.9/5.0[D][7] ? ?
802.11p Jul 2010 5.9 ? 1,000 m (3,300 ft)[8]
802.11y Nov 2008 3.7[A] ? 5,000 m (16,000 ft)[A]
ERP-OFDM(, etc.) 802.11g Jun 2003 2.4 38 m (125 ft) 140 m (460 ft)
HT-OFDM[9] 802.11n Oct 2009 2.4/5 20 Up to 288.8[B] 4 MIMO-OFDM 70 m (230 ft) 250 m (820 ft)[10]
40 Up to 600[B]
VHT-OFDM[9] 802.11ac Dec 2013 5 20 Up to 346.8[B] 8 MIMO-OFDM 35 m (115 ft)[11] ?
40 Up to 800[B]
80 Up to 1733.2[B]
160 Up to 3466.8[B]
HE-OFDM 802.11ax Est. Dec 2019 2.4/5/6 ? Up to 10,530 (10.53 Gbit/s) ? MIMO-OFDM ? ?
mmWave DMG[12] 802.11ad Dec 2012 60 2,160 Up to 6,757[13]
(6.7 Gbit/s)
N/A OFDM, single carrier, low-power single carrier 3.3 m (11 ft)[14] ?
802.11aj Apr 2018 45/60[C] 540/1,080[15] Up to 15,000[16]
(15 Gbit/s)
4[17] OFDM, single carrier[18] ? ?
EDMG[19] 802.11ay Est. May 2020 60 8000 Up to 20,000 (20 Gbit/s)[20] 4 OFDM, single carrier 10 m (33 ft) 100 m (328 ft)
sub-1GHz IoT TVHT[21] 802.11af Feb 2014 0.054–0.79 6–8 Up to 568.9[22] 4 MIMO-OFDM ? ?
S1G[21] 802.11ah Dec 2016 0.7/0.8/0.9 1–16 Up to 8.67 (@2 MHz)[23] 4 ? ?
? 802.11ba[E] Est. Sep 2020 Other 802.11 protocol frequencies narrow-
? N/A OOK ? ?
light IR 802.11-1997 Jun 1997 ? ? 1, 2 N/A PPM ? ?
? 802.11bb Est. Jul 2021 380-5000nm band ? ? N/A ? ? ?
802.11 Standard rollups
  802.11-2007 Mar 2007 2.4, 5 Up to 54 DSSS, OFDM
802.11-2012 Mar 2012 2.4, 5 Up to 150[B] DSSS, OFDM
802.11-2016 Dec 2016 2.4, 5, 60 Up to 866.7 or 6,757[B] DSSS, OFDM
  • A1 A2 IEEE 802.11y-2008 extended operation of 802.11a to the licensed 3.7 GHz band. Increased power limits allow a range up to 5,000 m. As of 2009, it is only being licensed in the United States by the FCC.
  • B1 B2 B3 B4 B5 B6 Based on short guard interval; standard guard interval is ~10% slower. Rates vary widely based on distance, obstructions, and interference.
  • C1 For Chinese regulation.
  • D1 For Japanese regulation.
  • E1 Wake-up Radio (WUR) Operation.
802 series

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