IEEE 802.11g-2003

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Short description: Wireless networking standard

IEEE 802.11g-2003 or 802.11g is an amendment to the IEEE 802.11 specification that operates in the 2.4 GHz microwave band. The standard has extended link rate to up to 54 Mbit/s using the same 20 MHz bandwidth as 802.11b uses to achieve 11 Mbit/s. 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, 802.11ac and 802.11ax 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.

Descriptions

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[1] 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.[1] 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 by RTS/CTS transmissions and a "back off" mechanism.[2] Some 802.11g routers employ a back-compatible mode for 802.11b clients called 54g LRS (Limited Rate Support).[3]

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 better modulation from 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.[4]

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

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 to side lobes exists, though it is considerably weaker.

Channels and frequencies

Graphical representation of Wireless LAN channels in 2.4 GHz band. Channels 12 and 13 are customarily unused in the United States. As a result, the usual 20 MHz allocation becomes 1/6/11, the same as 11b.
IEEE 802.11g channel to frequency map [5]
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 22MHz width, while 802.11g only requires 20MHz (the actual occupied bandwidth is even lower, 16.25 MHz). As a result, such overlaps have minimal performance implications.

Comparison

IEEE 802.11 network PHY standards
Frequency
range,
or type 		PHY Protocol Release
date[6] 		Frequency Bandwidth Stream data rate[7] Allowable
MIMO streams 		Modulation Approximate
range[citation needed]
Indoor Outdoor
(GHz) (MHz) (Mbit/s)
1–6 GHz DSSS/FHSS[8] 802.11-1997 Jun 1997 2.4 22 1, 2 N/A DSSS, FHSS 20 m (66 ft) 100 m (330 ft)
HR-DSSS[8] 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 20 MHz 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][9][failed verification] ? ?
802.11p Jul 2010 5.9 ? 1,000 m (3,300 ft)[10]
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[11] 802.11n Oct 2009 2.4/5 20 Up to 288.8[B] 4 MIMO-OFDM 70 m (230 ft) 250 m (820 ft)[12][failed verification]
40 Up to 600[B]
VHT-OFDM[11] 802.11ac Dec 2013 5 20 Up to 346.8[B] 8 MIMO-OFDM 35 m (115 ft)[13] ?
40 Up to 800[B]
80 Up to 1733.2[B]
160 Up to 3466.8[B]
HE-OFDM 802.11ax September 2019 [14] 2.4/5/6 20 Up to 1147[F] 8 MIMO-OFDM 30 m (98 ft) 120 m (390 ft) [G]
40 Up to 2294[F]
80 Up to 4804[F]
80+80 Up to 9608[F]
mmWave DMG[15] 802.11ad Dec 2012 60 2,160 Up to 6,757[16]
(6.7 Gbit/s) 		N/A OFDM, single carrier, low-power single carrier 3.3 m (11 ft)[17] ?
802.11aj Apr 2018 45/60[C] 540/1,080[18] Up to 15,000[19]
(15 Gbit/s) 		4[20] OFDM, single carrier[20] ? ?
EDMG[21] 802.11ay Est. May 2020 60 8000 Up to 20,000 (20 Gbit/s)[22] 4 OFDM, single carrier 10 m (33 ft) 100 m (328 ft)
Sub-1 GHz IoT TVHT[23] 802.11af Feb 2014 0.054–0.79 6–8 Up to 568.9[24] 4 MIMO-OFDM ? ?
S1G[23] 802.11ah Dec 2016 0.7/0.8/0.9 1–16 Up to 8.67 (@2 MHz)[25] 4 ? ?
2.4 GHz, 5 GHz WUR 802.11ba[E] Est. Sep 2020 2.4/5 4.06 0.0625, 0.25 (62.5 kbit/s, 250 kbit/s) N/A OOK (Multi-carrier OOK) ? ?
Light (Li-Fi) IR 802.11-1997 Jun 1997 ? ? 1, 2 N/A PPM ? ?
? 802.11bb Est. Jul 2021 60000-790000 ? ? 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.
  • F1 F2 F3 F4 For single-user cases only, based on default guard interval which is 0.8 micro seconds. Since multi-user via OFDMA has become available for 802.11ax, these may decrease. Also, these theoretical values depend on the link distance, whether the link is line-of-sight or not, interferences and the multi-path components in the environment.
  • G1 The default guard interval is 0.8 micro seconds. However, 802.11ax extended the maximum available guard interval to 3.2 micro seconds, in order to support Outdoor communications, where the maximum possible propagation delay is larger compared to Indoor environments.

See also

Notes

References

  1. ↑ 1.0 1.1 Jun, Jangeun; Peddabachagari, Pushkin; Sichitiu, Mihail (2003). "Theoretical Maximum Throughput of IEEE 802.11 and its Applications". Proceedings of the Second IEEE International Symposium on Network Computing and Applications. http://morse.colorado.edu/~timxb/5520/ho/MaxThru802112003.pdf. 
  2. ↑ "802.11b and 802.11g in same channel" (in en). 9 January 2009. https://community.cisco.com/t5/wireless/802-11b-and-802-11g-in-same-channel/td-p/1167829. 
  3. ↑ "USRobotics Wireless ADSL2+ Router: User Guide". https://support.usr.com/support/9114/9114-ug/wireless_advanced.html. "54g LRS (Limited Rate Support) is intended to support "legacy" (802.11b) clients that can't deal with access points which advertise supported rates in their beacon frames other than the original 802.11's 1 and 2 Mbps rates. [...] 54g™ protection: If you set this option as Automatic, the router will use RTS/CTS to improve the 802.11g performance in 802.11 mixed environments." 
  4. ↑ Van Nee, Richard; Awater, Geert; Morikura, Masahiro; Takanashi, Hitoshi; Webster, Mark; Halford, Karen (December 1999). "New High Rate Wireless LAN Standards". IEEE Communications Magazine. http://www.jorianvannee.nl/wifi. 
  5. ↑ [1][yes|permanent dead link|dead link}}]
  6. ↑ "Official IEEE 802.11 working group project timelines". January 26, 2017. http://grouper.ieee.org/groups/802/11/Reports/802.11_Timelines.htm. Retrieved 2017-02-12. 
  7. ↑ "Wi-Fi CERTIFIED n: Longer-Range, Faster-Throughput, Multimedia-Grade Wi-Fi® Networks". Wi-Fi Alliance. September 2009. http://www.wi-fi.org/register.php?file=wp_Wi-Fi_CERTIFIED_n_Industry.pdf. [|permanent dead link|dead link}}]
  8. ↑ 8.0 8.1 Banerji, Sourangsu; Chowdhury, Rahul Singha. "On IEEE 802.11: Wireless LAN Technology". arXiv:1307.2661.
  9. ↑ "The complete family of wireless LAN standards: 802.11 a, b, g, j, n". https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_news_from_rs/183/n183_lan.pdf. 
  10. ↑ Abdelgader, Abdeldime M.S.; Wu, Lenan (2014). "The Physical Layer of the IEEE 802.11p WAVE Communication Standard: The Specifications and Challenges". World Congress on Engineering and Computer Science. http://www.iaeng.org/publication/WCECS2014/WCECS2014_pp691-698.pdf. 
  11. ↑ 11.0 11.1 Wi-Fi Capacity Analysis for 802.11ac and 802.11n: Theory & Practice
  12. ↑ Belanger, Phil; Biba, Ken (2007-05-31). "802.11n Delivers Better Range". Wi-Fi Planet. http://www.wi-fiplanet.com/tutorials/article.php/3680781. 
  13. ↑ "IEEE 802.11ac: What Does it Mean for Test?". LitePoint. October 2013. http://litepoint.com/whitepaper/80211ac_Whitepaper.pdf. 
  14. ↑ "Wi-Fi 6 Routers: What You Can Buy Now (and Soon) | Tom's Guide". https://www.tomsguide.com/amp/us/best-wifi-6-routers,review-6115.html. 
  15. ↑ "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)". IEEE Std 802.11aj-2018. April 2018. doi:10.1109/IEEESTD.2018.8345727. https://ieeexplore.ieee.org/document/8345727. 
  16. ↑ "802.11ad - WLAN at 60 GHz: A Technology Introduction". Rohde & Schwarz GmbH. November 21, 2013. p. 14. https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ma220/1MA220_2e_WLAN_11ad_WP.pdf. 
  17. ↑ "Connect802 - 802.11ac Discussion". https://www.connect802.com/802-11ac-discussion. 
  18. ↑ "Understanding IEEE 802.11ad Physical Layer and Measurement Challenges". https://www.keysight.com/upload/cmc_upload/All/22May2014Webcast.pdf. 
  19. ↑ "802.11aj Press Release". https://mentor.ieee.org/802.11/dcn/18/11-18-0698-01-0000-802-11aj-press-release.docx. 
  20. ↑ 20.0 20.1 Hong, Wei; He, Shiwen; Wang, Haiming; Yang, Guangqi; Huang, Yongming; Chen, Jixing; Zhou, Jianyi; Zhu, Xiaowei et al. (2018). "An Overview of China Millimeter-Wave Multiple Gigabit Wireless Local Area Network System". IEICE Transactions on Communications E101.B (2): 262-276. doi:10.1587/transcom.2017ISI0004. https://www.jstage.jst.go.jp/article/transcom/E101.B/2/E101.B_2017ISI0004/_pdf. 
  21. ↑ "IEEE 802.11ay: 1st real standard for Broadband Wireless Access (BWA) via mmWave – Technology Blog". https://techblog.comsoc.org/2018/06/15/ieee-802-11ay-1st-real-standard-for-broadband-wireless-access-bwa-via-mmwave/. 
  22. ↑ Sun, Rob; Xin, Yan; Aboul-Maged, Osama; Calcev, George; Wang, Lei; Au, Edward; Cariou, Laurent; Cordeiro, Carlos et al.. "P802.11 Wireless LANs". IEEE. pp. 2,3. Archived from the original. Error: If you specify |archiveurl=, you must also specify |archivedate=. https://web.archive.org/web/20171206183820/https://mentor.ieee.org/802.11/dcn/15/11-15-1074-00-00ay-11ay-functional-requirements.docx. Retrieved December 6, 2017. 
  23. ↑ 23.0 23.1 "802.11 Alternate PHYs A whitepaper by Ayman Mukaddam". https://www.cwnp.com/uploads/802-11alternatephyswhitepaper.pdf. 
  24. ↑ Lee, Wookbong; Kwak, Jin-Sam; Kafle, Padam; Tingleff, Jens; Yucek, Tevfik; Porat, Ron; Erceg, Vinko; Lan, Zhou et al. (2012-07-10). "TGaf PHY proposal". IEEE P802.11. https://mentor.ieee.org/802.11/dcn/12/11-12-0809-05-00af-tgaf-phy-proposal.docx. Retrieved 2013-12-29. 
  25. ↑ Sun, Weiping; Choi, Munhwan; Choi, Sunghyun (July 2013). "IEEE 802.11ah: A Long Range 802.11 WLAN at Sub 1 GHz". Journal of ICT Standardization 1 (1): 83–108. doi:10.13052/jicts2245-800X.115. http://riverpublishers.com/journal/journal_articles/RP_Journal_2245-800X_115.pdf. 

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