IEEE 802.11 (legacy mode)

IEEE 802.11 (legacy mode) – or more correctly IEEE 802.11-1997 or IEEE 802.11-1999 – refers to the original version of the IEEE 802.11 wireless networking standard released in 1997 and clarified in 1999. Most of the protocols described by this early version are rarely used today.

Wi-Fi generations

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Gen.[1]	Vi- sual	IEEE standard	Adopt.	Link rate (Mbit/s)	RF (GHz)
Wi-Fi	—	802.11	1997	1–2	2.4
Wi-Fi 1	—	802.11b	1999	1–11	2.4
Wi-Fi 2	—	802.11a	1999	6–54	05
Wi-Fi 3	—	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	005[a]
Wi-Fi 6		802.11ax	2021	0.4–9608	2.4, 5
Wi-Fi 6E[b]					6
Wi-Fi 7		802.11be	2024[c]	0.4–23,059	2.4, 5, 6
Wi-Fi 8[2][3]	—	802.11bn		100,000	2.4, 5, 6

Description

It specified two raw data rates of 1 and 2 megabits per second (Mbit/s) to be transmitted via infrared (IR) signals or by either frequency hopping or direct-sequence spread spectrum (DSSS) in the Industrial Scientific Medical frequency band at 2.4 GHz. IR remained a part of the standard until IEEE 802.11-2016, but was never implemented.^{[citation needed]}

The original standard also defines carrier sense 0 access with collision avoidance (CSMA/CA) as the medium access method. A significant percentage of the available raw channel capacity is sacrificed (via the CSMA/CA mechanisms) in order to improve the reliability of data transmissions under diverse and adverse environmental conditions.

IEEE 802.11-1999 also introduced the binary time unit TU defined as 1024 μs.^[4]

At least seven different, somewhat-interoperable, commercial products appeared using the original specification, from companies like Alvarion (PRO.11 and BreezeAccess-II), BreezeCom, Digital / Cabletron (RoamAbout), Lucent, Netwave Technologies (AirSurfer Plus and AirSurfer Pro), Symbol Technologies (Spectrum24), and Proxim Wireless (OpenAir and Rangelan2). A weakness of this original specification was that it offered so many choices that interoperability was sometimes challenging to realize. It is really more of a "beta specification" than a rigid specification, initially allowing individual product vendors the flexibility to differentiate their products but with little to no inter-vendor interoperability.

The DSSS version of legacy 802.11 was rapidly supplemented (and popularized) by the 802.11b amendment in 1999, which increased the bit rate to 11 Mbit/s. Widespread adoption of 802.11 networks only occurred after the release of 802.11b which resulted in multiple interoperable products becoming available from multiple vendors. Consequently, comparatively few networks were implemented on the 802.11-1997 standard.^{[citation needed]}

Comparison

v t e 802.11 network standards
Frequency range, or type	PHY	Protocol	Release date[5]	Freq­uency	Bandwidth	Stream data rate[6]	Max. MIMO streams	Modulation	Approx. range
									In­door	Out­door
				(GHz)	(MHz)	(Mbit/s)
1–7 GHz	DSSS[7], FHSS[A]	802.11-1997	June 1997	2.4	22	1, 2	—	DSSS, FHSS[A]	20 m (66 ft)	100 m (330 ft)
	HR/DSSS[7]	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 20 MHz bandwidth, divide by 2 and 4 for 10 and 5 MHz)	—	OFDM	35 m (115 ft)	120 m (390 ft)
		802.11j	November 2004	4.9, 5.0 [B][8]					?	?
		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)[9]
		802.11bd	December 2022	5.9, 60					500 m	1,000 m (3,300 ft)
	ERP-OFDM[10]	802.11g	June 2003	2.4					38 m (125 ft)	140 m (460 ft)
	HT-OFDM[11]	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)[12]
					40	Up to 600[D]
	VHT-OFDM[11]	802.11ac (Wi-Fi 5)	December 2013	5	20	Up to 693[D]	8	DL MU-MIMO OFDM (256-QAM)	35 m (115 ft)[13]	?
					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-MIMO OFDMA (1024-QAM)	30 m (98 ft)	120 m (390 ft)[F]
					40	Up to 2294[E]
					80	Up to 5500[E]
					80+80	Up to 11 000[E]
	EHT-OFDMA	802.11be (Wi-Fi 7)	Sep 2024	2.4, 5, 6	80	Up to 5764[E]	8	UL/DL MU-MIMO OFDMA (4096-QAM)	30 m (98 ft)	120 m (390 ft)[F]
					160 (80+80)	Up to 11 500[E]
					240 (160+80)	Up to 14 282[E]
					320 (160+160)	Up to 23 059[E]
	UHR	802.11bn (Wi-Fi 8)	May 2028 (est.)	2.4, 5, 6, 42, 60, 71	320	Up to 100000 (100 Gbit/s)	16	Multi-link MU-MIMO OFDM (8192-QAM)	?	?
	WUR[G]	802.11ba	October 2021	2.4, 5	4, 20	0.0625, 0.25 (62.5 kbit/s, 250 kbit/s)	—	OOK (multi-carrier OOK)	?	?
mmWave (WiGig)	DMG[14]	802.11ad	December 2012	60	2160 (2.16 GHz)	Up to 8085[15] (8 Gbit/s)	—	OFDM,[A] single carrier, low-power single carrier[A]	3.3 m (11 ft)[16]	?
		802.11aj	April 2018	60[H]	1080[17]	Up to 3754 (3.75 Gbit/s)	—	single carrier, low-power single carrier[A]	?	?
	CMMG	802.11aj	April 2018	45[H]	540, 1080	Up to 15015[18] (15 Gbit/s)	4[19]	OFDM, single carrier	?	?
	EDMG[20]	802.11ay	July 2021	60	Up to 8640 (8.64 GHz)	Up to 303336[21] (303 Gbit/s)	8	OFDM, single carrier	10 m (33 ft)	100 m (328 ft)
Sub 1 GHz (IoT)	TVHT[22]	802.11af	February 2014	0.054– 0.79	6, 7, 8	Up to 568.9[23]	4	MIMO-OFDM	?	?
	S1G[22]	802.11ah	May 2017	0.7, 0.8, 0.9	1–16	Up to 8.67[24] (@2 MHz)	4		?	?
Light (Li-Fi)	LC (VLC/OWC)	802.11bb	December 2023 (est.)	800–1000 nm	20	Up to 9.6 Gbit/s	—	O-OFDM	?	?
	IR[A] (IrDA)	802.11-1997	June 1997	850–900 nm	?	1, 2	—	PPM[A]	?	?
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
		802.11-2024 (802.11me)	September 2024	2.4, 5, 6, 60		Up to 9608 or 303336		DSSS, OFDM
This is obsolete, and support for this might be subject to removal in a future revision of the standard For Japanese regulation. 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[update], it is only being licensed in the United States by the FCC. Based on short guard interval; standard guard interval is ~10% slower. Rates vary widely based on distance, obstructions, and interference. For single-user cases only, based on default guard interval which is 0.8 microseconds. 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. The default guard interval is 0.8 microseconds. However, 802.11ax extended the maximum available guard interval to 3.2 microseconds, in order to support Outdoor communications, where the maximum possible propagation delay is larger compared to Indoor environments. Wake-up Radio (WUR) Operation. For Chinese regulation.

Notes

1. 802.11ac only specifies operation in the 5 GHz band. Operation in the 2.4 GHz band is specified by 802.11n.
2. Wi-Fi 6E is the industry name that identifies Wi-Fi devices that operate in 6 GHz. Wi-Fi 6E offers the features and capabilities of Wi-Fi 6 extended into the 6 GHz band.
3. The Wi-Fi Alliance began certifying Wi-Fi 7 devices in 2024, but as of January 2025^[update] the IEEE standard 802.11be is yet to be ratified.