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. This specification is marketed as Wi-Fi and has been implemented all over the world. 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.

Description

802.11b has a maximum raw data rate of 11 Mbit/s and uses the same CSMA/CA media access method defined in the original standard. Due to the CSMA/CA protocol overhead, in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mbit/s using TCP and 7.1 Mbit/s using UDP.

802.11b products appeared on the market in mid-1999, since 802.11b is a direct extension of the DSSS (Direct-sequence spread spectrum) modulation technique defined in the original standard. The Apple iBook was the first mainstream computer sold with optional 802.11b networking. Technically, the 802.11b standard uses Complementary code keying (CCK) as its modulation technique. The dramatic increase in throughput of 802.11b (compared to the original standard) along with simultaneous substantial price reductions led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.

802.11b devices suffer interference from other products operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range include: microwave ovens, Bluetooth devices, baby monitors and cordless telephones. Interference issues and user density problems within the 2.4 GHz band have become a major concern and frustration for users.

Range

802.11b is used in a point-to-multipoint configuration, wherein an access point communicates via an omnidirectional antenna with mobile clients within the range of the access point. Typical range depends on the radio frequency environment, output power and sensitivity of the receiver. Allowable bandwidth is shared across clients in discrete channels. A directional antenna focuses output power into a smaller field which increases point-to-point range. Designers of such installations who wish to remain within the law must however be careful about legal limitations on effective radiated power.

Some 802.11b cards operate at 11 Mbit/s, but scale back to 5.5, then to 2, then to 1 Mbit/s (also known as Adaptive Rate Selection) in order to decrease the rate of re-broadcasts that result from errors.

Channels and Frequencies

802.11b/g channels in 2.4 GHz band

802.11b channel to frequency map

Channel	Center Frequency	Frequency delta	Channel Width	Overlaps Channels
1	2.412 GHz	5 MHz	2.401–2.423 GHz	2-5
2	2.417 GHz	5 MHz	2.406–2.428 GHz	1,3-6
3	2.422 GHz	5 MHz	2.411–2.433 GHz	1-2,4-7
4	2.427 GHz	5 MHz	2.416–2.438 GHz	1-3,5-8
5	2.432 GHz	5 MHz	2.421–2.443 GHz	1-4,6-9
6	2.437 GHz	5 MHz	2.426–2.448 GHz	2-5,7-10
7	2.442 GHz	5 MHz	2.431–2.453 GHz	3-6,8-11
8	2.447 GHz	5 MHz	2.436–2.458 GHz	4-7,9-12
9	2.452 GHz	5 MHz	2.441–2.463 GHz	5-8,10-13
10	2.457 GHz	5 MHz	2.446–2.468 GHz	6-9,11-13
11	2.462 GHz	5 MHz	2.451–2.473 GHz	7-10,12-13
12	2.467 GHz	5 MHz	2.456–2.478 GHz	8-11,13-14
13	2.472 GHz	5 MHz	2.461–2.483 GHz	9-12, 14
14	2.484 GHz	12 MHz	2.473–2.495 GHz	12-13

Note: Channel 14 is only allowed in Japan, Channels 12 & 13 are allowed in most parts of the world, except the USA, where only Channels 1 to 11 are legal to use. More information can be found in the List of WLAN channels.

See also

• IEEE 802.11
• IEEE 802.11g-2003
• Wi-Fi
• List of WLAN channels

802.11 network PHY standards
802.11 protocol	Release date	Fre- quency	Band- width	Stream data rate	Allowable MIMO streams	Modulation	Approximate range
							Indoor		Outdoor
		(GHz)	(MHz)	(Mbit/s)			(m)	(ft)	(m)	(ft)
802.11-1997	Jun 1997	2.4	22	1, 2	N/A	DSSS, FHSS	20	66	100	330
a	Sep 1999	5	20	6, 9, 12, 18, 24, 36, 48, 54	N/A	OFDM	35	115	120	390
		3.7					—	—	5,000	16,000
b	Sep 1999	2.4	22	1, 2, 5.5, 11	N/A	DSSS	35	115	140	460
g	Jun 2003	2.4	20	6, 9, 12, 18, 24, 36, 48, 54	N/A	OFDM	38	125	140	460
n	Oct 2009	2.4/5	20	7.2, 14.4, 21.7, 28.9, 43.3, 57.8, 65, 72.2 (6.5, 13, 19.5, 26, 39, 52, 58.5, 65)	4	MIMO-OFDM	70	230	250	820
			40	15, 30, 45, 60, 90, 120, 135, 150 (13.5, 27, 40.5, 54, 81, 108, 121.5, 135)			70	230	250	820
ac	Dec 2013	5	20	7.2, 14.4, 21.7, 28.9, 43.3, 57.8, 65, 72.2, 86.7, 96.3 (6.5, 13, 19.5, 26, 39, 52, 58.5, 65, 78, 86.7)	8		35	115
			40	15, 30, 45, 60, 90, 120, 135, 150, 180, 200 (13.5, 27, 40.5, 54, 81, 108, 121.5, 135, 162, 180)			35	115
			80	32.5, 65, 97.5, 130, 195, 260, 292.5, 325, 390, 433.3 (29.2, 58.5, 87.8, 117, 175.5, 234, 263.2, 292.5, 351, 390)			35	115
			160	65, 130, 195, 260, 390, 520, 585, 650, 780, 866.7 (58.5, 117, 175.5, 234, 351, 468, 702, 780)			35	115
ad	Dec 2012	60	2,160	Up to 6,912 (6.75 Gbit/s)	N/A	OFDM, single carrier, low-power single carrier	60	200	100	300
ah	Est. 2016	0.9
aj	Est. 2016	45/60
ax	Est. 2019	2.4/5				MIMO-OFDM
ay	2017	60	8000	Up to 100,000 (100 Gbit/s)	4	OFDM, single carrier,	60	200	1000	3000
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 Assumes short guard interval (SGI) enabled. C1 C2 C3 C4 C5 C6 Assumes short guard interval (SGI) disabled.