Please help improve this article by expanding it. Further information might be found on the talk page. (September 2007)

IEEE 802.11b-1999 or 802.11b, is an amendment to the IEEE 802.11 specification that extended throughput up to 11 Mbit/s using the same 2.4 GHz band. This specification under the marketing name of Wi-Fi has been implemented all over the world. The amendment has been incorporated into the published 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, and 802.11g versions to provide wireless connectivity in the home, office and some commercial establishments.

Contents 1 Description 2 Range 3 Channels and Frequencies 4 See also 5 References

[edit] 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 early 2000, since 802.11b is a direct extension of the DSSS (Direct-sequence spread spectrum) modulation technique defined in the original standard. 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.

[edit] Range

802.11b is used in a point-to-multipoint configuration, wherein an access point communicates via an omni-directional antenna with one or more nomadic or mobile clients that are located in a coverage area around the access point. Typical indoor range is 30 m (100 ft) at 11 Mbit/s and 90 m (300 ft) at 1 Mbit/s. The overall bandwidth is dynamically demand shared across all the users on a channel. With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to 8 kilometers (5 miles) although some report success at ranges up to 80–120 km (50–75 miles) where line of sight can be established. This is usually done in place of costly leased lines or very cumbersome microwave communications equipment. Designers of such installations who wish to remain within the law must however be careful about legal limitations on effective radiated power.^[1]

802.11b cards can operate at 11 Mbit/s, but will scale back to 5.5, then 2, then 1 Mbit/s (also known as Adaptive Rate Selection), if signal quality becomes an issue.

[edit] Channels and Frequencies

802.11b/g channel to frequency map ^[2]

Channel	Center Frequency	Channel Width	Overlaps 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	6,7,8,9,11,12,13,14
11	2.462 GHz	2.451 GHz - 2.473 GHz	7,8,9,10,12,13,14
12	2.467 GHz	2.456 GHz - 2.468 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	10,11,12,13

Note: Not all channels are legal to use in all countries.

[edit] See also

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

802.11 network standards v • d • e
802.11 Protocol	Release[3]	Freq. (GHz)	Bandwidth (MHz)	Data rate per stream (Mbit/s)[4]	Typ throughput (Mbit/s) [citation needed]	Allowable MIMO streams	Modulation	Approximate indoor range[citation needed] (m)	Approximate Outdoor range[citation needed] (m)
–	Jun 1997	2.4	20	1, 2	0.9	1	DSSS	20	100
a	Sep 1999	5 3.7[y]	20	6, 9, 12, 18, 24, 36, 48, 54	23	1	OFDM	35	120 5000[y]
b	Sep 1999	2.4	20	1, 2, 5.5, 11	4.3	1	DSSS	38	140
g	Jun 2003	2.4	20	1, 2, 6, 9, 12, 18, 24, 36, 48, 54	19	1	OFDM, DSSS	38	140
n	Oct 2009	2.4/5	20	7.2, 14.4, 21.7, 28.9, 43.3, 57.8, 65, 72.2[z]	30-130[5][6]	4	OFDM	~70	~250[7]
			40	15, 30, 45, 60, 90, 120, 135, 150[z]
y  IEEE 802.11y-2008 extended operation of 802.11a to the licensed 3.7 GHz band. Increased power limits allow for a range up 5000m. As of 2009[update], it is only being licensed in the United States by the FCC. z  Assumes Short Guard interval (SGI) enabled, otherwise reduce each data rate by 10%.

[edit] References

v • d • e IEEE Standards 488 · 754 (1985,revs) · 829 · 1003 · 1014-1987 · 1076 · 1149.1 · 1164 · 1219 · 12207 · 1275 · 1284 · 1394 · 1451 · 1471 · 1516 · 1541-2002 · 1547 · 1584 · 1603 · 1613 · 1667 · 1675-2008 · 1900.4 · 854-1987 · SCC41 · 11073 802 series 802 · 802.1 · 802.2 · 802.3 · 802.4 · 802.5 · 802.6 · 802.7 · 802.8 · 802.9 · 802.10 · 802.11 (a b d e g h i j k n p r y) · 802.12 · 802.15 · 802.15.4-2006 · 802.15.4a · 802.16 · 802.21 · 802.22 P series P1363 · P1619 · P1801 · P1900 · P1901 · P2030 See also: IEEE Standards Association · Category:IEEE standards