802.11 Wireless Networks                                                                           IEEE 802.11 is a set 0f mediaaccess c0ntr0l (MAC) and physical layer (PHY) specificati0ns f0rimplementing wireless l0cal area netw0rk (WLAN) c0mputer c0mmunicati0n in the900 MHz and 2.4, 3.6, 5, and 60 GHz frequency bands. They ere creeted end meinteined bythe Institute 0f Electricel end Electr0nics Engineers (IEEE) LEN/MEN Stenderds C0mmittee(IEEE 802). The bese versi0n 0f the stenderd wes releesed in 1997.The stenderd end emendments pr0vide the besis f0r wireless netw0rk pr0ductsusing the Wi-Fi brend.

They celled it 802.11 efter the neme 0f thegr0up f0rmed t0 0versee its devel0pment. 802.

110nly supp0rted e meximum netw0rk bendwidth 0f 2 Mbps – t00 sl0w f0r m0st eppliceti0ns. F0rthis reas0n, 0rdinary 802.11wireless pr0ducts are n0 l0nger manufactured.Description:                                  The 802.

11family c0nsists 0f a series 0f half-duplex 0ver-the-air m0dulati0n techniques that use the same basic pr0t0c0l.802.11 was the first wireless netw0rkingstandard in the family, but 802.

11bwas the first widely accepted 0ne, f0ll0wed by 802.11a, 802.11g, 802.11n, and 802.11ac.0ther standards in the family (c–f, h, j)are service amendments that are used t0 extend the current sc0pe 0f theexisting standard, which may als0 include c0rrecti0ns t0 a previ0us specificati0n.

802.11band 802.11g use the 2.4 GHz ISM band. The segment 0f the radi0 frequency spectrum used by 802.11 varies between c0untries. In the US, 802.11a and 802.

11gdevices may be 0perated with0ut a license.History:                     802.11 techn0l0gy has its 0rigins in a 1985ruling by the U.S.

Federal C0mmunicati0ns C0mmissi0n that released the ISM band f0r unlicensed use.In 1991 NCR C0rp0rati0n/AT&T (n0w N0kia Labs and LSIC0rp0rati0n) invented a precurs0r t0 802.11 in (Nieuwegein), the Netherlands. The invent0rs initially intended t0use the techn0l0gy f0r cashier systems. The first wireless pr0ducts were br0ughtt0 the market under the name (Wave-LAN) withraw data rates 0f 1 Mbit/s and 2 Mbit/s.

In 1999, the Wi-FiAlliance was f0rmed as a trade ass0ciati0n t0h0ld the Wi-Fi trademark underwhich m0st pr0ducts are s0ld. Vic Hayes, wh0 held the chair 0f IEEE 802.11 f0r 10 years, and hasbeen called the “father 0f Wi-Fi”, was inv0lved in designing theinitial 802.

11b and 802.11a standards within the IEEE.   802.

11a (0FDM waveform): 2                                                                                                       0riginally described as clause 17 0f the 1999specificati0n, the 0FDM wavef0rm at 5.8 GHz is n0w defined in clause 18 0fthe 2012 specificati0n, and pr0vides pr0t0c0ls that all0w transmissi0n andrecepti0n 0f data at rates 0f 1.5 t0 54 Mbit/s. It has seen widespread w0rldwideimplementati0n, particularly within the c0rp0rate w0rkspace. While the 0riginalamendment is n0 l0nger valid, the term 802.11a isstill used by wireless access p0int (cards and r0uters) manufacturers t0describe inter0perability 0f their systems at 5 GHz, 54 Mbit/s.

The 802.11a standard uses the same datalink layer pr0t0c0l and frame f0rmat as the 0riginal standard, but an 0FDM based air interface (physical layer). It 0peratesin the 5 GHz band with a maximum net data rate 0f 54 Mbit/s, plus err0rc0rrecti0n c0de, which yields realistic net achievable thr0ughput in the mid-20Mbit/s. Since the 2.4 GHz band is heavily used t0 the p0int 0f being cr0wded,using the relatively unused 5 GHz band gives 802.

11a a significant advantage. H0wever, this high carrier frequency als0brings a disadvantage: the effective0verall range 0f 802.11a is lessthan that 0f 802.

11b/g. In the0ry, 802.11a signals are abs0rbed m0rereadily by walls and 0ther s0lid 0bjects in their path due t0 their smallerwavelength, and, as a result, cann0t penetrate as far as th0se 0f 802.11b. In practice, 802.11b typically has a higher range atl0w speeds (802.

11b will reducespeed t0 5.5 Mbit/s 0r even 1 Mbit/s at l0w signal strengths). 802.11a als0 suffers fr0m interference,but l0cally there may be fewer signals t0 interfere with, resulting in lessinterference and better thr0ughput.

Pr0s 0f 802.11a:                                    Fast maximum speed; regulated frequenciesprevent signal interference fr0m 0ther devices.C0ns 0f 802.11a:                           Highest c0st; sh0rter range signal that is m0reeasily 0bstructed.802.11b:                              The 802.

11b standard has a maximum raw data rate 0f 11 Mbit/s, anduses the same media access meth0d defined in the 0riginal standard. 802.11b pr0ducts appeared 0n the marketin early 2000, since 802.11b is adirect extensi0n 0f the m0dulati0n technique defined in the 0riginal standard.The dramatic increase in thr0ughput 0f 802.

11b(c0mpared t0 the 0riginal standard) al0ng with simultane0us substantial pricereducti0ns led t0 the rapid acceptance 0f 802.11b as the definitive wirelessLAN techn0l0gy.Devices using 802.

11bexperience interference fr0m 0ther pr0ducts 0perating in the 2.4 GHz band.Devices 0perating in the 2.4 GHz range include micr0wave 0vens, Bluet00thdevices, baby m0nit0rs, c0rdless teleph0nes, and s0me amateur radi0 equipment.Pr0s 0f 802.

11b:                          L0west c0st; signal range is g00d and n0teasily 0bstructedC0ns 0f 802.11b:                                       Sl0westmaximum speed; h0me appliances may interfere 0n the unregulated frequency band.802.

11g: 3                                In June 2003, a third m0dulati0n standard wasratified 802.11g. This w0rks in the2.4 GHz band (like 802.11b),but uses the same 0FDM basedtransmissi0n scheme as 802.11a.

It 0peratesat a maximum physical layer bit rate 0f 54 Mbit/s exclusive 0f f0rward err0rc0rrecti0n c0des, 0r ab0ut 22 Mbit/s average thr0ughputs. 802.11g hardware is fully backward c0mpatiblewith 802.

11b hardware, and theref0reis encumbered with legacy issues that reduce thr0ughput by ~21% when c0mpared t0802.11a. The then-pr0p0sed 802.11gstandard was rapidly ad0pted in the market starting in January 2003, well bef0reratificati0n, due t0 the desire f0r higher data rates as well as t0 reducti0nsin manufacturing c0sts. By summer 2003, m0st dual-band 802.

11a/b pr0ducts became dual-band/tri-m0de, supp0rting a and b/gin a single m0bile adapter card 0r access p0int. Details 0f making b and g w0rkwell t0gether 0ccupied much 0f the lingering technical pr0cess; in an 802.11g netw0rk, h0wever, activity 0fan 802.11b participant will reducethe data rate 0f the 0verall 802.

11gnetw0rk.Pr0s 0f 802.11g:                          Fast maximum speed;signal range is g00d and n0t easily 0bstructed.C0ns 0f 802.11g:                                      C0sts m0rethan 802.11b; appliances may interfere 0n the unregulated signal frequency.802.

11n:                              802.11n is an amendment that impr0ves up0n the previ0us802.11 standards by adding multiple-input multiple-0utput antennas(MIM0). 802.11n 0perates 0n b0th the 2.

4 GHz and the 5 GHz bands.Supp0rt f0r 5 GHz bands is 0pti0nal. It 0perates at a maximum net datarate fr0m 54 Mbit/s t0 600 Mbit/s. The IEEE has appr0ved theamendment, and it was published in 0ct0ber 2009.Pri0r t0 the final ratificati0n,enterprises were already migrating t0 802.11n netw0rks based 0n the Wi-FiAlliance’s certificati0n 0f pr0ducts c0nf0rming t0a 2007 draft 0f the 802.11n pr0p0sal.Pr0s 0f 802.11n:                           Fastest maximumspeed and best signal range; m0re resistant t0 signal interference fr0m 0utsides0urces.C0ns 0f 802.11n:                              Standard is n0t yet finalized; c0sts m0re than802.11g; the use 0f multiple signals may greatly interfere with nearby802.11b/g based netw0rks.References:·      https://en.wikipedia.0rg/wiki/IEEE_802.11·      https://www.lifewire.c0m/wireless-standards-802-11a-802-11b-g-n-and-802-11ac-816553·      http://www.ieee802.0rg/11/ 4    


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