wifi what are the gens

[semi colon]

can someone explain what the difference between a b n g and ac are and something about there speeds 

[juretrn]

Speed, range, security, frequencies.

http://en.m.wikipedia.org/wiki/IEEE_802.11

[Wyre]

802.11-1997 (802.11 legacy)

 

Main article: IEEE 802.11 (legacy mode)

The original version of the standard IEEE 802.11 was released in 1997 and clarified in 1999, but is today obsolete. It specified two net bit rates of 1 or 2 megabits per second (Mbit/s), plus forward error correction code. It specified three alternative physical layertechnologies: diffuse infrared operating at 1 Mbit/s; frequency-hopping spread spectrum operating at 1 Mbit/s or 2 Mbit/s; and direct-sequence spread spectrum operating at 1 Mbit/s or 2 Mbit/s. The latter two radio technologies used microwave transmission over theIndustrial Scientific Medical frequency band at 2.4 GHz. Some earlier WLAN technologies used lower frequencies, such as the U.S. 900 MHz ISM band.

Legacy 802.11 with direct-sequence spread spectrum was rapidly supplanted and popularized by 802.11b.

 

 

802.11a (OFDM Waveform)

 

Main article: IEEE 802.11a-1999

Originally described as clause 17 of the 1999 specification, the OFDM waveform at 5.8 GHz is now defined in clause 18 of the 2012 specification and provides protocols that allow transmission and reception of data at rates of 1.5 to 54Mbit/s. It has seen widespread worldwide implementation, particularly within the corporate workspace. While the original amendment is no longer valid, the term "802.11a" is still used by wireless access point (cards and routers) manufacturers to describe interoperability of their systems at 5.8 GHz, 54Mbit/s.

The 802.11a standard uses the same data link layer protocol and frame format as the original standard, but an OFDM based air interface (physical layer). It operates in the 5 GHz band with a maximum net data rate of 54 Mbit/s, plus error correction code, which yields realistic net achievable throughput in the mid-20 Mbit/s.[10]

Since the 2.4 GHz band is heavily used to the point of being crowded, using the relatively unused 5 GHz band gives 802.11a a significant advantage. However, this high carrier frequency also brings a disadvantage: the effective overall range of 802.11a is less than that of 802.11b/g. In theory, 802.11a signals are absorbed more readily by walls and other solid objects in their path due to their smaller wavelength and, as a result, cannot penetrate as far as those of 802.11b. In practice, 802.11b typically has a higher range at low speeds (802.11b will reduce speed to 5.5 Mbit/s or even 1 Mbit/s at low signal strengths). 802.11a also suffers from interference,[11] but locally there may be fewer signals to interfere with, resulting in less interference and better throughput.

 

 

802.11b

 

Main article: IEEE 802.11b-1999

The 802.11b standard has a maximum raw data rate of 11 Mbit/s and uses the same media access method defined in the original standard. 802.11b products appeared on the market in early 2000, since 802.11b is a direct extension of the modulation technique defined in the original standard. 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.

Devices using 802.11b experience 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, cordless telephones and some amateur radio equipment.

 

 

802.11g

 

Main article: IEEE 802.11g-2003

In June 2003, a third modulation standard was ratified: 802.11g. This works in the 2.4 GHz band (like 802.11b), but uses the same OFDM based transmission scheme as 802.11a. It operates at a maximum physical layer bit rate of 54 Mbit/s exclusive of forward error correction codes, or about 22 Mbit/s average throughput.[12] 802.11g hardware is fully backward compatible with 802.11b hardware and therefore is encumbered with legacy issues that reduce throughput when compared to 802.11a by ~21%.[citation needed]

The then-proposed 802.11g standard was rapidly adopted by consumers starting in January 2003, well before ratification, due to the desire for higher data rates as well as to reductions in manufacturing costs. By summer 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. Details of making b and g work well together occupied much of the lingering technical process; in an 802.11g network, however, activity of an 802.11b participant will reduce the data rate of the overall 802.11g network.

Like 802.11b, 802.11g devices suffer interference from other products operating in the 2.4 GHz band, for example wireless keyboards.

802.11-2007[edit]

In 2003, task group TGma was authorized to "roll up" many of the amendments to the 1999 version of the 802.11 standard. REVma or 802.11ma, as it was called, created a single document that merged 8 amendments (802.11a, b, d, e, g, h, i, j) with the base standard. Upon approval on March 8, 2007, 802.11REVma was renamed to the then-current base standard IEEE 802.11-2007.[13]

 

 

802.11n

 

Main article: IEEE 802.11n-2009

802.11n is an amendment which improves upon the previous 802.11 standards by adding multiple-input multiple-output antennas (MIMO). 802.11n operates on both the 2.4 GHz and the lesser used 5 GHz bands. Support for 5 GHz bands is optional. It operates at a maximum net data rate from 54 Mbit/s to 600 Mbit/s. The IEEE has approved the amendment and it was published in October 2009.[14][15] Prior to the final ratification, enterprises were already migrating to 802.11n networks based on the Wi-Fi Alliance's certification of products conforming to a 2007 draft of the 802.11n proposal.

802.11-2012[edit]

In 2007, task group TGmb was authorized to "roll up" many of the amendments to the 2007 version of the 802.11 standard. REVmb or 802.11mb, as it was called, created a single document that merged ten amendments (802.11k, r, y, n, w, p, z, v, u, s) with the 2007 base standard. In addition much cleanup was done, including a reordering of many of the clauses.[16] Upon publication on March 29, 2012, the new standard was referred to as IEEE 802.11-2012.

 

 

802.11ac

 

Main article: IEEE 802.11ac

IEEE 802.11ac-2013 is an amendment to IEEE 802.11, published in December 2013, that builds on 802.11n.[17] Changes compared to 802.11n include wider channels (80 or 160 MHz versus 40 MHz) in the 5 GHz band, more spatial streams (up to eight versus four), higher order modulation (up to 256-QAM vs. 64-QAM), and the addition of Multi-user MIMO (MU-MIMO). As of October 2013, high-end implementations support 80 MHz channels, three spatial streams, and 256-QAM, yielding a data rate of up to 433.3 Mbit/s per spatial stream, 1300 Mbit/s total, in 80 MHz channels in the 5 GHz band.[18] Vendors have announced plans to release so-called "Wave 2" devices with support for 160 MHz channels, four spatial streams, and MU-MIMO in 2014 and 2015.[19][20][21]

 

 

802.11ad

 

Main article: IEEE 802.11ad

IEEE 802.11ad is an amendment that defines a new physical layer for 802.11 networks to operate in the 60 GHz millimeter wave spectrum. This frequency band has significantly different propagation characteristics than the 2.4 GHz and 5 GHz bands where Wi-Finetworks operate. Products implementing the 802.11ad standard are being brought to market under the WiGig brand name. The certification program is now being developed by the Wi-Fi Alliance instead of the now defunct WiGig Alliance.[22] The peak transmission rate of 802.11ad is 7Gbit/s.[23]

 

 

802.11af

 

Main article: IEEE 802.11af

IEEE 802.11af, also referred to as "White-Fi" and "Super Wi-Fi",[24] is an amendment, approved in February 2014, that allows WLAN operation in TV white space spectrum in the VHF and UHF bands between 54 and 790 MHz.[6][25] It uses cognitive radio technology to transmit on unused TV channels, with the standard taking measures to limit interference for primary users, such as analog TV, digital TV, and wireless microphones.[25] Access points and stations determine their position using a satellite positioning system such as GPSand use the Internet to query a geolocation database (GDB) provided by a regional regulatory agency to discover what frequency channels are available for use at a given time and position.[25] The physical layer uses OFDM and is based on 802.11ac.[26] The propagation path loss as well as the attenuation by materials such as brick and concrete is lower in the UHF and VHF bands than in the 2.4 and 5 GHz bands, which increases the possible range.[25] The frequency channels are 6 to 8 MHz wide, depending on the regulatory domain.[25] Up to four channels may be bonded in either one or two contiguous blocks.[25] MIMO operation is possible with up to four streams used for either space–time block code (STBC) or multi-user (MU) operation.[25] The achievable data rate per spatial stream is 26.7 Mbit/s for 6 and 7 MHz channels and 35.6 Mbit/s for 8 MHz channels.[27] With four spatial streams and four bonded channels, the maximum data rate is 426.7 Mbit/s for 6 and 7 MHz channels and 568.9 Mbit/s for 8 MHz channels.[27]

 

 

 

source: wikipedia.org

[LukaP]

a, b, g have the same speed but are different in security and stuff

n is faster, more secure, stable due to 5GHz band

ac is faster, also more chganels

ax is coming, even faster

[juretrn]

@Wyre ahem....

[Wyre]

@Wyre ahem....

 

LOL, You did post a bit faster than I did... LOL

[juretrn]

LOL, You did post a bit faster than I did... LOL

no I meant the huge text wall, but now I see you fixed that a bit.

[MrSuperb]

a, b, g have the same speed but are different in security and stuff

nope

b = max 11 Mb/s

a = max 54 Mb/s

g = max 54 Mb/s

n = max 600 MB/s

[razvan_and]

b = max 11 Mb/s

a = max 54 Mb/s with 5 Ghz

g = max 54 Mb/s with 2.4 Ghz only (standard) or 108 Mb/s on compatible hardware (like Super G).

n = max 450 Mb/s on 5 Ghz, 450 Mb/s (in theory) on 2.4 Ghz, using compatible hardware.

But actual throughput is half of the advertised speed, so ... yeah.

[skywake]

You need to be careful when you read the speed ratings for wireless. Even the "half the speed" yardstick is off the mark especially when you get upto higher speed APs. That's before you even consider the fact that most wireless clients won't be sitting right next to the router when they're in use. Even without people pushing the distance to the limit. So I think it's simpler to just break it down this way:

 

There are only four standards you should look at IMO:

N300: Max of ~70Mbps between it and a single device, entry level product. Use for sharing <50Mbps 'nets with <5 devices. I wouldn't go any lower than this.

N600: Max of ~70Mbps but with two radios. Use for sharing 50-100Mbps 'nets and maybe some local video streaming. Will support more traffic than N300 overall but not with just 1 device

AC1200: Max of ~300Mbps to a single client. Use for sharing <200Mbps 'nets with compatible clients. Good enough for most things (including Nvidia Shield) and affordable. The market "sweet spot" ATM

AC1900/3200: Max of ~400Mbps with 2 radios on 1900 and 3 on 3200. The best gear on the market for when everything else isn't "good enough" or you have money to burn on this

[Wyre]

The main reason that wireless is essentially 'half speed' is because of something called Duplex.

 

Wired networks are capable of 'Full Duplex' or the ability to both Transmit and Receive data packets at the same time. While wireless networks can only perform in 'Half Duplex' they can only Transmit or Receive data packets at one time. With this said a Tx or Transmit can take place until the wireless system needs to Receive or Rx a data packet. Then an interrupt is sent to halt the current operation and reverse the directionality of the data path.

 

With network overhead in place you will be doing well to run both Tx and Rx operations within 40% - 50% of the overall speeds listed.

 

Stanford university is working on a full duplex wireless system... but the cost will be prohibitive for some time.

[skywake]

Hmm, never thought about the numbers they put on the box in that way. I thought there wasn't much rationale to them at all given how poorly they correlate to actual performance. Either way "half the speed" is overly generous. They not only add both up and down despite the fact that it's Half-Duplex but you won't even get half the speed for a single client even if you somehow had a perfect signal. Then when they get another radio they just tack it on the end so the number is even more unrealistic.

 

So when they say N300 it's not "300Mbps" in the same way that 1Gbps Ethernet is "1Gbps". Not in the slightest. On paper it's 150Mbps Tx and 150Mbps Rx, that's how the get the number. In reality though it's closer to 70Mbps instead of 150Mbps and even that's generous. So basically if N300 was given a number that was comparable to Ethernet it wouldn't be 300Mbps. not even close. If it was a fair comparison you'd probably call it 70Mbps Half-Duplex.