802.11n: High Throughput, Not Just Fast Wireless

eggboard writes "Unstrung reveals that the 802.11 working group is spawning 802.11n, a high-throughput task group to work on increasing the actual data:symbol ratio in wireless networks while also boosting speed to 108 Mbps to 320 Mbps. Most people who use 802.11a, b, or g know that actual net throughput, or the real data that's carried, is a fraction of the cited rate: maybe 7 Mbps in the 11 Mbps 802.11b flavor and 25 Mbps in the 54 Mbps a and g flavors. The goal of 802.11n is to increase speed, sure, but also to increase the percentage of symbols that don't bear overhead. The bad news: they predict 2005 or 2006 for completion."

2007 or 2008?

[Anonymous Coward]

Come on - by then UWB coupled with cellular and mesh will offer those speeds. "n" should stand for "n" significant.

I think I speak for everyone...

[k-0s]

I think I speak for everyone when I say put egos aside, gather the best of each protocol into one protocol and make it the standard and release products for it. I think people (in general) are scared right now because they don't want to buy a product that will not be usuable in a year or two. I want my WiFi already.

Re:I think I speak for everyone...

[Anonymous Coward]

you're right. But its not like you're plunking down for a mainframe here. If its for home and desktop use, it doesn't matter. Just set it up and run it. It works fine right now. So, I assume you're talking about a card for your laptop that in a couple of years, you might not be able to link up at Starbucks or the University or something. Yeah, that's possible but the cards aren't prohibitively expensive. A couple years use for their price right now is a pretty good proposition. Not to mention you'll

Re:I think I speak for everyone...

[k-0s]

Maybe not for you but not having a job makes anything cost prohibitive. Well I have a job but not MUCH of I job I should say. I have enough to pay for living and with what little extra I have I'd like to be able to get a wireless card, specifically one that I won't have to buy again in a year or 2 when the specs change.

Progress...

[sgtsanity]

I think you're a bit confused about how the ways are going. At any given time, they're developing several different specs for wireless communication. Some of these, such as the publicized 802.11a, b, and g are hardware-side, meaning they have to deal with the way these things are actually transmitted. Others are more software-side, meaning they have to do with encrypting data and whatnot. Furthermore, all of these (except for a few earlier strange circumstances such as 802.11a) are backwards compatible.

In short, the hardware you buy today WILL be usable in a year or two. It just won't be the fastest, bestest thing on the market. Think of it as Moore's Law translated to wireless communication.

uh

[Anonymous Coward]

so why hasn't this been done before? Shouldn't a good spec already be lean? We've gone through six incarnations or so of 802.11 and we still have this kludge going around? I'm sure its not as easy as I'm making it out to be, but I would get fired if someone could take my spec and cut out this much overhead from it. The time to spend the four or five years crafting a good symbol set is before the thing goes public, not after.

Re:uh

[Stan Chesnutt]

If you take a look at the 802.11 spec from 1999, you'll see a lot of stuff there that is spec'd for backwards compatibility. For example, there is the PS-Poll exchange grafted atop the normal powersave-state protocol. A lot of this backwards compatibility is at the cost of performance. A "design-from-scratch" approach could result in a much more efficient data-networking protocol design that incorporates what has been learned in the last ten years or so. However, much of the IEEE process is subject to internecine politics and hidebound practices. I am hopeful but not too optimistic.

Re:uh

[minard]

because the efficiency enhancement isn't free. It adds complexity and cost. However, as the data rate goes up, the payback goes up too. So there's a tradeoff which is going to be different based on the data rate that you can achieve.

Re:they should use hexadecimal .

[Anonymous Coward]

Hmm, well their protocol name is clearly hexadecimal: 802.11a = 8*256 + 2 + 1/16 + 1/256 + 10/4096 = 2050.068848

recipe for high speed

[eenglish_ca]

If you want highspeed wireless networking just buy some of the at&t microwave bunkers. As a bonus you can have huge w/lan parties and microwave your food free of charge at the same time.

Not being used...

[InnovativeCX]

Favorite quote from the article:

802.11 Specification letter suffix: O
What it does: Not being used, because it looks confusing.

In all seriousness, this would be an incredibly useful technology--802.11b at it's current real speed is quite unusable for transferring files of significant size. However, I have to admit that I'm tired of seeing a Baskin-Robbins offering of wireless flavors...802.11g is a noble effort at standardization, but backwards-compatible technology is a must. I can't afford to hav

Re:Not being used...

[deadsaijinx*]

hmmm... b then a then g then n ... engineers don't beleive in the alphabet. "[the alphabet] is just a suggestion, Marge. Like pants" - homer
yes, I know that the quote actually talks about roads, so lets just call this the information super HIGHWAY and get on with our lives ^^

(if the above is incoherent, you haven't spent enuf time on slashdot)

Re:Not being used...

[minard]

all the letters are used (except l). Here's a list:

802.11a - physical layer

802.11b - physical layer

802.11c - addition to 802.1D bridging tables

802.11d - international roaming

802.11e - QoS

802.11F - inter AP protocols (the capital letter is important, but I won't go into that here)

802.11g - physical layer

802.11h - 5GHz regulatory conformance in Europe

802.11i - security

802.11j - Japanese 5GHz band extensions

802.11k - radio resource measurement

802.11m - maintenance

802.11n - high throughput

Re:Not being used...

[minard]

not quite true. However, the letter "l" has been skipped for exactly this reason... the actual quoted reason is that "802.11l" would be "a typographical accident waiting to happen". We haven't got to "o" yet

good idea

[stellar7]

I'm glad someone is focusing on the overhead and efficiency of the standards and not just trying to get something out there with a big unrealistic marketable speed. I guess comparing advertised Mbps on wireless devices could be like comparing MHz for CPUs by different companies.

Re:good idea

[IAR80]

Yep. Plus using CDMA (DSSS or FHSS) you never know how much throughput you'll get at a given time even taking in account the overhead. So that Mbps thing is useless.

It's not just marketing.

[mindstrm]

It's just the physics of it.

10Mbps ethernet is 10mbps because that's how many bits per second the channel itself can hold. It actually means nothing at all about the host to host bandwidth. In the case of ethernet, the numbers are very close, so nobody really thinks about it.

11Mbps wireless is the same thing.. it's the bitrate of the radio channel, not the useful data rate of the protocol itslef... and with wireless, there is more overhead. A lot more.

If these numbers are not satisfactory, what number sh

802.11??

[Czernobog]

This has to do with information theory, source and channel coding and modulation.

It'd be nice if these people standardised on a framework that can be combined with various coding and modulation schemes, in a modular sense, instead of creating 802.11xyz groups every now and then...

Guess marketers and managers (ie The Incompetent at best, The Illiterate as per usual) have taken over from the engineers.

Article wasn't very meaty

[CausticWindow]

No real details on what they're trying to achieve.

Are they aiming on improving software, the hardware or both? Anybody know more about this?

60% throughput is normal

[Anonymous Coward]

The speeds quoted are burst speeds. Assuming
binomial distribution of arriving packets (and that is the regular assumption), the throughput
for any packet based transmission is ~60% of the
burst speed. So 7MBPS out 11 is right what you
should expect.

Re:60% throughput is normal

[IAR80]

Depends verry nuch on the environment. You'll get 60% in the countryside while 20% in crouded spectrum metropolitan area might be a good asumption.

Uhmm?

[aspjunkie]

Have they taken into consideration that they might run out of letters at some point? ..especially if we skip from g to n.. there's some cool letters in there...

Re:Uhmm?

[Wesley Felter]

I think 802.3 (Ethernet) ran out of letters, so they started using aa, ab, etc.

And if you RTFA, you see that the letters between g and n are being used.

Re:Uhmm?

[Luminous Coward]

IEEE 802.3 CSMA/CD [ieee.org]

IEEE Std 802.3z-1998, Gigabit Ethernet.
IEEE Std 802.3aa-1998, Maintenance Revision #5 (100BASE-T).
IEEE Std 802.3ab-1999, 1000BASE-T.
IEEE Std 802.3ac-1998, VLAN TAG.
IEEE Std 802.3ad-2000, Link Aggregation.
IEEE Std 802.3ae-2002, 10Gb/s Ethernet.
IEEE Std 802.3ag-2002, Maintenance Revisions #6.

P802.3af, DTE Power via MDI.
P802.3ah, Ethernet in the First Mile.
P802.3aj, Maintenance #7 Task Force.
P802.3ak, 10GBASE-CX4 Task Force.

No big deal.

Throughput

[vslee]

Throughput on 802.11b networks is actually only around 3-4 Mbps in optimal conditions, less than 50% of the theoretical maximum.

Re:Throughput

[servanya]

The theoretical max it 5.5 Mbps, not 7. I've gotten close to 4.5 before..

Re:Throughput

[martyn s]

I think he was talking about the *real* theoretical max: 11Mbps.

Re:Throughput

[martyn s]

Okay, okay, I understand now. Some post further on explained that it's 11Mbps TOTAL in both directions. Or, in other words, as he put it, 5.5 Mbps Full-duplex. You were right, apologies.

Re:Throughput

[malia8888]

Two ideas keep running through my mind. The first is we are already on the letter "n" and the technology is so young. We better find another designation or we will be referring to the "son of 802.11 b" very soon.

Number two, with throughput increasing at this rate I better get that Mavis Beacon typing software, I gotta type faster.

Throughput is depended on many things

[saden1]

Too many workstations on the network and you got a recipe for collision. There are just too many factors to dramatically increase throughput.

This is the story of 802.11

[worst_name_ever]

I think it's kind of funny they're calling it 802.11n.

They might as well just give up and start saying "Oh, you don't want 802.11[n] anymore - you should throw away all your hardware and get 802.11[n+1] instead, since it'll be so much better! No, really!"

Real speeds of 802.11

[lindsayt]

I just wanted to point out that if we accepted 11Mbps and 54Mbps as the speeds of 802.11b and 802.11a/g then we would have to call regular fast ethernet 200Mbps. 802.11b is 5.5Mbps full-duplex and a and g both are 27Mbps full duplex. It is true that the radio signals are capable of carrying 11 and 54 respectively, but half of this bandwidth is dedicated for each direction, so that the MAXIMUM one-way speed you can achieve with 802.11a/g is 27Mbps. This means that if they're hitting real-life numbers of 24Mbps (I doubt it) of data throughput, then they're doing really well - about 88% of theoretical. That's as good as you can really expect from wired networks, in terms of throughput to bandwidth ratios.

Re:Real speeds of 802.11

[Wesley Felter]

802.11 is half duplex, not full duplex. Heck, it isn't even TDD.

Re:Real speeds of 802.11

[silas_moeckel]

Actualy it's half duplex a single sender could get close to 11 as long as nothing else was in the air like responce packets. This is the same as traditional ethernet in a standard envirnment twister pair ethernet only goes dull duplex with switching involved.

Noop.

[mindstrm]

- Technically we call it "100baseT Full Duplex"
- The 100 refers to 100 bits/second as a maximum channel capacity, not the maximum transfer rate between two hosts. it takes multiple hosts using the channel at the same time to saturate the channel.
- Half of the bandwidth of 802.11b is NOT set for " each direction". The full amount can be used for either direction.. it's half duplex. Further, the 11mbps refers to the radio channel, not any " direction".

- Full channel usage happens with multiple hosts, not with only two. with two hosts.. just like ethernet, but the delays and wait times are larger, adn there is more protocol overhead, due to the lack of collision detection.

Quick Guide to IEEE 802.11

[Luminous Coward]

Here is a complete chart [ieee.org] summarizing the work done by the various Task Groups (a through m) and Study Groups. The results of the letter ballots [ieee.org] are also available.

• TGe status [ieee.org]
• TGf status [ieee.org]
• TGg status [ieee.org]
• TGh status [ieee.org]
• TGi status [ieee.org]
• TGk status [ieee.org]

802.11g

[dg1kjd]

Maybe they should concentrate on approving the 11g standard first.
Just to comment on the "users of 11g" stuff: The implementations you are currently seeing in the shops are based upon more or less early *drafts* of the standard. The fit will really start hitting the shan when people start combining devices from different manufacturers: Incompatibilities range from different modulation schemes (TI) over incompatible MAC protocol elements (dataset identifiers in AP capabilities) to legacy support (some old

Forget about speed - How about security???

[tstoneman]

Why don't those guys forget about trying to make things faster, and instead make things more secure. I have 802.11b but I shut it off when I don't use it because I'm hella scared that my neighbor is going to download kiddie porn off my wireless connection, but the feds will bust me because it looked like it was coming from my ip address!

Let's hunker down, get some real security, and then move to something faster!!!

Re:Forget about speed - How about security???

[dattaway]

I have to use encrypted tunneling, because WEP is worthless. It causes my Linksys cards to lock up within minutes or seconds under full throughput. My Dlink cards do better, but resetting the cards after every timeout is annoying. Reminds me when Windows95 came out.

If the wireless cards had a second processor to handle the communications and leave the signal processing to the DSP, we might have better reliability. These cards (except the Cisco) we have now are cheap and barely functional.

802.1x + rolling keys is secure, even with WEP

[Stan Chesnutt]

If you can find an access-point that will do 802.1x properly with rolling keys, you are in great shape, even with RC4 WEP. The WEP attacks that have been published exploit a vulnerability with poorly-chosen IV values, and if enough encrypted packets are captured, the keys can be inferred. But, if you rekey on a frequent basis, and use a "modern" implementation of WEP which avoids the weak IV values, then you will be fine. Unfortunately, I don't know which SOHO access-point devices currently support an optimum 802.1x implementation. On the client side, Windows XP SP1 does it right, and I believe that Meetinghouse has client implementations for Linux and Mac OSX.

802.1x and WEP is not a Home User's solution

[jefftp]

802.1x is only half the picture. To run 802.1x you'll need to select an EAP (extensible authentication protocol) method.

Currently, there's 4 common flavors of EAP: EAP-TLS, EAP-TTLS, LEAP, and PEAP.

LEAP is Cisco proprietary and will probably be dumped when Cisco moves to PEAP. Surprisingly, Apple licensed LEAP from Cisco, but only on the client side. You can get LEAP support via the latest update to the Airport client software for MacOS 9 or X. LEAP's weakness is that you can see the username in cleartext

Multiple wireless nics?

[whereiswaldo]

Dumb question... is it possible to install two or more wireless NICs, enable support for splitting tcp/ip traffic amongst them, and get twice the throughput? I thought this was possible using ethernet cable... but I'm not sure how the wireless frequency bandwidth would limit something like this.

Re:Multiple wireless nics?

[Wesley Felter]

As long as you have multiple access points and put them on different channels it should work.

Differences between them all...?

[dargaud]

Could someone please post a link or a explaination of the various practical differences between a, b, g, n... I know someone posted something about the various task groups, but it is very theorical. I want to know things like average trhoughput, distance, built-in security...

What should an average joe like me who wants to have his laptop access files and the 'net onto the main home 'puter should choose ? Is it the same thing that for going on a road trip and hoping to find access points ?

Re:Differences between them all...?

[minard]

here's a brief summary:

802.11b, a, and g are primarily physical layer (OSI layer 1) extensions to the base 802.11-1997 standard (also referred to as 802.11-1999, which is actually the same thing published by ISO). None of these speaks to security issues, or QoS issues for that matter.

802.11i is the security extension (still in development) which is MAC layer (OSI layer 2). It applies to all of the physical layers.

802.11e is QoS extensions, again at the MAC layer, and applies to all the physical layers.

8

For Joe Average User, 802.11b is PLENTY

[HelbaSluice]

For virtually all consumer applications, 60% (or less!) of 802.11b's throughput is an ample plenty.

Why? Because the VAST majority of data they schlep goes through their broadband provider on the way to or from the Internet, where they don't get anything even APPROACHING 5 Mb/s. The line out of the house is the bottleneck in my home and in many, many other homes.

that's easy...

[mikeee]

This increase in efficiency will be achieved by having slashdot duplicate stories filtered out at the transport layer.

Just a few more letters...

[mnewton32]

and maybe we can get enough bandwidth for wireless VGA! Should only need 600 or 700 Mbps...