Forgot your password?
typodupeerror
Technology

802.11b at 22mbps 137

Posted by CmdrTaco
from the bring-it-on dept.
Radi-0-head writes "According to this article at PCWorld.com, "U.S. Robotics (USR) has boosted the speed of its latest range of wireless LAN products for small businesses to 22 megabits per second, while retaining compatibility with existing 2.4-GHz systems built to the IEEE 802.11b standard..." Sounds to me like a great alternative to 802.11a."
This discussion has been archived. No new comments can be posted.

802.11b at 22mbps

Comments Filter:
  • by mbone (558574)
    IMHO, 802.11a is DOA. I can't wait for 802.11g - which should interoperate with 802.11b.
    • Your opinion is questionable, then, given the massive proliferation and heavy sales of 802.11a hardware in the industry (some companies putting 802.11a hardware in their entire line of laptops). 802.11g offers no real advantage over 802.11a, so given that it's hitting the market a year or so later, I'd say that it doesn't have much of a chance.
      • Re:802.11g (Score:2, Informative)

        by smagoun (546733)
        Some interesting comparisons of 802.11a, b, g and the various combinations thereof that are kicking around: Clarity & Understanding: The High-speed WLAN standards debate [80211-planet.com]
      • i actually have computer that used to be on the wireless network using 802.11b... unfortunatly there was a microwave next to it so there was so much interference i could not stand it... every time the microwave goes on BAM network error... so i got some nice sheilded cable and ran that down to my wired hub... so personally im saving up for 802.11a becuase of the frequency difference so i dont worry about interferance AND it has better range/data rate... you can always get a 802.11a/b access point if your so picky...
      • What laptops have 802.11a?
      • The 'massive proliferation and heavy sales of 802.11a hardware' are entirely in the US; the EU is only just starting to approve their usage. [theregister.co.uk]

        Saying 802.11a is widespread now is like saying GSM was widespread five years ago - it was in some places, with other countries completely lacking in support.

    • Be careful. Everything is not as simple as it seems....

      First, actual throughput doesn't reflect the "nominal" speed on the box. Anybody who has used 802.11b will know that the most you actually get is about 6Mb/s (and that's under very ideal conditions). This matters in your choice of 802.11b, .11g or .11a., because the difference between "nominal" and "actual" are very different in each case.

      The reasons for the deviation are twofold:

      1. MAC & PHY layer overheads. 802.11 has much higher intrinsic overheads like inter-packet spaces and preambles than with traditional wired Ethernet. This means that for every packet there is a time on-air that isn't used for data. As the "nominal" data rate is pushed up, this "dead time" stays numerically the same, so becoming a higher proportion of the total. Bottom line: "22Mb/s" 802.11b isn't actually going to be anything like twice as fast. On the other hand, 802.11a is quite different - because all of the overheads have been shrunk; it isn't just a higher nominal rate. For instance, the preamble changes from 96us (802.11b) to 16us (802.11a). That stuff matters, big time.

      2. Errors. Packets in a wireless LAN frequently get corrupted in transmission. Much of the complexity of the 802.11 protocol is detecting and retransmitting the corrupted packets. But of course, every time you do that, you're spending more bandwidth. Bottom line - as the channel deteriorates, meaning more packet errors, your actual throughput goes down. This matters here because 802.11b has only three channels, in a very polluted band (Bluetooth, microwaves, cordless phones, X10 cameras, and other 802.11b systems). This pollution is only going to get worse. On the other hand, 802.11a has eight channels (and there's potentially more to be allocated over the next few years) and the spectrum rules are built to deliberately disadvantage "narrow band" systems, making it effectively uneconomic to build cordless phones or garage door openers that use the band (and no microwaves, btw).

  • This may have increased the possibilities of using 802.11b. But besides cost why not just go all out with 802.11a and enjoy the 100mbps. It may be an alternative but it's still not quite as fast.
    • I guess for the _average_ home user, it is a welcoming news, double the speed with only roughly $20 in price sounds good to me.
    • 802.11a is 54mbps not 100.

    • As you probably know, 802.11a and 802.11b each define a different physical layer. 802.11b radios transmit at 2.4 GHz and send data up to 11 Mbps using direct sequence spread spectrum modulation; whereas, 802.11a radios transmit at 5 GHz and send data up to 54 Mbps using OFDM (Orthogonal Frequency Division Multiplexing).
      • Right you are.
        And it has been proven by Wifi companies like Atheros that OFDM is more robust that DSSS techniques.
        It doesn't matter if you can put 1Gbps into the air channel if your packet error rate suffers so much that you have an effective rate of 10bps.
        This is where 802.11a shines with its forward error schemes, interleaving, OFDM instead of DSSS Barker sequences like 802.11b.
        OFDM will also allow the use of more channels so 802.11a SPEC could be updated later to more than the 48 channels for data comunication.
        They could update it to have 96 true channels and make it work at ~110Mbs or higher with schemes like 256-QAM instead of 64-QAM. That would be a byte encoded symbol per channel! It would then be easy to have 144Mbs with little work on the spec!
  • This article refers to USR as a totally stand-alone identity. This is news to me. Did 3Com spin off USR recently? Last I heard, they were a totally absorbed identity, thus no more USR modems or USR Palm Pilots (Irrelevant now). And furthermore, if US Robotics exists again, has Bernard Shifman [petemoss.com] returned to work there? :)

    • Did 3Com spin off USR recently?


      Yes. Not that recently, actually.
    • I agree. Join the T(H)GSB [slashdot.org] Apr 21-27

      $10 says slashdot.org gets a noticeable boost in the number of people visiting the site during that time... people's curiosity will be peaked and they'll have to come "just once" to see if the blackout is working.
      • $10 says slashdot.org gets a noticeable boost in the number of people visiting the site during that time... people's curiosity will be peaked and they'll have to come "just once" to see if the blackout is working.

        Doubtful as the "great blackout" is just on the comment pages, and from the front page you can see how many comments there are, and how many are at or above your threshold...

        So nobody has to "break the picket line" to see if the store is empty -- in effect it has these big plate glass windows...

    • > Did 3Com spin off USR recently?

      "Purchased by 3Com in 1997, U.S. Robotics re-emerged as an independent company in September 2000."

      Excerpted from http://www.usr.com/inside/in-backgrounder.asp

      USRobotics is back and they're focusing on products like modems, wireless gear and broadband routers as well as some new and interesting stuff like the SoundLink Wireless Audio Delivery System.

      I have fond memories of my first USRobotics HST modem and I wish them the best of luck.

  • You're not only getting faster speed, you're getting a stronger radio signal

    Operating at the 2.4GHz range, this means I can throw out my microwave. This thing will heat up my coffee while giving me bandwidth.....
    • Yessir! 100mW of coffee bean roasting power. A slightly longer wait, but surfing while you wait should be enjoyable. Use a highly directional 26dBi antenna to concentrate that power into a tiny area with an effective power of 25 watts. You might be able to see microscopic bubbles of steam...
    • Just hope it doesn't heat up your nuts while you're using your laptop...
  • more on this (Score:2, Informative)

    by doubtless (267357)
    More news on the 22mbps USR WiFi can be found here [bbwexchange.com], and the 88W8200 Wireless LAN Baseband Processor information can be found here [marvell.com]
  • 802.11g (Score:3, Interesting)

    by cyr (571397) on Saturday April 20, 2002 @11:13AM (#3379398) Homepage
    A nearly free 100% speed boost is nice, but I would wait for 802.11g instead, giving 54Mbps in the 2.4GHz band and also being backward compatible with 802.11b.

    I'm not an expert, but it seems to me 802.11a is doomed. Is there any reason to prefer it over the upcoming 54Mbps 2.4GHz stuff?
    • Is there any reason to prefer it over the upcoming 54Mbps 2.4GHz stuff?

      The fact that it's here today, and not "upcoming", perhaps? (Given that 802.11a is available right now, I think a much more reasonable question is "Is there any reason to prefer 802.11g over 802.11a?". To many, the answer is no. The backwards compatability of 802.11g is largely irrelevant because of the ultra-low market presence of 802.11b, hence 802.11a really is the first wireless technology many firms are implementing, so they have little concern if it's backwards compatible with an obsolete standard. On top of that the 2.4Ghz spectrum is rife with interference (cordless phones, bluetooth, etc.).

    • by Freeptop (123103) on Saturday April 20, 2002 @12:35PM (#3379691)
      First, the 2.4 GHz has a ton of other devices sharing the same spectrum, from Bluetooth to wireless headphones, to your microwave. 802.11a runs in the 5GHz band instead.

      Second, according to the last proposals I'd heard of, 802.11g is going to achieve higher bandwidth by taking up more of the spectrum. In other words, it is going to use more channels to simultaneously broadcast data, rather than just being able to shove more data down the same channel. This means your own access points will begin to interfere with each other much sooner than your 802.11a or .11b APs will.

      In general, it is going to depend on your situation as to which you wish to choose. 802.11g will be great for backwards compatibility, but the news coming out of IEEE seems to indicate that 54Mbps is more like something to shoot for than something they expect to achieve. 802.11a won't have compatibility, and it will also have a shorter range, but it will have higher speeds with less interference.
      • As a sidenote, it should be noted that in many tests (most recently PC Magazines wireless shootout) have shown a very similar range between 802.11a & 802.11b : The longer range of 802.11b was mostly a hypothetical, but in real world situations they often find them comparable.

        Just a point of interest for firms looking at 802.11b because of the hyped extra range.
      • Wow. This post looks familiar.
        Oh yeah, because I originally posted it here [slashdot.org] .
        Only there, it had my name as the author of the post...
        A hint: Please include credit for the original content if you are going to repost a comment. Otherwise it is called plagarism.
  • by DNS-and-BIND (461968) on Saturday April 20, 2002 @11:13AM (#3379399) Homepage
    Oh, God no, not proprietary USR hardware that gives superior connection speeds! Not a return to the bad old days!
    • It does have a sort of "x2/K56flex/v90" feel to it. ..
      • Beh, was fun explaining to n00bs on BBSs though why they couldn't get 56k to their local BBSs. LOL. Alls fun, alls fun.

        Besides, think of the +5 informative possabilities on /. everytime an article is posted on the topic and somebody gets confused! Hell if this goes through Karma rates will skyrocket! ;D (joke there folks, haha laugh)
      • >It does have a sort of "x2/K56flex/v90" feel to
        >it. ..

        I was thinking "802.11b.terbo", personally.

        Or maybe "802.11b.HST", since it's USR...

        -l

        • I remember V.everything USR modems.... what about v.everything LAN interfaces.. YEY! If I only could do lazer, microwave, radiowave and perhaps pigeon carried LAN with one of doze.

          Oh yes. I just came home from town now and I am pretty drunk. thanx for noticing.,
    • Heh, I still have my $400+ USR HST (not DS!) 14.4kb modem lurking in my storage room. It's the size of a notebook computer.

      I don't consider it the "bad old days" at all. I was running 14.4 amongst all the 2400 bps modems a good year or two before v32/v32bis modems were generally available.

      • Bad old days in the sense that the privileged few (rich) get a fast, superior experience, and the rest of us that use the industry standard get a crappy experience.
        • Um, isn't that the way that life works normally? I mean, I don't have the latest and greatest Lexus or Cadillac. Yet, features that were first used on much more expensive cars are now standard feature on run-of-the-mill cars, such as airbags. Most of the time companies will over-charge for new technologies or products because they have to recoup their R&D cost relatively quickly. Once that is done then they can realistically drop the price to make it available to the average consumer. Just wait, sooner or later those 21" LCD displays will be a few hundred instead of thousands. Welcome to reality...
          • Well frankly, the rich can keep the airbags. I'd rather see a rich fuck get killed by a 'life-saving device', while I brace against the steering wheel and wait it out.
      • Heh, I still have my $400+ USR HST (not DS!) 14.4kb modem lurking in my storage room. It's the size of a notebook computer.

        Pfah! That's nothing. I have a Hayes 300 baud StupidModem for my SOL-20. It's twice the size of your average PCI card (being a full S-100 card), uses an external "brick" for the phone line interface, has no DTMF generator (pulse dialing only), no internal speaker, and no internal software for dialing or connection establishment. You have to write a short program to fiddle the hook relay to count out dialing pulses, then wait and pray the connection works out.

        Ah, those were the days...

        BTW, who else learned to read NetNews off the screen at 2400 bps? :-)

        Schwab

        • Hehe. Yeah. That's how I got into speed reading.
          Back then I would read all the USENET news. All of
          it. Sitting at home with an Atari 1040ST, scrolling
          all the text that 2400bps could push.

    • I'm with you, pal. Everyone who bought one of USR's proprietary high-speed modems ended up having to spend extra money to replace it, because the standard that was ultimately adopted was superior to -- and incompatible with -- USR's.

      HST was obsoleted and replaced with V.32bis. X2 was obsoleted and replaced with V.90. I don't plan on wasting my money; I'll wait for 802.11a to get cheaper.

      Schwab

      • Ok, I got one for The History Channel. It's 1990, maybe 1991, a friend of mine and I both have Telebit T2500's. $1,100.00 apiece (No I'm not rich and neither is he, our companies bought them). Talking to each other we could do 19,200 when everything else was 9600 max. The thing was bigger than a laptop, and the most programmable modem on the planet. Manual was over an inch thick and the thing had hundreds of programmable registers. Read like an episode of The Twilight Zone, every register had a dozen variables, each of which was dependent on the settings of the dozens of variables in other registers, which were in turn...you get the idea. We'd stay up all night in our respective offices trying different combinations, phoning each other with the register settings, trying to connect at 19,200 (full-duplex), phoning again....I realized I was getting punchy when I dropped my pen and hit Cmd-z to get it back (Yes, for the record, I was on a Mac IIfx). I still have the thing in a closet somewhere.

        The last modem I owned cost $89.00 (USR X2, which, as far as I recall I flash-upgraded to V.90) and worked out of the box. Now I'm on DSL at about 100 KB/s with a homebrew Software Base Station under OSX running to an Orinoco card in a PBG3 that hangs out in the living room.

        Don't make me tell you about all the fun I had with 300 baud acoustic couplers and 8-level paper tape....

  • nothing new (Score:4, Informative)

    by smagoun (546733) on Saturday April 20, 2002 @11:15AM (#3379406) Homepage
    This isn't terribly new. Companies have been doing 22Mbps 802.11 for awhile now: Link from 6/2001 [theregister.co.uk]
  • mbps?? (Score:4, Funny)

    by daghlian (113201) on Saturday April 20, 2002 @11:19AM (#3379416) Homepage Journal
    Wow!! 22 millibits per second. That means it only takes 45 seconds to transfer a whole bit!

    I can't wait until 22Mbps devices come out.
  • The most interesting thing in this article, as the speed itself isn't blow-your-mind-out-of-the-sky for current wireless, is that this will be backwards compatible with current 802.11b.
    Doubling of the bandwidth for parts of the wireless commmunities that have spread up will gradually take place - and we'll all be the better for it.
  • So at twice the speed, I can gather enough packets to crack WEP encryption keys in half the time using Airsnort [shmoo.com]. Seriously, I really want secure security! My office won't move to wireless until there is cheap and proven FIPS-140 compliant security.
  • by chill (34294) on Saturday April 20, 2002 @11:23AM (#3379429) Journal
    11 Mbps to 22 Mbps SOUNDS like a 100% increase, but what is the real speed/range gain? Given an 11 Mbps system with 3 nodes each at 10m from the access point, what is the actual thruput? Is switching to the USR system going to actually DOUBLE that?

    Network speeds rank right up there with CRT sizes, CD-ROM spin speeds and tape storage capacity as some of the biggest bullshit numbers in computing.
    • Don't forget your network architecture, collision rates, and so forth. Since you are going wireless, what type of other possible issues does this new technology have?

      Definitely a ton of questions to be asked, and this is why the OFFICIAL Wireless specs take so damn long to get through committee.

      Ok actually it is the fact that they ARE a committee, but there _IS_ a review board in there someplace and they do do some good.

      This technology here has not yet been properly scrutinized by the community at large, sure it can get twice the data rate, but hell the official specifications could likely have done that to if they just made a few sacrifices. While technology has improved over time and it sounds like this little diddy here is an actual improvement how much of its gain is due to being improved and how much of its gain is due to fudge factor?
    • Do not forget MHz, the speed measure everyone, even people that should know better, is talking about.. stoopid engineers.
  • Is this going to be like the X2 non-standard modem but for the wireless world? If so, then as words taken by the Duke Nukem," Blow it out YER ass!!"

    That's the last we need it a half assed proprietary kinda-standard that only works well when you use their equipment.
  • 802.11a has dropped drasticly in price and continues to fall.

    There is no reason for this silly US Robotics specific solution. (except marketing to fools)

    If you want more speed, pay a little more and get 802.11a, or wait a short while for it to be in the same price range.

    Or, put your money into a better antenna on your WAP since few get the full bandwidth with existing 801.11b because of those tiny cheap antennas built into most WAPs.

  • ...to me WHY the WiFi manufacturers are focusing on speed BEFORE they worry about security? WEP is still a joke.

    • by Anonymous Coward
      run a more secure protocol like IPSec over the wireless connection, which is what they should have been doing anyways.
    • You will *never* get a secure wireless connection
      unless you encrypt the traffic using open-source
      software on dedicated hardware, end of story.
      WEP is perfectly well suited to prevent accidental
      eavesdropping, which is all that any vendor-supplied
      encrypting driver software (or hardware!) can ever
      seriously claim to offer. If you believe otherwise,
      you just bought a tanker load of snake oil, my
      friend. Closed software/hardware has been proven
      by hard experience to be so frequently corrupted
      by intentionally inserted weaknesses, that relying
      on it for security against snoops and hacks (as
      opposed to mere casual scanning) is misguided
      at best.

  • by CokeBear (16811) on Saturday April 20, 2002 @11:49AM (#3379508) Journal
    According to Mac OS Rumors [mosr.com]:

    Apple has reportedly demonstrated a 112Mbps version of its Airport wireless networking technology for educators in certain West Coast US locations, in anticipation that the new standard, which is up to ten times faster than the current Airport and can sustain original Airport speeds at distances upwards of 50% greater than today's devices. Release dates vary between reports, but the general consensus is Apple will release at least a partial implementation of this technology at Macworld New York this summer, just in time for the 2002-2003 school year buying season.
  • the cost of upgrading all of our equipment to 802.11a was astrnomical, if this is compatible with 'b' we could do our access points and all new network adapters slowly phasing out 'b' in a much more cost effective manner
  • by roguerez (319598) on Saturday April 20, 2002 @12:07PM (#3379568) Homepage
    These chips double 802.11b speeds by functioning full duplex. The drawback however, is that this requires category 5 air.

    Not all offices and homes fulfill this requirement. Location plays an important role: in the city you'll most likely not be able to communicate full duplex. In suburbs you'll have a fair chance if you're not too close to the city. In rural area's you'll most probably always have full duplex.

    You can communicate at 22 Mbps over short distances using category 4 air, but when the peers are more than a few meters apart, category 5 air becomes a must.

    Just something you might want to know before you buy these things..
  • USR OEMs their 802.11B products from Tiawanese company Eumitcom, recently bought out by Addtron [addtron.com]. The SMC, USR, Linksys, Belkin and quite a few other PCMCIA Intersil based 802.11B cards are Eumitcom WL-11000s and the access points are also Eumitcom, sometimes in different cases, sometimes not.

    Given that, is the doubling of claimed bandwidth actually USRs doing or is it Intersil's doing, Eumitcom or USR that has doubled claimed performance. Perhaps, USR is just first to market with this.

  • Market Release (Score:3, Informative)

    by hari (15720) on Saturday April 20, 2002 @12:18PM (#3379614) Homepage
    USR does not have a esitmated market release for their new cards (this from a USR sales person).

    Some other companies have also started producing the new standard, notably BuffaloTech.

    http://www.buffalotech.com/news/prelease/airstat io n2x/index.cfm

    Any insider information as to when these cards can bought at a local Bestbuy ?

  • Quoting the headline... "802.11b at 22mbps". Who the heck would want a 22 millibit per second connection? Sure, I wouldn't mind a 22 megabit per second (Mbps) connection, but that's a whole different story I guess. :)

    Here's a link [nist.gov] if you're confused or need to brush up. As well as a link [nist.gov] for extra info regarding binary multiples.

    Have a nice day!
  • Isn't Apple already shipping 54Mbps Airport cards? I thought I heard about that several months ago, but I just checked their site and it just says 11Mbps, so maybe I'm confused?
  • Sounds to me like a great alternative to 802.11a

    Rather than use a hacked non-standard modification of 802.11b, why not use 802.11g? It offers the same transfer speeds as 802.11a, but was designed to be compatible with existing 802.11b networks. So you can upgrade an existing 802.11b network to 802.11g gradually. With 802.11a, you have to rip out your old 802.11b wireless network and replace everything.
    • Read this.. especially the part about backwards compatibility [80211-planet.com]

      The backwards compatibility problem has not been solved yet for the legacy 802.11b systems to inter-operate with 802.11g. Until that happens, 802.11a, despite its problems with permeating substances such as brick and other building materials, is still the better alternative.

      This new higher speed for 802.11b mentioned in the article gives buisnesses NOW the opprotunity to upgrade their current hardware without installing a brand new system to operate in the 5ghz range.

    • If you want that just get a Cisco 1200AP, 802.11b now and a few months from now 802.11a. And when 802.11g gets ratified we will have an adapter for that too =) more info can be found here [theregister.co.uk].
    • It's funny that you call 802.11a nonstandard when 802.11g is the one that hasn't been finalized. 802.11a/b combo chipsets will arrive before 802.11g chipsets, and at that point 802.11g will be mostly pointless.

      You don't have to rip out your 802.11b network to use 802.11a; you can have two sets of base stations and migrate incrementally.
    • Umm -- because 802.11g doesn't exist?

      It's not something I'd invest in for causual,
      enthusiast, or home use, but if you have a business
      or operational requirement that can be met by the
      product *now*, you should at least evaluate whether
      it's worth spending a few bucks on short-term
      throwaway hardware (plus the admin tax).
  • lets see, at 22 millibits/sec it would take 1000 seconds to get 22 bits. I don't see how this will be a practical form of networking, it would be faster to read hexidecimal over the phone to the other end.
  • 802.11b at 22Mbps isn't new. Another company called Artem (www.artem.de) does it as well. They have this access point operates as a bridge and access point at the sametime, it splits the available 22Mbps. Where as a conventional setup would require 2 seperate set of equipment.
  • by Burdell (228580)
    Soon to be seen on the bottom of USR wireless hardware boxes everywhere:
    * Maximum speed 22Mbps, but FCC regulations restrict speed to 11Mbps.
  • Late last year Proxim delivered their Harmony 802.11a PC-Cards that are capable of "2X" mode, which yields 108 Mbps. At the time, a 2X AP wasn't available, so I tested using two PC-Cards.

    Unfortunately, the 5 GHz band used by 802.11a has trouble punching though anything much thicker than paper. I only obtained above 100 Mbps when standing within 8 feet of the other card. And that's with the antennas optimally aligned to each other.

    Repeating the tests using 802.11b cards showed vastly better range at full bandwidth, and much better fade resistance.

    We wanted to use 802.11a in 2X mode to send live 1500x1100 video about 50 feet. No way, no how.

    I'm planning to try again when 802.11g ships. The 2.4 GHz band simply has much more "punch" within the limits of the 802.11 family of protocols.

    -BobC
    • This might be more interesting as a point-to-point
      link, however, with a pair of tight yagi unidirectional
      antennae, running over open air, you can (one may
      suppose) get a VERY fat pipe over a few *miles*,
      which would otherwise cost beaucoup de argent, for
      OC-12 or dark fiber.

      Look, Ma! I made an HDTV MAN for $300!
  • by svindler (78075) on Saturday April 20, 2002 @04:21PM (#3380665) Homepage
    802.11b
    pros:
    11Mbps at low cost. Many vendors.
    cons:
    802.11b operates in 2.4GHz, which collides with among other things, bluetooth, wireless phones, and microwave ovens.

    802.11a
    pros:
    Higher speed at 54 Mbps
    Operates in 5 GHZ which is less used
    cons:
    New radios and antennas required if used to replace existing 802.11b network

    802.11g
    pros:
    Higher speed at 54 Mbps and includes backward compatibility to existing 802.11b equipment
    Antennas can be resued if used to replace existing 802.11b network
    cons:
    Operates in 2.4GHz, which collides with among other things, bluetooth, wireless phones, and microwave ovens.
    New radios required because of new chipsets

    Sorry, I can't tell you whether a or g is going to replace b, and at what speed existing b users will change to new technology.
    • You forgot something about 802.11g:

      Con: 5Ghz subject to rain-fade. Maybe not important in your silicone-valley home or office, but in places where there is rain and/or high humidity, the network will suffer a bit at the hands of the water mollecules in the air.

      Saw this on an intra-office network trying 802.11a on a day with 98% humidity. Not fun.
  • 11a,b,g factoids (Score:4, Informative)

    by xtp (248706) on Saturday April 20, 2002 @04:41PM (#3380753)
    11g is really 11a-style OFDM at 2.4 Ghz rather than the 5 Ghz band. There would be two (at least) 11g modes: a compatibility mode whereby OFDM packets and legacy 11b CCK packets coexist, and one which is "pure" OFDM at 2.4 Ghz.

    The compatibility mode adds a huge overhead to each transmitted packet. An 11g transmitter in this mode must first complete a legacy 11b RTS/CTS operation on the air which, if successful, is followed by the actual packet. Even if the actual packet were transmitted at nearly infinite bandwidth, the effective bandwidth you'd see on a connection would be quite low - think 10 Mb/s on average. That's not exactly chopped liver and its way better than legacy 11b, but it's definitely not 54 Mb/s.

    There are suprisingly large differences between 11a products, even those using the exact same vlsi chips. There are two primary reasons: differences in choice of output power amplifier (or lack thereof) and differences in choice of antenna.
    You can deduce some of what's going on by looking
    at power and sensitivity ratings in manufacturers product specs. By the way, this also a great way to distinguish between 11b products as well.

    Second generation 11a products have much better receiver sensitivity and output power than the first generation versions. And they do transmit through walls... although not concrete or metal or mirrors or some ceramics.

    The main reason why 11b can reach farther than 11a in some situations is that 11b can ratchet down to 1 Mb/s whereas 11a is defined for rates from 54 down to 6 Mb/s (11g is identical to 11a in this regard). The difference in SNR and sensitivity needed at a receiver to pick out the 11a or 11g signal accounts for nearly all of the differences in range ... and these differences are quite small if you have a good 11a radio with a good antenna.

    Thus, 11g will have the same power, SNR, and receiver sensitivity challenges as 11a in the 5 Ghz band, but will also have a small boost in signal propagation efficiency in the lower band.
    Don't get bamboozled by the hype about compatibility with 11b. Compatibility for sharing the channel does not imply that the radio properties of 11g are the same as 11b.

    Most vendors are busy bringing out 11a+b base stations and NIC cards. 11g in compatibility mode looks like a nightmare, whereas 11g in "pure" mode looks like 3 more channels of high performance OFDM if you have an 11a radio that can tune to both the 5Ghz and 2.4 Ghz bands. Aside from the higher-power outdoor channels at 5.8, this provides 11 channels for OFDM (8 at 5 Ghz plus 3).
    And this means that a group of base stations in an AP-dense environment will certainly be able to find a clear channel.

    I didn't say much about the PBCC-based 22 Mb/s products. PBCC is actually a clever design but is likely going to be overshadowed by OFDM at 5 Ghz (11a) and OFDM at 2.4 Ghz (11g variants).
    • Re:11a,b,g factoids (Score:1, Informative)

      by Anonymous Coward
      11g is really 11a-style OFDM at 2.4 Ghz rather than the 5 Ghz band.

      This is the so called "mandatory" mode of the proposed (and not yet approved 11g). What is being marketed now are the optional 22 Mbps modulations also in the draft yet unlikely to be supported by the majority of the implementations.
    • > And they do transmit through walls... although
      > not concrete or metal or mirrors

      don't forget old back-plaster-on-wire-mesh
      wallwork from ca. 1910. I think I need an *house*
      upgrade. Even with a carefully chosen and oriented
      omni on my AP, I barely get 10 meters of range at
      1Mbps!

      > or some ceramics.

      Pardon my naivete, but.... for the love of God,
      Montressor! -- who makes walls out of ceramics?!?!
      • bathrooms and Italian-style kitchens often
        have ceramic tile walls.
      • > Pardon my naivete, but.... for the love of God,
        > Montressor! -- who makes walls out of ceramics?!?!

        Bathrooms, kitchens, fireplaces, and exterior walls are relatively common in tile or brick formats. Tile is not uncommon for floors too.
      • Living in a Faraday cage can lower your wireless range. Just knock holes in the walls and build a bunch of Windows from room to room. ;-)
    • One thing you neglect to mention is power limits imposed by regulators. At least in Australia, the maximum power level in the 5GHz range is lower than the level in the 2.4GHz range (half?).

      Inverse square law.. halving power levels severely reduces the effective range of the transmitters. Also, more power is needed in order to get the same effective range at higher frequencies / bandwidths. Hence the rule of thumb that you'll need about four .11a access points for every one .11b access point.
  • USR rocks. (Score:3, Interesting)

    by Shanep (68243) on Saturday April 20, 2002 @07:50PM (#3381329) Homepage
    My USR Courier MODEM, now being about 7 years old (my model) was first a V.34 28.8k MODEM, then upgraded to V.34bis 33.6k with a simple firmware download, then X2 56k, then V.90 56k and now it seems, after 7 years, it will be upgradable to V.92 soon.

    With an Intel 80186 20MHz (25MHz for US model), TI DSP, flash memory, etc, it is one heavily over engineered beast of a MODEM.

    Does'nt surprise me that the company to get extra performance out of a technology, is USR.

  • Well, I am not sold on 802.11b anyway. There was a recent article [infoworld.com] in InfoWorld [infoworld.com] that talked about how polluted the 2.4GHz band is. There are things like fusion lighting (so cool!), microwave ovens, cordless phones, not to mention Bluetooth using the same frequency.

    Is increasing the range/bandwidth of 802.11b really a good idea? Wouldn't it be better to develop 802.11a (which uses 5.5GHz)?

10.0 times 0.1 is hardly ever 1.0.

Working...