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Handhelds Hardware

Roaming WLAN / GPRS 52

Posted by CmdrTaco from the bring-it-on dept.
Obnoxio The Clown writes "The Register has an article on breaking technology which will (theoretically) allow roaming between WLAN and GPRS (and presumably 3G when it gets here)." At long last, I'll be able to delete my spam from everywhere!
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Roaming WLAN / GPRS More

Roaming WLAN / GPRS

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  • 3G? (Score:2, Interesting)

    by Max Romantschuk ( 132276 )
    I don't know about you guys, but I feel like it's more likely that this kind of technology will become 3G than the third generation mobile networks themselves.

    • Re:3G? (Score:5, Interesting)

      by Michael Hunt ( 585391 ) on Tuesday April 08, 2003 @07:28AM (#5685289) Homepage
      802.11 as next-generation cell? Unlikely. The contention arbitration mechanisms aren't there, and the protocol was never designed to be used over a distance of greater than about 500 metres.

      People like Karlnet (with TurboCell) have tried to push this envelope, largely unsuccessfully. A company I was involved with (who shall remain nameless, as I still own some of their stock) tried to push these technologies as 'long distance wireless multipoint technology' and it plain sucked at it. Square peg, round hole.

      Comparing 802.11(a,b,g, or even TurboCell) with 2.5G/WCDMA/GSM/whatever is like comparing shared 10 megabit ethernet with a DS1. The latter has fixed timeslots to avoid two, three, or 30 devices contending for the available bandwidth. Each device is allocated a section of spectrum (bandwidth in the case of a DS1.) 802.3 has CSMA/CD which guarantees that all devices can continue speaking in the presence of collisions. 802.11 uses an even more perverse scheme referred to as CSMA/CA (collision AVOIDANCE,) which avoids collisions in the unlikely event that all nodes can see each other.

      Incidentally (I will get to the point eventually, I promise,) cell works by dividing the available spectrum into timeslots, much as a DS1 does. The three most common division mechanisms are FDMA (frequency multiplexing, in which case every device gets its own unique, but very small, section of spectrum), TDMA (timeslot multiplexing, in which all devices contend for the same spectrum, but the timing guarantees each device uses a given slot,) and CDMA (code-based multiplexing, i'm honestly not sure how this works. Qualcomm own a patent on much of it, paid for by the American taxpayer.)

      Since each device is guaranteed, deterministically, not to step on the toes of any other device, the devices don't have to be able to see each other in order to avoid major contention issues.

      Now, back to 802.11 and CSMA/CA. The CSMA/CA algorithm guarantees that a given device won't hog the spectrum when it can hear other devices contending for it. If you move some of these devices such that they can't hear each other, the theory has it (which is why you have a wireless net running in infrastructure mode with a base station) that the base station will repeat communications from one node to the others. However, node A won't have any way of knowing that node B is after some spectrum, and vice versa. End result, the node which is closer (think physics and speed of light) will get the lion's share of the bandwidth.

      Based on these assumptions, as well as the fact that 802.11 operates in spectrum used by microwave ovens, obscure military devices (the UNI/I 5.8 gig band,) and some satellite stuff (sideband interference 100MHz up the scale), 802.11 will never replace a properly thought out deterministic voice-grade protocol.

      Now, *MDS on the other hand....

      • Re:3G? (Score:3, Insightful)

        by Max Romantschuk ( 132276 )
        802.11 as next-generation cell? Unlikely. The contention arbitration mechanisms aren't there, and the protocol was never designed to be used over a distance of greater than about 500 metres.

        Your comment is no doubt very convincing. On the other hand, IDE was never designed to run at 133 MHz. I realize the analogy is poor, but we've managed to scale technology beyond the wldest dreams of the original designers before... providing the demand existed, that is.
        • I'm not for the life of me saying that an 802.11-like protocol won't do the job. I'm merely contending that 802.11 in its current state won't.

          You wouldn't plug your brand new 120GB WD Special Edition into a second-generation ISA IDE card, either (well, not and expect it to move more than about 2MB/sec.)
    • I don't think so. It's just that gprs networks have been around a little longer than the 3G networks, and as a result have had more applications developed for it. You wait for a few months, we'll be seeing the first killer apps for the 3g phones that are getting widespread adoption.

      Then again, none of my other prophesies have come to pass ;)

    • Re:3G? (Score:4, Informative)

      by rcs1000 ( 462363 ) <rcs1000.gmail@com> on Tuesday April 08, 2003 @07:35AM (#5685308)
      It's funny you should mention this, because I just got my 3G phone working yesterday. It sucks.

      (For the record I am using Hutchinson's three service in the UK with the NEC e606 phone.)

      Compared to WLAN access (even at its slowest), 3G crawls. And - frankly - you've got a better chance of finding a WLAN access point than consistent 3G coverage.

      WLAN does, however, have to jump through a few hurdles before it can approach what the cell phone networks do. Firstly, it needs some kind of rationing. At CeBIT my laptop could always see about 20 WLAN networks at any time. Surprise, surprise: none of them worked as they all interfered. At least with cell-phones, one person has a working service.

      Secondly, there is no support for "handing-off" between base stations. Given the limited range of an AP, this is a must. (It's also not simple: you need to maintain your IP address as you jumo between APs, which requires a unified backbone network - which 3G has, but WLAN does not.)

      Thirdly, it needs various WLAN access point owners and cell-phone operators to communicate. And this is where I break down laughing.

      I wish, I wish WLAN could come and allow me to throw away my terrible NEC e606. But I just don't see it.

      • Re:3G? (Score:3, Interesting)

        by Michael Hunt ( 585391 )
        Handoff between base-stations would require one of two things in order to work:

        a. the 802.11 infrastructure was all bridged, possibly with some interesting VLAN setups (although this would largely be useless, as you don't win anything by VLAN'ing on a shared network)

        b. device advertises its address as a 32-bit prefix to each base station it encounters, which then redistributes this into the network's IGP. This would not scale very well either.

        An ATM-based wireless protocol would sort out these issues as
      • > Secondly, there is no support for "handing-off"
        > between base stations.

        Not quite true.

        802.11f (Inter Access Point Protocol) defines an interoperable solution for that, some manufacturers already provide roaming capabilities in their equipment. I actuall roam almost every day (walking in the office) without problems. Heck, even Ethereal can decode IAPP ;)

        As for handing over between various providers, there is something called Mobile IP that allows the user to be seen under the same IP, no matter i
      • 3G has just started out, and I'm sure it will get better. As long as WLAN doesn't support any kind of hand-over (between diffrent nodes) you will never have any mobility with it. I would like to think as WLAN as a extension to 3G not a competitor. regards, Magnus

  • Spam (Score:5, Funny)

    by Neophytus ( 642863 ) on Tuesday April 08, 2003 @07:17AM (#5685245)
    At long last, I'll be able to delete my spam from everywhere!
    Thats my kind of night taco! An evening in the pub with a drink in one hand and a PDA deleting spam in the other... I mean, girls come second to spam any day!
    • "girls come second to spam any day" And my spam is full of pretty girls :-)
      • Yeah? Mine is consistently telling me that my ding-dong isn't long enough, yet I still seem to get the pretty girls, and not to mention Viagra...

        So I need work on my willy, but I still get bucket loads of 'Hot Teens'. Yet I need Viagra. What a blow for targeting advertising.

  • Bandwidth (Score:3, Interesting)

    by rf0 ( 159958 ) <rghf@fsck.me.uk> on Tuesday April 08, 2003 @07:19AM (#5685252) Homepage
    Cool now does that mean instead of paying for airtime on my mobile I can route my calls via my ADSL using VoIP + right software? Now that would be cool and save money

    Rus
    • If you're at home, sure - if you're roaming on GPRS, well, you'd probably end up spending 100x more on the GPRS chargers, unless there are unlimited GPRS plans around... *drool* (there aren't in the UK)

  • 3G.. (Score:3, Funny)

    by Anonymous Coward on Tuesday April 08, 2003 @07:20AM (#5685255)
    will be finally implemented 3 generations after mine?
  • From the article -

    "What remains to be sorted, it seems, is a universal smartcard carrier - at the moment, the SIM card is the only possible authentication device, and it's by no means universal. Most smartcards are credit card sized, and almost no GSM phone now accepts SIM carriers of that size."

    Yeah, but have you seen the size of the current crop of 3G phones?!? They'll definitely be able to hold a credit card sized sim.

    • Welcome to Europe... (Score:5, Interesting)

      by MosesJones ( 55544 ) on Tuesday April 08, 2003 @07:52AM (#5685394) Homepage

      Anyone who thinks the smart chip is credit card sized is a moron. My mobile has a smart card inside, its the same size as the smart card in my credit card... BUT NEITHER OF THEM ARE THE SAME SIZE AS THE CONTAINER (i.e. credit card or mobile).

      Sheesh, you can get smart cards that need all that space for extra memory, but most are tiny things with the external contacts making up most of the support.

      The mobile IS the smart card device that can be carried around as it has all of the required elements

      1) Contains a smart card
      2) Able to interact with other devices over multilpe mechanisms (GSM, IrDA, Bluetooth etc)
      3) Smart card can be replaced as require.

      Smart cards are NOT credit card sized, that is the plastic that holds them. Its sort of like saying that starter motors are car sized.
    • GSM phones have always had a SIM card.

      they are about the size of a dime and as thick as a credit card.

      i don't think the author of the article has the slightest idea of what she was writing about.

      what remains to be sorted is convincing the operators - who own the SIM cards - to allow them to be used for communications over WLAN networks where they presumably will not receive any air time revenue.

  • 3G is already here (Score:2, Funny)

    by Anonymous Coward
    ...and presumably 3G when it gets here

    3G is already here

    http://www.three.co.uk/

    • How is that +2 funny? It's real - three.co.uk is the first 3G mobile operator in the UK, but sadly the only handsets available are ugly as sin and probably lack some of the key features that later phones will have.
      • the only handsets available are ugly as sin and probably lack some of the key features that later phones will have.

        This "drip-feeding" of features has a posibility of turning off the key users. Most early adopters are the enthusiasts, with out them, the product will flop. Right now, I've a 2.5G SmartPhone that does pretty much everything for me that a mobile could do, excepting maybe video phone, but what use is that on a mobile platform? If I were to move to 3G, I would actually have to downgrade my pho


  • Now I know this is wonderful and amazing, and totally different that today where you can

    1) Buy a WLAN card for your laptop
    2) Buy a GPRS card for your laptop

    Set WLAN to be the default, set GPRS to be "dial when network connection not available"

    Which means that a few seconds after moving from WLAN your GPRS connection will become active.

    I _know_ they are talking about being a bit smarter than this, but this is what anyone can do today, in fact newer laptop have WLAN built in so all you need to do is buy t
  • Don't give in, it's a secret plot to monitor everyone.

    /end conspiracy theory

    On a serious note. How is privacy affected by "new Technology". Something like "Freedom Net"(forget if it was actaully called this) would be nice for this.

    -Rob
  • Can't mobile IP already do this? Surely this is more about the billing, allowing the network to keep charging the user per octet for some 'service' even when they go onto a wireless lan, which may or maynot be free to use. Likely the network hosts the mobile IP home agent on their network somewhere and charges the subscriber per octet forwarded through it to outside their network....

  • Market? What market? (Score:4, Insightful)

    by Rick the Red ( 307103 ) <Rick.The.Red@gm[ ].com ['ail' in gap]> on Tuesday April 08, 2003 @10:14AM (#5686131) Journal
    I worked on a similar project at a major cell phone company. It started over a year and a half ago, and quickly fizzled. Why? There's little market. We had a solution but no customers. Wow, you can be connected to your corporate LAN via 802.11 in the building, and seamlessly transition to GPRS when you leave the building, without losing your connection! Sounds great, but how many people do you know who access their corporate network via their cell phone, or who actively work on their laptop while they're walking out of the building? The only promising application for this technology was PDAs, and people don't run enterprise applications or work corporate spreadsheets on their PDAs. The "seamless handoff" tech is cool, but there's just no market.
  • The Register has an article on breaking technology

    Is it just me, or does this sound like a bad thing?

    Sean

  • CDMA'z already going it (Score:1, Informative)

    by Anonymous Coward
    This capability is already available in CDMA... oh well.
    • If you had RTFA, you'ld know that the point of the technology is rather on the billing and WLAN-side than on the GPRS/CDMA/3G/Your Favorite Mobile Data Standard Here side.
  • Can I make Voice over GPRS connections, a la VoIP with WCDMA? Would a VoGPRS session persist across t-net's kind of GPRS->WLAN transition? That kind of roaming alone would seem the killer app for VoGPRS.

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