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Signal Handoff Could Mean Roaming VoIP over WiFi

Posted by timothy on from the run-your-own-cloud dept.

wassup writes "According to this article in MIT tech review (and here), researchers at University of California San Diego have developed a technology called SyncScan that will reduce handoff delay in WiFi networks to a few milliseconds. VoIP roaming will be here soon!"

22 of 91 comments (clear)

  1. voip-a-doip by Anonymous Coward · · Score: 2, Funny

    Can you hear me now? Good, I'm wartalking

  2. just wait... by jleq · · Score: 5, Insightful

    ... until the wireless providers find out. We will finally break the speed of light when all of their lawyers run crying to the FCC and FTC. "OmG, unfair competition!" This, combined with municipal wi-fi, could lead to a much less expensive wireless future for us all. Yay!

  3. Roaming VOIP by ABeowulfCluster · · Score: 2, Funny
    1. attach phone to toolbelt.

    2. duct tape a voip converter box to toolbelt.

    3. add a power supply (solar panels or car battery

    4. Save money on your mobile voip setup.

    5. Profit!

  4. What about TCP/IP handoff? by hgilde · · Score: 5, Informative

    Last I checked, VOIP uses TCP sockets. When you move between WiFi base stations, you first must discover your new DHCP server, then get a new local IP address, then reconnect to the VOIP server.

    This will definitely be an annoying delay.

    1. Re:What about TCP/IP handoff? by jleq · · Score: 3, Insightful

      True... unless, of course, the access points are all on the same network (and therefore use the same DHCP server)

    2. Re:What about TCP/IP handoff? by c_g_hills · · Score: 5, Informative

      This is why IPv6 is a much better network (layer 3) protocol for VoIP as it supports mobility natively, allowing TCP and UDP sessions to be maintained when roamning from one network to the next.

      In fact, the Internet Society point out that IPv6 is necessary for mobile and wireless internet.

    3. Re:What about TCP/IP handoff? by LordoftheFrings · · Score: 4, Interesting

      VOIP does use TCP sockets for the initial data setup but UDP for actual voice streaming. This problem could be solved with some overlap of the wireless access point ranges and two network interfaces. One could get a DHCP lease on the upcoming network while the other still streams, and then once the first network is out of range instantly switch over to the other interface. Just a thought.

      --
      Canadian Cynic, canadian politics is less boring than you
    4. Re:What about TCP/IP handoff? by templeton008 · · Score: 3, Informative

      sip can go over tcp or udp, it's most often used over udp though. The actual rtp audio stream goes exclusively over udp to minimize delay/complexity (it doesn't matter if some packets get dropped).

    5. Re:What about TCP/IP handoff? by zm · · Score: 2, Informative

      VoIP works on UDP, not TCP. WIFI association and the address disovery can be done while the call is still in progress (ever heard of having two addresses on the same interface?). Then there is almost no impact on the media path. See for example http://sipquest.com/sipquest-software-wifi.htm.

      --
      Sig ?
    6. Re:What about TCP/IP handoff? by Alrescha · · Score: 2, Informative

      "Last I checked, VOIP uses TCP sockets."

      The last time I checked, my VoIP infrastructure used UDP.

      I suspect that there are enough implementations out there now to make 'VoIP' a useless term for determining the underlying technology.

      A.

      --
      ...bringing you cynical quips since 1998
    7. Re:What about TCP/IP handoff? by Anonymous Coward · · Score: 3, Informative

      You are correct about the TCP/IP issues, but the design for multi-AP networks
      is to have them all on the same subnet. Then the act of roaming between APs
      is scoped to L2.

      That leaves a couple different sources for delay/glitch:

      One is if the wireless client were to set the WiFi interface "down" upon
      dissassociating with the initial AP, then setting the interface back "up"
      once it associates with the next AP. This may have the affect of triggering
      the IP stack to release it's address information, and then restart a DHCP
      transaction when the interface comes up. This sort of thing should be easy
      to avoid in a WiFi VoIP client though.

      The other stickler is WiFi authentication. Most WiFi users are used to WEP
      with Open authentication, which is more or less instant. But a modern,
      enterprise-level network with modern authentication features (802.1x/RADIUS)
      makes the authentication step not-so-instant. Cisco has some proprietary
      features in their APs to make roaming in such an environment a much faster
      operation (they basically use an authentication "proxy" of sorts). I follow
      this stuff because I'm helping develop a competing AP at the company I work for.

      I'm glad to see some new ideas come out, but from looking at the article, it
      doesn't look like this new research is taking the full context of the wireless
      network - including the authentication scheme - into account.

  5. I just hope by Pinefresh · · Score: 4, Funny

    this research wasn't randomly generated

  6. "checks ... only at the precise times ..." by Anonymous Coward · · Score: 2, Insightful

    The sync up is interesting.
    If you're on one of 11 channels and you spend 10ms every 100ms checking for a beacon on each of the other 10 channels it takes you one second to check 1/10 of the channel-beacon slots. So, after 10 seconds, you've got all slots nailed down to 10ms windows. Once you have all the slots you can update the signal strengths on the active channels once per second and discover any new beacon within 10 seconds.
    Yep, pretty cool....

  7. Why do people love wifi everywhere so much ? by Anonymous Coward · · Score: 2, Insightful

    It's just one big LAN and easy pickings for 1337 kiddies with packet sniffers.

    And why would you want to join an untrusted network anyway ? So the admin of that network can keep nice juicy logs of everything you are doing ?

    Strange.

  8. Don't worry... by wingsofchai · · Score: 5, Funny

    I'm sure the FCC will step in and protect us from this innovative and helpful new technology with plenty of arbitrary regulations that make little or no sense...

    --
    Reading at high threshold levels is group-think.
    1. Re:Don't worry... by Saeger · · Score: 3, Insightful
      It's just greedy human nature. Machiavelli put it best 500 years ago:
      "Innovation makes enemies of all those who prospered under the old regime, and only lukewarm support is forthcoming from those who would prosper under the new."
      I've had that quote up on my wall for a number of years, since it helps to remind me how consistantly people -- and especially the cashcow status quo -- resist any disruptive change that shifts net benefit/power to a greater number of people.
      --
      Power to the Peaceful
  9. NO thanks by Timesprout · · Score: 4, Funny

    I will stick with my current approach of having a team of engineers follow me around 24/7 laying cat5 cable for my skype connection.

    --
    Do not try to read the dupe, thats impossible. Instead, only try to realize the truth
    What truth?
    There is no dupe
  10. Obvious really by smoker2 · · Score: 2, Interesting

    This idea is obvious in retrospect, as all really useful ideas are. Its basically a modification of the normal behaviour to take into account recent changes in WiFi usage. Instead of intensively hunting for a new AP when the signal has nearly died, the system checks more regularly, but much less intensively, so that it is ready to switch at a moments notice.
    I hope they get paid for this.
    Of course, this will only work for APs that you have legitimate access to, so if you come within reach of a restricted AP (on a different net maybe) then it can't handover to that, so "roaming" is perhaps too strong a word.

  11. VoIPoWiFi by t_allardyce · · Score: 2, Interesting

    I don't know about the name. Phone companies have always worked on the basis that they had something we needed - a network of transmitters maintained 24/7 and connected to the general phone system. Local calls in cities don't need to touch the phone system, or even the internet, just switch on some cheap routers and let them create a city wide network at practically no cost - it would be like one big cordless phone, sure it would probably be patchy, but people would live with it for most calls - which in the city go something like:
    "hey where are you? im outside x"
    "oh im like 1 minute away from x, stay there"
    and text messaging would work fine. If there was congestion or you wanted to call a land line then your phone just switches to your usual network and you pay for the call. Personally i think this would be good for everyone including the networks - that push-to-talk bullshit is a lesser version of this.

    --
    This comment does not represent the views or opinions of the user.
  12. WiMax will break the cell operators backs by cpeterso · · Score: 3, Interesting


    Cell operators like Verizon spend BILLIONS on proprietary "3G" networks. Their networks require lots of towers, yet have poor coverage and lots of "signal shadows". WiMax access points have ranges from 30-50 MILES and don't have the same signal shadow problems. WiMax phone networks will steamroll cell operators with cheap networks yet better coverage and service.

    --
    cpeterso
    1. Re:WiMax will break the cell operators backs by adolf · · Score: 2, Informative

      Not to piss on your wet dream, but:

      WiMax supports huge distances, sure. But in order to avoid needing a line of sight with the tower, you need to use low frequencies - that multiple-tens-of-GHz mumbo-jumbo is useless for penetrating things like trees, buildings, and cars.

      Thankfully, old analog TV spectrum (such as the lower 700MHz band) is suitable and available for use in this way.

      But realize that there's only so much information bandwidth that can be squeezed out of a slice of spectrum, and that the further you cast your signal, the more devices that are likely to be competing for that available bandwidth. So, "30-50 mile" range may not be as advantageous as you might think.

      And it's all licensed and auctioned off to the highest bidder, in much the same way as existing cellular frequencies were/are. The end-user equipment doesn't even exist yet, and there's certainly no economy of scale advantage over traditional cellular phones (and there may never be, depending on how this spectrum ends up actually being used).

      To top it off, it's extremely likely that the existing rules governing handheld cellular telephones to 600 mW ERP will be carried over to the lower 700's devices, if the rules aren't applicable already.

      And -that- means that you'll never get more than a few miles of range. Which means again a landscape peppered with hideously expensive towers for reasonable coverage patterns.

      Which is just like cellular phones operate, today. Except it's WiMax instead of CDMA.

      On the other hand, it will open up the market to new players. Which will increase competition, and probably lower prices overall.

      And in any event, the technology itself is not any cheaper simply by virtue of NOT being CDMA, GSM, or PCS. It's still governed by physics, the FCC, and market forces.

      --
      Kid-proof tablet..
  13. Actually by bluGill · · Score: 4, Insightful

    Actually VOIP over WiFi is more likely to be useful in deserts and other remote areas because those who care can setup their own network. It might not be worthwhile for a cell phone company to put up a cell tower, but a farmer can put a WiFi station on his silo and get pretty good coverage of his ranch. Sure it won't have a large coverage areas, but it covers his needs.