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Wi-Fi VoIP At 80 mph 142

Posted by timothy
from the 130-km/h-in-mexico dept.
fredo123 writes "Almost faster than a speeding bullet. As reported in Muniwireless minutes ago, RoamAD and WI-VOD have tested mobile VOIP over Wi-Fi at over 130 Km/h over an 8km stretch of Interstate highway somewhere near the Mexican border. Gee... I wonder what this is for?" No need to guess: according to the MuniWireless link, "the network is for public safety personnel (police, fire, ambulance and border patrol) first, with various community agencies, schools, business and local residents being added as the deployment expands beyond its targeted coverage areas."
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Wi-Fi VoIP At 80 mph

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  • by r84x (650348) * <r84x@yah[ ]com ['oo.' in gap]> on Tuesday February 22, 2005 @08:09PM (#11750749) Homepage Journal
    All hail the Information Superhighway!
  • Security? (Score:4, Interesting)

    by networkBoy (774728) on Tuesday February 22, 2005 @08:09PM (#11750754) Homepage Journal
    VOIP and wireless, now the Drug runners cn listen in on conversations. Remember some of the bigger cartels are funded as well as governments.
    -nB
    • Re:Security? (Score:3, Insightful)

      by temojen (678985)
      It's sooo much easier to eavesdrop with a police scanner.
    • Maybe this is exactly why they are looking at VOIP. VOIP is a lot easier to encrypt and secure than cellphones.

      I still wonder why they don't just use cellphones though. They would probably be a lot more reliable due to the huge infrastructure already present.

      Although I like VOIP, if I go by my own experiences using it, I can say it's not as realiable as the regular old phone system. VOIP needs a lot more technology to make it work. Eventually I see it as being better than the old phone system, but we
  • ...why? (Score:3, Insightful)

    by Anonymous Coward on Tuesday February 22, 2005 @08:09PM (#11750755)
    Why not just get them normal cell phones or something?
    • Re:...why? (Score:3, Insightful)

      by XorNand (517466)
      My guess that it's less costly than buying cell phones for everyone and then having to pay for airtime ontop of that. Plus it would be easier for that to record, log, etc. calls from HQ, regardless of who the officer calls.
    • Re:...why? (Score:3, Insightful)

      by chia_monkey (593501)
      There are a few reasons they could be trying this. One, they can deploy and control their own private network. This gives them more control over what kind of equipment they can use, how they use it, etc. Also, perhaps cell coverage blows in this area but setting up their WiFi network gives them full coverage. Also, with such network, they can also have their laptops or PDAs in the car to connect with the network and transmit valuable data (records, news flashes, etc) back and forth.
    • You need internet to get background checks, run license plate numbers, etc. The chase becomes very different if you're behind a known drug runner.
    • Three letters Q.o.S (Score:3, Interesting)

      by PaulBu (473180)
      Over IP it is "easy" (as in, standards exist) to support Quality of Service bits, and you can bet that police voice chat will get higher priority than some traveler's connection to maps.google.com.

      In cell phone network _maybe_ something like this is possible, but it would not be that easy to adjust in real time, I'd guess...

      A friend of mine told me that when he was stuck in really bad traffic on I5 (he used to commute LA to San Diego) his cellphone was almost useless exactly because everyone else was also
    • in some countries. VoIP is fine though :-).
    • Cops and Cell Phones (Score:5, Interesting)

      by ebooher (187230) on Tuesday February 22, 2005 @09:21PM (#11751366) Homepage Journal

      In response to your statement about giving cops cell phones instead of a WiFi VoIP based solution. I'd like to add my opinion to the argument. Everyone ready?! It is time once again for my Bullshit Theory of the Day . (Patent Pending, of course.)

      Let's review what the police already use to their job. Every officer where I live, be they local, county, or state, has a laptop in their car. Their radio system is trunked and the laptop receives information from the station as well as offering multiple channels for voice communication to dispatch. At this time the technology, though having been in use for a while, is still somewhat proprietary and thus is expensive. A station must buy the trunking hardware to digitize, and mux traffic, then transmit that into the ether where it is picked up by everyone.

      Let's review that last word. Everyone. Where I live it is illegal to have a police scanner in a moving vehicle. (Technically, during transport ie you just bought it, the scanner must be in the trunk.) There really isn't anything to keep normal people, as well as criminals, from listening to communications. At best, the consumer scanners don't have the proper computer communication from headquarters and most sometimes can't follow a full conversation. (The trunks switch every mic key release, and the "computer" channels change every couple of days.) But you typically can hear what you need to in order to know where your friendly neighbor Officer Mitchell is doing his job.

      Also, pushing information like that through the ether can be hit or miss in rural communities. You have to remember, that the curvature of the Earth dictates distance for RF travel. Typically 70 miles before you hit the ground itself, unless you get the signal on a high tower. However, the trunk receiver on the cars can't be equally as high (and I'm starting to wondering if satellites are not getting involved. The trunk receivers now look like XM antennas) anyway, I digress. This means, technically, that unless you are bouncing the signal to orbit and back you can not talk to a field agent that is over 70-ish miles from home base.

      Enter tomorrows technology today. Setting up WiFi that allows vehicle transmission to push VoIP so that as long as you have an internet link, you can communicate with dispatch. This will not be limited to voice. The laptops the officers use to get information about plates and criminals will also switch to this WiFi based system, and for the Law Enforcement Pointy Haired Bosses, here comes the best part. PGP type encryption for PTP tunnel building so that the information between agent and base is "secure". Technically, it would take someone long enough to get the encrypt key, even if it's measured in minutes, to keep from knowing exactly when and where officer movement is occuring real time.

      The funny thing is that I used to do tech support for Motorola, and they have a wireless networking technology that is pretty cool. We also did tech for their international customers, and had this one crazy chick from China continuously calling. Had to be two or three times a week, for about four months. Asking all kinds of technical and really out there questions about the system, and why the system didn't work. We puzzled through it and finally got an interpreter involved and found out she had these things on *trains* Apparently Asian WiFi has already been doing this moving hand off for a while now, at least experimentally. The Chinese chick couldn't understand that this product was like ethernet cabling, without the cable. Had to be aimed and left. So the control center kept losing, and then regaining, contact to trains on board systems. So people want this to work, for a variety of reasons.

      I can't even begin to tell you how often I look and listen to what is going on without thinking to myself, "My God, we're in a badly ghostwritten William Shatner novel." ... or any other post apocalyptic work that envisions the future of the world with computers in our head. Ever hear of Masamune Shirow? I'm starting to think that dude is dead on about what's coming in the next 50 years.

      • Actually any good digital scanner now can pick up trunked radio conversations very well. There are a couple systems that they can't pick up, but the Uniden BC296D or 796D can do most. RadioShack has their own model too, the PRO96 if I recall.

        The reason the antennas are so small is because the typical frequency of a trunked radio system is around 800mhz give or take. The antennas for this are comparable to mobile phone antennas. Back when the public safety systems were on CB frequencies you needed giant
      • The funny thing is that I used to do tech support for Motorola, and they have a wireless networking technology that is pretty cool.

        Are you thinking of the Tetra network? I did a lot of the migration of the managing software from american to european standards for them. It's pretty cool.

        One of the more interesting stories I got while working for Motorola is regarding the radios sold to the british police.
        As technology is getting cheaper and better it's also getting smaller - which leaves the british p

      • Oh boy, here we go... yep, this is mostly Bullshit, alright.

        First, tracking today's trunked radio systems is child's play, unless the control channels are encrypted.

        This is starting to happen, but slowly. Many agencies can't afford the upgrades necessary.

        You wouldn't believe how much simple encryption costs in commercial the two-way radio business -- it's an add-on feature, and some companies get upwards of $200 a radio.

        Okay, I have to ask this one:

        Is it legal in your area to have a police scanner in
      • There really isn't anything to keep normal people, as well as criminals, from listening to communications.

        Where I live, "as well as criminals" is redundant.
    • The cops do use cell phone tech, just not cell phones... I know for a fact in dc, mpd uses cdpd for data transmission in their squad cars. It also runs win98 :[
  • How Fast? (Score:5, Interesting)

    by th1ckasabr1ck (752151) on Tuesday February 22, 2005 @08:10PM (#11750760)
    Anybody know how fast you would have to be going (theoretically or otherwise) before the Doppler Effect makes the signal unusable?
    • by k4_pacific (736911) <k4_pacific@noSpaM.yahoo.com> on Tuesday February 22, 2005 @08:14PM (#11750810) Homepage Journal
      Fast enough that you'd be out of range of the access point before you could find out if it worked or not.

      Officer: Are you aware that you were going 0.90c in a 55 mph zone?

      Driver: Ummm... I was?

      Officer: Didn't you notice the blue shift son?
    • Depends on the frequency sensativity of the antenna/reciever circuit. If the frequency cuttoff is relatively shallow then you should be able to go pretty quick, but as it appears to be designed mainly for cars then doppler shouldn't really be a prob.
    • What might actually happen if this really occurred would be a shift in frequency, which in itself could easily be overcome by software radio. But anyway, you'd have to be going thousands of miles per second. Consider that colour is really just the differences in visible light frequency because of Doppler. The world in front of you would be turning red, and the world behind you turning blue, before you'd probably notice any problem in your connection. Even then, the TCP overhead would probably just grow.
      • You mixed up your red/blue shifts.

        Moving quickly towards a transmitter will cause the wavelength to be shorter from your perspective, and the waves behind you longer, as they "lag" behind.

        At 0.9c, thermal and some higher freq radio (like microwaves) would probably appear to you as light, while normal light would be shoved up past your perceptions.

        Would certainly be an awsome experience, as looking behind, you could "see" UV, maybe X-Rays, ect.
    • Re:How Fast? (Score:5, Informative)

      by DustMagnet (453493) on Tuesday February 22, 2005 @08:29PM (#11750942) Journal
      Light moves a lot faster than sound, so the amount of frequency shift is very small. A 2.4 GHz carrier would be shifted to 2.40000029 [google.com] at 80 MPH.

      The frequencies of radios aren't very exact, so the tuners are designed to deal with some variation. Without knowing exactly how the tuners are designed (especially the filters), I can't answer your question, except to say, a whole lot faster than 80 MPH.

      • Doesn't relativity state that light is constant speed for every observer? The speed of light is always the speed of light no matter of direction or speed? How does a doppler effect work with radio waves then?
      • The limiting factor is the amount of time it takes to lock onto a given base station, combined with the size of each base station's coverage. If using your typical home base station with its relatively small coverage, you can (in some cases) run your laptop through the area before it can lock on.

        Solution of course is to both up the coverage size per base station, and decrease the time to lock on, both of which are only slightly non-trivial to overcome.

    • by auburnate (755235)
      Anybody know how fast you would have to be going (theoretically or otherwise) before the Doppler Effect makes the signal unusable?

      No need to worry. Simply drive in reverse and it cancels the Doppler Effct.

    • The channels are normally spaced at around 8kHz or so for voice, but channels for IP will likely be far wider. Most RF front-ends are going to use some sort of AFC since that's wy more reliable and cheaper than dicking around with temperature controlled crystal oscillators etc. THis would mean you'd need a hell of a big doppler shift to make any detectable problems.

      Let's see. Supersonic aircraft still manage fine shifting digital data. So too do satellites and shuttles etc. Basically any car speeds are not

    • Re:How Fast? (Score:1, Informative)

      by Anonymous Coward
      When going over the doppler effect in my second semester of Physics, I asked the prof why our radios don't get distorted by the doppler effect when we are driving. He swiftly made me look like an ass by doing what I should have done instead of thinking out loud: plugged the numbers into the equation. As such, the equation. [thinkquest.org]
    • I recently took a 10-hour Amtrak ride and picked up > 300 access points along the way. I could never keep signal to an access point for long enough to get a DHCP lease, much less see any doppler shift.

      If everybody had a nice high-gain antenna on their roofs this would seem practical, but the little linksys dipoles aren't meant for and don't cut it for MAN'ing.
  • Public safety? (Score:5, Interesting)

    by Anonymous Coward on Tuesday February 22, 2005 @08:11PM (#11750775)
    How safe is using WiFi for such critical communication? Any kid with the right hardware can interfere with the WiFi signal. Not only that, but WiFi network congestion already creates problems for some people.

    I don't know what the rage over VoIP is -- the telephone system has worked for many, many years. We're just opening ourselves up for another avenue of attack. Can anyone say terrorists with WiFi blockers?
    • by k4_pacific (736911) <k4_pacific@noSpaM.yahoo.com> on Tuesday February 22, 2005 @08:17PM (#11750835) Homepage Journal
      Well, I'm sure police radios can be jammed too. As for traditional telephones, efforts to install land lines in the cruisers have proven unsuccessful.
    • Obviously the proper solution is for the emergency vehicles to drag a ten-mile strand of Cat5 behind them. Just imagine it -- an ambulance hurtling down the freeway with a blue network cable trailing behind, and a giant spool of Cat5 unreeling at 600 RPM... Tht tht tht tht tht tht tht
    • Redundancy (Score:4, Insightful)

      by div_2n (525075) on Tuesday February 22, 2005 @10:09PM (#11751705)
      The more modes of communication that law enforcements have available the better. I don't see why you would think that having one more is a bad thing. Remember that during 9/11 and the recent hurricanes that it was ham radio operators that did most of the communicating.
    • Re:Public safety? (Score:3, Interesting)

      by grasshoppa (657393)
      I don't know what the rage over VoIP is -- the telephone system has worked for many, many years. We're just opening ourselves up for another avenue of attack. Can anyone say terrorists with WiFi blockers?

      This I can answer:

      The office I work at has 3 locations ( soon to be four ) in wildly different area codes. We are getting larger, so we want to make our very own call center in one of the offices ( dr's office ), so the other three can simply focus on the patient.

      Using traditional methods, this would r
  • eh (Score:2, Interesting)

    by eobanb (823187)
    I dont know, I think this [apple.com] is 1337-er :)
  • In other news... (Score:3, Informative)

    by fireman sam (662213) on Tuesday February 22, 2005 @08:14PM (#11750802) Homepage Journal
    Cars have radios.

    In the harbour tunnel in Sydney traffic reports are broadcast to most frequencies in the FM scale so people listening to the radio will here them.

    Mind you it would be cool to have a VoIP broadcaster in the car so you can tell that jerk doing 20 under the speed limit to get the hell out of the overtaking lane.

    • by Anonymous Coward
      Mind you it would be cool to have a VoIP broadcaster in the car so you can tell that jerk doing 20 under the speed limit to get the hell out of the overtaking lane

      You can do this already with the mobile phone numbers on the side of tradesmen's vans.

      "Is that Jake the plumber?"
      "Yeah."
      "Then stop driving like a twat."

      They love it.

  • by ackthpt (218170) * on Tuesday February 22, 2005 @08:15PM (#11750815) Homepage Journal
    When the guy in the Luxus blasted past me at about 100 mph while blathering away on his cell call "hey fred, you should see how this thing handles on the shoulder of the road at 100 mph while one handed driving, marvelous..." he knew he could count on that keeping up with him. granted he was going substantially slower than the c (the speed of light).

    Now he's assured that he could steer with his knees and type away on his laptop while driving similarly "hey fred, how to you spell 'psychopath'?"

  • Netbacks? (Score:5, Funny)

    by Tackhead (54550) on Tuesday February 22, 2005 @08:15PM (#11750818)
    > have tested mobile VOIP over Wi-Fi at over 130 Km/h over an 8km stretch of Interstate highway somewhere near the Mexican border. Gee... I wonder what this is for?

    "DEY TUK R CONTENT!"
    - RIAA chair Cary Sherman

    "Goddamn netbacks!"
    - MPAA chair Jack Valenti

    "I! LOVE! THIS! COMPANY!"
    - Steve Ballmer, doing things you thought you could never get Americans to do for any price.

  • oh please! (Score:2, Insightful)

    by Jailbrekr (73837)
    I predict that in a week, we'll be seeing articles about how they are stuffing mobile VoIP systems into pizza boxes with neon lights illuminating the insides.

    OH COME ON. Report things which are relevant and unique, not 'omg its a wireless link that works at 80mph!'. Cel service works at speeds far faster than that (just ask anyone who used a cel phone on a plane before the ban).

  • by winkydink (650484) * <sv.dude@gmail.com> on Tuesday February 22, 2005 @08:23PM (#11750890) Homepage Journal
    Many frequent flyers have reported good results using Lufthansa's wireless internet in the sky with Skype. By contrast, doign this on a highway just seems a little humdrum.
    • Many frequent flyers have reported good results using Lufthansa's wireless internet in the sky with Skype. By contrast, doign this on a highway just seems a little humdrum.

      Isn't the signal actually relayed to/from the jet?

    • A lot less in the way of the signal when you're in the sky.
    • :-) given the choice I'd rather trust an ambulance to pick me and ferry me to hospital and do some data transmission on the way (e.g. send forward info about my condition to emergency doctors) if I was bleeding to death, than rely on Lufthansa to park a jet outside my house and then get downtown to the local emergency surgery :-)

      Ambulances /other emergency service scenarios more humdrum but I'm happy if people are spending time and money working it out :-)

  • wargames (Score:3, Funny)

    by lokalhost (666083) on Tuesday February 22, 2005 @08:23PM (#11750898)
    So how long before the wifi network gets a counterstrike server?
  • It sounds faster when given in kph (Thousand P's per Hour).
  • YASUOM (Score:5, Funny)

    by DoubleD (29726) on Tuesday February 22, 2005 @08:32PM (#11750967)
    Yet another stupid unit of measure "almost faster than a speeding bullet."

    Also what the heck kind of slow lazy bullets are almost slower than 80mph.

    because I was curious I checked out the speed of a bullet. referencing this link:
    http://hypertextbook.com/facts/1999/MariaPereyra.s html [hypertextbook.com]
    puts the lower end of bullet speed at about 750mph and the upper end at 6700mph.

    At least "almost as fast as a carrier pigeon in a tornado" would have been more accurate.
  • by istewart (463887) on Tuesday February 22, 2005 @08:38PM (#11751032)
    Make it work at 88 miles per hour and then they'll be on to something.
  • by StikyPad (445176) on Tuesday February 22, 2005 @08:44PM (#11751082) Homepage
    No need to guess: according to the MuniWireless link, "the network is for public safety personnel (police, fire, ambulance and border patrol) first, with various community agencies, schools, business and local residents being added as the deployment expands beyond its targeted coverage areas."

    Okay, what sort of alternate universe is this? This is the second story today where the submitter hasn't RTFA, but now this? Now the EDITOR actually read the story.

    Is anyone else feeling just a little freaked out right about now?
  • 80mph in Mexico (Score:1, Informative)

    by Anonymous Coward

    VOIP over Wi-Fi at over 130 Km/h over an 8km stretch of Interstate highway somewhere near the Mexican border.

    Gee... I wonder what this is for?

    I could've used that last week... was visiting family in Mexico, and the border is a no-man's-land of U.S. and Mexican cellular zones fighting it out. At times I haven't been able to make cell calls 1 mile inside the U.S. because stupid TelMex signals were overpowering the weak AT&T signal down there.

    Plus the 80mph thing is not so outrageous. My SUV s

    • "TelMex" is not a cellular company. It is a telephone/internet/long distance/frame relay company. You would be probably getting signal from TelCel, Telefonica or Pegaso, plus the fault wouldn't be from any of those companies but from AT&T for providing such a low signals at that zone. Basically at the US/Mexico border, the company that provides stronger signal owns the area.

      I used to live at the border (about 5km inside mexico) and I was still able to put calls thru Nextel and I could use my Telcel pho
  • that travels at 130 Km/hour (81 miles per hour) has definite problems, besides that of the kids needing better connectivity for their World of Warcraft sessions.
  • The current problem with WiFi VoIP is that you need a really big handset.

    What I really wanted was to use my mobile phone and make VoIP calls over bluetooth. Yes, the bluetooth range sucks, but at least it's a technology ready to use by my mobile. All it needs is an app (say J2ME) that handles the VoIP at the client side.

    - or -

    rather than use the mobile phone, use a bluetooth headset and link it straight to the bluetooth AP. The problem then being headset configuration and call making/receiving. Perha
    • I really don't think you mentioned Bluetooth quite enough...
  • what this could do at _88_ mph with a 1.21 gigawatt spark?
  • Can you get pulled over for this? or is there no speed limit?
  • looks like my car is gonna have to break down there often
  • Raleigh Fading (Score:5, Interesting)

    by renehollan (138013) <.rhollan. .at. .clearwire.net.> on Tuesday February 22, 2005 @10:01PM (#11751650) Homepage Journal
    I remember implementing communications code for packet radio modems way back in th' day... circa 1989, at 1200-9600 b/s.

    The big problem with mobile radio sysems (particularly in urban environments) is Raleigh Fading, otherwise known as "picket fencing" noise. What happens is that one receives the radio signal via multiple paths, reflected from buildings in the "urban jungle". Sometimes these signals interfere constructively, and sometimes destructively. When driving, in an urban environment, one tends to move from areas of constructive to destructive interferance and back again, on a surprisingly regular basis. The effect is called "Raleigh Fading", after the statistical distribution of constructive and destructive zones. On an analog voice radio channel, it sounds like someone running a stick past a picket fence, hence "picket fencing noise". Of course, in environments with less opportunities for radio signal reflections, the effect is less predictible, but it still happens.

    Naturally, transmitting and receiving a checksummed packet while driving through one of the areas of destructive interferance is, well, a challenge. If the non-acknowlegement retransmission rate, and speed are just so, you'll never get a packet through.

    There are two ways of dealing with this: spacial diversity antennas (multiple antennas separated at carefully computed distances so that one is always in an area of constructive interferance when the other is in an area of destructive interferance), and interleaved error correcting codes. The spacial diversity antennas work well at the higher VHF and greater frequencies, because the distance between individual antennas isn't all that great. However, at frequencies of around 150 Mhz and lower, the required distance between individual antennas is too great to allow for automobile mounting. So, one uses interleaved error correcting codes (generally Reed Solomon), and hopes that one travels between zones of constructive and destructive interferance "fast enough". Yes, there is a mimumum driving speed related to data rate, carrier frequency, and error correcting code and interleave chosen, below which the system would not work. One generally picks an error correcting code so that the minimum speed is low enough that it would be practical to stop in an area of constructive interferance.

    As I recall, at least one rural police force in Quebec, Canada was outfitted with the equipment we produced. Needless to say, the fade rate was not a problem when "Enos" (well, Jean-Guy in the Quebecois version of "Dukes of Hazzard") was in in "hot pursuit".

    No, we did not interface the modem to the cruise control to ensure the vehicle was moving "fast enough", though it was damn tempting...

    Of course, at modern data rates and carrier frequencies, spacial diversity antennas are a far better choice to combat this problem (and why wireless data network interfaces usually have two antennas).

    • So you are saying that next time police stops me for speeding I just say to him "I'm trying to get rid of the interference" :)
      • I guess you could try that excuse :-)

        However, bewarned that (a) we chose error-correcting codes where the minimum speed was something like 20 km/h (about 16 mph), and (b) modern equipment works at sufficiently high carrier frequencies that spacial diversity antennas can be used instead.

        So, unless you were speeding in a parking lot, or 15 mph school zone, driving a 15 to 20 year old car, with equally old radio equipment, and likely a Zenith clamshell laptop running DOS (yes, been there, done that -- exce

        • Sorry but I missed the part where anyone was talking about analog signals. If i can sit in the middle of the Hampton Roads Tunnel and surf the net on my blackberry, then a cruiser can do VoIP through midtown Manhattan...without looking like a porcupine in heat.
          • It's all analog at some level (unless you get to the quantum level).

            But, things work for the cop because s/he is using spacial diversity antennas: either at the transmitter (rare), or at the receiver (common). At the carrier frequences these services operate, the individial antennals (three are typically used, though two can suffice), need only be inches apart, not feet, and are often in a common housing.

  • Remember folks, it's illegal for you to talk on a cell phone while driving, but it is perfectly ok for cops to type on a terminal while driving 80mph!

    Shouldn't the same rules apply to everyone?

  • In other news... (Score:3, Insightful)

    by po8 (187055) on Tuesday February 22, 2005 @10:37PM (#11751901)

    • WiFi VoIP tested in cold weather.
    • WiFi VoIP tested for use during full moon.
    • WiFi VoIP: can it work for brunettes?

    Seriously. What possible reason would WiFi VoIP work any differently at 80MPH than in the rest Earth reference frame?

    P.S. Before you say "Doppler Shift", go do the math and examine the chip specs. We have: we hope to shortly demonstrate 802.11b at Mach 2 [pdx.edu].

  • by Keruo (771880) on Wednesday February 23, 2005 @03:01AM (#11753190)
    You really really really don't want emergency service calls routed over packet switched network.
    The network described is best effort service with no built-in QoS features. Yes, you can set the qos bit, but can't users do that same with custom voip software aswell?
    I'd perfer my emergency calls routed through circuit switched network, since there's actually chance for them to get through in it.

    And what's with this reinventing the wheel again?
    TETRA is already existing standard for public safety communications, it still works at speeds of 200km/h, circuit switched, encrypted secure transfer medium by default, nationwide user groups, integraded ptt in devices etc etc.
  • Actually it is funny that this topic has just surfaced, Im in the process of finishing a thesis studying Mobile IP actually MIPv6 and its capabilities, you'd be extremely surprised what you get when you start putting a few things together, using 802.1x and IPsec we can ultimately reduce handoffs between access routers on the same prefix to ~50ms or less and thats with an 802.1x authentication!! Sutff like this is really possible and can be done today without major infrastructure changes, we just need to sta
  • In the UK that's about average speed for the motorway(highway).

    We'd need the thing to work up to at least 150mph so the fast cars can still get comms at 'chase speed'. (too many Subaru Imprezza turbos on both side of law).
  • The main thing about this is how they have sucessfully made handover between each base-station along the route without cracks, mutes and dropped calls.

    Would be interesting to see these guys go up agains the EU DECT-standard.
  • While they were using a different communications mechanism, industry groups, in testing future ODBIII implementations, have already proven they can read out emissions data from automotive computers as vehicles drive by transponders embedded in the side of the road, in rush hour traffic, on a four lane highway, at 80 mph.

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