EVDO Over 90MPH

Michael · Posted: Tue Jul 11, 2006 12:08 pm Post subject: EVDO Over 90MPH

I have only tested EVDO at 75MPH, and it worked fine. I have never gone faster, but the people at the URL below, are trying to get WAY faster.

Bullrun 2006: Blogging at 200mph

I am starting this thread to see if anyone has gone faster than 75MPH and did you remain connected?

Please don't respond that they are going above the speed limit and that is too fast.

We are actually talking to some race car drivers, who would be going faster than 90 MPH, so it would be good to know if this works or not.

Unfortunately, I don't really want to risk try this one myself Smile

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Mackieman · EVDO Junkie Joined: 31 Oct 2005 Posts: 451

First I'd like to state that I am not an RF engineer so at best I only have a general understanding of how this works. That being noted, I don't think the performance is going to be all that great at extremely high speeds. This has a lot to do with CDMA signal fade and the distance between the cell site and receiving device. Of course, line of sight comes into play as well.

The MSM chips from Qualcomm have a power curve coded into them that takes things like digital SNR (sometimes referred to as the EbNo value based on the equation to derive it) and will step itself down so as not to overpower the cell site thus ruining the spectrum for all other devices. This function is called Power Control, unexcitingly enough. This is especially significant when it comes to high speeds and signal fade.

To read more about it from someone who actually knows what he's talking about, Dr. Arthur Ross at the CDG group has a write-up on it: http://www.cdg.org/technology/cdma_technology/a_ross/cdmarevolution.asp

AgentM · EVDO Newbie Joined: 27 Jul 2005 Posts: 4

I have flown a Cessna 172 while a passenger used EVDO service during takeoff. And I can say that at ~90mph it will work, but at a little over 1000ft the service drops out. Since this was during climbout and not cruise, I don't know how much faster you can go before it doesn't work.

In cars I've seen it working at up to 85mph.

tz1 · Posted: Tue Jul 11, 2006 6:43 pm Post subject:

I would note that on most race tracks I would think the system would stay within one cell. EVDO seems to work fine at 70mph+ (as does 1xRTT - maybe I should pull my GPS logs to see how fast I was going).

MaximumSignal · Posted: Tue Jul 11, 2006 7:09 pm Post subject:

Michael · Posted: Wed Jul 12, 2006 5:55 am Post subject:

The times I have used it while doing highway driving (I was passenger), going 75 MPH, it didn't matter if I was in an EVDO or 1xRTT area, never lost the connection. I had a Magnetic Mount antenna, but no amplifier.
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emilgh · Posted: Thu Jul 13, 2006 12:48 pm Post subject:

jackrodgers · EVDO Addict Joined: 23 Mar 2006 Posts: 1131

Check my math:

95 mph = 100 feet per second or 1 ft per mph (I tend to round numbers for ease of use)

It would seem the original question would depend upon the overlap of the towers or the distance between minimal reception from the towers and the switching time between the towers and the negative disconnect time. If you could enter all of these factors into the proper equation you might get that darn aircraft carrier on top of a mountain in that high school algebra test...

rickster · EVDO Junkie Joined: 27 Aug 2005 Posts: 216

What next ? A race between Kyorcera, Novatel, and Sierra? Who can go the fastest (down the runway) and still stay connected ? Laughing

horsessmellfunny · Posted: Thu Jul 13, 2006 5:35 pm Post subject:

Sounds like an episode for the MythBusters. If somebody has access to a run way (or a large open paved field), I am sure somebody can perform these types of tests.
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jackrodgers · EVDO Addict Joined: 23 Mar 2006 Posts: 1131

rickster · EVDO Junkie Joined: 27 Aug 2005 Posts: 216

jackrodgers · EVDO Addict Joined: 23 Mar 2006 Posts: 1131

horsessmellfunny · Posted: Fri Jul 14, 2006 10:38 am Post subject:

I have no problem sitting in the back of somebody's car I would rather do it legally though.

Anyways, here is an interesting facet I came upon last night when I was landing at DIA (Denver Int' Airport) in Denver CO. The entire place is covered by EVDO, that is besides the point. I couldnt bust out my laptop during landing, so I used the next best thing. My cell phone (Yes I know "please turn off all cellular phones during landing", which is a total crock, UHF vs a 1900mhz band), I noticed as we got closer to the ground the signal was bouncing around like crazy. One minute I would have three bars, the next no bars, the next two, the next searching (we were doing anywhere from 250-400 M.P.H, I didnt have the live map on in front of me (JetBlue)). The only problem with my test is that I live in the "mile high state". So even though we were close the ground, the GPS on the Live map still showed around 6,000 feet above sea level. However, as we were about I would say 3,000-4,000 feet off the ground, service began to come back. I was even able to send a text message. As far as speeds were, at the point we were sub 200 M.P.H. I noticed the woman next to me had a Verizon phone which has three bars of service at round 5,000 feet. Mine took longer to get service. Even hovering above the ground, maybe a few hundred feet, at around 100-150 M.PH. I had perfectly fine service. I had all my bars, and EVDO. I was even able to make a call while we landed at 100 + M.P.H Now, the airport itself may only have a few cell sites (I would guess anywhere from 1-5). The entire airport, runways, and even the underground tram thingy have perfectly good service. Around the airport, there is nothing but open space. There arent any small towns, or any towns that may have cell service. I also noticed, I didnt even roam once on 800mhz Verizon. So, I think it can be done just fine at specific speeds and even altitude. I dont have the greatest way of testing, jsut breaking FAA regulations during landing...
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rickster · EVDO Junkie Joined: 27 Aug 2005 Posts: 216

Now a days surprised they didn't take you away in handcuffs and label it as an act of terrorism.