How Much Can Your Datacard TAke

[Mikey Gribble]

I am still trying to figure out the details of my equipment situation this year and although I"ve made a lot of progress, I still have a ways to go. I have one of those verizon little white usb aircards for internet. My amp should be here by the end of the week god willing. I want to be able run spotter network, grlevel3, stream video and then look at regular data on the internet. Do most people run that many things on a data card at the same time without problems and if your signal gets weak what order do the programs start dropping in?
For example last Monday I just had my aircard with an external antenna. I was running spotternetwork, getting on the internet and grlevel3. If my signal got weak I would drop grlevel3 but spotternetwork would keep going. The main thing I'm worried about is streaming video. Is that simply too much of a load on the aircard? I swear I've heard people say they run that and more on one computer so I would think it could be done. If it comes down to it I would place my priority on keeping the spotternetwork and video stream going because I have XM as a radar backup. Any advice or input on the matter would be appreciated. It will help me from having to learn through trial and error, which I've already done enough of this season. thanks in advance.
edit - how much of a toll does streaming video take on the air card? Is it similiar to grlevel3 where it is going to take a fairly strong signal to work?

 

[Wes Carter]

Last year we ran a vehicle-to-vehicle wi-fi network with one pc running GRLevel2 and another running WeatherTap Radar Lab. I had Spotter Network on mine and other people were accessing SPC data and other stuff. It was almost all going through one Alltel card. I had a Verizon card we used for backup, but only a couple of times when we were out of Alltel service. We didn't do video, but what we had worked OK. We are going to be doing live feeds this year though.

 

[Scott Roberts]

It's not so much the card itself as just what service area you happen to be in at the moment. As an example: last spring, I could consistently get near-broadband speeds off the AllTel data card I have along highway 50 from Hutchinson to St. John. It was not uncommon when running thorugh there to be able to pull up 3 GRLevel3 instances, run SpotterNetwork, push my GPS info to another server, and have as many as two browser sessions going before I'd start having to wait on data to come in. The speeds were running in the neighborhood of 3MB/s (download), believe it or not. That's an EVDO RevA area. I consistenly get 1.5 to 2Mb/s here at home -- use the data card as backup when my cable 'net is out.

Contrast that to US 166 three weeks ago between I-35 and Ark City. 3/4 of the time the card would not authenticate to whichever system it was trying to reach, and when it did I had 1x speeds at best. I was down to a single GRLevel3 and SpotterNetwork, and GR was not always able to pull in my Allisonhouse data feeds consistently. Never hit a radar image timeout, though, surprisingly. Same night, US 160 W of Wellington, no problems at all and consistent low-end EVDO speeds (~200-400kB/s download).

The card, at least, is more consistent than the phone about using EVDO when it is available than falling back to 1x. (I have a blog post about that topic from earlier this year.) And the phone is old enough it doesn't understand RevA, so standard EVDO is the best speed it'll do.

The data card will handle whatever you can throw at it -- the limitation is the system it's communicating with and the signal strength.

 

[Scott Roberts]

edit - how much of a toll does streaming video take on the air card? Is it similiar to grlevel3 where it is going to take a fairly strong signal to work?

Depends completely on the settings you choose in the encoder. The best balance I've found between image size/quality and data load is the larger "Security" screen size in Windows Media Encoder...I think it's 640x480, 15fps, but I don't remember right now. It might be 320x240. Anyway, there are only two sizes available, and this is the larger one. I think it says it's either 159k or 259k data rate...which is about half the available bandwidth on most EVDO connections. On a 1X connection, the encoder will cache the stream some, so you'll end up with a gradually-increasing delay between what you see and what your stream viewers see. I've had it be as much as 7-8 minutes delay. In EVDO-land, it runs 30-45 seconds.

Streaming will impact your download speed very little -- the effect is seen when you (or your software) makes a request for something. Then the request packet may have to fight its way into the stream of uploading packets. Fortunately, request packets are usually samll, so wedging them in is usually possible if you haven't saturated the connection.

I have had zero success streaming and running even 1 GR instance on a single 1X connection -- the stream saturates the upload connection and the GR requests can't get through, even though the download bandwidth is sitting mostly available. That's the biggest reason I split streaming onto another PC and dedicated connection.

 

[Mikey Gribble]

I have XM too so if I had to I could shut down grlevel3 to keep the stream going. On a 1X connection (don't know what that is but I assume it's weak signal slow speed), if I shut down grlevel3 and just ran spotter network and streamed do you think I'd be alright?

 

[Dave Marshall]

Average 1x data rates are 56k speeds or slower, though I think theoretically it maxes out at 120kbit. In theory, a 1x connection is symmetrical, but I'd expect upload to be a good bit slower than download from experience. I know CTV's stream is approximately a 30K upload at minimum quality, which would probably be rubbing up against the limits of a 1x connection in most locations.

Something to keep in mind is that SN and GRLevel3 are intermittent users of the connection (and SN uses barely any bandwidth to begin with). Unless you're constantly switching radar sites (something I do pretty regularly) GRLevel3 with the archiver turned on is going to use bandwidth for a couple minutes while its downloading, then it will drop to almost zero utilization until the next update, at which point you'll see a brief spike in bandwidth while it pulls the new frame. The time-averaged bandwidth usage of GRLevel3 is pretty darn low compared to the stream.

If your stream is at the very upper limits of the data link on its own, you'll either see the stream freeze when the other programs are hitting their respective servers, after which it will start working again, or if the stream buffers, you'll see the amount of lag increase with each update cycle of the other software.

There is software out there that will throttle bandwidth used by specific applications in order to keep other applications operating happily. If you're having problems with restricted bandwidth on a 1x connection, you could set it up so that GRLevel3 and SN are throttled to keep the total bandwidth demand from maxing out the connection and freezing the stream. Depending on how friendly the backend for SN and GRLevel3 is, this may end up causing timeouts and update failures/disconnects from the servers though.

 

[Eric Friedebach]

On a 1X connection (don't know what that is but I assume it's weak signal slow speed),

That’s a reference to 1xRTT, the wireless standard prior to EV-DO and still found in many rural areas off the Interstates.

 

[Doug Everett]

Just watch out for your throughput limit per month. Almost all carriers have one. For Sprint and most others it is 5 Gigs per month. Sprint charges $50 per gig after you are over the 5 gig cap. Streaming would be what causes an issue here, if anything does.