Homemade EVDO/WiFi Mobile Access Point

Tamundson writes "Over the last few weeks I've built myself a mobile access point for my car. It's based on a Soekris net2421 embedded Linux box and uses Verizon's 1xRTT/EVDO network as its uplink, resharing it over 802.11b. Wherever my car goes, my Internet link goes! :) I finally put some webpages together on how I built it. The components are pretty cheap and anybody with basic Linux skills can build their own just as easily. I've also got it interfacing with Google Maps to do live vehicle tracking via gpsd. It also uploads pictures from an on-board webcam every five minutes or so."

No such thing as a net2421

[Cainam]

According to the article, the embedded platform used was actually a Soekris net4521. There's no such board as the net2421.

Re:It'll crawl!

[menn0nite]

Umm... evdo is 2.4mbps tops, 300-500k PROMISED. Since I've been using it I've averaged 800k down, 160k up. I've had no problem with ssh, (and vnc as well as terminal services )

Re:It'll crawl!

[Tugrik]

For speed testing I used Broadband Reports [dslreports.com]'s site.

In 1xRTT-land I got 70up/30dn most of the time. About 1/4 of the time I'd get 110up/50dn. At the worst (only a few times, and usually when the evening commute hours put a lot of traffic near where I was parked) I'd get about 50/10. Compared to a 56k modem (about 26/20 on the same tool when I tried it), this isn't bad.

I've had 4 computers using it at the same time. While it will start to gronk on images with multiple access it's truly not that bad. And no, we're not using any kind of proxy, cache or compressor.

I've yet to get this system out under EVDO coverage yet, save for the single test that got me 600dn (found one local tower where it was activated. Didn't last. Hrmf). When EVDO hits my area (or I take a trip into an EVDO area) I'll put up better metrics.

Compared to GPRS (my old wireless link) it's much nicer.

Re:rural no dsl/cable option...

[Tugrik]

This is what folks like JunXion [junxion.com] already do. It's really simple. Just remove the WiFi board, add a (surprisingly cheap) directional yagi antenna, a 3w 800/1900 booster and point at the nearest tower. Boom. House-data over ethernet. The device has two ethernet ports already built in. I use one for wired clients and the other as an alternate uplink if I don't use the EVDO card.

Re:It'll crawl!

[Daniel Wood]

Not really. I used a Sprint phone as my primary form of net access for nearly a year. While it does compress images(REALLY high compression at that), you can still pull 140kbits continuously. I used to run Kazaa downloading mp3s all the time and I used DUMeter to track my speeds. Consistent 140kbits, except on the weekends, then it was like 14kbits, especially on Sundays. Average reception where I was at was 2-3bars.

Why do you need a car?

[mi]

My bluetooth cellphone [verizonwireless.com] and laptop [neuro-tech.net] do this. The phone can "dial" Verizon's network. Not sure, what the bandwidth is supposed to be, but I saw downloads of 20 kilobytes per second.

The laptop talks to the phone over the built-in bluetooth and can share the connection over the built-in WiFi card.

Re:...and back to 2-wheels again

[Christopher Thomas]

What I didn't put in the project web pages before it got /.'d: I'm making a case with integrated battery that mounts on the back of my R1150GS motorcycle. If I get the size trimmed a bit it should fit without taking up any of the bike's luggage space. Now to figure out how to make a lean-angle sensor to record that along with the speed/position data... :)

You could use the dual-axis accelerometer [digikey.com] I used for the robot project to sense tilt changes. Have it integrate changes to guess at current tilt, and recalibrate itself by assuming that anything maintained for 30 seconds or more is a tilt of zero. You could combine it with one of the pseudo-gyro sensors made by the same company (Analog Devices), but be warned that they're ball-grid array packages (and it's probably overkill for your purposes).

Re:It'll crawl!

[greg1104]

I've been using the same Verizon broadband service as is described in the article for about six months now. When connecting to their EVDO network, I get a consistant raw rate of 500Kb/s on downloads and around 100Kb/s up. This is in the suburbs about 15 miles from the center of the coverage area I live near (Baltimore). While I don't have any firm numbers, the network seems even faster when I'm nearer to the center of their area, like when in NYC.

Note that I saw raw rate here because I'm not using the compression package Verizon provided. While it seemed to slightly improve performance when browsing the web, I found that something it was messing with made SSH sessions much less reliable. I turned it off the first day and haven't missed it.

While there are occasional hiccups that cause me to lose the connection (which are no more frequent than when I'm connected with 802.11b; screen is your friend here), I can assure you that when in the EVDO sections the SSH sessions I launch every day work perfectly even if I have two or three computers sharing the network connection via NAT.

Or... use a laptop

[bmidgley]

We don't have EVDO in my area yet, but I do this all the time with my laptop and a 1xrtt connection. It connects through bluetooth to my v710 and I share the connection using an atheros wifi card.

I was going to switch to an intel wifi card when the driver started improving, but they don't support master mode yet.

Under debian, it's fairly easy using ipmasq. If I "ifup" the wireless adapter when there is already a default route (from the phone or ethernet), the wifi card is set up to take a static address with no default route of its own and fire up a dhcp server before it reruns ipmasq.

I was running it today on the bus. A pal was using it for his network connection but he had to ride a lot farther than I did so he was sad when my stop came up.

I wish I knew how to make the net sharing stealthy like OpenBSD does. Without any stealth, I think if verizon wanted to figure out who was sharing their connection, they could find out.