datix logoUsing the e815 cellphone as a modem

A little-known feature of the Motorola e815 cellphone (and perhaps some others) is its ability to work as a wireless modem for a laptop to establish a PPP connection to the internet.   With a Linux laptop it's especially easy because no extra software or modifications to the phone are needed.   With a USB to e815 cable it is really easy to connect a Linux laptop to the internet via Verizon's MobileOffice service.   This service is available to any Verizon Wireless subscriber, but not publicized at all.  I believe there is no added cost except for minutes usage, which is zero after 9PM and on weekends. 

No changes to the phone are needed except to enable DUN (DialupNetworking) by keying in # # 342587 (# # DIALUP).  If you do this quickly enough, the display will briefly say "Dialup Networking Active".  If you're too slow, it won't.  Try again.

You can deactive DUN by reentering this code, but there doesn't seem to be any downside to leaving it active.

When you plug the phone and cable into a USB port, /var/log/messages will show that a new device has been detected, and a new device file, /dev/ttyACM0, will appear.   This device behaves like a normal modem.   To use it, run system-config-network and create a new "Modem Connection", and give it a nickname, eg, "Verizon".  A search for a modem will fail to discover /dev/ttyACM0, so manually enter that into the appropriate field.   In the dialup data, set

phone number: #777  (odd, but correct)
login name: qnc
passwd: qnc    (I think anything will do)

and in the Advanced tab

Modem initialization string: AT$QCMDR=2

Check:    "Let PPP do all authentication".
Check:    "Make this connection the default route"

After saving these settings, activate this device and enjoy your new wireless connection.

All internet services that I've tried work the same as when connected to my LAN, just a lot slower.  The laptop accesses email thru my public domain name and the main server delivers it via IMAP.   The server is a secure relay for outgoing email.  Thus, full email service is available when connected thru the cellphone.   I can now go (almost) anywhere and be connected.

I measured the effective transmission speed by scp'ing a large file from my server and then back again.  The speed was 1.5 KB/sec in both directions, which is 15. Kb/s. The phone displayed "Data 14.4 K"during the connection.  I suppose this meant 14.4 Kb/s.

According to http://www.zdziarski.com/papers/v710info.html, the InitString tells Verizon which service you're connecting to.

AT$QCMDR=2 for MobileOffice, or
AT$QCMDR=3 for ExpressNetwork

As I understand it, MobileOffice is a free service that uses a 1xRTT channel, which is slow, but available throughout the Verizon cellphone service area.  In elite urban areas Verizon also offers the ExpressNetwork that uses EVDO, a high speed digital transmission mode that provides speeds up to 2.4 Kb/s, but also requires subscription to that service at extra cost.  Verizon marketeers try to sell EVDO wherever possible, and downplay 1xRTT.  EVDO isn't available where I live, and I'm weary of paying Verizon for services I don't need, so I have no more info on ExpressNetwork.

MobileOffice is adequate for occasional internet access.

It's also possible to use BlueTooth instead of a cable to connect the laptop to the cellphone, but that requires modifying the program in the cellphone because Verizon has crippled that feature.   Also, my laptop lacks a BlueTooth module.

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