I would love to have some (wide area) mobile VoIP phones. I've been searching for a solution for awhile and finally decided to just see how bad it would be to use a current mobile phone network to achieve this functionality.
I've been a SprintPCS user for years so after getting reports of sub-400ms ping times, I decided to give their data card a try. The nearest stores (in Indy) only had the Novatel Wireless Merlin C201 so that's what I got.
As has been reported, after initializing this card (under MS Windows) it is readily usable by Linux. Once up (as a PPP device), it yielded ping times mostly in the 300 to
400ms range. It seemed fairly robust. I didn't get the many-second-long silences that I expect from GPRS. --- yahoo.com ping statistics --- 50 packets transmitted, 50 received, 0% packet loss, time 49431ms rtt min/avg/max/mdev = 307.951/453.274/1437.838/214.054 ms, pipe 2I discovered that port 80 is run through a transparent HTTP proxy. (Some of my photos were recompressed.) Most communications seemed unfettered though. Unfortunately, when I tried using a SIP phone over this connection it failed to even register. I suspect timing was the issue but I don't have an eye for spotting SIP problems. (The packets seemed to be passing o.k.)
Recently I found iaxComm, an IAX softphone. I decided to give it a whirl and it registered without any problems. Making calls seemed o.k. and the audio was decent. When I tried to send audio, however, it fell apart. It
*really* chokes on ulaw (of course) but even GSM is unusable. 50 packets transmitted, 50 received, 0% packet loss, time 49007ms rtt min/avg/max/mdev = 366.003/1182.807/2815.567/536.911 ms, pipe 3I like having this card but the latency is too high for me to justify keeping it at $80/month. I'm hoping for UMTS to arrive someday soon...
--kyler