On Jul 6, 2007, at 6:20 PM, John Ioannidis wrote:
Unfortunately, it's not so easy to roll your own on top of a 3G- enabled smartphone. The "broadband" channel does not have the tight jitter and throughput guarantees that voice needs, and some providers (Verizon in the USA for example) consider running voice traffic over their "broadband" network a violation of the usage agreement (no need to blame the government for that, their own greed is adequate explanation). There are lots of other technical and human-factors issues that have been covered to great extent in this and other fora./ji
The Cryptophone project in Europe <http://www.cryptophone.de/> has been trying to tackle the QoS issues for four or five years now. I haven't looked at their implementation closely in several years, but back in 2002 or so they were using CSD (modem-modem calls) instead of the broadband channel, trading bandwidth for low jitter... With current CPUs and audio codecs you can get decent voice quality over 9600bps.
Thanks, Eric
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