Steve Shear <azur@netcom.com> writes:

[very useful explanation of GSM TDMA, and the new HSCSD]

64 kbit/s tied to ISDN is very nice technology.

ENCRYPTED GSM LINKS If the GSM phone includes a data port, as some already do, just connect your laptop, dial your ISP and 'push' the encrypted traffic over that link (e.g., using TCP/IP and PGPfone).

This would obviously be possible, but to my mind reduces the appeal of the system. Not every one has a laptop. Even if the potential user does have a laptop, booting windows95, and starting up PGPfone is an onerous task compared to just dialing a number on a mobile phone. It's a user friendliness issue, and a question of ergonomics. A mobile phone is more portable than a GSM phone with a laptop plugged into the data port. You can't fit the laptop and GSM phone combination into your shirt pocket. What are you going to use for a handset? Radio operators headphone (with mike attached to the headset) plugged into the laptop? That's more dangling wires, and makes the system less portable, and even more onerous to setup (take laptop from carry bag, plug in headphones, plug in phone data port, wait for laptop to boot, etc). Even for crypto enthousiasts, I would submit that many would neglect to go through the hassle of going through PGPfone for most conversations, and would instead just use the mobile phone in the clear (or with A5 encryption). This for similar reasons to the situation with PGP itself, many people rarely use PGP, even though there is abundant software available to use it seamlessly with most mail readers. (I can vouch for mailcrypt.el the emacs interface to PGP, and use it for to anyone who has a PGP key, and does not express displeasure at receiving encrypted email). Also, the cell phone tarriffs may be higher if you need higher bandwidth to get the software only voice codec implementations in PGPfone to produce equivalent full-duplex voice quality to that expected from a digital mobile phone. Not knocking the mobile phone and laptop combination for the purpose of having mobile TCP/IP access from a laptop, I know several people who have this combination, though only at 9.6kbits, and even at that speed it is very neat. Adam -- print pack"C*",split/\D+/,`echo "16iII*o\U@{$/=$z;[(pop,pop,unpack"H*",<> )]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`