Hi Fabio,
On 15 January 2011 20:56, Fabio Pietrosanti (naif)
<lists(a)infosecurity.ch> wrote:
Maybe there are an area of conditions where transcoding doesn't happen,
like within the same operator or within national gsm operators
interconnections.
If that could be confirmed, it would be possible to have a low latency
full-duplex communication data path at 13.3kbit/s (GSM codec) or
12.2kbit (GSM EFR/AMR codec) to be managed such like a serial connection.
On top of a protocol alike HDLC could provide a serial connection over a
GSM voice raw transport
Someone willing to make a try?
Note the L1 channel coding is intimately linked to characteristics of
the codec/connection type, and it's just not as simple as treating the
bits that usually carry codec frames as a serial link. For example
block size and error correction varies by codec and even between
individual frame types within a codec. I believe L2 has no automatic
retransmission on frame error for voice channels, so that must also be
handled.
I'm not suggesting a solution, just pointing out these are not simple
"boxes and arrows" to be freely substituted without detailed knowledge
of the surrounding system.
David