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'[EE]: CDMA / GSM audio link'
2002\03\03@035346 by Kathy Quinlan

Hi all,

I am designing a GSM / CDMA audio link for transmission of signals for
broadcast FM radio (88-108Mhz)

I am looking at encoding and decoding the signal to get the best possible
signal through the link (ever listened to on hold music over a mobile phone
? ). I am hoping that a data rate of 9600bps will support a bandwidth
limited signal. My specs are the best signal quality achievable, audio
output bandwidth above 3Khz (300 - 3.3Khz) MONO only needed (makes it easier
as all our transmitters are mono FM).

I am looking around for audio codec chips, but can not seem to find any that
seem to fit the bill :o(

Would I be better off designing my own ? IE ADC to encode and a DAC to
decode with a data compression / decompression routine that will save me
bandwidth ?

The link is only needed to be one way, may build a detection circuit to let
the studio end know that the link has gone down (eg remote mobile out of
range, not turned on, signal drop out etc.

Any suggestions appreciated (constructive please)



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2002\03\03@071750 by dbengtson

picon face
Based on what you are saying, I suspect that you best option would be
to DIY. The signal compression aspects of this might be challenging,
though. Is this for an existing Mobile system? Part of the problem
with music on hold systems and mobile phones is the audio codec's in
the phones are optimized for voice only, and so their performance for
music is not great. It's almost impossible to measure the system audio
performance of a Mobile because of this.


On Sun, 3 Mar 2002 16:51:48 +0800, you wrote:

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