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voip_wire

join:2010-07-02
kudos:1
reply to OZO

Re: [General] Receiving calls from cell phones to Voip phone

said by OZO:

Cell phones have intrinsic and big latency ...

I am not sure that there is any intrinsic high latency in cellular communication. All EM waves travel at the speed of light. Given a fixed speed of information travel, the time it takes to go from point a to b is purely a function of distance.

Note that this distance is not geomtric distance, but an effective distance. In other words, latency can be large if the signals are improperly routed. However, this is not a fundamental, physical constraint.

I expect that spectrum (as you noted) and transmission losses are the discrminating factors in voice quality. Dissimilar codecs would require an extra decoding - recoding step, perhaps contributing to poor quality.

To the OP, have you tried forcing the gsm codec? The narrow band codecs should not degrade clarity ( in my opinion, but this is a very subjective issue), but would make the audio sound less "natural".

This is partly an educated guess, so I would really appreciate if you report back your findings!

Cheers,
-m

PX Eliezer70
Premium
join:2008-08-09
Hutt River
kudos:13
Reviews:
·callwithus
·voip.ms
If cell towers are busy, some mobile companies switch to GSM Half-Rate [GSM-HR or GSM 06.20] which is 5.6kbit/s

That gives crappy sound.

Reportedly some mobile companies have this as their defaults.

-----------------------------

Also, Nokia offers this as a [customer] option on most Nokia cellphones, the customer can do this by pressing *4720#

Why would a customer do it?

Because it extends battery life.