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| How do text messages travel from one phone carrier to another? |
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| madires:
Usually VoIP phones have some configuration switches for comfort noise. And there's RFC 3389 (https://tools.ietf.org/html/rfc3389) to help managing the comfort noise feature. |
| coppice:
--- Quote from: Zbig on January 09, 2019, 12:01:28 pm ---As this thread has already diverted to codec quality, bandwidth and compression, I remember how surprised I was back in the day upon learning at school about the concept of "comfort noise". Apparently, in digital communications devices, there was an audible background noise artificially injected locally by the user's terminal equipment (telephone). --- End quote --- Rubbish. Comfort noise has nothing to do with poor quality lines. Its about silence suppression, and the effect it has on the background mush you normally hear from the far end room in a high quality call. If you are only trying to carry speech, you can stop transmission and save bandwidth, when there is nobody talking. However, the background noise from the room stops along with the voice, and that's confusing. It seems like the call has dropped. A proper comfort noise system estimates the volume and spectral character of the background noise in the room, and sends those parameter to the far end at infrequent intervals. The receiving end then synthesises background noise of a similar character to play to the recipient. Done well, you barely notice the silence suppression cutting in and out, and you can save maybe 30% of the total bits transmitted. |
| Zbig:
--- Quote from: coppice on January 09, 2019, 04:12:58 pm ---Rubbish. --- End quote --- Sorry, you lost me there. You were saying...? |
| MadScientist:
Having worked briefly in this area. The whole telco billing system is more complex then the switching system. |
| duckduck:
How do carriers exchange SMS messages? The same way that carriers exchange any other data: at an internet exchange. Since rack space / servers / bandwidth are not free, there are peering agreements between carriers. https://en.wikipedia.org/wiki/Internet_exchange_point https://en.wikipedia.org/wiki/Peering (much more info here) EDIT: OK, maybe not so much. I'm not sure where SS7 data is exchanged between carriers. Apparently they sell access: https://www22.verizon.com/wholesale/solutions/solution/SS7.html |
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