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modem throughput via VG248

I am finding that any modems dialing out through a VG248 are only connecting at 28.8kbps not their standard 54kbps.

any suggestions as why or how to fix it.

thanks

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Re: modem throughput via VG248

Remember that modme relay on only VOIP platform uses G711 as the codec, meaning it samples at 64KBps.

Nyquist's sampling theorem states that to reconstruct a sampled signal , the waveform must be sampled at 2 times the maximum frequency (or rate) contained in the original waveform.

Therefore, in theory, at least, we should get a reliable maximum of 32 Kps when we pass a modem signal over a G711 codec.

The 33.3K and 56K modem standards do some very funky modulations based on phase shift keying and quadrature modulations so they can actually push it to the 56K max, but the G711 codec in the middle will affect this, so 28.8K is actually quite good - some customers have reported rates slightly higher than this but they are the exception rather than the rule.

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