Now here is another number of ponder on: Once upon a time, back in the 1990's, GSM base stations where connected via 2 MBit/s E-1 backhaul links. With a data rate of 16 kbit/s required for one voice call, 120 simultaneous calls could be transmitted over such a link, minus some channels for control information. At the time, only a fraction was used and a single E-1 was usually daisy-chained to several base stations. Today, I have a 25 MBit/s DSL line to my home for my own use with a 5 MBit/s uplink. Voice has evolved and half-rate AMR now uses 6.75 kbit/s. Just think about the number of voice calls the DSL line I have for my own could transport: 5000 kbit/s / 6.75 kbits/s = 740. Subtract IP overhead, etc. and we should still be at around 500 simultaneous calls over my DSL line. And even if full-rate AMR was used it would still be 250 simultaneous calls over my private DSL line. Incredible how technology has evolved.
One thought on “500 Simultaneous Voice Calls Over My DSL Line – In Theory”
Last time I checked my VoIP traffic I found that the voice codec (about 8 kbit/s) plus IP overhead at small packets resulted in roughly 54 kbit/s total on the wire. So, similar to computing, no one cares about efficiency if there is “enough” resource.
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