500 Simultaneous Voice Calls Over My DSL Line – In Theory

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.