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I want to know difference between propagation speed and bandwidth in digital communication.I know bandwidth is no of bits in one second and propagation speed of signal is distance traveled by signal is one second.Is there any relation between them or they are totally different.Can anyone tell me exact definition to differentiate these twos.

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    $\begingroup$ Jumbo jet full of DVDs: high bandwidth, low propagation speed. Person doing Morse code: low bandwidth, high propagation speed. $\endgroup$ – David Richerby Oct 24 '13 at 15:52
  • $\begingroup$ What do you want to say? $\endgroup$ – user1917769 Oct 24 '13 at 19:00
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They are unrelated.

The bandwidth is, as you correctly said, the number of bits per second. The propagation speed is the time until the first bit arrives (this is also called the latency).

Imagine you have an army of snails that can carry SD cards along a straight line. Their propagation speed is very slow, so it takes a long time until a snail arrives after you send it. However, you can send a snail every second, so that after the initial delay your snails deliver one SD card of data every second. That's high bandwidth.

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  • $\begingroup$ But if we increase propagation speed will bandwidth also increase? $\endgroup$ – user1917769 Oct 25 '13 at 17:53
  • $\begingroup$ No, the number of snails per second stays the same, only the time between setting a snail on the trail and it reaching the destination decreases. $\endgroup$ – adrianN Oct 26 '13 at 10:55

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