The transmission time is an important parameter for data transmission because it directly affects the transmission costs. The transmission time depends on the file size to be transmitted and the transmission speed.
Since file sizes are usually specified in bytes, whereas the transmission time is specified in bits per second, the file value must be multiplied by a factor of 8. In addition, the overhead of the various headers and trailers must be taken into account when determining the transmission time.
A few examples will illustrate what has been said: The transmission time of a text page with 40 lines of 30 characters each, i.e. 1200 bytes, is for example 0.18 seconds with ISDN at 64 kbit/s and an assumed overhead of 20%. If a graphics file of 10 megabytes( MB) is transmitted at the same transmission speed and with the same overhead, then the transmission takes about 26 minutes. The transfer time for this graphics file would be reduced to 0.65 s with Synchronous Digital Hierarchy( SDH) at 155 Mbit/s, and with a 5th generationmobile network( 5G) with a download rate of 10 Gbit/s, the same graphics file would be transferred in half a second.