Using TDM circuit switch with 10 slots per frame and each slot consisting of 1000 bits. Suppose there are 10 users and one user suddenly generates one thousand 1000 bit packets, while the others remain idle. The active user can only use it’s one time slot per frame. Using this formula (bits-to-transmit)/(link speed) the author calculates it would take 10 seconds to transfer the data.

I don’t understand how the author arrived at 10 secs as the time to transfer the data. How is it possible to transfer 1000000 bits in 10 secs with a link at 1000 bits/s?

  • 2
    Homework is explicitly off-topic here.
    – Zac67
    Dec 31 '17 at 20:49
  • This is not Homework ... I’m self studying.
    – dcrearer
    Dec 31 '17 at 20:50

TDM allocates one or potentially multiple slots to a single user.

In your scenario, each slots is allocated 1/10 of total transmission time. If the slot time is one second, each slot transfers for one second and then needs to wait for 9 seconds. 1000*1000 bits require 1000 slot times to transfer.

With 1000 bit/s total speed and 1000 slot times you'd need 1000 s for transferring and 8991 seconds for waiting.

With a slot time of 1/1000 s (or 1000 slots/s), you'd get 10 s total time or more exactly 9.991 s - you don't need to wait after the last transmission slot.

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