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In a TDM medium access control bus LAN, suppose the channel has a effective bandwidth of 10Mbps and each station has effective throughput of 1Mbps, then what is the maximum number of stations allowed ?


Here the answer is 10/1 = 10. I don't understand the term "maximum number of stations allowed" in TDM.

If we are dividing both the bandwidths then it means that we are considering the possibility of all stations transmitting together and hence we are saying only 10 stations can transmit at a time.

But in TDM, only one station is allowed to transmit data at a time right ? So how does dividing the bandwidths make sense here?

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Within the given time period of 1 second, each host will transmit. The circuit will have transmitted up to 10 Mb, and each host will have transmitted up to 1 Mb in that second. That means you can have a maximum number of 10 hosts on the circuit.

TDM will divide the full circuit into a number of virtual circuits, and a host has exclusive use of a virtual circuit. If the circuit is 10 Mbps and the virtual circuits are each 1 Mbps, then you can only have 10 hosts using the circuit.

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  • Thanks for the answer. Can you please tell me the difference between effective bandwidth of channel and effective bandwidth of each station ? I am slightly confused between these terms. – Zephyr Nov 25 '17 at 8:27
  • The channel is the full circuit in the context of the question. What the question is saying is that the circuit is 10 Mbps, and each virtual circuit is 1 Mbps. The circuit will transmit each virtual circuit for 1/10 of a second. – Ron Maupin Nov 25 '17 at 8:31
  • Yes, I understand that. But in general can you tell me the difference between both these terms ? – Zephyr Nov 25 '17 at 8:33
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    That is normally how I would view throughput, but clearly the author meant effective bandwidth, not how I see throughput. It is probably because the question is only about the raw bits on the wire, not any protocols above OSI layer-1. Another book may use different terms. – Ron Maupin Nov 25 '17 at 8:46
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    Yes, that is what it means. Effectively, each host can transmit 1 Mbps, even though it is done in bursts. TDM circuits have burst rate, but that is getting ahead. – Ron Maupin Dec 9 '17 at 19:00

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