I am studying about logic gates and I came across this diagram showing the uses of multiplexors and Demultiplexors in communications networks. Using Mux/ DMux in network communications
In the description of this diagram the Mux and DMux are connected to completely different oscillators and act independently and asynchronously.
What I don't understand is won't we lose half the information that goes into the Mux? If a Mux takes a and b from the source and only selects one to go into the line without storing the other bit, then we will lose half the information of the a line and the b line.
Am I missing something here or is this diagram too over simplified?
I searched a lot about a better explanation but I have yet to find one that convinces me.
This is a TDM (time domain multiplexing) scheme. I think this link sums it up quite nice:
https://www.techtarget.com/searchnetworking/definition/frequency-division-multiplexing
In short - the missing information is that the shared bus data transfer rate is higher than the sources.
In your example, assuming both sources send data non-stop, and both have the same data transfer rate, it has to be at least twice than the sources data transfer rate to prevent data loss.
The mux/dmux selectors operates at the shared channel data rate. Obviously, they need to be somewhat calibrated for the receiving side to sample the data correctly.
Note that if the shared bus data rate is much higher than of each source, there will be "empty" or "duplicated" cycles on the communication channel. This requires some mechanism (like "valid" indications) or more tight synchronization between the two sides to identify which data is valid and which is not.
Another option for this diagram to work without lose of data, is if the multiplexer had a mechanism to give backpressure to the sources. This backpressure indicates one of the sources to wait while the other source is being served.
In this scenario the connecting channel can be at a lower data rate than each source.