Difference between physical layer and data link layer, so as to understand difference between multiplexing and multiple access?

Question

I am trying to understand the relation and difference between multiplexing and multiple access.

Since multiplexing appears in physical layer, and multiple access in data link layer (or MAC sublayer), what is the difference between physical layer and data link layer, which can help to explain the difference between multiplexing and multiple access? I don't completely understand the Quora replies there, and I am not sure if they are correct 100%. But they may point out the right direction to understand it.

Another link also says:

Two types of combining signals are:

• Multiplexing - combining signals from the same sources
• Multiple-access - combining signals from multiple sources

Do the signals in multiplexing come from the same source, or can the signals also come from multiple sources?

Thanks.

Answer 1

Neither definition is quite correct in all cases. As I've said before, these terms are abstract, so depending on your point of reference, they could be right or wrong. But it is not true that one is layer 1 and the other is layer 2.

Multiplexing is a technique for combining signals, while multi-access is a characteristic of a medium.

Answer 2

Multiplexing means combining analog signals or digital data streams into a single composite signal. The output is just ONE signal. This signal has the content of all its constituents. This signal can travel through a shared medium or a non-shared medium. The receiver of this signal can extract all its constituents.

Multiple access means that different devices are able to access the same medium in some shared manner. They may use time slots or have a particular schedule for using the medium. In most cases, only one of the devices is using the medium in any given time instant.

So, multiplexing COMBINES the signals into one signal while multiple access governs WHEN this signal will be transmitted through the medium.