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I am curious to know if in an Ethernet network the techniques used in LTE or other High Speed wireless Network that allow different devices to send data at the same time can still be used.

For example would it be possible to use different frequencies for different devices on the same network and still have the devices "understand" each other?

I know that when hubs were used and many computers would have access to the same wire there was a system called CSMA/CD that would prevent two devices from talking in the same time. What if the devices would communicate at the same time but at different frequencies?

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    Of course it's possible, but what you're describing would no longer be Ethernet. How would a device know which frequency to listen to in order to hear a sender?
    – Ron Trunk
    Commented Sep 1, 2017 at 17:46
  • Sure you could but with switches creating a direct path to communicate why would you add issues like frequency channelization for many devices. It'd become as complex as wifi. You could still have broadcast to identify your channel. But if your "nic" card is talking to 10 diffrent devices that card would need the capability to talk to many frequencies possibly creating a very expensive card or chip. Then you have channel overlap. If two devices use the same channel and you need to talk to both of them it could get messy. But, very interesting idea. I wonder if there were tests of this concept?
    – Fixitrod
    Commented Sep 4, 2017 at 16:58
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Commented Feb 19, 2018 at 20:42

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Using different frequencies for transmission from multiple sources or in opposite directions is called frequency-division multiplex (FDM). This implies that each transmission sources has hold of a dedicated frequency band it can use.

Nearly all Ethernet PHYs use baseband signaling - baseband means the frequency starts at (close to) 0 Hz and reaches up the maximum frequency that is used. Therefore, baseband signaling provides no room for FDM.

(Optical fiber can be considered a special case: the baseband signal modulates the amplitude of a light source - using different light colors/wavelengths you can very well multiplex various sources into a single fiber. This is used for e.g. 1000BASE-BX10 or 10G/GE/PON.)

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Can the devices want to send data at the same time? Yes. Will the devices send the data at the same time ? No.

the idea is simple. Be it high speed or LTE or any type of communication If the technology is using packet switched network- Ethernet the transmission link has a maximum bandwidth. This dictates how much data can traverse through the data per instance of time.

Thus if more than a certain amout of data is transmitted then it results in collission, retransmissions and this reduces the performance of the system.

Can the devices send at different frequencies. For that, first of all the cable should support different frequencies of data through the channel (which is not the case for eg. You cannot send any frequency on an optical fiber) which is generally used in high speed communications

But asssuming that it does, the switches need to be equipped with to listen at different frequencies and allow band gaps to prevent disturbance.

Secondly the hosts need to be smart enough to listen and understand which frequency is currently unused and transmit at a different frequency.

This involves significantly higher processing and takes away the fundamental requirement that a network must be simple.

And as Ron pointed out it wouldnt be Ethernet

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