Why do people characterize signal with frequency?

Hi everyone, I know this could be a really fundamental problem...

Is there any way (or has there been any trials in history..) to characterize signals with features other than frequency?

I was starting to learn CDMA recently and got in touch with this spectrum spreading technique. If my understanding is correct, it says that different signals occupying the same frequency band could still go alone without corrupting each other. If this is the case, does it mean that spectrum is not the only dimension that signal could vary to differ from each other? Are we limiting ourselves by putting different signals into different parts of the spectrum? Is it possible to build another set of basis to classify signals?

Any advice would be appreciated. Thx...

If you review the explanations of CDMA and TDMA, you'll see that there are other properties beside frequency that allow to distinguish signals. I don't apply to retell the detailed Wikipedia articles.

https://en.wikipedia.org/wiki/Code_division_multiple_access
https://en.wikipedia.org/wiki/Time_division_multiple_access

Of course frequency is only one characteristic of a signal. Others have been used for many decades. For instance, the type of modulation used is also a distinguishing characteristic. It is possible to use both amplitude and phase modulation of a single carrier to transmit two types of information. The NTSC TV signal (analog TV) used a sub carrier modulated in this manner to simultaneously transmit both the color's shade (phase modulated) and the saturation (amplitude modulated) of that color. Additional techniques like frequency inter-leafing allowed that sub carrier to be mixed with the black and white signal and be separated from it with proper filters at the TV receiver. Other techniques use things like time domain multiplexing. All that preceded digital. With digital techniques, there are far more advanced techniques out there for transmitting as much information as possible on a single signal. Without interference.

Frequency and time are two reference planes which are synonyms with signal at all time

Frequency and time are just different ways of looking at the same thing. They are reciprocals of each other. F = 1/t and t = 1/F. They do bring out or suggest different ways of using the spectrum.

the reason for the usage of frequency is to represent very high values of time in a small number in frequency domain

cos of this the representation becomes less tedious and more simpler

I think the use of frequency in electronics and radiation theory is a lot more involved than just a desire for small numbers. The metric system provides us with a vast selection of prefixes that easily take care of that problem: Hertz, kiloHertz, megaHertz, gigaHertz, etc. These easily keep the number within reason.

Frequency is a lot more descriptive and a lot more informative about the properties of the wave or signal being thought about than the time that one cycle takes would. You could describe a kiloHertz signal in terms of miliseconds and a megaHertz one in terms of microseconds, but it just does not convey the same feeling of difference between them. At least, not in my mind. Also, the frequency of a signal conveys some information about the amount of data that could be transmitted over a channel that uses that signal. A signal in the tens of Hertz could not carry a real time video signal which requires megabits of information. The higher the frequency, the higher the information carrying ability and this is in a direct proportion. If you are using time as a measure of the frequency, then the relationship becomes reciprocal and is a lot harder to visualize.

Tens of thousands of physicists and millions of engineers can't be wrong. Frequency is the best way to think about it. Of course, YMMV.

that is also true pal the analysis of any signal in the frequency domain makes it more easier than that of in time domain