Can I have two system models in the same paper, for the same research? I am writing a paper in the field of telecommunication. I would distribute my paper into two parts. In the first (more general) part, the system performance for all mobile-phone towers is considered. Results derived from this part are used to study one particular mobile-phone tower. For the first part, I use probability over the entire region. For the second part, I only consider a single tower and revolve my study around it.

Question: Can I have two system models in the research paper with the explanation that I have given above?
Yes, you can. But be sure to follow the common structure of a scientific article. That means that you have to have 2 subsections at least on the procedure section (AKA materials and methods) as well as on the results section and on the results discussion. These sub-sections are those related to your 2 systems.
I would conclude about the paper as a whole. Also, be sure that your introduction states at the end the interest of studying two separate objects: if the first object is more general, is the idea to apply the methodology to a smaller system in order to validate it. Or is it the idea to get a generalization of the findings obtained for the smaller sub-system? Usually the latter is widely better accepted. In that case, you should put the smaller sub-system first.

I hope I have helped you,
Cheers,
Miguel Andrade
Mechanical Engineer,PhD