I am thinking a lot about infrastructure these days. My definition of infrastructure is "something, which facilitates other things, but does not by itself fulfill the need of a person". An example is the fiber-optics combined with the TCP/IP protocols and a bunch of other technologies, facilitate the creation of the internet, which again facilitates creation of services, which in the end fulfill the need for people to for example communicate. The word infrastructure can certainly be used for the fiber-optics and I believe also for the internet. Another example, is pure research, which "is research carried out to increase understanding of fundamental principles. Many times the end results have no direct or immediate commercial benefits". I believe that one cannot use the word infrastructure for pure research, even though I believe it is conceptually the same thing. Is there any other expression than infrastructure one can use for these things (Social Capital is another example)?
Infrastructure is defined as
in this sense fiber optics, internet or services can all be considered infrastructure - they are indeed a basic structure or features of some systems (in your example a communication system).
Social capital can be called infrastructure; for a social system or a social organization it actually refers to infrastructure on which the system functions.
Pure research can not be called infrastructure because it is an activity (and not an object such as basic structure or feature).
You could say that pure research is the infrastructure on which all applied research is founded.
However, that would be a metaphor drawing upon the property that infrastructure is necessary for functioning of the system in a similar manner as pure research is necessary for applied research.
You could simply say that pure research is the foundation for ... (or that the results of the pure research are the foundation for ...).
I think in the case, "infrastructure" would be fine, but if you are looking for other words, "groundwork" is fitting to the context:
Note, the example is not of my own, but the example, coincidentally is also concerning possibly a piece of "pure research", the discovery of the laws of electricity.
I don't think "infrastructure" and "pure research" are at all similar.
You build infrastructure because you need it to do something else, the something else is usually very specific. You build a highway so you can drive a truck from a to b, you lay fiber optic cable so you can sell more internet connections.
You do pure research because you want to increase the sum of human knowledge. That knowledge will probably be useful to someone (maybe even yourself) in the future but you don't know how or even if it will be useful until after the research is done.
I think infrastructure is itself a pretty abstract term, but you could use "enabling technology", "foundation", "nuts and bolts", "backbone" or "framework" depending on the type of infrastructure involved.
A more abstract term for pure research could be inquiry or "seeking knowledge".