Nice. Trying to read/understand "RF Systems and Modulation" is what got me interested in this subject in the first place.

So in my mind i map your comment as; the "carrier signal" frequency (analog) is the infinitely repeating regular signal traveling at v(p) while the "information signal" frequency (analog/digital) imposed on top of it creates the pulse/wave packet traveling at v(g).

Add in different media and you have a difference between v(g) and v(p) - https://news.ycombinator.com/item?id=49988070