The same set of frequencies are used over and over within a given area, to make the most economical use of the radio spectrum. No matter how the radio works, be it PCS or conventional cellular, no matter the enabling transmission technology, say TDMA or CDMA, it is all cellular radio, since distributed cell sites, employing frequency reuse, make up a wireless network. PCS generally refers to cellular radio at higher frequencies. Being purely digital, though, is not necessarily a good thing. Quite often the all digital services lack coverage since more base stations are required.
Audio quality can suffer terribly, with analog still superior.
As wireless evolves the different services may operate on high and low frequencies as needed, thus blurring the defining lines between the technologies. Depending on what the local carrier offers, it even changes its operating method, dropping back to analog cellular service where digital service isn't provided. I am a fan of this system. GSM or PCS, besides being all digital, and designed in Europe with no thought of being compatible with conventional cellular systems, does differ from standard cellular in the way it makes and sends calls. The difference is in the thousands of details.