PCS is a marketing term invented by cellular
carriers. Both 800 and 1900 Mhz are still
"cellular." PCS originally meant Personal
Communications Services which was a term
used even with old analog via touch-tone
before there ever existed 1900 Mhz "Cellular."
The system could not operate with just one cell because
if everyone was on the same site they would
interefere with one another. More profound
than that, but a cell-phone is still cellular
whether on so-called "PCS" or 800 Mhz
bands.