BSS, Base Station Subsystem is a part of Public Land
Mobile Network (
PLMN).
It's needed to support Mobile Stations' (MS) connection to Mobile Switch Center (MSC) via Air Interface (Um).
Most visible part of an BSS is Base Station Tranceiver (BTS) which consists the BTS equipment and an antenna which can be located i.e. on the wall of building or on the masts all over the rural area.