A base station for secondary-cell (S-cell) operation in an unlicensed band is subject to listen-before-talk (LBT) rules. The apparatus generates S-cell discovery reference signal (DRS) that includes a primary synchronization signal (PSS) based on a cell ID associated with the base station, a secondary synchronization signal (SSS), a cell-specific reference signal (CRS), and optionally CSI-RS. Solutions are described for generating portions of the DRS to accommodate the placement of the DRS in arbitrary subframes.