Methods, systems, and devices are described for a system that supports wireless communication with a first set of devices using a first OFDM symbol duration associated with a first tone spacing (i.e., a first physical layer (PHY) configuration) and second set of devices using a PHY configuration associated with a second tone spacing. A base station may transmit a set of discovery reference signals (DRS) in a narrowband region of a primary channel of a carrier. The DRS may have the first PHY configuration and a secondary channel of the carrier may support communications using the second PHY configuration. The base station may transmit a first system information (SI) message for one set of devices using the first PHY configuration, and it may transmit a second SI message for another set of devices using the second PHY configuration.