Techniques and apparatuses described herein facilitate narrowband communication within the unlicensed frequency spectrum by simultaneously transmitting (e.g., in adjacent channels) a plurality of anchor channels. For example, a base station may simultaneously transmit at least three anchor channels of 180 kHz each so that the 500 kHz minimum bandwidth requirement is satisfied. Furthermore, the techniques and apparatuses described herein provide discovery reference signal (DRS) structures to cause the different types of DRS to be repeated and/or transmitted on different anchor channels, which improves frequency diversity. Also, a synchronization signal of the anchor channels may be used to indicate a configuration of the anchor channels. Thus, synchronization in the NB-IoT-unlicensed (NB-IoT-u) spectrum is enabled, and efficiency is improved over synchronization using a single anchor channel.