In embodiments, apparatuses, methods, and storage media may be described for mapping media access control (MAC) protocol data units (PDUs) that are used to transmit scheduling assignment (SA) discovery, and/or device-to-device (D2D) data. Embodiments herein may describe how one or more MAC PDUs may be mapped into a time resource pattern for transmissions (T-RPT). Embodiments herein may further describe examples of how and when a UE may skip subframes in transmissions of the SA and/or data. Additionally, embodiments herein may further describe examples of how a UE may behave if the UE cannot transmit one or more scheduled instances of SA or data. Additionally, embodiments herein may describe resolution of collisions of D2D discovery messages in the time domain. Other embodiments may be described and/or claimed.