Embodiments of a UE to operate in accordance with a device-to-device (D2D) communication mode are disclosed herein. The UE may include hardware processing circuitry to determine a synchronization reference time based on reception of signals from an eNB. The hardware processing circuitry may be further to, during a D2D communication session, transmit Multi-Time Transmission Interval Bundle Groups (MTBG) of data symbols during a first group of Data Transmission Intervals (DTI) and refrain from transmission of data symbols during a second group of DTIs. Starting times of the DTIs may be based at least partly on the synchronization reference time. The hardware processing circuitry may be further to transmit, during an in-network communication session, data symbols according to a Time Transmission Interval (TTI) reference time synchronized to the synchronization reference time.