A first terminal device (100A) transmits scheduling assignments to announce its scheduled data transmissions. A second terminal device (100B), after receiving the scheduling assignment, determines the timing information of the scheduled data transmission from the first terminal device (100A). However, the scheduling assignment transmissions from two terminal devices (100A, 100B) may collide, in which case, the terminal devices(100A, 100B) may fail to receive the scheduling assignment from each other and miss the scheduled data transmissions indicated in the scheduling assignments. The present application discloses how to detect collisions between scheduling assignment transmissions from two terminal devices (100A, 0B) that are configured for device-to-device communication.