1. A method for data transmission on a contention-based physical data channel (PDCH), the method being performed by a wireless device, the method comprising:sending a first data transmission on the contention-based PDCH to an access node;
receiving a response to the first data transmission from the access node;
determining a signal strength of the response; and
acting as if the first data transmission either was collision-free or collided with another data transmission of another wireless device, depending on a comparison between the signal strength and a threshold defined by an expected signal strength of the response.