Aspects of the present disclosure are directed to ascertaining whether data messages are repetitions of a previous data message. As may be implemented in accordance with one or more embodiments characterized herein, data packets (130/131) are received (102) and which use a first time delay relative to transmission of a previous data packet (120/121) by a different transmitter. Repetitions (110A/111A) of data packets are also received (102), and which use a second time delay relative to transmission of a previous data packet (110/111) by the same transmitter. The second time delay is less than the first time delay. The received packet is identified (102) as being a repetition of an immediately-previous data packet based on a time delay between the data packet and the immediately-previous data packet, relative to the first and second time delays.