A network node and a user device are provided. The network node comprises a processor to determine for each of the plurality of user devices a corresponding check element position of a corresponding check element in a control information message addressed to the user device; a transmitter to transmit a first control signal (CS1) to each of the plurality of user devices, the CS1 indicating the determined corresponding check element position. The user device comprising: a receiver to receive a CS1 indicating a corresponding check element position of a check element associated with the user device in a control information message (M), the control information message (M) comprising control information (d) and at least two check elements, a processor to derive the corresponding check element position of the check element associated with the user device from the CS1.