Method and arrangement in a base station for providing feedback to user equipments in a cell concerning the reception status of data received from the user equipments. The base station and the user equipments are comprised in a wireless communication system, adapted for contention based transmissions. The method comprises sending a contention based grant to a plurality of user equipments within the cell, receiving data from any user equipment and verifying if the data is correctly received. Also, the method comprises sending feedback to any user equipment that has used the contention based grant, wherein the feedback comprises an ACK, if it is verified that data has been correctly received from at least one user equipment and the feedback comprises a NACK if it is verified that data has not been correctly received from any user equipment. Also, a corresponding method and arrangement in a user equipment is described.