A mobile communications system is described in which a mobile device is operable to communicate with base stations using a first radio technology and with other devices using a second radio technology. The mobile device maintains a control plane connection with a first base station and a user plane connection via a second base station. In case of an interference is detected due to concurrent use of the first and second radio technologies, the mobile device provides assistance information to the base stations, based on which the base stations alleviate the effects of the detected interference.