A method for causing a user agent to release at least one of uplink and downlink semi-persistent communication resources in a mobile communication system, the method comprising the steps of, at the user agent receiving a downlink communication via a physical downlink control channel (PDCCH), using a semi persistent scheduling radio temporary network identifier (SPS-RNTI) assigned to the device to decode a control message on physical downlink control channel (PDCCH) which may include downlink control information (DCI) in a plurality of DCI fields arranged in a DCI format and where the data from the at least one of the DCI fields is identical to a fixed SPS release value, releasing at least one of the uplink and down link semi-persistent communication resources.