A mobile communication system using an enhanced uplink dedicated transport channel transmits data at a relatively low effective data rate through non-scheduled transmission. Data transmission time intervals for user equipments (UEs) have different values in the non-scheduled transmission and therefore uplink interference is reduced. An non-scheduled transmission period N and the number of non-scheduled transmissions k are determined such that each UE performs the non-scheduled transmission. A Node B and each UE are notified of possible non-scheduled transmission time intervals based on the determined non-scheduled transmission period N and the determined number of non-scheduled transmissions k through signaling. The UE transmits the uplink data without the Node B's scheduling at the possible non-scheduled transmission time intervals.