A terminal of a communication system transmits a first signal through a physical uplink channel that is allocated within a first radio resource based on a first Transmission Time Interval (TTI) having a first time length at a first step for uplink access, performs the remaining steps for the uplink access using a second radio resource based on the second TTI from a base station, when the terminal may operate based on a second TTI having a second time length smaller than the first time length, and transmits uplink data.