Provided is a technique related to a terminal apparatus, a base station apparatus, a communication system, a communication method, and an integrated circuit that are capable of efficiently performing device-to-device communication. In a case where a terminal apparatus capable of direct communication between terminal apparatuses starts a timer corresponding to a group index that identifies short-range group communication, to which the terminal apparatus belongs, and the timer expires, switching is performed from a first radio resource allocation method, by which a radio resource to be used for the direct communication is requested to a base station apparatus, to a second radio resource allocation method by which the terminal apparatus selects a radio resource to be used for the direct communication.