1. A terminal apparatus which communicates with a base station apparatus by using multiple serving cells including a primary cell and one or multiple secondary cells, comprising:medium access control layer processing circuitry configured to initiate a random access procedure for a secondary cell based on a single reception of a Physical Downlink Control CHannel (PDCCH) order;
a transmitter configured to transmit a first random access preamble; and
a receiver configured to receive a random access response,
the transmitter is further configured to transmit a second random access preamble after the transmitter transmits the first random access preamble,
the medium access control layer processing circuitry, in a case that (a) reception of the random access response is considered not successful and (b) the first random access preamble was transmitted on the secondary cell, determines whether to transmit the second random access preamble based on the single reception of the PDCCH order, based on a configuration of a higher layer, and
the transmitter resumes, based on a second PDCCH order, random access preamble transmission to transmit the second random access preamble, in a case that the medium access control layer processing circuitry determines, based on the configuration, that the transmitter does not transmit the second random access preamble based on the single reception.