Aspects of the present disclosure provide for random access channel (RACH) configuration in wireless communication systems. In some examples, a RACH configuration may be selected for use by a scheduled entity in transmitting a RACH signal to a scheduling entity based on an estimated timing advance value. The RACH configuration may include, for example, a transmission time of the RACH signal and/or a RACH waveform configuration identifying at least a cyclic prefix (CP) length and a guard time (GT) for the RACH signal. In some examples, the CP and GT length may each be set to the difference between an estimated maximum round-trip time (RTT) and an estimated minimum RTT between the scheduled entity and the scheduling entity. In some examples, the timing advance value may be estimated as the estimated minimum RTT.