Methods, systems, and devices for wireless communications are described. A user equipment (UE) may receive an indication of a subcarrier spacing (SCS) for communications in a transmission time interval (TTI), such as a half-subframe, including multiple symbols, corresponding cyclic prefixes, and a padding duration which is at least as long as a symbol duration. The UE may receive a configuration for the padding duration, indicating that at least a portion of the padding duration is reallocated for a reference signal that indicates waveform parameters for one or more symbols of the TTI after the padding duration. The UE may receive the reference signal indicating the waveform parameters during the portion of the padding duration and communicate during the one or more symbols of the TTI according to the waveform parameters.