A method of sidelink communications can include receiving at a user equipment (UE) a configuration for a first resource pool indicating a first size of a first first-stage sidelink control information (SCI) in terms of a number of orthogonal frequency division multiplexing (OFDM) symbols and a second size of the first first-stage SCI in terms of a number of physical resource blocks (PRBs). The first resource pool can be divided into slots in time domain and sub-channels each occupying a set of PRBs in frequency domain. The first first-stage SCI having the first size of the number of OFDM symbols and the second size of the number of PRBs indicated by the configuration for the first resource pool can be transmitted within a first slot and a first sub-channel of the first resource pool.