A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus determines at least one time-frequency resource among resources of a cellular communication system to be used for device-to-device (D2D) communication, identifies a propagated start point of a first portion of the at least one time-frequency resource, and begins transmission of the D2D signal from a transmission start point. The transmission start point is based on the propagated start point and a cellular communication system downlink timing offset to the propagated start point. The apparatus also identifies a propagated end point of a last portion of the at least one time-frequency resource and ends transmission of the D2D signal at a transmission end point. The transmission end point is based on the propagated end point and a cellular communication system downlink timing advance to the propagated end point.