A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus may be a UE. The apparatus may transmit a message in a first subset of a set of resources. The message may include a position of the apparatus and a resource ID indicating at least one symbol in a second subset of the set of resources for transmitting a sequence. The apparatus may transmit the sequence in the at least one symbol in the second subset of the set of resources identified by the resource ID, receive at least one other sequence, adjust a transmission timing based on the received at least one other sequence, and transmit, based on the adjusted transmission timing, the sequence in one or more symbols in a third subset of the set of resources.