A source node estimates not only the schedule time offset of the destination node but also the clock drift of the destination node. In this way, the source node may choose very accurately the transmission start time of an information packet to this destination node so that typically only one very short preamble needs to be transmitted. The estimation of time offset and clock drift between two nodes is achieved through tone or more previous transmissions between these two nodes, in particular, information relating to these parameters is transmitted from the destination node to the source node in reply to a preamble transmitted by the source node to the destination node.