A backscatter transmission scheme is provided in which a carrier signal is transmitted by a carrier communication device discontinuously as carrier signal bursts. The carrier signal, while it is on, is divided into carrier time segments. Each carrier time segment has a specified time. The different carrier time segments represent different times that backscatter devices can make backscatter transmissions. In addition, in some embodiments, a set of frequencies are available for backscatter transmission. The set of frequencies includes the carrier frequency and a set of frequencies with respective frequency shifts relative to the carrier frequency. The combination of a specific carrier time segment, a specific frequency shift, together constitutes a specific backscatter transmission opportunity.