Noncoherent Detections for Ambient Backscatter System
Abstract: Ambient backscatter, an emerging communication mechanism where battery battery-free devices communicate with each other via backscattering ambient radio frequency (RF) signals, has achieved much attention recently because of its desirable application prospects in the Internet of Things. In this paper, we formulate a practical transmission model for an ambient backscatter system, where a tag wishes to send some low low-rate rate messages to a reader with the help of an ambient RF signal source, and then provide fundamental sstudies tudies of noncoherent symbol detection when all channel state information of the system is unknown. For the first time, a maximum likelihood detector is derived based on the joint probability density function of received signal vectors. In order to ease av availability of prior knowledge of the ambient RF signal and reduce computational complexity of the algorithm, we design a joint joint-energy energy detector and derive its corresponding detection threshold. The analytical bit error rate (BER) and BER BER-based outage probability ility are also obtained in a closed form, which helps with designing system parameters. An estimation method to obtain detection-required detection required parameters and comparison of computational complexity of the detectors are presented as complementary discussions. Sim Simulation ulation results are provided to corroborate theoretical studies.