Channel Estimation and Pilot Design for Ambient Internet of Things with Frequency Offsets

Recently backscatter communications and Ambient Internet of Things (A-IoT) arouse extensive interest from both academia and industry. One key parameter for A-IoT is frequency offset (FO), including carrier frequency offset (CFO) and sampling frequency offset (SFO), which is often neglected by existing studies. In this paper, we investigate the channel estimation and optimal pilot design for A-IoT with frequency offsets. Specifically, we first propose a joint FOs and channel estimator and then derive the corresponding Cramer-Rao Bounds (CRBs) for the channel estimates. We then suggest the optimal pilot design for the tag with on-off keying and binary phase shift keying modulation schemes. Finally, extensive numerical results are provided to corroborate our proposed studies.