Intra-Symbol Differential Amplitude Shift Keying-Aided Blind Detector in AmBC Systems

Ambient backscatter communication (AmBC) is a crucial technology for addressing the energy consumption challenge in green Internet of Things through the reflection or absorption of surrounding radio frequency (RF) signals. Nevertheless, it grapples with the intricacies of ambient RF signal and the round-trip path loss. For the traditional detectors, the incorporation of pilot sequences results in the reduction in spectral efficiency. Furthermore, traditional energy-based detectors are inherently susceptible to a notable error floor issue, attributed to the co-channel direct link interference (DLI). Consequently, this paper proposes a blind symbol detector without the prior knowledge concerning the channel state information, signal variance, and noise variance. Leveraging the intra-symbol differential amplitude shift keying (IDASK) scheme, this detector effectively redirects the majority of DLI energy towards the largest eigenvalue of the received sample covariance matrix, thereby utilizing the second largest eigenvalue for efficient symbol detection. Simulation results demonstrate that the proposed blind detector exhibits a significant enhancement in symbol detection performance compared to traditional counterparts.