  Internet-of-Things (IoT) is rapidly growing in wireless technology, aiming to
connect vast numbers of devices to gather and distribute vital information.
Despite individual devices having low energy consumption, the cumulative demand
results in significant energy usage. Consequently, the concept of
ultra-low-power tags gains appeal. Such tags communicate by reflecting rather
than generating the radio frequency (RF) signals by themselves. Thus, these
backscatter tags can be low-cost and battery-free. The RF signals can be
ambient sources such as wireless-fidelity (Wi-Fi), cellular, or television (TV)
signals, or the system can generate them externally. Backscatter channel
characteristics are different from conventional point-to-point or cooperative
relay channels. These systems are also affected by a strong interference link
between the RF source and the tag besides the direct and backscattering links,
making signal detection challenging. This paper provides an overview of the
fundamentals, challenges, and ongoing research in signal detection for AmBC
networks. It delves into various detection methods, discussing their advantages
and drawbacks. The paper's emphasis on signal detection sets it apart and
positions it as a valuable resource for IoT and wireless communication
professionals and researchers.
