Investigation of Power Levels and Phase Variations from Interference between Bi-Static Ambient Backscattered and Direct Signals in 5G-NR Free Space Scenario

This paper addresses several key challenges in bistatic ambient backscatter communication (AmBC) regarding the direct path interference (DPI) problem, contributing to both theoretical insight and practical feasibility. To predict the power of the backscattered signal (BS) from the total power in the presence of an interfering direct signal without using complex signal processing algorithms, a power-centric theoretical model based on the phase difference of the interference between the AmBC signal and the direct signal (DS) is proposed for 5 G-NR free space. As a first approach, only a direct continuous wave (CW) signal at 3.5 GHz was considered. Knowing the BS power level is important for estimating the potential AmBC range. Knowing the ratio of AmBC power to the direct signal power (in dB) is also important for a robust reception of the AmBC signal without interfering with the active communication systems. Predicting this ratio allows to check if AmBC could co-exist with active communication by examining the interference at the legacy receiver (LR).