Determination Scheme for Detection Thresholds Using Multiple Antennas in Wi-Fi Backscatter Systems

In this paper, a detection scheme for the uplink transmission of Wi-Fi backscatter system is proposed. In the uplink transmission, a backscatter tag modulates signals from a Wi-Fi access point by backscattering. Since the reflection occurs, the backscattered signal experiences more attenuation than the direct Wi-Fi signals to a Wi-Fi reader. Most recent studies focus on effective detection techniques to increase the coverage of the backscatter tag in the poor signal to interference plus noise ratio environment. This paper proposes an improved detection scheme using multiple antennas at the reader. At the reader, the backscattered signals are received by multiple antennas and thresholds are determined appropriately for improvement of detection performance. Typically the methods using multiple antennas require channel information. However the channel estimation for the uplink of backscatter system is difficult since the backscattered signals are weak. The detection method of this paper does not require the channel information for the uplink. Simulation results show improved performance and possibility for the increase of coverage.