A method for throughput enhancement in Wi-Fi backscatter communications using power-level modulation

Wi-Fi Backscatter System with Tag Sensors Using Multi-Antennas for Increased Data Rate and Reliability

“…We propose a demodulation method for determining a data symbol in a Wi-Fi reader with multiple antennas. To compare the performance along the number of antennas between the system proposed in this paper and the existing system in [12], we first transformed the ED method to suit the proposed system, and we additionally described three low complexity demodulation methods proposed to reduce the computational complexity of ED method.…”

“…In Figure 2, we modify the frame structure of the Wi-Fi backscatter system, which uses power level modulation method [12] to suit the proposed system. As shown in Figure 2, the Wi-Fi tag sensor The backscattered signal modulated from the tag sensor changes CSI (in frequency domain) and received a signal strength indicator (RSSI) of a received Wi-Fi packet without directly affecting the data in the Wi-Fi packet.…”

“…In Figure 2, we modify the frame structure of the Wi-Fi backscatter system, which uses power level modulation method [12] to suit the proposed system. As shown in Figure 2, the Wi-Fi tag sensor sends L preamble symbols (training sequence) first before data symbol transmission [12] (the tag sensor can tell its data by changing the Wi-Fi channel between a helper and a reader, and the symbol means the tag's backscatter pattern). Therefore, there is the symbol x k ⊃ preamble p l , data d m in a frame, and k can be summarized as L + M, where L and M are the numbers of preamble and data backscatter symbols, respectively.…”

“…Sensors 2020, 20, 1314 4 of 20 sends preamble symbols (training sequence) first before data symbol transmission [12] (the tag sensor can tell its data by changing the Wi-Fi channel between a helper and a reader, and the symbol means the tag's backscatter pattern). Therefore, there is the symbol x ⊃ {preamble , data } in a frame, and can be summarized as + , where and are the numbers of preamble and data backscatter symbols, respectively.…”

“…where x k is a normalized complex baseband signal transmitted in the k-th symbol interval and z jk is a Gaussian random noise. The variables in Equation (1) can be expressed as a matrix where y jk , H ji , x k , and n jk are expressed as N × T matrix Sensors 2020, 20, 1314 4 of 20 sends preamble symbols (training sequence) first before data symbol transmission [12] (the tag sensor can tell its data by changing the Wi-Fi channel between a helper and a reader, and the symbol means the tag's backscatter pattern). Therefore, there is the symbol x ⊃ {preamble , data } in a frame, and can be summarized as + , where and are the numbers of preamble and data backscatter symbols, respectively.…”