The Efficient BackFi Transmission Design in Ambient Backscatter Communication Systems for IoT

According to the limited communication distance and the low transmission efficiency for massive electronic tags/sensors of traditional or bistatic backscatter technology, the BackFi transmission protocol design with energy harvesting of massive smart multi-hop electronic tags/sensors was investigated in the ambient backscatter communication systems. This paper proposed the large-scale tags/sensors multi-hop communication protocols with energy harvesting under Wi-Fi architecture, where the “CTS-to-self” frame can be used to set the traditional AP/STA to the sensing status without sending, and then, the new defined frame “Multi-RTS” may send the trigger signal to massive tags or sensors with its frame field as “M-RTS” strategy, compressed bitmap, tags/sensors number, and other messages. The tags/sensors shall respond to the sounding signal and give the backscatter signal to AP using energy harvesting. It can be mentioned that the Wi-Fi standard in this paper is based on the IEEE 802.11ah. Finally, AP can collect and modulate the backscatter signal after massive tags/sensors response to the reader. It was worth noting that the multi-hop relay adopts the power splitting way to implement the communication process, where the object function was energy efficiency maximization with the parameters optimization of transmitting power and relay scaling factor. In order to solve the non-convex problem, this paper derived the approximate expression in the high SNR case and achieved the optimal solution via the Lambert W function. The simulation and analysis verified the effectiveness of the proposed schemes and the correctness of the derivations.