Performance Analysis for Relay Assisted Short-Packet Backscatter Communications

Most of works on backscatter communication (BackCom) assume the availability of a direct link from the BackCom transmitter to its receiver and the long-packet transmission for BackCom. However, the above assumptions may be inapplicable in some practical Internet of Things (IoT) applications, e.g., industrial automation. Motivated by this, this paper proposes and studies a relay assisted short-packet BackCom network, where a full-duplex relay (R) with two antennas and an energy self-sustaining IoT node form a monostatic short-packet BackCom paradigm in the first phase while R forwards the IoT’s short-packet information to the information receiver (IR) in the second phase via a decode-and-forward (DF) or amplify-and-forward (AF) relaying protocol. For a given DF or AF relaying protocol, we propose to optimize the power allocation factor of two antennas at R in the second phase to minimize the IoT node’s average block error rate (BLER), and derive the optimal solution in the closed form. With the optimal power allocation factor, we derive the analytical expressions of the IoT node’s average BLER under the DF and AF protocols while considering the residual self-interference at R and the energy causal constraint at the IoT node. Simulation results verify the correctness of the derived expressions and reveal the impacts of various parameters such as the IoT node’s short-packet blocklength and power reflection coefficient on the average BLER. It is found that when the short-packet blocklength increases, the average BLER decreases until it reaches a certain value.