Ambient Backscatter Communication With HARQ Assisted Hybrid Long-Short Packets

This letter investigates the performance of an ambient backscatter communication (BackCom) network with hybrid automatic repeat request (HARQ) assisted hybrid long and short packets, where a base station transmits long packets to a cellular user while an Internet of Things (IoT) node performs short-packet BackCom with retransmissions. For the IoT node's short-packet BackCom, we adopt both the HARQ with chase combining (HARQ-CC) scheme and the practical non-linear energy harvesting model and investigate scenarios involving short-packet retransmissions spanning single or multiple cellular transmission blocks, where the closed-form expression for the IoT node's block error rate (BLER) is derived by considering the energy causality constraint and the decoding error in the process of successive interference cancellation. For the cellular long-packet transmission, the outage probability is derived. Simulation results illustrate the correctness of the derived expressions and show that the utilization of the HARQ-CC scheme demonstrates a notable enhancement in the IoT node's BLER performance without observable impact on the outage probability.