Age-Optimal Network Coding HARQ Transmission Scheme for Dual-Hop Satellite-Integrated Internet

In the upcoming satellite-integrated Internet, a noted limitation is the non-trivial propagation latency due to the long distances. To support the emergent timeliness applications, information must be transmitted within a short end-to-end latency. Hence, the traditional hybrid automatic repeat request (HARQ) strategies with frequent feedbacks do not fit anymore, because the reliable transmission needs retransmission of the lost packets, which inevitably leads to the low efficiency in the satellite-integrated Internet. In this paper, we propose an age-optimal network code HARQ (NC-HARQ) transmission scheme with the metric of information timeliness, i.e., age of information (AoI) to realize limited/no feedback dual-hop reliable transmission in the satellite-integrated Internet. We derive the closed-form expression for the average and peak AoI of the proposed dual-hop age-optimal NC-HARQ transmission scheme, and also the expression for the benchmark schemes through establishing a finite-state Markov chain. Then, by taking account of the time-varying channel and the characteristics of random update of data file, two dynamic forward transmission strategies are further designed. Simulation results illustrate that our dual-hop age-optimal NC-HARQ transmission scheme can achieve lower average and peak AoI in comparison with several state-of-the-art HARQ schemes.