Packet Encoding for Data Freshness and Transmission Efficiency with Delayed Feedback

This paper investigates the tradeoff between data freshness and transmission efficiency for packet delivery over erasure channels with delayed feedback. First, we show that the transmission efficiency of the preemptive last-generated-first-served (pLGFS) policy degrades drastically with the feedback delay. To address this issue, we propose a new coding scheme by incorporating the pLGFS policy with a selective packet encoding strategy. Specifically, the transmitter estimates the packet reception status based on the delayed feedback information, and then decides whether to remain silent, or to send the latest information packet or a coded packet. The proposed transmission policy can achieve flexible tradeoff between data freshness and transmission efficiency by adjusting the decision and coding parameters. In particular, compared with the pLGFS policy, the proposed policy can greatly enhance the transmission efficiency, with only a slight degradation of data freshness.