## 1 Introduction
But for the scenarios we consider, node densities are generally higher than those in deep space ONs, with higher traffic and much lower tolerance for delay. These transport protocols will incur network congestion and unacceptable latency when a huge traffic burst emerges in human ONs. For terrestrial ONs, protocols based on rateless coding (network coding or erasure coding such as Luby transform (LT) codes and Reed-Solomon (RS) codes) are widely considered as a promising solution to enhance the reliability of ONs [15; 16; 17], thus getting more and more attention. With coding, the successful reception of a file no longer depends on receiving specific packets, but on receiving a sufficient number of individual packets, whereas without coding, the loss of a packet has to be compensated by retransmitting the same packet. Thus, the coding-based protocols can offer resilience to link failures, increase throughput, and reduce the delivery delay [18; 19]. Several coding-based schemes have shown that deterministic forms of reliable transport in ON can be allowed by integrating receivers' acknowledgements (ACKs) [20; 21]. Nevertheless, these solutions rely on considerable redundancy/forwarding to cater the packet losses in the network and increase the probability of the message arriving at its destination, thus obtaining acceptable latency at the cost of energy resources [22]. Therefore, they are well suited for some scenarios where network resources such as cache and energy are rich to use. However, they make the assumption that all relays are willing to participate in the routing process, which is not necessarily the case in real-life human ONs. To be specific, since network resources in realistic human society are limited, relays tend to be selfish when they are low on these resources, which we refer to as selfish nodes. A selfish node may choose not to receive packets from other nodes in order to save its resources for future use (such as energy-conserving sleep schedules). Consuming a lot of energy/cache to get a satisfactory delay will trigger the selfish behavior of considerable relays, which can lead to the noncooperation of relays. As a result, the performance of these schemes will be degraded. Therefore, to enhance the reliability of real-life human ONs, the transport scheme should take file delivery delay as well as the resource consumption into account. There are a few transport schemes for ONs to date to consider the resource consumption in the minimization of delay. [PERSON] et al. [PERSON] et al. (2018) proposed a reliable transport protocol based on coding and ACKs aiming at minimizing the round-trip file delay by controlling the allocation of the limited cache for source packets and ACKs dynamically. When constructing the network model, they assumed that only one packet can be stored per node, and adopted the cache management rule in which the source packets and acknowledgements competed for the rare cache, which was defined as the \"half-duplex\" feature. However, they neglected the influence of continuous energy consumption on the network performance. Although the authors proposed an improved version which took the energy consumption of the network into account, they still focused on optimizing the delivery delay by allocating the limited cache space, and simply setting an upper limit on energy consumption ([PERSON] et al., 2018). Therefore, an optimal trade-off between energy consumption of relays and the delivery delay remains to be further studied. In this paper, our goal is to develop a more reliable transport scheme by achieving the optimal trade-off between the two metrics: We make use of acknowledgements and coding at the source. For the sake of concentrating on the influence of energy consumption on the performance of the scheme, we adopt a loosen cache management rule that there is no contention between the source packets and acknowledgements for storage, which is defined as the \"full-duplex\" strategy. Then an analytical model is set up to describe the evolution of packets dissemination.