Enhanced intermediate packet delivery in delay tolerant networks

Recently, rateless codes have been employed in packet forwarding protocols of delay tolerant networks (DTNs) to improve the network reliability and to cope with packet loss. However, in intermediate range, where the number of received coded packets is less than the number of source packets, rateless decoder cannot recover any source packets. However, in some applications such as multimedia content delivery partial recovery of source packets from the incomplete received encoded packets is still desired. In this paper, we propose to deliver rateless coded symbols in a certain order to improve the intermediate packet recovery rate. We propose sorted packet forwarding (SPF) and improved SPF (ISPF) that aim to sort coded symbols at source and destination, respectively. Next, we propose modified SPF (MSPF) and modified ISPF (MISPF), which employ a new class of rateless codes to achieve even higher recovery rates compared to SPF and ISPF. Finally, we evaluate the proposed algorithms' performance using numerical simulations, and discuss the pros and cons of each algorithm.