Average Packet Decoding Delay Minimization for Rate-Aware Buffered Instantly Decodable Network Codes

Buffered instantly decodable network coding (B-IDNC) can cache the non-instantly decodable network packets (NIDPs) containing two wanted packets for subsequent network decoding. This letter proposes a cross-layer scheme named as rate-aware B-IDNC (RA-B-IDNC) by jointly considering the B-IDNC decision at the network layer and transmission rate adaption at the physical layer to minimize the average packet decoding delay. Due to the intractability of the considered problem, we approximate it as maximizing the recovery rate which is defined as the ratio of the total number of instantly decoded packets to the transmission time. We design two graphs named as RA-B-IDNC encoding graph which reflects the encoding relations among the vertices of the graph, and RA-B-IDNC decoding graph which indicates the decoding relations among the wanted packets of each receiving node by exploiting its buffered NIDPs. Using these graphs, the approximated problem can be formulated as a maximum weight encoding clique problem. Simulation results demonstrate that RA-B-IDNC can reduce the average packet decoding delay compared with the existing algorithms in the literature.