Delay-constrained capacity for broadcast erasure channels: A linear-coding-based study

Supporting delay-sensitive traffic is critical to the next-generation communication network. This work studies the 1-to-2 broadcast packet erasure channels with causal ACKnowledgement (ACK), which is motivated by practical downlink access point networks. While the corresponding delay-constrained Shannon capacity remains an open problem (no existing analysis tools can be directly applied), this work focuses on linear codes and proposes three new definitions of delay-constrained throughput based on different outage metrics: the file-based, the rank-based, and the packet-based ones. It then fully characterizes the corresponding linear coding capacity regions for relatively-short-delay flows - flows for which the delay requirement is no larger than the interval of file arrivals.