FEC-based AP downlink transmission schemes for multiple flows: Combining the reliability and throughput enhancement of intra- and inter-flow coding

We consider downlink access point (AP) networks and the corresponding reliable transmission schemes. It is well known that one can protect the network traffic against packet erasures by forward-error-correcting-codes (FEC). In addition to ensuring reliable delivery, FECs could substantially reduce the amount of feedback traffic, which is critical when designing high-performance AP protocols.In this work, we generalize the FEC-based schemes, also known as intra-flow coding schemes, for multiple downlink flows. In contrast with the classic approach that performs FEC separately on individual flows, we propose a new protocol MU-FEC, which incorporates the recent idea of inter-flow coding to further enhance the achievable throughput. Specifically, MU-FEC guarantees 100% reliability, is oblivious and robust to the underlying erasure probabilities, has near-optimal throughput higher than any existing inter-flow coding protocols, and can be practically implemented on top of 802.11. The design of MU-FEC consists of three components: batch-based operations, a systematic phase-based network coding decision policy, and smooth integration of inter-flow and intra-flow coding. We analytically show that MU-FEC can achieve much higher throughput than intra- or inter-flow coding alone, and validate its performance gain via extensive simulations. To our knowledge, MU-FEC is the first practical protocol that leverages both intra-flow and inter-flow network coding to solve a real-world problem in single-hop wireless networks.