A novel multi-hop ARQ concept

Wireless multi-hop communication has recently gained a lot of interest in the research community as an approach to provide improved coverage compared to single-hop wireless networks. While most studies focus on routing protocols, ARQ mechanisms for multi-hop wireless links have found little attention so far. In this paper, we propose a novel link layer concept for reliable and efficient transmission in multi-hop environments that we name RelayARQ. The distinguishing feature of RelayARQ is that it establishes a single connection in which a common protocol state is shared between the end nodes and all relay nodes. The protocol state maintained in relay nodes is a soft-state, which allows relay nodes to seamlessly "leave and join" without breaking the RelayARQ connection. The key idea behind RelayARQ is the concept of relay-acknowledgements (RACKs). A relay node sends a RACK towards its sending peer to indicate that it has correctly received a data unit. On receiving a RACK, the sending peer temporarily delegates the retransmission responsibility to the relay node. The ultimate responsibility, however, remains with the sender node until the receiver node acknowledges the successful delivery of the data unit. Based on these features RelayARQ provides reliability between the end nodes as well as high performance and resource efficiency.