AirExpress: Enabling Seamless In-band Wireless Multi-hop Transmission

This paper describes the design and implementation of AirExpress, a system that enables in-band wireless cut-through transmission. Unlike wired cut-through, wireless cut-through can reduce latency and improve throughput performance of the network at the same time. In AirExpress, all the forwarders along the cut-through path forward the signal they received immediately without decoding. The hierarchical structure of AirExpress enables its interference cancellation ability to handle all kinds of interference among the radios. Novel MAC and routing algorithms based on cut-through transmission are also proposed to support the realization of AirExpress in multi-hop mesh networks. AirExpress is implemented on an NI-based SDR platform. Through experiments in the 2.4GHz ISM band, we show throughput gain of up to 3.4 times with a 4-hop AirExpress system. Trace driven evaluation of AirExpress on the NS3 platform shows an average throughput gain of 2.85 for AirExpress over optimal TDMA.