Less Transmissions, More Throughput: Bringing Carpool to Public WLANs

Wei Wang, Yingjie Chen, Qian Zhang, Kaishun Wu, Jin Zhang
2015 2015 IEEE 35th International Conference on Distributed Computing Systems  
A typical scenario for public WLANs is large audience environment where Wi-Fi hotspots serve scores of mobile devices. The performance of those Wi-Fi hotspots is extremely poor in terms of low goodput and severe delay due to heavy contention and MAC inefficiency. After carefully investigating the traffic patterns in public WLANs, we propose Carpool, a practical design that facilitates transmission sharing among multiple receivers, to tackle this problem. The key idea is to reduce contention by
more » ... eeding frames for multiple destinations into one transmission at physical layer (PHY). As such, each downlink transmission carries payloads for multiple receivers, which reduces contention overhead and enables in-time response to concurrent requests from multiple users. To achieve efficient and reliable transmission in Carpool, we propose i) a lightweight frame structure to support multiple receivers, and ii) a realtime channel estimation scheme to continuously calibrate channel estimation during the transmission of a Carpool frame. We have implemented the entire PHY of Carpool on the GNURadio/USRP platform and tested it in various indoor environments. Furthermore, our trace-driven MAC evaluation shows that Carpool achieves up to 3.2× goodput gain and reduces up to 75% delay compared to the IEEE 802.11n MAC frame aggregation scheme.
doi:10.1109/icdcs.2015.100 dblp:conf/icdcs/0050CZWZ15 fatcat:j2535hzmuvbuxmi2aw4ir22j44