Matryoshka: Single RF Chain Multi-user Transmission through WiFi-in-WiFi Signal Emulation using COTS Hardware.

We see a trend toward serving Internet of Things (IoT) devices using the IEEE 802.11 protocol to offer cost-effective solutions. A WiFi AP serving simultaneously both broadband and IoT applications suffers from performance degradation as the slow IoT devices operating on a low modulation and coding throttle down the high-speed broadband devices. In this paper, we present Matryoshka, an approach that exploits the signal emulation technique developed in the context of cross-technology communication (CTC) to create multi-user transmissions from a SISO WiFi AP in the downlink. With such emulated multi-user transmissions, which is a form of hierarchical modulation, it is possible to simultaneously serve a high-speed 802.11 station together with a slow-speed station, which is more efficient than serving them one after another in the time domain. Our approach is a software solution and works with commodity WiFi hardware (COTS). Experimental results from our prototype show the practical feasibility.