EasyPass: combating IoT delay with multiple access wireless side channels

Many IoT applications have stringent requirements on wireless transmission delay, but have to compete for channel access with other wireless traffic. Traditional techniques enable multiple access to wireless channels, but yield severe delay when the channel is congested. In this paper, we present EasyPass, a wireless PHY technique that allows multiple IoT devices to simultaneously transmit data over a congested wireless link without being delayed. The key idea of EasyPass is to exploit the excessive SNR margin in a wireless channel as a dedicated side channel for IoT traffic, and allow multiple access to the side channel by separating signals from different transmitters on the air. We implemented EasyPass on software-defined radio platforms. Experiment results demonstrate that EasyPass reduces the data transmission delay in congested IoT networks by 90%, but provides a throughput up to 2.5 Mbps over a narrowband 20MHz wireless link that can be accessed by more than 100 IoT devices.