Fine-grained Frequencies to Combat Cross Technology Interference in IoT: A Measurement Study

In this paper we show a possible way to deal with the problem of severe WiFi interference in low power WSN/IoT-edge in the 2.4 GHz ISM band. Through extensive multi-frequency link-measurement experiments we demonstrate that under heavy congestion when the frequency band is fully occupied by WiFi channels, the multi-channel protocols for low power ZigBee communication should try to exploit all the 1 MHz separated 80 different frequencies instead of sticking to only the 16 standard channels. Through an in-depth analysis of the outdoor link measurement data we observe that the availability of the usable frequencies follows a well-known lévy characteristics. Exploiting this special property, we propose an efficient frequency searching mechanism that can quickly find a suitable frequency when the current operating frequency degrades. Our trace-based simulation results show that the proposed strategy can perform upto 80% faster compared to the naive random probe based searching.