DCCA: Differentiating clear channel assessment for improved 802.11/802.15.4 coexistence

The interaction between devices sharing the same frequency domain, but using different communication protocols, is an important issue prevalent to the Internet of Things (IoT). IEEE 802.11 and IEEE 802.15.4, protocols that overlap in applications such as home automation, health care and factory automation, is one such example. In these situations 802.11 networks are known to detrimentally interfere with 802.15.4 networks, degrading performance significantly. We show that the response to unsuccessful Clear Channel Assessments (CCA) is a large contributor to this degradation. Current responses do not distinguish between different transmission sources, employing the same response independent of the interferer type. However, as we show in this paper, it is beneficial to discriminate interferer types when performing CCA as this allows us to employ different strategies in handling occupied media. Our work considers in particular the low-power Medium Access Control (MAC) protocols based on the 802.15.4 standard. In such protocols, CCA is applied at the transmitter to arbitrate channel access, and also at the receiver for power efficient transmission detection. We present a protocol building block called Differentiating Clear Channel Assessment (DCCA) which allows us to tailor the reaction to a busy channel depending on the nature of the interfering network type. We evaluate an implementation of DCCA for the ContikiMAC protocol on the Maxfor MTM-CM5000MSP platform. The experimental evaluation shows that DCCA improves throughput of 802.15.4 networks in the presence of 802.11 networks significantly, ten-fold in some settings.