When processing time exceeds applicative timeouts: Concurrent Zigbee/Thread stack evaluation

As Matter protocol aims to unify home automation, the need for compatibility between ecosystems is greater than ever. Currently, wireless gateways in home automation operate on the basis of one radio chipset per protocol, which is neither space nor cost efficient. Internet-of-Things (IoT) in Matter relies on IPv6-based Thread protocol, which uses the same IEEE 802.15.4 physical layer than Zigbee protocol. Exploiting the common physical layer, a nascent technology released by Silicon Labs aims to make Thread and Zigbee coexist on the same radio chipset. Dubbed Concurrent Multi-Protocol (CMP) stack claims to be a prime candidate for interoperability in home automation gateways. It provides futureproofing against new Matter products coming to the market, while still supporting already deployed Zigbee devices. In this paper, we evaluated the performance of the CMP Zigbee/Thread stack. We showed that the retry mechanism of Zigbee applicative layers, and the associated timeouts highly impacts the performance. We compare the performance of a CMP architecture to a two-stack configuration baseline: we show for the same Zigbee and UDP-over-Thread traffic, the two-stack architecture handles the traffic better than the concurrent multiprotocol implementation, due to a longer time processing incoming packets resulting in unjustified applicative retries. Moreover, we show that using an enhanced serial link between the radio coprocessor and the host improves the performance. Finally, we highlight the limitations in a realistic environment use-case, assuming a Zigbee / Matter-over-Thread deployment scenario.