Implementing QZMAC (a Decentralized Delay Optimal MAC) over 6TiSCH under the Contiki OS in an IEEE 802.15.4 Network

TL;DR

This paper implements and evaluates the QZMAC protocol, a decentralized, delay-optimized MAC designed for IoT networks, demonstrating its effectiveness over 6TiSCH in Contiki OS with real hardware.

Contribution

The paper presents the first implementation and experimental validation of QZMAC on real IoT hardware using 6TiSCH and Contiki OS, showcasing its low delay performance.

Findings

QZMAC achieves near-optimal delay in practical IoT testbeds.

The protocol maintains good performance under WiFi interference.

Separate demonstration of polling and contention modes.

Abstract

Motivated by the emerging delay-sensitive applications of the Internet of Things (IoT), there has been a resurgence of interest in developing medium access control (MAC) protocols in a time-slotted framework. The resource-constrained, ad-hoc nature of wireless networks typical of the IoT also forces the amount of control information exchanged across the network -- required to make scheduling decisions -- to a minimum. In a previous article we proposed a protocol called QZMAC that (i) provides provably low mean delay, (ii) has distributed control (i.e., there is no central scheduler), and (iii) does not require explicit exchange of state information or control signals. In the present article, we implement and demonstrate the performance of QZMAC on a test bed consisting of CC2420 based Crossbow telosB motes, running the 6TiSCH communication stack on the Contiki operating system over the 2.4GHz ISM band. QZMAC achieves its near-optimal delay performance using a clever combination of polling and contention modes. We demonstrate the polling and the contention modes of QZMAC separately. We use an Adaptive Synchronization Technique in our implementation which we also demonstrate. Our network shows good delay performance even in the presence of heavy interference from ambient WiFi networks.