QUATTRO: QoS-Capable Cross-Layer MAC Protocol for Wireless Sensor Networks

As the wireless sensor network (WSN) technology evolves towards higher transmission rates, it makes sense to start considering sensing and transmission of real-time information, such as audio and video. These applications require quality of service (QoS) guarantees, not offered by current networks. The multi-hop nature of WSN makes QoS a challenging task. In addition, researchers have recently realized that cross-layer protocols achieve a far better performance than protocol layers working in isolation. These two ingredients are the focus of our work. In this paper we propose an architecture in which the MAC and routing protocols collaborate to discover and reserve routes, to organize nodes into clusters and to schedule the access to the transmission medium in a coordinated time-shared fashion. As a consequence, not only QoS is achieved but also great energy savings by eliminating collisions and considerably reducing idle listening. The resulting protocol is called QUATTRO: QUAlity-of-service-capable clusTer-based Timeshared ROuting-assisted MAC protocol. We evaluate our proposal using simulations by examining multiple scenarios in which different numbers and densities of nodes are considered. Our results show that the protocol overhead is reasonable.