MAC Protocols With Wake-Up Radio for Wireless Sensor Networks: A Review

The use of a low-power wake-up radio in wireless sensor networks is considered in this paper, where relevant medium access control solutions are studied. A variety of asynchronous wake-up MAC protocols have been proposed in the literature, which take advantage of integrating a second radio to the main one for waking it up. However, a complete and a comprehensive survey particularly on these protocols is missing in the literature. This paper aims at filling this gap, proposing a relevant taxonomy, and providing deep analysis and discussions. From both perspectives of energy efficiency and latency reduction, as well as their operation principles, state-of-the-art wake-up MAC protocols are grouped into three main categories: 1) duty cycled wake-up MAC protocols; 2) non-cycled wake-up protocols; and 3) path reservation wake-up protocols. The first category includes two subcategories: 1) static wake-up protocols versus 2) traffic adaptive wake-up protocols. Non-cycled wake-up MAC protocols are again divided into two classes: 1) always-on wake-up protocol and 2) radio-triggered wake-up protocols. The latter is in turn split into two subclasses: 1) passive wake-up MAC protocols versus 2) ultra low power active wake-up MAC protocols. Two schemes could be identified for the last category, 1) broadcast based wake-up versus 2) addressing based wake-up. All these classes are discussed and analyzed in this paper, and canonical protocols are investigated following the proposed taxonomy.