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Abstract-Disruption Tolerant Networks (DTNs) are designed to overcome limitations in connectivity due to conditions such as mobility, poor infrastructure, and short range radios. DTNs rely on the inherent mobility in the network to deliver packets around frequent and extended network partitions using a store-carry-andforward paradigm. However, missed contact opportunities decrease throughput and increase delay in the network. We propose the use of throwboxes in mobile DTNs to create a greater number of contact opportunities, consequently improving the performance of the network. Throwboxes are wireless nodes that act as relays, creating additional contact opportunities in the DTN. We propose algorithms to deploy stationary throwboxes in the network that simultaneously consider routing as well as placement. We also present placement algorithms that use more limited knowledge about the network structure. We perform an extensive evaluation of our algorithms by varying both the underlying routing and mobility models. Our results suggest several findings to guide the design and operation of throwbox-augmented DTNs.

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IEEE 802.15.4 (used by Zigbee, 6LoWPAN and Thread) and Bluetooth Low Energy (BLE) are two widely used wireless standards for ultra low power IoT (Internet of Things) technologies and smart home applications. In this article, we present the first comparison of the physical layer of the two protocols, focusing on two performance metrics: energy efficiency and wireless coverage. The comparison uses the first radio that seamlessly supports both protocols; therefore, the protocols are compared on identical hardware and software. By combining the two metrics, we quantify the performance, and identify in which types of links it is preferable to use one protocol or the other, thus providing practical guidelines to developers of short-range energy-constrained wireless networks and smart home applications.