Abstract-The use of drone base stations to provide wireless connectivity for ground terminals is becoming a promising part of future technologies. The design of such aerial networks is however different compared to cellular 2D networks, as antennas from the drones are looking down, and the channel model becomes height-dependent. In this paper, we study the effect of antenna patterns and height-dependent shadowing. We consider a random network topology to capture the effect of dynamic changes of the flying base stations. First we characterize the aggregate interference imposed by the cochannel neighboring drones. Then we derive the link coverage probability between a ground user and its associated drone base station. The result is used to obtain the optimum system parameters in terms of drones antenna beamwidth, density and altitude. We also derive the average LoS probability of the associated drone and show that it is a good approximation and simplification of the coverage probability in low altitudes up to 500 m according to the required signal-to-interference-plusnoise ratio (SINR).

Bluetooth Low Energy (BLE) represents the low-power, low-cost extension of the Bluetooth communication technology envisioned for the Internet of Things. Mesh protocols on top of BLE are currently emerging and the standard is currently being released. This paper first proposes a detailed measurement based comparison of two mesh approaches that fit within BLE operation: flooding and connection oriented networking. Using metrics such as packet delivery ratio (PDR), end-to-end delay and power consumption we conclude that the optimal mesh approach depends on the application. It is shown that for a comparable performance in terms of PDR and overhead, flooding can trade a lower end-to-end delay for a higher power consumption when compared to the connected mesh. We then propose an architecture, called Bluetooth Now, that is able to automatically switch the network between the two based on message priority. Our measurement results confirm the reliable delivery of important and urgent data sent using the Bluetooth Now paradigm, while saving battery life when transmitting non-time critical messages.

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Bluetooth Low Energy (BLE) is envisioned as one of the most prominent technologies for the Internet of Things (IoT). The recent release of BLE mesh has attracted interest from both the industrial and academic communities, with new proposals for optimizing its performance being published on a regular basis. However, the majority of these publications rely on analysis and simulations, potentially neglecting the effect of real life environments and hardware limitations. Moreover, no framework is available to experimentally compare the performance of different mesh protocols on top of BLE. This paper presents the design and implementation of a low-cost, modular and fully automated testbed capable of running multiple mesh protocols. It is also remotely accessible for any third party interested in performing network experiments with it. Apart from discussing the testbed architecture, we provide results obtained from a measurement driven comparison of two protocols that fit within BLE operation: flooding and connection based. These results show that there is a trade off between the two approaches and that the optimal mesh protocol to use is application dependent, which should be taken into consideration when heading towards the next release of BLE mesh.

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