Using Radio Frequency (RF) signals as a way of sensing has seen great popularity and promising results in existing research. However, the technology is limited by the fact that an object has to be located between a transmitter and a receiver in order to be observable by such a system. While many publications have addressed this limitation by leveraging multipath propagation effects, these are often only found in closed indoor environments. In this paper, we introduce a novel method to utilize RF sensing from a distance that does not rely on multipath effects, allowing it to be used in scenarios where it would have previously been considered impractical such as outdoor applications. By receiving the ground reflection of a signal, we measure objects within its path as the signal propagates through them. This allows combining both antennas into a single compact unit that can be pointed at an object from a distance. We perform a series of experimental evaluations to gather preliminary data on the feasibility and performance of this approach. Using our setup, we are able to count water bottles positioned underneath the sensor with high accuracy based solely on the received signal strength of the reflected component.

Low Earth Orbit (LEO) satellite networks like Starlink are susceptible to both external factors (e.g., weather and obstruction) and internal factors such as frequency and resource allocation changes. This causes performance instabilities by design. In this demo, we show that such instabilities can have a detrimental impact on the performance of TCP and consequently on large parts of today’s internet, as most traffic uses TCP as transport protocol. Consequently, LEO-specific adaptations to either TCP and/or higher-level applications are necessary.

Indoor localization based on wireless communication networks has attracted a lot of attention in research. It can deliver better accuracy than a traditional Global Navigation Satellite System (GNSS) and operate in environments where satellite signals can not be received. Although more accurate methods have been published, fingerprinting based on Received Signal Strength (RSS) remains interesting. Such a system can be deployed on top of most existing networks without imposing additional requirements or restrictions to the communication. However, existing solutions usually require a larger number of base stations with known locations (anchors) within a mobile node’s reception range. This is required to prevent ambiguous fingerprints and deliver accurate results. However, it also increases the network’s energy consumption and operating cost. In this paper, we present a new approach that uses multi-frequency fingerprints to eliminate this requirement and operates with only a single anchor node while achieving accuracy that is comparable to existing solutions. In order to efficiently collect RSSI fingerprints across multiple frequencies, we introduce a measurement methodology using Software Defined Radio (SDR).

Wireless transmission of images in real time over large distances is a challenge for applications such as agricultural UAV-based remote sensing. The Wifibroadcast project uses standard WiFi hardware to provide a purely unidirectional transmission link for such situations. This paper examines the trade-off between image compression and FEC for image transmission via Wifibroadcast. The goal is to achieve highest robustness against transmission errors with regards to visual quality. For this, we conducted two experiments: First, we implemented a complete simulation of the transmission process to assess different degrees of packet and byte corruption. Afterward, we incorporated real network traces into the simulation in order to model realistic corruption patterns. The results show that for uniformly distributed byte corruption patterns, compression in combination with redundancy does not yield benefits to visual quality. However, if packet loss is the dominating corruption source, FEC is able to make image transmission more robust.

Some core advances in the early research on wireless networks have been made with simple analytical models for collisions. While complex simulations are nowadays often used to evaluate such networks, the more simple analytical models are still helpful for gaining fundamental understanding of effects. One challenge in using such models is finding appropriate parameters for them. To facilitate quick plausibility checks on these models, ready-to-use parameter sets for realistic example networks are desirable. In this paper, we provide such parameter sets for two networks, one in an office building and one in an industrial facility.

Using existing general purpose wireless technologies, it is difficult to transmit large amounts of data from Unmanned Aerial Vehicles (UAVs) to a ground station during flight. Thus, there is a demand for specialized solutions. Wifibroadcast proposes a solution for this use case, utilizing a unidirectional and connectionless design to transmit data using unmodified low-cost WiFi hardware. In this paper, we measure and evaluate the performance of Wifibroadcast for UAV to ground transmissions over large distances and provide a direct comparison against standard IEEE 802.11. We demonstrate that Wifibroadcast is able to outperform WiFi in all tested scenarios while identifying specific characteristics, limitations, and requirements of a long-distance transmission on both the 5 GHz and 2.4 GHz frequency bands.

The quality of Bluetooth Low Energy (BLE) connections can be improved by deactivating wireless channels when external interference is detected. The BLE standard contains basic requirements to implement this behavior. However, it does not specify how channels should be classified and disabled, leaving the details up to the implementations. In this paper, an implementation is presented and evaluated, based partially on existing work. A new algorithm for re-activating channels that were previously disabled in order to allow for operation in dynamic environments with changing background interference is proposed and demonstrated to deliver improvements over existing work, resulting in better connection stability. Finally, an evaluation under real-world conditions confirms the improvements to BLE connections that were previously only shown in controlled testing environments.