Bertold Van den Bergh

Micro aerial vehicle networks: an experimental analysis of challenges and opportunities

The need for aerial networks is growing with the recent advance of micro aerial vehicles, which enable a wide range of civilian applications. Our experimental analysis shows that wireless connectivity among MAVs is challenged by the mobility and heterogeneity of the nodes, lightweight antenna design, body blockage, constrained embedded resources, and limited battery power. However, the movement and location of MAVs are known and may be controlled to establish wireless links with the best transmission opportunities in time and space. This special ecosystem undoubtedly requires a rethinking of wireless communications and calls for novel networking approaches. Supported by empirical results, we identify important research questions, and introduce potential solutions and directions for investigation.

CLAWS: Cross-Layer Adaptable Wireless System enabling full cross-layer experimentation on real-time software-defined 802.15.4

MotivationIn recent years, researchers have developed a large and growing set of protocols and algorithms to improve the throughput and capacity of wireless networks. These schemes span the physical (PHY), medium access control (MAC), and higher layers of the protocol stack. Most effective innovations however require cross-layer modifications of both PHY and higher layers. To date, the verification of those designs has been limited to simulations or small setups relying often on off-line processing of the results. MAC layer results that rely on even the tiniest modification of the PHY can only be verified under simplified networking assumptions. Similarly, novel PHY algorithms are typically only verified for a single wireless link, avoiding complex scenarios. Most importantly, there is almost no cooperation between PHY and networking communities, as the tools and testbeds they use are incompatible.ContributionsIn this paper, we propose a methodology for fully flexible PHY, MAC, and network layer verification that is designed to (a) reuse existing software components from PHY and network communities, (b) enable both simple- and expert-level modification and configuration of all components, (c) have real-time performance benchmarked with off-the-shelf systems, and (d) enable large networking experiments including off-the-shelf nodes for rapid experimentation, testing, and comparison. The main contribution of this paper is the introduction of an approach that enables the realization of full software-defined radio (SDR) sensor nodes, all running on a single field-programmable gate array and reusing PHY layer SDR tools and typical operating systems such as Contiki OS. Subsequently, the paper will illustrate the strengths of the proposed approach by demonstrating communication with off-the-shelf sensor nodes. This allows fair benchmarking with state-of-the-art or off-the-shelf solutions. Finally, some cross-layer improvements are proposed and compared with the baseline off-the-shelf system. This proves our claims that the proposed platform is a very useful tool for cross-layer experimentation, in that it allows full cross-layer control of the PHY and network layers, and moreover enables elegant comparison with state-of-the-art designs. This architecture is provided to the open source community (http://claws.be/), in order to become a framework for validating and benchmarking wireless cross-layer innovations.

Analysis of Harmful Interference to and from Aerial IEEE 802.11 Systems.

Civil Unmanned Aerial Vehicles (UAVs) enable a manifold of exciting new services. UAVs are about to be part of our everyday lives. The range of applications is very broad, ranging from swarms of UAVs that can be used for 3D modeling and surveillance of large areas, to search and rescues and fire fighter missions. An important cornerstone for the development of civil UAVs is communication technology. To ensure lightweight and cheap UAV technology, it is necessary to use existing commodity communication technology and chip-sets for UAV communications. Yet, the impact of the novel aerial and high altitude propagation context on those technologies needs to be understood. In this paper, we analyze the performance of IEEE 802.11 communication, both experimentally and by means of simulation. It is shown that the aerial context results in very different communication performance for an 802.11 network compared to the typical terrestrial context. Decreased shadowing gives a larger number of networks that can be seen, resulting in higher interference and packet loss due to collisions.

Electrosense: Open and Big Spectrum Data

While radio spectrum allocation is well regulated, there is little knowledge about its actual utilization over time and space. This limitation hinders taking effective actions in various applications including cognitive radios, electrosmog monitoring, and law enforcement. We introduce Electrosense, an initiative that seeks a more efficient, safe and reliable monitoring of the electromagnetic space by improving the accessibility of spectrum data for the general public. A collaborative spectrum monitoring network is designed that monitors the spectrum at large scale with low-cost spectrum sensing nodes. The large set of data is stored and processed in a big data architecture and provided back to the community with an open spectrum data as a service model, that allows users to build diverse and novel applications with different requirements. We illustrate useful usage scenarios of the Electrosense data.

IEEE 5G Spectrum Sharing Challenge: A Practical Evaluation of Learning and Feedback

We present the results, experiences, and takeaways from comparing a diverse set of dynamic spectrum access methods during the IEEE DySPAN 2015 spectrum challenge. Five solutions for coexistence with a given wireless link were implemented and tested in an unknown environment during the conference in Stockholm. The challenge was framed broadly, enabling participants to use their own hardware, antennas, physical layer, or medium access control solutions to compete in a unified setup. Each solution was run two times and ranked using a single metric. Between the two runs the teams were allowed to improve their solution. The metric considered wanted throughput and unwanted interference. In addition to the metric, all solutions were evaluated by a jury. In this article, we give a detailed overview of the challenge, how we organized it, the participating teams, and finally the winners. We conclude with some takeaways on dynamic spectrum access.

Electrosense: Crowdsourcing spectrum monitoring

We present Electrosense: a distributed, collaborative and low-cost wireless spectrum monitoring solution which is deployed on a large scale. The proposed framework provides tools to enable and promote a crowdsourced open spectrum monitoring platform for wide area deployments. The collected spectrum data is stored and processed in the backend which can be easily retrieved by the users through an open API. The framework also allows using various signal processing algorithms deployed on the sensors as well as in the backend. These algorithms provide statistics on spectrum usage, collaborative spectrum data decoding, help in applications like anomaly detection and localization. The goal of the demo is to introduce the framework, show the infrastructure already deployed, how to join the network and demo a few built-in applications.

Multidisciplinary Learning through Implementation of the DVB-S2 Standard

Telecommunication standards are documents that contain consolidated knowledge about communication systems and implementation best practices. They are created based on long consensus processes in order to meet practical constraints. This article describes how the DVB-S2 standard is used in the electrical engineering curricula at KU Leuven within a design and implementation course called EAGLE. The goal of the course is to teach third-year Bachelor students how to apply the abstract knowledge gathered in the theoretical courses (control theory, communication theory, software, and hardware) to the design of a complex and real engineering project. Based on their progress during the academic year, we illustrate how standards can be used to teach a broad skill set and act as an accelerator to abstract system implementation complexity. We give an overview of the objectives of the EAGLE project and the relevance of the DVB-S2 standard, the design and implementation task that the students need to accomplish, and how they finally learn to master the complexity of a real communication standard, VHDL coding, and system verification and integration.

Ultra-Reliable IEEE 802.11 for UAV Video Streaming: From Network to Application

Civilian application of Unmanned Aerial Vehicles (UAVs) are becoming more and more widespread. An important question is how ultra-reliable communication to and from the drone will be organised. At the moment complex and difficult to deploy point-to-point proprietary wireless links are often used. To enable ubiquitous usage of UAVs it is necessary to have a simple, reliable and widely available data link, such as IEEE 802.11. In this work we examine if infrastructure to control UAVs could be built from IEEE 802.11 access points already deployed for other applications. Our conclusions are based on a combination of measurements and simulations. The analysis presented assumes, but is not limited to, a representative UAV mission that involved streaming video to the ground. The proposed framework then significantly improves reliability by allowing the UAV to broadcast to multiple ground receivers and solves the limited acknowledgment available to the aerial node by applying FEC at the application layer.

On the performance of 802.15.4e in the real world

To make wireless sensor networks more robust, an amendment was added to the IEEE802.15.4 standard: IEEE802.15.4e. This work studies one of the operational modes described in this amendment: Time-Slotted Channel Hopping (TSCH). This protocol is more robust due to the use of channel hopping. When channel hopping is used, every time communication fails, the nodes switch to another channel for retransmission. This way the resilience to interference increases. To be able to analyze this protocol, some environments are characterized. These serve the purpose of evaluating the operation of TSCH in real circumstances. To characterize these environments the signal strength (RSSI), 802.15.4 link quality indicator (LQI), bit error rate (BER) and packet loss (PL) are measured. A first conclusion derived from the results is the asymmetry in interference between nodes. The nodes do not see an equal amount of interference on the same channel. Secondly the characteristics of the channels vary during the day. Therefore, a communication schedule that takes these spatial and temporal variations into account is very important to optimize TSCH performance.

uLoRa: Ultra Low-Power, Low-Cost and Open Platform for the LoRa Networks

Long-Range (LoRa) is an emerging technology that is proposed to realize the Internet of Things (IoT). It enables very long range (up to 15 km) wireless communications with very low-power consumption. Many applications are being enabled by LoRa, such as water flow monitoring, animal tracking, smart parking, among many others. Although LoRa has attracted significant attentions from both industry and academia, its current cost and energy consumption are bringing inconveniences for the academia to exploit and improve LoRas performance, e.g., when massive deployment of LoRa nodes are required in order to study the scalability performance of LoRa networks. In this paper, we design and implement uLoRa, an ultra low-power, low cost, and open-source platform for LoRa networks. uLoRa is built around an ultra low-power ARM processor. Each uLoRa node only costs ≈10 euros. To reduce the energy consumption of uLoRa, we optimize its design and implementation in both the hardware and software. We evaluate the performance of uLoRa with experiments, in terms of energy consumption and communication coverage. Compared to state-of-the-art LoRa platform, uLoRa can reduce the cost by two thirds and can double the battery life of the nodes. We also demonstrate the flexibility of uLoRa through the application of moisture monitoring.