Conducting a Large-scale Field Test of a Smartphone-based Communication Network for Emergency Response

Smartphone-based communication networks form a basis for services in emergency response scenarios, where communication infrastructure is impaired or overloaded. Still, their design and evaluation are largely based on simulations that rely on generic mobility models and weak assumptions regarding user behavior. For a realistic assessment, scenario-specific models are essential. To this end, we conducted a large-scale field test of a set of emergency services that relied solely on ad hoc communication. Over the course of one day, we gathered data from smartphones distributed to 125 participants in a scripted disaster event. In this paper, we present the scenario, measurement methodology, and a first analysis of the data. Our work provides the first trace combining user interaction, mobility, and additional sensor readings of a large-scale emergency response scenario, facilitating future research

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Decentralized Communication Services for Post-Disaster Scenarios, Resource Allocation, Prioritization, and Long-Range Communication Support

Our modern society strongly depends on critical infrastructures, such as the central power grid or information and communication technology. When these infrastructures fail during and after disasters, the affected population has no means of communication. At the same time, the increased population density of urban areas coupled with the peoples’ expectation to have permanent access to communication systems and to be informed at all times and at any place, has made disaster-management increasingly challenging. Communication is crucial during disasters as it empowers the affected population to organize and help themselves. But even if parts of the communication infrastructure are still intact, the increased communication demand for disaster relief efforts and checking on loved ones typically overloads the available infrastructure. As such, infrastructure-independent and rapidly deployable communication systems are required. Delay-tolerant ad-hoc networks can be used to build communication networks, which propagate messages via the store-carry-forward paradigm directly between neighboring communication devices. Such DTN-MANETs can be formed by the smartphones of the affected population. However, such communication networks must overcome various scenario-specific difficulties, such as limited network lifetime due to limited battery power of the devices, message propagation limitations caused by isolated network areas due to the limited range of device-to-device communication, and network resource restrictions. In this thesis, we first assess scenario-specific characteristics by conducting and evaluating a large-scale field test. Based on these results, our main contribution is the design and implementation of the decentralized disaster communication system D2CS.KOM, which extends the functionality of conventional DTN-MANETs. We enable D2CS.KOM to allocate available energy resources to the network participants in a fully decentralized way, extending the lifetime of communication devices and thus the overall network. We further propose and integrate a prioritization architecture to improve the propagation of disaster-relevant messages in the network and enable the system to adapt to continuously changing communication demands. Since the mobility of network participants determines the performance of data dissemination in DTN-MANETs, D2CS.KOM overcomes this limitation by utilizing Unmanned Aerial Vehicles (UAVs) to strategically support the dissemination of messages. We generalize disaster-specific characteristics into the Simonstrator.KOM simulation platform and conduct an extensive evaluation of our contributions. We show that our system extends the communication lifetime of individual nodes and consequently of the overall network while prioritizing disaster-relevant messages. Additionally, we demonstrate the significant support capabilities of UAVs in intermittent DTN-MANETs. In summary, we show that our contributions constitute a significant step towards ensuring communication during and after disasters by improving upon decentralized, infrastructure-independent communication systems

Decentralized Communication Services for Post-Disaster Scenarios, Resource Allocation, Prioritization, and Long-Range Communication Support

Our modern society strongly depends on critical infrastructures, such as the central power grid or information and communication technology. When these infrastructures fail during and after disasters, the affected population has no means of communication. At the same time, the increased population density of urban areas coupled with the peoples’ expectation to have permanent access to communication systems and to be informed at all times and at any place, has made disaster-management increasingly challenging. Communication is crucial during disasters as it empowers the affected population to organize and help themselves. But even if parts of the communication infrastructure are still intact, the increased communication demand for disaster relief efforts and checking on loved ones typically overloads the available infrastructure. As such, infrastructure-independent and rapidly deployable communication systems are required. Delay-tolerant ad-hoc networks can be used to build communication networks, which propagate messages via the store-carry-forward paradigm directly between neighboring communication devices. Such DTN-MANETs can be formed by the smartphones of the affected population. However, such communication networks must overcome various scenario-specific difficulties, such as limited network lifetime due to limited battery power of the devices, message propagation limitations caused by isolated network areas due to the limited range of device-to-device communication, and network resource restrictions. In this thesis, we first assess scenario-specific characteristics by conducting and evaluating a large-scale field test. Based on these results, our main contribution is the design and implementation of the decentralized disaster communication system D2CS.KOM, which extends the functionality of conventional DTN-MANETs. We enable D2CS.KOM to allocate available energy resources to the network participants in a fully decentralized way, extending the lifetime of communication devices and thus the overall network. We further propose and integrate a prioritization architecture to improve the propagation of disaster-relevant messages in the network and enable the system to adapt to continuously changing communication demands. Since the mobility of network participants determines the performance of data dissemination in DTN-MANETs, D2CS.KOM overcomes this limitation by utilizing Unmanned Aerial Vehicles (UAVs) to strategically support the dissemination of messages. We generalize disaster-specific characteristics into the Simonstrator.KOM simulation platform and conduct an extensive evaluation of our contributions. We show that our system extends the communication lifetime of individual nodes and consequently of the overall network while prioritizing disaster-relevant messages. Additionally, we demonstrate the significant support capabilities of UAVs in intermittent DTN-MANETs. In summary, we show that our contributions constitute a significant step towards ensuring communication during and after disasters by improving upon decentralized, infrastructure-independent communication systems

Multi-Strategy Simulation of Aerial Post-Disaster Ad Hoc Communication Support Systems

In case of destroyed or impaired infrastructure due to natural catastrophes, mobile devices such as smartphones can be used to create civilian ad hoc networks to provide basic means of communication. Due to the human behavior to form groups and cluster around significant locations in such situations, however, the network is often heavily intermittent, and thus, communication between clusters is impossible. Aerial Post-Disaster Ad Hoc Communication Support Systems can overcome the gaps between clusters, but the performance is highly dependent on factors like the applied strategy, the amount of UAVs, or their technical specifications. In this demonstration, we present different support strategies in an urban post-disaster scenario. Attendees can interact and select strategies and explore different strategy parameter settings, while observing the effect on the network performance and, additionally, gaining a comprehensive insight into the strategy behavior. The interaction with the demonstration underlines the vast amount of different settings and influence factors, an aerial system operator must take into account when selecting and adapting a strategy suitable for the current situation, as motivated in our accompanying main conference pape ZLD+19

On the Deadline Miss Probability of Various Routing Policies in Wireless Sensor Networks

Moving data across communication networks is often subject to deadline requirements. An example is early warning of disasters of natural origin, where sensor measurements at the disaster location must be communicated across a network within a predefined maximum delay in order for a consequent warning to be timely. In this work, we present a probabilistic model that allows for characterizing the delay experienced by sensor measurements in a wireless sensor network from source to sink depending upon the routing metric used for forwarding the data through the network. Using link delay probability distributions and the probabilities of following different paths to the sink, source-to-sink delay distributions are found for routing policies based on minimum hop-count, minimum mean delay and the Joint Latency (JLAT) protocol. An algorithm for calculating the end-to-end source to sink delay probability density function (PDF) is presented for the general case of networks that use routing tables whose input for routing decisions is the remaining time-to-deadline. The work provides a general tool for routing delay analysis, allowing for comparison of the deadline miss probability between different routing policies. An improved form of JLAT is proposed. Its deadline miss probability is found using the presented algorithm and compared to the ones determined for minimum hop-count, minimum mean delay and JLAT by means of an example