Open Access

Rural areas often lack affordable broadband Internet connectivity, mainly due to the CAPEX and especially OPEX of traditional operator equipment [HEKN11]. This digital divide limits the access to knowledge, health care and other services for billions of people. Different approaches to close this gap were discussed in the last decade [SPNB08]. In most rural areas satellite bandwidth is expensive and cellular networks (3G,4G) as well as WiMAX suffer from the usually low population density making it hard to amortize the costs of a base station [SPNB08].

This work describes extensions to the well-known Distributed Coordination Function (DCF) model to account for IEEE802.11n point-to-point links. The developed extensions cover adaptions to the throughput and delay estimation for this type of link as well peculiarities of hardware and implementations within the Linux Kernel. Instead of using simulations, the approach was extensively verified on real-world deployments at various link distances. Additionally, trials were conducted to optimize the CWmin values and the number of retries to maximize throughput and minimize delay. The results of this work can be used to estimate the properties of long-distance 802.11 links beforehand, allowing the network to be planned more accurately.

Anhand von Funkfeldmessungen in mehreren ausgewählten Orten im Hochsauerlandkreis wird die Frage diskutiert, welchen Beitrag der Aufbau eines LTE-Netzes zur Breitbandversorgung von bisher unterversorgten Gebieten im ländlichen Raum liefern kann - und dies unter Verwendung bestehender GSM-Basisstationsstandorte und dem Frequenzbereich der Digitalen Dividende. Für verschiedene Szenarien werden Empfangspegelstatistiken mit geforderten Empfängerempfindlichkeiten verglichen, Statistiken zur zu erwartenden Datenraten abgeleitet und Netzkapazitäten abgeschätzt. Dabei zeigt sich, dass i. A. sowohl der Empfangspegel als auch die Netzkapazität ausreichen, um mittels LTE eine genügende Zahl von Anschlüssen mit einer Downlink-Datenrate von mindestens 1 Mbit/s in den untersuchten Ortschaften bereit zu stellen. Hohe Versorgungsgrade mit Datenraten von 50 Mbit/s sind jedoch nicht zu erwarten. Durch eine Außeninstallation der Endgeräteantennen lassen sich auch bei 2600 MHz nahezu optimale Empfangsbedingungen erzielen. Insofern scheint ein Mischbetrieb mit Frequenzen im 800- und im 2600-MHz-Bereich geeignet, die Netzkapazität auch im ländlichen Raum zu erhöhen.

WiFi-based Long Distance (WiLD) networks have emerged as a promising alternative approach for Internet in rural areas. However, the MAC layer, which is based on the IEEE802.11 standard, comprises contiguous stations in a cell and is spatially restricted to a few hundred meters at most. In this work, we summarize efforts by different researchers to use IEEE802.11 over long-distances. In addition, we introduce WiLDToken, our solution to optimizing the throughput and fairness and reducing the delay on WiLD links. Compared to previous alternative MAC layers protocols for WiLD, our focus is on optimizing a single link in a multi-radio multi-channel mesh. We implement our protocol in the ns-3 network simulator and show thatWiLDToken is superior to an adapted version of the Distributed Coordination Function (DCF) for different link distances. We find that the throughput on a single link is close to the physical data-rate without a major decrease over longer distances.

SDN and WMN evolved to be sophisticated technologies used in a variety of applications. However, a combined approach called wmSDN has not been widely addressed in the research community. Our idea in this field consists of WiFi-based point-to-point links managed by the OpenFlow protocol. We investigate two different issues regarding this idea. First, which WiFi operational mode is suitable in an OpenFlow managed broadcast domain? Second, does the performance decrease compared with other routing or switching principles? Therefore, we set up a real-world testbed and a suitable simulation environment. Unlike previous work, we show that it is possible to use WiFi links without conducting MAC address rewriting at each hop by utilizing the 4-address-mode.

This paper describes the security mechanisms of several wireless building automation technologies, namely ZigBee, EnOcean, ZWave, KNX, FS20, and Home-Matic. It is shown that none of the technologies provides the necessary measure ofsecurity that should be expected in building automation systems. One of the conclusions drawn is that software embedded in systems that are build for a lifetime of twenty years or more needs to be updatable.

Two key questions motivated the work in this paper: What is the impact of different usage schemes for multiple channels in a dual-radio Wireless Mesh Network (WMN), and what is the impact of some popular WMN routing protocols on its performance. These two questions were evaluated in a small and simple real-world scenario. A major concern was reproducibility of the results. We show that it is beneficial to use both radios on different frequencies in a fully meshed environment with four routers. The routing protocols Babel, B.A.T.M.A.N. V, BMX7 and OLSRv2 recognize a saturated channel and prefer the other one. We show that in our scenario all of the protocols perform equally well since the protocol overhead is comparably low not influencing the overall performance of the network.

Online advertising represents a main instrument for publishers to fund content on the World Wide Web. Unfortunately, a significant number of online advertisements often accommodates potentially malicious content, such as cryptojacking hidden in web banners - even on reputable websites. In order to protect Internet users from such online threats, the thorough detection of ad-malware campaigns plays a crucial role for a safe Web. Today, common Internet services like VirusTotal can label suspicious content based on feedback from contributors and from the entire Web community. However, it is open to which extent ad-malware is actually taken into account and whether the results of these services are consistent. In this pre-study, we evaluate who defines ad-malware on the Internet. In a first step, we crawl a vast set of websites and fetch all HTTP requests (particularly to online advertisements) within these websites. Then we query these requests both against popular filtered DNS providers and VirusTotal. The idea is to validate, how much content is labeled as a potential threat. The results show that up to 0.47% of the domains found during crawling are labeled as suspicious by DNS providers and up to 8.8% by VirusTotal. Moreover, only about 0.7% to 3.2% of these domains are categorized as ad-malware. The overall responses from the used Internet services paint a divergent picture: All considered services have different understandings to the definition of suspicious content. Thus, we outline potential research efforts to the automated detection of ad-malware. We further bring up the open question of a common definition of ad-malware to the Web community.

This paper introduces a novel Wireshark dissector designed to facilitate the analysis of Service-Based Interface (SBI) communication in 5G Core Networks. Our approach involves parsing the OpenAPI schemes provided by the 5G specification to automatically generate the dissector code. Our tool enables the validation of 5G Core Network traces to ensure compliance with the specifications. Through testing against three open-source 5G Core Network projects, we identified several issues where messages deviate from specification standards, highlighting the significance of our implementation in ensuring protocol conformity and network reliability.

More and more low-power wide-area networks (LPWANs) are being deployed and planning the gateway locations plays a significant role for the network range, performance and profitability. We choose LoRa as one LPWAN technology and evaluated the accuracy of the Received Signal Strength Indication (RSSI) of different chipsets in a laboratory environment. The results show the chipsets report significantly different RSSI. To estimate the range of a LPWAN beforehand, path loss models have been proposed. Compared to previous work, we evaluated the Longley-Rice Irregular Terrain Model which makes use of real-world elevation data to predict the path loss. To verify the results of that prediction, an extensive measurements campaign in a semi-urban area in Germany has been conducted. The results show that terrain data can increase the prediction accuracy.

Verschiedene intelligente Heimautomatisierungsgeräte wie Lampen, Schlösser und Thermostate verbreiten sich rasant im privaten Umfeld. Ein typisches Kommunikationsprotokoll für diese Geräteklasse ist Bluetooth Low Energy (BLE). In dieser Arbeit wird eine strukturierte Sicherheitsanalyse für BLE vorgestellt. Die beschriebene Vorgehensweise kategorisiert bekannte Angriffsvektoren und beschreibt einen möglichen Aufbau für eine Analyse. Im Zuge dieser Arbeit wurden einige sicherheitsrelevante Probleme aufgedeckt, die es Angreifern ermöglichen die Geräte vollständig zu übernehmen. Es zeigte sich, dass im Standard vorgesehene Sicherheitsfunktionen wie Verschlüsselung und Integritätsprüfungen häufig gar nicht oder fehlerhaft implementiert sind.

More and more devices will be connected to the internet [3]. Many devicesare part of the so-called Internet of Things (IoT) which contains many low-powerdevices often powered by a battery. These devices mainly communicate with the manufacturers back-end and deliver personal data and secrets like passwords.

Urban LoRa networks promise to provide a cost-efficient and scalable communication backbone for smart cities. One core challenge in rolling out and operating these networks is radio network planning, i.e., precise predictions about possible new locations and their impact on network coverage. Path loss models aid in this task, but evaluating and comparing different models requires a sufficiently large set of high-quality received packet power samples. In this paper, we report on a corresponding large-scale measurement study covering an urban area of 200km2 over a period of 230 days using sensors deployed on garbage trucks, resulting in more than 112 thousand high-quality samples for received packet power. Using this data, we compare eleven previously proposed path loss models and additionally provide new coefficients for the Log-distance model. Our results reveal that the Log-distance model and other well-known empirical models such as Okumura or Winner+ provide reasonable estimations in an urban environment, and terrain based models such as ITM or ITWOM have no advantages. In addition, we derive estimations for the needed sample size in similar measurement campaigns. To stimulate further research in this direction, we make all our data publicly available.

This work provides a short but technical introduction to the main building blocks of a blockchain. It argues that a blockchain is not a revolutionary technology but rather a clever combination of three fields: cryptography, decentralization and game theory. In addition, it summaries the differences between a public, private and federate blockchain model and the two prominent consensus mechanism Proof-of-Work (POW) and Proof-of-Stake (POS).