Jens Heuschkel

Crowdsourcing Measurements of Mobile Network Performance and Mobility During a Large Scale Event

Cellular infrastructure in urban areas is provisioned to easily cope with the usual daily demands. When facing shockingly high loads, e.g., due to large scale sport or music events, users complain about performance degradations of the mobile network. Analyzing the impact of large scale events on the mobile network infrastructure and how users perceive overload situations is essential to improve user experience. Therefore, a large data set is required to get a detailed understanding of the differences between providers, mobile devices, mobile network access technologies, and the mobility of people.

Protocol virtualization through dynamic network stacks

Network operators move away from specialized solutions and towards generic hardware and virtualized environments, allowing them to scale faster and at lower cost. It also allows them to adapt and control their network via software such as OpenFlow. Today, this control loop does not provide end-to-end adaptation and control. Mainly due to the fact that end devices, e.g., mobile phones, and the applications installed are not yet part of this control loop. To enable this, we must push virtualization to the end device. In this paper, we introduce the Dynamic Network Stack (DyNS). DyNS is based on the idea of protocol virtualization. Hidden behind a virtual network interface, DyNS creates different network protocol stacks for each application. As requirements change, DyNS can seamlessly switch between network stacks. A first proof-of-concept implementation on Linux illustrates the feasibility by switching between UDP/IP and DCCP/IP with minimal overhead and transparency for the application.

SGF: a crowdsourced large-scale event dataset

This paper presents a crowdsourced dataset of a large-scale event with more than 1000 measuring participants. The detailed dataset consists of various location data and network measurements of all national carrier collected during a four-day event. The concentrated samples for this short time period enable detailed analysis, e.g., by correlating movement patterns and experienced network conditions.

SCXML on Resource Constrained Devices

Ever since their introduction as a visual formalism by Harel et al. in 1987, state-charts played an important role to formally specify the behavior of reactive systems. However, various shortcomings in their original formalization lead to a plethora of formal semantics for their interpretation in the subsequent years. In 2005, the W3C Voice Browser Working Group started an attempt to specify SCXML as an XML dialect and corresponding semantic for state-charts and their interpretation, promoted to W3C recommendation status in 2015. In the context of multimodal interaction, SCXML derives a special relevance as the markup language proposed to express dialog models as descriptions of interaction in the multimodal dialog system specified by the W3C Multimodal Interaction Working Group. However, corresponding SCXML interpreters are oftentimes embedded in elaborate host environments, are very simplified or require significant resources when interpreted. In this chapter, we present a more compact, equivalent representation for SCXML documents as native data structures with a respective syntactical transformation and their interpretation by an implementation in ANSI C. We discuss the characteristics of the approach in terms of binary size, memory requirements, and processing speed. This will, ultimately, enable us to gain the insights to transform SCXML state-charts for embedded systems with very limited processing capabilities and even integrated circuits.

Beyond the core: Enabling software-defined control at the network edge

Software-defined networking (SDN) changes the structure of core networks from statically planned to flexible and adaptable to the network conditions. The de facto standard for the interaction between the controller and the forwarding devices (e.g., SDN switches) is the OpenFlow protocol. With increasing interest in SDN technologies, researchers found solutions to extend these paradigms to end devices, like it is done with the protocol virtualization framework VirtualStack. However, the current SDN protocols such as OpenFlow are unsuitable for controlling end devices, since they are designed for core network nodes. In this paper, we close this gap by presenting TROLL — a protocol suggestion for realizing software-defined control at the network edge. With the communication between the controller and the VirtualStack-enabled end devices being defined by TROLL, control decisions can be made jointly for both the network core and the edge, improving the flexibility, adaptability, and efficiency of the network system significantly.