Christian Lottermann

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Due to the fast evolution of mobile devices, a high penetration of notebooks and smart-phones, and the growing demand for high rate services, e.g. mobile video and P2P services, modern radio access networks require efficient means for call admission control and radio resource management. In particular, network operators, managing co-deployed, heterogeneous(More)
The new cellular communication standard 3GPP Long Term Evolution (LTE) promises high throughputs and low latencies, thus enabling even more bandwidth-demanding and real-time critical services for end-users. This is of particular interest for vehicle manufacturers who in the future intend to offer a huge variety of cooperative driver assistance services with(More)
We present a novel bit rate model for H.264/AVC video encoding which is based on the quantization parameter, the frame rate as well as temporal and spatial activity measures. With the proposed model, it is possible to trade-off the frame rate versus the quantization parameter to achieve a target bit rate. Our model depends on video activity measures that(More)
We present a low complexity approach for the estimation of the temporal and spatial activity parameters of videos which are captured by a front-facing camera of a vehicle based on context information of the vehicle. The estimated parameters are integrated into an objective video quality metric, which can be used to determine the perceptual quality of a(More)
We study the uplink delivery of live video using adaptive HTTP streaming (AHS). In AHS, the process of simultaneously creating video levels at different rates is computationally demanding and quickly exceeds the computational capacity of mobile devices. As a remedy, we propose a network-aware video level selection approach which reduces the number of levels(More)
This paper presents the research and development activities within ”SolarMesh Energy-Efficient, Autonomous, Wide-Area Wireless Voice and Data Network”, a R&D project funded by the German Federal Ministry of Education and Research. The project, bringing together expertise from academia and industry in Germany, is specifically dedicated to develop reliable(More)
In the near term, vehicles will be connected with each other and to centralized off-board servers to provide automotive services. In this paper we analyze existing heterogeneous network selection algorithms. It is shown that the developed algorithm for network selection with additional cooperative information is well suited to improve the handover decisions(More)
The focus of the present thesis is the uplink delivery of live video using dynamic adaptive streaming over HTTP (DASH). This thesis is specifically concerned with live uplink streaming of automotive videos from the front-facing camera of a vehicle over rate-constrained heterogeneous radio access networks (RANs). DASH splits an input video in small segments(More)
Emergency situations where lives are at stake, such as natural disasters, accidents, or serious fire, require low reaction times. Especially in sparsely populated areas the distance between the nearest emergency station and its disaster location may be quite large. In order to minimize reaction times, emergency communication is to be prioritized with(More)