Berthold Rathke

EvalVid – A Framework for Video Transmission and Quality Evaluation

With EvalVid we present a complete framework and tool-set for evaluation of the quality of video transmitted over a real or simulated communication network. Besides measuring QoS parameters of the underlying network, like loss rates, delays, and jitter, we support also a subjective video quality evaluation of the received video based on the frame-by-frame PSNR calculation. The tool-set has a modular construction, making it possible to exchange both the network and the codec. We present here its application for MPEG-4 as example. EvalVid is targeted for researchers who want to evaluate their network designs or setups in terms of user perceived video quality. The tool-set is publicly available [11].

A radio over fiber network architecture for road vehicle communication systems

The road vehicle communication system is an infrastructure network to be deployed along the roads for future intelligent transportation systems. Recently, in order to provide high bandwidth data traffic a radio over fiber based network at millimeter-wave bands has been proposed. In this network a control station is connected to functionally simple base stations via optical fibers. Due to millimeter-wave properties the cell size is very small; therefore, the system is characterized by small cell and high mobility. As a result, it is obvious that mobility management becomes very significant. In this paper we propose a medium access control scheme featuring fast handover and dynamic bandwidth allocation using the ability of centralized control of radio over fiber networks.

A dual distance measurement scheme for indoor IEEE 802.11 wireless local area networks

In this paper we address the problem of distance measurement in indoor IEEE 802.11 WLANs. The Received Signal Strength Indicator (RSSI) and the Signal Propagation Time (SPT) have been widely used for distance estimation in indoor WLAN deployments. However, neither approach by itself is accurate. Moreover, there is no mean by which WLAN nodes know whether the estimated distance is accurate or not. In this work we propose a multi-measurement approach. Specifically, we combine an RSSI and a propagation time - based schemes and utilize both results for mutual cross-validation to improve the estimation accuracy and reduce the number of false decisions based on errored estimations. The performance of our combined mechanism has been evaluated through real experiments.

Collaborative setting of RTS/CTS in multi-rate multi-BSS IEEE 802.11 wireless LANs

Despite the fact that the Request-To-Send/Clear-To-Send (RTS/CTS) protocol significantly reduces collisions and retransmissions due to the hidden node problem, it is well known that it adds considerable overhead specially with small payload packets. The IEEE 802.11 standard defined a manageable parameter, RTS threshold, above which a data packet should be preceded with RTS/CTS handshake. In this paper, we propose new dynamic criteria for setting the RTS/CTS mechanism. We believe that RTS/CTS settings should consider the characteristics of userspsila traffic, data rates, activities and locations. While most of the algorithms proposed for controlling RTS/CTS have been investigated under single transmission rate for all users, we evaluate our criteria in a multi-rate scenario. We validate our ideas using both synthetic and real traces as well as real experiments.

TCP over multiple paths revisited: Towards transparent proxy solutions

The idea of using multiple paths to transport TCP traffic seems very attractive due to the potential benefits it may offer. Despite a solid theoretical background and quite substantial implementation attempts, none of the provided proposals was successful enough to fully establish its mark. Therefore, this paper presents and develops a novel approach to carry TCP traffic over multiple paths. The main features of the proposed architecture include: (1) end-to-end transparency, (2) autonomy of the operation (protocol stack transparency), and (3) interoperability with different operating systems (OSs). To demonstrate the potential of the presented architecture, experimental results are provided in one of possible application scenarios, a high capacity local mesh backbone network with bottleneck gateway links.

Snuffle: Integrated Measurement and Analysis Tool for Internet and Its Use in Wireless In-House Environment

In this paper we describe Snuffle, a new measurement tool for capturing, displaying and analyzing the operation of the Internet protocol stack within end-systems. Snuffle is a set of modules operating in a distributed fashion and supporting an on-line analysis of network and protocol performance. This kind of tool is especially suited for wireless networks.