Publications

Dishonest Reporting in Queue-Based Cross-Layer Network Optimization

Authors: Dimitris Giatsios, Iordanis Koutsopoulos, Thanasis Korakis

Conference: International Workshop on Quality of Service (IWQoS) 2012, Coimbra, Portugal, June 2012

Abstract: Queue-based cross-layer optimization algorithms have recently been a subject of intensive research in wireless networks. Their purpose is to guarantee stable operation and to achieve some form of fairness among users, whenever the traffic demand exceeds network capacity. Despite the plethora of work in this field, the scenario where one or more nodes declare false queue backlog values in order to gain throughput advantage remains unexplored. In this paper we examine this type of selfish misbehavior, concentrating on a specific class of algorithms, the so-called quadratic Lyapunov-function-based algorithms (QLA). In particular, the effect of backlog misreporting on a single-hop access network with contending stations is evaluated through simulations. A simple framework for the detection of misbehaving nodes is proposed, under the assumption that the access-point is aware of the utility functions of the stations. The detection approach exploits the fact that under QLA the throughput of a node must be approximately equal to an “expected” value, derived from the reported queue backlogs.

Download paper here.

Demonstration of a Vehicle-to-Infrastructure (V2I) Communication Network featuring Heterogeneous Sensors and Delay Tolerant Network Capabilities

Authors: Donatos Stavropoulos, Giannis Kazdaridis, Thanasis Korakis, Dimitris Katsaros and Leandros Tassiulas

Conference: TridentCom 2012, Thessaloniki, Greece, June 2012

The development of applications based over vehicular networks, such as road safety, environmental information etc. require a complete testbed platform for research and evaluation. Such a platform will be provided by NITOS testbed, that will include nodes mounted on cars and fixed nodes of the testbed operating as road side units (RSU). Besides the wireless infrastructure, there will be several sensors regarding the environmental conditions and the vehicle. These will gather measurements about air conditions and GPS data such as position and speed and will be collected in a central database, where the experimenter will be able to depict them in a Google map.

Download paper: tridentcom-dtn.pdf

Enabling Sensing and Mobility

Authors: Harris Niavis, Giannis Kazdaridis, Thanasis Korakis and Leandros Tassiulas

Conference: TridentCom, Thessaloniki, Greece, June 2012

The inherent inability of simulation models to adequately express factors such as wireless signal propagation etc., can lead to incomplete evaluation of wireless protocols and applications. Thus, testing of proposed schemes under real-life settings has become the de facto validation process. More specifically, in the context of testing scenarios that include mobility, evaluation in real environments become a prerequisite. Networking testbeds have recently extended their capabilities by providing the researchers with the ability to include mobile nodes to their experiments as well. Towards this direction, we have developed a prototype mobile node in NITOS, which features a mounted camera and wireless interfaces that enable remote access and control. The proposed mobility framework is also accompanied by a graphical user interface that allows the experimenter to observe the node's behavior remotely.

Download paper: Mobile_node_demo.pdf

A Demonstration of Video over an IEEE802.11 compliant version of the Enhanced-Backpressure algorithm

Authors: Kostas Choumas, Thanasis Korakis, Iordanis Koutsopoulos and Leandros Tassiulas

Conference: TridentCom, Thessaloniki, Greece, June 2012

Abstract: This demo presents a novel routing and scheduling scheme, named Enhanced-Backpressure over WiFi (EBoW), that obviously outperforms the dominant approach of a shortest-path routing (SRCR) combined with the classic CSMA/CA scheduling policy of 802.11 networks. The new scheme combines aspects of load-balancing and shortest-path routing and enhances the CSMA/CA scheduling, maximizing the throughput performance, while keeping low end-to-end delay. We perform a comparative demonstration of video streaming over an ad-hoc 802.11 network, using EBoW and SRCR, where the latter one is a state-of-the-art shortest-path routing algorithm. The new scheme delivers a smooth and jitter-free video playback experience, while the SRCR scheme experiences noticeable jitter and rather frequent distortions. The demo clearly demonstrates the performance superiority of the new implemented scheme, as compared to the other one. The implementation of both schemes relies on the well-known Click framework.

Download paper: kohoumas_tridentcom_2012_backpressure_demo.pdf