Publications

An Integrated Chassis Manager Card Platform featuring multiple sensor modules

Authors: Giannis Kazdaridis, Stratos Keranidis, Harris Niavis, Thanasis Korakis, Iordanis Koutsopoulos and Leandros Tassiulas

Conference: TridentCom 2012, Thessaloniki, Greece, June 2012

Abstract: The gradually growing demand for experimentation of protocols designed for wireless networks in real environments has resulted in the development of experimental network facilities (testbeds). Most currently deployed testbeds have been designed so as to o er services to experimenters that lie within the testbed's premises, thus limiting the accessibility to external users. The requirement for multi-user access of network resources has led several large-scale testbeds to provide remote access services to certi ed experimenters. However, management and maintenance of large-scale remotely accessible testbeds is a rather challenging task that requires proper hardware, as well as software custom-built tools. In order to provide for remote switching of testbed nodes, NITOS has developed a new chassis manager (CM) card and also a custom framework that allows for monitoring and controlling of the nodes' operational mode. In addition, NITOS CM card provides for gathering of various types of sensor measurements, through the attached temperature, humidity and light intensity sensor modules. Another innovative characteristic of the proposed card is that it provides the experimenters with the ability to monitor the energy consumption of each testbed node, which is rather important for experimentation with power optimization schemes. In this demo, we will present the various functionalities of the NITOS CM card and the developed control framework that accompanies it.

Download paper: An Integrated Chassis Manager Card Platform featuring multiple sensor modules.pdf

A Framework and Experimental Study for Discrimination of Collision and Channel Errors in Wireless LANs

Authors: Georgios Kyriakou, Donatos Stavropoulos, Iordanis Koutsopoulos, Thanasis Korakis and Leandros Tassiulas

Conference: TridentCom, Shanghai, China, April 2011

A fundamental unresolved problem in wireless networks is that of distinguishing packet errors that are caused by deteriorated link conditions and noise, from errors that occur due to packet collisions. In this paper, we develop advanced algorithms based on Cyclic Redundancy Check (CRC) [10] that solve this problem. Speci cally, our innovation is that we form multiple CRCs, each of which is responsible for a di er- ent segment in a packet. The CRCs are appended after each segment. In this way, we can essentially visualize the pattern of errors across the packet. If the number of successive erroneous segments exceeds a thresh- old, we decide in favor of a collision. We integrate our approach with SampleRate. Our approach is implemented in MadWiFi [7] and is val- idated through realistic test-bed experiments. Our technique is shown to signi cantly outperform current error identi cation techniques, while having low complexity, and it constitutes an approach that can be readily incorporated in existing wireless protocols.

Download link: Tridentcom-CRC.pdf

An Experimental Framework for Channel Sensing through USRP/GNU Radios

An Experimental Framework for Channel Sensing.pdf

Authors: Virgilios Passas, Stratos Keranidis, Thanasis Korakis, Iordanis Koutsopoulos and Leandros Tassiulas

Conference: TridentCom 2012, Thessaloniki, Greece, June 2012

Abstract: In the last decade testbeds have been set-up to evaluate network protocols and algorithms under realistic settings. In order to draw solid conclusions about the corresponding experimental results, it is important for the experimenter to have a de- tailed view of the existing channel conditions. Moreover, especially in the context of non-RF-isolated wireless testbeds, where external interference severely impacts the re- sulting performance, the requirement of experimenters for accurate channel monitoring becomes a prerequisite. Toward, this direction, various channel sensing platforms have been introduced, where each one o ers di erent operational characteristics. In this demo, we propose the NITOS Channel Sensing framework, which is based on software-de ned radio (SDR) devices that feature highly exible wireless transceivers and are able to provide highly accurate channel sensing measurements. Through this framework, online measurement gathering is automated and further simpli ed using speci cally developed scripts, so that it becomes a transparent process for the experimenter. The proposed framework is also accompanied by a web user interface that allows the user to get a graphical representation of the gathered measurements.

Download paper: An Experimental Framework for Channel Sensing.pdf

Implementation & E2E Throughput Evaluation of an 802.11 compliant version of Enhanced-Backpressure

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

Conference: TridentCom,Thessaloniki, Greece, June 2012

Abstract: Extensive work has been done in wireless multihop routing with several ideas based on shortest path or load balancing routing algorithms, that aim at minimizing end-to-end delay or maximizing throughput respectively. Backpressure is a throughput-optimal scheme for multihop routing and scheduling, while Enhanced-Backpressure is an incremental work that reduces end-to-end delay without sacri cing throughput optimality. However, the implementation of both theoretical schemes is not straightforward in the presence of 802.11 MAC, mainly because of their requirement for centralized scheduling decisions that is not aligned with the aspects of CSMA/CA. This paper proposes a novel scheme, named Enhanced-Backpressure over WiFi (EBoW), which is compatible with the decentralized operation of WiFi networks and e ciently utilizes the bene ts of Enhanced-Backpressure design, combining throughput optimality with low end-to-end delay. EBoW router is implemented relying on Click framework for routing con guration. The performance of EBoW is evaluated both on a medium-scale outdoors wireless testbed as well as through experimentations in NS-3 simulator tool. The protocol has been compared against other state of the art routing protocols and we argue that EBoW is much more throughput e cient than the others, while succeeding similar end-to-end delay.

Download paper: kohoumas_tridentcom_2012_backpressure.pdf