Publications

GENI WiMAX Performance: Evaluation and Comparison of Two Campus Testbeds

Authors: Fraida Fund, Cong Wangy, Thanasis Korakis, Michael Zinky and Shivendra Panwar

Conference: The Second GENI Research and Educational Experiment Workshop (GREE2013), Salt Lake City, Utah, March 2013

In the last few years, there has been an increasing awareness of the need to evaluate new mobile applications and protocols in realistic wireless settings, and platforms such as the GENI WiMAX testbeds have been developed to fulfill this need. However, wireless testbed users have experienced frustration when straightforward usage scenarios do not consistently agree with the high data rates that are advertised by the wireless technology. This work seeks to clarify the performance characteristics of two GENI WiMAX testbeds under various wireless signal conditions and network traffic patterns. By measuring the performance of several popular wireless Internet applications in two very different wireless environments, we gain a deeper understanding of how a researcher may expect the GENI WiMAX platform to behave. Our findings include some counterintuitive results, e.g. that increasing signal quality can reduce application throughput, and that applications using a single TCP flow may achieve as much as 72% less throughput than an application in an identical setting that uses multiple TCP flows. With this work, we hope to help other researchers design realistic experiments on wireless Internet systems, understand the perceived shortcomings of the GENI WiMAX platform, and interpret their experimental results in the context of the wireless setting in which the experiment was conducted.

Download paper: GENI WiMAX Performance: Evaluation and Comparison of Two Campus Testbeds

A Relaying Selection Scheme for Maximizing a Diamond Network's Throughput

Energy Efficiency Performance Evaluation ofBackPressure Driven Cooperative Relay Selection for WiMAX

Authors: Mahmoud Hadef, Apostolos Apostolaras, Alain Mourad, Jim Oreilly, Iordanis Koutsopoulos, and Leandros Tassiulas

Conference:  EMUTools – 1st Workshop on Emulation Tools, Methodology and Techniques, Cannes, French Riviera, March 5-7 2013

Abstract: This paper proposes an energy efficient buffer-level aided relay selection mechanism for mobile communication networks that is based on the back-pressure algorithm. The mechanism exploits channel state information and the availability of buffers at the relays to perform dynamic relay selection based on an analytical framework derived from a Lyapunov optimization. The latter ensures a maximization of the cell throughput while preserving the stability of backlog queues. Performance evaluation is conducted using a WiMAX System Level Simulator compliant with IEEE 802.16m standard and supports various relaying scenarios. In order to represent the system energy efficiency of the whole WiMAX system, a sophisticated and holistic energy consumption model that maps the RF output power radiated at the antenna elements of each node on the network to the total supply power of the node equipment is implemented. Two derivatives of the proposed mechanism for half duplex and full duplex systems are proposed and evaluated. Preliminary results on the Above Roof Top relaying scenario reveal a noticeable increase on both cell throughput and system energy efficiency, in terms of joules per bit, compared to conventional relaying protocols.

Download paper: Energy Efficiency Performance Evaluation ofBackPressure Driven Cooperative Relay Selection for WiMAX

Methodology and Tools for Measurements on Wireless Testbeds: The NITOS Approach

Authors: Dimitris Giatsios, Apostolos Apostolaras, Thanasis Korakis and Leandros Tassiulas

Publication Details:  Springer Lecture Notes in Computer Science (LNCS), vol. 7586 2013

Abstract: Since its establishment in 2009, the Network Implementation Testbed using Open Source drivers (NITOS) wireless testbed has been extensively used in several research projects for the experimental evaluation of protocols and algorithms. Collection of accurate measurements is of crucial importance for testbed users, allowing them to both select appropriate topologies for their experiments and assess the performance of their implementations. In this chapter, we describe measurement methodologies and tools used in the NITOS testbed in the context of its involvement in some of these projects. We provide examples demonstrating the utility of these tools for specific experiments. We also explain the challenges posed by the complex wireless medium, summarize lessons learned and outline future plans of NITOS towards an enhanced and more integrated measurement framework.

Download paper:Methodology and Tools for Measurements on Wireless Testbeds: The NITOS Approach.pdf