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Research: Cross-layer Control of Wireless Ad-hoc Networks This project investigates new approaches for network control for multimedia traffic in the wireless Internet, more specifically in the wireless ad-hoc networks. The recent emergence of wireless network architectures and devices increases the need for re-design in some basic Internet mechanisms and protocols. The main problem with wireless networks is in the high level of transmission errors that occur due to the imperfection of the radio medium. The transmission errors substantially degrade the Quality of Service of Internet applications, especially in the case of the highly-structured video traffic. This project will investigate the directions for the re-design of the Internet transport protocol TCP, which needs to change to address the wireless medium. The project focuses on the design of a novel congestion control mechanism, optimised for the wireless medium, which will be investigated through extensive network simulation and analysis. Main topic of our research is transport control in wireless ad-hoc networks, especially algorithms for efficient recovery of transport-layer connections upon the event of physical-layer connection loss due to high error rate or disappearance of one or more intermediate nodes. The objective is to develop an algorithm which will differentiate between random and congestion-related loss in the specific environment of wireless ad-hoc networks and thus minimise the transport-layer disruptions. This research is sponsored by EPSRC and The Nuffield Foundation. Publications:
E Hamadani, V Rakocevic, A Cross layer Analysis of TCP Instability in Multihop Ad hoc Networks, European Wireless 2007, Paris, April 2007 E Hamadani, V Rakocevic, Evaluating and Improving TCP Performance against Contention Losses in Multihop Ad Hoc Networks,, IFIP International Conference on Mobile and Wireless Communication Networks, Marrakech, Morocco, September 2005 E Hamadani, V Rakocevic, Impact of RTS/CTS Handshake on the Performance of TCP Connections in Multihop Ad-Hoc Networks, PREP 2005 Conference, Lancaster, UK, April 2005 Teaching: At City University Opnet is used extensively for teaching computer networks courses at undergraduate and postgraduate levels. Our students benefit from a computer network laboratory in which they can practice network simulation using Opnet. Opnet is also used for undergraduate and postgraduate final year projects. Modules that have Opnet labs include EE2480 Internet Engineering and EPM775 Multiservice Communication Networks. EE2480 is a second-year undergraduate module and EPM775 is a postgraduate module at masetrs (MSc) level. The Laboratory material has been adapted from the book Network Simulation Experiments Manual, by Prof E Aboelela, Morgan Kaufmann 2003. The full laboratory assignments for EPM775 module can be found here. In the future we are planning to introduce Oopnet for the module EPM756 Wireless Communications. OPNET Technologies, Inc. is a leading provider of solutions for managing networks and applications. OPNET's best-in-class solutions address application troubleshooting, application monitoring, network monitoring, network configuration management, capacity management, and network simulation. OPNET’s solutions have been operationally proven in thousands of customer environments worldwide, including corporate and government enterprises, government and defense agencies, network service providers, and network equipment manufacturers. For more information about OPNET and its products, visit www.opnet.com. |
