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University: University of Coimbra - FCTUC Research: Study of Routing Mechanisms for Mobile Ad-hoc Networks 1. The work produced by this research project resulted in a PhD thesis entitled: "Towards Scalable Routing for Wireless Multi-hop Networks", where an innovative approach to MANET Routing is described. After having analysed the performance of the OLSR routing protocol in different scenarios, changing parameters such as the number of nodes, number of flows and even mobility options (for instance speed and pause time), an optimized approach to MANET routing was defined and implemented. 2. Following the research topic of Deferred Routing, a link quality metric using Kernel Methods has been developed using the wireless model of the OPNET simulator. This work lead to interesting results regarding the estimation of a link's quality, published in Elsevier's Computer Networks Journal. in a paper entitled: "Link Quality Estimation in Wireless Multi-hop Networks Using Kernel Based Methods" (Paper). 3. Two additional papers that analyse the impact of hierarchical transitions in wireless multi-hop clustered networks and the scalability and routing performance of these networks were accepted in the IFIP/IEEE Network Operations and Management Symposium (NOMS 2012) and in the 3rd IEEE International Workshop on SmArt COmmunications in NEtwork Technologies - IEEE International Conference on Communications 2012, with titles "Impact Analysis of Hierarchical Transitions in Multi-hop Clustered Networks" and "Scalability and Routing Performance of Future Autonomous Networks" respectively. Paper1 Paper2 4. A paper containing the main features of the new routing proposal has been submited and accepted in the IFIP Wireless Days 2010 conference with the title "DASH, Deferred Aggregated routing for Scalable ad-Hoc networks". Paper. 5. The first obtained results were submitted and accepted in the 4th ERCIM eMobility Workshop, presenting a routing metric for the new proposed routing scheme, with the title "Increasing Reliability in Large Scale Ad-hoc Networks". Paper. 6. A paper regarding scalability performance of the OLSR protocol was submitted to the 8th International Conference on Ad Hoc Networks and Wireless, Ad Hoc Now 2009. This paper presents several simulation studies performed using the OPNET simulator and suggests possible enhancements to the OLSR protocol demonstrating the differences on routing performance for a clustered versus unclustered network of 400 nodes. Paper. Research: Analysis of Clustering Schemes for Mobile Ad-Hoc Networks 1. Clustering is one of the most important features of Mobile Ad Hoc Networks (MANETs), enabling their performance and scalability for a large number of mobile nodes. The design of clustering schemes is quite complex, due to the highly dynamic topology of such networks. Until now, a wide variety of clustering schemes has been proposed, focusing on different metrics and purposes. Followed by a study of the most significant clustering approaches, a new distinct clustering scheme was idealized, namely Novel Stable and Low-maintenance Clustering Scheme (NSLOC). This scheme attempts to simultaneously accomplish two divergent objectives, the stability of the network and a low overhead of maintenance procedures. Following this work, it was proposed an improvement of NSLOC, namely Smart and Balanced Clustering for MANETs (SALSA), aiming to further improve the its efficiency and overhead in the network. This work is part of a PhD student proposal and has been implemented using the OPNET simulator. The final objectives are to study and propose new clustering algorithm with different specific objectives in order to embrace various scenarios and situations. Currently, a new clustering algorithm is being developed, taking advantage of context information, e.g. location and user profiles, to improve even further such algorithms. The improvements of SALSA clustering scheme are being developed at the moment. New clustering schemes provide location-based sensing mechanisms to provide a more efficient cluster management. CIDNET and DiLoC algorithms are being proposed in two new distinct papers.
2. The first stage of this work resulted in an accepted paper in the "25th Symposium On Applied Computing" (sac2010) entitled "A Novel Stable and Low-maintenance Clustering Scheme". Paper. 3. The continuity of the work also resulted in a paper accepted in the "10th International Conference on Ad Hoc Networks and Wireless (ADHOC-NOW 2011)" entitled "Smart and Balanced Clustering for MANEts". Paper. 4. Another paper has been published in the "12th International Conference on Next Generation Wired/Wireless Advanced Networking (NEW2AN 2012)" entitled "Clustering for Indoor and Dense MANETs". Paper. 5. A paper proposing a new mobility model for disaster environments was accepted in the "11th International Conference on Wired/Wireless Internet Communications (WWIC 2013)" entitled "Modeling Mobility based on Human Behaviour in Disaster Areas". Paper. 6. A paper regarding a new clustering scheme, suitable for different scenario configurations using location context, was published in the Journal "Ad Hoc Networks" in July 2013, entitled "Onto Scalable Wireless Ad Hoc Networks: Adaptive and Location-aware Clustering". Paper. 7. A paper evaluating the performance of different clustering schemes in disaster scenarios with obstacles, entitled "Modelling Mobility based on Obstacle-aware Human Behaviour in Disaster Areas" was submited to a special issue of the Ad Hoc Networks journal. Research: Study the impact of IEEE 802.11n aggregation schemes 1. The IEEE 802.11 standard working group introduces new MAC frame aggregation in the IEEE 802.11n standard, aiming to improve the network throughput and efficiency. Apart from the MAC layer optimization also other important PHY layer optimization were introduced (e.g. multiple-input and multiple-output antennas (MIMO) technique). The aggregation schemes supported by IEEE 802.11n include in two distinct approaches, namely the Aggregated MAC Service Data Unit (A-MSDU) and Aggregated MAC Protocol Data Unit (A-MPDU). 2. Both A-MSDU and A-MPDU are supported in the latest OPNET Modeler's version. As a result, this work aims to study the impact of IEEE 802.11n aggregation schemes in the network performance, but also in end-user devices' related parameters, such as energy consumption. This work might encompasses new implementation concerning the energy consumption model, since there is already work performed in the area. Research: Quality of Experience Evaluation in a Multi-user VoIP scenario: WiMAX vs. LTE Networks 1. The work performed in OPNET was focused on the evaluation of WiMAX technology, allowing a comparison with testbed environment results, and the evaluation and comparison of LTE technology with the previously obtained results from the WiMAX simulation. The conducted tests simulated a multi-user VoIP scenario, where the users were sharing the same radio resources, allowing to observe several network parameters, as well as Quality of Experience (QoE) parameters. Both WiMAX and LTE tests were conducted in the 2.6GHz band, employing the TDD with a 10 MHz bandwidth channel. These tests were performed in several scenarios, namely with line of sight (free space path loss) and without line of sight (using pathloss, shadowing and multi-path models). Also, the tests were performed with and without background traffic, in order to observe the network behavior in the support of VoIP users over a congested channel. This work is part of an ongoing MSc thesis. Teaching: Network Modeling and Performance 1. The main purpose of this course is to study methodologies for modeling and evaluation of communication networks' performance, including analytic and simulation approaches. The students are given the opportunity to participate in existing research projects and encouraged to use OPNET as a simulation tool to evaluate proposals (to a certain level of extent) possibly contributing with new information for the project and developing their sense of awareness on network performance. 2. One of the works being performed by the students involves the recreation of a WiMAX test bed scenario to evaluate VoIP. The students will also try to study the performance of VoD in the same scenario and integrate the evalvid framework with OPNET. The scenario structure is as depicted bellow. 
3. Another study being developped by the students involves the comparison between the Random Waypoint and the Random Walk Mobility models analysing several parameters such as speed and direction changes, applied to real life scenarios. 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. |
