| 1. |
- Börjesson, Per Ola, et al.
(author)
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Free-riding in Group Work - Mechanisms and Countermeasures
- 2006
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In: [Host publication title missing].
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Conference paper (peer-reviewed)abstract
- Studies have shown that group work offers great possibilities for deeper learning compared to some more traditional teaching formats [1], but it can also lead to some new problems such as free-riding. Different aspects of group psychology and behaviour as well as impropriate group sizes can be used to explain why and how free-riding develops in groups. With careful course planning teachers can seriously discourage students from free-riding. Especially the grading system should be carefully chosen not to promote free-riding but to stimulate deeper learning
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| 2. |
- Gosselin, Stéphane, et al.
(author)
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Fixed and Mobile Convergence: Needs and Solutions
- 2014
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Conference paper (peer-reviewed)abstract
- The drivers of Fixed and Mobile Convergence (FMC) are discussed. A reference framework for FMC proposed by European project COMBO is then presented. Some use cases of FMC are described, showing the needs for mutualization and convergence of fixed and mobile broadband networks. Five network scenarios providing technical solutions to FMC use cases are proposed. They target an optimal and seamless quality of experience for the end user together with an optimized network infrastructure ensuring increased performance, flexibility, reduced cost and reduced energy consumption.
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| 3. |
- Hamidian, Ali, et al.
(author)
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An Enhancement to the IEEE 802.11e EDCA Providing QoS Guarantees
- 2006
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In: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 31:2-3, s. 195-212
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Journal article (peer-reviewed)abstract
- One of the challenges that must be overcome to realize the practical benefits of ad hoc networks is quality of service (QoS). However, the IEEE 802.11 standard, which undeniably is the most widespread wireless technology of choice for WLANs and ad hoc networks, does not address this issue. In order to support applications with QoS requirements, the upcoming IEEE 802.11e standard enhances the original IEEE 802.11 MAC protocol by introducing a new coordination function which has both contention-based and contention-free medium access methods. In this paper, we consider the contention-based medium access method, the EDCA, and propose an extension to it such that it can be used to provide QoS guarantees in WLANs operating in ad hoc mode. Our solution is fully distributed, uses admission control to regulate the usage of resources and gives stations with high-priority traffic streams an opportunity to reserve time for collision-free access to the medium.
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| 4. |
- Hamidian, Ali, et al.
(author)
-
Deployment and Evaluation of a Wireless Mesh Network
- 2009
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In: [Host publication title missing]. ; , s. 66-72
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Conference paper (peer-reviewed)abstract
- Wireless Mesh Networks (WMNs) have the potentialities to greatly penetrate the marketplace in the next decade. They can be considered a hybrid between wireless infrastructure and ad-hoc networks; no other network infrastructure is needed other than the mesh points, thus providing flexibility in building and expanding the network, allowing for automatic discovery of neighboring nodes, increased reliability and redundancy. In this work, we discuss how WMNs can be practically employed to support wireless multihop communications in an office-wide area. To this aim, we have deployed a real WMN testbed utilizing state-of-the-art technology and analyzed the performance of this architecture when supporting multihop heterogeneous traffic.
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| 5. |
- Hamidian, Ali, et al.
(author)
-
Distributed reservation-based QoS in Ad Hoc networks with internet access connectivity
- 2009
-
In: 2009 21ST INTERNATIONAL TELETRAFFIC CONGRESS (ITC 21). - 9781424447442 ; , s. 33-40
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Conference paper (peer-reviewed)abstract
- Real-time applications introduce new requirements on wireless networks and impose quality thresholds on parameters like delay, jitter, throughput, and packet loss in order to run smoothly. This paper addresses this issue by presenting a MAC scheme that offers real-time applications the opportunity to reserve transmission time based on their QoS requirements for contention-free medium access. Our scheme, which is called EDCA with Resource Reservation (EDCA/RR), operates in a fully distributed manner, is compatible with IEEE 802.11, and provides both prioritized and parameterized QoS. In this study, we have extended EDCA/RR to handle reservation collisions and, through extensive simulations, we show that our proposal can handle multiple reservations as well as the hidden station problem while providing QoS guarantees. We compare EDCA/RR with EDCA and our results show that, as the traffic in the network increases, EDCA/RR succeeds providing the required service to QoS-demanding applications whereas EDCA fails in this task; especially if there are hidden stations. In addition, when the medium is lossy we show that, not only does EDCA/RR give better service to real-time traffic, but also to contending non-real-time traffic.
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| 6. |
- Hamidian, Ali, et al.
(author)
-
Exploring wireless mesh networks for collaborative augmented reality environments
- 2010
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In: The International Journal of Virtual Reality. - 1081-1451. ; 9:2, s. 21-30
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Journal article (peer-reviewed)abstract
- Augmented Reality (AR) has emerged as a technology able to greatly support the interaction between people and digital information by merging virtual objects with the real environment. So far, research in this field has been mainly focused on single-user scenarios with pre-stored digital data whose visualization needs to be appropriately and promptly aligned with physical objects. Instead, latest developments of AR also involve collaborative scenarios where several participants share the same AR environment, generating and exchanging data in real-time, and communicating with each other through VoIP. To this aim, in this work we consider networking issues and possible solutions, as they represent crucial aspects when dealing with collaborative AR environments. Through the use of a real testbed, we discuss how Wireless Mesh Networks (WMNs) can be practically employed to support communications in a department-wide AR environment without the need of a fixed infrastructure. We also analyze the performance limitations of this architecture and, finally, we evaluate a possible practical QoS solution to overcome them.
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| 7. |
- Hamidian, Ali, et al.
(author)
-
Extending EDCA with Distributed Resource Reservation for QoS Guarantees
- 2008
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In: Telecommunication Systems. - : Springer Science and Business Media LLC. - 1018-4864 .- 1572-9451. ; 39:3-4, s. 187-194
-
Journal article (peer-reviewed)abstract
- In this paper we describe how the contention-based medium access mechanism of 802.11e, EDCA, can be enhanced in order to allow stations to reserve medium access for their real-time applications with QoS requirements. We present our proposed scheme, which is called EDCA with resource reservation (EDCA/RR), and describe how it can be extended in order to be used in wireless multi-hop networks. EDCA/RR operates in a completely distributed manner and manages to provide deterministic, contention-free medium access, making it an attractive scheme for wireless networks.
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| 8. |
- Hamidian, Ali
(author)
-
Internet Access and QoS in Ad Hoc Networks
- 2006
-
Licentiate thesis (other academic/artistic)abstract
- It is likely that the increased popularity of wireless local area networks (WLANs) together with the continuous technological advances in wireless communication, also increase the interest for ad hoc networks. An ad hoc network is a wireless, autonomous, infrastructure-less network composed of stations that communicate with each other directly in a peer-to-peer fashion. When discussing mobile ad hoc networks (MANETs), we often refer to an ad hoc network where the stations cooperate in forwarding packets on behalf of each other to allow communication beyond their transmission range over multi-hop paths. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed quality of service (QoS) guarantees and multi-hop Internet access. This thesis presents conceivable solutions to both of these problems. The first two papers focus on the network layer and consider the provisioning of Internet access to ad hoc networks whereas the last two papers focus on the data link layer and investigate the provisioning of QoS to ad hoc networks. The first paper studies the interconnection between a MANET and the Internet. In addition, it evaluates three approaches for gateway discovery, which can be initiated by the gateway (proactive method), by the mobile station (reactive method) or by mixing these two approaches (hybrid method). The second paper also studies Internet access for MANETs, but with focus on micro mobility, i.e. mobile stations moving from one gateway to another. In particular, it evaluates a solution that allows mobile stations to access the Internet and roam from gateway to gateway. The third paper, gives an overview of the medium access mechanisms in IEEE 802.11 and their QoS limitations. Moreover, it proposes an enhancement to the contention-free medium access mechanism of IEEE 802.11e to provide QoS guarantees in WLANs operating in ad hoc network configuration. The fourth paper continues the work from the third paper by enhancing the scheme and dealing with the problems that occur due to hidden stations. Furthermore, it discusses how to deal with the problems that occur when moving from single-hop ad hoc networks (i.e. WLANs in ad hoc network configuration) to multi-hop ad hoc networks.
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| 9. |
- Hamidian, Ali, et al.
(author)
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Performance of Internet Access Solutions in Mobile Ad Hoc Networks
- 2004
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In: [Host publication title missing]. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 3540253297 ; 3427, s. 189-201
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Conference paper (peer-reviewed)abstract
- Although an autonomous mobile ad hoc network (MANET) is useful in many scenarios, a MANET connected to the Internet is more desirable. This interconnection is achieved by using gateways, which act as bridges between a MANET and the Internet. Before a mobile node can communicate with an Internet host it needs to find a route to a gateway. Thus, a gateway discovery mechanism is required. In this paper the MANET routing protocol ad hoc on-demand distance vector (AODV) is extended to achieve the interconnection between a MANET and the Internet. Moreover, the paper investigates and compares three approaches for gateway discovery. The question of whether the configuration phase with the gateway should be initiated by the gateway, by the mobile node or by mixing these two approaches is being discussed. We have implemented and simulated these three methods and we discuss the advantages and disadvantages of the three alternatives
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| 10. |
- Hamidian, Ali
(author)
-
Providing QoS Guarantees in Ad Hoc Networks through EDCA with Resource Reservation
- 2006
-
Reports (other academic/artistic)abstract
- As the use of WLANs based on IEEE 802.11 increase, the need for QoS becomes more obvious. The upcoming IEEE 802.11e aims at providing QoS, but its contention-based medium access mechanism enhanced distributed channel access (EDCA), provides only service differentiation, i.e. soft QoS. In order to provide hard QoS, we have proposed an extension called EDCA with resource reservation (EDCA/RR), which enhances EDCA by offering also hard QoS through resource reservation. This report focuses on EDCA/RR with the aim to enhance the scheme further in single-hop scenarios but also to present an idea of how to extend the scheme to be useful also in multi-hop ad hoc networks.
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