| 1. |
- Cavalcanti de Castro, Marcel, et al.
(författare)
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Peer-to-Peer Overlay in Mobile Ad-hoc Networks
- 2009
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Ingår i: Handbook of Peer-to-Peer Networking. - New York : Springer. - 9780387097503
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Wireless multi-hop networks such as mobile ad-hoc (MANET) or wirelessmesh networks (WMN) have attracted big research efforts during the last yearsas they have huge potential in several areas such as military communications, fastinfrastructure replacement during emergency operations, extension of hotspots oras an alternative communication system. Due to various reasons, such as characteristicsof wireless links, multi-hop forwarding operation, and mobility of nodes,performance of traditional peer-to-peer applications is rather low in such networks.In this book chapter, we provide a comprehensive and in-depth survey on recent researchon various approaches to provide peer-to-peer services in wireless multi-hopnetworks. The causes and problems for low performance of traditional approachesare discussed. Various representative alternative approaches to couple interactionsbetween the peer-to-peer overlay and the network layer are examined and compared.Some open questions are discussed to stimulate further research in this area
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| 2. |
- Bayer, Nico, et al.
(författare)
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VoIP service performance optimization in pre-IEEE 802.11s Wireless Mesh Networks
- 2008
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Ingår i: Proceedings of the IEEE International Conference on Circuits andSystems for Communications (ICCSC) 2008. - : IEEE conference proceedings. - 9781424417070 ; , s. 75-79
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Konferensbidrag (refereegranskat)abstract
- 802.11-based wireless mesh networks are seen as a means for providing last mile connections to next generation networks. Due to the low deployment cost and the mature technology used, they are scalable, easy to implement and robust. With an increasing coverage of wireless networks, VoIP becomes a cheaper alternative for traditional and cellular telephony. In this paper, we carry out a feasibility study of VoIP in a dual radio mesh environment. Heading towards 802.11s, we present the design of a mesh testbed and methodology for performing the measurements. Additionally, we address the problem that small voice packets introduce a high overhead leading to a low voice capacity of 802.11 based mesh networks. In order to alleviate this problem and increase the voice capacity, a novel packet aggregation mechanism is presented and evaluated using the ns-2 simulator.
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| 3. |
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| 4. |
- Brunström, Anna, et al.
(författare)
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NEWCOM++ DR11.3: Final report on the activities and results of WPR11
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document is the last deliverable of WPR.11 and presents an overview of the final activities carried out within the NEWCOM++ Workpackage WPR.11 during the last 18 months. We provide a description of the most consolidated Joint Research Activities (JRAs) and the main results so far obtained. We also address some considerations on the future activities which are expected to continue at the end of NEWCOM++
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| 5. |
- Cavalcanti de Castro, Marcel, 1978-, et al.
(författare)
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BestPeer : A Load-aware Multi-path Peer Selection for Wireless Mesh Networks
- 2012
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Ingår i: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM). - : IEEE Press. - 9781467312387
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Konferensbidrag (refereegranskat)abstract
- In this paper we study the interactions between peer selection, routing and channel assignment while deploying Peer-to-Peer (P2P) systems over multi-channel multi-radio Wireless Mesh Networks (WMNs). In particular we propose Bestpeer, a novel peer selection algorithm for WMNs which incorporates a cross-layer path load metric and integrates multi-path load balancing capability throughout the P2P download process in order to achieve faster resource disseminations. By comparing Bestpeer with BitTorrent through extensive simulations, we show that we can reduce the time to disseminate a resource by up to 40 %. The key mechanism used by Bestpeer to increase performance in WMNs is the effective exploitation of cross-layer information made available from the routing and channel assignment during the peer selection process in order to balance the load along high capacity paths
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| 6. |
- Cavalcanti de Castro, Marcel, et al.
(författare)
-
Capacity Increase for Voice over IP Traffic through Packet Aggregation in Wireless Multihop Mesh Networks
- 2007
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Konferensbidrag (refereegranskat)abstract
- Recently, Voice over IP (VoIP) has become an important service for the future internet. However, for ubiquitous wireless VoIP services, greater coverage will be necessary as promised by the advent of e.g. 802.11 WLAN based wireless meshed networks. Unfortunately, the transmission of small (voice) packets imposes high overhead which leads to low capacity for VoIP over 802.11 based multihop meshed networks. In this work, we present a novel packet aggregation mechanism that significantly enhances capacity of VoIP in wireless meshed networks while still maintaining satisfactory voice quality. Extensive experiments using network simulation ns-2 confirm that our packet aggregation algorithm can lead to a significantly increase in the number of supported concurrent VoIP flows over a variety of different hop numbers while reducing the MAC layer contention
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| 7. |
- Cavalcanti de Castro, Marcel, et al.
(författare)
-
Challenges of SIP in Internet Connected MANETs
- 2007
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Konferensbidrag (refereegranskat)abstract
- Mobile Ad Hoc networking has been considered as one of the most important technologies to support future Ubiquitous and Pervasive Computing Scenarios and internet connected MANETs will be an integral part of future wireless networks. For providing multimedia services and Voice over IP in such environment, support for Session Initiation Protocol (SIP) is essential. A MANET is a decentralized collection of autonomous nodes but a SIP infrastructure requires centralized proxies and registrar servers. In this paper, we study the implications of using standard SIP architecture in internet connected MANETs. We analyze performance limitations of SIP service scalability when centralized proxies/registrars located in the access network are used by MANET nodes. We also present and compare an alternative approach to provide SIP services in internet connected MANETs in order to minimize the impact of such performance limitations
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| 8. |
- Cavalcanti de Castro, Marcel, 1978-
(författare)
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Enabling Multimedia Services over Wireless Multi-Hop Networks
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the constant development of wireless technologies, the usageof wireless devices tends to increase even more in the future.Wireless multi-hop networks (WMNs) have emerged as a keytechnology to numerous potential scenarios, ranging from disasterrecovery to wireless broadband internet access. The distributedarchitecture of WMNs enables nodes to cooperatively relay othernode's packets. Because of their advantages over other wirelessnetworks, WMNs are undergoing rapid progress and inspiringnumerous applications. However, many technical issues still existin this field. In this thesis we investigate how Voice over IP(VoIP) and peer-to-peer (P2P) application are influenced bywireless multi-hop network characteristics and how to optimizethem in order to provide scalable communication.We first consider the deployment of VoIP service in wirelessmulti-hop networks, by using the Session Initiation Protocol (SIP)architecture. Our investigation shows that the centralized SIParchitecture imposes several challenges when deployed in thedecentralized wireless multi-hop environment. We find that VoIPquality metrics are severely degraded as the traffic and number ofmultiple hops to the gateway increase. In the context ofscalability, we further propose four alternative approaches whichavoid current limitations.In the second part of this thesis we tackle the network capacityproblem while providing scalable VoIP service over wirelessmulti-hop networks. The performance evaluation shows the influenceof intra and inter-flow interference in channel utilization, whichdirect impacts the VoIP capacity. In order to avoid the small VoIPpacket overhead, we propose a new adaptive hop-by-hop packetaggregation scheme based on wireless link characteristics. Ourperformance evaluation shows that the proposed scheme can increasethe VoIP capacity by a two-fold gain.The study of peer-to-peer applicability over wireless multi-hopnetworks is another important contribution. A resource lookupapplication is realized through structured P2P overlay. We showthat due to several reasons, such as characteristics of wirelesslinks, multi-hop forwarding operation, and structured P2Pmanagement traffic aggressiveness the performance of traditionalP2P applications is rather low in wireless multi-hop environments.Therefore, we suggested that a trade-off between the P2P lookupefficiency and the P2P management traffic overhead can be achievedwhile maintaining the overlay network consistency in wirelessmulti-hop networks.
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| 9. |
- Cavalcanti de Castro, Marcel, 1978-
(författare)
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Enhancing P2P Systems over Wireless Mesh Networks
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to its ability to deliver scalable and fault-tolerant solutions, applications based on the peer-to-peer (P2P) paradigm are used by millions of users on the internet. Recently, wireless mesh networks (WMNs) have attracted a lot of interest from both academia and industry, because of their potential to provide flexible and alternative broadband wireless internet connectivity. However, due to various reasons such as unstable wireless link characteristics and multi-hop forwarding operation, the performance of current P2P systems is rather low in WMNs. This dissertation studies the technological challenges involved while deploying P2P systems over WMNs. We study the benefits of location-awareness and resource replication to the P2P overlay while targeting efficient resource lookup in WMNs. We further propose a cross-layer information exchange between the P2P overlay and the WMN in order to reduce resource lookup delay by augmenting the overlay routing table with physical neighborhood and resource lookup history information. Aiming to achieve throughput maximization and fairness in P2P systems, we model the peer selection problem as a mathematical optimization problem by using a set of mixed integer linear equations. A study of the model reveals the relationship between peer selection, resource replication and channel assignment on the performance of P2P systems over WMNs. We extend the model by formulating the P2P download problem as chunk scheduling problem. As a novelty, we introduce constraints to model the capacity limitations of the network due to the given routing and channel assignment strategy. Based on the analysis of the model, we propose a new peer selection algorithm which incorporates network load information and multi-path routing capability. By conducting testbed experiments, we evaluate the achievable throughput in multi-channel multi-radio WMNs. We show that the adjacent channel interference (ACI) problem in multi-radio systems can be mitigated, making better use of the available spectrum. Important lessons learned are also outlined in order to design practical channel and channel bandwidth assignment algorithms in multi-channel multi-radio WMNs.
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| 10. |
- Cavalcanti de Castro, Marcel, et al.
(författare)
-
Measuring the Impact of ACI in Cognitive Multi-Radio Mesh Networks
- 2010
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Konferensbidrag (refereegranskat)abstract
- In this paper we address the impact of ACI on dynamic spectrum allocation in multi-radio systems. In particular, we present the benefits of dynamic spectrum allocation by adapting channel bandwidth and distance in order to mitigate ACI in multi-radio mesh networks. Based on our measurement campaign in an indoor mesh testbed, which we extended in order to use adaptive channel width, we evaluate the performance in terms of network throughput. We show that by using channel bandwidth adaptation and antenna separation, the impact of ACI can be significantly reduced. The performed experiments give important insights into ACI in multi-radio cognitive systems which help to develop e.g. better channel assignment algorithms or capacity estimation methods
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