ONEChat: Enabling Group Chat and Messaging in Opportunistic Networks

Opportunistic networks, which are wireless network "islands" formed when transient and highly mobile nodes meet for a short period of time, are becoming commonplace as wireless devices become more and more popular. It is thus imperative to develop communication tools and applications that work well in opportunistic networks. In particular, group chat and instant messaging applications are particularly lacking for such opportunistic networks today. In this paper, we present ONEChat, a group chat and instant messaging program that works in such opportunistic networks. ONEChat uses message multicasting on top of service discovery protocols in order to support group chat and reduce bandwidth consumption in opportunistic networks. ONEChat does not require any pre-configuration, a fixed network infrastructure or a client-server architecture in order to operate. In addition, it supports features such as group chat, private rooms, line-by-line or character-by-character messaging, file transfer, etc. We also present our quantitative analysis of ONEChat, which we believe indicates that the ONEChat architecture is an efficient group collaboration platform for opportunistic networks

A novel cooperative opportunistic routing scheme for underwater sensor networks

Increasing attention has recently been devoted to underwater sensor networks (UWSNs) because of their capabilities in the ocean monitoring and resource discovery. UWSNs are faced with different challenges, the most notable of which is perhaps how to efficiently deliver packets taking into account all of the constraints of the available acoustic communication channel. The opportunistic routing provides a reliable solution with the aid of intermediate nodes’ collaboration to relay a packet toward the destination. In this paper, we propose a new routing protocol, called opportunistic void avoidance routing (OVAR), to address the void problem and also the energy-reliability trade-off in the forwarding set selection. OVAR takes advantage of distributed beaconing, constructs the adjacency graph at each hop and selects a forwarding set that holds the best trade-off between reliability and energy efficiency. The unique features of OVAR in selecting the candidate nodes in the vicinity of each other leads to the resolution of the hidden node problem. OVAR is also able to select the forwarding set in any direction from the sender, which increases its flexibility to bypass any kind of void area with the minimum deviation from the optimal path. The results of our extensive simulation study show that OVAR outperforms other protocols in terms of the packet delivery ratio, energy consumption, end-to-end delay, hop count and traversed distance

Coopetition spectrum trading in cognitive radio networks

Spectrum trading is a promising method to improve spectrum usage efficiency. Several issues must be addressed, however, to enable spectrum trading that goes beyond conservative trading idle bands and achieve cooperation between primary and secondary users. In this paper, we argue that spectrum holes should be explicitly endogenous and negotiated by spectrum trading participants. To this end, we proposed an a Vickery auction based, coopetive framework to foster cooperation, while allowing competition for spectrum sharing. Incentive schemes and penalty for revocable spectrum are proposed to increase the spectrum access opportunities for SUs while protecting PUs spectrum value. A simultation study shows that the proposed framework outperforms conservative trading approaches, in a variety of scenarios with different levels of cooperation and bidding strategies. © 2013 IEEE

Explorative R&D collaboration: Searching for effective and efficient governance mechanisms.

Explorative R&D collaboration is an important alternative for the internal development of new technologies. The high failure rate of this type of inter-organizational collaboration, however, indicates that governing explorative R&D collaboration is not a straightforward task. Moreover, we argue that different theoretical perspectives have formulated contradictory advice of how to govern explorative R&D collaboration. Given high risks of opportunistic behavior and high coordination costs within explorative R&D collaboration, Transaction Cost Economics and Organization Theory emphasize the need for formal governance mechanisms. The innovation literature, however, stresses that formal governance mechanisms prohibit the carrying out of explorative activities which are necessary to develop new technologies. We also suggest two alternatives to address these paradoxical requirements. In specific, we argue that effective and efficient governance of explorative R&D collaboration can be achieved by 1) collecting second-hand information about potential partners, allowing for the substitution of formal governance by relational governance, and 2) combining formal and relational governance mechanisms. Based on these theoretical findings, we emphasize the importance of longitudinal, multi-level research to study the characteristics and dynamics of different governance mechanisms within inter-organizational collaboration.Behavior; Characteristics; Coordination; Cost; Costs; Dynamics; Economics; Governance; Information; Innovation; Organization theory; R&D; Requirements; Research; Risk; Studies; Substitution; Technology; Theory; Transaction cost;

MOSDEN: A Scalable Mobile Collaborative Platform for Opportunistic Sensing Applications

Mobile smartphones along with embedded sensors have become an efficient enabler for various mobile applications including opportunistic sensing. The hi-tech advances in smartphones are opening up a world of possibilities. This paper proposes a mobile collaborative platform called MOSDEN that enables and supports opportunistic sensing at run time. MOSDEN captures and shares sensor data across multiple apps, smartphones and users. MOSDEN supports the emerging trend of separating sensors from application-specific processing, storing and sharing. MOSDEN promotes reuse and re-purposing of sensor data hence reducing the efforts in developing novel opportunistic sensing applications. MOSDEN has been implemented on Android-based smartphones and tablets. Experimental evaluations validate the scalability and energy efficiency of MOSDEN and its suitability towards real world applications. The results of evaluation and lessons learned are presented and discussed in this paper.Comment: Accepted to be published in Transactions on Collaborative Computing, 2014. arXiv admin note: substantial text overlap with arXiv:1310.405

Spectrum sharing models in cognitive radio networks

Spectrum scarcity demands thinking new ways to manage the distribution of radio frequency bands so that its use is more effective. The emerging technology that can enable this paradigm shift is the cognitive radio. Different models for organizing and managing cognitive radios have emerged, all with specific strategic purposes. In this article we review the allocation spectrum patterns of cognitive radio networks and analyse which are the common basis of each model.We expose the vulnerabilities and open challenges that still threaten the adoption and exploitation of cognitive radios for open civil networks.L'escassetat de demandes d'espectre fan pensar en noves formes de gestionar la distribució de les bandes de freqüència de ràdio perquè el seu ús sigui més efectiu. La tecnologia emergent que pot permetre aquest canvi de paradigma és la ràdio cognitiva. Han sorgit diferents models d'organització i gestió de les ràdios cognitives, tots amb determinats fins estratègics. En aquest article es revisen els patrons d'assignació de l'espectre de les xarxes de ràdio cognitiva i s'analitzen quals són la base comuna de cada model. S'exposen les vulnerabilitats i els desafiaments oberts que segueixen amenaçant l'adopció i l'explotació de les ràdios cognitives per obrir les xarxes civils.La escasez de demandas de espectro hacen pensar en nuevas formas de gestionar la distribución de las bandas de frecuencia de radio para que su uso sea más efectivo. La tecnología emergente que puede permitir este cambio de paradigma es la radio cognitiva. Han surgido diferentes modelos de organización y gestión de las radios cognitivas, todos con determinados fines estratégicos. En este artículo se revisan los patrones de asignación del espectro de las redes de radio cognitiva y se analizan cuales son la base común de cada modelo. Se exponen las vulnerabilidades y los desafíos abiertos que siguen amenazando la adopción y la explotación de las radios cognitivas para abrir las redes civiles