Multiagent and Grid Systems - Volume 6, issue 4

Authors: Kissoum, Yacine | Sahnoun, Zaidi | Barkaoui, Kamel

Article Type: Research Article

Abstract: Among all the different architectures being researched in the field of multi-agent systems, the mobile agent has shown to be one of the most challenging and most critical systems. With more applications being developed, there is a need to ensure large and complicated mobile agent systems are functioning correctly, with minimum or no errors. Moreover, the model-based testing technique has gained attention with the popularization of models in software design and development. Since the paradigm on nets within nets is well suited to express the dynamics of open mobile agents, it is retained as an abstract model from which abstract …test cases are generated. Those test cases are then concretized and addressed to the system under test. The responses of the system under test are, finally, compared to the expected results derived from the abstract test model. As a case study, we modeled a packet world example on which different colored packets are scattered. Agents that live in this virtual world have to collect those packets and bring them to their right destination. Show more

Keywords: Mobile agents, nets within nets, reference net, renew, testing

DOI: 10.3233/MGS-2010-0152

Citation: Multiagent and Grid Systems , vol. 6, no. 4, pp. 271-292, 2010

Authors: Paquet, Sébastien | Chaib-draa, Brahim | Dallaire, Patrick | Bergeron, Danny

Article Type: Research Article

Abstract: Coordinating agents in a complex environment is a hard problem, but it can become even harder when certain characteristics of the tasks, like the required number of agents, are unknown. In these settings, agents not only have to coordinate themselves on the different tasks, but they also have to learn how many agents are required for each task. To contribute to this problem, we present in this paper a selective perception reinforcement learning algorithm which enables agents to learn the required number of agents that should coordinate their efforts on a given task. Even though there are continuous variables in …the task description, agents in our algorithm are able to learn their expected reward according to the task description and the number of agents. The results, obtained in the RoboCupRescue simulation environment, show an improvement in the agents overall performance. Show more

DOI: 10.3233/MGS-2010-0153

Citation: Multiagent and Grid Systems , vol. 6, no. 4, pp. 293-314, 2010

Authors: Zhu, Hong | Wang, Fang | Wang, Shufeng

Article Type: Research Article

Abstract: Community is a common phenomenon in natural ecosystems, human societies as well as artificial multi-agent systems such as those in web and Internet based applications. In many self-organizing systems, communities are formed evolutionarily in a decentralized way through agents' autonomous behavior. This paper systematically investigates the properties of a variety of the self-organizing agent community systems by a formal qualitative approach and a quantitative experimental approach. The qualitative formal study by applying formal specification in SLABS and Scenario Calculus has proven that mature and optimal communities always form and become stable when agents behave based on the collective knowledge of …the communities, whereas community formation does not always reach maturity and optimality if agents behave solely based on individual knowledge, and the communities are not always stable even if such a formation is achieved. The quantitative experimental study by simulation has shown that the convergence time of agent communities depends on several parameters of the system in certain complicated patterns, including the number of agents, the number of community organizers, the number of knowledge categories, and the size of the knowledge in each category. Show more

Keywords: Adaptive systems, self-organization, autonomous agent, community formation, recurrence properties, reachability, stability, convergence

DOI: 10.3233/MGS-2010-0154

Citation: Multiagent and Grid Systems , vol. 6, no. 4, pp. 315-352, 2010

Authors: Bowring, Emma | Tambe, Milind | Yokoo, Makoto

Article Type: Research Article

Abstract: Distributed constraint optimization (DCOP) is a useful framework for cooperative multiagent coordination. DCOP focuses on optimizing a single team objective. However, in many domains, agents must satisfy constraints on resources consumed locally while optimizing the team goal. Yet, these resource constraints may need to be kept private. Designing DCOP algorithms for these domains requires managing complex trade-offs in completeness, scalability, privacy and efficiency. This article defines the multiply-constrained DCOP (MC-DCOP) framework and provides complete (globally optimal) and incomplete (locally optimal) algorithms for solving MC-DCOP problems. Complete algorithms find the best allocation of scarce resources while optimizing the team …objective, while incomplete algorithms are more scalable. The algorithms use four main techniques: (i) transforming constraints to maintain privacy; (ii) dynamically setting upper bounds on resource consumption; (iii) identifying the extent to which the local graph structure allows agents to compute exact bounds; and (iv) using a virtual assignment to flag problems rendered unsatisfiable by resource constraints. Proofs of correctness are presented for all algorithms. Experimental results illustrate the strengths and weaknesses of both the complete and incomplete algorithms. Show more

DOI: 10.3233/MGS-2010-0155

Citation: Multiagent and Grid Systems , vol. 6, no. 4, pp. 353-393, 2010

Authors: Tian, Jin | Tian, Tian

Article Type: Research Article

Abstract: This paper discusses three the fundamental issues of Cognitive radio: Frequency, Modulation and Power. Frequency is located in 3.1 GHz ∼ 10.6 GHz so that the system can sufficiently utilize UWB spectrum resource and communications channel. OFDM UWB transmission technology is extensively used to mitigate multi-path interference. QPSK and DCM modulation are used to map binary data on signal wave shape on subcarriers. The most important problem is emission power mask level which should not affect primary users' communications. Cognitive Radio that operates in the unused range of licensed spectrum could transmit the same level power as license wireless communications.

Keywords: CR, frequency, modulation, power

DOI: 10.3233/MGS-2010-0156

Citation: Multiagent and Grid Systems , vol. 6, no. 4, pp. 395-399, 2010