Security and privacy issues have become critically important with the fast expansion of multiagent systems. Most network applications such as pervasive computing, grid computing, and P2P networks can be viewed as multiagent systems which are open, anonymous, and dynamic in nature. Such characteristics of multiagent systems introduce vulnerabilities and threats to providing secured communication. One feasible way to minimize the threats is to evaluate the trust and reputation of the interacting agents. Many trust/reputation models have done so, but they fail to properly evaluate trust when malicious agents start to behave in an unpredictable way. Moreover, these models are ineffective in providing quick response to a malicious agent's oscillating behavior. Another aspect of multiagent systems which is becoming critical for sustaining good service quality is the even distribution of workload among service providing agents. Most trust/reputation models have not yet addressed this issue. So, to cope with the strategically altering behavior of malicious agents and to distribute workload as evenly as possible among service providers; we present in this paper a dynamic trust computation model called "SecuredTrust.” In this paper, we first analyze the different factors related to evaluating the trust of an agent and then propose a comprehensive quantitative model for measuring such trust. We also propose a novel load-balancing algorithm based on the different factors defined in our model. Simulation results indicate that our model compared to other existing models can effectively cope with strategic behavioral change of malicious agents and at the same time efficiently distribute workload among the service providing agents under stable condition.

Peer-to-peer (P2P) networks have shown great potentials in providing a wide range of services starting from simple file sharing to distributed computing. However, P2P systems present ominous threats due to its anonymous and dynamic nature. One feasible way to minimize the threats is to evaluate the trust and reputation of the interacting peers. Trust models have often been deployed in determining the trust of peers in the network with the view to avoiding the malicious ones. Most of the existing trust models can successfully isolate malicious peers when the peers behave in a predictable way while others even fail to do so. On the other hand, these models suffer greatly when peers start to behave in a unpredictable way. Moreover, these models are ineffective in providing quick response to a peer's dynamic personality. To cope with such strategically altering behavior we present in this paper, a feedback based fast adaptive trust model which takes into account various factors in computing the trust of peers including recent trend, historical trend, sudden deviation of trust and so on. Simulations show that our model compared to other existing models can effectively identify and isolate the dynamic behavioral change of malicious peers.

Energy is one of the main obstacles to deploying wireless sensor networks (WSNs) because tiny sensor nodes cannot accommodate sufficient energy for achieving the desired level of usage. The clustering protocols of wireless sensor network attain the acme popularity among researchers because of effective usage clustering concepts based on locality and the election of a cluster head for each of them. We derive motivation from energy saving clustering schemes and propose an enhancement by saving energy and prolonging the lifetime of a sensor network significantly. The Low Energy Adaptive Clustering Hierarchy (LEACH) achieves popularity for its simplicity and applicability in WSNs. A large number of works exist that modify LEACH to strengthen the applicability of this scheme in practice, but only limited to the cluster set-up phase. In this paper, we observe a major problem that exists in all of the clustering protocols based on LEACH. That is, LEACH and its variants encounter premature death of cluster heads because data transmission time of each cycle of communication is fixed. Our proposed dynamic service policy-based scheme decreases the premature death of cluster heads and packet loss significantly.

Assuring quality of service (QoS) is an extreme challenge in cellular multimedia delivery. Without appropriate QoS, the content delivered cannot meet consumers' aesthetic demands and thus resulting in revenue loss for the service provider. In this paper, we propose a novel multi-path cellular network architecture through placement of additional base stations (BSs), i.e., antennae in the existing cellular architecture. This architecture provides a MU more than one communication links with the BSs placed in different locations. The availability of multiple channels allows the implementation of path diversity transmission protocols and improves error resilience capability for multimedia services. The problem of link failure and blind spots in the existing cellular networks are handled for voice communications as at least one base station can maintain a line of sight communication path with the MU. The distributed nature of base station placement and multiple diversified path links also reduces outage probability. We show that our proposed architecture provides better reliability and maintains cell capacity for high bandwidth multimedia services while improving signal to interference ratio compared to the existing cellular network model.

This paper presents an advanced cell visiting probability estimator for more accurately reserving resources for an estimated time interval to neighbouring cells by exploiting key mobility parameters (speed, direction and distance). The call admission control strategy used allocates bandwidth more efficiently to provide consistent Quality of Service (QoS) guarantees for multimedia traffics. Concomitantly, to ensure continuity of on-going calls with better utilization of resources, bandwidth is borrowed from existing adaptive calls without affecting the minimum QoS guarantee. Simulation results prove that the new scheme offers substantial improvements over the recent existing schemes.

This paper proposes a novel velocity support call admission scheme through defining a new directional probability function and a new technique of estimating the reservation time window. The projected velocity-dependent directional probability function, with a negative exponential distribution, is based on the assumption that both the probability of changing direction and the rate of change are higher for slow rather than fast moving mobile units. In this paper, the reservation time window is estimated more accurately through considering the estimated travel distance and average cell dwelling time rather than considering finite number of paths as proposed in many recent studies. The new scheme is compared against the existing predictive mobility support scheme using extensive real-scenario simulations. Results prove the new scheme to be very effective in achieving superior performance in terms of QoS parameters and also reduced number of overhead message transmissions.