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The reliability of delivering packets through multi-hop intermediate nodes is a significant issue in the mobile ad hoc networks (MANETs). The distributed mobile nodes establish connections to form the MANET, which may include selfish and misbehaving nodes. Recommendation based trust management has been proposed in the literature as a mechanism to filter out the misbehaving nodes while searching for a packet delivery route. However, building a trust model that adopts recommendations by other nodes in the network is a challenging problem due to the risk of dishonest recommendations like bad-mouthing, ballot-stuffing, and collusion. This paper investigates the problems related to attacks posed by misbehaving nodes while propagating recommendations in the existing trust models. We propose a recommendation based trust model with a defence scheme, which utilises clustering technique to dynamically filter out attacks related to dishonest recommendations between certain time based on number of interactions, compatibility of information and closeness between the nodes. The model is empirically tested under several mobile and disconnected topologies in which nodes experience changes in their neighbourhood leading to frequent route changes. The empirical analysis demonstrates robustness and accuracy of the trust model in a dynamic MANET environment. [ABSTRACT FROM AUTHOR]

The article offers an introduction to a series of articles on performance analysis and enhancements of wireless networks including "DS/CDMA throughput of a multi-hop sensor network in a Rayleigh fading underwater acoustic channel," "Effect of redundancy on the mean time to failure of wireless sensor networks," "EZRP: an enhanced zone-based routing protocol for ad-hoc networks," "Augmenting Reed–Solomon coding with retransmission for error recovery in 3G video broadcasts," "SCTP performance evaluation over heterogeneous networks," "Distributed communication model in hierarchical Infostation systems," "QoS-aware mobile service transactions in a wireless environment," "Modeling and evaluation of congestion control for different classes of network traffic," "Mobility management in hybrid ad-hoc networks and the Internet environment," and "Towards building a conflict-free mobile distributed file system."

Traffic congestion has become a crucial problem in wireless networks due to its detrimental effects on the end-to-end Quality-of-Service (QoS) of mobile users. This issue has posed various challenges to developing effective congestion control mechanisms and devising new performance evaluation tools. Various congestion control schemes have been proposed to support differentiated QoS. Among these schemes, Active Queue Management (AQM) has been recognized as an effective mechanism to manage downlink buffers in wireless networks. Most existing studies on AQM are based on the use of averaged queue length and the related performance analysis is carried out via software simulation. This paper contributes to the development of an analytical performance model for a finite capacity queuing system subject to AQM and multiple traffic classes based on the instantaneous queue length. Expressions for the aggregated and marginal performance metrics including the mean queuing length, packet loss probability, mean waiting time, system throughput, response time, and utilization are analytically derived. The validity of this new model is demonstrated by comparing the analytical results against those obtained from simulation experiments. The analytical model is then used to investigate the effects of varying thresholds on the aggregated and marginal performance metrics under different combinations of arriving rates for multiple traffic classes. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Mobile transaction technology ensures reliability, data consistency, and concurrency in mobile computing applications. Current solutions develop numerous transaction models and protocols in order to enhance the reliability and improve the performance of mobile transactions. However, they give no attention to the underlying network on which mobile transactions are carried out. This paper presents a network-centric strategy in order to improve the performance of mobile transactions. The proposed strategy is based on employing preemptive resume scheduling mechanism in mobile transactions. A cost effective analytical model for the network node with bursuty arrival traffic and prioritised scheduling mechanism has been developed using maximum entropy (ME) methodolgy. It involves rigorous analysis of a network node with finite capacity to accommodate messages, bursty arrival process to represent incoming multi-class messages, and the employment of a priority scheduling mechanism to give preferential treatment to high priority messages. This analytical solution provides closed form expressions for calculating the queuing delay per class involved in the commit processing of mobile transactions. The aim is to reduce queuing delays involved in the processing of mobile transactions at each network node. Such reduction of queuing delay significantly improves the performance of mobile transactions given the heavy network traffic and the lower network bandwidth. Several experiments have been conducted using the analytical modelling approach, which determine the impact of priority scheduling mechanism on the performance of mobile transactions. Experiments show significant performance improvements of the proposed strategy over existing approaches. [ABSTRACT FROM AUTHOR]

The article features the best six papers from the first workshop on Performance Modelling of Wired and Wireless Mobile Computing and Networks that was held in conjunction with the 11th ICPADS 2005, in Fukuoka, Japan. These papers were chosen by the scientific program committee and extended and revised before taking a peer-review. The workshop was aimed to provide an international forum for researchers and industry practitioners to introduce their research on performance modeling and evaluation studies regarding the wired and wireless networking and computing and to exchange ideas and to explore new avenues of collaborations. The papers include an investigative study by Pong and others; an experimental study by Seah and others; and the detailed investigative study by Yassein and others.