COSTA: Composite Trust-Based Asset-Task Assignment in Mobile Ad Hoc Networks

In mobile ad hoc networks (MANETs), asset-task assignment problems have been explored with vastly different approaches. Considering the unique characteristics of MANET environments, such as no centralized trusted entity, a lack of resources, and high-security vulnerabilities, resource allocation is not a trivial problem particularly for situations where a mobile team aims to successfully complete a common mission. The existing approaches have studied asset-task assignment problems by best matching a node's functionality and requirements of a given task. In this paper, we propose a task assignment protocol using the concept of multidimensional trust, namely, CompoSite Trust-based Assignment (COSTA), aiming to maximize the completion ratio of a common mission consisting of multiple tasks by balancing trust and risk in executing them. Based on the core concept of trust defined as the willingness to take the risk in performing a given task, COSTA selects qualified nodes for a given task while meeting an acceptable risk level for executing multiple tasks contributing to successful mission completion. Given a mission consisting of dynamic multiple tasks, we model each task with importance, urgency, and difficulty characteristics and use them for selecting qualified members. In addition, we model a node's risk behavior (i.e., risk-seeking, risk-neutral, and risk-averse) and investigate its impact on mission performance where a payoff is given for member selection and task execution. We formulate an optimization problem for the task assignment using integer linear programming (ILP). Our simulation results validated with ILP solutions demonstrate the existence of an optimal acceptable risk level that best balances trust and risk so as to maximize the mission completion ratio. We conduct a comprehensive comparative analysis and show that COSTA achieves a higher mission completion ratio while incurring a lower communication overhead compared with non-trust-based counterparts.