Since the inception of service-oriented computing paradigm, we have witnessed a plethora of services deployed across a broad spectrum of applications, ranging from conventional RPC-based services to SOAP-based Web services. Likewise, the proliferation of mobile devices has enabled the remote "on the move" access of these services from anywhere at any time. Secure access to these services is challenging especially in a mobile computing environment with heterogeneous modalities. Conventional static access control mechanisms are not able to accommodate complex secure access requirements. In this paper, we propose an adaptive secure access mechanism to address this problem. Our mechanism consists of two components: an adaptive access control module and an adaptive function invocation module. It not only adapts access control policies to diverse requirements, but also introduces function invocation adaptation during access, which is the missing part of existing access control models. We have successfully applied the proposed adaptive secure access mechanism to a computer-assisted surgery application called UbiCAS. Performance evaluation shows that with limited overhead, our technique enforces secure access to the services provided by the UbiCAS system in a flexible way.

In this paper we propose a novel energy-aware QoS model, e-QoS, for application sessions that might across multiple protocol domains. The model provides the QoS guarantee by dynamically selecting and adapting application protocols. To the best of our knowledge, our model is the first attempt to address QoS adaptation at the application session level by proposing a new QoS metric called session lifetime. To show the effectiveness of the proposed scheme, we have implemented a case study: instant messenger applications between two PocketPCs. Experiment shows that the session lifetime has been successfully extended to the value negotiated by two PocketPCs with very diverse battery capacities.

We have witnessed the increasing demand for pervasive Internet access from public area wireless networks (PAWNs). The diverse service requirements from end users necessitate an efficient service differentiation mechanism, which should satisfy two goals: end-user fairness and maximizing the utilization of wireless link. However, we found that the existing best-effort based service model is not enough to satisfy either goal. We have proposed an application-aware service differentiation mechanism which takes both application semantics and user requirements into consideration. The results show that our proposed method outperforms two other bandwidth allocation approaches, best effort and static allocation, in terms of both client fairness and wireless link bandwidth utilization, especially in heavy load environments.