Dimitris Vassis

The IEEE 802.11g standard for high data rate WLANs

Continuous WLAN public acceptance comes with increasing demand for provision of higher data rates. Building on this context, the IEEE published the IEEE 802.11g standard for providing data rates of up to 54 Mb/s at the 2.4 GHz band. This article presents the new features of IEEE 802.11g and, using an open source C++-based simulation tool, evaluates both the performance and effectiveness of these features compared to the older IEEE 802.11 standard versions.

Delay Performance Analysis and Evaluation of IEEE 802.11e EDCA in Finite Load Conditions

The paper presents an analytical model for the performance evaluation of IEEE 802.11e EDCA scheme under finite load conditions on the basis of various instances of delay metric (i.e., media access delay, queuing delay and total delay). The simulation results show that the analytical estimated instances of the delay metric are almost accurate. The paper exhibits that concerning the delay of serving classes, EDCA compared to the conventional DCF, favors high priority classes against low priority ones, while almost does not affect the behavior of medium ones.

Providing advanced remote medical treatment services through pervasive environments

Advances on sensor technology, wireless environments and data mining introduce new possibilities in the healthcare sector, realizing the anytime-anywhere access to medical information. Towards this direction, integration of packet-switched networks and sensor devices can be effective in deploying assistive environments, such as home monitoring for elderly or patients. In this paper we describe a policy-based architecture that utilizes wireless sensor devices, advanced network topologies and software agents to enable remote monitoring of patients and elderly people; through the aforementioned technologies we achieve continuous monitoring of a patient’s condition and we can proceed when necessary with proper actions. We also present a software framework and network architecture that realizes the provision of remote medical services, in compliance with the imposed security and privacy requirements. A proof of concept prototype is also deployed, along with an evaluation of the overall architecture’s performance.

Performance evaluation of single and multi-channel actor to actor communication for wireless sensor actor networks

Abstract The paper discusses two distributed actor to actor communication schemes (a single channel one and a multi-channel one) for wireless sensor actor networks (WSANs). The performance of these two schemes is evaluated through analysis and simulation. The simulation results show that the whole analysis is fairly accurate. It is further proven that the multi-channel scheme has better performance than the single channel one. The key feature of the multi-channel scheme is the separation of the single hop from the multi-hop traffic.

Performance analysis of IEEE 802.11 ad hoc networks in the presence of exposed terminals

The paper evaluates the performance effects of exposed terminals in IEEE 802.11 ad hoc networks in finite load conditions. It derives analytical models for the estimation of channel utilization and media access delay for IEEE 802.11 ad hoc networks in finite load conditions with and without exposed terminals. The simulation results show that the analytical estimated channel utilization and media access delay metrics are fairly accurate.

A pervasive architectural framework for providing remote medical treatment

The proliferation of mobile devices has led to their integration into a huge number of assistive environments where they perform a key role. Pervasive environments, built over wireless infrastructures, introduce new possibilities in the healthcare sector realizing the anytime-anywhere access to medical information paradigm. Towards this direction pervasive technology can be deployed in assistive environments, such as home monitoring for elderly or patients. In this paper we describe a policy based architecture that utilizes software agents and wireless sensor technologies to enable remote monitoring of patients and elderly people. We also discuss the technical challenges which directed the decisions with respect to the design of our software prototype architecture. These decisions mainly focus on providing continuous feedback of the patients condition, while transferring encrypted versions of the necessary medical information in accordance with the increased security and privacy requirements. The presented prototype implementation utilizes advanced network management technologies and software agent engineering in order to operate effectively, to achieve interoperability through the different modules and in order to comply with the imposed (by the legislative framework) increased security and privacy requirements.

Throughput analysis for IEEE 802.11 ad hoc networks under the hidden terminal problem

The paper proposes an analytical model, which deals with the channel utilization metric in IEEE 802.11 ad hoc networks. The basic advantage of the proposed model is that it considers the hidden terminal problem. Simulation results show that the model is fairly accurate.

A wireless distributed framework for supporting assistive learning environments

There is a lot of interest in developing environments utilizing various types of assistive technologies lately. Among else, people with specific difficulties may benefit from specially designed devices and software that aim in overcoming the disabilities of various groups. We describe a framework that aims in the provision of advanced services towards the facilitation of access to information for specific groups of people. Among else, our approach uses various tools and techniques. With wireless devices access to information is achieved independently of location, while with personalized services there is a capability to adjust the services and interfaces to various demands. Finally with a specific methodology that has been developed and tested as a result of international projects, the content and interfaces are adjusted to various needs of the participating user-groups.

End to end secure communication in ad-hoc assistive medical environments using secure paths

Recent advances in technology introduce many new capabilities for several sectors. Among else, the continuous improvement and integration of new features in mobile devices, allow their interoperation and integration to a large number of environments; primarily the medical sector may suffice from their utilization in order to monitor efficiently the condition of patients and provide feedback to specialists, especially in cases of absence of a stable (wired) network infrastructure. Strict security requirements emerge due to the sensitivity of data being transmitted, often imposed by different international legislation processes. We present an architecture that allows secure dissemination of medical information in a secure manner in the absence of stable topologies and infrastructures built upon resource efficient devices. The presented architecture utilizes advanced management techniques, achieving secure and privacy-preserving transmission of sensitive data. A number of initial measurements show the effective operation of our architecture in presence of an adequately large number of users participating in the performance test-bed scenario.

Using neural networks and SVMs for automatic medical diagnosis: A comprehensive review

In this paper we make a comprehensive review regarding the use of neural networks in automated medical diagnosis, with a special emphasis in Support Vector Machines (SVMs), which are specialized types of neural functions. Through the study, we see that, in many cases, symptoms and diseases can be efficiently predicted by neural systems, while SVMs are increasingly used in medical diagnosis due to their accurate classification characteristics.