Antonis Athanasopoulos

Implementation of power aware features in AODV for ad hoc sensor networks. A simulation study

Ad hoc wireless networks are power constrained since nodes operate with limited battery energy. Thus, energy consumption is crucial in the design of new ad hoc routing protocols. To design such protocols, we have to look away from the traditional minimum hop routing schemes. This paper presents an energy-aware routing mechanism to balance the energy consumption among the nodes of the network. The mechanism was based on the AODV protocol using a realistic energy consumption model which takes into account the battery of a node and the transmission energy. The results show that the modified AODV protocol reduces the energy consumption of the nodes by routing packets to their destination using energy-optimal routes. The outcome is the improvement of network survivability by maintaining the network connectivity without affecting negatively the others parameters of the protocol.

Evaluation Analysis of the Performance of IEEE 802.11b and IEEE 802.11g Standards

The IEEE 802.11 Wireless LAN standard is one of the most popular wireless standards in the market today. Since 1997 when the first version of the IEEE 802.11 was launched in the market, a lot of different versions has been announced and developed. In this paper, a comprehensive evaluation analysis of the IEEE 802.11b and IEEE 802.11g has been carried out, examining the performance of both standards at the MAC sub-layer, in terms of QoS, using two different simulation tools. Finally, the comparison for both cases is discussed.

802.15.4: The Effect of Different Back-off Schemes on Power and QoS Characteristics

IEEE 802.15.4 LR-WPAN is intended as a specification for low-cost, low-powered networks with no critical concerns about throughput and latency. These features enable applications in the fields of industrial, agricultural, vehicular, residential and medical sensors as well as actuators, such as wireless monitoring and control of lights, security alarms, motion sensors, thermostats and smoke detectors, which cannot make use of current wireless technologies or have to use proprietary solutions. However, when dealing with wireless networks, optimized power management and better QoS characteristics are always a topic of great importance. In this paper, an evaluation of the effect of different back-off schemes of MAC algorithm, on power and QoS characteristics is presented.

Security and DRM in indoor/outdoor heterogeneous networking applications for user - centric frameworks

As networks become more and more complicated and applications more and more demanding, a very common network topology for state-of-the-art multimedia applications supporting emerging user - centric frameworks is a heterogeneous wired/wireless architecture. A network architecture solution for indoor/outdoor heterogeneous networking applications, to support both multimedia and sensor applications suitable for such frameworks is proposed in this paper. Furthermore, an integrated DRM system architecture is proposed for the protection of intellectual property, characterized by its interoperability aspect.

Comparative performance evaluation of 802.15.4 and 802.11b for usage in ad-hoc wireless networks

The IEEE 802.15.4 is a relatively new standard, targeted specifically at personal wireless networks. However the characteristics it offers, like low power consumption, cost and complexity, are very appealing for a wider range of networks like ad-hoc wireless ones. It is very interesting to examine the performance of 802.14.5 compared to 802.11b under various ad-hoc network conditions. In this paper a thorough simulation based evaluation is presented for these two MAC layer protocols as well as a discussion is taking place whether 802.15.4 could in fact substitute 802.11b in certain cases.

A framework architecture supporting QoS-power trade-offs for heterogeneous network systems

Power awareness and quality of service (QoS) integration in wireless systems are two of the main research activities in wireless systems today. As frameworks are developed to handle dynamic reconfiguration, the need for a power optimization methodology to investigate alternative cross-layer configurations is imposed as critical. However, as networks become more complex and energy savings become critical, this leads to the consideration of constructs for treating QoS-power trade-offs and adjust to the heterogeneous nature of network systems. In this paper, we propose an interoperable architecture for a hybrid wired-wireless network, where communication is treated transparently and enhancements are proposed to improve QoS by the definition of a framework also supporting dynamic power optimization

Implementation and evaluation of a Greek Text To Speech System based on an Harmonic plus Noise Model

The use of text to speech (TTS) systems beyond pure scientific applications has been gaining ground and has been incorporated in everyday life aspects. Thus, the development of TTS system, that can produce synthesized speech of high quality is more than necessary in state-of-the-art everyday life applications. This paper evaluates the performance of a TTS using harmonic plus noise model (HNM) - a speech analysis/synthesis algorithm, as part of its DSP module. A TTS for the Greek language is studied with respect to its DSP module and an evaluation is presented of the HNM algorithm in terms of overall performance and the impact of its attributes on the results quality.

A simulation study on dropping tendencies of an ad-hoc wireless network

This paper aims to study and analyze lost packet tendencies for ad hoc wireless networks. Lost packets greatly influence all performance aspects of such a network. Moreover, lost or drop packets are directly involved in many active research fields concerning ad hoc network nowadays. Accordingly, investigating the various kinds of packets dropped more frequently in conjunction with critical network parameters, can result in very usefully conclusions. These conclusions can give new insights in designing new protocols and more importantly in cross-layer designs in order to enhance the performance of the whole network.

Framework Design Supporting QoS-Power Trade-Offs for Heterogeneous Networked Systems

The work reported here was performed as part of the ongoing research Program PYTHAGORAS II and funded by the European Social Fund (ESF), in particular by the Operational Program for Educational and Vocational Training II (EPEAEK II).Two of the main research efforts in wireless systems, nowadays, are the Power awareness and Quality of Service (QoS) integration. As frameworks are developed to handle dynamic reconfiguration, the need for a power optimization methodology to investigate alternative cross-layer configurations is critical. However, as networks become more complex and energy savings become crucial, this leads to the consideration of constructs for treating QoS-power trade-offs and adjust to the heterogeneous nature of network systems. In this paper, we propose an interoperable framework design for heterogeneous network systems, where communication is treated transparently and enhancements are proposed to improve QoS by the definition of a framework also supporting dynamic power optimization.