A Framework Architecture Supporting QoS-Power Trade-offs for Heterogeneous Network Systems C. Antonopoulos, A. Athanasopoulos, S. Giannoulis, A. Prayati, E. Topalis, S. Koubias Applied Electronics Laboratory, Department of Electrical & Computer Engineering University of Patras, Rio Campus, Greece (cantonop, athan, sgiannoulis, prayati, topalis, koubias)@ee.upatras.gr Abstract 1 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. 1. Introduction The need for interoperability of heterogeneous wired/wireless networks stems from the requirement for integrating the communication constructs in advanced industrial control applications. As the complexity degree of these applications increases over the years, miscellaneous network traffic must be curried through different mediums in a macroscopically homogeneous way. An interoperable architecture is thus required for a hybrid 802.11 [1] and Ethernet [2] network system, where communication is treated transparently to the higher-levels. Designing such an architecture is a complex task since two very different network architectures must interoperate. On one hand, there is a very well known network such is the wired Ethernet tested in all sort of application environments and able to cope with high time constrained demands. On the other hand, the relatively new ad hoc networks, which 1 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). although has attracted a great deal of research interest in the resent years still lack in all performance parameters compared with the wired Ethernet networks [3]. In any case, it is critical that from the user point of view the whole system is seen as a black box and is expected to function equally well independently from its heterogeneity concerning the wired and wireless parts that comprise it. Consequently, the introduction of new constructs is required along with novel protocols in MAC and Network layers, which will diminish the deficiencies of the wireless part so as to cooperate smoothly with the wired counterpart. Besides dealing with heterogeneity, the innovative protocols for the wireless part tend to consider QoS parameters in order to improve network performance. However, the mobile nature of network systems under study imposes an imperative requirement for the network node life-cycle extension in terms of power consumption minimization. Power-awareness involves also higher-level parameters and thus a cross-layer middleware is required to handle power aspects in distributed networks of high heterogeneity. In this paper, an interoperable middleware architecture is proposed, handling network heterogeneity and QoS tenability. Also a great benefit from the development of this framework is to study the trade-offs that exist between critical network parameters like QoS and power consumption so as to find the optimal balance between them especially as far as power aware interoperable networks are concerned. Additionally, application layer is also involved in this cross-layer study of the wireless network stack with respect to its impact on network communication and its performance concerning network parameters like delay, throughput and power consumption. In section 2, related work is discussed and in section 3 the middleware architecture and optimization objectives are presented. The network and MAC layer QoS-related enhancements are defined in section 4 and the case study application is described in section 5. 0-7803-9402-X/05/$20.00 © 2005 IEEE