Mobile Middleware Solutions for the Adaptive Management of Multimedia QoS to Wireless Portable Devices Paolo Bellavista, Antonio Corradi Dip. Elettronica, Informatica e Sistemistica - Università di Bologna Viale Risorgimento, 2 - 40136 Bologna - ITALY Phone: +39-051-2093001; Fax: +39-051-2093073 {pbellavista, acorradi}@ deis.unibo.it Abstract New challenging service scenarios are integrating wireless portable devices with limited and heteroge- neous capabilities. They are expected to access both traditional and novel (context-dependent) Internet ser- vices. This not only calls for novel infrastructures to support the integration of mobile devices with the fixed network, but also stresses the necessity of nego- tiation-time tailoring and provision-time adaptation of Quality of Service (QoS). The paper presents a flexi- ble and dynamic middleware for the management of multimedia QoS to wireless devices that can roam during service provisioning. The middleware exploits mobile agents that act as device shadow proxies over the fixed network to transparently follow the device movements between wireless localities, to negotiate the proper QoS level, and to dynamically adapt mul- timedia flows depending on device profiles and user preferences. In particular, the paper focuses on how the middleware achieves the on-line visibility of the device change of locality in a portable way over dif- ferent implementations of different wireless technolo- gies, i.e., IEEE 802.11 and Bluetooth. The first ex- perimental results show that, notwithstanding the ap- plication-level approach, the middleware reorganiza- tion time is compatible with the requirements imposed by the addressed multimedia scenario. 1. Introduction Recent advances in wireless networking and the enlarging market of wireless-enabled portable devices stimulate the provisioning of distributed services to a wide set of client terminals with very heterogeneous and limited resources. Service providers and wireless network operators have to face new challenging and state-of-the-art technical issues, toward both the de- ployment of distributed applications for mobile ad-hoc networks and the full seamless integration of wireless client devices with the traditional fixed Internet. The first scenario is just moving its first steps and still in- vestigating solutions mostly at the network level, e.g., for multi-hop cooperative routing [1]. At the opposite, the second scenario, which we will call wireless Inter- net in the following, already starts to exhibit research and commercial network-level solutions to support mobile connectivity [2, 3]. However, the investigation of several aspects of service accessibility in the global and open wireless Internet, such as dynamic un/installation of infrastructure/service components, configuration management, service content adaptation, security, and interoperability, is still at its beginning and calls for flexible state-of-the-art middleware solu- tions at the application level [4, 5]. In addition, the wireless Internet stimulates re- search on several novel classes of services (and on methodologies for their development) where service results and the offered Quality of Service (QoS) levels may depend on the provisioning context, i.e., the logi- cal set of resources that a client can access due to some properties of the provisioning environment, such as client location, access device capabilities, user prefer- ences, and mutual relationships with currently local users/terminals [6]. In particular, the provisioning of context-dependent services for the wireless Internet must take into con- sideration the specific constraints of access portable devices, i.e., their limits on local resources and their high heterogeneity. On the one hand, limited process- ing power, memory and file system make portable de- vices unsuitable for traditional services designed for the fixed network and require downscaling to fit less powerful access terminals. On the other hand, portable devices exhibit heterogeneity of hardware capabilities, installed operating systems, supported software and network technologies. Heterogeneity makes impossible to provide all needed service versions with the suitable and statically tailored QoS levels. Middleware solu- Proceedings of the Ninth IEEE International Workshop on Object-Oriented Real-Time Dependable Systems (WORDS’03) 0-7695-2054-5/04 $20.00 © 2004 IEEE