Cross-layer optimization for wireless systems: a european research key challenge

Anew design paradigm has recently arisen in wireless communications research: so-called cross-layer optimization. In fact, this implies the redefinition of the overall design strategies for this kind of system as it breaks the classical open systems interconnection (OSI) model. The endless need for higher bit rates, stringent quality of service (QoS) requirements, and need for anytime anywhere wireless connections lead to the necessity of squeezing to the outmost the available radio bandwidth. Cross-layer plays a key role in achieving this goal. Literature on ross-layer-related issues is still relatively scarce, but recently published results show that the potential obtainable gains deserve the increasing attention cross-layer is getting. European research efforts on this topic have been increasing in the last years, and currently active research lines on this topic are gaining relevance. New Design Concept During the last decade, significant growth of digital wireless communications systems has arisen. Wireless networks initially inherited the traditional OSI-layer-based architecture from wired networks, where each layer is worked out based on its parameters as a separate entity. The OSI model is a widely known, well accepted framework for communication systems [1, 2]. With this model, systems are decomposed in seven layers (physical, link, network, transport, session, presentation, and application). Each is responsible for a subset of the system’s operational functions. Messages are interchanged between entities of the same layer in both the transmitter and receiver. Each layer is aware of its own messages and embeds its information into upper layer messages when they go down in the layer stack, while it discards the lower layers’ informa