Cross-Layer Design and Optimization in Wireless Networks

Communication networks have traditionally been engineered following the principle of protocol layering. This means designing specic network functionalities (such as ow control, routing, medium access) in isolation from each other, and putting together the complete system through limited interfaces between the layers performing these specic tasks. The layers, which are in fact distributed systems with collaborating entities distributed through the network [6, p. 20], are arranged in a vertical hierarchy. Each layer makes use of the services provided by the layers below itself and, in turn, makes its services available to the layers above itself. Inter-layer communication happens only between adjacent layers and is limited to procedure calls and responses. Familiar examples of layered communication architectures are the seven-layer Open Systems Interconnect (OSI) model [6, p. 20] and the four-layer TCP/IP model [39]. Even though layered communication architectures have been instrumental in the development of many communication networks, most notably the Internet, in recent times, the suitability of protocol layering is being questioned in the research community. This is largely due to wireless networks becoming an integral part of the communications