Section: Scientific Foundations

Flexible Radio Node design

To cope with terminal flexibility, the terminals' complexity is constantly increasing with the multiplicity of radio interfaces on the market. It is nowadays impossible to develop an all-standards-compliant terminal since most standards are permanently under development. Therefore, the wireless convergence at the application level is possible only by superposing several radio interfaces within the same terminal. This strategy is neither cost efficient, nor optimal from the compactness points of view, and prohibiting any system adaptability. Further, the time to market of the new technologies is also slowed down, because the future evolutions are conditioned to the usual backward compatibility that often limits the capabilities of new technologies.

Since the seminal paper of J. Mitola in 1991, the concept of Software Radio appeared progressively as a key technology to offer adaptable and full-compliant radio systems. If a full software radio system remains futuristic, some software defined radio architectures are already on the market (picochip, EVP,Lyrtech SFF SDR, GNU radio platforms). Moreover, the concept of cognitive radio requires that the terminal is aware of the available radio resources on a wide set of frequencies. Several problems are still open:

• What will be the emerging hardware paradigm for software radio? Multi-processor on chip are now available but there are room for many experimental study to focus the target software radio computation model.

• What will be the programming model for software defined radio? What will be the emerging waveform description language? Some attempts have been made to define a radio virtual machine but research direction are still widely open.

• wireless nodes design offering to the upper layers the required agile radio capabilities for self-optimizing networks is still an open problem, especially to consider simultaneously the three objectives: QoS, Energy consumption and Security.

• What kind of RF architecture do software defined radio need ? Wideband or multiband capabilities that are mandatory for dynamic spectrum sensing and resource management strongly constrain the RF design.

The first challenge is then the optimization of wireless nodes with respect to our three common objectives (QoS, Energy consumption and Security) while offering to the upper layers the required agile radio capabilities for self-optimizing networks..