The evolution of mobile radio networks is leading to the definition of communication systems with very high capacity and complexity which are able to exploit at best the available transmission resources in terms of space, time and frequency bands. To achieve this goal, each system in the network must be able to collect information on the channels occupation in the areas in which it operates. This task is performed by means of suitable detection and identification functions, allowing the system to locate these resources and use them on an opportunistic basis, avoiding interference with other users, especially if they have the channel access rights.
The systems outlined here are called cognitive and networks formed by such systems are commonly called cognitive radio networks in the scientific literature.
The use of cognitive systems in the construction of the broadband mobile networks leads to a significant increase in the efficiencyof utilization of radio resources, improving the availability and quality of services offered.
The main objective of the research and development activities in this area is the realization of a cognitive network prototype capable of independently detecting the available channels, coordinating with other nodes and exploit the transmission opportunities.
Cognitive systems consist of three main subsystems: the spectrum sensing unit, the receiver and transmitter unit (transceiver) and the radio resource management and coordination unit.
The spectrum sensing unit makes the system able to detect and identify any transmissions of primary users. Has been carried outa research that has focused on the study, the design, development and testing of algorithms that can effectively detecttransmissions of OFDM type. The algorithms implemented require a more in depth in different propagation conditions.Furthermore, it is necessary to improve the characteristics and especially expand the number of modulations that the system is able to detect.
It is also necessary to provide the system algorithms for the transmission at high speed and algorithms for the coordination between the nodes, algorithms are able to efficiently exploit the available spectrum and provide a high quality of service while minimizing interference with other systems.
Unversity of Rome La Sapienza
Politecnico di Torino