In parallel with the need for cost- and energy-efficient reconfigurable radio implementations, there is as a matter of fact also a growing need to make next-generation terminals more intelligent and adaptive. Through appropriate radio management, these terminals should make flexible and efficient use of network/spectrum resources, so as to enable connectivity across complex and spectrum-constrained wireless networking environments.
Anything, anywhere, anytime: the query is not new. Still, offering ubiquitous wireless connectivity and seamless access to multimedia services is not yet a reality. Next-generation mobile terminals will have to face two main challenges to enable this vision: (A) the need for cost- and energy-efficient reconfigurable radio implementations, and (B) the need to make these terminals more intelligent (cognitive) and adaptive, through appropriate radio resource management.
Regarding the second challenge, through appropriate radio management, these terminals should make flexible and efficient use of network/spectrum resources, so as to enable connectivity across complex and spectrum-constrained wireless networking environments. Next-generation communication systems will indeed have to enable seamless connectivity across heterogeneous wireless environments shown in the illustration below.
A fundamental enabler in this direction is the increasing flexibility offered by emerging reconfigurable radio platforms on the one hand and by emerging communication networks on the other hand. By properly managing this flexibility, one can enable significant improvement, for instance in terms of connectivity or energy efficiency. Also, a current trend in wireless communication and in spectrum regulation is the evolution towards dynamic and open access to radio spectrum. This is motivated by the under-utilization of many licensed frequency bands and the continuously increasing demand for large data rates. New paradigms for efficiently exploiting the spectrum will definitely be needed in this context. An evolution to more flexible use is needed according to regulatory bodies.
This has lead to the concept of cognitive radio, first coined in, which is defined on the most generic way as follows; “A radio that can autonomously change its transmission parameters based on interaction with and learning of the environment in which it operates.”
A second acceptation of cognitive radio (often referred to as opportunistic radio) is the following one; “A radio that co-exists with legacy wireless systems using the same spectrum resources without significantly interfering with them.”
The SDR solutions described in the present book are of course paving the way in this direction. However, several significant extensions are needed to enable cognitive radio terminals.
