Cognitive communication


 * Motivation

As broadcasting, cellular as well as other services have widespread, spectrum has become one of the most precious resources in wireless communications. Both in the United States and in Europe, spectrum regulatory bodies have been assigning spectrum bands in a licensed manner, meaning that a specific spectrum portion can legally only be exploited for a specific service with specific communication constraints. Although huge, the spectrum resource is actually not infinite, therefore the growth of wireless systems and services in the last decades made the availability of spectrum resources very scarce. Wireless cognitive communications represent a solution to the continuously growing spectrum demand by allowing unlicensed users to exploit temporarily available licensed spectrum.


 * Cognitive Radio

The concept behind cognitive communications is to allow cognitive users to transmit in temporarily unused spectrum bands, therefore providing a more efficient usage of the spectrum resource while preserving the rights of licensed users to use spectrum bands they paid for. In cognitive communications, cognitive users are generally referred as secondary users as opposite to legacy users, generally termed primary users. Cognitive communications over the wireless channel (Cognitive Radio) provide a paradigm that requires secondary users to be smart and flexible enough devices to handle with spectrum sensing and spectrum management so that their presence turn out to be almost transparent to primary users (as well as other secondary users) in terms of caused interference. The concept of Cognitive Radio was first introduced in a seminar by J. Mitola at KTH, The Royal Institute of Technology, in 1998 and then published in [Mitola99] by Mitola et al.. Mitola defined a cognitive radio as

[MitolaDissertation] “The point at which wireless personal digital assistants (PDAs) and the related networks are sufficiently computationally intelligent about radio resources and related computer-to-computer communications to detect user communications needs as a function of use context, and to provide radio resources and wireless services most appropriate to those needs”.

In terms of information theory, a definition of Cognitive Radio is provided in terms of network side information

[Goldsmith09] "a cognitive radio is a wireless communication system that intelligently utilizes any available side information about the a) activity, b) channel conditions, c) codebooks, or d) messages of other nodes with which it shares the spectrum".

REFERENCES

[Goldsmith09] A. Goldsmith, S.A. Jafar, I. Maric, and S. Srinivasa, "Breaking Spectrum Gridlock With Cognitive Radios: An Information Theoretic Perspective," Proceedings of the IEEE, vol.97, no.5, pp.894-914, May 2009

[Mitola99] J. Mitola III and G. Q. Maguire Jr., “Cognitive Radio: Making Software Radios More Personal,” in IEEE Personal Comm., Aug. 1999.

[MitolaDissertation] J. Mitola, "Cognitive Radio An integrated Agent Architecture for Software Defined Radio," Doctoral Dissertation, 2000.