Citizendia

Cognitive radio is a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users. Cognition is a concept used in different ways by different disciplines but is generally accepted to mean the process of awareness or thought Wireless communication is the transfer of information over a distance without the use of electrical conductors or " Wires quot Communication is the process of conveying information from a sender to a receiver with the use of a medium in which the communicated information is understood the same way A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics Wireless communication is the transfer of information over a distance without the use of electrical conductors or " Wires quot A node ( Latin nodus, ‘knot’ is a critical element of any Computer network. In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or In Mathematics, Statistics, and the mathematical Sciences a parameter ( G auxiliary measure) is a quantity that defines certain characteristics This alteration of parameters is based on the active monitoring of several factors in the external and internal radio environment, such as radio frequency spectrum, user behaviour and network state. Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz In Telecommunications, a user is a person organization or other entity that employs the services provided by a Telecommunication system or by an Information A telecommunications network is a network of Telecommunications links and nodes arranged so that messages may be passed from one part of the network to another over

Contents

History

The idea of cognitive radio was first presented officially in an article by Joseph Mitola III and Gerald Q. Cognition is a concept used in different ways by different disciplines but is generally accepted to mean the process of awareness or thought Maguire, Jr in 1999. [1] It was a novel approach in wireless communications that Mitola later described as:

The point in 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. [2]

It was thought of as an ideal goal towards which a software-defined radio platform should evolve: a fully reconfigurable wireless black-box that automatically changes its communication variables in response to network and user demands. A Software-Defined Radio (SDR system is a Radio communication system where components that have typically been implemented in hardware (i Black box is a technical term for a device or system or object when it is viewed primarily in terms of its input and output characteristics

Regulatory bodies in various countries (including the Federal Communications Commission in the United States, and Ofcom in the United Kingdom) found that most of the radio frequency spectrum was inefficiently utilized. The Office of Communications (Y Swyddfa Gyfathrebiadau or as it is more often known Ofcom is the independent regulator and competition authority for the Communication Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz [3] For example, cellular network bands are overloaded in most parts of the world, but amateur radio and paging frequencies are not. A cellular network is a Radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter known as a Cell Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications A pager (sometimes called a beeper) is a simple personal Telecommunications device for short messages Independent studies performed in some countries confirmed that observation,[4][5] and concluded that spectrum utilization depends strongly on time and place. Moreover, fixed spectrum allocation prevents rarely used frequencies (those assigned to specific services) from being used by unlicensed users, even when their transmissions would not interfere at all with the assigned service. This was the reason for allowing unlicensed users to utilize licensed bands whenever it would not cause any interference (by avoiding them whenever legitimate user presence is sensed). This paradigm for wireless communication is known as cognitive radio. Cognition is a concept used in different ways by different disciplines but is generally accepted to mean the process of awareness or thought

Terminology

Depending on the set of parameters taken into account in deciding on transmission and reception changes, and for historical reasons, we can distinguish certain types of cognitive radio. The main two are:

Also, depending on the parts of the spectrum available for cognitive radio, we can distinguish:

Technology

Although cognitive radio was initially thought of as a software-defined radio extension (Full Cognitive Radio), most of the research work is currently focusing on Spectrum Sensing Cognitive Radio, particularly in the TV bands. A Software-Defined Radio (SDR system is a Radio communication system where components that have typically been implemented in hardware (i Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic The essential problem of Spectrum Sensing Cognitive Radio is in designing high quality spectrum sensing devices and algorithms for exchanging spectrum sensing data between nodes. It has been shown[8] that a simple energy detector cannot guarantee the accurate detection of signal presence, calling for more sophisticated spectrum sensing techniques and requiring information about spectrum sensing to be exchanged between nodes regularly. Increasing the number of cooperating sensing nodes decreases the probability of false detection. [9]

Filling free radio frequency bands adaptively using OFDMA is a possible approach. Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz Orthogonal Frequency-Division Multiple Access ( OFDMA) is a multi-user version of the popular Orthogonal frequency-division multiplexing (OFDM digital modulation scheme Timo A. Weiss and Friedrich K. Jondral of the University of Karlsruhe proposed a Spectrum Pooling system[10] in which free bands sensed by nodes were immediately filled by OFDMA subbands. The University of Karlsruhe, also known as Fridericiana, was founded in 1825 Orthogonal Frequency-Division Multiple Access ( OFDMA) is a multi-user version of the popular Orthogonal frequency-division multiplexing (OFDM digital modulation scheme

Applications of Spectrum Sensing Cognitive Radio include emergency networks and WLAN higher throughput and transmission distance extensions. Professional Mobile Radio (also known as Private Mobile Radio (PMR in the UK and Land Mobile Radio (LMR in North America are field radio communications systems which use portable In Communication networks, such as Ethernet or Packet radio, throughput is the average rate of successful message delivery over a communication channel In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or

Main functions

The main functions of Cognitive Radios are:[11]

Cognitive radio (CR) vs. The Media Access Control (MAC Data communication protocol sub-layer also known as the Medium Access Control is a sublayer of the Data Link Layer specified in the Intelligent antenna (IA)

Intelligent antenna (or smart antenna) is antenna technology that uses spatial beamforming and spatial coding to cancel interference; however, it requires intelligent multiple or cooperative antenna array. In Radio, multiple-input and multiple-output, or MIMO (pronounced mee-moh or my-moh) is the use of multiple antennas at both the transmitter Smart antennas (also known as adaptive array antennas multiple antennas and recently MIMO) are Antenna arrays with smart signal processing algorithms used to identify On the other hand, cognitive radio (CR) allows user terminals to sense whether a portion of the spectrum is being used or not, so as to share the spectrum among neighbor users. The following table compares the different points between two advanced approaches for the future wireless systems: Cognitive radio (CR) vs. Intelligent antenna (IA).

PointCognitive radio (CR)Intelligent antenna (IA)
Principal goalOpen Spectrum SharingAmbient Spatial Reuse
Interference processingAvoidance by spectrum sensingCancellation by spatial pre/post-coding
Key costSpectrum sensing and multi-band RFMultiple or cooperative antenna arrays
Challenging algorithmSpectrum management techIntelligent spatial beamforming/coding tech
Applied techniquesCognitive Software RadioGeneralized Dirty-Paper and Wyner-Ziv coding
Basement approachOrthogonal modulationCelluar based smaller cell
Competitive technologyUltra wideband for the higher band utilizationMulti-sectoring (3, 6, 9, so on) for higher spatial reuse
SummaryCognitive spectrum sharing technologyIntelligent spectrum reuse technology

See also

References

  1. ^ IEEE Xplore - Login
  2. ^ http://www.it.kth.se/~jmitola/Mitola_Dissertation8_Integrated.pdf
  3. ^ IEEE Spectrum: The End of Spectrum Scarcity
  4. ^ IEEE Xplore - Login
  5. ^ IEEE Xplore - Login
  6. ^ IEEE 802.22
  7. ^ IEEE 802.15.2
  8. ^ http://www.eecs.berkeley.edu/wireless/posters/WFW05_cognitive.pdf
  9. ^ IEEE Xplore - Login
  10. ^ IEEE Xplore - Login
  11. ^ doi:10.1016/j.comnet.2006.05.001
  12. ^ Natasha Devroye, Patrick Mitran and V. In Radio, Multi-user MIMO (MU-MIMO is a set of advanced MIMO, multiple-input and multiple-output (pronounced mee-moh or my-moh) Tarokh, Limits on Communication in a Cognitive Radio Channel," IEEE Communications Magazine, pp. 44-49, June 2006.

External links

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