Cognitive Radio

frequency allocation

Cognitive Radio

A cognitive radio is a transceiver that dynamically switches between optimal wireless channels in its vicinity. It automatically detects available channels, then accordingly changes its transmission or reception parameters to allow more concurrent wireless communications in a given spectrum band at one location. This process is a form of dynamic spectrum management.

The cognitive engine is capable of configuring waveform, protocol, operating frequency, and networking parameters. Units can exchange information about the environment with the networks it accesses and other cognitive radios (CRs). A CR ‘monitors its own performance continuously,’ in addition to ‘reading the radio’s outputs’; it then uses this information to ‘determine the RF environment, channel conditions, link performance, etc.’, and adjusts the ‘radio’s settings to deliver the required quality of service subject to an appropriate combination of user requirements, operational limitations, and regulatory constraints.’

Some ‘smart radio’ proposals combine wireless mesh network—dynamically changing the path messages take between two given nodes using cooperative diversity; cognitive radio—dynamically changing the frequency band used by messages between two consecutive nodes on the path; and software-defined radio—dynamically changing the protocol used by message between two consecutive nodes.

The concept of cognitive radio was first proposed by software radio pioneer Joseph Mitola III in a seminar at KTH (the Royal Institute of Technology in Stockholm) in 1998 and published in an article by Mitola and KTH professor of communications Gerald Q. Maguire, Jr. in 1999. It was a novel approach in wireless communications, which 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.’ Cognitive radio is considered as a goal towards which a software-defined radio platform should evolve: a fully reconfigurable wireless transceiver which automatically adapts its communication parameters to network and user demands.

Traditional regulatory structures have been built for an analog model and are not optimized for cognitive radio. Investigations by national regulatory bodies, including the FCC, as well as different independent measurement campaigns found that most radio frequency spectrum was inefficiently utilized. Cellular network bands are overloaded in most parts of the world, but other frequency bands (such as military, amateur radio, and paging frequencies) are underutilized. Independent studies performed in some countries confirmed that observation, and concluded that spectrum utilization depends on time and place. Moreover, fixed spectrum allocation prevents rarely used frequencies (those assigned to specific services) from being used, even when any unlicensed users would not cause noticeable interference to the assigned service. Regulatory bodies in the world have been considering whether to allow unlicensed users in licensed bands if they would not cause any interference to licensed users. These initiatives have focused cognitive-radio research on dynamic spectrum access.



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