Today's wireless services have come a long way but there has always been a problem of spectrum management in wireless communication and though many solutions have been provided, still none of them can fully rectify the issues associated. The recent outbreak in the form of Cognitive Radio (CR) has the potential to increase spectrum utilisation and desired interference protection to licensed users.
Cognitive Radio, being defined as the new state of the art technique, is an efficient technology oriented towards the intelligent usage of the available frequency spectrum and avoiding interference to facilitate congestion-less data transmission. It has the ability to adapt itself dynamically to utilise radio resources in time, frequency and space domains based on the careful inspection of the instantaneous requirements in a radio environment taking into consideration the various user demands and interference in that particular area.
It provides an opportunity to utilize the unused section of the spectrum, known as "TV White Space", without going for an increase in the spectrum provided. The main spectrum is currently located for broadcast television providers. The use of this unused spectrum is made in such a way that the other wireless services that are being deployed do not cause any interference to the television broadcast signals.
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Because of its numerous characteristics and intelligent adaptation parameters, cognitive radios find a lot of applications related to secure and reliable communication such as military applications, public safety communications, secured data transmission in highly interfering environment etc. It is their unique adaptation capability that makes the communication undetectable for the external threats and hence allows confidential conversations to be carried out in a secured way.
Cognitive Radio technology, being combined with the Spread Spectrum modulation techniques can provide a highly secure communication format, resistant to deliberate jamming and other obstruction tactics. Spread Spectrum technique, because of its unique feature to make the data look like noise, is very much secure in the sense that the jamming and the interfering elements are unable to distinguish the data (mixed with noise) being sent over the channel and hence it is a possible solution to avoid eavesdropping or information leakage.
Even the various encryption techniques such as public key encryption (RSA, Elliptic, SHA) and private key encryption (DES, Triple DES, AES) algorithms can be used, in tandem, with cognitive radio to provide a form of secure communication. These encryption algorithms make sure that the key that is used at the transmitter side should be provided by the receiver (just like the pseudorandom sequence used in spread spectrum modulation) for correct information retrieval and hence ensures the security and also prevent the malicious users from taking control over the system, blocking the access to other secondary users.
CR technology also finds various Geo-location and Networking applications such as: teenager tracking, blue force tracking, location augmented routing, location of services, biometric authentication applications, planning etc. In addition, it may also be useful to implement interoperability between different public safety wireless protocols. It helps in maintaining a balance between the incompatible channels, operation modes and different protocols and hence ensuring the interoperability among a multitude of public safety network users.
In summary, a CR can be viewed as a combined application of Software Defined Radio (SDR) and intelligent signal processing with functional elements of radio flexibility, spectral awareness and the intelligence of decision-making.
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