An overview on cooperative spectrum sensing in cognitive radios

Abstract

With the advent of wireless technology, a large number of devices are continuously accessing the frequency spectrum. As the number of mobile devices is increasing, the contention for spectrum utilisation is seriously challenging the spectrum availability. The entire usable frequency spectrum is divided into licensed and open or unlicensed spectrum. While the unlicensed spectrum (ISM Bands) is open for applications like Bluetooth, Wi-Fi, cordless phones, some broadband radios etc., the licensed spectrum is commercially allocated to the intended user centrally through an international body. As the commercial licensed band is largely unutilised, the cognitive radio (CR) approach has resulted in optimal utilisation of entire frequency spectrum. A cognitive radio searches for a vacant licensed spectrum which is unutilised and can be made available for use by cognitive radios. In order to achieve this functionality, CR makes use of spectrum sensing for effective allocation of unlicensed and licensed spectrum. A number of CR jointly detect the free frequency spots to form a network of CR. Such type of collaborative spectrum sensing is known as cooperative sensing. This papers aims at highlighting various spectrum sensing techniques which are prevalent in realms of CR.