Introductory Chapter: Primary and Secondary Users in Cognitive Radio-Based Wireless Communication Systems [chapter]

Shahriar Shirvani Moghaddam
2018 Cognitive Radio in 4G/5G Wireless Communication Systems  
Additional information is available at the end of the chapter Wireless communications and the necessity of cognitive radio Wireless communication systems play a special role in human life, facilitate the life, and change the world much more in the future. The diversity of applications and services of wireless communications indicates the widespread use of wireless systems and equipment in the future. Since the first radio link by Marconi in 1896, it has been more than 120 years, and several
more » ... less communication systems have been introduced up to now. Meanwhile, the advancement of cellular wireless communications, whose idea came back to 1947 and their first generation in 1978 (namely advanced mobile phone service), has been well adopted and has grown dramatically, so that the researchers and operators are focused on standardization and design of 5G and 6G wireless communication systems [1] . From the beginning, one of the main problems in wireless communications is the scarcity of radio resources (frequency, time, and power). In recent years, the lack of frequency spectrum and the necessity of frequency reuse at different times and places and reduction of the consumed power are of great importance. Looking at the following laws: • Moore's law: The number of transistors that can be cheaply placed on a microchip doubles and the computer power exponentially increases approximately every 2 years [2] • Cooper's law: The number of voice calls or data that can be sent over the usable radio spectrum doubles every 30 months [2]
doi:10.5772/intechopen.82033 fatcat:cwflydi5qrbobk2lmpyxzqvdfe