International Journal of Computer Applications (0975 – 8887) Volume 74– No.10, July 2013 10 Cognitive Radio New Dimension in Wireless Communication – State of Art Rajwinder Singh Dept. of Electronics Technology Guru Nanak Dev University Amritsar, India Jasvir Singh Dept. of Electronics Technology Guru Nanak Dev University Amritsar, India A.S. Kang Dept. of Electronics and Comm. Panjab University Chandigarh, India ABSTRACT In today‘s wireless communication environment, the Radio Frequency spectrum is occupied for different purposes like cellular, Television, military, emergency or satellite communication. The frequency spectrum used for cellular communication is getting over crowded with increasing number of subscribers and demand for high data rate text or video transmission, but the frequency spectrum in other wireless broadcast and communication is not utilized efficiently, example in Television broadcast band, some of frequency spectrum is vacant at some instant or for particular time. The vacant spectrum could be used in cellular communication, means the spectrum is borrowed from Television Broadcast band to be used for cellular communication. A borrow/use of spectrum from other licensed frequency bands will improve the efficiency of spectrum use. In this paper, aspects of Cognitive Radio and comparison of different sensing techniques and methods are discussed. Secondly, the layer architecture of Cognitive Radio is presented. Thirdly, hardware and software platforms are discussed for Cognitive Radio testing. Keywords Cognitive Radio, Software Defined Radio, Spectrum Sensing, Primary User, Secondary User, Transmit Power Control and Dynamic Spectrum Management. 1. INTRODUCTION The Cognitive Radio is a radio that can borrow/use spectrum by sensing vacant or white space in spectrum from their surroundings, adapt it and can change frequency dynamically based on its location and other neighbouring radios by learning their spectrum pattern. Ability of CR is to recognize spectrum availability and reconfigure itself for efficient spectrum use. CR provides more radio spectrum for cellular communication, more bandwidth as per requirement for transmission, and interoperability between communication systems. By the mean of Cognitive Radio technology, the high data rate could be achieved for multimedia applications. Cognitive Radio covers the services such as speaker recognition, language identification then translation into another, text-to- speech conversion, speech-to-text conversion, noise suppression, and noise management. For military applications, Cognitive Radio will allow finding free channel automatically to communicate instead of manually setting to a particular radio channel. Another benefit, CR can resist the jamming in a particular area where radio signal jammers are used and some radio spectrum is restricted. In disaster and emergency condition, due to over-crowding of the radio spectrum collapses the communication system. In such circumstances when radio spectrum is completely occupied and no direct link is available to the access point. But through other CR terminals, access point is reachable by forming spontaneous network. Cognitive Radio is discussed in the following sessions: in session 2-history of Cognitive Radio is discussed in flow of technologies from analog domain to intelligent domain, in session 3-working cycle of CR and its sensing methods and techniques are discussed, in session 4- architecture of CR is discussed in accordance with its functions layer by layer, in session 5-hardware platforms and testbeds which are established for testing of Cognitive Radio, and in session6-software platforms are discussed for implementation of Cognitive Radio. 2. HISTORY OF COGNITIVE RADIO The roadmap to Cognitive Radio technology starts from analog domain to intelligent domain in the following phases as shown in figure 1. a) Analog Radio Analog is the standard method of radio broadcasting where the entire spectrum of radio frequencies is transmitted in a continuous flow of waveform data with amplitude or frequency modulation technique. Nikola Tesla wirelessly transmitted electromagnetic energy. Guglielmo Marconi sent first wireless signal across Englishchannel in 1899 and Jagadish Chandra Bose‘s 1904 US patent described Galena Crystal detector for demodulating continuous wave radio signals [1]. b) Digital Radio Digital radio describes radio communications technologies which carry information as a digital signal, by means of digital modulation techniques. The baseband signal implemented on a Digital Signal Processing. c) Software Capable Radio The radio is capable of fixed modulation and limited data rate but it is software controlled means data handling is done through software. It has the capability to select channel automatically and programmable cryptography of data. d) Software Programmable Radio In this technology, the new features and functions can be added by changing in software module. It has networking capability and multi waveform interoperability [2]. e) Software Defined Radio The complete processing in SDR technology is through software in which functionalities are performed by software modules running on field programmable gate arrays (FPGAs), digital signal processors (DSP), general-purpose processors