International Journal of Computer Applications (0975 – 8887) Volume 74– No.10, July 2013 1 Cognitive Radio: State of Research Domain in Next Generation Wireless Networks - A Critical Analysis Jai Sukh Paul 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 Cognitive Radio (CR) is a comparatively new technology in which problems like underutilization of spectrum and spectrum scarcity is solved based on the revolutionary ideas. Cognitive Radio allows group of users to identify and access to available spectrum resources for their optimum use. Recent studies show that most of the assigned spectrum is underutilized. On the other hand, the increasing number of wireless multimedia applications leads to a spectrum scarcity. Cognitive Radio is proposed as a promising technology to solve the imbalance between spectrum scarcity and spectrum underutilization. In Cognitive Radio, spectrum sensing is done in order to locate the unused spectrum segments. This paper show the strength and capabilities of Cognitive Radio processes and what makes it more powerful over the other competitive radio. Main focus is given on Present State of Research, Architecture and Future Scope for CR. Stress is given on Application areas, where Cognitive Radio techniques can be implemented and proved out to have upper-hand than the available Intelligence and adapting Radios. Keywords Cognitive Radio, Software Defined Radio, Cognitive Cycle, Spectrum Sensing, Dynamic Spectrum Management, Spectrum Sharing, Spectrum Mobility, Primary User, Secondary User, Cognitive User. 1. INTRODUCTION The aim of the Cognitive Radio technology is to provide the maximum efficiency of the spectrum to improve its utilization by using dynamic spectrum access techniques. The key to enable the maximum spectrum efficiency is to provide the capability to share the wireless channel with licensed users in the most efficient manner and this goal can be achieved by using spectrum management techniques that are dynamic and efficient. Cognitive radios are fully programmable wireless devices that can sense their environment and dynamically adapt their channel access methods, transmission waveform, spectrum utilization and networking protocols as needed for good network and application performance [2].The interesting feature of cognitive radio technology is one in which handsets would automatically use underutilized spectrum. Smartness of a radio is when it utilizes the available service from locally accessible wireless computer networks, and interacts with networks of preferred protocols, without any confusion in finding out the appropriate wireless network for audio video or data [3].Moreover, frequencies selection and utilization minimize/avoid interference with existing radio systems. 1.1 Radios in Software Defined To exactly understand what basically Cognitive Radio is we have to start with Software Defined Radio (SDR), which is known to be the base platform for Cognitive Radio. Cognitive radios is a radio application that sit on top of an SDR, which as described before is implemented largely from General Purpose Processors (GPP’s) and Digital Signal Processors (DSP’s) [3]. Communication devices like the traditional radio system supports fixed number of channels and multiple frequencies but the problem is that channel and frequency must be chosen at the time of design and not at a later stage because there is no mechanism to bring about any post-design adjustment at the time of and as per actual requirement. In search of a better solution to this problem, a comparatively new concept called Software Defined Radio (SDR) was introduced. It was designed based on the idea of the traditional radio system but with a little change to its design. In SDR radio’s physical layer behavior and functionalities are defined in software. In SDR different components of the radio communication system like amplifier and filters have been implemented in software instructions rather than the hardware [4]. Software Defined Radio = Traditional Radio + Software defined functionality Basically Software Defined Radio is defined [3] as “Radio in which entire or some of the physical layer functions are software defined”. Software-Defined Radio (SDR) is a technology where software modules running on a generic hardware platform consisting of General Purpose Processors (GPP’s) and Digital Signal Processor (DSP’s) are used for the implementation of radio functions like Modulation at transmitter and Demodulation (detection/tuning) at receiver. Traditional radio’s (hardware based radios) limits cross- functionality and any modification can be done only using physical intervention which results in higher production costs. So, Software Defined Radio (SDR) as emerged out as an efficient and comparatively inexpensive solution to the above defined problem, using software upgrades. SDR can be used in implementation of applications like Bluetooth, Radar, GPRS, GPS, WLAN, Radar, WCDMA, etc. [3]. 1.2 Role of SDR in Wireless Communication Commercial Wireless network standards are continuously evolving from 2G to 2.5G/3 to 4G and now towards 5G. This difference in networks of each generation, which significantly is the difference between Data-Link layer protocol standards causes problem to subscribes, wireless network operators and equipment manufacturers. With the coming of new generation subscribers are forced to update themselves to new handsets to take the advantage of upcoming services. Wireless network operators face problems with the problem of migration of the network from one generation to the next as majority of the subscriber’s uses legacy handsets which are incompatible with newer generation network. So to overcome this network