International Journal of Soft Computing and Engineering (IJSCE) ISSN: 2231-2307, Volume-1 Issue-5, November 2011 259 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: E0215101511/2011©BEIESP Abstract— In this paper one of the most important cognitive radio task i.e. spectrum sensing is explained in detail. Cognitive radio is an intelligent wireless communication technology in order to increase the spectrum efficiency. Increasing efficiency of the spectrum usage is an urgent need as an intrinsic result of the increasing demand for higher data rates, better quality of services and higher capacity. There are several spectrum sensing techniques proposed in literature for cognitive radio based systems like Non cooperative and cooperative spectrum sensing. But there are some practical challenges and limitations in these techniques. So this paper provides the idea behind the MIMO concept in cognitive radio where multiple antennas can be placed both on primary user and secondary user and results evaluate the performance of its implementation. With the emergence of MIMO system, multipath were effectively converted into benefit for communication system. The probability of detection increases and the probability of false alarm decreases as given below in the simulation section. Index terms: Cognitive Radio, Spectrum hole, Spectrum Sensing, MIMO, Cooperative I. INTRODUCTION Primary users are licensed users having higher priority on the usage of part of spectrum and secondary users are unlicensed users. Cognitive radio is a promising solution to this spectrum underutilization problem. Federal Communication Commission (FCC) has issued a Notice of Proposed Rulemaking regarding cognitive radio that requires rethinking of the wireless communication architecture so that emerging radios can share spectrum with primary users without causing interference to them [1]. The term cognitive radio is coined by Dr Joseph Mitola in his doctoral thesis [2]. The word “Cognition” means the mental process of acquiring knowledge through thought, experience and the senses. Cognitive radio enables the users to determine portion of the spectrum available and detect the presence of licensed users when a user operates in licensed bands. There are four main cognitive tasks: spectrum sensing, spectrum management, spectrum mobility and spectrum sharing. Spectrum sensing aims to determine spectrum availability and the presence of the licensed users. Spectrum management is to Manuscript received October 19, 2011. Suman Rathi, Research Scholar, Department of Electronics & Communication, JNU, Jaipur, Jaipur, Rajasthan, India, (E-mail: diyasuman.rathi@gmail.com). Prof. Rajeshwar Lal Dua, Professor, Department of Electronics & Communication, JNU, Jaipur, Jaipur, Rajasthan, India, (E-mail: rndua43@gmail.com) Parmender Singh, Assistant Professor, Department of Electronics & Communication, GITM, Gurgaon, Haryana, India, (E-mail: parmender1979@yahoo.com. predict how long the spectrum holes are likely to remain available for use to the unlicensed users (also called cognitive radio users or secondary users). Spectrum sharing is to distribute the spectrum holes fairly among the secondary users bearing in mind usage cost. Spectrum mobility is to maintain seamless communication requirements during the transition to better spectrum. Spectrum sensing is key element in cognitive radio communication. It enables cognitive radio to adapt to its environment by detecting spectrum holes. A spectrum hole (also known as white space) is a band of frequencies licensed to a primary user but at a particular time and specific geographical location that particular band is not utilized by that user. Several spectrum sensing methods are proposed in literature among them we will focus on few like matched filtering, energy Detector, Periodogram, Welch’s, cooperative and multiple antenna spectrum sensing methods. In this paper we evaluate the results about spectrum sensing using MIMO technique in which multiple antennas are implemented at both transmitter and receiver side. II. ARCHITECHTURE OF COGNITIVE RADIO TRANCEIVER Fig. 1.1 Cognitive Radio Transceiver architecture The wideband signals are received through the RF front end and then are sampled using the high speed analog-to-digital (A/D) converter and furthermore different measurements are done for detection of licensed user signal. But in real applications, RF antenna receives signal from various transmitters operating at different power levels, bandwidths and locations which makes it hard to detect weak signals in that kind of range. So there should be multi-GHz speed A/D converter with high resolution but it is practically infeasible to implement.. Another approach can be the usage of multiple antennas. Spectrum Sensing in Cognitive Radio using Mimo Technique Suman Rathi, Rajeshwar Lal Dua, Parmender Singh