Dynamic Channel Selection in Cognitive Radio for OFDM System

In this paper, we integrate overlay cognitive radio technology into 4G cellular networks for the sharing of TV spectrum. On one hand, OFDM is a promising technique for high-speed data transmission over multipath fading channels and has been considered to be the best candidate for 4G mobile networks. On another hand, the overlay cognitive radio model makes it possible to have two concurrent transmissions in a given interference region, where conventionally only one communication takes place at a given time. We investigate different service provision scenarios and propose both time domain and frequency domain overlay cognitive radio OFDM systems for next generation cellular networks. Numerical results show our proposedschemescan achieve satisfying performance in different use cases. Thus highly reliable cognitive radio scheme for OFDM based wireless communication proposed with increasing the spectral efficiency by two concurrent transmissions in a region and thesecondary users throughput is improved. Index Terms – Cognitive Radio,DTV,Frequency domain overlay CR, OFDM systems, Primary user,Spectrum Sharing, Time domainoverlay CR 1.INTRODUCTION 1.1Cognitive Radio Cognitive radio (CR) technology is the key technology that enables an 4G network to use spectrum in a dynamic manner.Automatically detects available channels in wireless spectrum.. The term, cognitive radio, can formally be defined as follows Cognitive capability Cognitive capability refers to the ability of the radio technology to capture or sense the information from its radio environment. This capability cannot simply be realized by monitoring the power in some frequency band of interest but more sophisticated techniques are required in order to capture the temporal and spatial variations in the radio environment and avoid interference to other users. Consequently, the best spectrum and appropriate operating parameters can be selected. Reconfigurability The cognitive capability provides spectrum awareness whereas reconfigurability enables the radio to be dynamically programmed according to the radio environment. More specifically,the cognitive radio can be programmed to transmit and receive on a variety of frequencies and to use different transmission access technologies supported by its hardware design. 2.WORKING OF MY PROJECT 2.1 Cognitive Radio Technology Joseph Mitola defined CR as an intelligent wireless communication system that aware and learns from its environment and adapts its internal states by makingcorresponding changes in certain operating parameters. The vital objective of the cognitive radio is to achieve the best accessible spectrum through cognitive capability and reconfigurability. In other words, CR is also defined as awareness, intelligence, learning, adaptively, reliability and efficiency. Cognitive cycle consists of three major steps as follows. 1. Sensing of RF stimuli. • Detection of spectrum holes. • Estimation of channel state information. • Prediction of channel capacity for use by the transmitter. 2. Cognition/spectrum management. • Spectrum management, which controls opportunistic spectrum access. • Optimal transmission rate control. • Traffic shaping. • Routing. 3. Quality of service provision. 2.2.Transmit Power Control Asmentioned earlier, among the challenges in CR is spectrum sharing. CR allows the usage of temporally vacant spectrum, which is referred to as white space or spectrum hole. If a licensed user further uses this band, CR node need to move to another spectrum hole or stays in the same band, altering its ———————————————— • P.Perumal is currently pursuing masters degree program in Electronics and Communication Engineering in Valliammai Engineering college, India. E-mail: [email protected] • Dr.M.Murugan is the Professor of Electronics and Communication Engineering in Valliammai Engineering College, India. E-mail: [email protected] IJSER International Journal of Scientific & Engineering Research, Volume 5, Issue 4, April-2014 209