View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by ethesis@nitr RESOURCE ALLOCATION FOR OFDM-BASED COGNITIVE RADIO SYSTEMS A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Technology In Telematics and Signal Processing By VENKATA RAMA REDDY M Roll No: 209EC1110 Department of Electronics & Communication Engineering National Institute of Technology Rourkela 2011 RESOURCE ALLOCATION FOR OFDM-BASED COGNITIVE RADIO SYSTEMS A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Technology In Telematics and Signal Processing By VENKATA RAMA REDDY M Roll No: 209EC1110 Under the guidance of Prof. Poonam Singh Department of Electronics & Communication Engineering National Institute of Technology Rourkela 2011 Dedicated to, Shiva keshava National Institute Of Technology Rourkela CERTIFICATE This is to certify that the thesis entitled, “RESOURCE ALLOCATION FOR OFDM- BASED COGNITIVE RADIO SYSTEMS‖ submitted by VENKATA RAMA REDDY M (209EC1110) in partial fulfillment of the requirements for the award of Master of Technology degree in Electronics and Communication Engineering with specialization in ―Telematics and Signal Processing‖ during session 2010-2011 at National Institute of Technology, Rourkela (Deemed University) is an authentic work carried out by her under my supervision and guidance. To the best of my knowledge, the matter embodied in the thesis has not been submitted to any other university/institute for the award of any Degree or Diploma. Prof. Poonam Singh DATE: Department of Electronics and Communication National Institute of Technology, Rourkela- 769008. i Acknowledgment First of all, I would like to express my sincere respect and gratitude towards my guide Prof. Poonam Singh. I thank her for giving me an opportunity to work under her. I am very much thankful for the support she extended to me and the freedom to express my views. I am thankful to Prof.S.K.Patra, Head, Department of Electronics &Communication Engineering who provided all the official facilities to me. I express my respects to all my teachers Prof.G.S.Rath,Prof.K.K.Mohapatra, Prof.S.Meher,Prof.D.P.Acharya,Prof.S.K.Behera,Prof.Ajit Kumar Sahoo and Prof.S.K.Das for teaching me and also helping me how to learn. They have been great sources of inspiration to me and I thank them from the bottom of my heart. I would like to thank all faculty members and staff of the Department of Electronics and Communication Engineering, N.I.T. Rourkela for their generous help in various ways for the completion of this thesis. I would like to finally thank my best in Institute is Prof.N.V.L.N. Murthy, Prof.Samit Ari, given me the direction way in a critical decision making and great support. VENKATA RAMA REDDY M ii Abstract Cognitive Radio (CR) is a novel concept for improving the utilization of the radio spectrum. It is a software controlled radio that senses the unused frequency spectrum at any time from the wide but congested wireless radio spectrum. This promises the efficient use of scarce radio resources. Orthogonal Frequency Division Multiplexing (OFDM) is a reliable transmission scheme for Cognitive Radio Systems [3] which provides flexibility in allocating the radio resources in dynamic environment. It also assures no mutual interference among the CR radio channels which are just adjacent to each other, making it one of the best schemes to be used in CR systems. Allocation of radio resources is a major challenge in cognitive radio systems. In a dynamic environment, many parameters and situations have to be considered which affect the total data rate of the system. A Secondary users (CRUs/SUs) may coexist with the Primary user (PU) either on Conservative basis or on a more aggressive basis which allows secondary transmissions as long as the induced interference to the PU is below acceptable level. In this we have considered Uplink cognitive radio system heaving one PU coexists with M SUs and A Downlink of an Multi User Orthogonal Frequency Division Multiplexing CR system with one base station (BS) serving one PU and K SUs. We focused on the design on the design and analysis of subcarrier and power allocation scheme under imperfect CSI for cognitive OFDM systems. A two – step Algorithm for bit rate is proposed to obtain the (1) subcarrier allocation to secondary users and (2) bits, power allocation on subcarriers. The algorithms attempt to maximize the total throughput of the CR system (secondary users) subject to the total power constraint of the CR system and tolerable interference from and to the licensed band (primary users). iii Contents CERTIFICATE .................................................................................................................................................. i Acknowledgment .............................................................................................................................................. ii Abstract ............................................................................................................................................................. iii List of Figures .................................................................................................................................................... vi Acronyms and abbreviations ....................................................................................................................... vii Chapter1 .............................................................................................................................................................. 1 INTRODUCTION ............................................................................................................................................. 1 1.1. Cognitive Radio: ................................................................................................................... 2 1.2. Cognitive Radio Features: ................................................................................................... 2 1.3. OFDM For Cognitive Radio: ............................................................................................... 3 1.4. Motivation: ............................................................................................................................ 4 1.5. Thesis Outline: ...................................................................................................................... 5 Chapter 2 ............................................................................................................................................................. 6 LITERATURE SURVEY ................................................................................................................................ 6 2.1. Introduction: .................................................................................................................. 7 2.2. Term Cognition: ............................................................................................................. 8 2.3. Why Cognitive Radio? ................................................................................................... 9 2.4. When Will Cognitive Radio Happen? ..............................................................................10 2.5. Back Ground Study: ...................................................................................................10 2.6. Cognitive Radio Hardware Design Challenges: .............................................................13 2.7. Possible Application: .....................................................................................................14 2.8. Spectrum Sensing in Cognitive Radio Networks: ..........................................................15 2.9. Spectrum Sharing in Cognitive Radio Systems: .........................................................17 Chapter 3 .......................................................................................................................................................... 18 COGNITIVE OFDM SYSTEMS UNDER IMPERFECT CSI WITH SMART CHANNEL ESTIMATION ................................................................................................................................................ 18 3.1. Introduction: ..............................................................................................................19 3.2. System Model and Problem: .......................................................................................20 3.2.1. System model: .....................................................................................................20 3.2.2. Problem Formulation: .........................................................................................21 3.3. Training Preamble Assisted Channel Estimation: ...........................................................22 3.4. Proposed Allocation Scheme: .......................................................................................23 iv 3.4.1. Greedy Subcarrier Allocation: ...............................................................................24 3.4.2. Fast Iterative Water-Filling: ...............................................................................24 3.5. Complexity Analysis: ..................................................................................................26 3.6. Simulation and Results: ..............................................................................................26 Chapter 4 .........................................................................................................................................................