End of degree project TELECOMUNICATION ENGINEERING DDVVBB--TT PILOT SENSING ALGORITHMS Linköping University Department of Electrical Engineering, Communication System Division Student: David Cordero Díaz Supervised by Danyo Danev Linköping, June 2010 Kommunikationssystem, ISY. Linköpings universitet. 581 83 LINKÖPING. Tel: 013-28 10 00. Fax: 013-13 92 82 DVB-T pilot sensing algorithms David Cordero Díaz June 2010 Abstract The world nowadays is in the middle of a digital to analog TV transition where digital transmission technology is substituting completely the analog television. This is because digital transmission has many advantages in terms of spectral efficiency, flexibility and robustness which make it especially attractive over analog transmission. Digital Video Broadcasting for Terrestrial (DVB-T) is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television. This system transmits compressed digital audio, video and other data over an MPEG-2 stream, using COFDM modulation. This paper deals with a C++ application currently being developed to simulate a DVB-T transmission in different real channels in order to test several pilot sensing algorithms, compare them and determine in which conditions and scenarios their use is more appropriated. Therefore an emitted DVB-T signal has been generated and detected after crossing a channel. Channel models and detection algorithms have been chosen from existing ones. All the blocs are implemented as specified in the DVB-T standard (ETSI EN 300 744 V1.6.1). Throughout this paper performance of DVB-T is defined and all the technical details needed to understand the application are explained. The application developed and its functions are described. Finally, the obtained results are evaluated and discussed. 2 DVB-T pilot sensing algorithms David Cordero Díaz June 2010 Contents List of figures ................................................................................................................ 5 List of tables ................................................................................................................. 7 Symbols ........................................................................................................................ 8 Abbreviations ............................................................................................................... 9 References .................................................................................................................... 11 Chapter 1.Introduction ................................................................................................. 12 1.1. What is DVB-T?..................................................................................................................... 12 1.2. Why DVB-T should be studied? ............................................................................................ 12 1.3. Overview of Digital TV Broadcasting .................................................................................... 13 1.4. Project organization ............................................................................................................. 14 Chapter 2.DVB-T European Standard ............................................................................. 15 2.1. General consideration ......................................................................................................... 15 2.2. Specification of DVB-T ......................................................................................................... 17 2.3. Signal constellation and mapping ....................................................................................... 18 2.4. Concept of OFDM ................................................................................................................ 22 2.4.1. Mathematical Descriptions of OFDM ...................................................................................... 22 2.4.2. Guard Interval and Cyclic Extension ........................................................................................ 22 2.4.3. OFDM frame structure............................................................................................................. 23 2.5. Reference Signals ................................................................................................................ 26 2.5.1. Definition of reference sequence. ........................................................................................... 26 2.5.2. Continual pilot carriers ............................................................................................................ 27 2.5.3. Scattered pilot cells .................................................................................................................. 28 2.5.4. Transmission parameter signaling (TPS) .................................................................................. 29 2.5.4.1. Definition of the TPS ....................................................................................................... 30 2.5.4.2. TPS modulation ............................................................................................................... 31 2.5.4.3. TPS transmission format ................................................................................................. 31 2.5.4.3.1. Initialization .......................................................................................................... 32 2.5.4.3.2. Synchronization .................................................................................................... 32 2.5.4.3.3. TPS length indicator .............................................................................................. 32 2.5.4.3.4. Frame number ...................................................................................................... 33 2.5.4.3.5. Constellation ......................................................................................................... 33 3 DVB-T pilot sensing algorithms David Cordero Díaz June 2010 2.5.4.3.6. Hierarchy information.......................................................................................... 33 2.5.4.3.7. Code rates ............................................................................................................ 34 2.5.4.3.8. Guard intervals..................................................................................................... 34 2.5.4.3.9. Transmission mode .............................................................................................. 35 2.5.4.3.10. Error protection of TPS ...................................................................................... 35 Chapter 3.Channel Model ............................................................................................. 36 Chapter 4.Detection of DVB-T Signals ............................................................................ 39 4.1. Energy Detection (Power detection) ..................................................................................... 40 4.2. Autocorrelation Coefficient Detector ................................................................................... 40 4.3. Cyclic Prefix Based Sliding Correlation .................................................................................. 41 4.4. Detection Based on IFFT of Pilot .......................................................................................... 42 4.4.1. Time Domain Pilot Based Sliding Correlation ........................................................................... 42 4.4.2. Time domain Pilot in Cyclic Prefixes Based Sliding Correlation ................................................ 43 4.5. Threshold ............................................................................................................................. 44 Chapter 5.C++ application ............................................................................................. 45 5.1. Parameters ............................................................................................................................ 45 5.2. Functions ............................................................................................................................... 46 5.3. Performance explanation ...................................................................................................... 47 Chapter 6.Simulation .................................................................................................... 51 6.1. Energy Detector..................................................................................................................... 52 6.2. Autocorrelation Detector ...................................................................................................... 57 6.3. Cyclic Prefix Detector ............................................................................................................ 59 6.4. Pilot Detector ........................................................................................................................ 61 6.5. CP Pilot Detector .................................................................................................................. 63 6.6. All Detectors .......................................................................................................................... 63 Chapter 7.Conclusions .................................................................................................. 66 Appendix A. Detailed explanation of the C++ functions