Hierarchical MIMO modulation in digital TV transmission

OF THE MASTER’S THESIS Author: Gao Liang Title: Hierarchical MIMO modulation in digital TV transmission Date: September 2009 Number of pages: 76 Faculty: Electronics, Communications and Automation Professorship: S-72 Communications Engineering Supervisor: Professor Olav Tirkkonen It is possible to use hierarchical modulation in broadcast systems so that there are two different levels of service with different coverage patterns. There is a basic reception quality, which should be available to almost all users in the system, and there is a higher reception quality which should be available for most users in the system. The higher quality is realized by combining the basic signal with an incremental signal. For this, the basic part of the signal should be more robustly encoded than the incremental part. The fundamental tradeoff in hierarchical modulation is between the coverage of the basic signal and the coverage of the incremental signal. Independently of the method used to multiplex the basic and incremental signals, the presence of the incremental signal takes resources from the basic signal or causes interference. Thus the larger the coverage of the incremental signal is, the smaller the coverage of the basic signal becomes. Most digital broadcast standards (DVB-T, DVB-H, LTE MBMS) are based on orthogonal frequency division multiplexing (OFDM) and single-frequency network (SFN) operation. In this thesis, hierarchical modulation for single-antenna transmission is studied from technical point of view, based on a SFN environment, where time division multiplexing (TDM), superposition, hierarchical quadrature amplitude modulation (QAM) and hierarchical multiple-input and multiple-output (MIMO) scheme are illustrated. The alternatives for hierarchical multi-antenna modulation are investigated. The fundamental tradeoff of different hierarchical broadcasting methods are evaluated in MATLAB. This thesis mainly focuses on the progress of hierarchical broadcasting methods and possible improvements that could be made. The aim of this thesis is to improve current digital broadcasting methods by introducing multiple antennas to both transmitter and receiver.