System Design of Baseband Receiver for the DVB-H Standard

本論文提出一個數位電視廣播DVB-H (Digital Video Broadcasting – Handheld) 系統的基頻接收機。信號的格式是根據ETSI EN 302 304中訂定的規格所設計。我們希望此接收機除了可以在室內和室外進行靜態接收外，亦能在高速移動的環境下進行動態接收。然而手持裝置的外型必須夠小、夠輕巧，所以採用多根天線改進動態接收效能的方式是不太可行的。 在本研究中，我們提出了一個新的方法，只需使用單根天線的架構，便能對都卜勒效應進行有效的補償，進而改進其行動接收的效能，從我們的模擬結果中可知，假設傳送信號的中心頻率約為550 MHz，即使移動的速度達到時速110 Km，仍有不錯的接收效果。另外，在時間同步、通道估測及頻率漂移補償等問題上亦提出了一些新的演算法，以提高整個系統的接收效能。 最後，我們在Simulink的模擬環境下，建立了一套完整的DVB-H基頻接收機，模擬結果顯示我們所設計之接收機的表現令人滿意。We investigate a DVB-H (Digital Video Broadcasting – Handheld) baseband receiver in the thesis. The architecture is based on the DVB-H standard which is published by ETSI (European Telecommunication Standard Institute). Mobility is an important requirement, meaning that access to services should be possible not only at almost all indoor and outdoor locations but also while moving in a vehicle at high speed. However, the situation is worsened by the fact that a multi-antenna diversity approach is almost impossible because of space limitations. In this work, we propose a new algorithm which only uses a single antenna to compensate for the Doppler effect. When the carrier frequency of the transmitted signal is about 550 MHz, the tolerable maximal speed is about 110 Km/h. The method has much better performance than the conventional algorithm. In addition, we also propose some new algorithms to improve the performance of symbol timing synchronization, carrier frequency offset estimation and channel estimation. Finally, we make simulation in Simulink environment to demonstrate that the receiver we design indeed works well.Chapter 1 Introducation 1 1.1 Motivation 1 1.2 Thesis organization 2 Chapter 2 DVB-H Fundamentals 3 2.1 Overview 3 2.2 OFDM basics 4 2.2.1 OFDM model 6 2.2.2 Guard interval and cyclic prefix 9 2.3 New technological elements in DVB-H 10 2.3.1 Link layer elements 11 2.3.2 Physical layer elements 13 2.4 DVB-H compatibility issues 16 Chapter 3 DVB-H Transmitter Model and Frame Structure 17 3.1 Modes of operation 17 3.2 Hierarchical modulation 19 3.3 Frame structure 23 3.4 Reference signals 24 3.5 Transmitter system architecture 30 3.5.1 Transport multiplexer and scrambler 31 3.5.2 Outer coding 32 3.5.3 Outer interleaving 34 3.5.4 Inner coding 35 3.5.5 Inner interleaving 38 3.5.5.1 Bit-wise interleaving 38 3.5.5.2 Symbol interleaving 42 3.5.6 Signal constellation and mapping 48 Chapter 4 Wireless Channel Model 51 4.1 Channel characteristics 51 4.1.1 Path loss 52 4.1.2 Shadowing 54 4.1.3 Multi-path fading 55 4.1.3.1 Frequency selective fading 56 4.1.3.2 Delay spread 57 4.1.4 Doppler shift 58 4.2 Mathematical model of multi-path channels 60 4.3 Channel parameters 61 4.4 Typical channel models 64 4.5 Channel models for DVB-H simulation 66 4.5.1 Channel profiles for simulation without Doppler shift 66 4.5.2 Profiles for realtime simulation without Doppler shift 68 4.5.3 Profiles for realtime simulation with Doppler shift 69 4.5.4 The COST 259 channel models 71 Chapter 5 DVB-H Baseband Receiver Design and Model 75 5.1 Symbol timing synchronization 76 5.1.1 Effect of the timing offset 76 5.1.2 Timing synchronization techniques 79 5.1.2.1 Timing synchronization with continual pilots 80 5.1.2.2 Timing synchronization with guard interval 82 5.2 Carrier frequency offset estimation 85 5.2.1 Mathematical model of CFO 86 5.2.2 Fractional CFO estimation 89 5.2.3 Integer CFO estimation 91 5.3 Channel estimation without Doppler frequency 95 5.3.1 One-dimensional channel estimation 96 5.3.2 Two-dimensional channel estimation 102 5.4 Doppler effect compensation 106 5.5 Demapper 109 5.6 Inner deinterleaver 112 5.6.1 Symbol deinterleaver 112 5.6.2 Bit deinterleaver 113 5.7 Inner decoder 114 5.8 Outer deinterleaver 116 5.9 Reed-Solomon decoder 117 Chapter 6 Simulations Results 119 6.1 Simulation parameters 119 6.2 Simulation of timing synchronization 120 6.3 Simulation of fractional CFO estimation 124 6.4 Simulation of integer CFO estimation 130 6.5 Simulation of channel estimation 131 6.6 Simulation of Doppler effect compensation 136 Chapter 7 Conclusion and Future Work 149 References 15