臺灣博碩士論文加值系統

由於無線數據通訊的蓬勃發展，無線區域網路也因著其高速傳輸的特性因應而生，本篇論文將著重於設計一組符合IEEE 802.11a標準的基頻傳送接收機制。由於實體層的調變技術乃使用正交分頻多工，所以其傳統上會發生的問題，諸如時脈與載波的同步、過大峰對均值的克服等技術都將被分析與解決。從工作站SPW模擬的成果證明使用個人所設計的同步機制不但在白色高斯雜訊的通道下有不錯的性能曲線，而且在無線的多路徑衰退通道下的封包及位元錯誤率也能符合期盼。

除了分析與模擬外，硬體實現是最後的重頭戲，為了考驗所設計的同步演算法在即時的通訊環境也能正常運作，採用德州儀器公司所生產的數位訊號處理器TMS320C6711配合週邊電路完成了一對傳送接收之雛型數據機。可以想像這比分析模擬更具有挑戰性!

Owing to the rapidly development of wireless data communication, wireless LAN with its high speed transmission is also proposed, then this thesis focuses on the design of a baseband transceiver conforming with the IEEE 802.11a standard. Due to the using of Orthogonal Frequency Division Multiplexing on physical layer, some traditional issues such as the recovery of timing clock and carrier frequency, immoderate peak to average power ratio will be analyzed and solve. From the simulation results of SPW, the synchronization solutions one designs not only have superior performance on AWGN channel, but also its PER and BER could be expected on wireless multipath fading channel.

In addition to analysis and simulation, hardware implementation is the last emphasis. For testing the designed synchronization algorithm could well work at real time communication environment, one adopt the TI TMS320C6711 and some peripheral circuits to complete an embryo modem. These give more challenge than simulation!

Abstract i
Contents ii
List of Tables iv
List of Figures v

Chapter Page

Chapter 1 Introducation ..............1
1.1 Overview of Wireless Local Area Networks…………………1
1.2 Applications for OFDM …………………………………………3
1.3 the Outlines………………………………………………………5

Chapter 2 System Description for Wireless LAN ..........7
2.1 OFDM Principles …………………………………………………7
2.1.1 OFDM Modulation ………………………………………………7
2.1.2 Guard Time and Cyclic Prefix………………………………9
2.2 IEEE 802.11a Specification……………………………………13
2.2.1 Basic Parameters………………………………………………13
2.2.2 Frame Formats …………………………………………………14
2.2.3 Channelization…………………………………………………16
2.3 Wireless Channel Environment…………………………………18
2.3.1 Fading and Multipath Propagation…………………………18
2.3.2 Indoor Radio Channel Model…………………………………22

Chapter 3 Synchronization Analysis for OFDM ............25
3.1 Synchronization Issues for OFDM ……………………………25
3.1.1 Effects of Phase Noise………………………………………26
3.1.2 Effects of Carrier Frequency Offset ……………………27
3.1.3 Effects of Timing Errors……………………………………29
3.1.4 Integrated Effects of Synchronization Issues…………31
3.2 Synchronization Methods for OFDM……………………………35
3.2.1 Using Cyclic Prefix …………………………………………36
3.2.2 Using Training Sequences……………………………………38
3.2.3 Using Pilots on Each OFDM Symbol…………………………40
Chapter 4 Transceiver Design of IEEE 802.11a on Baseband........45
4.1 Design of the Indoor Wireless Channel ……………………45
4.2 System Design of the Transmitter……………………………48
4.3 System Design of the Receiver ………………………………48
4.2.1 Packet Detection………………………………………………49
4.2.2 Carrier Frequency Offset Acquisition……………………50
4.2.3 Symbol Timing Decision………………………………………53
4.2.4 Channel Estimation……………………………………………55
4.2.5 Synchronization Tracking……………………………………59
4.2.6 Simulation Results……………………………………………66

Chapter 5 Firmware Design and Implementation
5.1 Introduction to TMS320C6711 DSP ……………………………71
5.1.1 General Description …………………………………………72
5.1.2 Key Features……………………………………………………74
5.1.3 Timer and Interrupt …………………………………………76
5.2 Hardware Architecture of OFDM Modem ………………………78
5.3 Program Structure of OFDM Modem ……………………………84

Chapter 6 Conclusions and Future Work
6.1 Conclusions ………………………………………………………87
6.2 Future work ………………………………………………………88

Bibliography……………………………………………………………91

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