臺灣博碩士論文加值系統

此論文中我們探討正交分頻多工系統下、合作式中繼系統之載波間干擾問題。在此系統中，頻率偏移和通道響應在不同中繼點到接收端是統計上獨立的，因而導致載波間的干擾更難處理。實現共軛傳輸在該合作式中繼系統時，我們藉由在各個載波上引入振幅調整值，改進了既有的適應性接收機。該振幅調整值是在考慮多路徑環境下、最小化載波間干擾與雜訊之影響推導而來，不同於之前的推導是基於可加性高斯白雜訊通道、並最小化載波間干擾。對於該適應性接收機之設計，我們還提出了一個該系統架構下的新中繼點選擇機制，此機制根據Max-Min CINR的結果同時考慮頻率偏移和通道的影響，選出兩個中繼點。電腦模擬結果顯示出在誤碼率的比較上，相較先前的架構，我們所提出的接收機設計有較優的效能。

In this thesis, we investigate intercarrier interference (ICI) cancellation for OFDM-based cooperative relay systems using conjugate transmission. First, we modify an existing adaptive receiver for such systems by introducing a new amplitude scaling factor for each subcarrier. The presented amplitude scaling factor is optimized by a carrier-to-interference-plus-noise ratio (CINR) criterion derived under multipath environments, rather than by the carrier-to-interference ratio (CIR) derived under AWGN channels in a previous scheme. With the proposed adaptive receiver, we then develop a relay selection method based on a max-min CINR criterion for OFDM-based cooperative relay systems using conjugate transmission, where the frequency offset and channel state information are jointly considered for relay selection. Computer simulation results demonstrate that the proposed adaptive receiver and the proposed relay selection method outperform previous related schemes in terms of the bit-error-rate performance.

Abstract i
Table of Contents ii
List of Figures iii
List of Tables iv
Chapter 1 Introduction 1
Chapter 2 OFDM-Based Cooperative Relay System 4
2.1 Introduction to ICI 4
2.2 System Description 6
2.3 Problem Formulation 7
Chapter 3 ICI Self-Cancellation Schemes for OFDM Systems 9
3.1 Conjugate Cancellation (CC) [8] 9
3.2 Phase Rotated Conjugate Cancellation (PRCC) [9] 11
3.3 An Adaptive Receiver for Conjugate Transmission [10] 13
3.4 An improved Adaptive Receiver for Conjugate Transmission [11] 16
3.5 An Adaptive Receiver for OFDM-Based Cooperative Relay Systems [12] 20
Chapter 4 Proposed Receiver Design for OFDM-Based Cooperative Relay Systems 28
4.1 Motivation 28
4.2 Optimizations of the Phase Rotations and Amplitude Scaling Factor 29
4.3 Adaptations of the Phase Rotations and the Amplitude Scaling Factor 30
4.4 Selection of Two Relays for Conjugate Transmission 32
4.5 More Selection Criteria 33
Chapter 5 Simulation Results 37
Chapter 6 Conclusions 41
Appendix A Derivation of the New Amplitude Scaling Factor 42
Bibliography 44

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