Joint Channel Estimation and Interference Cancellation for MC-CDMA Communication Systems

多載波分碼多重存取系統(MC-CDMA)因為容易實現和對頻率選擇性衰減通道有強力的抵抗力，以及CDMA適合多使用者系統的種種優點，所以近年來備受矚目。本篇論文主要是針對上行鏈路多載波分碼多重存取系統在頻率選擇性多重路徑衰減通道下的聯合通道估測與干擾消除技術之研究。所提出的演算法，可分為三個部分，期望步驟(Expectation step)、最大步驟(Maximization step)與初始化(Initialization)。其中期望步驟包含了聯合通道估測和干擾消除技術。最大步驟是執行資料檢測。而初始化則是利用發射端的區塊導引符元(block-type pilot symbol)，執行均方根誤差估測(MMSE estimation)來得到通道資訊，與線性均方根誤差檢測(linear MMSE detection)來得到資料符元，並將其視為所提出演算法的初始值，以改善演算法的收斂速度。所提出的干擾消除技術，不僅能夠處理多重存取干擾(multiple access interference, MAI)，還能夠同時地處理載波間干擾(inter-carrier interference, ICI)。並將參考文獻的接收機和所提出的接收機於COST 207通道模型下比較其位元錯誤率的表現。Multicarrier code division multiple access (MC-CDMA) systems has arrested a lot of attention, owing to the simple implementation and powerful resistance to frequency-selective channels and the CDMA with the suitability for multiuser systems. This paper is concerned with joint channel estimation and interference cancellation for uplink MC-CDMA communication systems in frequency-selective multipath fading channel. The proposed algorithm is consists of three parts: Expectation step, Maximization step and initialization. Expectation step is performs channel estimation and interference cancellation jointly. Maximization step is performs data detection. Initialization is performs the MMSE estimate and the linear MMSE detection by the block-type pilot symbols from transmitter side to obtain the initial value of data symbol, to improve the convergence rate of the proposed algorithm. The proposed interference cancellation scheme not only performs multiple access interference (MAI) cancellation but also performs inter-carrier interference (ICI) cancellation simultaneously. We assessed the BER performance for the proposed receiver and the reference receiver are verified with the COST 207 channel model.Chapter 1 Introduction 1 Chapter 2 Background 6 2.1 CDMA 6 2.2 OFDM 8 2.3 MC-CDMA 11 Chapter 3 System Model 13 3.1 System Description 13 3.2 Initialization 17 Chapter 4 Joint Channel Estimation and Interfernce Cancellation 18 4.1 Expectation Step 23 4.2 Maximization Step 27 Chapter 5 Simulation Results 29 Chapter 6 Conclusions 35 Bibliography 3