單輸入多輸出之正交分頻多工系統中載波頻率位移與實虛部非協調之盲估測

Abstract

近日由於成本上的優勢，直接轉換射頻接收器變得流行，然而使用直接轉換射頻接收器的正交分頻多工系統對接收器的前端的非理想效應非常敏感，例如：載波頻率位移和實虛部非協調，非理想效應會造成載波間干擾，在正交分頻多工系統仍需估計通道響應，所以準確的估計非理想效應參數及通道響應非常重要，故這篇論文是在單輸入多輸出的正交分頻多工系統中估計載波頻率位移、實虛部非協調和通道響應，包含三種盲估測方法。第一個方法是最小平方法，原先由許等人提出估計通道響應的方法延伸使之可以估計實虛部非協調參數。第二個方法是閉型方法，由張等人所提出的估計載波頻率位移參數的方法，將此延伸可以同時估計載波頻率位移和實虛部非協調參數。第三個方法是所謂的一步法可同時估計載波頻率位移和通道響應，我們將之延伸使得可同時估計載波頻率位移、實虛部非協調和通道響應。此論文提供數值模擬以驗證該方法的性能。

Nowadays, direct-conversion radio frequency (RF) receivers become more appealing due to its cost advantage. However, orthogonal frequency division multiplexing (OFDM) systems with direct-conversion RF receivers are very sensitive to non-idealities at the front-end of receiver, such as carrier frequency offset (CFO) and inphase/quadrature-phase (I/Q) imbalance. These non-idealities at the receiver result in inter-carrier interference (ICI). Accurate estimates of the non-idealities and channel response are required in OFDM systems. This thesis studies CFO, I/Q imbalance, and channel estimation for OFDM systems with multiple transmit antennas. The thesis consists of three different blind estimation methods. The first one is least-square method. However, the original least-square method proposed by Xu etal. can only estimate channels. We improve it and make it able to estimate both I/Q imbalance and channels. The second one is a closed-form method for CFO estimation proposed by Zhang etal. In this thesis, we extend the closed-from method for joint CFO and I/Q imbalance estimation. The third one is the so-called one-shot method for CFO and channel estimation. We extend this method for joint CFO, I/Q imbalance, channel estimation. In this thesis numerical simulations are also provided to verify the performances of the proposed methods.