數位歐式無線電話傳輸等化之研究

Abstract

在最近幾年，無線用戶迴路以及無線區域網路愈來愈被廣泛地使用，而數位歐式無線電話雖然是一個適合的系統，但在無線迴路之應用中，因有較大的延遲擴散，故需使用等化器來解決覆蓋範圍的問題。同調檢測器在無頻率偏移或調變指數偏移時表現不錯，但非同調檢測器這些環境下卻仍有不錯的表現。在本篇論文中，我們試圖用非同調檢測器及建構於非同調檢測架構下的等化器來降低無線用戶迴路傳輸之錯誤率而增大其覆蓋範圍。首先，我們研究一些非同調檢測器並將其效能與同調檢測器比較。其次，我們研究通道等化的方法。我們嘗試使用數位歐式無線電話中同步區的訊號序列作為訓練序列，並且使用最小均方差等化器改善非同調檢測器對於錯誤率和延遲範圍的效能。我們也提出一個方法來解決訓練序列長度不夠的問題。模擬結果顯示，在訊擾比為13 dB，標準延遲擴散在0.9訊號時間，限制鑑別積分檢測器加上判斷回饋等化器可使錯誤率降至0.001。

Wireless local loop (WLL) and Wireless local area network (WLAN) is more and more popular used during recent years, and DECT is a suitable system. Because of the larger delay spread, we need to solve the coverage problem by equalizer in wireless local loop applications. Coherent detectors may have better performnace without the variation of frequency offset and modulation index, but noncoherent detectors have good performance in these environments. In this thesis, we try to use noncoherent detectors and build up equalizers under noncoherent detection structures to reduce the BER and enlarge the coverage of a wireless local loop. First, We study some noncoherent detectors and compare their performance with coherent ones. Then, we study the method of equalization. We want to use the S-field sequence in DECT as the training sequence and use MMSE equalizers to improve the performance of BER and delay spread of noncoherent detectors. Because this training sequence is not long enough, we want to provide a technique to solve this problem. Simulation results show that a LDID plus a DFE can reduce the BER to 0.001 when SNR is 13 dB and nomalized delay spread is 0.9 bit. Chapter2 DECT Specifications Chapter3 Transmission System Model and Detector Performance Without Equalization Chapter4 Equalization for DECT Chapter5 Conclusion