分時複接數位行動電話之等化器設計

Abstract

電話通訊中，信號可能會受到建築物或其他地形障礙的影響，而有多重路 徑衰減的情形．因此，在接收端，需要有等化器來消除這種干擾．我們發 展了一套ｃ語言程式來模擬北美ＩＳ－５４數位行動電話系統，以輔助等 化器設計．我們研究一種雙方向等化技術．實驗結果顯示它可以解決傳統 等化器不易收歛的問題．我們模擬了等化器在各種條件下的效能．我們也 對等化器做了精確度的模擬，以作為硬體實現的基礎；同時也以高階的電 路模擬來証驗結果．最後，我們提出了一個低複雜度的等化器．它採用一 個重複訓練的架構來克服ＬＭＳ ＤＦＥ收歛速度太慢的問題． In the TDMA cellular mobile communication, the received signal may suffer from multipath fading due to the reflections of buildings or terrain. An equalizer is needed to cancel the intersymbol interference. We develop a C-language program to simulate the North American IS-54 digital mobile system for the equalizer design. A bi-directional equalization technique is studied. The simulation result shows that it can solve the divergence problem of the conventional DFE (Decision Feedback Equalizer). We investigate the performance of the bi- directional QRD-RLS DFE under different SNR, vehicle speed, and delay spread. The finite-precision simulation results of the QRD-RLS DFE are also discussed. A behavioral level circuit simulation in Verilog HDL is accomplished as a verification. Finally, we propose a low-complexity equalizer, which adopts the LMS algorithm for tap-weight updating. A "multiple training" scheme is used to overcome the bottleneck of slow convergence of the LMS DFE.