| 摘要: | 迴旋渦輪碼(Convolutional Turbo Code , CTC)是由傳統的渦輪碼演進而來，目前已在WiMAX、DVB等通訊技術中被應用，CTC採用雙二進制循環遞迴系統迴旋(CRSC)，與相同碼塊的渦輪碼相比，CTC擁有更佳的錯誤率，且利用編碼器的循環狀態特性，不需像傳統渦輪碼要多傳一些讓狀態歸零的位元，其解碼部分一般多使用事後機率(MAP)、對數事後機率(log-MAP)、最大對數事後機率(MAX log-MAP)，在本文則採用最大對數事後機率。合作式通訊方面，一般有放大轉送(AF)和解碼轉送(DF)，而解碼放大轉送(DAF)也於近年被提了出來，DAF在中繼站解碼，但並不判斷位元，也不重新編碼。由於CTC是雙二進制的，解碼判斷時也一次判斷兩個位元，為了將CTC應用於DAF上，本論文在中繼站解碼後將雙位元判斷轉換成單位元判斷，成功將DAF應用於CTC上，最後再將DAF與DF合併使用，成為混和解碼轉送(HF)，而從模擬結果也顯示使用DAF和HF的效能大大優於傳統的AF。Convolution Turbo Code(CTC) is comes by the traditional turbo code evolution, at present in communication technologies and so on the WiMAX, DVB has been applied, CTC uses the duobinary cycle recursive system convolution (CRSC), compares with the same code block turbo code, CTC has a better performance. It’s different from the traditional turbo code, CTC Base on the cyclic state characteristic of encoder, does not have to transmit another bits which is used to return the state to zero. Besides, It’s decoding general using maximum a posteriori probability (MAP) algorithm, logarithm maximum a posteriori (log-MAP) algorithm, and maximum log-MAP probability (MAX log-MAP). In this thesis, we uses MAX log-MAP for decoding.The cooperative communication aspect, the mobile relays generally consist of decode and forward (DF) or amplify and forward (AF) .However, the decode- amplify –and- forward (DAF) has been proposed for recent years. DAF decoded the signal in relay station , but did not determine the bit and re-encoding .Because CTC is the doubinary system, when decoding determine begin it also determine two bit at one time.In order to applies CTC on DAF, we change the double bit determent into single bit determent after the relay station decoding ,in this way we succeeds applies CTC on DAF. Finally we again DAF and the DF merge use, becomes the Hybrid-and-Forward mode (HF). By simulation result, we can also demonstrated that using DAF and the HF have significant better performance than the traditional AF. |
