適用於無線視訊娛樂之多系統融合及節能技術---子計畫四：訊源與通道共同編碼之設計與實作(I)

Abstract

隨著通訊與訊號處理技術的進展，為滿足不斷被提升的資料或影音的傳輸品質， 許多訊源（source）或通道（channel）編碼或天線系統設計的新方法，都陸續被 納入近幾年所制定的無線通訊標準當中。據此，本計畫將針對WLAN IEEE 802.11n 以及WiMAX IEEE 802.16e 所規範的通道編碼，包括主要的64-state Viterbi Decoder、Turbo Decoder、以及選作的LDPC Decoder、BTC Decoder 等提出低功 率晶片設計方案，並將試著實現在總計畫所建構具節能運算概念的多系統融合平 台，eH-II。 此外，在多媒體的應用中，可調性視訊編碼標準（Scalable Video Coding）壓 縮技術近來受到相當廣泛的重視與討論。MPEG-SVC 藉由同時考慮時間可調性 （temporal scalability）、空間可調性（spatial scalability）與訊雜比可調性（SNR scalability）等功能，除了在效能上與H.264 的壓縮標準相當，在有限通道頻寬的 利用方面，有著更高的彈性及效率，非常適合無線通訊與網路傳輸這種變動頻寬 的應用。因此我們針對WLAN 與WiMAX 等寬頻長距離的無線網路技術規範中， 一方面運用反覆解碼（iterative decoding）的概念，將source 解碼器所得知資料 彼此間的相關性，提供給channel 解碼器，當作輸入資料的likelihood ratio，共同 設計source/channel 的編/解編碼器來提升系統整體效能；另方面嘗試地加入錯誤 更正機制（Forword Error Correction，FEC），希望能夠在固定的頻寬條件下，達 到穩定且不受干擾的影像品質，也就是在MPEG-SVC 相關應用上提出更具效益 的錯誤更正碼（如Block erasure code、Fountain code 等），在bit-rate 與PSNR 上 作最佳化之取捨。

Due to the progress in signal processing techniques, many advance source encoding, channel encoding, and antenna systems have been adopted in the latest wireless communication standards. However, challenges on implementing these new schemes still remain. Therefore, this proposal will firstly focus on the low-power designs for channel decoder, including 64-state Viterbi decoder, turbo decoder, LDPC decoder, and BTC decoder in both WLAN IEEE 802.11n and WiMAX IEEE 802.16e systems. Moreover, we will also integrate our solutions into the newly developed multi-system merging platform, eH-II. For the new source coding schemes, the SVC (scalable video coding) techniques have been drawn much attention recently. According to the spatial scalability, temporal scalability, and SNR scalability, the MPEG-SVC standard not only has approached the performance similar to H.264 now, it also has better efficiency and flexibility that make it very suitable for communication systems with varying available bandwidths. Therefore, the iterative decoding scheme is proposed to both WLAN and WiMAX systems. By iteratively exchanging information between the source decoder and the channel decoder, the system performance can be improved by the proposed joint source/channel decoder. Furthermore, additional forward error correction (FEC) schemes such as block erasure codes and fountain codes will also be combined with the proposed MPEG-SVC system, providing larger coding gain and tradeoff when optimizing the data rate and PSNR.