應用具跨層設計特色之新式低密度位元檢測碼於無線多媒體網路通訊之研究---理論建構與硬體實現

Abstract

隨著個人化通訊需求的迅速發展及多媒體訊息交流的急遽增加，強化無線接取技術 以因應高速、多元及高品質傳輸要求，已成為發展新一代無線通訊系統時所須考量的重 要課題。具有多重輸出、入收發架構之正交分頻多工系統由於可從空間、時域及頻域等 三重維度有效地使用通道資源，已被眾多無線通訊標準選取為內定之傳輸架構。以此類 系統為核心架構，本三年期計畫預計以低密度位元檢測碼為主體，整合可提升多媒體傳 輸品質之非均等錯誤保護技術及可達最佳傳輸效率之混合式自動重傳機制，擷取三者優 點以設計出適合於高速無線多媒體傳輸之高效能通道編碼系統。 在計畫的前兩年中，吾人將針對前述高效能通道編碼系統進行基礎理論之建構。首 先對於正交分頻多工系統獨有之高峰均功率缺陷，本計畫預計結合低密度位元檢測碼與 傳統低峰均功率比之編碼技術，以建造可在多載波系統中兼具高糾錯能力與低峰均功率 比之新型通道編碼系統。所得之新型低峰均功率比-低密度位元檢測碼將與傳統非均等 錯誤保護技術進行整合式設計，進而針對多媒體服務提供最佳之資料保護。此外，在具 網路架構之通訊系統中，通道編碼多搭配混合式自動重傳機制以達實體層與媒體存取控 制層效能之最佳化。從跨層設計的角度出發，吾人亦將設計可搭配混合式自動重傳機制 之新型低密度位元檢測編碼系統，以提升整體系統之使用效率。在計畫的最後一年中， 針對第一、二年計畫所研發之新型編碼系統，我們將從軟體無線電的角度進行兼具高效 率、低複雜度解碼理論之研究及其DSP/FPGA硬體實現。計畫所得結果預期將對理論研究 者與系統工程師提供相當的助益，同時亦能推廣高效能新型低密度位元檢測編碼技術於 未來蜂巢式行動電話、寬頻無線都會廣域網路、無線區域及個人網路系統之應用。

With the fast development of personal communications and the increasing need of multi-media messaging, the major topic for future wireless communications will be to effectively enhance the capability of radio access to provide excellent spectral efficiency and system capacity, so that high data rate transmission and multi-media services can be realized. This proposed 3-year project is to construct a powerful channel coding scheme which integrates three advanced techniques: low density parity-check (LDPC) coding, unequal error protection (UEP), and hybrid automatic repeat request (HARQ) for wireless multimedia and network communications. The first year of the proposed project will be devoted to combining LDPC codes with the space-domain UEP techniques and UEP coded modulation and to establishing the related theoretical fundamentals. New UEP-LDPC codes and UEP LDPC-coded modulation with low peak-to-average power ratio (PAPR) and high coding gain are then designed to provide excellent performance against channel errors. In the second year, we will focus on combining the proposed low-PAPR LDPC codes with the time-domain UEP techniques to construct a flexible coding scheme which can adapt to the unequal error sensitivities of multimedia data. From the viewpoint of cross-layer design, the proposed LDPC coding schemes are then integrated with HARQ to maximize system throughput. In the last year, we will develop an efficient decoder of the UEP-LDPC codes from a soft-defined radio perspective. Then, its DSP/FPGA implementation will be conducted. The results of the 3-year project are expected to be beneficial to both theoreticians and practical engineers, and will promote more LDPC codes for use in future communication systems and networks.