在無線通道的編碼技術中，多元性與編碼增益是影響錯誤效能的兩個重要因素。我們在第二章中回顧具延遲處理器的籬柵碼與空時碼架構。正交分頻多工系統可以提供高的頻譜使用率，藉由加入循環字首有效克服信號與子載波之間的干擾。在第三章中，我們回顧在正交分頻多工系統的編碼技術並比較其性能。在第四章中，我們結合具有延遲處理器的籬柵編碼架構與正交空時區塊碼應用於正交分頻多工系統。此種編碼設計可以在頻域獲得更高的多元性，使每一個正交分頻多工系統的子載波有很強的抗衰減能力。在獲得相同的多元性前提下，此種編碼設計降低了解碼的複雜度。對於不同的多路徑衰退通道與不同的信號延遲擴散，我們可以使用重複性解碼、超籬柵解碼演算法與交錯器改善錯誤性能。 The diversity gain and coding gain are two important factors in wireless communications. We review the structures of trellis codes with a delay processor and space-time coding in chapter 2. The orthogonal frequency division multiplexing (OFDM) system can provide high spectral efficiency, and combat the interference between each OFDM symbol and the interference between each subcarrier in one OFDM symbol effectively. In chapter 3, we review two coded OFDM systems and compare their performance. In chapter 4, we concatenate space-time block coding with a delay processor and a signal mapper in OFDM system. We can get more diversity gains in frequency domain and enhance the abilities to resist fading in an OFDM symbol. The decoding complexities are decreased by the code design. We use iterative decoding, super trellis decoding and interleaving to improve the error performance for different number of resolvable paths and delay spreads.
