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  • 學位論文

於二維干擾下資料偵測之設計與應用

Design and Application of Data Detection in the Presence of Two-Dimensional Interferences

指導教授 : 闕志達

摘要


近年來二維干擾成為通道中不可避免的現象,例如行動多天線輸入輸出正交分頻多工(MIMO-OFDM)系統通道中的載波間干擾(ICI)及天線間干擾(IAI),或者是全像術光學儲存系統通道中的二維像素間干擾(IPI)。傳統資料偵測方法將兩個維度分開解決,因此常會遭遇錯誤傳遞(error propagation)的問題,但若是同時考慮兩個維度則因複雜度過大而無法實現。 因此本論文提出了一種新的演算法,根據最大事後機率(MAP)準則,針對兩個維度中的解分別建立列表(list),隨著疊代更新內容,藉由共同考慮兩列表中的解,達到消除錯誤地板現象(error floor)的效果。 本論文選擇行動多天線輸入輸出正交分頻多工系統以及全像術光學儲存系統兩個應用,和傳統演算法比較在位元錯誤率上的表現,數值模擬結果顯示出新演算法確能解決傳統演算法遭遇的錯誤傳遞困境,甚至在多天線輸入輸出正交分頻多工系統下能逼近靜態通道的表現。此外本論文也以聯合邊界(union bound)的技巧推導符元錯誤率之理論上限,觀察列表長度對錯誤率表現的影響。 在實作方面,本論文提出數個降低複雜度的技巧,以避免重複運算、單獨計算差異量、以簡單的檢測方法提前結束等等為原則,在付出合理的成本下達到期待的錯誤率表現。並且本論文將新演算法的在兩個應用下的硬體設計以場域可程式化閘陣列(FPGA)做功能驗證。 經由數學分析、模擬驗證及硬體實現,本論文為二維干擾通道的資料偵測提供了一新的解決方案。

並列摘要


Recently, two-dimensional (2-D) interferences have become inevitable in channels of many scenarios, such as inter-carrier interference (ICI) and inter-antenna interference (IAI) in mobile multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) systems or 2-D inter-pixel interference (IPI) in holographic data storage (HDS) systems. Conventional solutions treat 2-D interferences separately and often suffer from the notorious error propagation problem. On the other hand, dealing with 2-D interferences simultaneously is infeasible due to extremely high complexity. This thesis proposes a Turbo Receiver with Interference-aware Dual-List (TRIDL) detection that enjoys the advantages of bit-interleaved coded modulation (BICM)-with iterative decoding (ID). In this architecture, an Interference-aware Dual-List (IDL) detection algorithm is designed to combat 2-D interferences and achieve near maximum a posteriori (MAP) performance by exploiting dual lists. The list-based concept further eliminates redundant calculation, leading to benefits of low complexity. The strength in error rate performance of the IDL detector is shown in two applications: mobile MIMO-OFDM and HDS systems. This thesis not only derives an upper bound on the uncoded symbol error rate (SER) but also provides insightful discussion about the bit error rate (BER) performance through Monte Carlo simulations. Concerning feasibility, this thesis also presents several techniques to reduce complexity in arithmetic operations. By eliminating redundant calculation and sharing common sub-blocks with initial detection block, up to 99.63% of complex additions, 99.69% of complex multiplications and 67.25% of comparisons are saved in the mobile MIMO-OFDM system. As a result, TRIDL running for 10 iterations requires around 4.3-fold complex additions, 2.5-fold complex multiplications and 36-fold comparisons used by the conventional non-iterative algorithm. Similar strategies also eliminate about 57.40% of arithmetic operations in the binary HDS system while over 73.78% is saved in the 3-bit gray-scale HDS system, resulting in similar number of additions and 50% of the multiplications used by the conventional algorithm. The thesis also discusses hardware design of the TRIDL algorithm. The entire TRIDL detection for a 4x4 MIMO-OFDM system with 16QAM and 64QAM as well as for a 3-bit gray-scale HDS system are designed and verified in FPGA. We exploit techniques such as resource sharing, pointer-based delay buffer, and folding transform to achieve low-power and low-complexity design. In consequence, experimental results indicate about 34.8% reduction of resources in TRIDL for the MIMO-OFDM system.

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