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  • 學位論文

單載波單入單出/單入多出/多入多出傳輸系統下改良式有限長度決策回授接收機

Single-Carrier SISO/SIMO/MIMO Transmission Systems with Improved Finite-Length Decision-Feedback Receivers

指導教授 : 黃正光教授
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摘要


近年來,有限長度決策回授接收機,以其良好的接收能及低運算複雜度,吸引了眾多研究能量。本論文致力於設計多種改良式決策回授接收機應用在二大類單載波系統,期能對抗碼際間干擾,多重接取干擾,以及循環碼際間干擾,以提升接收性能,傳輸速度,以及增加系統容量。以外,為充份達到接收機效能,吾人進而提出高精確性及低運算複雜度的單入單出/多入多出通道估測器。 在第一大部分,本論文採用分數間距,渦輪貝氏,以及允許多個決策延遲,設計應用在序列式單載波傳輸系統的回授接收機。首先,吾人利用精確的相關性單入多出雜訊模型,以及半解析方法,快速正確証實分數間距接收機對傳送頻寬,及通道延遲擴展具強健性。再來,吾人根據貝氏均方準則設計渦輪回授接收機,以致更有效消除嚴重碼際間干擾,在高階調變及高次通道階數的情況下,傳統最佳渦輪接收機受限於硬體複雜度已無法實現,但是吾人提出的貝氏接收機,在大幅降低計算複雜度下,仍具有不錯的接收性能。接著,本論文提出配有不同決策延遲之多用戶多入多出回授接收機,期能在增加系統容量下,同時消除多重接取干擾並抑制遠近效應,吾人基於最小聯合誤碼率及使用者功率,提出二種選擇多用戶決策延遲的方法,在標準都市通道環境下[3GPP05],二者方法均被証實不僅能幫助多用戶接收機有效對抗遠近效應,更能讓弱用戶在功率不平衡下得到巨幅增益。 在第二大部分,本論文首先設計新型頻域決策回授接收機,使其應用在具循環字首單載波區塊傳輸系統,期能在不損失頻譜效益下對抗循環碼際間干擾。循環碼際間干擾因為回授濾波器的模數運算以及循環字首的安插,將原本區塊後段干擾摺疊至前段訊號,造成開始訊號極易偵收錯誤,本論文利用循環決策延遲及分工的方式來對抗此干擾,此外,在增加傳送區塊長度以及串接多級回授架構,則可進一步提升通訊信賴度。再來,在特殊字完單載波區塊傳輸統下,吾人使用高斯近似以及向量馬可夫鏈路技巧,二階段系統化分析回授接收機的錯誤傳遞率。為得到更精確分析,殘餘碼際間干擾也納入在此分析模型中,並且在稀疏型多路徑通道的假設下,馬可夫過渡狀態數則可巨幅降低。 最後一大部分,本論文提出具位置選擇性單入單出/多入多出最佳通道估測器,以適用在定點戶外高速傳輸系統下稀疏型多路徑通道。首先考慮以Chu序列為序文的單入單出系統,吾人根據最大似然及最小描述準則設計此最佳通道估測器,此估測器可自動追踨通道稀疏特性,以達到最佳性能界限,並且只需利用一個反傅利葉轉換及叠代架構即可實現,具有極高的硬體實現優勢。再來,在重覆,相位旋轉,Chu(RPC)序列作為多入多出系統的序文幫助下,多入多出之位置選擇性通道估測器可視為多個互斥之單入單出估測器結合,因此與單入單出估測器具有相同的估測性能,此外,吾人利用RPC序列特性也成功推導出高效率分工及平行的計算架構。

並列摘要


Decision-feedback equalizer (DFE) has been shown to provide good tradeoff between performance and complexity. Recently, much research investigated the finite-length DFE for further reducing the complexity. In this dissertation, we consider a number of improved finite-length DFE receiver designs for two prime transmission systems. One is time-domain DFEs design for single-carrier (SC) serial transmission system, and the other is frequency-domain DFE (FD-DFE) design for SC block transmission system with cyclic prefix (CP). In the SC serialtransmission system, we first consider the improved T/M-spaced (fractionally symbol-spaced) DFE design problem under the precise single-input multiple-output (SIMO) correlated noise channel, which is fully characterized by the covariance matrix of receiver pulse shaping. The T/M-DFE receiver is robust to the transmitted excess bandwidth and channel delay spreads. Second, assuming perfect knowledge of the a priori probability of transmission symbol, we derive the optimized DFE’s filter coefficients based on the Bayesian mean-square-error (BMSE) criterion. Such a receiver is shown to be a promising low-complexity alternative to the maximum a posteriori symbol estimator (MAPSE) of traditional turbo equalizer (TEQ), where the a priori probability of symbol is estimated from the extrinsic log-likelihoods of the decoder in previous iteration. Third, we extend the finite-length DFE design problem to the multiuser multiple-input multiple-output (MU-MIMO) system, in particular for power-imbalance channel scenario and assuming individual uplink user has different decision delay. We propose a minimum joint-BER (MJB) scheme for choosing optimal multiple decision delays. It leads to the MU-MIMO-DFE receiver not only being able to resist the near-far effect but also to provide significant performance gain, as compared to the receiver using an optimized but common decision delay. Moreover, an efficient power-ratio-based (PRB) scheme is proposed to solve multiuser decision delay problem in the burst-by-burst transmission application. In the SC-CP transmission system, we investigate an inherent but adverse phenomenon called cyclic intersymbol interference (cyclic ISI) occurred in FD-DFE and the corresponding mitigation scheme. Cyclic ISI arises with the CP insertion and the modulo-N operation of feedback filter (FBF). Although the cyclic ISI can be removed by replacing CP with known unique word (UW), some spectral efficiency will be wasted. Hence, a novel FD-DFE receiver structure using cyclic property is proposed to overcome this problem without sacrificing spectral efficiency. It consists of two parallel cooperating branches of almost identical FD-DFE receivers designed for different cyclic decision delays. The receiver can completely suppress the cyclic ISI at the target raw BER of 10-3 with only slight complexity increase compared to the FD-DFE. To assess the FD-DFE performance analytically, a two-stage framework is presented, which is based on Gaussian approximation and vector Markov chain model. This analysis can provide accurate prediction of the performance degradation under error propagation effect. Finally, tap-selective maximum likelihood (TS-ML) channel estimation algorithm is proposed for broadband long-range block transmission system over sparse multipath channel. Efficient computation algorithm based on fast Fourier transform (FFT) and some modified recursive minimum description length (MDL) criteria is presented and shown to considerably outperform the conventional ML method. For the multi-input/multi-output (MIMO) channel case, an optimal MIMO preamble based on repeated, phase-rotated, Chu (RPC) sequences is fully exploited, and an MIMO-TS-ML algorithm is derived which also leads to highly efficient computation structure.

參考文獻


[HC06] J. K. Hwang, and R. L. Chung, “Performance behavior of T/M-spaced decision feedback equalizer with correlated noise SIMO model,” Int. Journal of Electrical Engineering, vol. 13, pp.297-303, Aug. 2006.
[HCC02] J. K. Hwang, R. L. Chung, and C. H. Chen, “Design and performance analysis of an SI4O-MMSE DFE receiver for GMSK signal over multipath Rayleigh fading channel,” in Proc. IEEE Int. Symposium on Intelligent Signal Processing and Communications Systems (ISPACS-2002), Kaohsiung, Taiwan, Nov. 21-24, 2002.
[HC05] J. K. Hwang, and R. L. Chung, “Efficient and robust multiuser decision-delay selection scheme in the MIMO TDMA system,” in Proc. IASTED Int. Conf. on Communication Systems and Applications (CSA 2005), Banff, Canada, pp. 27-31, July, 2005.
[AC95] N. Al-Dhahir, and J. M. Cioffi, “MMSE decision-feedback equalizers: Finite-length results,” IEEE Trans. Inform. Theory, vol. 41, pp. 961-975, July 1995.
[AC96] N. Al-Dhahir, and J. M. Cioffi, “Efficient computation of the delayed optimized finite-length MMSE-DFE,” IEEE Trans. Signal Processing, vol. 44, pp. 1288-1292, May 1996.

被引用紀錄


張晉文(2010)。具有多根天線之行動OFDM(A)系統下雙邊載波間干擾消除技術〔碩士論文,中原大學〕。華藝線上圖書館。https://doi.org/10.6840%2fcycu201000554
Chen, W. M. (2007). 行動OFDM系統中基於散佈導引信號之時頻通道估測及補償方法 [master's thesis, Yuan Ze University]. Airiti Library. https://www.airitilibrary.com/Article/Detail?DocID=U0009-0707200721465200

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