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標題: | 差分振幅及相移鍵控用於非同調無線通訊環境下之分集傳送及接收 Diversity Transmission and Reception of DAPSK Over Noncoherent Wireless Communication Channels |
作者: | Chi-Hua Huang 黃啟華 |
指導教授: | 鐘嘉德 |
關鍵字: | 放大轉送,合作式分集,合作式中繼,差分振幅及相移鍵控,差分偵測,差分空時調變,頻率選擇性瑞雷衰退通道,多重輸入輸出,中上衰退通道,正交分頻多工,萊斯衰退通道, Amplify-and-forward (AF),cooperative diversity,cooperative relaying,differential amplitude and phase shift keying (DAPSK),differential detection,differential space-time modulation (DSTM),frequency-selective Rayleigh fading channel,multiple-input multiple-output (MIMO),Nakagami-m fading channel,orthogonal frequency-division multiplexing (OFDM),Rician fading channel, |
出版年 : | 2014 |
學位: | 博士 |
摘要: | 在無線通訊裡,多重輸入輸出技術藉由在傳送端及接收端架設多根天線能增進資料傳輸量及可靠度。而近年來,合作式中繼技術經由使用者之間的互相合作能加大基地台覆蓋率及可實現分散式空間分集。除了多重輸入輸出及合作式中繼技術外,正交分頻多工也是一極具競爭力的技術,因為此技術能非常有效地利用頻譜及易於與其他現存的通訊技術做結合,所以被廣泛採用於現今及未來的無線通訊系統標準裡。過去關於多重輸入輸出、正交分頻多工及合作式中繼系統的研究大部分著重於同調偵測,其中這些研究需先假定接收端可以獲得所有傳輸通道的精確通道狀態資訊包含瞬時通道響應、訊號雜訊功率比及平均通道統計特性。然而在快速時變環境下,所有傳輸通道的精確通道狀態資訊是非常難以獲得,因此執行同調偵測變得不可行。為了減少對於精確通道狀態資訊的需求,一具有高功率效率的差分調變技術,名為差分振幅及相移鍵控已被提出並且在點對點通訊裡有著相當廣泛的研究及討論。差分振幅及相移鍵控採用同心圓狀的星座點架構,裡面包含多層的環,每一層環上都有相同密度的信號點。利用差分編碼的方式,差分振幅及相移鍵控將振幅符元及相位符元分別負載於相鄰傳送符元的振幅比及相位差。藉由觀察兩個相鄰接收信號,可在不需要任何的通道狀態資訊下完成差分振幅及相移鍵控的差分偵測。在本論文中,我們將差分振幅及相移鍵控應用於非同調多重輸入輸出、正交分頻多工及放大轉送多中繼站系統並且設計差分振幅及相移鍵控的分集傳送及接收方式以進一步改善這些系統的錯誤率效能及簡化接收機實現。
在非同調多重輸入輸出系統中,我們提出了一種使用分集編碼式差分振幅及相移鍵控的新式差分空時調變,其在傳送天線有著低且固定的峰均功率比。最大相似度接收機及近似最大相似度接收機在獨立非同分佈時間相關性萊斯衰退通道下已發展出來得以對分集編碼式差分振幅及相移鍵控信號進行差分偵測。其中,最大相似度接收機需要平均通道動差、接收信號雜訊功率比及平均雜訊功率等通道狀態資訊來實現,而近似最大相似度接收機不需要除了平均雜訊功率以外的通道狀態資訊,因此相較之下更容易實現。近似最大相似度接收機的位元錯誤率上限在獨立非同分佈時間相關性萊斯衰退通道下已完成分析。除此之外,在獨立非同分佈非時變瑞雷衰退通道及高接收信號雜訊功率比的情況下,一個近似位元錯誤率上限也已推導出來。利用此近似錯誤率,我們發展出了決定分集編碼系數的準則。對於多接收天線的非同調正交分頻多工系統而言,憑藉均勻交錯子載波群組化方式可將所有正交分頻多工系統上較高相關性的子載波劃分成擁有較小相關性的子載波群組,每一個群組可視為有著較小相關性的多重輸入輸出系統。因此先前發展出來的分集編碼式差分振幅及相移鍵控和近似最大相似度接收機可直接應用於非同調正交分頻多工系統以開發頻率及天線分集。最後,在非同調放大轉送多中繼站系統中使用差分振幅及相移鍵控,相等式增益接收機及加權式增益接收機在此發展出來,能以非同調的方式結合來自於源頭端及中繼站的信號進而達到合作式分集的效果。相等式增益接收機不需要任何的通道狀態資訊,然而加權式增益接收機則需要源頭端至中繼站及中繼站至目的端的平均信號雜訊比。無論存不存在信號雜訊功率比的估測錯誤,一個整合相等式增益接收機及加權式增益接收機的位元錯誤機率上限的一般表示式在獨立非同分佈非時變萊斯及中上衰退通道下已完成推導。數值與模擬結果驗證了我們推導出的錯誤率上限的正確性及緊密性並且展示了所提出的差分振幅及相移鍵控系統能提供相較於先前提到的非同調無線通訊系統更好的錯誤率效能。 In a wireless communication link, multiple-input multiple-output (MIMO) techniques have been developed to increase throughput and reliability of data transmission by employing multiple antennas at the transmitter and the receiver sides. Recently, cooperative relaying techniques have been proposed to enlarge the cellular coverage and realize distributed spatial diversity in terms of user cooperation. Other than MIMO and cooperative relaying techniques, orthogonal frequency-division multiplexing (OFDM) is also a promising technique and widely adopted in many recent and future wireless communication standards since it can make very efficient use of available spectrum and be easily combined with other existing communication techniques. Most of past studies on MIMO, OFDM, and cooperative relaying systems focus on coherent detection, which is based on the assumption that perfect channel state information (CSI) of all transmission links including instantaneous channel impulse response, signal-to-noise power ratio (SNR), and average channel statistics is available at the receiver. However, in fast time-varying environment, the sufficiently accurate CSI of all transmission links is very difficult to obtain, and thus performing coherent detection may not be feasible. In order to reduce the requirement for perfect CSI, a differential modulation technique with high power efficiency, namely differential amplitude and phase shift keying (DAPSK), has been proposed and well studied in point-to-point communications. DAPSK employs a star constellation with multiple concentric amplitude rings, each containing the same number of uniformly distributed phasors, and sequentially encodes information onto the amplitude ratio and phase difference between currently and previously transmitted symbols. By operating two consecutively received signals, the differential detection of DAPSK can be achieved without any CSI. In this thesis, we apply DAPSK into the noncoherent MIMO, OFDM, and multiple-relay systems and design the diversity transmission and reception of DAPSK for these noncoherent wireless communication systems to improve the system error performance and simplify the receiver implementation. In the noncoherent MIMO system, a new differential space-time modulation (DSTM) using diversity-encoded DAPSK is proposed with low and fixed peak-to-average power ratio at each transmit antenna. The maximum-likelihood (ML) and an asymptotic ML (AML) receiver are developed for differentially detecting diversity-encoded DAPSK signals over independent but not identically distributed (inid) time-correlated Rician fading channels. The knowledge of CSI including average channel moments, received SNRs, and average noise power is required for realizing the ML receiver, while the AML receiver is devoid of any CSI except average noise power and thereby much easier to implement. The bit error probability (BEP) upper bound is analyzed for the AML receiver over inid time-correlated Rician fading channels. Particularly, an approximate BEP upper bound of the AML receiver is also derived for inid time-invariant Rayleigh fading channels with large received SNRs. By virtue of this approximate bound, a design criterion is developed to determine the appropriate diversity encoding coefficients for the proposed DAPSK MIMO system. For the noncoherent OFDM system with multiple receive antennas, resort to uniformly interleaved subcarrier grouping can divide all correlated subcarriers of an OFDM system into the nonoverlapping groups containing lightly correlated subcarriers. Thus, the previously developed diversity-encoded DAPSK and the corresponding AML receiver can be directly applied by treating each group as a MIMO system with lightly correlated transmit antennas so that both frequency diversity and spatial antenna diversity can be achieved. Finally, in the noncoherent amplify-and-forward multiple-relay system using DAPSK, an equal gain combining (EGC) receiver and a weighted gain combining (WGC) receiver are developed to noncoherently combine received signals from direct and multiple relay links and thereby achieve cooperative diversity. The EGC receiver operates without any CSI, while the knowledge of average SNRs on source-relay and relay-destination links is required for realizing the WGC receiver. A unified expression of BEP upper bound is analytically derived for both receivers over inid time-invariant Rician and Nakagami-m fading channels with or without link SNR estimation errors. Numerical and simulation results verify the correctness and tightness of the derived BEP bounds and show that the proposed DAPSK systems can provide improved error performance over the existing works on the above-mentioned noncoherent wireless communication systems. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/5384 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 電信工程學研究所 |
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