基于mimoofdm系統的正交空時分組碼單位抗衰落復正交空時分組碼級聯的turbo碼畢業論文外文翻譯(編輯修改稿)

　

【文章內容簡介】 eve full transmit diversity and has a simple Maximum Likelihood (ML) decoding algorithm while used at the decoder. For this, STB code is an attractive approach for practical purposes. But ,it is proved that for STB code, a plex orthogonal design which provide full diversity and unit rate is not possible for more than two antennas, and the 1/2rate or 3/4rate STB code for three and four transmit antennas (4Tx) are also given with the coderate 2/3rate STB code for five transmit antennas is proposed recently. Considering the full rate is the important means to implement high data rate service and very important for low Signal to Noise Ratios (SNRs). Ⅱ . Unitrate Complex Orthogonal STB Code diversity STB codes review In this subsection, we review the basic principle of STB code that provides maximum possible diversity for multiple transmit antennas in wireless munications. Let L,M and T be positive integers, a plex orthogonal STB code is defined by a TM dimensional transmission matrix G, every entry of which is plex linear bination of the 。 input symbols lssss ,..., 321 ,and their conjugates **3*2*1 ,..., lssss ,and it satisfies the following plex orthogonal condition MMLL LH ISGG ???? )||(21 where superscript H denotes the Hermitian conjugation and I is the MM identity matrix. M and T are the numbers of transmitting antenna and time slots used to transmit L input symbols, respectively. STB code In this subsection, we consider a munication system prising 3 transmit antenna and 1 receive antenna that operates in a Rayleigh of analysis. The transmitter and receiver structures of the munication system with TC are shown in and , respectively. The data source bits are firstly encoded by the turbo encoder, then are mapped into corresponding constellation symbols。 the symbols are STB encoded, the resulting encoded symbols are modulated onto a pulse waveform and then transmitted from three transmit antennas respectively. In TDD model, the channel gain estimated by the uplink can be used to downlink transmission, so we can choose two maximum channel gain amplitudes from estimated three antenna channel gains, and use corresponding two transmit antennas to transmit the coded symbols, respectively. Namely, if |h1|≥|h3| and |h2|≥|h3|, we choose Txl and Tx2 to transmit symbols. Similarly, the other two cases are also easy to analysis. Here, let 1mh and 2mh denote the two chosen maximum channel gains, respectively. Then at the receiver, the received signal matrix at time slot 1 and slot 2 can be expressed by ??????????????????????????????2121*1*2212212hnnhhssssEnGErrrmmρ It can be changed as nHsEnnsshhhhErrrmmmm~2/2/~ *2121*1*221*21????????????????????? ????????? The normalized constant ρ is used to keep the total transmitted energy be E ,here ρ= 2/12? , E is the transmitted energy at each transmission interval. n is the 21 white noise matrix ， The SNR is defined as E/No. The elements of H can be obtained from the estimated channel gain coefficients in the uplink by the use of TDD mode. Considering 222221 )|||(| ??? IhhHH mmH Then, ?????? ??????????? 1*2* 21 2*2* 11212221 )|||(|2/~ mm mmmmH hnhn hnhnsshhErH Thus the decoding can be performed via linear bining and maximum likelihood decision as follows: ??????????????????????????????2121*1*2212212/ nnhhss ssEnhGErrrmmρ References [1] Siavash M Alamouti. A simple transmit diversity technique for wireless (08). [2] V R Calderbank. Spacetime block codes from orthogonal (07). [3] XueBin Liang. A highrate orthogonal spacetime block code. 2020(05). [4] T H Hanzo. Spacetime codes and concatenated channel codes for wireless munications 2002(02). [5] C Glavieux. Near optimum error correcting coding and decoding:Turbocodes1996. 譯文 單位抗衰落復正交空時分組碼級聯的 Turbo 碼 空時編碼因其正交性簡單解碼和高分集 增益是一種防止衰落的有效的發射變化技術。在本文中，假設對于多個天線的時分雙工模型有一個單位速率的復正交空時編碼。同時，使用 Turbo 碼通過利用其良好的性能來改進所假設的空時分組碼的抵抗衰落信道的突發的錯誤的能力。與全樣性的多天線空時分組碼相比，所假設的碼能夠有單位速率以及部分的多樣性，并且它在相同的系統吞吐量時計算復雜性要小的多。更好的是，因其部分多樣性， Turbo 碼的應用能有效的彌補性能損失。仿真結果表明在相同的系統的吞吐量以及 Turbo 碼串連情況下，所假設的碼相對于那些全樣性的碼有更加低的誤碼率。 Ⅰ 介 紹 近年來，因在基站使用的簡單性和多天線的靈活性，傳送多樣性作為在衰落信道中抵抗嚴重衰落的方法而被廣泛研究。 Alamouti 建議一種用兩個天線的簡易傳送多樣性計劃。一種對超過兩個傳送天線的引申也產生了，它顯示出 Alamouti是空時分組編碼的一種特殊例子。這個空時分組編碼能夠達到傳送全樣性并且在譯碼時有最大的解碼可能性。因此，空時分組碼是一種有實用性的很有吸引力的編碼方式。然而，對于正交分組碼。對于超過兩個天線的復正交設計，提供全傳送和單位速率是不大可能的，對于三根或四根天線 1/2速率或者 3/4速率 的空時分組碼也給出。對于 5根傳送天線的 2/3速率的空時分組碼也被提出了。近來，考慮到全速率是一種非常重要的方法來運行高數據速率服務，同時對低信號比率也非常重要。另外，由于接收大小和能力的限制，空時分組碼的低復雜解碼算法也是必需的。 Ⅱ 單位速率正交空時分組碼 全部分集的 空時分組碼 在這部分，我們回顧在無線通信中對于傳送天線的提供最大多樣性的空時分組碼的基本原則。假設 L,M,T 都是正整數，一個復正交空時編碼被定義為一個MT? 的 傳輸矩陣 G,對于這個矩陣中的每一個詞條都是輸入為 1 2 3, , ,... ls s s s 的 L的復雜線性組合 ,并且它們的共軛 * * * *1 2 3, , ,... ls s s s ,而且它滿足下面的復正交條件 21 ||LHL M MLG G S I ????? ????? 在此 ,上標 H 代表的是厄米的結合 ,而 I 則是 MT? 的單位矩陣。 M 和 T 是傳送天線的數量和傳送 L 輸入信號的時間標志。 2 單位速率空時分組碼 在這一部分，我們考慮一個 由三根天線所組成的通信系統， 1接收到在平穩衰落環境和時分雙工模型的天線信號。包含 Turbo 碼的這個通信系統的傳送和接收結構分別在圖 1和圖 2中給出。 圖 1 圖 2 數據來源位首先是由 Turbo 碼的輸入，然后被映射入對應的標志。這個表示就是空時分組碼所編碼的，由此產生的編碼符號調制到一個脈沖波形，然后分別從三個傳輸天線轉交。 在時分雙工模型中在時分雙工模式，信道增益估計上行可用于下行傳輸，所以我們能夠從估計三個天線通道增益來選擇兩個最大振幅 增益的通道，并使用兩個相應的發射天線。我們定義，如果 |h1|≥|h3|并且 |h2|≥|h3|，我們選擇 Tx1和 Tx2 來傳遞標志。相似的，另外兩個情況也很容易分析。假設 1mh 和 2mh 分別指代兩個被選擇的最大的通道增益。然后在這接收端，時隙 1和時隙 2接收信號矩陣可以表示為 ??????????????????????????????2121*1*2212212hnnhhssssEnGErrrmmρ 也可以表示為 nHsEnnsshhhhErrrmmmm~2/2/~ *2121*1*221*21????????????????????? ????????? 歸一常數 ? 用來保持總的傳送能量 E，這里 1/22? ?? ，