【正文】 ,同時滿足這一標準法典 ,必須犧牲一些比 例的數(shù)據(jù)傳輸速率。因此 ,他們的誤碼率是空時編碼的界定標準之一 ,正交率提供免費傳授由于正交碼。這是特意直截了當(dāng)?shù)囊詣?chuàng)造了這個方案的創(chuàng)始人名字為名。他們的代碼。然而 ,作為明確的例子 ,為什么不能到達率 1,其他什么必須解決的問題有如何用空時碼接收更好的信號。 4 個發(fā)射天線 兩個直截了當(dāng)?shù)拇a為 4 發(fā)射天線是 : ???????????????????????????????????????*1*2*3*4*2*1*4*3*3*4*1*2*4*3*2*112342143341243212/14ccccccccccccccccccccccccccccccccC ， 以及 ? ? ? ?? ? ? ??????????????????????????????????????????222222222222*22*11*11*22*3*3*11*22*22*11*3*333*1*233214/3,4ccccccccccccccccccccccccccccC. 這些編碼實現(xiàn) 1/2 比特和 3/4 比特的空時編碼 , ?????????????????1*2*32*1*33*1*23214/3,40000ccccccccccccC , 從所有具有 相同能力 的 天線 可知 。為了考慮解碼方法 ,無線通信系統(tǒng)的模型是必需的。 )()(1 1 irR tjint nj jti tT R ?? ?? ?? ?? 滿足對于準正交空時分組編碼而言 , 由于發(fā)射矩陣的各行不是完全正交的 , 因此在接收端進行最大似然譯碼時需對信號進行聯(lián)合檢測 , 這就使得其譯碼算法較之正交空時分組編碼要復(fù)雜一些。雖然從表面上看 ,這是一個簡單的直線解碼方案 ,提供最大的 似然性 。 and it hay much smaller putational plexity under the same system throughput. Moreover, the application of TC can effectively make up for the performance loss due to partial diversity. Simulation results show that on the condition of same system throughput and concatenation of TC, the proposed code has lower Bit Error Rate (BER) than those fulldiversity codes. Ⅰ . Introduction Recently, transmit diversity has been studied extensively as a method of bating detrimental effects in wireless fading channels due to its relative simplicity of implement and feasibility of having multiple antennas at the Base Station (BS).A simple transmitter diversity scheme using tw0 transmit antennas is proposed by Alamouti .An extension to more than two transmit antennas is presented ,where it is shown that the Alamouti scheme is a special case of SpaceTime Block(STB) code. The STB code scheme can achieve 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 。 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(fù)正交空時分組碼級聯(lián)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(fā)射變化技術(shù)。同時，使用 Turbo 碼通過利用其良好的性能來改進所假設(shè)的空時分組碼的抵抗衰落信道的突發(fā)的錯誤的能力。更好的是，因其部分多樣性， Turbo 碼的應(yīng)用能有效的彌補性能損失。 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。一種對超過兩個傳送天線的引申也產(chǎn)生了，它顯示出 Alamouti是空時分組編碼的一種特殊例子。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。對于超過兩個天線的復(fù)正交設(shè)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。近來，考慮到全速率是一種非常重要的方法來運行高數(shù)據(jù)速率服務(wù)，同時對低信號比率也非常重要。 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。 M 和 T 是傳送天