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空时编码是实现宽带无线数据通信的一种极有潜力的技术.本文研究了一种简单而有效的空时格码设计方案——广义延迟分集码.延迟分集可以认为是重复码与多发射天线之间的延迟因子的组合,而广义延迟分集码的思想是将普通的延迟分集中的重复码替换成某些简单的分组码,以提高编码增益.本文给出了广义延迟分集码达到完全分集的充要条件,进而证明了完全分集广义延迟分集码是具有最小复杂度的完全分集空时格码.对于二进制相移键控(BPSK)信号星座上的广义延迟分集码,本文证明了它们具有相同的编码增益;对于四相移键控(QPSK)信号星座上的广义延迟分集码,本文分析了它们的编码增益,并给出了最优的编码方案.所用的分析方法可以推广到其他的信号星座. 相似文献
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MIMO系统中线性弥散空时码的优化设计 总被引:1,自引:0,他引:1
MIMO系统的大部分空时编码方法在设计时单一强调对传输分集性能或传输复用性能的提高,为了联合提高分集性能和复用性能,在LDC编码基础上提出了线性正交弥散空时码(OLDC),LDC编码的优化中利用遗传算法来构造OLDC的空时正交调制基矩阵.优化的编码方法设计简单,便于调制解调.仿真结果表明,OLDC码比传统的LDC编码在误码性能、分集性能、复用性能等方面均有大幅度提高. 相似文献
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空时编码利用多天线阵列提供的并行信道传输信息,可以在保证通信质量的前提下进一步提高信息传输速率。介绍了笔者在正交空时码、空时网格码、酉空时码、差分空时码、混合空时码等方面的工作。采用类脉冲位置调制定义了负数、共轭、求补等运算,将编码矩阵转化为一个用脉冲位置表示的实数矩阵。分析了不同发射天线/接收天线数目、大气湍流强度与系统误码率之间的关系。讨论了差分空时码、酉空时码在不同大气湍流条件下的误码率特性;将分层空时码和空时分组码相结合,对复用增益和分集增益进行合理的折中,提出了一种适合于IM/DD式光通信的混合空时编码方案。 相似文献
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空时编码采用多发送天线设计信道编码,综合考虑分集、编码和调制,从而提高信号在无线衰落信道中的传输可靠性和数据传输率。介绍具有正交性的分组空时码的编译码方法。 相似文献
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Heegard C. Lery S.A. Paik W.H. 《Selected Areas in Communications, IEEE Journal on》1993,11(1):111-118
It is demonstrated how modulation schemes based on QPSK can be directly incorporated into QAM-based systems. It is argued that this leads directly to an easily implementable structure that is both efficient in bandwidth and data reliability. It is contended that the correct solution to the concatenated coding problem for HDTV transmission is to simply extend the modulation codes developed for QPSK-to-QAM modulation. In nonconcatenated situations, a trellis code based on a binary code at rate 2/3 is usually best. However, this is not the case for higher error rates at the output of the trellis decoder (e.g., when a symbol error correcting decoder follows as a concatenated code). The reason for this follows from an analysis of the effect of the number of nearest neighbors on the error rate. A four-way partition of QAM is a natural extension of QPSK modulation; it is a simple matter to incorporate any good QPSK code into a trellis coding scheme for QAM modulation. A concatenated coding scheme based on QPSK trellis codes and symbol error correcting coding is proposed. An example is presented to show the advantages of this approach 相似文献
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Trellis coded modulation is widely used for digital transmission over fading channels. Classical diversity techniques are also frequently employed to combat fading. In this paper two different strategies for equal gain combining are compared, One scheme is based on an interleaved code combining technique. The alternative scheme is based on averaged diversity combining. The well known transfer function bounding technique for trellis codes is used to obtain: expressions for the bit error rate performance of the two trellis coded diversity receivers over a slowly fading Rayleigh channel. The analysis of interleaved code combining is a straightforward modification of the analysis for multiple trellis coded modulation. The analysis of averaged diversity combining is accommodated through a more involved, novel modification of the branch labeling of the error state diagram. The analytic techniques presented in this paper are supported by simulation results using a TCM scheme based on QPSK modulation and a rate-l/2 linear convolution code 相似文献
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An underwater acoustic multimedia communication (UWAMC) system is proposed with 2400 transmission modes according to time-varying multipath underwater acoustic (UWA) channel conditions. The orthogonal variable spreading factor (OVSF) scheme and Gold sequence (GS) scramble code are integrated into multi-input multi-output UWAMC system based on orthogonal frequency-division multiplexing to achieve the quality of service of multimedia transmission in the UWA channel. Binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) adaptive modulation, direct mapping (DM) or space–time block code (STBC) transmission strategies, convolution channel code with rate 1/2 and 1/3, and a power assignment mechanism were adopted in the proposed system. Simulation results show that the bit error rate (BER) and power saving ratio (PSR) performance of the STBC strategy with transmission diversity is superior to that of the DM strategy without transmission diversity, and the performance of the BERs and PSRs of the transmission scheme with the GS scramble code surpasses that of the scheme without the code. The performance of the BERs and PSRs of BPSK modulation with a channel code rate of 1/3 is better than that of BPSK modulation with a channel code rate of 1/2, and the performances of BERs and PSRs of BPSK modulation with a channel code rate of 1/3 are better than that of QPSK modulation with a channel code rate of 1/3. As the length of the OVSF codes increases, the UWAMC system’s BERs decrease, and its PSRs increase. The UWAMC system can achieve either maximum transmission speed or maximum transmission power efficiency. 相似文献
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本文采用步进转动(顺时针或逆时针)的信码作信源,分析了广义四相调制的特性,给出调制信号的频谱和两调相电路间的导纳关系表达式,计算了几种典型四相调制频谱的实例,据此可判定调制的效果和相位误差,并用于动态测试中对四相调制器进行调整,实验表明测得的结果与理论计算是相符的。本文还报道了X波段四相调制器的实验情况,测得其最大相位误差小于4,相让精度可达0.1,插入损耗小于4dB,传送数据率可达 34Mb/s。 相似文献
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Shao Wenchang 《电子科学学刊(英文版)》1985,2(3):233-240
Using the clockwise or anticlockwise stepping pulse code signal, the characteristics of general quaternary phase shift keying
(QPSK) modulation are analysed. This paper gives the spectrums in several operational conditions and the admittance formulas
of related two modulation circuits. Several typical examples of QPSK modulation are calculated. The modulation effect and
the phase error can be decided and the QPSK modulator under the dynamic test may be adjusted by using above results. The experimental
results are in agreement with the theoretical calculations. An X-band QPSK modulator is also presented. The maximum phase
error is less than 4°, the phase accuracy near ±0.1°, the insertion loss less than 4 dB and the data (transfer) rate up to
68 Mb/s. 相似文献
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为了研究信道编码技术对无线光通信副载波系统差错性能的影响,基于无线光通信链路噪声特性,建立了大气信道等效数学模型。采用低密度奇偶校验(LDPC)码作为信道编码方式引入无线光通信,在不同光强闪烁指数下对基于副载波相移键控调制无线光通信系统进行了差错性能仿真,比较分析了LDPC编码前后副载波调制系统的误比特率,并对二相相移键控及四相相移键控两种系统进行了对比。结果表明,副载波二相相移键控调制系统的差错性能优于四相相移键控系统,同时LDPC码在弱湍流信道具有优越的纠错能力,可以获得比未编码系统较高的编码增益,在无线光通信领域具有一定的应用价值。 相似文献
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It is shown that the degradation in the performance of wideband digital transmission systems due to intersymbol interference can be reduced by utilizing diversity selection using coding. A BCH (31, 21, 5) double-error-correcting code and QPSK (quadrature-phase-shift-keying) modulation with coherent detection are used for this study. The probability of word error is taken to be the measure of system performance. Analytic expressions are derived for the word error probability; these expressions simplify the simulation processes. It is found that a diversity selection algorithm using coding can reduce the floor of word error probability, and hence increase the dynamic range of received power before the word error probability reaches that floor 相似文献
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Ümit Ayglü Mehmet E. elebi 《AEUE-International Journal of Electronics and Communications》2004,58(4):268-273
In this paper, 4-state and 8-state space-time trellis codes with full rate, full diversity and high coding gain are proposed for MSK modulation, based on a technique similar to the super-orthogonal space-time trellis code (SOSTTC) design. Since the phase continuity requirement of MSK is the main constraint in space-time MSK code design not all the signal matrices corresponding to the trellis branches are orthogonal. The paper shows that the SOSTTC design technique can be extended to nonorthogonal coding structures. The new space-time MSK codes have frame error performances very close to those of their space-time QPSK counterparts given in [1] 相似文献
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Bit error rate performance of BCH-coded QPSK with coherent demodulation and multiple-branch selection diversity reception is calculated in the presence of fast Rayleigh fading and a cochannel interface environment. How diversity reception affects the optimum code rate and coding gain is investigated from power and spectrum efficiencies points of view.<> 相似文献