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瑞利衰落下的空时频(STF)分组编码OFDM系统 总被引:4,自引:3,他引:1
基于正交频分复用(OFDM)系统,提出了一种发射分集方案——比特交织空时频(BI—STF)分组编码。其基本思路是:应用子载波分群方法并选择合适的系统参数,将OFDM系统转化成分群OFDM(G-OFDM),对每个群分别进行空时频分组编码(GSTFBC);在编码比特被重组和映射成GSTF分组编码前进行合理的比特交织,并按一定的规则分配给各个单群子载波进行酉星座旋转(CR)预编码。随后讨论了该方案的频谱利用率和成对错误概率(PEP)。仿真结果表明,同其它编码方案相比,提出的方案能在频率选择性瑞利衰落信道下获得最大的空间分集和频率分集增益,且只有较低的解码复杂性。 相似文献
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介绍了空时分组编码,正交频分复用原理以及STBC—OFDM的一般系统模型。阐述了STBC—OFDM系统的性能和当前对STBC—OFDM技术研究取得的进展,最后时STBC—OFDM技术在未来移动通信中的研究方向做了前景展望。 相似文献
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空时编码在OFDM系统中的应用 总被引:1,自引:0,他引:1
研究了空时分层码(LSTC)、空时分组码(STBC)和空时网格码(STTC)3种典型的空时编码技术。讨论了各自的编码原理和译码原理。以空时分组码为重点,介绍了OFDM系统的基本原理,将空时分组码和OFDM技术相结合,对STBC-OFDM系统的基本模型加以探讨,理论分析系统接收端的信噪比性能,通过M atlab仿真对收发... 相似文献
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为获得存在多径衰落的MIMO-OFDM系统中高速率传输方案,给出了一种基于线形星座预编码和坐标交织的速率为1的简单空时频分组码.该传输方案通过线性星座预编码来获得频率分集增益,通过坐标交织变换来获得传输速率为1,且能适当改善系统的误码性能.仿真结果表明,与传统的结合空时码的OFDM系统相比,该方案能获得更大的分集增益、更高的频谱效率和更好的误码性能.在误码率为10^-2的未加信道编码的条件,本文方案与传统方案相比,至少能够提供约4dB的性能增益.若在接收端采用MMSE等线性接收方案,本文方案的计算复杂度并没有明显的增加。 相似文献
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以正交空时分组码为例讨论了空时编码技术的性能特征。给出了各种STC-OFDM系统的BER性能。理论分析和仿真结果表明,STBC-OFDM系统在频率选择性的瑞利衰落信道下,性能优于其它STC-OFDM系统。 相似文献
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提出一种基于空时分组编码的异步正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)协同分集方案。提出的方案在中继节点实现OFDM调制及OFDM符号的时间反转和复共轭,信宿节点接收信号的每个OFDM子载波都具有Alamouti空时分组编码结构。信宿节点采用最大似然(ML,Maximum Likelihood)译码准则译码。仿真结果表明,提出的异步OFDM空时协同分集方案无需两个中继节点的同步可获得二阶分集增益,且与其它协同分集方案相比,该方案的误比特率和实现复杂度都更低。 相似文献
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在双向中继系统中,针对采用SSK传输不能获得发射分集且频谱效率较低的问题,提出了一种对角空时码空间调制算法,简称为DSTC-SM。该算法在源节点处采用DSTC-SM码字发送信号,在中继节点处配置单根天线对接收到的信号进行放大并将其转发至目的节点。DSTC-SM码字的构造中以对角码作为基本码块,并与空间调制(SM)技术相结合,采用循环结构来激活不同的天线。此外,通过对旋转角度的优化使该方案在即使只激活一根天线的情况下仍然可以获得发射分集增益。仿真结果表明,所提的算法比现有的算法具有较好的误码性能。 相似文献
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通过引入多电平振幅调制和变换矩阵方法,提出了一种基于多幅值调制的差分正交空时分组码方案。该方案可克服通常基于PSK调制的单幅值差分空时码(DSTC,differential space-time coding)在高频带利用率下由于星座符号间的最小距离减小所带来的性能下降,而且可用于编码矩阵是非方阵情况,避免了已有方案仅适合于方阵码矩阵。与已有单幅值DSTC相比,所提方案有着高的频谱效率和编码增益,且可实现线性译码复杂度和高的码率。此外,还给出了所提方案级联信道编码时的性能。仿真结果表明所提方案与已有单幅值DSTC方案相比,有着较低的误比特率,而且信道编码后的所提多幅值DSTC也好于相应的单幅值DSTC。 相似文献
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基于空时分组编码的差分检测方法 总被引:1,自引:1,他引:0
利用正交设计原理提出了通用的差分空时分组码(GDSTBC,general differential space-time block code)。与已有的差分调制方法相比,GDSTBC对信号星图无任何限制,因而可利用幅度和相位同时携带信息提高频谱效率。基于最大似然准则,给出了平坦。Rayleigh衰落信道下的非相干译码器。我们将证明:在高信噪比下,GDSTBC能够以线性复杂度和满天线分集恢复数据符号;在PSK调制方式下,没有信道估计时性能下降3dB;Ganesan基于PSK星图的差分空时分组码、Xia基于APSK星图的差分空时调制技术都可看成GDSTBC的特例。 相似文献
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在研究传统的空时编码 OFDM 系统模型及误码率性能的基础上,提出了 Turbo 码级联空时格码的 OFDM 系统方案;并给出了该系统在无线瑞利衰落信道中的性能上界和误码率仿真结果,仿真结果表明:该系统能最大限度地利用所有的分集资源,获得相当大的分集增益和编码增益。 相似文献
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A bit allocation algorithm is presented for orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic–geometric means inequality. Consequently, this algorithm has a simple procedure and low computational complexity. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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讨论了多发射天线OFDM系统中有限比率反馈对通信系统误码率的影响。通过发射端的波束成形将多天线OFDM无线信道等价为独立的并行子信道,并结合有限比率反馈下的波束成形矢量集的最优设计,推导了多发射天线下OFDM系统中反馈比特数对误码率影响的表达式,同时给出了反馈比特数对误码率的相对误差的影响。数值仿真表明,当发射天线数为2且10dB≤Es/N0≤20dB时,为使误码率的相对误差小于20%,每一子信道需3~5的反馈比特数,当发射天线数为3时则需7~8的反馈比特数,可为带反馈信道的多天线OFDM系统设计提供参考。 相似文献
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对于多发单收天线(MISO)通信系统,考虑发射端信道状态信息的差错(ECSI).研究正交空时分组码的MISO系统的多天线选择,提出了一种CSI差错的选择性信道序统计特性求解方法.在独立的平坦瑞利衰落信道和多进制相移键控(MPSK)调制下,推导了一种较准确的系统比特误码率(BER)切诺夫上界解析式.最后系统BER性能上界的数值结果和仿真结果研究表明:多发射天线选择技术能极大地提高系统的传输质量,能有效地抵抗ECSI的影响. 相似文献
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Andreas A. Hutter Selim Mekrazi Beza N. Getu Fanny Platbrood 《Wireless Personal Communications》2005,35(1-2):173-185
We investigate space-frequency block coding for OFDM systems with multiple transmit antennas, where coding is applied in the
frequency domain (OFDM carriers) rather than in the time domain (OFDM symbols). In particular we consider Alamouti's code,
which was shown to be the optimum block code for two transmit antennas and time domain coding. We show that the standard decoding
algorithm results in significant performance degradation depending on the frequency-selective nature of the transmission channels,
such that a low coherence bandwidth results in a huge degradation. The optimum decoding algorithm that alleviates this problem
is the maximum-likelihood decoder for joint symbol detection. We present a performance analysis for the investigated space-frequency
decoders in terms of the achievable BER results. Furthermore we compare space-time and space-frequency coding and discuss
the respective advantages and drawbacks of the different decoding algorithms in terms of their complexity. It should be noted
that for the space-time approach we introduce the so-called matched-filter receiver, which shows significantly lower complexity
compared to the maximum-likelihood decoder known from literature. The HIPERMAN system serves as an example OFDM system for
quantitative comparisons.
Andreas A. Hutter received the Dipl.-Ing. (electrical engineering) and the Dr.-Ing. degree from Munich University of Technology (TUM) in 1997
and 2001, respectively. From 1997 to 2000 he was with the research and engineering department (FIZ) of BMW at Munich where
he was project leader for the broadband wireless data initiative. In 2000 he was visiting researcher at Stanford University
and in 2001 he joined the Swiss Center for Electronics and Microtechnology (CSEM) as senior R&D engineer. His research interests
include the characterization of the propagation characteristics of mobile communication channels, signal-processing techniques
for multiple antenna systems and the different aspects related to the design of ultra wideband systems. Andreas A. Hutter
is co-recipient of the VTC-Fall 1999 best paper award.
Selim Mekrazi received his M.Sc. in Digital Communications, Signal Processing and Telecommunications from Université de Rennes 1, Ecole
Nationale Supérieure de Télécommunications de Bretagne (ENST Bretagne) and Ecole Supérieure d'Electricité (Sup'Elec), France,
in 2003. In October 2003, he joined Eurecom Institue (Sophia-Antipolis, France) where he is currently pursuing his Ph.D in
Electrical Engineering. His general interests lie in the areas of information theory, signal processing, digital communications,
micro-electronics and public safety systems. Current researches focus on physical layer transmission techniques and implementation
aspects for high-throughput, reconfigurable and rapidly deployable systems.
Beza Negash Getu was born in Bahir Dar, Ethiopia, on May 27, 1975. From 1992 to 1997, he followed Addis Abeba University and he completed
his B.Sc. degree in Electrical Engineering. Following his graduation, he was employed at Bahir Dar University as an assistant
lecturer. From June 1998 to August 2000, he studied the Master of Science Program of Delft University of Technology, the Netherlands
and obtained his M.Sc. degree in Electrical Engineering. In October 2000, he joined the Antennas and Propagation group of
Prof. Dr. Techn. Jorgen Bach Andersen at the Center for Person Kommunikation (CPK) of Aalborg University, Denmark as a Ph.D.
student. He worked in the field of Wireless Communications focusing on smart antennas and MIMO systems. The subject are encompasses
communication theory, propagation and antenna research with the goal of optimizing link spectral efficiency and bit error
rate. During 2002–2003, he spent six months in the Wireless Communications group at CSEM, Neuchatel, Switzerland, working
on the same area. Beza N. Getu received the Ph.D. degree from Aalborg University in 2003.
Fanny Platbrood received her Dipl.Eng. (M.Sc.EE) Degree in Electrical Engineering from the “Faculté Polytechnique” (Mons-Belgium) in 1996
after having made some research at the University of Rochester (NY-USA) and at the Swiss Federal Institute of Technology (EPFL).
She worked as ASIC designer in the VLSI Design Department of Alcatel Bell, Belgium until end 1998. She was more particularly
responsible for the ASIC development and testing for ADSL. In fall 1998, she joined the CSEM to work on research and development
as an expert in wireless communications. She worked then on the PHY layer development for the WLAN standard HiperLAN Type-2
(H/2). From September 1999 until September 2001, she worked in the ESPRIT SLATS European project where she began first as
workpackage leader of the GSM and WCDMA PHY software module development to become later the SLATS project manager for CSEM.
In 2001, she was responsible for a UMTS concept study in a receiver structure. Up to end 2003, she worked on the IST SCOUT
project on software architectures for re-configurable baseband systems and APIs definition. From 2002 to September 2004, she
was responsible for the IST STRIKE project where she worked on Multiple Transmit Multiple Receive (MTMR) coding techniques
applied to BFWA systems (HIPERMAN). From 2001 to 2004, she was the technical project manager of the IST PRODEMIS project.
From 2003, she is task leader in the IST MAGNET project. She is presently project manager at CSEM and her areas of expertise
are in ASIC design, digital and mobile communications. She published conference and magazine papers. 相似文献