共查询到18条相似文献，搜索用时 968 毫秒
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在分析空时编码技术和多载波CDMA技术原理的基础上,采用turbo编码作为信道编码以及优化的复小波包作为多载波调制,提出一种基于复小波包和turbo码的空时分组编码的MC-CDMA系统,研究了其在瑞利衰落信道下的误码率性能.该系统能充分利用空时分组编码的发送分集和turbo码的良好抗信道衰落能力显著提高系统性能,而且还能利用优化复小波包的优良特性避免通常MC-CDMA系统由于插入循环前缀(CP)所带来频谱效率的降低.仿真结果表明,基于复小波包的空时分组编码的MC-CDMA系统要好于空时分组编码的通常MC-CDMA(STBC-MC-CDMA)系统,略好于采用CP的STBC-MC-CDMA系统;级联turbo码的空时编码技术的应用进一步增强了系统抗衰落信道下的各种干扰能力. 相似文献
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叶卓映 《廊坊师范学院学报(自然科学版)》2014,14(6)
提出一种新的MIMO传输技术,即在发射端(基站)使用最大比发射,接收端使用两根接收天线并采用恒模等增益合并接收,记作MRT/EGC(Maximal-Ratio Transmission/equal gain combiner).利用随机矩阵理论,推导出瑞利衰落信道下MRT/EGC系统多进制相位调制的误符号率的确切表达式.仿真试验验证了理论分析的正确性. 相似文献
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《绵阳师范学院学报》2021,(2):22-27
我国是世界上煤炭开采大国,由于煤炭开采环境的特殊性,矿井下的无线通信环境与地面的无线通信环境相差甚远,若直接将用于广阔空间的无线通信技术应用到煤炭矿井中会产生无线信号的多径衰落等不可预期的问题,严重影响矿井下的无线通信质量.本文首先从理论上分析了煤炭矿井中多径无线信道的复杂性,并采用瑞利多径信道模型对其进行仿真建模.采用无线通信中多输入多输出技术(MIMO)和正交频分复用技术(OFDM),设计了一套基于MIMO-OFDM的矿井无线通信系统,以减少多径衰落现象对无线信号的消极影响.最后通过MATLAB软件对该系统进行仿真分析,实验结果证明本系统具有抗多径衰减的功能. 相似文献
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基于最优小波包基的信号去噪算法 总被引：7，自引：0，他引：7
提出了一种基于最优小波包基的信号去噪算法,该算法以小波包分析为基础,根据最小代价原理搜索信号分解的最优基,然后对高频和低频系数采用不同的阈值算法进行量化,用量化后的系数重构得到去噪后的信号.实验结果表明该算法对于信号去噪是十分有效的. 相似文献
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研究了信道估计的均方误差,利用无限长、非因果的维纳滤波器推导出了它的下界.通过对不同衰落信道多普勒谱的积分,求出了相应的信道估计均方误差下界的闭合表达式,并在此基础上得到了分集系统在独立同分布的衰落信道中采用最大比合并时的误码率下界.数值分析结果表明,非理想信道估计下最大比合并的误码率性能是以理想信道估计的结果为下界,并随着最大多普勒频移的增加或信道估计信噪比的减小而逐渐劣化. 相似文献
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基于最优小波包基的信号去噪方法研究 总被引：1，自引：0，他引：1
冯宏亮 《西安文理学院学报》2009,12(2):60-63
改进了基于最优小波包基的信号去噪算法,该算法以小波包分析为基础,根据最小代价原理搜索信号分解的最优基,然后对高频和低频系数采用不同的阈值算法进行量化,用量化后的系数重构得到去噪后的信号． 相似文献
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刘献民 《天津工程师范学院学报》2009,19(4)
将离散小波变换(DWT)和离散多小波变换(DMWT)方法用于子带抽样图像水印技术中,并对其性能和采用离散余弦变换(DCT)方法的性能进行了对比分析.仿真结果表明,在DWT和DMWT两个变换域嵌入水印后能获得较好的图像质量.在DMWT域嵌入水印有较DCT和DWT域更好的图像质量效果和更好的抵抗通常图像处理攻击的能力. 相似文献
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自适应调制技术能有效地利用系统有限的功率和频谱资源,改善系统的误码率性能．针对资源受限的水声MC-CDMA系统提出一种自适应的调制算法．采用该方案的自适应水声MC-CDMA系统在获得有效频谱效率和分集增益的同时,还能获得很好的误码率性能．分析了提出的自适应调制算法的性能,并通过MATLAB系统仿真,表明自适应调制算法较非自适应调制可以使系统性能有明显的提高,说明了自适应调制技术在水声MC-CDMA中的有效性． 相似文献
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研究了多用户场景下多载波码分多址系统（MC—CDMA）的下行信道和功率分配,并将吞吐最大化问题建模成一个混合整数优化问题．为了简化分析,将问题分成2个低复杂度的子问题：功率分配和信道分配．这2个子问题可分别被一个次最优自适应功率分配算法（APA）和一个最优自适应信道分配算法（ACA）解决．通过联合APA和ACA算法,进一步提出了一个自适应信道和功率的分配方案．仿真结果表明：与传统的均匀功率分配算法相比,提出的APA算法更加适用于MC—CDMA系统;此外,提出的自适应信道和功率分配方案可以显著地提高系统吞吐量性能． 相似文献
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A joint cooperation diversity and symbol mapping diversity （SMD） strategy is proposed for cooperative packet retransmission system with high-order modulation such as 16QAM. Substantial SER/BER （symbol error rate/bit error rate） gains result from multiple packet transmissions over independent paths and distinct bit-to-symbol mappings for each packet transmission. The SER/BER performance of relay assisted retransmission system is analyzed. Simulation results show that the joint-diversity strategy can provide more BER gains than other relaying strategies （i.e., decode-and-forward and constellation rearrangement relaying strategies） when no relay makes a decision error; but if some relays make decision errors, the joint-diversity strategy outperforms other relaying strategies only when the relays are closer to the source than to the destination. 相似文献
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A novel time-frequency domain interference excision technique is proposed. The technique is based on adaptive biorthogonal local discrete cosine transform (BLDCT). It uses a redundant library of biorthogonal local discrete cosine bases and an efficient concave cost function to match the transform basis to the interfering signal. The main advantage of the algorithm over conventional transform domain excision algorithms is that the basis functions are not fixed but can be adapted to the time-frequency structure of the interfering signal. It is well suited to transform domain compression and suppression of various types of interference. Compared to the discrete wavelet transform (DWT) that provides logarithmic division of the frequency bands, the adaptive BLDCT can provide more flexible frequency resolution. Thus it is more insensitive to variations of jamming frequency. Simulation results demonstrate the improved bit error rate (BER) performance and the increased robustness of the receiver. 相似文献
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INTRODUCTION In broadband wireless communication, thdelay spread caused by channel multi-path fadinwill usually introduce serious Inter-Symbol Interference (ISI) to the receiver. To counteract the ISIthe high-efficiency Orthogonal Frequency DivisioMultiplexing (OFDM) modulation first splits thhigh-rate data stream into a number of parallesub-streams and modulates them onto differenorthogonal sub-carriers and thus lower the symborate, and then add a Cyclic Prefix (CP) to the h… 相似文献
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Conventional OFDM transmission system uses a fixed-length Cyclic Prefix to counteract Inter-Symbol Interferences(ISI)caused by channel delay spreading under wireless mobile environment. This may cause considerable performance deterioration when the CP length is less than the channel RMS delay spread,or may decrease the system power and spectrum efficiency when it is much larger. A novel Orthogonal Frequency Division Multiplexing(OFDM)transmission scheme is proposed in this paper to adapt the CP length to the variation of channel delay spread. AOFDM-VCPL utilizes the preamble or pilot sub-carriers of each OFDM packet to estimate the channel RMS delay spread; and then uses a criterion to calculate the CP length,which finally affects the OFDM transmitter. As illustrated in the simulation section,by deploying this scheme in a typical wireless environment,the system can transmit at data rate 11.5 Mb/s higher than conventional non-adaptive system while gaining a 0.65 dB power saving at the same BER performance. 相似文献
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INTRODUCTION The technology of smart or adaptive antennawhich can increase capacity and range, and reducesmultipath propagation of mobile radio communi-cation system, has aroused great interest in recentyears (Haardt and Spencer, 2003; Bellofiore, 2002;Godara, 1997). Beamforming is a key technologyin smart antenna systems (SAS) and many differentadaptive beamforming algorithms have been pro-posed. Code division multiple access (CDMA)system will be applied in most mobile communi-… 相似文献
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The paper presents a modified least squares despread respread multitarget constant modulus algorithm(LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate(MBER)criterion.The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate(BER)of code division multiple access(CDMA)mobile communication system. In order to achieve adaptive update of weight vectors,a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance,capacity and near-far effect resistance of a given CDMA communication system. 相似文献