共查询到16条相似文献,搜索用时 140 毫秒
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在分析多载波CDMA(MC-CDMA)技术原理的基础上,利用优化的多带复小波作为多载波调制以及turbo 编码作为信道编码,提出一种基于优化多带复小波和turbo编码的MC-CDMA系统,研究了其在瑞利衰落信道下的误比特率性能。该系统能克服通常MC-CDMA系统插入循环前缀(CP)所带来频谱效率的降低,并能充分利用turbo 码的良好抗信道衰落能力,进一步提高系统性能。理论分析和仿真结果表明该系统性能要好于通常MC-CDMA系统,具有与采用CP的MC-CDMA系统相比较的优势。同时turbo编码的应用显著增强了系统抗多径衰落和多址干扰的能力。 相似文献
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基于小波包函数的正交MC-CDMA及其性能 总被引:1,自引:0,他引:1
本文将小波包变换理论应用于多载波码分多址(MC-CDMA)系统,提出一种基于小波包函数的正交调制方法.系统中,发端数据串并转换成若干子信道,每个子信道的数据进行直序扩频,不同子信道上的数据以chip调制不同的小波包函数作为基带传输波形.小波包函数的一系列优良性质,使系统能有效地抗多径干扰,抑制子信道串扰、多址干扰等.本文对系统在多径Rayleigh慢衰落信道中的性能,进行了理论分析和计算机仿真.结果表明,本系统比基于DFT的MC-CDMA有较大的性能改善. 相似文献
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提出一种基于多带复小波和空时编码的多载波CDMA系统,研究了其在瑞利衰落信道下的误比特性能。理论分析和仿真结果表明该系统要明显优于通常MC-CDMA系统,具有与采用循环前缀(CP)的MC-CDMA相比较的优势,而且能够克服通常MC-CDMA系统插入CP所带来能量的减少和频谱效率的降低。同时空时编码技术的应用,显著增强了系统抗多径干扰和多址干扰的能力,进一步提高了系统性能。 相似文献
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基于神经网络均衡器的小波包多载波扩频系统 总被引:1,自引:0,他引:1
在多径衰落信道下,本文提出了一种基于神经网络均衡器的小波包多载波扩频系统(Neural Network Equalizers Wavelet Packet Spread Spectrum,NNE-WPSS).本文利朋基于最小均方算法(Least Mean Square algorithm,LMS)的复径向基函数神经网络均衡器(Complex Radial Basis Function Network Equalizers,CRBF)来抑制由多径衰落信道引起的码间干扰(Inter-Symbol Interference,ISI)并且利用最大似然算法对解调后的码元进行检测.在多径衰落信道和白高斯噪声情况下,本文分析了基于神经网络均衡器的新型小波包多载波扩频系统的传输性能.仿真结果表明,本文所提出的基于神经网络均衡器的新型小波包多载波扩频系统的性能要优于传统的基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)多载波扩频系统;本文提出的复径向基函数神经网络均衡器(CRBF)的性能也优于迫零均衡器(Zero-Forcing Equalizer,ZFE). 相似文献
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在分析多载波码分多址的原理基础上,利用优化生成的多带复小波,提出了一种基于优化多带复小波的多载波CDMA系统反向链路模型,并采用基于多天线的空间分集合并(SDC)技术进一步完善所提系统.该系统可利用优化多带复小波的优良特性来避免通常多载波CDMA由于插入循环前缀所带来的频谱效率的下降,在此基础上我们研究了所提系统采用空间分集合并技术时在瑞利衰落信道下的反向链路性能;给出相应的误比特率分析.理论分析和仿真结果表明采用基于最大比合并的SDC技术可显著提高所提系统抗空间衰落和各种干扰的能力,而且基于SDC技术的所提系统要好于同样基于SDC技术的通常多载波CDMA系统和基于实小波包的多载波CDMA系统. 相似文献
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目前,紧张的无线频谱资源已经使频谱利用率成为无线通信系统面临的重要问题。多载波调制技术能有效解决上述问题并以其高效的频谱利用率和良好的抗多径衰落性能成为4G的核心传输技术之一。本文提出一种基于导频信号和最大似然估计算法的离散小波包多载波调制系统。通过对导频信号的设计,获得信道状态信息,利用最大似然估计算出最优信道状态信息,最后利用基于迫零算法消除由多径衰落引起的码间干扰。通过理论分析和仿真验证,基于导频信号和最大似然估计的算法的离散小波包调制是值得考虑的多载波调制技术。 相似文献
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广义正交传输系统及其高效实现方法 总被引:1,自引:0,他引:1
基于子带变换理论构建的广义正交传输复用模型,不仅适用于TDMA、FDMA和CDMA多用户系统,也适用于像OFDM之类的多载波(MC)系统以及由OFDM与CDMA综合而成的MC-CDMA系统。该模型在结构上等效于均匀DFT滤波器组,可以采用FFT结合多相滤波器组的方式高效实现。本文实现的多载波系统具有子载波间隔可伸缩性特点,而复杂性与OFDM加窗处理相接近。在相同的仿真环境下得到的结果表明:基于软脉冲响应的多载波系统(MCSIS)误码率性能优于OFDM;对于相同衰落信道,MC-CDMA系统抗衰落特性明显优于OFDM。 相似文献
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Multi Carrier Code Division Multiple Access (MC-CDMA) is an appropriate modulation technique for high data rates. In this modulation scheme, employing of combining techniques are unavoidable for restoring orthogonality between different user signals. In this paper, the combining techniques of a MC-CDMA based on wavelet transform are studied. The partial combining of the wavelet based MC-CDMA system is suggested and its performance is compared with the maximum ratio combining (MRC), equal gain combining (EGC), orthogonality restoring combining (ORC) and the minimum mean square error (MMSE) techniques. Orthogonal filter banks of the wavelet transforms provide orthogonality between the wavelets and scaling functions, subcarriers and spreading sequences. Therefore, they provide new dimensions in combatting multipath fading, inter carrier interference (ICI) and narrowband interference in MC-CDMA systems. Furthermore, analysis of partial combining shows that coefficients of this technique can be computed in a simple manner. Simulations results indicate that the bit error rate (BER) performance of the proposed scheme is almost comparable with the MMSE combining scheme and the proposed system has a proper performance in terms of BER versus the signal to noise ratio (SNR) in frequency selective fading channels. 相似文献
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Yu Xiangbin Zhang Xiaodong Xu Dazhuan Bi Guangguo 《电子科学学刊(英文版)》2006,23(6):837-841
In this paper, a Complex Wavelet Packet (CWP-MC-CDMA) system uplink model is proposed, based Multi-Carrier Code Division Multiple Access based on the analysis of the principle of MC-CDMA and the use of the optimized complex wavelet packet. Considering that the base station can adopt multiple re- ceiver antennas in the uplink, we employ the Space Diversity Combining (SDC) technique to improve the sys- tem pertbrmance via multiple antennas. The uplink performance of proposed CWP-MC-CDMA system with SDC technique is investigated over Rayleigh lading channel, and corresponding bit error rate analysis is given in detail. The system can avoid the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix. Theoretical analysis and simulation result show that the application of SDC technique can improve the CWP-MC-CDMA system ability to combat spatial lading and various interferences effectively. Moreover, the proposed system based on SDC technique has superior Bit Error Rate (BER) performance over the Discrete Fourier Transform (DFT) and SDC based MC-CDMA system and the real wavelet packet and SDC based MC-CDMA system. 相似文献
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Performance of Multiband Complex-Wavelet-Based MC-CDMA System with Space-Time Coding over Nakagami-m Fading Channels 总被引:1,自引:0,他引:1
Xiang-Bin Yu Guang-Guo Bi Xiao-Min Chen 《Circuits, Systems, and Signal Processing》2010,29(3):539-552
Space-time coding technique and Multi-carrier CDMA (MC-CDMA) technique have received much interest due to their high frequency
spectrum efficiency and high data rate transmission. On the basis of analyzing the two technique principle, utilizing the
optimized multiband complex wavelet as multi-carrier basis function, we propose an MC-CDMA system based on multiband complex
wavelet and space-time coding for downlink and investigate the system bit error rate (BER) performance over Nakagami-m fading channel. The system has much higher spectrum efficiency and data rate due to no need any cyclic prefix (CP) when compared
to the conventional MC-CDMA system. Moreover, the application of space-time coding technique improves the ability against
fading channel effectively and perfects the downlink performance further. Simulation results show that the proposed multiband
complex-wavelet-based MC-CDMA (MBCW-MC-CDMA) system performs better than conventional MC-CDMA system and real wavelet-packet-based
MC-CDMA system due to its superior ability against interferences. Especially, the space-time coded MBCW-MC-CDMA system has
superior performance, and it outperforms single antenna MBCW-MC-CDMA and conventional MC-CDMA with space-time coding. 相似文献
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Belal A. Al-fuhaidi Hossam Eldin A. Hassan Moataz M. Salah 《Wireless Personal Communications》2014,74(2):439-456
Modern wireless communications require an efficient spectrum usage and high channel capacity and throughput. Multiple-input and multiple-output (MIMO), Linear equalizers, multi-user detection and multicarrier code-division multiple access (MC-CDMA) are possible solutions to achieve spectral efficiency, high channel capacity, eliminate multiple access interference (MAI), eliminate Inter symbol interference (ISI) and robustness against frequency selective fading. In this paper, we combine all these techniques and investigate BER performance. We propose a low complexity receiver structure for Single-input Multiple-output (SIMO) downlink MC-CDMA systems. It employs an interference cancellation scheme to suppress the interference caused by the multipath fading channel. Also, the proposed scheme is developed for MIMO MC-CDMA system. The performance analysis of Downlink MIMO MC-CDMA systems with V-BLAST over frequency selective fading channel is investigated under various number of transmit and receive antennas. The simulation results show proposed SIMO equalization with parallel interference cancellation scheme is effective in reducing the ISI and the MAI. It improves the performance significantly and the simulation results show that MIMO MC-CDMA with V-BLAST multi-user detection provides high data rate and the BER significant improvement. 相似文献
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混合DS-SFH扩频多址室内无线数字通信性能分析 总被引:3,自引:0,他引:3
本文讨论了DS-SFH扩频多址室内无线通信系统在瑞利多径衰落信道中的平均差错概率和多址容量。基于多径干扰、多址干扰和信道噪声的机理分析,推导了计算平均差错概率的有效近似公式。理论分析和数值模拟指出:混合系统的DS部分具有良好的多址容量并提供抗来自指定用户的多径干扰能力,混合系统的FH部分则具有抗来自非指定用户的多址和多径干扰能力。 相似文献
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The reverse link performance of hierarchical wideband multicarrier code-division multiple-access (MC-CDMA) systems is studied. An MC-CDMA system divides the system bandwidth into several equal narrow subbands that are used to transmit multiple signal waveforms in parallel. MC-CDMA systems are known to be robust to multipath fading and narrowband interference. We propose a hierarchical MC-CDMA system where the microcell(s) occupies a fraction of the available subbands. It is shown that such an architecture is a viable way of supporting microcell traffic while protecting the existing macrocell traffic. The effects of microcell Nakagami fading and power control error are also studied. 相似文献