共查询到17条相似文献,搜索用时 315 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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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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基于空时分组编码的发射分集技术利用空间和时间分集 ,能有效抗多径 ,增强信道可靠性。将空时分组编码应用到MC -CDMA下行链路中 ,构建了一种新的多载波CDMA系统 (ST -MC -CD MA) ,通过在每个子载波信道中获得空间分集增益来提高系统性能。具体实现时 ,依据传统MC -CDMA信号合并方案 ,提出了ST -MC -CDMA空时译码后相应的四种合并方案。仿真结果验证了这 4种合并方案的优、缺点 ;并进一步证明 :在频率选择性瑞利衰落信道中 ,该系统比采用相同合并方案的传统MC -CDMA有明显的性能改善。 相似文献
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提出一种通用的多载波频率分集CDMA系统基带发射、瑞利信道以及相关接收的矩阵信号分析模型。通过分析可以看出,多载波频率分集CDMA系统是一种高效的并行调制技术,它使信道和信号之间的卷积关系变成了线性加权关系,有效地抑制了符号间干扰和码间干扰,同时还具有频率分集的优点。对多载波频率分集CDMA系统在BPSK调制下的理论误码性能进行了深入探讨,给出了一种新颖的单用户系统和多用户系统的误码率分析方法。通过高斯近似法和Monte-Carlo模拟方法得到的数值仿真结果表明:瑞利衰落信道下,多载波频率分集CDMA具有良好的抗多径效果:随着用户数的增加,系统性能下降;在无线宽带数据业务传输中的性能大大优于CDMA,应用前景广阔。 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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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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Xiangbin Yu Xiaodong Zhang Dazhuan Xu Guangguo Bi 《Wireless Personal Communications》2007,41(2):193-206
In this paper, the multiband complex wavelet used as multi-carrier basis function is optimized. On the basis of analyzing
the principle of multi-carrier code division multiple access (MC-CDMA), a new multiband complex wavelet based MC-CDMA (MBCW-MC-CDMA)
system model is proposed, and space diversity combining (SDC) technique is employed to improve the system performance further.
The uplink performance of proposed MBCW-MC-CDMA system with SDC technique is investigated in Rayleigh fading channel, and
corresponding bit error rate (BER) analysis is given in detail. Without any cyclic prefix (CP), the system can avoid the decrease
of spectrum efficiency and data rate of conventional MC-CDMA with CP. By comparison, our scheme outperforms real wavelet packet
based MC-CDMA and slightly outperforms conventional MC-CDMA with CP via utilizing superior properties of the optimized multiband
complex wavelet. Theoretical analysis and simulation result show that the application of SDC technique can improve the proposed
system ability to combat spatial fading and various interferences effectively. Moreover, the proposed system based on SDC
technique has superior BER performance over conventional DFT and SDC based MC-CDMA system and real wavelet packet and SDC
based MC-CDMA system.
Xiangbin Yu received the M.S degrees in Communication and Information Systems from Hohai University, Nanjing, China, in 2001; and his
Ph.D. in Communication and Information Systems in 2004 from National Mobile Communications Research Laboratory at Southeast
University, China. Now he is working as a Postdoctoral Researcher in Information and Communication Engineering Postdoctoral
Research Station at Nanjing University of Aeronautics and Astronautics, Nanjing, China. His research interests include multi-carrier
digital communication, space-time coding and digital signal processing in modern communications.
Xiaodong Zhang received the M.S degrees from Nanjing University of Posts and Telecommunications, Nanjing, China, in 1998. In 2002, he received
the Ph.D. degree from Southeast University, Nanjing, China. His research interests include contemporary signal processing
and digital communications.
DaZhuan Xu received the M.S degrees and Ph.D. in Communication and Information Systems from Nanjing University of Aeronautics and Astronautics
in 1986 and 2001, respectively. He is now a full professor in Nanjing University of Aeronautics and Astronautics, Nanjing,
China. Prof.Xu is a Senior Member of China Institute of Electronics (CIE). His research interests include digital communications,
soft radio, coding theory, medical signal processing.
Guangguo BI was graduated from Nanjing Institute of Technology, Nanjing, China, in 1960. He is now a professor in the Department of Radio
Engineering of Southeast University, Nanjing, China. Prof.Bi is a fellow and a member of the board of Director of the China
Institute of Communications, and a senior member of IEEE. His research interests include digital communications, personal
communications network, spread spectrum communications, and intelligent information processing. He has published more than
200 papers in above areas. 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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《AEUE-International Journal of Electronics and Communications》2014,68(4):291-300
Different kinds of Multirate (MR) communication systems, such as multicode (MCD) scheme and variable spreading length (VSL) schemes, have been considered for accommodating information sources with different data rates in Multicarrier code-division multiple access (MC-CDMA). In this paper, we propose the use of MCD scheme for MR services in MC/MCD-CDMA system that employs wavelet packets (WPs) as subcarriers. The bit error rate (BER) performance for the system was investigated by means of analytical methods and numerical results in a slow fading frequency selective Nakagami channel. The performance analysis includes the effects of diversity techniques, channel intensity profile, diversity order and fading parameter. Also, the effects of different service rates and number of users in each service rate were investigated. The performance of the system was compared to that of MC/MCD-CDMA based on sinusoidal carrier. Results reveal that BER performance is proportional to the service rate and our proposed system outperform the other system. 相似文献
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Oui Suk Uhm Soon Young Yoon Hwang Soo Lee 《Electronics letters》1996,32(2):89-91
A practical coherent detection scheme for biorthogonal signals over Rayleigh fading channels is proposed. The proposed scheme improves the bit error rate (BER) performance compared to the noncoherent detection schemes for biorthogonal signals. It also outperforms the coherent and noncoherent detection schemes for orthogonal signals with comparable bandwidth efficiency. The BER performance for a Rayleigh fading channel with two path diversity combining is obtained by computer simulation. The results show that the required average signal-to-noise ratio per bit γb can be reduced by as much as 1.4 dB when we use this system in the CDMA cellular reverse link 相似文献
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An implementation of a reverse link receiver for IS-95 CDMA (Code-Division Multiple-Access) communications that applies decision feedback to the decoding of the received signal is presented. Decision feedback is used in order to improve BER performance by making use of additional information that conventional receiver designs generally ignore. Qualitative analysis and computer simulation of the hardware components of the proposed implementation shows that it can be built as a single integrated circuit using present day technology. The design presented here does not include the RF front-end of the receiver, does not consider the effects of multipath and fading on system performance, and assumes perfect power control. 相似文献