共查询到20条相似文献,搜索用时 187 毫秒
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研究了在多径瑞利衰落环境中,抽样定时误差对相位调制的时分双工(TDD)预均衡正交频分多路复用系统(OFDM)的误码率性能影响.给出了理想和非理想相位预均衡处理的误码率解析表达式,并进行了计算机仿真,仿真和理论分析相符.对于TDD相位预均衡OFDM系统,定时误差导致了解调数据的相位旋转,且系统性能随定时误差的增加呈加速恶化的趋势.与无定时误差的瑞利衰落性能上界相比,当归一化定时误差为1/8时,理想和非理想相位预均衡的性能分别损失了约1dB和3dB;归一化定时误差为1/4时,二者的性能均严重恶化且差距减小,这时候定时误差成为影响系统性能的主要因素. 相似文献
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基于虚拟时间反转镜的水声OFDM信道均衡 总被引:2,自引:0,他引:2
针对水声信道对正交频分复用(OFDM)系统带来的符号间干扰(ISI)问题,提出了虚拟时间反转镜(VTRM)信道均衡算法,该算法具有时间压缩特性和频域相位共轭特性,可以有效缩短信道长度,减小多途信道带来的相位畸变,采用匹配追踪(MP)算法估计信道冲激响应,可以精确的估计出水声信道的幅度、时延和相位信息,为虚拟时反信道均衡提供准确的信道信息,改进了传统匹配相关信道估计方法估计精度低、无法估计信道相位信息的缺点。仿真、水池和湖上实验结果表明,OFDM水声通信系统中,VTRM信道均衡技术性能优于被动时反镜(PTRM)信道均衡和最小平方(LS)信道均衡。 相似文献
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残留频偏会导致星座点发生旋转,而且这种旋转与时间有关,时间越长,旋转越大。若残留频偏长时间得不到校正,将会使星座点旋转到其他象限从而出现判决错误,使系统的性能急剧恶化。针对这个问题,提出了一种基于星座点特征的残留频偏跟踪算法。该算法要求在信道估计之后完成,并假定一个OFDM帧内的信道频率响应保持不变。该算法包括三个步骤,首先将每个OFDM符号的星座点划分为四个子集,然后对每个子集的均值求相位角获得相位误差,最后经环路滤波器输出一个校正量补偿时域频偏。由于残留频偏估计值的提取充分利用了所有数据子载波信息,并对每个子集进行了求均值处理,所以有效的改善了环路的输入信噪比。它适用于子载波为QPSK或QAM调制的OFDM系统,不同的子载波调制方式跟踪范围不同,最大跟踪范围为±0.05个子载波间隔。仿真表明:新算法性能要优于基于循环前缀的算法,与基于导频的跟踪算法性能相当。 相似文献
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J. C. Silva N. Souto F. Cercas R. Dinis A. Rodrigues A. Correia 《Wireless Personal Communications》2007,40(3):291-304
This paper focuses on the usage of Equalization-Based receivers for Wideband Code-Division Multiple Access (WCDMA) Multiple
Input, Multiple Output (MIMO) Bell Labs Layered Space Time (BLAST)-type systems. The main receivers on trial are the Zero-Forcing
and Minimum Mean Square Error (MMSE) algorithm-based receivers and their variants, employing Parallel interference cancellation
(PIC) and Iterative Partial Cancellation (IPC) schemes. To assess its performance in an existing system, the uncoded Universal
Mobile Telecommunications System (UMTS) High-Speed Downlink Packet Access (HSDPA) standard was considered (using solely QPSK
modulation) alongside the reference UMTS environments. The BER performance is assessed both by simulation and by semi-analytical
processing. 相似文献
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Li Lei Niu Zhisheng 《电子科学学刊(英文版)》2007,24(2):257-260
A spatial compatible user grouping algorithm is proposed to reduce CoChannel Interference (CCI) in Space Division Multiple Access (SDMA) multiuser Multiple Input Multiple Output (MIMO) systems. We evaluate the interferences among Users by use of distances between row spaces spanned by users' channel matrixes, then control frequency sharing according to the compatible user grouping algorithm. Results show that the row space distance algorithm outperforms others because it can fully utilize the information from users' channel matrixes, especially the matrix structure information. The results also prove that the algorithm based on channel matrix structure analysis is a better candidate for spatial compatibility approximation. 相似文献
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High Resolution Wide Swath (HRWS) Synthetic Aperture Radar (SAR) often suffers from low Signal-to-Noise Ratio (SNR) due to small transmitting antenna, especially in phased array antenna systems. Digital Beam Forming (DBF) based on Single Input and Multiple Output (SIMO) achieves receiving array gain at the cost of increasing data rate. This letter proposes a new HRWS SAR method, which employs intra-pulse null steering to get receiving gain in elevation and decrease the data rate, and Multiple Input and Multiple Output (MIMO) using Space-Time Block Coding (STBC) in azimuth to get transmitting gain and receiving array gain simultaneously. The feasibility is verified by deduction and simulations. 相似文献
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Wireless Personal Communications - The capacity of the radio link can be improved a lot by using modern wireless technologies like Multiple Input and Multiple Output (MIMO) technology. Successful... 相似文献