共查询到20条相似文献,搜索用时 78 毫秒
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通过介绍UWB技术的发展现状,着重阐述了MB-OFDM UWB通信系统的物理层帧结构和信道模型。在分析最小二乘(LS)信道估计算法和基于快速傅里叶变换(FFT)信道估计算法的基础上,针对MB-OFDM UWB信号帧结构特征提出了一种基于FFT变换和Hannan-Quinn(HQ)准则的改进算法,即FFT-HQ信道估计算法。该文也提出了一种基于信道估计的自适应均衡算法,利用仿真可以看出此均衡算法在性能上优于传统的基于LS算法调整均衡器系数的方法。 相似文献
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基于OFDM-UWB系统信道估计方法的研究 总被引:1,自引:1,他引:0
介绍了基于正交频分复用的超宽带(OFDM-UWB)系统的结构,详细分析了常用的几种信道估计方法,并通过系统仿真比较对这几种方法进行了比较。仿真结果表明,基于时域的信道估计算法在估计效果和实现方面都相对优良。 相似文献
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隐藏系统具有估计精度差的缺陷,辅助导频具有占用带宽多的缺陷,针对这种情况提出了复合导频信道估计方法,在隐藏导频中插入极少量的辅助导频,由于UWB信道是慢变信道,所以隐藏导频可以借鉴辅助导频的信道估计。把辅助导频和隐藏导频的信道估计叠加成新的信道估计。仿真结果表明复合导频信道估计继承了两种导频信道估计的优点,提高了信道估计精度,减少了带宽占用率。 相似文献
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在宽带移动环境下,由于多普勒频移以及多径的影响,信道是时变的。为了消除信道对传输信号的影响,需要对信道进行估计。给出了2种基于离散余弦变换(DCT)的信道估计方法,可以很好的降低频谱泄露造成的混叠失真,适用于非整数倍的抽样信道。其中一种性能较好,另一种实现更加方便。仿真结果表明,这两种算法的性能均优于基于DFT的信道估计算法。 相似文献
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OFDM系统中基于变换域的信道估计 总被引:1,自引:0,他引:1
研究了正交频分复用(OFDM,orthogonal frequency division multiplexing)系统中基于变换域补零的插值方法,深入分析了基于离散余弦变换(DCT)的插值法,利用DCT的能量压缩特性,能有效消除传统基于离散傅里叶变换(DFT,Discrete Fourier Transform)估计算法在信道延时不是采样周期整数倍时产生的频谱能量泄露的问题。针对如何降低导频信道响应估计值中的噪声分量,提出了一种改进的方法,设计了一种适用于DCT变换域的滤波器,通过仿真系统参数变化对改进算法性能的影响,分析和验证了改进算法的有效性。 相似文献
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在MB-OFDM UWB 系统中,传统的信道估计方法没有充分利用信道长度这一信息,估计信道长度常大于实际长度,造成了性能损失。针对这一缺陷,提出一种新的信道估计算法。首先利用LS 算法估计出信道,然后通过信号能量估计(SEE)方法估计出信道长度。算法有效地降低了估计维数,因此提高了LS 算法的估计性能,同时对各算法的性能进行了分析比较。最后利用实验仿真证实了算法的有效性和分析的正确性。 相似文献
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L. K.K. Y.M. L. R.S. 《AEUE-International Journal of Electronics and Communications》2006,60(7):513-520
In a code-division multiple-access (CDMA) system, multiuser detection (MUD) can exploit the information of signals from other interfering users to increase the system capacity. However, the optimum MUD for CDMA systems requires the solution of an NP-hard combinatorial optimization problem. It is well known that the computational complexity of the optimum multiuser detector is exponential with the number of active users in the system. In this paper, we apply a hybrid algorithm to develop a suboptimal MUD strategy. The result of symmetric successive overrelaxation (SSOR) preconditioned conjugate-gradient method is first used to initialize the reduced-complexity recursive (RCR) multiuser detector. Then, RCR algorithm is applied to detect the received data bit by optimizing an objective function in relation with the linear system of decorrelating detector. Simulation results for the synchronous case show that the performance of our proposed SSOR-RCR multiuser detector is promising and outperform the decorrelator and linear minimum mean squared error multiuser detector with lower computational complexity. 相似文献
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信道编码是OFDM系统的关键技术之一,低密度格码(Low Density Lattice Codes, L
DLC)则是一种能高效译码且达到AWGN信道容量的新型编码技术,它兼具格码和低密度奇偶
校验码(Low Density Parity Codes, LDPC)的特点。基于LDLC码编译码原理,给出了LDLC
码作为前向纠错编码技术应用于OFDM系统的方案,在MATLAB平台下仿真研究了LDLC-OFDM系
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在Rayleigh衰落信道下的性能,结果表明LDLC码很大程度地改善了OFDM系统的误码率性能,
且优于LDPC码。 相似文献
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We propose a novel approximate lower triangular structure for the parity part of the parity-check matrix of QC-LDPC codes. About half of the non-zero elements in the parity part are set to locate on the upper diagonal while the remaining non-zero elements can be located almost anywhere within the lower triangular area, provided certain rules are observed. Compared with the typical dual-diagonal structure, the proposed structure requires very similar encoding complexity and produces lower error rates over an AWGN channel. 相似文献
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针对柱面共形阵列的波达方向(DOA)估计问题,从信号子空间的角度分析了在阵元遮挡下应用多重信号分类(MUSIC)算法的性能缺陷。在此基础上提出通过偏置常数的方法克服经典MUSIC算法的阵元遮挡问题。进一步提出一种基于数据自适应子阵分割的快速DOA估计算法,该方法先利用稀疏采样的偏置MUSIC算法进行DOA预估,依此确定所需要的子阵及二维搜索区域,确定MUSIC算法的搜索范围,进而得到高精确度的DOA估计。利用子阵分割的方法进行DOA估计,避免了经典MUSIC算法因阵元遮挡导致运算量大、精确度低等问题。仿真结果表明,该方法能大幅度降低运算复杂度,同时提高DOA估计精确度。 相似文献
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Mingbo Zhu 《电子科学学刊(英文版)》2008,25(6):774-779
In this paper, the design and implementation of a high performance Ultra-WideBand (UWB) Linear Frequency Modulation (LFM) waveform generator at Very High Frequency/Ultra High Frequency (VHF/UHF) band are introduced. Firstly, the design ideas for a high performance UWB LFM waveform generator are described. Then, a generation scheme for UWB LFM waveforms is presented according to the baseband digital generation method combining with the bandwidth extension method via frequency doubling. An experimental system has been implemented and tested. The results show that the UWB LFM waveform generator achieves very high performance. 相似文献
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Jin Young Lee Ho-Cheon Wey Du-Sik Park 《Journal of Visual Communication and Image Representation》2012,23(8):1179-1188
The H.264/AVC video coding standard can achieves higher compression performance than previous video coding standards, such as MPEG-2, MPEG-4, and H.263. Especially, in order to obtain the high coding performance in intra pictures, the H.264/AVC encoder employs various directional spatial prediction modes and the rate-distortion (RD) optimization technique inducing high computational complexity. For further improvement in the coding performance with the low computational complexity, we introduce a sampling-based intra coding method. The proposed method generates two sub-images, which are defined as a sampled sub-image and a prediction error sub-image in this paper, from an original image through horizontal or vertical sampling and prediction processes, and then each sub-image is encoded with different intra prediction modes, quantization parameters, and scanning patterns. Experimental results demonstrate that the proposed method significantly improves the intra coding performance and reduces the encoding complexity with the smaller number of the RD cost calculation process. 相似文献
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The performance of a joint rake and minimum mean square error (MMSE) equalizer receiver for high data rate ultra-wideband communications is studied in this paper. The proposed receiver combats inter-symbol interference by taking advantage of the rake and equalizer structure. The receiver performance is investigated using a semianalytical approach and Monte-Carlo simulation. The effects of the number of rake fingers and equalizer taps on the error performance are examined. 相似文献
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Caixia Chen Manh Anh Do Kiat Seng Yeo Chirn Chye Boon 《Analog Integrated Circuits and Signal Processing》2011,68(1):77-84
A new transmitter for ultra-wideband (UWB) impulse radio is described in this paper. The new UWB transmitter implements a
low power Gaussian shaping filter to reduce the side-lobe in the frequency domain. A simple pulse amplitude modulation (PAM)
circuit is used to keep the power consumption low. The proposed architecture features the simple design, low-power operation,
and enables the pulse-shape generation for a multi-channel UWB. The core layout size is only 0.2 mm2. The simulation results show that the generated signals satisfy the FCC spectrum mask, and the average power consumption
is <1.97 mW for the 1.8 V supply voltage. Pulses are transmitted at a PRF (pulse repetition frequency) of 40.5 MHz in 500 MHz
bandwidth channels equally spaced within the 3.1–10.6 GHz UWB. This transmitter is designed and fabricated in a 0.18-μm CMOS
process. 相似文献
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Nikos Dimokas Dimitrios Katsaros Leandros Tassiulas Yannis Manolopoulos 《Wireless Networks》2011,17(3):717-737
During the last decade, Wireless Sensor Networks have emerged and matured at such point that they currently support several
applications such as environment control, intelligent buildings, target tracking in battlefields. The vast majority of these
applications require an optimization to the communication among the sensors so as to serve data in short latency and with
minimal energy consumption. Cooperative data caching has been proposed as an effective and efficient technique to achieve
these goals concurrently. The essence of these protocols is the selection of the sensor nodes which will take special roles
in running the caching and request forwarding decisions. This article introduces two new metrics to aid in the selection of
such nodes. Based on these metrics, we propose two new cooperative caching protocols, PCICC and scaPCICC, which are compared against the state-of-the-art competing protocol, namely NICoCa. The proposed solutions are evaluated extensively in an advanced simulation environment and the results confirm that the
proposed caching mechanisms prevail over its competitor. The evaluation attests also that the best policy is always scaPCICC, achieving the shortest latency and the least number of transmitted messages. 相似文献