共查询到20条相似文献,搜索用时 625 毫秒
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Studies of digital transmission over typical urban and suburban mobile channels using simulations that employ a local area model for the time varying mobile channel impulse response are discussed. The digital transmission techniques of coherently detected and differentially coherent detected versions of quadrature phase-shift keying (QPSK), Gaussian minimum shift keying (GMSK), and coherently detected binary phase-shift keying (BPSK) over example mobile channels are presented. Two measures of performance are considered; the mean bit error ratio (and irreducible bit error ratio), which is used to compare the robustness of the various modulation methods to delay spread, and the outage probability, which provides a measure of the overall transmission quality as would be perceived by a user. Emphasis is placed on results obtained for GMSK, which is the modulation scheme to be employed in the Pan-European digital cellular mobile system. The effects of RMS delay spread on the mean bit error ratio, mean irreducible bit error ratio, and probability of outage are considered for different channel types 相似文献
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The intersymbol interference (ISI) produced by multipath channel delay spread can be approximated as Gaussian noise. The equivalent average signal-to-noise power ratio (SNR) is defined. Very simple expressions for average bit error rate (BER) due to delay spread are derived for linear quaternary DPSK (QDPSK) transmission with differential detection over mobile radio Rayleigh fading channels.<> 相似文献
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The bit error rate (BER) performances of variant delay multiple-access differential chaos-shift keying (VDMA-DCSK) communication
systems over a multipath fading channel with delay spread are investigated. The BER formula of the VDMA-DCSK over the fading
channel is evaluated. A two-ray Rayleigh fading channel model is used to simulate the VDMA-DCSK system. The theoretical and
simulation results are presented and they match each other, which supports the theoretical analysis. The multipath performance
of the VDMA-DCSK is compared with that of a benchmark coherent MA-CSK system and with that of an invariant delay MA-DCSK system.
The results show that in the multipath fading channel with delay spread environment the VDMA-DCSK system performance decreases
least. 相似文献
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《Vehicular Technology, IEEE Transactions on》1986,35(4):168-174
Digital mobile radio often suffers from fatal effects caused by frequency-selective fading, resulting in severe bit error rate (BER) degradation. The feasibility of digital mobile radio largely depends on the multipath-distortion tolerant capability of modulation technique. The BER performance is compared among four digital modulation techniques in a frequency selective fading channel with large multipath delay spread. In particular, taking the timing fluctuation of eye patterns due to delay distortion of a fading channel into account, the effect of sample timing on BER is analyzed. The analyses have revealed that BER performance markedly depends on the choice of sample timing, and also an interesting fact that BPSK is outstanding in the multipath-distortion tolerance, if coupled with adaptive sampling, and its BER curves remain almost the same as that of frequency-flat fading as long as multipath delay difference is less than a bit interval. 相似文献
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Current advances in multi-dimensional channel sounding techniques make it possible to evaluate performances of signal processing
algorithms in realistic conditions. By using channel impulse response measurement data collected in the real fields, link-level
performances of signal transmission techniques in the fields such as bit error rate (BER) and frame error rate (FER) performances
can be evaluated. This technique is called link-level simulation. Through statistical analysis of link-level simulation results,
system-level performances of the techniques such as geographical distribution of BER and FER in the area of interest can also
be evaluated. This technique is called system-level simulation. This paper focuses on link- and system-level performances
of a multiple-input multiple-output (MIMO) Turbo Equalizer in real fields. Methodologies for the link- and system-level simulations
using field measurement data are first presented. Results of link- and system-level simulations using two-dimensional channel
sounding field measurement data collected in Tokyo are then presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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初始判决指导的DS/CDMA最大似然检测算法 总被引:1,自引:1,他引:1
本文首先给出了多径异步多用户DS/CDMA系统的一种数学模型,得出了恒参信道下最大似然检测(MLSE)算法的一种新的表示形式,然后作者具体分析了以RAKE接收机作为衰落信道的匹配滤波器时,最大似然检测器的算法设计问题,分析指出,在多径环境下MLSE算法的复杂度和计算量与多径时延的分布有关,如果有用户时延扩散在一个信息码元之内,算法复杂度和恒参信道下相同,而其实现可以用状态中变的Viterbi算法来 相似文献
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Tantra J.W. Chuan Heng Foh Tinnirello I. Bianchi G. 《Wireless Communications, IEEE Transactions on》2007,6(9):3256-3267
In recent years, the physical layer data rate provided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the distributed coordination function (DCF), represents a limiting factor: the throughput efficiency drops as the channel bit rate increases, and a throughput upper limit does indeed exist when the channel bit rate goes to infinite high. These findings indicate that the performance of the DCF protocol will not be efficiently improved by merely increasing the channel bit rate. This paper shows that the DCF performance may significantly benefit from the adoption of two separate physical carriers: one devised to manage the channel access contention, and another devised to deliver information data. We propose a scheme, referred to as out-of-band signaling (OBS), designed to reuse (and remain backward compatible with) the existing 802.11 medium access control (MAC) specification. Performance evaluation of OBS is carried out through analytical techniques validated via extensive simulation, for both saturation and statistical traffic conditions. Numerical results show that OBS improves the throughput/delay performance, and provides better bandwidth usage compared with the in-band signaling technique employed by DCF. 相似文献
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本文首先给出了多径异步多用户DS/CDMA系统的一种数学模型,得出了恒参信道下最大似然检测(MLSE)算法的一种新的表示形式。然后作者具体分析了以RAKE接收机作为衰落信道的匹配滤波器时,最大似然检测器的算法设计问题。分析指出,在多径环境下MLSE算法的复杂度和计算量与多径时延的分布有关,如果用户时延扩散在一个信息码元之内,算法复杂度和恒参信道下相同,而其实现可以用状态数可变的Viterbi算法来实现。最后,本文用传统判决方法得出的初始判决信息缩减Viterbi算法的搜索空间,在保证一定性能的前提下,算法的计算复杂度大大降低。 相似文献
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《Communications, IEEE Transactions on》1997,45(11):1444-1455
In order to mitigate narrow-band interference in spread spectrum communications systems, novel communications receivers incorporating transform domain filtering techniques are designed. In this paper, lapped transforms are used to transform the received data signal to the transform domain wherein adaptive excision is performed. Transform domain detection algorithms, which yield bit decisions based on the remaining signal energy, are analyzed and, together with excision, are employed on a block-by-block basis to suppress single-tone and narrow-band Gaussian interference. System performance is analytically quantified in terms of the overall system bit-error rate (BER). Subsequent results are presented for a variety of channel conditions and compared to those obtained using excision algorithms based on orthonormal block transforms (Medley 1995). These results demonstrate the improved performance and increased robustness with respect to jammer frequency and bandwidth of lapped transform domain excision techniques relative to similar algorithms based on nonweighted block transforms 相似文献
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This paper analyses the effect of signal combination techniques in videowatermark detection. A spatial spread spectrum based watermarking techique isused as embedding method, in combination with common error correction codes(BCH, Reed-Solomon with multilevel signaling, binary convolutional codes withViterbi decoding). Besides an analytical evaluation of the bit error rate, theeffectiveness of the channel coding and diversity techniques is also assessedexperimentally under MPEG-2 video compression. 相似文献
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Gen-kwo Lee Michael P. Fitz Saul B. Gelfand 《International Journal of Wireless Information Networks》1995,2(1):41-54
This paper applies the Bayesian conditional decision feedback estimator (BCDFE) to rapidly fading frequency selective channels. The BCDFE is a model-based deconvolution algorithm which jointly estimates the transmitted data and channel parameters. The BCDFE smoothly transitions between trained and blind operation and consequently provides robust performance in rapidly fading channels. We provide a brief derivation of the BCDFE and characterize the performance on the land mobile radio channel. We assess the BCDFE's principle design characteristics and the resulting performance in both transient and steady-state operation. The effects of delay spread, Doppler spread, and cochannel interference on the bit error probability performance are also presented. The BCDFE demonstrates many of the desirable characteristics of an equalizer for mobile radio. 相似文献
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Computer simulation results are presented of a study of delay spread on digital modulations with different constellations in a quasi-static multipath radio channel. Unfiltered 2-, 4-, and 8-PSK and 16-QAM with a rectangular signaling pulse are compared first, followed by 4- and 16-QAM with a raised-cosine Nyquist pulse. The bit error rate performances averaged over fading samples under the influence of the intersymbol interference caused by delay spread are compared for modulations of different levels. It is found that 4-level modulation is the most desired method for both performance and implementation in a quasistatic, frequency-selective fading radio channel. Both the spectral and the power efficiencies can be enhanced using Nyquist signaling pulses 相似文献
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Chien‐Ching Chiu Shi‐Cheng Hung Chien‐Hung Chen 《International Journal of Communication Systems》2002,15(8):701-711
Wideband communication characteristics of wireless indoor millimetre‐wave channel for arched and rectangular buildings are investigated. The impulse responses of arched and rectangular buildings for any transmitter–receiver location are computed by shooting and bouncing ray/image (SBR/Image) techniques. By using the impulse responses of these multipath channels, the impact of shapes of building is presented and the bit error rate performance of binary phase shift keying (BPSK) system with phase and timing recovery circuits are also calculated. Moreover, dual space antenna diversity technique and decision feedback equalizer (DFE) with four forward and three feedback taps are used to combat the multipath fading. Numerical results show that the mean root mean square (rms) delay spread for the arched building is smaller than that for the rectangular building. In addition, it is also found that the transmission rate can be up to 20 Mbps for indoor millimetre‐wave channel of these two buildings by using dual space diversity and DFE. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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报道了31位声表面波可程序匹配滤波器的结构、设计和性能参数。声表面波可程序抽头延迟线是近年来快速发展的直扩技术广泛应用的一种器件。它的强大信号处理能力和极高的运算速度,使得直扩序列信号的快速同步及匹配滤波较传统的技术大为简化。文章报道的31位声表面波低频可程序抽头延迟线是一种用于扩频抗干扰通信系统所用的关键信号处理器件。在研制过程中,采用的COMS/SOS等新技术以及分裂抽头等新设计,使器件的时钟速率和主旁瓣比关键技术指标获得了较大的提高,完全满足系统要求 相似文献
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Peter Kuczynski Arnaud Rigoll Wolfgang H. Gerstacker Johannes B. Huber 《AEUE-International Journal of Electronics and Communications》2004,58(4):256-267
In this paper, a Hidden Markov Modeling (HMM) technique for a fast and accurate simulation of bit errors and soft outputs in wireless communication systems is presented. HMMs with continuous probability distributions are considered. Soft outputs and bit errors are combined to error patterns. We focus on binary phase–shift keying (BPSK) modulation for direct–sequence spread spectrum (code–division multiple access, CDMA) transmission as proposed e.g. for the third generation wireless communication system UMTS (uplink for the frequency division duplex mode (FDD)). Comparisons of simulated bit error rates for HMM models and Rake receivers are shown for AWGN, flat fading, and vehicular channel conditions. In order to assess the ability of the HMM to describe the dynamical behaviour of the channel a comparison for transmission with interleaving and convolutional coding is presented. Furthermore calculated autocorrelation functions of the error patterns and error gap distributions corresponding to the Rake receiver and to the HMM, respectively, are presented. Our investigations show a strong dependence of the required HMM order on Eb/N0 and the channel conditions. The degree of accordance of the HMM outputs and the training data is examined based on calculated statistical scoring indicators. 相似文献
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A novel completion detection technique for delay insensitive current sensing on-chip interconnects is presented. The scheme is based on sensing currents on the data wires and comparing the sum of these currents to an appropriately set reference. The goal is to solve the performance bottleneck caused by conventional voltage-mode detection methods. With the channel width of 64 bits, the proposed method is 4.65 times faster and takes 36% less area than the voltage-mode scheme. Furthermore, its speed does not degrade when increasing the channel bit width. It is implemented in a 65 nm CMOS technology. 相似文献