共查询到20条相似文献,搜索用时 375 毫秒
1.
This paper presents measured error-rate performance of binary FSK with discriminator detection in simulated Rayleigh fading with time delay spread. Measured relations between error rate and carrier-to-noise ratio are shown for a range of time delay spreads. We have verified that the effect of time delay spread on error rate can be described by only one parameter, the ratio of the rms delay spread to the transmitted baud time. Intersymbol interference from time delay spread causes an irreducible error rate for FSK, even for infinite carrier-to-noise ratio. For 64 kbit/s binary FSK, the 2.6μs rms delay spread typical of the urban environment produces an irreducible error rate of 3 percent. The measured irreducible error rate for binary FSK with discriminator detection is proportional to the fourth power of the ratio of rms delay spread to baud time. This functional dependence is identical to that predicted analytically for FSK with incoherent matched-filter detection. 相似文献
2.
Ichitsubo S. Furuno T. Taga T. Kawasaki R. 《Vehicular Technology, IEEE Transactions on》2000,49(2):422-427
This paper proposes a multipath propagation model for line-of-sight (LOS) street microcells with building roof base sites (BS) in urban areas, Multipath propagation characteristics are of great importance in evaluating the performance of digital systems and designing wireless links. Typical delay profiles are measured to clarify their statistical characteristics in LOS street microcells. The channel sounder used is a sliding correlator with 30-Mb/s PN code and a center frequency of 2.6 GHz. The measurements clarify the features of delay profile and mean RMS delay spread. The proposed delay profile model explains one plausible mechanism of multipath propagation. The delay profiles calculated using the model agreed well with the measured profiles. Furthermore, the factors influencing the RMSs delay spread are investigated, and the regression equation of medium RMS delay spread on a sidewalk is established. The proposed model can evaluate the transmission characteristics of wireless digital communication systems in multipath propagation environments 相似文献
3.
Tai-Kuo Woo 《Wireless Personal Communications》2012,62(2):395-410
The Constant Modulus Algorithm (CMA) adopts the constant modulus (CM) criterion to minimize the deviation of the equalizer
output from a fixed value. However it has two drawbacks: (1) slow rate of convergence (2) the likelihood of getting trapped
in a local minimum. The problem gets even worse when the channel delay spread varies rapidly as the filter length cannot match
the delay spread. If the filter length is significantly longer than the delay spread, the convergence rate can be slow. In
this paper, we improve the performance of the standard CMA by using a dynamically partitioned hierarchical structure to organize
the taps of a filter. The filter length is dynamically partitioned according to the delay spread such that they are tightly
matched. Preferably, the length of a sub-filter is slightly longer than the delay spread of the channel. The performance evaluation
is divided into two parts. In Part I, we do simulation runs for both the cost functions and cost surfaces comparing the standard
CMA, where the filter length is significantly longer than the delay spread, and the dynamically partitioned CMA, where the
filter length matches the delay spread. In Part II, an analysis is provided to show that the proposed partitioned scheme can
speed up the convergence rate and reduce the cost function. 相似文献
4.
CCIR impairment is a subjective measure of the degradation of television images caused by ghosting. Delay spread is the standard deviation of the impulse response of a multipath channel. To compare the impairment and delay spread, measurements were taken of independent real channels through the use of widely spaced frequencies and decorrelated receiving patterns. The comparison shows that the log of the impairment and the delay spread are well correlated over the useful impairment range. The delay spread, an analytic parameter, thus provides an alternative for the more complicated and empirically-derived CCIR ghosting impairment measure 相似文献
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Tsioumparakis K.H. Doumi T.L. Gardiner J.G. 《Vehicular Technology, IEEE Transactions on》1997,46(3):664-675
In current analog cellular systems, same-frequency repeaters are very often used as gap fillers. With digital wideband systems, the use of a repeater, with its inherent group delay added to the differential propagation delay, may yield a degradation in the performance in view of the resulting delay spread. An approach to estimate the statistics of the delay spread when each link is subjected to lognormal shadowing and each channel's power-delay profile follows an exponential decay is presented. Expressions for the cumulative density function (CDF), mean value, mean-square value, and standard deviation for the RMS delay spread are derived, and their accuracy is verified through simulation 相似文献
7.
Suiyan Geng Kivinen J. Xiongwen Zhao Vainikainen P. 《Vehicular Technology, IEEE Transactions on》2009,58(1):3-13
This paper presents and analyzes the results of millimeter-wave 60-GHz frequency range propagation channel measurements that are performed in various indoor environments for continuous-route and direction-of-arrival (DOA) measurement campaigns. The statistical parameters of the propagation channel, such as the number of paths, the RMS delay spread, the path loss, and the shadowing, are inspected. Moreover, the interdependencies of different characteristics of the multipath channel are also investigated. A linear relationship between the number of paths and the delay spread is found, negative cross correlation between the shadow fading and the delay spread can be established, and an upper bound exponential model of the delay spread and the path loss is developed to estimate the worst case of the RMS delay spread at given path loss. Based on the DOA measurements that are carried out in a room [line of sight (LOS)] and in a corridor with both LOS and nonline-of-sight (NLOS) scenarios, radio-wave propagation mechanisms are studied. It is found that considering the direct wave and the first-order reflected waves from smooth surfaces is sufficient in the LOS cases. Transmission loss is very high; however, diffraction is found to be a significant propagation mechanism in NLOS propagation environments. The results can be used for the design of 60-GHz radio systems in short-range wireless applications. 相似文献
8.
基于室内视距(Line-of-Sight,LOS)和非视距(Non-Line-of-Sight,NLOS)无线信道测量数据,研究了28 GHz多输入多输出(Multiple-Input Multiple-Output,MIMO)信道参数和容量特性.具体地说,分析了莱斯K因子、时延扩展、出发角和到达角的角度扩展等信道参数,研究了MIMO信道容量及空间相关性对容量的影响.结果表明:莱斯K因子、时延扩展以及角度扩展值取决于测量环境及场景;LOS条件下时延扩展的累积分布函数(Cumulative Distribution Function,CDF)曲线与正态分布拟合优于NLOS条件下的数据;MIMO天线空间相关性越大信道容量越小.本文结果可为28 GHz无线通信系统设计提供有用信息. 相似文献
9.
Impulse response radiowave propagation measurements from an urban area of Denver, CO, are described. The basic transmission loss and delay spread are used to characterize the mobile communications environment. These metrics are quantified using path loss slope and delay spread statistics. By analyzing the results versus carrier frequency, the relative propagation impairments at 430, 1350, 2260, and 5750 MHz are compared. It was found that the path loss slope increased on average by 11 dB/dec and the median delay spread decreased from 0.7 to 0.3 /spl mu/s over the decade of frequencies measured. 相似文献
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Cheon C. Liang G. Bertoni H.L. 《Selected Areas in Communications, IEEE Journal on》2001,19(11):2191-2200
The design of advanced radio systems requires knowledge of higher order channel statistics, such as the time delay spread and the angle of arrival spread. Time delay has been measured in a number of cities, while angle of arrival has been measured in only a few. Since the link geometry is not the same for all measurements, it is not clear how to compare the measured values, or if they are applicable to other building environments, antenna height, etc. To clarify these issues, we have used a three-dimensional ray tracing code, called the vertical plane launch (VPL) method, to simulate time delay spread and angle of arrival spread in different building environments. Results for elevated base station antennas show that the distribution of root mean square (RMS) delay spreads is not sensitive to the statistical properties of the buildings but increases with distance to the mobiles and increases as the base antenna is lowered below the rooftops. In contrast, the distribution of RMS angle spread is sensitive to the distribution of building heights and to the height of the base station antenna but not to the distance to the mobile. The influence of street geometry on delay and angle spread for low base station antennas is also discussed 相似文献
12.
This paper studies the effects of time-delay spread on trellis-coded modulation (TCM) in portable radio channels, where equalization is not employed to mitigate frequency-selective fading. The average irreducible bit error rate (BER) of three different TCM schemes are analytically formulated first and then numerically evaluated by simulation. The results for a delay spread lower than 0.2 of the symbol period indicate that the performance of TCM schemes with interleaving/deinterleaving is much better than that of QPSK, and better TCM schemes for flat fading also give better performance under low delay spread. Analytical results indicate that a good TCM scheme in frequency-selective fading channels should have both a large Euclidean distance and a high degree of built-in time diversity. If higher time-delay spread is encountered, TCM does not have advantages over QPSK. We also compare TCM performance with and without diversity. It is found that diversity greatly improves the performance under low delay spread, while the diversity gain quickly diminishes as the RMS delay spread approaches 0.2 of the symbol period 相似文献
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A study of time dispersion in different indoor line-of-sight radio channels in the 492-862 MHz band is presented in this paper. A combined method to filter the noise in the measured impulse response is described. The effect of frequency windowing on the impulse responses and the root mean square (rms) delay spread is also investigated. It has been found that, in general, the use of windows with lower side-lobe levels yields larger values of the rms delay spread. The relation between the mean delay and the rms delay spread has also been studied for copolar and crosspolar channels. The dependence of the coherence bandwidth on the rms delay spread has been considered, and an inverse relation has been tested for both components 相似文献
15.
宽带UHF无线电波在隧道中的传播停产信道的特性 总被引:16,自引:1,他引:15
本文分析了宽带UHF无线电波在隧道中的传播特性。研究表明:在隧道全空和有障碍物时,Rms时延扩展分别不大于22ns和103ns。由此可知,隧道无线电波具有较宽的相关带宽,即使不进行补偿,也可支持每秒1Mbit的数据库。隧道无线电波传播信道与频率密切相关,频率超高,接收信号的起伏越大,Rms时延扩展也越大。 相似文献
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室内多径时延扩展的实验研究 总被引:3,自引:0,他引:3
本文介绍关于室内环境中时延扩散的实验,实验采用基于伪随机码滑动相关法的无线信道探测器,在典型的室内环境中对UHF(900MHz)无线信道功率时延曲线进行实地测量,通过对大量实测数据的处理和分析得出了一些很有价值的结论,如在LOS及NLOS情况下的时延扩展均方根值和方差;时延扩散与收发距离、路径损耗及收发天线不同线极化方向的关系等等。 相似文献
18.
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
19.
Wide-band measurements and characterization at 2.1 GHz while entering in a small tunnel 总被引:2,自引:0,他引:2
Molina-Garcia-Pardo J.-M. Rodriguez J.-V. Juan-Llacer L. 《Vehicular Technology, IEEE Transactions on》2004,53(6):1794-1799
The wide-band complex transfer function and propagation characteristics in a small passageway tunnel for nonline-of-sight are studied in this paper. A two-dimensional wide-band model based on the uniform theory of diffraction (UTD) and geometric optics (GO) is implemented and a network analyzer is used to perform measurements. In order to obtain the power delay profile, a correction factor is used, which adjusts the deviation caused by the windowing and zero padding performed in frequency domain. The UTD model predicts quite well the averaged path loss, power delay profile, root-mean-square (rms) delay spread and coherence bandwidth, even when the curved tunnel is approximated to two straight lines. Furthermore, it is shown that the position of the transmitter is crucial in the performance of the system: the path loss slope and rms delay spread are increased when the inclination of the transmitter is increased. In all cases, the rms delay spread is lower than 40 ns, where the coherence bandwidth decreases to 20 MHz. This parameter is proposed to estimate the excitation zone inside a tunnel. 相似文献
20.
This paper presents results of experiment and computer simulation based on a three-dimensional (3-D) ray-tracing method for various directional polarized antennas, where the effects of polarization, antenna directivity, and room size on delay spread (measured at 94 GHz) are investigated in the line-of-sight (LOS) indoor channel. These results indicate that the delay spread can be reduced significantly by the directional circularly polarized antenna. It is also found that the delay spread increases almost proportionally with the square root of the room floor area 相似文献