共查询到20条相似文献,搜索用时 15 毫秒
1.
Durgin G.D. Kukshya V. Rappaport T.S. 《Antennas and Propagation, IEEE Transactions on》2003,51(5):936-944
The paper presents spatio-temporal measurements for the peer-to-peer radio channel at a center frequency of 1920 MHz with 140 MHz of radio-frequency bandwidth. The measurements were taken using a spread-spectrum channel sounder and an automated spatial probing system that uses precise computer-controlled positioning and orientation of omnidirectional and directional (30/spl deg/ beamwidth) antennas to measure both the angles-of-arrival and time-delays of multipath components. We use a unitless definition of angular spread which we proposed previously (see Durgin, G.D. and Rappaport, T.S., IEE Electron. Lett., vol.34, no.25, p.2431-2, 1998). Transmitter-receiver configurations include six outdoor-to-outdoor cross-campus locations at Virginia Polytechnic Institute and State University (17-219 ns rms delay spread, 0.36-0.91 angular spread), three outdoor-to-indoor locations (27-34 ns rms delay spread, 0.78-0.98 angular spread), and three indoor-to-indoor locations (29-45 ns rms delay spread, 0.73-0.90 angular spread). The paper also quantitatively describes a trend that shows how angular spread increases with increasing delay spread. 相似文献
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3.
This paper proposes a random channel generator for the narrowband power line communication (PLC). Based on the top-down approach, an analytical formulation with a limited set of parameters is established for the PLC channel transfer function in the frequency band below 500 kHz. Then, the extracted parameters deduced from measurements are fitted with proper distribution functions. The top-down random channel generator is validated through the comparison between measured and generated channels in terms of time–frequency characterization metrics, especially the average channel attenuation, the root mean square (RMS) delay spread and the coherence bandwidth. Obtained results show the good agreement between the proposed modeled channels and the experimental ones with very close mean values and distributions of the main metrics. 相似文献
4.
为了准确反映复杂城区环境下移动自组织网络(mobile ad hoc network,MANET)通信节点间的无线信道传播特性,以150 MHz频点为例对山东省青岛市典型城区场景的超短波无线信道进行了外场测量.基于测量数据开展统计分析,提取了路径损耗指数、阴影衰落标准差、多径时延拓展以及频率相关性等信道参数,并针对准视距(quasi-light-of-sight,QLOS)区和非视距(non-light-of-sight,NLOS)区建立了大尺度衰落模型和小尺度抽头延迟线模型.分析和建模结果表明:在MANET城市通信场景下,路径损耗指数随距离增加呈现出双斜率特性;当累积分布函数(cumulative distribution function,CDF)为0.9时,均方根时延在QLOS区为726 ns,在阻挡严重的NLOS区为967 ns;相关带宽在QLOS区和NLOS区分别为700 kHz和300 kHz.论文所建信道模型有利于准确衡量MANET通信设备在复杂城区的通信性能,并为相关通信系统设计提供参考. 相似文献
5.
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
6.
Wideband Channel Sounder With Measurements and Model for the 60 GHz Indoor Radio Channel 总被引:1,自引:0,他引:1
《Vehicular Technology, IEEE Transactions on》2005,54(4):1266-1277
In this paper, a wideband channel sounder and measurement results for the short range indoor 60 GHz channel are presented. The channel sounder is based on a 1 gigasamples/s dual channel arbitrary waveform generator and A/D converter/software demodulator, which synthesize and detect a baseband PN sequence with 500 MHz bandwidth. A heterodyne transmitter and receiver translate the baseband PN sequence to and from the 60 GHz band. Ten channel measurements taken across the 59 GHz to 64 GHz range are concatenated to provide a continuous channel measurement covering 5 GHz of bandwidth, resulting in 0.2 ns time domain channel impulse response resolution. The dynamic range and maximum sensitivity performance of the channel sounder are discussed in detail. Comparisons of results with a vector network analyzer based system are shown to verify the accuracy of the sounder. In an extensive measurement campaign with vertically polarized omnidirectional antennas, several different rooms (offices, labs, conference rooms and others) in four different buildings have been investigated. Over 700 channel measurements are the basis for a comprehensive characterization of the short range 60 GHz indoor radio channel with omnidirectional antennas. Finally, a simple stochastic static multipath channel model is derived from the measurement results. 相似文献
7.
Seidel S.Y. Rappaport T.S. Jain S. Lord M.L. Singh R. 《Vehicular Technology, IEEE Transactions on》1991,40(4):721-730
The authors present typical and worst-case root mean square (RMS) delay spreads and excess delay spreads (10 dB) and mean channel path loss at 900 MHz in four European cities using typical cellular and microcellular antenna locations. Several thousand power delay profile measurements were made at six typical cellular and microcellular base station locations in the four cities. The data were obtained at local worst-case time-dispersion locations over hundreds of kilometers of typical operating routes, such as highways, bridges, and city streets, and form the basis for statistical models which can be used to predict the percentage of locations or the percentage of time in which channels will possess particular values of RMS delay spread and excess delay spread. The effect of reference distance on wideband path loss and the propagation path loss laws for cellular and microcellular radio channels are given. Radar cross sections computed from the data for typical scatterers in cellular and microcellular radio channels are given 相似文献
8.
Xiongwen Zhao Kivinen J. Vainikainen P. Skog K. 《Selected Areas in Communications, IEEE Journal on》2002,20(3):507-514
In this paper, empirical channel models and parameters are derived from the wideband measured data at 5.3 GHz in outdoor mobile communications. The path loss exponents and intercepts are obtained by using the least square method. The mean excess delay and mean root-mean-square (rms) delay spread are within 29-102 ns and 22-88 ns, respectively. The correlation distances and bandwidths are within 1-11 λ and 1.2-11.5 MHz, respectively, when the envelope correlation coefficients equal 0.7 in line-of-sight cases. These correlation values depend strongly on the base station antenna heights. The window length for averaging out the fast fading components is about 1-2 m for microcells and picocells. The multipath number distributions follow both Poisson's and Gao's distributions, but Gao's distribution is better in the high probability region. Large excess delays up to 1.2 μs and rms delay spread about 0.42 μs are found in the urban rotation measurements, where the receiver is close to a large open square 相似文献
9.
Pulse propagation characteristics at 2.4 GHz inside buildings 总被引:3,自引:0,他引:3
Seong-Cheol Kim Bertoni H.L. Stern M. 《Vehicular Technology, IEEE Transactions on》1996,45(3):579-592
The growing use of unlicensed wireless systems has spurred interest in the 2.4-GHz ISM band. In order to facilitate the design of such systems, measurements of the pulse response characteristics have been made inside commercial buildings. From the measured pulse response, the statistical properties of the amplitude variation for individual pulses was determined, in addition to the path loss, mean excess delay, root mean square (RMS) delay spread, and the coherence bandwidth of the indoor channel 相似文献
10.
Small scale statistics of multipath propagation in a heavily built-up urban mobile radio environment are presented. The statistics cover vehicle travel distances on the order of 30 m along streets. Measuring equipment time delay resolution is about 0.1 μs. In some locations, paths with significant amplitudes are observed with excess delays of 9 to 10 μs. The delay spreads (sqrt{second central moment of power delay profile} ) in this environment are on the order of 2 μs. Often the signal at fixed delays has a Rayleighdistributed amplitude but large departures from the Rayleigh distribution also occur. From the measurements it appears reasonable to model the urban mobile radio channel as a Gaussian quasi-wide-sense stationary uncorrelated scattering channel within a bandwidth of 10 MHz and for intervals along the street of up to 30 m. 相似文献
11.
《Vehicular Technology, IEEE Transactions on》1973,22(4):104-110
Small scale statistics of multipath propagation in a heavily built-up urban mobile radio environment are presented. The statistics cover vehicle travel distances on the order of 30 m along streets. Measuring equipment time delay resolution is about 0.1 µs. In some locations, paths with significant amplitudes are observed with excess delays of 9 to 10 µs. The delay spreads (√second central moment of power delay profile) in this environment are on the order of 2 µs. Often the signal at fixed delays has a Rayleigh-distributed amplitude but large departures from the Rayleigh distribution also occur. From the measurements it appears reasonable to model the urban mobile radio channel as a Gaussian quasi-wide-sense stationary uncorrelated scattering channel within a bandwidth of 10 MHz and for intervals along the street of up to 30 m. 相似文献
12.
Time delay spread and signal level measurements of 850 MHz radio signals were made over inside-to-outside radio paths at two residential locations and an office building. Root mean square time delay spreads of up to 420 ns were encountered in residential environments. However, when a direct path was present, this improved to less than 325 ns overall, and even to 100 ns at one residence. Received power levels were around -40 dB, with respect to levels received at 0.3 m antenna separation, Under favorable conditions. In other cases, these relative levels varied from - 40 to - 80 dB. Median signal levels agreed well with continuous wave measurements made earlier at one site. No significant polarization dependence or floor level dependence were seen in these data. 相似文献
13.
该文提出一种在模拟域抑制功率放大器(PA)非线性失真的双通道非线性反馈架构,以改善PA线性度,减少邻道泄露。在该架构中,用于抑制非线性的电路包含非线性提取环路和反馈调整环路。非线性提取环路通过耦合器提取PA输入和输出信号,进行幅度和相位对齐后抵消线性信号,保留PA产生的非线性失真。反馈调整环路包含两条独立反馈通道,且信号通过非线性提取环路和反馈调整环路中两条通道分别反馈后的总时延具有两倍关系,使反馈环路呈现2阶Delta-Sigma结构形式,相比于单通道非线性反馈架构具有更好的失真抑制性能。并且通过所提方法配置反馈通道参数,可以实现不同目标频点下非线性失真的灵活抑制。最后设计了一个使用CMPA0060002F商用功放芯片的实验平台,对于带宽为40 MHz,载频为780 MHz的测试信号,在当前6 ns的硬件反馈时延条件下,可以使邻道功率泄露比(ACLR)单边带改善11 dB或双边带改善6 dB,且通过减小反馈时延能够取得更好的性能。 相似文献
14.
This paper addresses some wideband propagation characteristics for Indoor Broadband Wireless LANs at the 60 GHz band. Important system design characteristics from measured results obtained from two wideband 60 GHz LOS radio links are presented. Measurements had been undertaken using the swept frequency channel sounding method. Analysis from the complex frequency responses in a worst-case scenario have yielded to a lower coherence bandwidth value of 5 MHz. Minimum and maximum B0.9coherence bandwidths obtained with a directional horn transmit and an omnidirectional receive antenna is 1.10 MHz and 105.33 MHz respectively. It has been observed that the coherence bandwidth fluctuates significantly with the location of the receiver with respect to the base station. These results can be used for modelling and design of future Indoor BWLANs. 相似文献
15.
《Microwave Theory and Techniques》2009,57(7):1767-1773
16.
The requirement for narrow linewidth lasers or short-loop propagation delay makes the realization of optical phase-lock loops using semiconductor lasers difficult. Although optical injection locking can provide low phase error variance for wide linewidth lasers, the locking range is restricted by stability considerations. Theoretical and experimental results for a system which combines both techniques so as to overcome these limitations, the optical injection phase-lock loop (OIPLL), are reported. Phase error variance values as low as 0.006 rad 2 (500 MHz bandwidth) and locking ranges exceeding 26 GHz were achieved in homodyne OIPLL systems using DFB lasers of summed linewidth 36 MHz, loop propagation delay of 15 ns and injection ratio less than -30 dB. Phase error variance values as low as 0.003 rad2 in a bandwidth of 100 MHz, a mean time to cycle slip of 3×1010 s and SSB noise density of -94 dBc/Hz at 10 kHz offset were obtained for the same lasers in an heterodyne OIPLL configuration with loop propagation delay of 20 ns and injection ratio of -30 dB 相似文献
17.
Wilson P.F. Papazian P.B. Cotton M.G. Lo Y. Bundy S.C. 《Vehicular Technology, IEEE Transactions on》2001,50(1):67-78
Simultaneous four-antenna wide-band mobile channel-sounding measurements were made in two areas at 1920 MHz. The received signal strength and transmission loss were examined. Path-loss exponents for the two sectors were found to be 4.9 and 4.1. Root mean square delay spreads for the two sectors were found to be less than 1.38 and 0.65 μs for 90% of the data and less than 3.14 and 1.35 μs for 99% of the data. Fast fading reduction using antenna diversity and increased channel bandwidth (19.6 kHz, 1.25 MHz, 5.0 MHz, and 10.0 MHz) were examined. Three signal combining methods were considered: selection diversity, equal gain combining, and maximal ratio combining. The measured results show that increasing the number of diversity antennas or the channel bandwidth significantly reduces fading. Maximal ratio combining yields the largest diversity gain, exceeding 11.0 and 17.0 dB at the 90% and 99% fast fade depth probability levels, respectively, for the 19.6-kHz narrow-band signal and 6.7 and 6.9 dB for the 10.0-MHz broad-band signal when all four channels are used 相似文献
18.
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
19.
This paper presents a selection of results obtained during an impulse responsemeasurement campaign undertaken in Hong Kong at 1.8 GHz. The chanel probingsignal bandwidth of 60 MHz was generated by a pseudorandom sequence clockedat 30 MHz. The results of the channel impulse response measurements in theHung Hom district of Kowloon, Hong Kong are presented. The measured resultsare analyzed for CIR parameters like delay spread, average delay and thesignificant number of paths. An attempt is made to relate the measured datawith the geometry of the environmental features that surround the transmitterand the receiver. 相似文献
20.
Wideband multipath measurements at 1300 MHz were made in five factory buildings in Indiana. Root-mean-square delay spread (σ) values were found to range between 30 and 300 ns. Median σ values were 96 ns for line-of-sight paths along aisleways and 105 ns for obstructed paths across aisles. Worst-case σ or 300 ns was measured in a modern open-plan metal-working factory. Delay spreads were not correlated with transmitter-receiver separation or factory topography but were affected by factory inventory, building construction materials, and wall locations. Wideband path loss measurements consistently agreed with continuous-wave measurements made at identical locations. It is shown that such empirical data suggest independent and identical uniform distributions on the phases of resolvable multipath signal components. Average factory path loss was found to be a function of distance to the 2.2 power 相似文献