Mobile radio propagation in Auckland at 76 MHz

A series of field trials in Auckland at 76 MHz have confirmed that propagation path loss is normally distributed and may be characterised by a fourth-power-law distance dependency. The path loss standard deviation has been found to be dependent on the mobile terminal's environment and on frequency, but is essentially independent of base station antenna height and path length. The excess path loss over plane earth predictions and the standard deviation of path loss have been measured as 14.6, 5.0, 0.8 and 1.0 dB and 6.2, 5.2, 3.7 and 5.0 dB for urban, light urban, suburban and rural environments, respectively.     

Hata based propagation loss formula using terrain criterion for 1800 MHz

Many mobile propagation models are going under intensive corrections; recently, to suit other new criteria's such as rough terrain areas. This proposed model modifies Hata main urban equation by adding a formula representing a logarithmic linear regression estimator of the standard deviation (σ) of the measuring campaign path in Amman city, Madaba city, and Jiza town, Jordan. High correlation factor of −96.7% is calculated between excess measured path loss compared to Hata urban path loss and log(σ). Root mean square error (RMSE) difference between this model and the measured raw data path loss has overcome RMSE calculated for Hata model, by an average of 21 dB, for open areas. The correction of suburban areas is calculated, on average, as 20 dB, and for urban areas as 17 dB.     

Mobile radio propagation in Auckland at 465 MHz

A series of field trials in Auckland at 465 MHz have confirmed that propagation path loss may be characterised by a fourth-power-law distance dependency. The excess loss over plane earth predictions has been measured as 37.8, 26.4, 18.6 and 14.1 dB for urban, light urban, suburban and rural environments, respectively.     

Terabit-per-Second Satellite Links: a Path Toward Ubiquitous Terahertz Communication

Due to the demand for high-speed wireless communications, carrier frequencies have increased in the search for both available and wider bands. The millimeter-wave and terahertz bands (0.1–3 THz) are commonly believed to be impractical for all but short-range links due to severe attenuation by atmospheric water vapor. However, the field of submillimeter radio astronomy has demonstrated that this can be effectively mitigated by the construction of large aperture telescopes in very dry high-altitude locations, such as the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes. Modeling has shown that Earth-satellite links in excess of 1 Tb per second can be achieved with a system patterned off observatories, since the loss of a satellite link from a dry location equals a sea-level path of only several kilometers. Despite advantages over optical satellite links, THz links have not been an area of active study. We review the technology and science necessary to develop a terabit-per-second THz satellite link and argue that a satellite link offers a good first step toward the development of ubiquitous THz communications.     

Satellite Sound Broadcasting Around 1 GHz

This paper presents the technical factors affecting the design of a geostationary satellite sound broadcasting system operating around 1 GHz to serve low-cost consumer-quality portable and automobile receivers. The technical characteristics for such a system are under study in a number of countries in preparation for the 1985/1988 ITU Space Services Planning Conference.The first session will make appropriate recommendations to the second session on the future regulatory provisions for the service. A medium-quality monophonic or stereophonic service would be provided using frequency modulation. Signals would be received using a simple circularly polarized omnidirectional antenna. Link margins to serve indoor portable receivers and automobile receivers in rural and urban areas are discussed. Building penetration loss for single family dwellings is expected to be about 11.8 dB in 90 percent of the houses not using foil-backed insulation or shadowed by trees, increasing to over 17 dB with foil-backed insulation. Shadowing by trees increases the loss by 12-15 dB. Apartment and commercial building penetration loss is expected to approach 20 dB. Automobile reception in rural areas will be primarily affected by foliage attenuation due to trees. At a 30° elevation angle, an attenuation of about 15 dB with probability of 0.90 is expected. In situations where the line-of-sight path is unobstructed, multipath fading of 2.8 dB at 0.90 probability is the predominant source of degradation. Automobile reception in urban areas requires operating margins of 24-30 dB because of shadowing and multipath by large buildings. Based on the foregoing considerations, an e.i.r.p. from 66 to 79 dBW is required from a geostationary satellite to serve low-cost portable and automobile receivers in rural and urban environments.     

Variability of mobile radio path loss in Auckland at 465 MHz

A series of field trials in Auckland at 465 MHz have confirmed that the variability of mobile radio path loss is approximately normally distributed and can, therefore, be represented by a standard deviation. This standard deviation has been found to be dependent on the mobile terminal's environment and on frequency, but is essentially independent of base-station antenna height and path length. Standard deviations have been measured as 5.2, 4.4, 5.4 and 5.2 dB for rural, suburban, light urban and urban environments, respectively.     

Urban mobile radio propagation at 900 MHz

A series of field trials in London and Birmingham have been used to provide a propagation data base in urban areas at 900 MHz. Measured signal strengths are highly correlated with the results of earlier trials at lower frequencies. The excess loss over plane earth predictions varies with location but is generally in excess of 40 dB.     

Path diversity for LEO satellite-PCS in the urban environment

A new method for analyzing the propagation aspects of mobile satellite systems is introduced. It consists of: (1) taking fisheye lens images at potential user locations; (2) extracting path state information (clear, shadowed, or blocked) as a function of look angles from the images; and (3) combining each path state for single or multiple satellites in a specific constellation with frequency-appropriate statistical fade models to predict overall performance measures such as fade dependence with elevation angle or path-diversity gain. The advantage of the method is that it minimizes the need for expensive propagation campaigns. The importance of including specular reflections and diffraction under urban blockage conditions is established. From images obtained in urban Japan, a fade-lapse rate with elevation of 0.2 dB/degree is deduced for fades exceeded about 10% of the time. Path-diversity gain for combining and hand-off diversity is found for up to four-fold diversity at a high-, mid-, and low-latitude location for the Globalstar constellation. With two-fold diversity and neglecting implementation losses, the fade margin required for 80% and 95% coverage at mid-latitude urban locations is reduced from 16 to 6 dB and from 25 to 16 dB, respectively     

Integrated folding 4/spl times/4 optical matrix switch with total internal reflection mirrors on SOI by anisotropic chemical etching

A folding rearrangeable nonblocking 4/spl times/4 optical matrix switch was designed and fabricated on silicon-on-insulator wafer. To compress chip size, switch elements (SEs) were interconnected by total internal reflection (TIR) mirrors instead of conventional S-bends. For obtaining smooth interfaces, potassium hydroxide anisotropic chemical etching of silicon was utilized to make the matrix switch for the first time. The device has a compact size of 20/spl times/1.6 mm/sup 2/ and a fast response of 7.5 /spl mu/s. The power consumption of each 2/spl times/2 SE and the average excess loss per mirror were 145 mW and -1.1 dB, respectively. Low path dependence of /spl plusmn/0.7 dB in total excess loss was obtained because of the symmetry of propagation paths in this novel matrix switch.     

Effect of Atmospheric Parameters on Satellite Link

The rainfall path attenuation measured at Universiti Sains Malaysia (USM) for 4 years (January 02 to January 06) is presented. The data obtained are useful to investigate the impairment due to rainfall attenuation in satellite links operating in tropical and equatorial climates. It shows that the logarithmic function with ground rain rate deviates at very high rain rate. A rainfall rate of 130 mm/h causes the rainfall attenuation threshold (> 20 dB) to be exceeded. Maximum exceedences for rain rate and attenuation were observed during the wet months. The cumulative distributions of attenuation derived from the measured data are presented and compared with those obtained with existing prediction methods.     

Path loss prediction in microcellular environments at 900 MHz

A model is proposed to estimate path loss in urban environments at 900 MHz when the base station antenna is below the average height of the buildings. It shows that the percentage of area occupied by buildings explains more than 20 dB of variation of the mean path loss.     

Performance of a circular signal set in a regenerative satellite system employing TWTA or SSPA

This paper presents the results of a computer-simulation study of a (4,12) circular signal set for use over regenerative satellite links. The signal has a 16-ary symbol alphabet. The satellite transponders and each of the earth-stations use either travelling-wave-tube amplifiers (TWTAs) or solid-state power amplifiers (SSPAs) for high-power amplification. Several different earth-stations are assumed to have simultaneous access to a given regenerative satellite, in an arrangement of frequency division mulitple access (FDMA). Thus, adjacent-channel-interference (ACI) can be introduced into the wanted signal by the immediately adjacent channels. The performances of the signal are compared to those of a 16-ary differentially encoded-quadrature-amplitude-modulated (16-ary DEQAM) signal with a rectangular signal set and the results are used to determine the preferred signal set for spectrally efficient transmission over satellite links. It has been shown that, with TWTAs used for high-power amplification and in the absence of ACI, the circular signal set has an advantage of about 3 dB over the rectangular signal set, at the bit error rate of 10^?4. While in the presence of the ACI, the advantage is 2 dB. With SSPAs, the respective advantages become 0·7 and 0·5 dB.     

紫外光NLOS通信的机群间通路快速恢复算法

为了研究直升机编队飞行在链路中断或节点中断情况下的路径恢复,基于紫外光非直视通信的路径损耗,采用Dijkstra算法寻找网络连通性的前提下直升机编队飞行通信网络的最优路径,通过节点移动来实现链路中断或节点中断时的路径恢复。通过理论以及仿真分析,得到了最优路径在不同链路断开时的路径恢复情况。结果表明,采用所提出的算法虽然在节点移动时需要花费2s~3s的时间,但是与路径重寻方法相比,3跳和4跳节点的链路收敛时间能够有效减小0.2ms和0.4ms,路径权值同样能够减小20dB和45dB,因此该算法具有可行性。这一结果对机群间路径快速恢复的研究有一定的应用价值。     

Fuzzy-Based Uplink Power Control in Forward Broadband Satellite Links

End-to-end performance of broadband satellite links operating at Ku band and above is studied in this paper. The problem of power control in terms of optimal power allocation and maximization of the total carrier-to-interference-and-noise ratio is considered. More specifically, the paper proposes the use of Fuzzy Inference Systems (FIS) to optimize power allocation in a dual-hop (end-to-end) satellite system, considering the general case of dual-polarized satellite links with transparent satellite transponder. The quality of the link is assessed through the FIS based on the predicted values of rain attenuation induced on the corresponding links and the interference-to-noise ratios. According to this estimation, the satellite hub-station increases or reduces the allocated uplink power. The proposed scheme’s effectiveness is investigated in terms of carrier-to-noise plus depolarization plus interference ratio and power consumption for 30/20 GHz frequency in the uplink and the downlink respectively. A variety of conditions is considered regarding the rain attenuation values from 0 (no rain) to 30 dB and interference-to-noise ratio from ?15 to 15 dB to both links. Finally, the scheme is compared to step-based power control algorithms, showing that it can significantly reduce the total consumed power.     

基于机器学习和卫星图像的路径损耗预测

基于反向传播神经网络（back propagation neural network,BPNN）构建了一种路径损耗预测模型.通过卫星图像的红、绿、蓝（red, green and blue,RGB）通道的颜色信息来表征无线通信电波传播路径的环境特征,结合路测点与基站的距离特征构建数据集,迭代训练网络参数,以预测传播路径损耗.结果表明,对跨基站路测点的预测结果与实测数据之间的相关系数达到0.83,绝对平均误差控制在0.66 dB,标准差控制在6.65 dB,说明在缺乏某一场景的详细模型和材质参数时,本文模型也能可靠预测无线通信电波的传播路径损耗.此外,本文信道模型与传统信道建模方法多方面的对比与分析表明,本文模型在相同计算资源下可以提供和传统信道建模方法相差很小的预测结果,同时大大缩短预测所需的时间,说明本文模型对传播路径损耗做出快速预测的能力可以用于无线通信网络系统的优化.     

Multiple knife-edge diffraction of microwaves

The paper discusses a simplified solution to the problem of multiple diffraction of microwaves over knife-edge obstacles. The path loss is obtained directly and quickly by alignment of distances and heights, adequately selected from a path profile. A theoretical study shows good agreement between the simplified approach and a complete mathematical analysis made by G. Millington in 1962. When the diffraction loss reaches a maximum which might be in excess of 50 dB, the approximate value exceeds the theoretical one by 2 to 5 dB. Predictions are in good agreement, too, with the results of experiments conducted both in France and in the United States. Out of ten examples reported in the paper, nine indicate an error equal or smaller than 3 dB.     

914 MHz path loss prediction models for indoor wirelesscommunications in multifloored buildings

Qualitative models are presented that predict the effects of walls, office partitions, floors, and building layout on the path loss at 914 MHz. The site-specific models have been developed based on the number of floors, partitions, and concrete walls between the transmitter and receiver, and provide simple prediction rules which relate signal strength to the log of distance. The standard deviation between measured and predicted path loss is 5.8 dB for the entire data set, and can be as small as 4 dB for specific areas within a building. Average floor attenuation factors, which describe the additional path loss (in decibels) caused by floors between transmitter and receiver, are found for as many as four floors in a typical office building. Path loss contour plots for measured data are presented. In addition, contour plots for the path loss prediction error indicate that the prediction models presented are accurate to within 6 dB for a majority of locations in a building     

Millimeter-wave propagation at street level in an urban environment

Measurements on point-to-point transmission at street level were performed in downtown Denver, CO, with RF probes that operated at 9.6, 28.8, and 57.6 GHz. All probes were mounted on self-contained vehicles, permitting a variety of path scenarios. Information on performance of these channels for propagation in an urban environment on both line-of-sight and non-line-of-sight paths is presented. For non-line-of-sight (non-LOS) paths obstructed by buildings of several common materials, results that showed signal attenuations in excess of 100 dB. When the LOS followed a path directly through clear glass walls, the attenuation was small at all probe frequencies. However, when the glass wall had a metalized coating to reduce ultraviolet and infrared radiation, the attenuation increased by 25 to 50 dB for each metallized layer. In most cases no signals could be detected through steel reinforced concrete or brick buildings     

4×4热光SOI波导开关阵列

设计并制作了阻塞型和完全无阻塞型4×4热光SOI(silicon-on-insulator)波导开关阵列。开关单元采用了多模干涉耦合器(MMI)-MZI(Mach-Zehnder interferometer)结构的2×2光开关。阻塞型光开关附加损耗为4.8～5.4dB,串扰为-21.8dB～-14.5dB。完全无阻塞型光开关阵列附加损耗为6.6～9.6dB,串扰为-25.8～-16.8dB。两者的消光比都在17～25dB内变化,开关单元功耗小于230mW。器件的开关时间小于3μs。功耗和开关速度都明显优于SiO2基和聚合物基的开关阵列。     

Indoor broadband optical wireless communications: optical subsystems designs and their impact on channel characteristics

With proper system design, infrared multispot diffusing (MSD) configuration communications links promise several orders of magnitude higher bit rates than radio links. Essential to the communications system are the optical subsystems: transmitter and receiver optics. Preliminary experiments on fabrication of beamshaping optical elements for the transmitter and receiver optical front-end have been conducted. The impact of optical subsystems on channel characteristics is investigated, and the results undoubtedly prove the great potential of MSDC. Use of holographic optical elements at both transmitter and receiver increases the signal-to-noise ratio by at least 11 dB and at the same time significantly improves the power budget of the system by reducing path loss by more than 6 dB.