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Vehicular Technology, IEEE Transactions on

Issue 4 • Date Nov. 1977

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Displaying Results 1 - 17 of 17
  • [Front cover and table of contents]

    Page(s): c1
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    Freely Available from IEEE
  • In memoriam [Richard Pitman Gifford]

    Page(s): 293 - 294
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    Freely Available from IEEE
  • Radio propagation for vehicular communications

    Page(s): 295 - 308
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    Radio propagation is affected by many factors including the frequency, distance, antenna heights, curvature of the earth, atmospheric conditions, and the presence of hills and buildings. The influence of each of these factors at frequencies above about 30 MHz is discussed with most of the quantitative data being presented in the series of nomograms. By means of three or four of these charts an estimate of the received power and the received field intensity for a given point-to-point radio transmission path ordinarily can be obtained in a minute or less. The theory of propagation over a smooth spherical earth is presented in a simplified form that is made possible by restricting the frequency range to above about 30 MHz where variations in the electrical constants of the earth have only a secondary effect. The empirical methods used in estimating the effects of hills and buildings and of atmospheric refraction are compared with experimental data on shadow losses and on fading ranges. View full abstract»

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  • Radio wave loss deviation and shadow loss at 900 MHz

    Page(s): 309 - 313
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    Radio wave propagation between base and mobile stations is normally described as being Rayleigh distributed due to multipath radio wave combining. When the number of radio wave paths are limited the variation in received signal amplitude frequently follows a more general case given by a Weibull distribution. A significant portion of the Weibull distribution is defined as the transmission loss deviation. Other definitions have been included with the object of standardizing methods of measuring and reporting propagation data. Data will be presented showing loss deviation between 3 and 30 dB. Shadow loss over hills and around buildings are usually assumed to be knife-edge or rounded knife-edge. Shadow loss based on these assumptions is generally found to be less than the true measured value. Data will be presented comparing calculated shadow loss with measured value. View full abstract»

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  • Mobile radio propagation in British cities at frequencies in the VHF and UHF bands

    Page(s): 313 - 323
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    Measurements of the received signal envelope magnitude have been made in three British cities at frequencies of 85.875, 167.2, and 441.025 MHz. In all cases unmodulated carrier waves were radiated from aerials atop tall buildings or prominent terrain features and detected using a vehicle-mounted receiver. These measurements have provided the basis for an analysis of the factors affecting the transmission loss in urban/suburban areas which, in turn, has enabled a propagation prediction model to be constructed. Close agreement between measured and predicted path losses has been found for the various terrain situations investigated. The statistical prediction errors produced by the proposed model for the three British cities analyzed are shown to be similar in magnitude to those obtained using an extrapolation of the Okumura method. Because the proposed model is much less complex and procedurally simpler, it is recommended for use, in the first instance, in British cities. View full abstract»

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  • Computer prediction of service areas for VHF and UHF land mobile radio services

    Page(s): 323 - 327
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    A computer program written to predict the effective service area of a transmitter in a VHF or UHF mobile radio network is described. The computed results enable field strength contours to be determined, and hence provide more useful information than is possible by reference to standard statistical curves. Present manual methods of calculating the attenuation to be expected over transmission paths rely on the laborious extraction of essential ground profile information along the path joining the transmitter to the receiver. This difficulty may be overcome by using a topographical data base in a computerized method of service area prediction. With this scheme each data base entry represents the effective terrain height above sea level within each 0.5-km square. A high-speed computer can access the necessary information from the data base to reconstruct a close approximation of the radio path profile. The reconstructed profile is then processed to calculate the transmission loss. These computations are repeated for numerous points throughout the area and enable field strength contours to be deduced. The propagation model described forms part of a fully automated frequency assignment procedure for the private land mobile radio services in operation in the Directorate of Radio Technology, Home Office, UK. View full abstract»

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  • 900-MHz mobile radio propagation in the Copenhagen area

    Page(s): 328 - 331
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    A comparative study of 900-MHz, 450-MHz, and 150-MHz mobile radio propagation characteristics performed in Copenhagen, Denmark is described. The three systems were compared with respect to usable coverage area, flutter characteristics, and transmission quality. A statistical method was used for the determination of the coverage area, the limits of which are defined by the contour line corresponding to 20-dB noise quieting at 90 percent of the locations. Flutter patterns were photographically recorded, and simultaneous recordings of voice signals received on the three systems were made on magnetic tape. Concluded is that when corrections are made for differences in transmitter power, antenna gain, receiver sensitivity, etc., and when the propagation losses are assumed to vary with frequency like the free space losses, the coverage areas obtained will be nearly identical. The increased flutter rate at 900 MHz apparently does not affect the transmission noticeably, and it must be generally concluded that the 900-MHz band will provide as good mobile radio performance as any of the lower bands. View full abstract»

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  • Mobile fading—Rayleigh and lognormal superimposed

    Page(s): 332 - 335
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    A closed solution is presented showing the composite probability distribution of power levels derived from short term Rayleigh fading with superimposed long term lognormal variations of mean value. An example shows how the results can be applied to the prediction of bit error rates in a mobile radio data transmission channel, and how the error rate will vary with standard deviation of the lognormal distribution. View full abstract»

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  • Mobile radio fading in Scandinavian terrain

    Page(s): 335 - 340
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    Field strength patterns have been recorded in Sweden (deep woods, hilly terrain), Norway (long narrow valleys), and Denmark (farmland, urban districts). Digital processing of recordings has taken place. Examples of amplitude distributions are presented for various types of terrain. Results show good agreement with the Rayleigh distribution in spite of the great difference in type of terrain. View full abstract»

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  • Multipath delay spread and path loss correlation for 910-MHz urban mobile radio propagation

    Page(s): 340 - 344
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    Performance of some mobile radio systems is limited both by multipath delay spread and average path loss. This paper presents data indicating a low correlation between delay spread and path loss at 910 MHz for 100 small areas within a 2 × 2 ½-km region. Some small areas with low path loss have large delay spread. The region extends from 1.5 to 3.5 km from a base station on a 120-m high building in New York City. The region is representative of heavily built-up downtown districts of many large U.S. cities. View full abstract»

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  • Mobile antenna gain in the multipath environment at 900 MHz

    Page(s): 345 - 348
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    A program has been completed that investigated the effect of the urban multipath environment on mobile antennas at 900 MHz. The program involved the construction of several mobile antennas, careful measurement of these antennas on an antenna range to determine their characteristics in a controlled environment, and measurement of their characteristics in the multipath environment of cities. Measured results were compared to computed results and pattern range results were compared to field data to permit generalized conclusions to be reached. The results of the second phase of the program, measurements made in the mobile multipath environment, are presented. Analysis of this data shows that gain antennas have significantly less gain in areas where multipath propagation predominates and that the increased aperture of the gain antennas provides no significant smoothing of the received signals in the multipath environment. View full abstract»

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  • Antennas for VHF/UHF personal radio: A theoretical and experimental study of characteristics and performance

    Page(s): 349 - 357
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    A theoretical analysis of the characteristics of small personal radio antennas for the 68- to 470-MHz frequency range is given. Representing the human body by a simplified lossy dielectric structure, the influence of the body on the performance of the antenna is investigated in detail, and it is shown how antenna impedance, gain, and radiation patterns can be calculated taking the presence of the body into account. For very short antennas the results indicate that radiation from the body may dominate over the radiation contributed by the antenna itself, and that the presence of the body can increase the antenna efficiency considerably, indicating that even very short antennas may provide acceptable radiation efficiencies. The results of the theoretical work are supported by measurements on practical antennas. Quarter-wave and short antennas of the helical type are compared with respect to efficiency and radiation patterns at 80, 160, and 450 MHz, and it is demonstrated how the physical length of the antenna affects the antenna performance. The design of a very short and compact personal radio antenna is described. View full abstract»

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  • The attenuation of UHF radio signals by houses

    Page(s): 358 - 362
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    The results of a measurement program that was conducted to determine the attenuation of UHF radio signals penetrating to the inside of a typical house is presented. This program is part of a study to determine the feasibility of using direct satellite communication to disseminate disaster warning messages. The measurements were made in a manner to determine the building attenuation as a function of frequency, construction type, climate, and the elevation angle to the signal source. Attenuation measurements were made in five cities: Boulder, CO, Duluth, MN, Kansas City, MO Little Rock, AR, and Houston, TX. The measurements were made at three frequencies, 860 MHz, 1550 MHz, and 2569 MHz, using the ATS-6 geosynchronous satellite as a signal source. Most measurements were made on two principal house types; wood frame with a wood outside surface, and wood-frame with a brick-veneer outside surface. The average measured building attenuation for all houses and all frequencies was 6.3 dB. View full abstract»

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  • New radio paging system and its propagation characteristics

    Page(s): 362 - 366
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    A radio paging system using a 200 band NRZ-digital code for the selective calling signal on new frequency bands is discussed. This system uses the 250-MHz band, and its propagation characteristics in urban areas, necessary for the radio system design, was measured in the Tokyo area. Distance versus median field strength characteristics in this band approximate that of the 150-MHz band. Building loss is 19.7 dB and is less than that of the 150-MHz band. Therefore, the new system will provide nearly the same grade of service as the former system using the 150-MHz band. View full abstract»

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  • Cordless telephone system and its propagation characteristics

    Page(s): 367 - 371
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    The cordless telephone system is designed to replace the indoor portion of a subscriber line with a radio so that a telephone set can be carried about freely and used anywhere within a limited service area. Therefore, it can be considered to be a partial realization of a portable telephone system. A description of the cordless telephone system using the 250-MHz and 400-MHz bands, which is scheduled to be put into commercial service is presented. The propagation characteristics, such as indoor propagation and urban area propagation for short distances, which are important for the system are also presented. Finally, the ultrasmall zone (minicellular zone) composition, which is newly employed in the system, is described. View full abstract»

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  • Leaky coaxial cable characteristics at 900 MHz

    Page(s): 372 - 375
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    Mobile communication through electromagnetically obstructed areas can be established by using wayside leaky coaxial cables. Available experimental data had been limited to 450 MHz. This paper presents the results of a recent experiment of the RADIAX cable at 900 MHz in near-field. These data are used to supplement an earlier RADIAX experiment at frequencies below 450 MHz and to compare with a theoretical study at 1 GHz. View full abstract»

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  • [Back cover]

    Page(s): c4
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    Freely Available from IEEE

Aims & Scope

IEEE Transactions on Vehicular Technology covers land, airborne, and maritime mobile services, vehicular electrotechnology, equipment, and systems identified with the automotive industry.

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Meet Our Editors

Editor-in-Chief
Yuguang Michael Fang
University of Florida