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Showing papers in "IEEE Transactions on Vehicular Technology in 1981"


Journal ArticleDOI
Tor Aulin1
TL;DR: A new model for the digital channel is proposed, which is a memoryless binary symmetric channel (BSC) with field strength dependent crossover error probability and fits very well to the recorded data.
Abstract: A field test has been made in order to better understand the digital mobile radio channel. At the mobile receiver (450 MHz, 1200 bits/s) recordings were made of the digital signal and the field strength. These recordings were later analyzed by a computer. Some existing models for digital channels have been tested. Theoretically motivated probability density functions for the fading envelope have also been considered. A new model for the digital channel is proposed. This model is a memoryless binary symmetric channel (BSC) with field strength dependent crossover error probability. This model fits very well to the recorded data.

132 citations


Journal ArticleDOI
TL;DR: The performance of code division multiple-access (CDMA) systems is determined using direct-sequence spectral spreading to show the degradation in system performance as a function of the number of users to have a threshold effect.
Abstract: The performance of code division multiple-access (CDMA) systems is determined using direct-sequence spectral spreading. Asynchronous users are assumed so that there is no network control. Under relatively ideal conditions, the degradation in system performance as a function of the number of users is shown to have a threshold effect. This basic limitation in the number of users of the system is further limited if the powers are unequal. For two users, system performance as a function of their power ratios also has a threshold effect. System performance as a function of the amount of spectral spreading is determined. The performance of both coded and uncoded systems is predicted.

128 citations


Journal ArticleDOI
TL;DR: In this article, the authors studied burst error characteristics by using a Rayleigh and Nakagami-Rice fading simulator, and proposed burst length shortening by means of dual frequency diversity is a promising candidate in order to introduce safely forward error correction (FEC) coding into digital land mobile communication systems.
Abstract: Burst error characteristics are studied by using a Rayleigh and Nakagami-Rice fading simulator. Burst error length distribution estimated with fade duration is described. Thus burst length shortening by means of dual frequency diversity is a promising candidate in order to introduce safely forward error correction (FEC) coding into digital land mobile communication systems.

50 citations


Journal ArticleDOI
TL;DR: The error rate performance of duobinary coded MSK and TFM has been studied under these environments with noncoherent detection and the probability of error has been calculated by numerical integrations for different cases of slow and fast fading and cochannel interference.
Abstract: Two continuous phase constant envelope modulation schemes are considered for use in digital mobile radio communication systems. These two schemes, duobinary coded minimum shift keying (MSK) and tamed frequency modulation (TFM), use partial response signaling to achieve efficient power spectrum. Therefore, they are suitable candidates for the application of digital data transmission via mobile radio where spectrum efficiency is an important consideration. The mobile communication channel is characterized by fast Rayleigh fading and cochannel interference resulting from the reuse of the channels. The error rate performance of duobinary coded MSK and TFM has been studied under these environments with noncoherent detection. A closed form expression for the probability of error of duobinary coded MSK with discriminator detection has been derived and evaluated for different cases of fast and slow fading and cochannel interference. The probability of error of duobinary coded MSK and TFM with differential detection has been calculated by numerical integrations for different cases of slow and fast fading and cochannel interference.

47 citations


Journal ArticleDOI
TL;DR: The form of space diversity suggested has the unusual feature that it can be employed at the fixed station site only and provide diversity in both communication paths, i.e., to and from the mobile.
Abstract: The performance of a spread-spectrum receiver previously described by the authors is analyzed in detail. Performance curves are given for a wide range of mobile radio channel conditions, including multipath distortion and correlated fading. The use of optimal filters to combat the former and space diversity to combat the latter are investigated. Some errors in the authors' earlier papers are corrected. The form of space diversity suggested has the unusual feature that it can be employed at the fixed station site only and provide diversity in both communication paths, i.e., to and from the mobile. Degradation due to fading and other aberrations is shown to be in the range 3-6 dB for typical mobile channel conditions. In a nonfading channel the receiver is suboptimum by about 3 dB.

30 citations


Journal ArticleDOI
TL;DR: Application of the method to the cases of minimum shift keyed and offset quadriphase shift key (OQPSK) systems reveals a slight performance advantage for MSK.
Abstract: A technique is given for determining the error-rate performance of a class of digital communication systems operating with fading multipath interference. The approach uses a truncated series to represent the fading process and takes into account the effects of intersymbol interference caused by linear filtering in the receiver or channel. Application of the method to the cases of minimum shift keyed (MSK) and offset quadriphase shift key (OQPSK) systems reveals a slight performance advantage for MSK.

28 citations


Journal ArticleDOI
TL;DR: The describing-function approach, especially in view of its ease of application and the insights it provides, appears to be a useful one for the control aspect of antiskid design.
Abstract: A describing-function approach is employed in the design of an antiskid braking system. This includes the specification of the dynamics of a braking vehicle, a proposed system employing a feedback compensator to provide antiskid behavior, and the determination of the design parameters by a describing-function analysis. A wide range of tire-roadway conditions was considered in the latter. The resulting design was implemented and evaluated in field tests. The observed antiskid braking performance was approximately that predicted from the design. Thus the describing-function approach, especially in view of its ease of application and the insights it provides, appears to be a useful one for the control aspect of antiskid design.

24 citations


Journal ArticleDOI
TL;DR: In this paper, a theoretical and experimental evaluation of the electromagnetic fields in the immediate vicinity of resonant dipole antennas is presented. And it is shown in the results that it is possible to detect relatively high intensity electromagnetic (EM) fields in close proximity to dipoles even for very low levels of radiated power (1 mW and less).
Abstract: The theoretical and experimental evaluation of the electromagnetic fields in the immediate vicinity of resonant dipole antennas is presented. This type of antenna is widely used with portable and mobile radio transmitters. The work presented herein has been motivated by the concern that future Radio Frequency Protection Guides with respect to human exposure to nonionizing electromagnetic radiation might be expressed strictly in terms of the intensity squared of the electric or magnetic fields. It is shown in the results that it is possible to detect relatively high intensity electromagnetic (EM) fields in close proximity to resonant dipoles even for very low levels of radiated power (1 mW and less). The paper is divided into a theoretical section and an experimental section because its goals are twofold. First, the formulas for the correct evaluation of the EM fields in the close proximity to dipole antennas are established. Second, it is shown that such EM fields, which can be theoretically predicted and experimentally verified with satisfactory accuracy, are indeed strong enough to violate proposed Radio Frequency Protection Guides even for very low levels of radiated power. Thus portable radios are rendered virtually useless, although the same guides permit exposures to much higher levels of power in the far field. Part I of the paper is essentially theoretical and expresses the fields near dipole antennas in terms of cylindrical waves, which lend themselves to closed form integration. The asymptotic expressions of some components of the field are particularly simple for close distances (in terms of wavelength) from the antenna. The correctness of the solution is checked by evaluating how closely boundary conditions are satisfied. Results have shown that previously used formulas for evaluating field intensity very near dipole antennas can give incorrect values.

18 citations


Journal ArticleDOI
S. Asakawa1, F. Sugiyama
TL;DR: In this paper, a digital modulation system with compact spectrum and constant envelope is proposed, based on the results of theoretical and experimental studies, which is suitable for digital mobile communication, which generally is subject to deep and rapid fading.
Abstract: A digital modulation system with compact spectrum and constant envelope is proposed, based on the results of theoretical and experimental studies. This modulation system is suitable for digital mobile communication, which generally is subject to deep and rapid fading. It is characterized with a possibility of practical and stable instrumentation. In the modulator, modulation signal parameters are read out of the memories, by which precise spectrum and waveform can be realized. For the modulator, an orthogonal phase modulation, whose parameters are stable, can be adopted by pertinent parameter design for the modulating signal stored in the memories. The experimental results agree well with the design.

16 citations


Journal ArticleDOI
TL;DR: It is postulated that satellites could serve this lower density, thin-route market at a competitive cost and thus complement terrestrial systems in the urban and more densely populated areas to provide an integrated nationwide mobile service.
Abstract: Potential satellite markets in the public safety (disaster relief, emergency medical, and law enforcement) and common carrier (mobile radio telephone) service areas are identified. The public mobile telephone segment is then examined to illustrate a methodology for identifying a potential satellite addressable market, including capacity requirements for roughly sizing a satellite. It is postulated that satellites could serve this lower density (mobiles per square kilometer), thin-route market at a competitive cost and thus complement terrestrial systems in the urban and more densely populated areas to provide an integrated nationwide mobile service.

12 citations


Journal ArticleDOI
TL;DR: A random model for urban ultrahigh frequency (UHF)- multipath propagation is proposed using an optical analogy, which can be well justified at these high frequencies.
Abstract: A random model for urban ultrahigh frequency (UHF)- multipath propagation is proposed. The model uses an optical analogy, which can be well justified at these high frequencies. Several results are obtained. The transfer function and its autocorrelation properties are investigated. Also the time domain behavior is studied. The model is finally tested against experimental data from a field trial made in the town of Linkoping, Sweden.

Journal ArticleDOI
TL;DR: In this article, the results of an experimental program to evaluate the electric field near dipole antennas are presented, and the measured field intensities are compared with the numerical values computed using the theory developed in Part I of this paper.
Abstract: The results of an experimental program to evaluate the electric field near dipole antennas are presented. The measured field intensities are compared with the numerical values computed using the theory developed in Part I of this paper. The theoretical and measured field intensities are in excellent correlation even for observation points spaced from the axis of the dipole less than one hundredth of a wavelength. For thin dipoles (radius ≃ .002λ) the experimental measure of the E-field at the antenna surface or at one antenna radius distance has not been possible because of the practical limitation of available instruments. The experimental and theoretical results show that the field intensities near some parts of a dipole antenna are higher than predicted by commonly used formulas.

Journal ArticleDOI
TL;DR: Theoretical predictions are shown to have good agreement with the experiment and the relation between the radiation patterns and the correlation coefficient is worked out.
Abstract: A novel diversity technique is suggested for mobile communications. It depends upon the radiation patterns of the used antennas. The relation between the radiation patterns and the correlation coefficient is worked out. Theoretical predictions are shown to have good agreement with the experiment.

Journal ArticleDOI
TL;DR: An analysis of the effect of multiple narrow-band interfering signals on the probability of error in a frequency-hopped differential phase shift keyed (FH-DPSK) spread-spectrum communication system indicates that for n ≥ 32 adequate performance can be achieved even when each of the subchannels has an interfering signal present.
Abstract: An analysis of the effect of multiple narrow-band interfering signals on the probability of error in a frequency-hopped differential phase shift keyed (FH-DPSK) spread-spectrum communication system is given. A basic assumption in this analysis is that the sum of the outputs from an n-subchannel receiver can be modeled as a Gaussian random variable. Subject to this assumption, numerical evaluation of the probabilities of error for both nonfading and Rayleigh fading channels are presented. The results indicate that for n ≥ 32 adequate performance can be achieved even when each of the subchannels has an interfering signal present.

Journal ArticleDOI
TL;DR: In this article, NASA's application technology satellites (ATS) were used in a series of communications and position-fixing experiments with automotive vehicles, ships, and aircraft, and the technical success of the experiments and demonstrated potential value of the communications prompted a study that concluded an operational satellite-aided system would be a valuable augmentation of planned trunking or cellular-type terrestrial mobile radio telephone systems.
Abstract: NASA's application technology satellites (ATS) were used in a series of communications and position-fixing experiments with automotive vehicles, ships, and aircraft. Applications of the communications were demonstrated and evaluated for public services including law enforcement, search and rescue, medical emergency, and for commercial uses in the land and maritime transportation industries. The technical success of the experiments and the demonstrated potential value of the communications prompted a study that concluded an operational satellite-aided system would be a valuable augmentation of planned trunking or cellular-type terrestrial mobile radio telephone systems.

Journal ArticleDOI
On-Ching Yue1
TL;DR: In this paper, the authors compared two frequency-hopping mobile radio systems for digitized speech and showed that the system employing multiple frequency-shift keying (MFSK) can accommodate many more users than the one with differential phase-shift-keying (DPSK).
Abstract: In comparing two proposed frequency-hopping mobile radio systems for digitized speech, Goodman et al. have observed that the system employing multiple frequency-shift keying (MFSK) can accommodate many more users than the one with differential phase-shift keying (DPSK). Besides the difference in modulation methods, the MFSK system uses hard-limited combining while the DPSK one uses linear combining. Upper bounds are obtained on the probability of error for DPSK systems with hard-limited combining and linear combining. These bounds suggest that the DPSK system with hard limiters can support about twice as many users as the original one.

Journal ArticleDOI
L. Jasinski1
TL;DR: In this paper, a statistical method is developed for analysis of interference in land mobile communications systems, which is applicable to any frequency band for which path loss statistics are known, and an example of this method is given which calculates reduction in communication range, area, and degradation of communication reliability for different values of splatter protection, and distributions of mobile units.
Abstract: A statistical method is developed for analysis of interference in land mobile communications systems Reduction of communication range and degradation of system reliability are calculated This method can be used for cases in which a desired signal is transmitted by a base station (or mobile unit) and received by a mobile unit (or base station) and is interfered with by a signal transmitted either by a fixed station or a mobile unit The spatial probability distribution of mobile units is considered The method is applicable to any frequency band for which path loss statistics are known, and an example of this method is given which calculates reduction in communication range, area, and degradation of communication reliability for different values of splatter protection, and distributions of mobile units

Journal ArticleDOI
K. Tomiyasu1
TL;DR: The conceptual advantage of a bistatic radar compared to a monostatic radar is shown and examples are given to show the conceptual advantage.
Abstract: A monostatic Doppler radar can yield accurate vehicle speed measurements over a very limited angular extent When applied to a multilane superhighway geometry, the area within which the vehicle must be confined for accurate measurement becomes quite small A much larger area yielding accurate measurement can be achieved by designing the radar system for bistatic operation In this geometry the transmitter and receiver are on opposite sides of the multilane highway and both transmitting and receiving antenna beams are oriented towards the vehicle A radiation leakage link is required between transmitter and receiver to provide a reference frequency signal Examples are given to show the conceptual advantage of a bistatic radar compared to a monostatic radar

Journal ArticleDOI
TL;DR: A critical survey of the status and technical and economic conclusions of these investigations, including a perspective of the relative roles of private and public enterprise, is presented in this article, where a critical survey is presented.
Abstract: Last decade's major expansion of mobile communications has prompted investigations by NASA into the potential role of space technology in alleviating spectrum crowding and other constraints resulting from this growth. A critical survey is presented of the status and the technical and economic conclusions of these investigations, including a perspective of the relative roles of private and public enterprise.

Journal ArticleDOI
P.J. Mabey1
TL;DR: Some of the factors affecting the design of a binary signaling format for high capacity wide area digital radio paging are discussed and synchronization, battery economy techniques, error control coding, and the choice of bit rate are considered.
Abstract: Some of the factors affecting the design of a binary signaling format for high capacity wide area digital radio paging are discussed. Topics considered are synchronization, battery economy techniques, error control coding to ensure acceptable success and false call rates, and the choice of bit rate. Paging successful and false call rates of typical format are predicted for moving and stationary pagers in environment of multipath propagation and shadowing.

Journal ArticleDOI
TL;DR: A new technique which provides increased capacity in a direct-sequence spread-spectrum system is described, which makes use of the Hilbert transform of the spreading sequence to provide an extra degree of orthogonality.
Abstract: A new technique which provides increased capacity in a direct-sequence spread-spectrum system is described. The technique makes use of the Hilbert transform of the spreading sequence to provide an extra degree of orthogonality. The crosstalk between the various signals is shown to be negligible, and the performance of the system when operating in the presence of a tone interfering signal is derived. Methods of achieving synchronization are discussed and experimental results showing all key waveforms are presented.

Journal ArticleDOI
TL;DR: The history of the IEEE is traced from its establishment in 1949 as the Vehicular and Railroad Communications Professional Group, through its existence as the Professional Group on Vehicular Communications, (PGVC), and up to its present role in mobile communications, automotive technology, and transportation systems.
Abstract: The history of the Vehicular Technology Society (VTS), Institute of Electrical and Electronics Engineers, Inc. (IEEE) is traced from its establishment in 1949 as the Vehicular and Railroad Communications Professional Group, through its existence as the Professional Group on Vehicular Communications, (PGVC), and up to its present role in mobile communications, automotive technology, and transportation systems.

Journal ArticleDOI
TL;DR: The delay encountered by vehicles waiting to merge is considered and tight upper bounds on the probability of delay are derived based on a "gap acceptance" model.
Abstract: The delay encountered by vehicles waiting to merge is considered. Tight upper bounds on the probability of delay are derived based on a "gap acceptance" model. The general approach is developed, and specific results of some interest are presented.

Journal ArticleDOI
TL;DR: It is pointed out that, except for some minor changes, the above paper1is a true copy of an earlier correspondence by En, and that the code presented should not be recommended.
Abstract: It is pointed out that, except for some minor changes, the above paper1is a true copy of an earlier correspondence by En, and that the code presented should not be recommended.