Showing papers in "IEEE Transactions on Vehicular Technology in 1985"
TL;DR: A statistical model for a land mobile satellite link that assumes that the amplitude of the line-of-sight component under foliage attenuation (shadowing) is lognormally distributed and the received multipath interference has a Rayleigh distribution is described.
Abstract: A statistical model for a land mobile satellite link is described. The model assumes that the amplitude of the line-of-sight component under foliage attenuation (shadowing) is lognormally distributed and the received multipath interference has a Rayleigh distribution. Expressions for the level crossing rate and average fade duration are given. Comparison between results calculated from the model and from measurements show reasonably good agreement. The model should be useful for designing communications systems and for simulating propagation effects in the laboratory.
678 citations
TL;DR: In this paper, the procedure for obtaining the local average power (also called local mean) of a mobile radio signal is described, which is based on the Rayleigh distribution and can be treated as a standard procedure.
Abstract: The procedure for obtaining the local average power (also called local mean) of a mobile radio signal is described. The measured length of a mobile radio signal necessary to obtain the local average power is determined to be in the range of 20 to 40 wavelengths. It is based on the Rayleigh distribution. The sufficient number of samples for estimating the local average power values is about 36. It is based on a 90 percent confidence interval and less than 1 dB error in estimate. This procedure of estimate can be treated as a standard procedure.
352 citations
TL;DR: In this article, a predistortion (PD) circuit was developed to compensate for third-order intermodulation (IM) distortion generated in the power amplifier of microwave transistor amplifiers.
Abstract: New relay equipment for a tunnel relay system used in an 800 MHz band land mobile telephone network has been developed Significant improvements in size and power consumption have been achieved using a predistortion (PD) circuit to compensate for third-order intermodulation (IM) distortion generated in the power amplifier This predistortion circuit features a simple configuration and easy adjustment, as well as high distortion reduction performance The circuit configuration is derived from an analysis based on a complex power series representation of input-output nonlinearities for microwave transistor amplifiers This analysis shows that two kinds of nonlinearities, AM-AM and AM-PM conversions, are uniquely related through the third-order distortion phase, In addition, an automatically controlled predistortion system is introduced to establish an adjustment and maintenance-free compensator Using the developed predistortion circuit, a stable distortion reduction of more than 20 dB per 25 MHz bandwidth has been attained
127 citations
TL;DR: In this paper, the authors proposed a system to provide high quality ubiquitous service to low power portable radiotelephones and data terminals using frequency reuse radio system configurations applicable to residential and large building environments along with multipath and other 800 MHz radio propagation limitations.
Abstract: In our highly mobile society, the provision of voice and data communications to people away from their wireline telephones has become a major communications frontier Some emerging radio systems, eg, cellular mobile radio, cordless telephone, and radio paging, have begun to penetrate this frontier However, each of these approaches only partially satisfies portable communication needs That is, the approaches do not provide overall portable communication service Some of the problems involved and the technologies and system configurations needed for an advanced radio communications system are discussed The goal for the system is to provide high quality ubiquitous service to low power portable radiotelephones and data terminals Frequency reuse radio system configurations applicable to residential and large building environments will be described along with multipath and other 800 MHz radio propagation limitations The system would use fixed radio ports attached to the telephone network and spaced about 2000 ft in residential areas The residential ports would have antenna heights of less than 30 ft The horizontal spacing of ports within large buildings would be 200 ft or more In service areas, more than 99 percent radio link availability would be provided for 5 mW portable transmitters
107 citations
TL;DR: The method proposed by Hata, based on Okumura's results, and Allsebrook and Parsons' model, which provides an easy way to take into account the influence of buildings are the most complete and it is suggested to use them with the inclusion of an estimation of diffraction losses due to terrain.
Abstract: A number of statistical models are available in the literature for the prediction and the calculation of transmission loss, but the main differences between them as well as their usefulness in a particular situation is not easy to assess. In this article, the experimental results of Okumura, as seen through the empirical expression derived by Hata, are compared with the models of Egli, Edwards and Durkin, Blomquist and Ladell, and Allsebrook and Parsons. Comparisons are made for the case of an open region and flat terrain, first without and then with inclusion of a statistical estimation of diffraction losses due to terrain in the models of Blomquist and Ladell, Edwards and Durkin, and Allsebrook and Parsons. The study is also extended to cover the case of irregular terrain and urban areas. The method proposed by Hata, based on Okumura's results, and Allsebrook and Parsons' model, which provides an easy way to take into account the influence of buildings are the most complete and it is suggested to use them with the inclusion, as required, of an estimation of diffraction losses due to terrain. As a conclusion, experimental propagation loss measurements taken in the Ottawa region at 910 MHz are presented and are found to fall very nicely in the range predicted by the above-mentioned methods.
59 citations
TL;DR: In this article, a methodology for designing an automated vehicle longitudinal controller is presented and applied to an automobile characterized by velocity-dependent dynamics, which consists of a cascade compensator, which is selected to achieve small tracking errors, and an observer/controller compensator.
Abstract: A methodology for designing an automated vehicle longitudinal controller is presented and applied to an automobile characterized by velocity-dependent dynamics. The design consists of a cascade compensator, which is selected to achieve small tracking errors, and an observer/controller compensator. The controller portion was designed to achieve a velocity-invariant response, and the observer to derive the state-feedback signals. Both compensators were realized on an eight-bit microcomputer, and the vehicle dynamics were simulated on an analog computer. The performance of the resulting system was evaluated using a large-signal, entry merging command and small-signal mainline commands. Excellent results were obtained with typical values being a maximum position error of 0.63 m during an entry maneuver and 0.15 m during a mainline maneuver; however, the designed system was sensitive to large changes in critical vehicle parameters. Thus, there is a need to modify the controller so that it can adaptively compensate for such changes. Then, the designed digital controller, with its flexibility to perform other functions and its ease of reliability enhancement, is an attractive candidate for implementation, and at the very least, indicates the type of longitudinal performance one can expect from a realistically designed controller over the speed range 0-30 m/s.
40 citations
TL;DR: In this article, the power spectrum of Gaussian-filtered minimum-shift keying (GMSK) modulation can be made compact, at the sacrifice of co-channel interference protection.
Abstract: Gaussian-filtered minimum-shift keying (GMSK) is a constant envelope and narrow-band modulation suitable for power- and band-limited digital radio communication. From the viewpoint of efficient spectrum use by land mobile radio, geographical reuse of cochannels as well as power spectrum compactness are desired. The output power spectrum of GMSK modulation can be made compact, at a sacrifice of co-channel interference protection. Parameters for optimizing GMSK are determined maintaining a compromise between co-channel reuse and power spectrum compactness.
38 citations
TL;DR: A simple method is proposed to remove random FM from a fast Rayleigh faded binary phase shift keying (BPSK) signal and the great improved performance of reducing the irreducible error is presented.
Abstract: A simple method is proposed to remove random FM from a fast Rayleigh faded binary phase shift keying (BPSK) signal and the great improved performance of reducing the irreducible error is presented. In the mobile radio environment, there happens inevitably a fast Rayleigh fading which causes random FM. The phase error of the reference signal due to random FM will degrade the bit error rate (BER) performance, even if the signal-to-noise ratio is sufficiently high. In the realization of reliable mobile communication, removal of this random FM is an unavoidable theme. Proposed strategy is to transmit a sounding continuous wave (CW) together with a BPSK signal, each phase being kept orthogonal and each power being kept the same. This CW wave is also used as the reference signal in coherent reception. The BER performance of this system is worse by 3 dB than that of the coherent BPSK in a slow Rayleigh fading environment.
36 citations
TL;DR: In this article, the internal electric field and energy deposition in a full-size adult male mannequin in the immediate vicinity of 1.5 W body-mounted communication transceivers have been measured.
Abstract: The internal electric (E) field and energy deposition in a full-size adult male mannequin in the immediate vicinity of 1.5 W body-mounted communication transceivers have been measured. Transceivers operating at the four frequencies 50, 150, 450, and 800 MHz, and placed at various locations vis-a-vis the body were used. The mannequin was filled with two-thirds muscle-simulant biological phantom mixtures at each of the four frequencies. The complex permittivities (e*) of these mixtures were confirmed by measurement. The internal E-field distribution was measured by three-dimensional implantable E-field probes. Relatively superficial energy depositions were obtained at points close to the location of the transceiver antenna for the two higher frequencies with energy depositions typically less than 1-2 W/kg. Considerably reduced energy depositions were measured at the two lower frequencies on account of in-depth and wider dissemination of the absorbed energy and the relatively high e*of the tissues which results in an increased shielding of the body.
35 citations
TL;DR: It is determined that the excess path loss, or fade margin, of a Rician channel will change the envelope statistics of the received waveform from Rayleigh to a more favorable Rician distribution when coherent detection of binary phase shiftkeying or quaternary phase shift keying signals is considered.
Abstract: Excess path loss due to multipath severely restricts the performance of power limited mobile networks such as those using satellite-aided links. To reduce multipath related losses, the higher elevation angle of the spacecraft can be exploited by utilizing mobile antennas which reduce the strength of the multipath reflections in favor of the line-of-sight signal. The presence of a strong and stable path in a fading link will change the envelope statistics of the received waveform from Rayleigh to a more favorable Rician distribution. It is determined that the excess path loss, or fade margin, of a Rician channel when coherent detection of binary phase shift keying (BPSK) or quaternary phase shift keying (QPSK) signals is considered. The results are presented parametrically such that they can be applied to a wide range of propagation characteristics from heavy fading to nonfading situations. Furthermore, similar results are also given for the case where only limited coverage is provided.
32 citations
TL;DR: Signal levels around and within four suburban houses were measured at 800 MHz by an instrumentation van having erectable 27-ft and 125-ft-high antennas as discussed by the authors, and the dependence of attenuation on the height of antennas is needed in designing portable radio communication systems that can accommodate low-power radio communication sets.
Abstract: Signal levels around and within four suburban houses were measured at 800 MHz The measurements were made from an instrumentation van having erectable 27-ft and 125-ft-high antennas The dependence of attenuation on the height of antennas is needed in designing portable radio communication systems that can accommodate low-power radio communication sets The height dependence of the trends in the data are consistent with the simple model of reflection from the ground
TL;DR: In this paper, a phase-locked transparent tone-in-band (TTIB) was proposed to achieve coherent data transmission in the presence of Rayleigh fading without the usual "high-level" irreducible error rates.
Abstract: The transmission of speech and data over 942 MHz pilot tone single sideband (SSB) mobile radio links is the main concern of this paper. It has been found that the use of feedforward signal regeneration enables a speech quality to be obtained in the Rayleigh fading environment which is superior to that achieved by a 25 kHz Advanced Mobile Phone Service (AMPS) type FM system and markedly superior to that obtained with a 12.5 kHz FM system. A new optimized form of SSB, phase-locked transparent tone-in-band (TTIB), is shown to be capable of achieving coherent data transmission such as M-ary phase shift keying (PSK) in the presence of Rayleigh fading without the usual "high-level" irreducible error rates. The signal processing described has wide application from line to satellite communications.
TL;DR: The autocorrelation function (acf) of a stochastic Rician fading process is numerically evaluated, and useful approximations are given.
Abstract: The autocorrelation function (acf) of a stochastic Rician fading process is numerically evaluated, and useful approximations are given. The spectral properties of the fading are related to the component processes constituting the fading process. The result is that for Rayleigh fading and first-order Butterworth characteristic of the component processes the fading bandwidth is double the component bandwidth. The fading bandwidth decreases to the component bandwidth, however, when the Gaussian channel is approached or when high-order faltered components are assumed.
TL;DR: In this paper, the design and performance of a single-chip minimum shift keying (MSK) coherent demodulator fabricated by complementary metal oxide semiconductor-integrated circuit (CMOS-IC) technology is described.
Abstract: Design and performance of a single-chip minimum shift keying (MSK) coherent demodulator fabricated by complementary metal oxide semiconductor-integrated circuit (CMOS-IC) technology is described. The demodulator consists of a phase detection circuit, carrier recovery circuit, data recovery circuit, and timing-clock recovery circuit. For the carrier recovery circuit, three types of Costas-loop are reviewed from the viewpoint that MSK modulation format has a close relationship to binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK). Among these loops, a loop of center-frequency locking scheme modified from a BPSK Costas-loop, termed MSK Costas-loop in this paper, is adopted for IC implementation. Digital IC design techniques are next described. Utilizing the sample-and-hold operation of the digital devices, a divided-frequency locking scheme of the quadrature coherent demodulation is proposed. Finally, IC demodulator performance is experimentally shown in the static and Rayleigh fading environments. The bit error rate performance and error-burst characteristic are measured. It is concluded that the single-chip coherent demodulator is suitable for digital mobile radio application.
TL;DR: In this paper, co-channel reuse rules in two dimensions were reviewed and extended to three dimensions, and it was shown that a much larger N will be needed in three dimensions.
Abstract: Ubiquitous use of low-power hand-held radiotelephone units will introduce a third dimension into channel assignment architecture. Co-channel reuse rules in two dimensions are reviewed and extended to three dimensions. Rules for generating N (number of channel sets) and D/R (which affects median signal-to-interference ratio) are developed for several three-dimensional geometries. It is shown that in three dimensions, a much larger N will be needed. However, other factors which may mitigate this are discussed.
TL;DR: The analysis clarified the multipath conditions causing severe distortions and also the mechanisms of eye pattern degradation, showing the superiority of BPSK in multipath tolerance.
Abstract: In a digital mobile radio transmission, long-delayed multi-path propagation causes frequency selective fading, resulting in signal waveform distortion and hence bit error rate (BER) degradation. Comparison of multipath distortion among various digital modulation techniques (binary, quaternary, offset quaternary, and minimum phase shift keying (BPSK, QPSK, OQPSK and MSK)) is made using a two-ray propagation model, which is a fundamental model to evaluate multipath tolerant capability. The analysis clarified the multipath conditions causing severe distortions and also the mechanisms of eye pattern degradation, showing the superiority of BPSK in multipath tolerance.
TL;DR: In this article, the power gain radiation patterns of mobile antennas mounted in six different locations on a test vehicle were measured with and without typical lights and sirens mounted on the roof.
Abstract: Power gain radiation patterns of mobile antennas mounted in six different locations on a test vehicle were measured with and without typical lights and sirens mounted on the roof. The measurements were performed at frequencies representing the frequency bands of 25 to 50, 150 to 174, 400 to 512, and 806 to 866 MHz. In addition, special antennas consisting of three disguised antennas operating at discrete frequencies of 40.27, 162.475, and 416.975 MHz and one slot antenna operating at 413 MHz were also measured. Plots of power gain radiation patterns are given for the mobile antennas mounted in six different locations on the test vehicle and for the special antennas. Results showing the effects of poor grounding characteristics are also included. Recommended locations for mounting the mobile antennas are given for specific frequency bands.
TL;DR: In this article, a comparison of current prediction techniques available in the literature (for slow lognormal fading rather than multipath Rayleigh fading), with an emphasis on three essential criteria to consider in the selection process: the type of terrain or geography covered by each method, the form of prediction provided, and the implementation difficulty and degree of sophistication.
Abstract: The design and installation of a mobile radio system involves the evaluation or prediction of the propagation characteristics associated with the geographical area of interest. A wide variety of prediction techniques has been developed for different mobile environments, so that the task of selecting an appropriate propagation prediction method can be difficult and complex. This is especially true for systems operating in the upper-UHF band of 800-950 MHz, where mobile radio services are rapidly growing. A practical comparison is given of current prediction techniques available in the literature (for slow lognormal fading rather than multipath Rayleigh fading), with an emphasis on three essential criteria to consider in the selection process: the type of terrain or geography covered by each method, the form of prediction provided (e.g., transmission loss estimates, field strength contour maps, etc.), and the implementation difficulty and degree of sophistication.
TL;DR: A modeling approach to the problem of channel sharing in land mobile radio dispatch services, which is based on real life traffic data, is presented and it is shown how to use simple approximation formulas to evaluate the expected waiting time, when two or more independent users must share a common channel.
Abstract: A modeling approach to the problem of channel sharing in land mobile radio dispatch services, which is based on real life traffic data, is presented. In order to apply the GI/G/1 queueing model, the first step consists in identifying a message arrival process for each user by means of observed available data. It is then shown how to use simple approximation formulas to evaluate the expected waiting time, when two or more independent users must share a common channel. GPSS simulations were performed to verify that the proposed approach is suitable to practical applications.
TL;DR: Cellular zone design parameters for a land mobile communication system are clarified and system parameters having a strong influence on cellular system performance are discussed and some problems encountered when system parameters are changed are examined.
Abstract: Cellular zone design parameters for a land mobile communication system are clarified. System parameters having a strong influence on cellular system performance are discussed and some problems encountered when system parameters are changed are examined.
TL;DR: This correspondence shows that the analysis provided by Yokoyama can be drastically simplified.
Abstract: M. Yokoyama describes a binary phase shift keying (BPSK) system that by utilizing a sounder removes the error floor associated with Rayleigh faded signals. This correspondence shows that the analysis provided by Yokoyama can be drastically simplified.
TL;DR: With synchronization between sequences at the chip level, the results show binary FH-FSK performance comparable to that of frequency-hopped multilevel frequency shift keying (FH-MFSK) and thus, substantially better than that of Fh-DPSK.
Abstract: A binary frequency-hopped frequency shift keying (FHFSK) spread spectrum system for mobile radio communication as well as an address assignment scheme for such a system and an evaluation of error probabilities due to mutual interferences in binary FH-FSK in function of the number of simultaneous users are presented. In the absence of any form of synchronization between sequences, the system's performance is not as good as frequency-hopped differential phase shift keying (FH-DPSK) for any decoding scheme; decoding with intermediate decisions on interval pairs (i, i + L/2) in a sequence of length L gives approximately the same performance as when using only the combiner circuit and maximum likelihood decoding. With synchronization between sequences at the chip level, however, the results show binary FH-FSK performance comparable to that of frequency-hopped multilevel frequency shift keying (FH-MFSK) and thus, substantially better than that of FH-DPSK.
TL;DR: Alternative inversion methods are analyzed and the optimum method, entitled "dual inversion with down-shift," reduced the increase in system noise performance to 0.99 dB for a small increase in residual intelligibility.
Abstract: Frequency inversion of the voice spectrum is a common method of providing simple privacy on single channel radio links. When combined with exponential modulation this method produces an increase in system noise of 8.00 dB. Alternative inversion methods are analyzed. The methods involve partitioning the voice spectrum into two halves, inverting one or both of these halves and, in some cases, incorporating a bandshift. The optimum method, entitled "dual inversion with down-shift," reduced the increase in system noise performance to 0.99 dB for a small increase in residual intelligibility. This was measured at 36 percent using a voice test incorporating digit identification. Frequency inversion had a residual intelligibility of 31 percent.
TL;DR: An analysis of the effect of multiple tone interferers on the bit error rate in a Frequency-Hopped Multiple Frequency Shift Keying (FH-MFSK) spread spectrum communication is given and shows that adequate performance can be achieved even when 40tone interferers are present.
Abstract: An analysis of the effect of multiple tone interferers on the bit error rate (BER) in a frequency-hopped multiple frequency shift keying (FH-MFSK) spread spectrum communication is given. A constant insertion rate detection strategy has been considered and a matched tuned filtering used in the receiver. We have obtained results in the 20 MHz (one-way) bandwidth with a data rate of 32 kbit/s and a Rayleigh fading channel. The results show that adequate performance can be achieved even when 40 tone interferers are present with a signal to interference ratio of -10 dB and a signal-to-noise ratio of 25 dB.
TL;DR: In this article, a computer-based piecewise linear technique is used to analyze the transient responses, taking the full account of nonlinearities such as the magnetic saturation and the product of variable terms.
Abstract: The possible modes of operation are explained and the dynamic equations for the combined regenerative and rheostatic braking of dc chopper controlled series motor are derived. A computer-based piecewise linear technique is used to analyze the transient responses, taking the full account of nonlinearities such as the magnetic saturation and the product of variable terms. The responses in the transient conditions, which occur in practical situations, are predicted by a computer model and are compared with the practical measurement.