Showing papers in "IEEE Transactions on Vehicular Technology in 1986"
TL;DR: A traffic model and analysis for cellular mobile radio telephone systems with handoff, which shows, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters.
Abstract: A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented.
1,654Â citations
TL;DR: Lower bounds for the number of frequencies required by solutions of certain frequency assignment problems were derived in this article, which constitute generalizations of the clique number to problems including adjacent channel and co-site constraints as well as preassigned and blocked frequencies.
Abstract: Lower bounds for the number of frequencies required by solutions of certain frequency assignment problems are derived. The bounds constitute generalizations of the clique number, which appears in the pure co-channel case, to problems including adjacent channel and co-site constraints as well as preassigned and blocked frequencies. Examples of mobile telephone systems are studied with the aid of these bounds.
400Â citations
TL;DR: A statistical model applicable to a local area has been developed for mobile-to-mobile urban and suburban land communication channels and the probability distributions of the received envelope and phase, spatial-time correlation function, and the power spectral density of the complex envelope have been developed.
Abstract: A statistical model applicable to a local area has been developed for mobile-to-mobile urban and suburban land communication channels. Using the model, the probability distributions of the received envelope and phase, spatial-time correlation function, and the power spectral density of the complex envelope have been developed.
389Â citations
TL;DR: In this article, the authors use the co-channel interference reduction factor as a design criterion and predict the signal-to-interference (S/I) ratios in different system configurations.
Abstract: A major concern in a cellular mobile radio system is the co-channel interference. Therefore, the reduction of co-channel interference becomes a main thrust for the system design engineers. We use the co-channel interference reduction factor as a design criterion and predict the signal-to-interference (S/I) ratios in different system configurations. The handoff mechanism and algorithmic considerations, the traffic capacity and procedure for splitting cells, and the near-end-to-far-end ratio interference and reduction are the elements described.
171Â citations
TL;DR: In this article, 1.2 GHz band radio wave propagation characteristics in a concrete building were investigated for the design of indoor radio communication or a portable radio telephone system, including the penetration loss through a window, local median variations, and cumulative distributions of received signal levels in a room, reflection coefficient or equivalent dielectric constant and transmission loss of a wall/floor.
Abstract: For the design of indoor radio communication or a portable radio telephone system, 1.2 GHz band radio wave propagation characteristics are investigated in a concrete building. Penetration loss through a window, local median variations, and cumulative distributions of received signal levels in a room, reflection coefficient or equivalent dielectric constant and transmission loss of a wall/floor are discussed.
85Â citations
TL;DR: The operation and performance of the dual-pilot tone calibration technique (DPTCT) are analyzed, and its effectiveness is compared to that of the single tone TCT technique.
Abstract: Pilot-based calibration techniques are used to reduce the effects of multipath fading in mobile satellite receivers. One of the more recent of these techniques, namely the tone calibration technique (TCT), suggests transmitting double sideband modulation with the pilot tone located at the center of its spectrum where the amplitude and phase characteristics of the channel are most stable. To "make room" for the pilot in the presence of the Doppler shift, the equivalent low-pass data sidebands must be shaped so as to have zero response in the neighborhood of dc. Other techniques such as transparent tone-in-band (TTIB) similarly "notch out" a hole in the center of the data spectrum for location of the pilot. An alternate possibility which is at the same time much more bandwidth efficient than TCT is a dual-pilot tone calibration technique (DPTCT) that symmetrically locates a pair of pilots outside the data spectrum near the band edges of the channel. The operation and performance of DPTCT are analyzed, and its effectiveness is compared to that of the single tone TCT technique.
73Â citations
TL;DR: Discriminator detection of Gaussian MSK in land mobile radio environment is analyzed and simple closed form expressions for the average probability of error are presented and evaluated for cases of practical interest.
Abstract: Discriminator detection of Gaussian minimum shift keying in a land mobile radio environment is analyzed. Simple closed-form expressions for the average probability of error are presented and evaluated for cases of practical interest.
67Â citations
TL;DR: The signals in mobile communications are reviewed both in terms of the physical scenario and as the basis of the transfer function of the mobile channel to demonstrate the inherent limitations resulting from using single port antennas, in both narrow- and wide-band systems.
Abstract: The signals in mobile communications are reviewed both in terms of the physical scenario and as the basis of the transfer function of the mobile channel. The transfer function is arranged to demonstrate the inherent limitations (the irreducible bit error rate effect) resulting from using single port antennas, in both narrow- and wide-band systems. A new model for the average source scenario at the urban-based (vehicular) mobile is determined and an analogous model for the base station is formulated. The models are useful for deriving diversity antennas.
67Â citations
TL;DR: The effect of intersymbol interference of Gaussian filtered minimum shift keying of GMSK on the probability of error of one bit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels.
Abstract: The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of one bit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed-form expression is derived for the probability of error as a function of the fading rate, IF filter bandwidth, signal-to-noise ratio (SNR) and ISI. Numerical results are presented for cases of practical interest to researchers and designers of cellular land mobile radio systems.
56Â citations
TL;DR: It is shown that partial-response CPM schemes with good performance can also be obtained with noncoherent detectors, both for differential and discriminator detection.
Abstract: Recently, bandwidth efficient constant-amplitude digital modulation schemes have also been shown to be power efficient when coherent detection is used. Partial-response continuous phase modulation (CPM) schemes are within this class. In some applications noncoherent detection is preferred. The performance of CPM systems is analyzed for differential and discriminator detection. An additive white Gaussian channel is assumed. The detectors make symbol-by-symbol decisions. The considered schemes are M-ary with an arbitrary modulation index and pulse shaping over several symbol intervals. The performance is analyzed by means of error probability expressions. The IF filter for the detectors is optimized within a special class of filters to give good performance. The differential detector is also analyzed on a Rayleigh fading channel. The fading is assumed to be slow. The IF filter is also optimized on this channel. Simulated error probabilities for discriminator detection with a Viterbi detector are also presented both for the Gaussian and the Rayleigh fading channel. The discriminator detector making symbol-by-symbol decisions is simulated on the Rayleigh fading channel. It is shown that partial-response CPM schemes with good performance can also be obtained with noncoherent detectors.
49Â citations
TL;DR: In this paper, the classic technology of the saturable core may be combined with the microcomputer to yield an improved version of the magnetic flux-gate compass, with application to mass-produced automobiles.
Abstract: The classic technology of the saturable core may be combined with the microcomputer to yield an improved version of the magnetic flux-gate compass. General description and fundamental principles are discussed with application to mass-produced automobiles. A transfer function between the earth's magnetic field and the fluxgate output voltages is developed. The introduction of the microcomputer allows a faster calibration which does not require any type of nulling or feedback circuit.
TL;DR: The analyses have revealed that BER performance markedly depends on the choice of sample timing, and also an interesting fact that BPSK is outstanding in the multipath-distortion tolerance, if coupled with adaptive sampling, and its BER curves remain almost the same as that of frequency-flat fading as long as multipath delay difference is less than a bit interval.
Abstract: Digital mobile radio often suffers from fatal effects caused by frequency-selective fading, resulting in severe bit error rate (BER) degradation. The feasibility of digital mobile radio largely depends on the multipath-distortion tolerant capability of modulation technique. The BER performance is compared among four digital modulation techniques in a frequency selective fading channel with large multipath delay spread. In particular, taking the timing fluctuation of eye patterns due to delay distortion of a fading channel into account, the effect of sample timing on BER is analyzed. The analyses have revealed that BER performance markedly depends on the choice of sample timing, and also an interesting fact that BPSK is outstanding in the multipath-distortion tolerance, if coupled with adaptive sampling, and its BER curves remain almost the same as that of frequency-flat fading as long as multipath delay difference is less than a bit interval.
TL;DR: It is seen that in a fading environment space diversity is very effective in bringing down the threshold of channel SNR to maintain the required audio SNR.
Abstract: The performance of a speech transmission scheme with application to cellular digital mobile radio systems is considered The source coder is embedded differential pulse code modulation (DPCM) and the modulation schemes belong to the class of partial response continuous phase modulation (CPM) Both quantizing noise and transmission errors contribute to the overall mean square error The performance measure is the audio signal-to-noise ratio (SNR) It is seen that in a fading environment space diversity is very effective in bringing down the threshold of channel SNR to maintain the required audio SNR The number of channels the system can support is evaluated under various conditions
TL;DR: In this paper, a real zero single sideband (RZ SSB) transceiver is proposed for mobile radio services, where an amplitude limiter can be used without degrading the quality of detected output signals in the receiver.
Abstract: A real zero single sideband (RZ SSB) transceiver is newly proposed for mobile radio services. The necessary transmission bandwidth of RZ SSB is similar to that of a conventional SSB. In this new transceiver, an amplitude limiter, which can remove the amplitude impairment, can be used without degrading the quality of detected output signals in the receiver. Furthermore, since RZ SSB signals possess FM-like characteristics, they can be demodulated with frequency detection as well as product detection.
TL;DR: The computations of the probability of error for a differential phase shift keying (DPSK) modulation scheme in the presence of frequency selective fading show the dominance of this factor as the signal-to-noise ratio (SNR) increases.
Abstract: An experiment has been designed to determine the frequency selective behavior of a mobile radio channel for a medium bandwidth (maximum of 128 kHz). The measurement technique uses a multitone approach. The transmitted signal consists of several tones (five) with fixed phase and amplitude relationships. Coherent demodulation and separation of each tone is performed at the receiving end. Quantification of the mobile radio channel is conveniently described by its frequency correlation function. Measurements for several types of environments (rural, suburban, urban) were taken and analyzed. The results characterize the amplitude and phase behaviors of a signal for each type of environment. Finally, the computations of the probability of error for a differential phase shift keying (DPSK) modulation scheme in the presence of frequency selective fading show the dominance of this factor as the signal-to-noise ratio (SNR) increases.
TL;DR: In this article, a model was developed and solved which captures the essence of the concept of mobile dispatch service, where two types of users, dispatch and interconnect (calls routed from the public switched telephone network, of much longer holding times).
Abstract: A model has been developed and solved which captures the essence of the concept of mobile dispatch service. There are two types of users, dispatch and interconnect (calls routed from the public switched telephone network, of much longer holding times). Also, only some of the available repeaters can be used for interconnect traffic, and blocked interconnect calls are cleared. Dispatch calls, however, can access all repeaters, and then are queued if all repeaters are busy. One design decision involves a trade between blocking of interconnect calls and queueing of dispatch calls. A formula has been derived for both interconnect blocking probability and the mean dispatch queueing time to permit this trade. The results indicate that a good operating point is to have (N - a d )(rounded down) interconnected repeaters, where there are N total repeaters and a d Erlangs of dispatch traffic.
TL;DR: This work has attempted to describe a novel spectrum-efficient frequency allocation scheme that provides an operation which is free from co-channel interference as well as intracell adjacent channel and two-signal third-order intermodulation interference.
Abstract: A large volume of work has been devoted to searching for a better frequency assignment scheme to handle varying traffic loads in a cellular radio system. However, very little has been accomplished in designing a spectrum-efficient interference-free frequency allocation scheme for this type of system. It is attempted to describe a novel spectrum-efficient frequency allocation scheme that provides an operation which is free from co-channel interference as well as intracell adjacent channel and two-signal third-order intermodulation interference. The proposed scheme is fundamentally different from the existing cellular frequency assignment schemes in which traffic loading is considered without taking interference into account. In the design, we assume that the traffic is uniform in all the cells of the cellular system and there are the same number of channels in each cell.
TL;DR: In this paper, a theoretical model of an automobile body was developed in conjunction with the geometrical theory of diffraction (GTD) in order to calculate vertical plane patterns of quarter wavelength monopole and a half-wavelength dipole located on an automobile's roof.
Abstract: Theoretical and experimental studies are made on radiation patterns of mobile antennas within the frequency range from 300 to 900 MHz. In order to calculate vertical plane patterns of quarter wavelength monopole and a half-wavelength dipole located on an automobile's roof, a theoretical model of an automobile body is developed, in conjunction with the geometrical theory of diffraction (GTD). The theoretical model consists of three-perfectly conducting plates. It is ascertained from a comparison between calculated and measured results for the feed point impedance and the radiation pattern that the effect of the body and the earth can be well examined with the theoretical model. The results of pattern calculation for the above two antennas show that the radiation patterns depend largely on the configuration of the automobile body and the earth condition. The technique described in this paper can be used as a design tool to estimate radiation performance of mobile antennas.
TL;DR: In this paper, a self-adaptive electronic injection system is presented, both the theory of operation and the development of an experimental prototype are discussed in detail, and experimental results are reported to demonstrate the validity of the system.
Abstract: A new self-adaptive electronic injection system is presented. Both the theory of operation and the development of an experimental prototype are discussed in detail. Finally, experimental results are reported to demonstrate the validity of the system.
Journal Article•
TL;DR: The San Francisco Municipal Railway (MUNI) fleet of 345 trolleybuses, the largest in North America, is powered by dc motors with switched resistor controllers.
Abstract: The San Francisco Municipal Railway (MUNI) fleet of 345 trolleybuses, the largest in North America, is powered by dc motors with switched resistor controllers. Under an Urban Mass Transportation Administration (UMTA) grant, MUNI conducted a Trolleybus Propulsion Evaluation Program, in which the energy use and performance were measured of the existing switched resistor dc motor controller and three chopper and ac propulsion systems. For each of the systems, tests were conducted on level, medium, and hilly routes, with empty, seated, and crush loads. Graphical analyses are presented, comparing net propulsion energy, regenerated energy, control losses, net motor energy, and rheostatic braking losses for the four systems. Advanced systems are shown to reduce propulsion energy use by an aggregate average of 39 percent compared to the switched resistor controller.