Showing papers in "IEEE Transactions on Vehicular Technology in 1980"
TL;DR: An empirical formula for propagation loss is derived from Okumura's report in order to put his propagation prediction method to computational use.
Abstract: An empirical formula for propagation loss is derived from Okumura's report in order to put his propagation prediction method to computational use. The propagation loss in an urban area is presented in a simple form: A + B log 10 R, where A and B are frequency and antenna height functions and R is the distance. The introduced formula is applicable to system designs for UHF and VHF land mobile radio services, with a small formulation error, under the following conditions: frequency range 100-1500 MHz, distance 1-20 km, base station antenna height 30-200 m, and vehicular antenna height 1-10 m.
2,763 citations
TL;DR: SCAT, the coordinated adaptive traffic signal system, now being installed in Sydney, offers a substantial improvement to movement on arterial roads at low cost thereby enabling usage of the arterial road network to be optimized.
Abstract: Sydney, Australia, just as many major cities in the world, has seen traffic movement become more and more congested despite capital expenditure on road construction and widening, on public transport systems, and on traffic management measures. SCAT, the coordinated adaptive traffic signal system, now being installed in Sydney, offers a substantial improvement to movement on arterial roads at low cost thereby enabling usage of the arterial road network to be optimized. An initial trial on a length of arterial road showed advantages in journey time over optimized fixed-time signal coordination of 35-39 percent in peak periods. SCAT is unique in that it consists entirely of computers and is totally adaptive to traffic demand. Its communication network provides extremely powerful yet flexible management of the system. The system, the system philosophy, and the benefits it is expected to yield are described. The benefits are not only in reduced delay, improved flow, and decreased congestion, but also in reduced accidents, lesser usage of petroleum resources, decreased air pollution, and improved residential amenity.
391 citations
TL;DR: In this article, a mobile location technique using a signal strength measurement scheme is described, and the probability that a mobile is judged to exist in a certain zone (zone selection rate) is defined.
Abstract: In a high-capacity mobile telephone system using cellular technology, a mobile location technique which determines the radio zone in which a moving vehicle exists is one of the most important techniques for the system control. A mobile location technique using a signal strength measurement scheme is described. The probability that a mobile is judged to exist in a certain zone (zone selection rate) is first defined. Dependency of this rate on land mobile propagation characteristics is then discussed in detail. A field test for the justification of this location technique was carried out in the Tokyo metropolitan area in which the field test results agreed well with the estimated values.
166 citations
TL;DR: The Advanced Mobile Phone Service (AMPS) system as discussed by the authors is an FM cellular radio system in the final stages of development, which is described by a brief description of the system and a discussion of the control algorithms which are basic to its operation.
Abstract: The advanced mobile phone service (AMPS) system, an FM cellular radio system in the final stages of development, is described. A brief description of the system is followed by a discussion of the control algorithms which are basic to its operation. Finally, a status report is presented on the Chicago developmental system (an operational cellular system) and the cellular test bed in Newark, NJ (a field laboratory used to evaluate the radio performance of FM cellular systems with cells as small as 1.4-mi radius).
87 citations
TL;DR: In this article, a velocity-adaptive lateral controller is designed to meet requirements pertaining to lateral position tracking accuracy, ride comfort, and an insensitivity to both changes in critical vehicle parameters and disturbance forces.
Abstract: A velocity-adaptive lateral controller is designed to meet requirements pertaining to lateral-position tracking accuracy, ride comfort, and an insensitivity to both changes in critical vehicle parameters and disturbance forces. This controller was tested under full-scale conditions wherein a wire-follower configuration and a dual-mode test vehicle were employed. The latter was automatically steered on straight sections of roadway at speeds up to 35.8 m/s, lane-changing maneuvers were performed up to this speed, and small-radius (100 m) curves were traversed at speeds up to 17.9 m/s. Excellent lateral control, close tracking, good insensitivity to disturbance forces, and a comfortable ride resulted; thus, a relatively simple controller can be effectively employed for nonemergency situations.
50 citations
TL;DR: The results show that the modular structure of the support and guidance system which uses the "magnetic wheel" as a self-contained functional unit is economically feasible within the constraints of existing technology and provides a very promising approach for future tracked high-speed ground transportation systems.
Abstract: The electromagnetic support and guidance system for magnetic levitation railways consists of electromagnets on the vehicle and an armature rail on the track. The experience gained in the operation of the experimental vehicles built so far have lead to the development of a modular structure of the support and guidance system which uses the "magnetic wheel" as a self-contained functional unit. This concept, which is characterized by modular mechanical and electrical structures in connection with decentralized control systems, has made possible a higher reliability by functional redundancy and an improvement of the dynamic characteristics of the vehicle track systems. The results show that such a system is economically feasible within the constraints of existing technology and that it provides a very promising approach for future tracked high-speed ground transportation systems.
42 citations
TL;DR: Large-scale testing of the interactive ALI system (guidance and information system for drivers) is being prepared on an autobahn network in the Ruhr area; the effectiveness of the system, an analysis of cost-benefit, and the effect upon driver acceptance will be determined.
Abstract: Traffic flow has already been improved in the German autobahn network by guidance systems utilizing data collection and calculating forecasts Some examples of this are the remote-controlled traffic signs in the autobahn network Rhein-Main, the congestion warning system on the Aichelherg, and the lane-controlling system of the Frankfurt-Cologne autobahn An improvement of the prediction accuracy can be expected if the destinations of the vehicles are known This is the basic idea of the interactive ALI system (guidance and information system for drivers) After indicating his destination, the driver receives individual information about how to reach the destination in the shortest and easiest way By knowing the destination, the system can improve its prediction ability At this time, such a system of approximately 100 km in length is being prepared on an autobahn network in the Ruhr area; it is being financially supported by the Federal Ministry of Research and Technology, the Federal Minister of Transport, and several participating authorities of Northrhein-Westfalia At 83 cross sections all vehicles will he counted and data will be exchanged with the ALI vehicles This enables one to receive automatic directional information for 32 autobahn exits For testing purposes, 400 vehicles will he fitted with ALI units After considering the current traffic situation, the central computer can arrive at a forecast for this partial stretch of the network For example, if there is a threat of congestion, the computer can modify its program for directional information in the cross sections, thereby informing ALI vehicles as to traveling time, operating costs of the vehicles, as well as the danger of congestion, and the detour route Large-scale testing began in mid-1979, accompanied by a series of tests The effectiveness of the system, an analysis of cost-benefit, and the effect upon driver acceptance will he determined The evaluation of the large-scale testing will he available by mid-1981 This project is being carried out by Blaupunkt-Werke, the consulting engineers Heusch/Boesefeldt, and the Voikswagenwerke AG It is supervised by the Technical Inspection Bureau (TUV), Rheinland
35 citations
TL;DR: In this paper, an experiment conducted with the ATS-6 satellite to determine the additional path loss over free-space loss experienced by land-mobile communication links is described, measured as a function of local environment, vehicle heading, link frequency, satellite elevation angle, and street side.
Abstract: An experiment conducted with the ATS-6 satellite to determine the additional path loss over free-space loss experienced by land-mobile communication links is described. This excess path loss is measured as a function of 1) local environment, 2) vehicle heading, 3) link frequency, 4) satellite elevation angle, and 5) street side. A statistical description of excess loss developed from the data shows that the first two parameters dominate. Excess path loss on the order of 25 dB is typical in urban situations, but decreases to under 10 dB in suburban/rural areas. Spaced antenna selection diversity is found to provide only a slight decrease (4 dB, typically) in the urban excess path loss observed. Level crossing rates are deprsessed in satellite links relative to those of Rayleigh-faded terrestrial links, but increases in average fade durations tend to offset that advantage. The measurements show that the excess path loss difference between 860- MHz links and 1550-MHz links is generally negligible.
35 citations
TL;DR: A model has been developed for waves propagating over a nonflat ground which allows the antenna height effect to be predicted in different types of actual terrain contours, and the theoretically estimated results show good agreement.
Abstract: As is well known, a base-station antenna height gain factor of 6 dB/octave has been predicted theoretically for signal path loss over flat ground and has been verified by measured data. However, the 6-dB/octave rule for antenna height effect cannot be used to predict signal strength for terrain contours if the terrain is not flat. A model has been developed for waves propagating over a nonflat ground which allows the antenna height effect to be predicted in different types of actual terrain contours. In the model, the actual terrain profile is classified as one of two different kinds of general terrain types. The relative received power due to the actual terrain path contour is predicted by considering the reflection points of the waves along the path. Experimental data have been used to verify the theoretically estimated results and they show good agreement.
30 citations
TL;DR: By the use of the classifiers which were found with the above procedure, an on-line program in assembler code was written for a PDP-11/20 minicomputer and gave very satisfactory results.
Abstract: For various applications it is useful to automatically divide vehicles passing a point into several categories. For the method described two inductive loop detectors were used in each lane. The shape of the bottom of a passing car can be assessed by examining the detector's analog signal. This signal, called the "signature," is sampled and fed into a digital computer, which calculates the vehicle's length and some shape factors. The passing vehicles can be separated into five categories: 1) passenger car, 2) delivery van, 3) truck, 4) truck-trailer, and 5) truck-semitrailer. To develop and optimize the method, a "learning set" of 1400 signatures was obtained from known vehicles. To investigate the effectiveness of the method, a "test set" of 950 signatures was gathered. By the use of the classifiers which were found with the above procedure, an on-line program in assembler code was written for a PDP-11/20 minicomputer. The determination of the class can be carried out in approximately 500 µs after a vehicle passes the detector. A trial with the on-line system gave very satisfactory results.
30 citations
TL;DR: This device provides a flexible, easily changed set of simulated channel characteristics, which allows the performance of a mobile radio unit to be evaluated in the laboratory under controlled conditions, and shows excellent agreement with theoretical prediction and documented experimental data.
Abstract: A device to simulate the channel propagation characteristics of the ground mobile environment at UHF has been designed, built, and characterized. This device provides a flexible, easily changed set of simulated channel characteristics, which allows the performance of a mobile radio unit to be evaluated in the laboratory under controlled conditions. The channel simulator was designed to simulate mobile platform speeds up to 675 mi/h and multipath components having differential delays approaching 10 µs. The channel simulator can provide up to four easily selectable, independently fading, multipath components, having calculated time delay spreads of up to 3.5 µs. The adjustable fading bandwidths and the exceptional long delays were implemented using the relative new signal processing technologies of charged-coupled devices and surface wave devices. Envelope statistics such as fading distributions and level crossing rates produced by the channel simulator show excellent agreement with theoretical prediction and documented experimental data.
TL;DR: In this paper, the design of a tunnel relay system in an 800-MHz band land mobile telephone system is described, where several dozen RF signals from a base station or many different mobile units in the tunnel are directly amplified in the RF stage, without frequency conversion, by a common amplifier in the relay equipment installed near the tunnel entrance.
Abstract: System design of a tunnel relay system in an 800-MHz band land mobile telephone system is described. Several dozen RF signals from a base station or many different mobile units in the tunnel are directly amplified in the RF stage, without frequency conversion, by a common amplifier in the relay equipment installed near the tunnel entrance, then radiated into the tunnel through a leaky coaxial cable (LCX) or to the base station by a unidirectional antenna. Repeaters are inserted along the LCX to compensate for transmission loss in RF signal power inside the cable. Amplifying a number of RF signals simultaneously, a common amplifier generates intermodulation products and radiates spurious signals. The required amplifier linearity to suppress the spurious signals is discussed in detail. The combination of LCX and service area in the tunnel is determined according to the amplifier performance, the number of radio channels assigned to the base station, and the radio wave propagation characteristics in the tunnel.
TL;DR: Traffic characteristics of a mobile radio communication system using a dynamic channel assignment scheme which has all channels available at all base stations are derived and some approximation methods are proposed.
Abstract: Traffic characteristics of a mobile radio communication system using a dynamic channel assignment scheme which has all channels available at all base stations are derived. In the system with one channel, the traffic characteristics in each zone are exactly obtained. For a multichannel operation, some approximation methods are proposed and some simple examples are also presented.
TL;DR: The development of the magnetic suspension ground transport system is sponsored by the Federal Ministry for Research and Technology within the scope of the Ground Transport System Technologies program as mentioned in this paper, which began about 1970 and is proceeding in controlled project phases.
Abstract: The characteristics, contingent on magnetic suspension technology, and the research results obtained by now open up the possibility that today's long-distance transport can be improved using the magnetic suspension ground transport system. Besides efficiency and profitability, low influence on the environment, considerable preservation of resources, and a high degree of safety are important developmental objectives. The development of the magnetic suspension ground transport system is sponsored by the Federal Ministry for Research and Technology within the scope of the Ground Transport System Technologies program. It began about 1970 and is proceeding in controlled project phases. The level of the development and selection of components and the functional tests reached by now form a sufficient basis for the next step, i.e., development and testing of the system. The electromagnetic suspension technology is first applied with the long-stator propulsion. Belonging to a tracked transportation system, Maglev vehicles are extremely well adapted for automatic operation. The synchronous long-stator propulsion with active windings in the guideway and fixed frequency/speed ratio also meets all requirements for automatic operation. Modulation of speed and thrust is done by stationary frequency changers. Close contacts are maintained with several states that are also working on the development of new long-distance transport systems. As a result of the development two applications appear to be possible: the magnetic suspension ground transport system as a superimposed long-distance transport system, and the magnetic suspension ground transport system as a solution to specific transport tasks in the medium-distance range. The technical problems to be overcome prior to the introduction of the magnetic suspension ground transport system are clear today. After termination of the system tests, the operating tests, and the studies performed in parallel, the decisions which will then be necessary can be made on a firm basis.
TL;DR: The key software developed for the SCAN is a vehicle detection and tracking algorithm which reduces the TV image data to vehicle descriptions and trajectories which can be easily reduced to a wide range of traffic parameters.
Abstract: The sensor for control of arterials and networks (SCAN) uses imaging technology and processing technology to jointly provide real-time quantification. The SCAN concept consists of a television camera mounted on a pole to obtain images of the traffic, and a microprocessor to process the image data into traffic parameters. The current activities focus on the development of SCAN for surveillance of arterials or urban highways. If these efforts are successful, an attempt will be made to extend the concept to network applications. The key software developed for the SCAN is a vehicle detection and tracking algorithm which reduces the TV image data to vehicle descriptions and trajectories. These preprocessed trajectory data can be transmitted over a phone line or can be easily reduced to a wide range of traffic parameters. A SCAN breadboard has been implemented and installed in a van which enables remote field tests and evaluations. The SCAN breadboard and its operation, evaluation, and potential applications are described.
TL;DR: In this paper, a multistation simulcast digital radio paging system is considered, where each base station transmits the same RF signal simultaneously with the resulting efficient frequency utilization and simplified receiver design.
Abstract: In a multistation simulcast digital radio paging system, each base station transmits the same RF signal simultaneously with the resulting efficient frequency utilization and simplified receiver design. In this system a paging receiver in the overlapping area receives several RF signals transmitted from different base stations. When frequency-shift keying (FSK) is used as a modulation method, experimental test results have already shown that the timing of each RF signal should be synchronized as closely as possible, but that the carrier frequency of each transmitter should be set following a certain offset assignment. The signal transmission performance in a multipath fading environment can then be markedly improved. The cause of this improvement effect is theoretically analyzed. It is clarified that the improvement effect is caused by transforming the probability distribution of time-averaged signal power.
TL;DR: It is shown that the predicted performances of the levitation magnets, LIM, and the power collector system have been satisfactorily established, and that there would be no major technical problems in the course of the future development for implementation of the HSST system toward commercial services.
Abstract: HSST is an acronym for high-speed surface transport and is the trade name of the vehicle levitated by the attractive electromagnets and propelled by the linear induction motor (LIM) developed by Japan Air Lines. Two test vehicles have been designed, manufactured, and flight-tested. The first test vehicle, HSST-01, marked a maximum speed of 307.8 km/h on a 1300-m long test track in February, 1978, whereas the second test vehicle, HSST-02, has demonstrated boarding test flights successfully to an aggregated total of abut 1500 passengers since April, 1978, onward. The HSST-01 weighs one ton, is 4 m long, designed for high-speed testing, and incorporates eight electromagnets and a LIM with a maximum thrust of 300 kg. The levitating power supply is taken from the batteries carried on board the vehicle, and the three-phase VVVF power for the LIM propulsion is supplied from the wayside power lines through the power collector. The nine-seated HSST-02 has a loaded weight of 2.3 tons. Major items of additional functions realized in the HSST-02 include: 1) the electromagnets are fitted to the flexible chassis for better riding comfort by incorporating mechanical suspension between the chassis and the body, and 2) with the continuous levitation, the power for the LIM is rectified and supplied to the electromagnets jointly serving with the batteries carried on board. In light of the test results obtained so far, it is shown that the predicted performances of the levitation magnets, LIM, and the power collector system have been satisfactorily established, and that there would be no major technical problems in the course of our future development for implementation of the HSST system toward commercial services. The design of a preoperational test vehicle is now underway, and its test flight is scheduled to he initiated in 1980. This 80-seated preoperational test vehicle will have test flights on a 15-km test tract at a target crusing speed of 300 km/h.
TL;DR: An overview of the Mag-Transit concept from a control system standpoint, results from a dynamic simulation of a test vehicle configuration, and a potential for a substantial increase in system reliability and availability are provided.
Abstract: Mag-Transit is a unique combination of magnetic levitation and propulsion for people mover applications. Linear induction motors are used for levitation, propulsion, braking, and guidance. Since there are a minimum of moving parts there is a potential for a substantial increase in system reliability and availability as compared to conventional systems. Modern solid-state technology provides the capability to condition sufficient quantities of electrical energy to control motor excitation, and thereby levitation, within a closed-loop servo system. Real time measurements of air gaps and vehicle accelerations are used to compute the desired levitation force. In addition, the solid-state electronics provides the ability to control independently the speed of the vehicle by a continuously variable excitation frequency to the motors. An overview is provided of the Mag-Transit concept from a control system standpoint. Results from a dynamic simulation of a test vehicle configuration are presented.
TL;DR: Here, a methodology to ascertain the severity of one especially critical accident, multivehicle collisions resulting from the emergency braking of a platoon of automatically controlled, closely spaced vehicles, is presented.
Abstract: Future automatic highway systems should operate at high capacities (≥3600 vehicles/lane/h) over a range of highway speeds (13-26.8 m/s). Under such conditions it would be impossible to eliminate accidents. Here, a methodology to ascertain the severity of one especially critical accident, multivehicle collisions resulting from the emergency braking of a platoon of automatically controlled, closely spaced vehicles, is presented. This includes the specification of a collision model, which was based on reported crash-testing results, the selection of an accident-severity measure, a consideration of a corresponding cost function, and a sensitivity analysis to determine those parameters which most heavily impinge on accident severity and/or cost. The utility of the methodology was demonstrated by applying it to three platoon-accident scenarios which would be especially relevant to automated highway operations, and a quantitiative measure of the effects of key parameters on accident severity is specified. Such results would be of considerable use to a system designer.
TL;DR: A simple mathematical model is used to predict co-channel and adjacent channel interference effects in land mobile radio, valid for flat urban terrain and yields insights into the properties of differing types of modulation.
Abstract: A simple mathematical model is used to predict co-channel and adjacent channel interference effects in land mobile radio, valid for flat urban terrain. Results obtained, although oversimplified compared with real-life mobile radio systems, yield insights into the properties of differing types of modulation.
TL;DR: Four advanced system concepts are critiqued: automatic vehicle identification, automatic vehicle monitoring, automatic route guidance, and the automatic highway.
Abstract: Four advanced system concepts are critiqued: automatic vehicle identification, automatic vehicle monitoring, automatic route guidance, and the automatic highway. Each concept is defined, its potential applications are delineated, an overview of the state of the relevant technology given (and shortcomings noted), and the prospects for future deployments are considered. In addition, an extensive reference list is included.
TL;DR: In this paper, a modulation signal is made by superimposing a specific wave on an ordinary rectangular digital wave, and two conditions necessary for obtaining a diversity effect equivalent to the maximal-ratio combining are mathematically derived.
Abstract: Many mobile radio communication systems require digital signaling simultaneously from multiple transmitters from the viewpoints of efficient frequency utilization and simplified receiver construction. A new modulation scheme intended to realize simulcast digital transmission is described. In this method, a modulation signal is made by superimposing a specific wave on an ordinary rectangular digital wave. The two conditions necessary for obtaining a diversity effect equivalent to the maximal-ratio combining are mathematically derived. The specific waves for the various transmitters may be sinusoidal waves having a frequency equal to the original bit rate, and phases which differ from one transmitter to another. In order to clarify the feasibility of this technique, experimental simulation tests have been performed in the 900-MHz band in a two-transmitter configuration. It is proved that this modulation scheme, in comparison with the carrier-frequency offset strategy, not only gives the same amount of improvement in digital signaling in an overlapped area, but also makes the allowable carrier frequency drift more than ten times larger.
TL;DR: Automatic vehicle monitoring (AVM) is an electronic means of gathering data and effecting command and control over a land vehicle fleet as discussed by the authors, which is totally dependent upon refiable dedicated communications systems.
Abstract: Automatic vehicle monitoring (AVM) is an electronic means of gathering data and effecting command and control over a land vehicle fleet. While data on vehicle location are required for effective control, such systems are totally dependent upon refiable dedicated communications systems. By presenting a dispatcher or computer with information on each vehicle's location, decisions concerning the fleet's dispersion and operational readiness can be made. The Department of Transportation's Urban Mass Transportation Administration (UMTA) is developing such a system which will be evaluated in actual transit operations and offers potential application in traffic control operations.
TL;DR: The general conclusion drawn is that HAR can be, and has repeatedly proven to have been, a useful tool for traffic management and control.
Abstract: In 1977, two years after its initial Notice of Proposed Rule Making in Docket 20509, the Federal Communications Commission (FCC) authorized the establishment of travelers' information stations (TIS) in the Local Government Radio Service, Part 90 of the FCC Rules and Regulations. Stations may he authorized on either 530 kHz or 1610 kHz for the purpose of providing useful noncommercial information to the traveling public by agencies of state and local governments via the AM radios with which most motor vehicles are currently equipped. Agencies of the federal government, such as the U.S. Park Service, have also been authorized by the Interagency Radio Advisory Committee (IRAC) to operate travelers information stations subject to the same rules adopted by the FCC. The background of highway advisory radio (HAR) and some of the considerations that led to the present rules are discussed. The effect on HAR system design of limitations imposed by the rules and by AM receiver characteristics is also discussed. Using field data acquired under a Federal Highway Administration (FHWA) contract, the problems of HAR antenna design within the FCC imposed limits are illustrated. Finally, the FCC "Part 15" alternative to the design of HAR systems is discussed. Conclusions are stated. The general conclusion drawn is that HAR can be, and has repeatedly proven to have been, a useful tool for traffic management and control.
TL;DR: The main purpose is to report recent testing of automatic vehicle identification (AVI) systems and consider some probable early applications.
Abstract: To identify a vehicle uniquely and automatically as it passes on the roadway without requiring any action by the driver, one general approach uses a transponder on the vehicle and an interrogator by the roadside. When the identity is passed from the interrogator to a data system which may have data storage, retrieval, computation, display, and actuation capabilities, various functions such as charging for the use of road or parking facilities, fleet management, and fine grain traffic control become possible. The main purpose is to report recent testing of such systems and consider some probable early applications. At the outset, however, the functional requirements are discussed in more detail, and the background of automatic vehicle identification (AVI) development and testing is briefly reviewed.
TL;DR: In this paper, a magnetically levitated linear-motor propelled test vehicle is described, and a longitudinal control system with programmed limits on the second and third derivatives of the position command allows both precise position stopping and control of acceleration and jerk.
Abstract: The power conditioning for a magnetically levitated linear-motor propelled test vehicle is described. Control circuits have been developed to provide a constant air gap for levitation and improved damping of lateral motion due to force disturbances. Transistorized magnet drivers supply the required magnet current. A longitudinal control system with programmed limits on the second and third derivatives of the position command allows both precise position stopping and control of acceleration and jerk. A programmable controller is used for sequencing and monitoring the levitation and propulsion systems.
TL;DR: A basic land mobile satellite system (LMSS) is described, example applications are provided, and the status and rationale for LMSS frequencies in the 806-890 MHz band are given.
Abstract: The land mobile market is reviewed briefly, and services that might be provided by hybrid terrestrial/land mobile satellite systems (T/LMSS) are discussed. In view of the expected urban/ suburban patterns of planned terrestrial systems it is suggested that a satellite may prove a cost-effective complement to terrestrial systems for serving thinly populated or large geographical areas. A basic land mobile satellite system (LMSS) is described, example applications are provided, and the status and rationale for LMSS frequencies in the 806-890 MHz band are given. Next, examples are given of NASA supported land mobile satellite experiments, and a preliminary T/LMSS work plan, part of an overall narrowband (NB) program, is presented for structuring future work. The initiation of the T/LMSS plan depends on pending management/budget decisions. In conclusion a listing of issues and potential problem areas are given, the solutions of which NASA believes are critical to the success of the proposed T/LMSS effort.
TL;DR: In mobile communications such as automobile telephone systems, an instantaneous interruption is caused by rapid fading, and speech quality is markedly deteriorated, and a pitch-synchronized interpolation method is proposed to improve this quality.
Abstract: In mobile communications such as automobile telephone systems, an instantaneous interruption is caused by rapid fading, and speech quality is markedly deteriorated. A pitch-synchronized interpolation method is proposed to improve this quality. This method utilizes the fact that most speech signal regions have a pitch period. In this method, when an instantaneous interruption is detected at the receiver, a speech signal, which includes instantaneous interruption noise, is deleted and interpolated by repetition of the speech signal received one pitch interval wave before the instantaneous interruption. This method can be applied to receivers used in analog and digital transmission systems. A receiver using this method has been constructed, and it was shown that a 10-dB carrier-to-noise ratio (CNR) gain can be obtained by this receiver.
TL;DR: In this article, the ignition noise from the ignition systems of more than 11,000 individual vehicles in service in the United States in mid-1977 was measured at 50 and 153 MHz.
Abstract: Electromagnetic noise from the ignition systems of more than 11000 individual vehicles in service in the United States in mid- 1977 was measured at 50 and 153 MHz. Very little difference was found between the noise of U.S. domestic and foreign vehicles. Older vehicle groups are noisier than new vehicle groups, a fact which may be accounted for by either of two causes: a) some vehicles in a group become noiser with age, b) newer vehicles may have improved noise suppression systems. Measurements made in a single year will not show which effect predominates. We found the greatest noise differences between vehicle types (cars, trucks, and so on).
TL;DR: In this paper, four leading theories of linear induction motors (LIM's) are applied to the analysis of test data on the linear induction motor research vehicle, and computer models are exercised to demonstrate the operating regions over which the different finite size effects become significant.
Abstract: Four leading theories of linear induction motors (LIM's) are applied to the analysis of test data on the linear induction motor research vehicle (LIMRV). Computer models are exercised to demonstrate the operating regions over which the different finite size effects become significant. Each model is seen to yield a reasonable description of LIM performance within the limitations imposed by the model boundary assumptions. Variations in the predicted LIM normal force and input phase impedance are traced to different treatments of the finite size effects. Flux studies conducted on the LIMRV in the single-sided configuration demonstrate the presence of large phase belt modulation under static conditions.