Showing papers in "IEEE Transactions on Vehicular Technology in 1983"

Switched diversity with feedback for DPSK mobile radio systems

Abstract: Switched diversity with feedback for differential phase shift keying (DPSK) mobile radio is discussed. The technique uses multiple transmit antennas at the base station but only one receive antenna at the mobile. The base station transmits with one antenna that is switched when the mobile informs the base station that the received signal has fallen below a fixed level. The implementation of switched diversity with feedback in a digital mobile radio system is first described, and then the bit error rate performance of the system is analyzed with fading as a function of several design parameters. Implementation of the system is shown to be relatively simple, yet the system is shown to reduce substantially the required received E b /N 0 for a given error rate at the mobile as compared to a system without diversity. For example, with five transmit antennas the required received E b /N 0 for a 10-3bit error rate is 13 dB less. The system capacity and availability assuming 32 kb/s audio and flat fading is then discussed. It is shown that with three-corner base station diversity and four transmit antennas at each base station, 126 two-way circuits per cell can be used in a fully loaded 40-MHz bandwidth system with a ten-percent probability that the error rate exceeds 10-3.

Propulsion system

Abstract: Summary form only given. The propulsion system of low-voltage dc (-600 V) transit cars is complicated by the continual breaking of heavy dc currents in the typical multistep motor controller. Semiconductor controllers have two difficulties: they are vulnerable to high voltage impulses, and they require the ministrations of electronic technicians who may be hard to attract to the railroad industry. The author suggests an arrangement using two old and well-proven devices to control the flow of power to the traction motors. One is the venerable synchronous converter running inverted, that is, converting dc to polyphase ac, for example, 12 phase ac. The second device is the polyphase variable autotransformer, receiving its power from the converter and driving separately excited dc traction motors through diodes. Coasting is effected by simply backing off the variable autotransformer.

The timing of EV recharging and its effect on utilities

Abstract: Electric vehicles (EV's) represent an important future load on the electric utility system which, if properly managed, could increase power plant utilization and reduce the average cost of generating electricity. A future EV population of 7.5 million is addressed, together with its characteristics, vehicle use, consequent recharging loads, and the impact of EV's on electric utilities in terms of the generation of electric power, fuel use, and costs. The impact on utilities will depend in part on when the vehicles are recharged. If the price of electricity is uniform throughout the day, recharging is likely to begin when vehicles are parked at home. Most of the recharging would then occur during late afternoon and early evening hours when other demands for electricity are high. In the year 2000, peak electricity demand would increase by 5700 MW, and oil- and gas-fired power plants would generate 39 percent of the recharge power. Marginal generating costs would average 7.6 cents/kWh in 1982 dollars. If electricity were priced by time of day, recharging could shift to late night hours when the other demands for electricity are low. The peak demand would increase by only 400 MW; 27 percent of the power would come from oil and gas, and marginal generating costs would average only 5.1 cents/kWh, some 25 percent less than the marginal cost of the system load without EV's. The fuels to recharge EV's were found to vary from one region of the country to the next. Utilities in the northeast would use the most oil and gas for recharging (more than 75 percent), while those in the central part of the country would use the least.

Optimal channel reuse in cellular land mobile radio systems

Abstract: Origination probability for cochannel interference is introduced to the study of the influence of all cochannel interferers surrounding the base station of interest. In addition, the probability of cochannel interference, which is of importance in determining system parameters in a cellular communication scheme, is evaluated for the mobile radio environment as expressed by Rayleigh fading and shadowing. As a consequence, the optimal number of radio channels to allocate to each cell is derived through the use of a simple mathematical model. The theoretical results obtained are useful not only as a step in the maturation of the cellular land mobile radio system, but also for the development of the portable radio telephone system.

Spread spectrum mobile radio, 1977-1982

Abstract: In 1977, Cooper and Nettleton proposed a spread spectrum mobile radio system using frequency-hopping multiple access, Hadamard coding for error correction, and differential phase shift keyed (DPSK) modulation, and they claimed higher spectral efficiency than frequency-division (FD) FM systems. Subsequent analyses showed that the DPSK system has a spectral efficiency of 8.4 percent as compared to the efficiency of unity for a FD-FM system with 30-kHz channel spacings. Goodman et al. suggested an alternative modulation scheme in 1980, using multilevel frequency shift keying (MFSK), and a 30 percent efficiency was obtained. The research results in spread spectrum mobile radio are summarized, and the areas requiring further investigation before a commercial system can be implemented are identified.

Intercept point and undesired responses

Abstract: A method for using the concept of intercept point to calculate the undesired-response rejection ratio of a single stage is presented. Single stages may be cascaded together to form a system and the undesired-response rejection ratio of the system may be found using a procedure similar to cascaded noise figure. When applied to receiver system design, this method allows easy calculation of such undesired receiver responses as intermodulation distortion and spurious responses.

Theoretical and experimental investigation of feedforward signal regeneration as a means of combating multipath propagation effects in pilot-based SSB mobile radio systems

Abstract: A technique is described, feedforward signal regeneration (FFSR), to combat the effects of multipath propagation on VHF and UHF pilot tone single sideband (SSB) mobile radio systems. Unlike feedforward automatic gain control (FFAGC), FFSR suppresses both the random amplitude and phase fluctuations in the received signal. Extensive laboratory and field tests have shown that the operation of SSB at UHF frequencies is a viable proposition for both speech and data communication.

Quality of service and bandwidth efficiency of cellular mobile radio with variable bit-rate speech transmission

Abstract: The performance of an adjustable source/channel codec in a cellular mobile-radio environment is investigated. The speech transmission rate and the amount of forward error correction change in response to changing channel conditions. The channel rate is constant at 32 kb/s, and when the channel is good all of these bits are used for speech transmission. In intermediate and poor channels the speech rate is 24 or 16 kb/s, and the remaining channel symbols are used for forward error correction. Relative to conventional transmission this approach offers an improved grade of service. For example, the outage rate (the proportion of "poor or worse" communications) goes from nine percent with fixed-rate to three percent with variable-rate transmission. Alternatively, this improved grade of service can be exchanged for higher bandwidth efficiency. The fixed-rate system (with nine percent outage) has 23 users per cell. With 52 users per cell the outage of the variable-rate system is only six percent.

Development history of the hybrid test vehicle

Abstract: The development of the hybrid test vehicle (HTV) is described from its conception during Phase I of the DOE/JPL Near-Term Hybrid Vehicle Program through the design, fabrication, and delivery of the final HTV to the Jet Propulsion Laboratory (JPL) for evaluation and testing. Important design and test experiences gained in the development program leading to the final HTV are highlighted and described. The various mule vehicles leading to the final design are discussed. The HTV is described including computer projections of final performance.

Zinc-bromine battery design for electric vehicles

Abstract: Design projections for zinc-bromine batteries are attractive for electric vehicle applications in terms of low manufacturing costs ($28/kWh) and good performance characteristics. Zinc-bromine battery projections (60-80 Wh/kg, 130-200 W/kg) compare favorably to both current lead acid batteries and proposed advanced battery candidates. The performance of recently developed battery components with 1200 cm2electrodes in a 120V, 10 kWh module is described. Similarly constructed smaller scale (600 cm2) components have shown lifetimes exceeding 400 cycles and the ability to follow both regenerative braking (J227aD) and random cycling regimes. Initial dynamometer evaluations of full scale 20 kWh batteries is expected in early 1984.

The application of acoustic ranging to the automatic control of a ground vehicle

Abstract: The use of acoustics is proposed as an alternative method to determine the position of a vehicle relative to the road or to other vehicles Acoustic transducers mounted on the vehicle would range to passive targets along the side of the road or to other vehicles The simplicity of the system indicates that it could offer potential advantages in cost savings Factors which affect the accuracy of the system are discussed Theoretical and experimental analysis is presented to determine the extent to which these factors influence the accuracy of the system Based on these results, acoustic ranging represents a feasible method for use in the automatic control of a ground vehicle

Time division adaptive retransmission for reducing signal impairments in portable radiotelephones

Abstract: Multiple-antenna receiving diversity was shown previously to be effective in mitigating the effects of random angular orientation and multipath radio propagation for portable radiotelephones. It is shown that time-division adaptive retransmission used with appropriate antenna configurations can also mitigate these effects. The retransmission configurations require fewer antennas than the receiving diversity configurations for a given improvement in relative signal-to-noise ratio (S/N). Cumulative distributions of S/N were determined for adaptive retransmission and diversity using random orientation and multipath propagation models. Distributions of S/N for systems with two antennas at the portable set and two appropriately polarized antennas at the portable radiotelephone terminal (PORT) are similar to distributions for two-branch selection diversity in the fixed-orientation mobile radio environment. Systems with one portable antenna and two PORT antennas have distributions with slopes similiar to two-branch mobile radio distributions but the distributions for the portables range from 3 to 7 dB worse.

Electric vehicle field test experience

Abstract: Thirty-five experimental GMC electric vans accumulated over 300 000 miles in a field test application as telephone service and repair vehicles. Information was obtained on recharging lead-acid traction batteries which led to microprocessor control of the recharge. Energy consumption, ac kilowatt hours per mile, was greatly reduced and recharge efficiency increased by accurate control of the recharge. Battery energy density (range) and wear-out remain concerns which promote the need for a new energy source for commercial electric vehicles.

Propagation measurements for UHF spread spectrum mobile communications

Abstract: The U.S. Army is currently developing a number of spread spectrum radio systems to support its needs for more survivable and efficient mobile UHF data distribution on the tactical battlefield of the 1990's and beyond. The analysis and prediction of the performance of these systems in mobile tactical environments has been met with a great deal of uncertainty relating to the applicability of narrow-band propagation models and the effects of terrain irregularity and vegetation on broad-band signals. An overview is presented of an ongoing Army program utilizing wide-band pulse response measurements to characterize ground mobile tactical UHF spread spectrum propagation channels. Recently acquired experimental data are used to demonstrate the potential of this program for improving available tools for prediction and analysis of tactical UHF spread spectrum systems employing bandwidths of hundreds of MHz.

Electrical environmental characteristics for automotive electric systems

Abstract: The electrical environment is one of the most important factors in the design of high reliability electronic systems mounted on automobiles. Studies were made of the generation mechanisms and characteristics of both transients and high-frequency conducted noise generated in automotive electrical components. The high-frequency conducted noise data were obtained in terms of amplitude-frequency through real-time statistical treatment of the acquired data. The most important transient for automotive electronic systems has been found to be the alternator load dump transient caused by battery disconnection, and the most influential high-frequency conducted noise is caused by contact breaking. The high-frequency conducted noise characteristics can be expressed in the amplitude-frequency relation in the frequency range of 100 kHz-80 MHz.

Adjacent cell interference in FH-MFSK cellular mobile radio system

Abstract: The effect of adjacent cell interference in cellular mobile system using FH-MFSK transmission is evaluated quantitatively. The performance of base to mobile communication in the system is analyzed, assuming perfect synchronization between users in all the cells. Analysis of the system employing no power control shows that the number of simultaneous users possible at average bit error probability P b of less than 1 × 10-3is reduced greatly from the corresponding figure for the isolated cell (which is about 170). It is then shown that a simple power control strategy could reduce the adjacent cell interference significantly. A reasonable knowledge of the distribution of users within a cell allows the optimization of the receiver threshold with respect to distance from the base. With this optimization, each cell could accomodate ≳ 115 users at P b < 10-3, the exact figure being dependent on the user distribution. The power control also helps to reduce the average power transmitted from a base.

An experimental investigation of the active-idle pattern of speech over land mobile radio telephone channels

Abstract: Two methods of speech detection at the syllabic level of voice traffic over land mobile radio telephone channels are presented. Both methods are based on the periodic comparison of the audio signal level with a threshold and provide an ON-OFF pattern of active-idle periods on the channel at a rate equal to 100 to 200 samples per second. One method is entirely digital whereas the other method uses an analog detector followed by digital processing. Results of the analysis show that during a conversation more than 50 percent of the time the channel is idle, with an average duration of the silences larger than 300 ms. These results and those concerning other parameters of interest indicate that even during a conversation many useful idle periods do occur. These silences could indeed be exploited by making them available to additional users and hence improve both the efficiency of the channels and their congestion.

Design and performance evaluation of a packet voice system

Abstract: A packet voice network has been designed using adaptive delta modulators. Tests were performed to examine the effects of packet length and packet loss rate on digital voice intelligibility. The packet voice network was simulated using a SLAM network model to find queue size requirements as a function of packet size, delay distribution, and expiring time out. The queuing strategy is investigated in order to minimize total information loss during channel acquisition delays.

Fuel cell power plants for automotive applications

Abstract: The SPE®fuel cell has been under continuous development since the mid-fifties. For the most part the applications have been of a specialty type such as for space vehicle electrical power, remote or mobile ground power, and undersea systems. The common denominator of these specialty power plant applications is that each is obliged to pay a premium for electric power generation. As a result the SPE fuel cell has been economically competitive in the specialty powerplant market. Until recently the SPE fuel cell has not been considered economically viable in the industrial/commercial markets in competition with gas turbine generators or internal combustion engines. However, in the last few years the electrical current density capability of the SPE fuel cell has markedly increased which has the impact of reducing capital costs on the basis of the kW output rating. During 1981, a study was conducted for the Los Alamos National Laboratory (LANL) to determine the feasibility of using this SPE fuel cell technology for vehicular propulsion. The results show that with adequate development, a power plant is possible which will meet the performance, size, and weight objectives, and that the costs for such a system could be competitive with other potential advanced power systems.

A computer simulation model for the evaluation of mobile radio systems in the military tactical environment

Abstract: A computer simulation model, designed specifically for the analysis and evaluation of military mobile radio communication systems in the tactical environment is discussed. The algorithms and performance models used in the simulation model are briefly described, while statistical characteristics are derived analytically for a simplified scenario. Typical computer-generated histograms and distribution functions are presented for the more complex scenarios. The computer simulation model is shown to be an effective design tool for many different applications.

RF Conducted noise measurements of automotive electrical and electronic devices using artificial network

Abstract: Two RF conducted noise measurement systems have been developed for laboratory measurements of automotive electrical and electronic devices. One is a noise emission measurement system for measuring noise level from the electrical devices while the other is a susceptibility measurement system for measuring the susceptibility level of the electronic devices to the noise. The former's function is to measure a histogram of noise level, and the latter functions both to measure the malfunction level and to judge a malfunction mode of the electronic devices. These measurement systems are applicable to the frequency of 150 kHz-60 MHz. These are for laboratory measurements performed with the measurement systems connected to an artificial network of the automotive electrical network. This artificial network represents electrical networks used on Japanese compact passenger vehicles.

The lead-acid battery&#8212;Demonstrating the systems design approach to a practical electric vehicle power source

Abstract: Resurgent interest in electric vehicles has resulted in extensive research and development programs, including government support, to develop a lead-acid battery system which can deliver acceptable range and cycle life. In the last decade, significant gains in energy density, power density, and cycle life have been made. The Improved State of the Art (ISOA) Electric Vehicle (EV) battery developed by the Globe Battery Division of Johnson Controls, Inc., utilizes the leading edge technology responsible for these improvements. The patented electrolyte circulation system is the cornerstone of this design. Emphasis was placed on a systems design approach which included priority consideration for safety and ease of maintenance. Efforts toward achieving the ambitious "Advanced Battery" goals are progressing. Rival exotic energy storage systems require considerable additional development before they might become practical alternatives. The major advantages of the lead-acid system firmly position it as the most practical energy source for electric vehicles, both now and in the near future.

Digital signal processing spectrum inversion for analog speech channels

Abstract: Speech security communication systems applied to radio analog speech channels become more and more desirable as radio channel capacity increases and service area spreads. Analog spectrum inversion used in existing radio communication systems is suitable for preventing eavesdropping and ensuring security, but it suffers from inevitable speech quality degradations. It is shown that digital spectrum inversion can be accomplished merely by alternating the sign of the sampled data to avoid distortion. Digital inversion is theoretically deduced by the discrete Fourier transform and verified by experiments. The aperture effect is also discussed from the viewpoint of spectrum inversion. Digital spectrum inversion is implemented with exclusive OR gates and a one digit binary counter, which is easily integrated onto a large scale integration (LSI) chip to avoid element value deviation. Signal-to-noise ratio (SNR) and distortion are observed to be more than 50 dB and -50 dB right across the 0.3-3.7 kHz frequency band, when an 8 kHz sampling rate is adopted for digital processing.

Summary of electric vehicle energy source technologies

Abstract: The many requirements that electric vehicles impose on energy sources are presented. The capabilities and potential problem areas of various electrochemical energy sources being considered for vehicle propulsion are reviewed, and their state of technology development is compared to expected vehicular performance requirements.

The role of computer modeling and simulation in electric and hybrid vehicle research and development

Abstract: Computer modeling and simulation is widely used in support of electric and hybrid vehicle research and development. Many modeling-assisted studies and assessments, involving candidate technology comparisons, have been performed to provide information for management planning and research decisions. Modeling has also been extensively used in engineering activities including preliminary and final design optimization. A wide range of programs has been developed including small ones for use on hand-held programmable calculators and large programs involving more than 11 000 lines. Many programs exist in the public domain, and two major programs are available on commercial time-sharing systems.

Advanced vehicle system concepts

Abstract: Various nonpetroleum vehicle system concepts for passenger vehicles in the 1990's are being considered as part of the Advanced Vehicle (AV) Assessment at the Jet Propulsion Laboratory. The vehicle system and subsystem performance requirements, the projected characteristics of mature subsystem candidates, and promising systems are presented. The system candidates include electric and hybrid vehicles powered by electricity with or without a nonpetroleum power source. The subsystem candidates include batteries (aqueous-mobile, flow, high-temperature, and metal-air), fuel cells (phosphoric acid, advanced acids, and solid polymer electrolyte), nonpetroleum heat engines, advanced dc and ac propulsion components, power-peaking devices, and transmissions.

A summary of EHV propulsion technology

Abstract: The quest for a commercially successful electric vehicle invariably centers around three major factors which influence buyer decisions: performance, range, and cost. Using today's technology, two items within an electric vehicle have the greatest influence on these factors. The battery is the primary determinant of range and to a lesser extent of performance. The design of the propulsion system sets the performance level of the vehicle and has a smaller effect on range. While the battery has the greatest impact on the life cycle cost of a vehicle, the propulsion system is a much larger contributor to the purchase price. Propulsion subsystem weight, efficiency, and cost are related to the specified combination of components used. Under the United States Department of Energy's Electric and Hybrid Vehicle Program, propulsion component and system advancements have been made which will result in weight savings of 35-50 percent, efficiency gains of 25 percentage points, and significantly lower cost when compared to the state of the art at the inception of the program.

Low loss and high performance SAW filters for 800 MHz mobile telephone transceiver

Abstract: Low loss surface acoustic wave (SAW) filters have been developed for use in the radio frequency circuits of the mobile telephone transceiver. Both the UHF (800 MHz) and VHF (90 MHz) band-pass filters have exhibited high performance, and the employment of the SAW filters has shown advantages in UHF/VHF circuit integration for mass production.

EHV systems technology&#8212;A look at the principles and current status

Abstract: Systems analysis provides a crucial focal point which binds together the various component and subsystem technologies in electric and hybrid vehicle (EHV) development. Basic principles and practices involved in system engineering are examined in order to define this sometimes nebulous concept better. Recent electric vehicle (EV) system developments are reviewed with some emphasis on their fundamental limitations. Hybrid-electric vehicles (HV's) are introduced as an alternative which overcomes many of these limitations. A hybrid concept assessment methodology is presented which utilizes the state of the technology and yet satisfies Department of Energy (DOE) petroleum displacement goals.

A mobile interference model into UHF television reveivers

Abstract: A mathematical model to compute the duration of interference into a TV receiver from a land mobile transmitter in the busy hour is proposed. The objective is to determine how various parameters such as mobile density, traffic density, and distance will affect the probability that a transmitting mobile will degrade the picture quality of a TV receiver.