By Topic

Vehicular Technology, IEEE Transactions on

Issue 3 • Date Aug 1991

Filter Results

Displaying Results 1 - 15 of 15
  • Visual control of an autonomous vehicle (BART)-the vehicle-following problem

    Publication Year: 1991 , Page(s): 654 - 662
    Cited by:  Papers (25)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    The authors consider the problem of vehicle-following including automatic steering and speed control of an autonomous vehicle following the motion of a lead vehicle. A visual control system for vehicle-following is presented. The system consists of the following modules: image processing, recursive filtering, and a driving command generator. First, the range and heading signal of the lead vehicle are obtained by visually identifying a unique tracking feature on the lead vehicle. Based upon this information, appropriate steering wheel and speed commands for driving are generated, which are then downloaded and executed on a microprocessor controller. The visual control system was tested on BART (Binocular Autonomous Research Team), a testbed vehicle developed at Texas A&M University for autonomous mobility. Successful full-scale test runs have been accomplished for speeds up to 20 mi/h View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bit error rate performance of π/4-DQPSK in a frequency-selective fast Rayleigh fading channel

    Publication Year: 1991 , Page(s): 558 - 568
    Cited by:  Papers (49)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    The bit error rate (BER) performance of π/4-differential quadrature phase shift keying (DQPSK) modems in cellular mobile communication systems is derived and analyzed. The system is modeled as a frequency-selective fast Rayleigh fading channel corrupted by additive white Gaussian noise (AWGN) and co-channel interference (CCI). The probability density function of the phase difference between two consecutive symbols of M-ary differential phase shift keying (DPSK) signals is first derived. In M-ary DPSK systems, the information is completely contained in this phase difference. For π/4-DQPSK, the BER is derived in a closed form and calculated directly. Numerical results show that for the 24 kBd (48 kb/s) π/4-DQPSK operated at a carrier frequency of 850 MHz and C/I<20 dB, the BER will be dominated by CCI if the vehicular speed is below 100 mi/h. In this derivation, frequency-selective fading is modeled by two independent Rayleigh signal paths. Only one co-channel is assumed in this derivation. The results obtained are also shown to be valid for discriminator detection of M-ary DPSK signals View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of PRMA: a packet voice protocol for cellular systems

    Publication Year: 1991 , Page(s): 584 - 598
    Cited by:  Papers (252)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1208 KB)  

    Equilibrium point analysis is used to evaluate system behavior in a packet reservation multiple access (PRMA) protocol based network. The authors derive the probability of packet dropping given the number of simultaneous conversations. The authors establish conditions for system stability and efficiency. Numerical calculations based on the theory show close agreement with computer simulations. They also provide valuable guides to system design. Because PRMA is a statistical multiplexer, the channel becomes congested when too many terminals are active. For a particular example it is shown that speech activity detection permits 37 speech terminals to share a PRMA channel with 20 slots per frame, with a packet dropping probability of less than 1% View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fiber optic microcellular radio

    Publication Year: 1991 , Page(s): 599 - 606
    Cited by:  Papers (65)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A distributed antenna system consisting of optical fiber connected canisters is proposed to replace or supplement the base station antennas required for cell splitting of growing cellular mobile radio systems. The end-to-end linear transmission of RF signal voltage can be maintained over the wide dynamic range of mobile radio. The technical feasibility of multiplexed subcarrier transmission using available lightwave components has been verified by signal-to-noise ratio and intermodulation distortion measurements. Measurements of a two-way audio link over both simulated and real radio paths have demonstrated the compatibility of a prototype lightwave transceiver, designed for the canister, with the existing base station and mobile equipment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Facsimile transmission via HF radio

    Publication Year: 1991 , Page(s): 515 - 520
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The authors examine the feasibility of transmitting facsimile (FAX) over radio voice-channels using existing machines and existing radio installations. CCITT Groups 1, 2, and 3 FAX were tested on simulated high-frequency (HF) channels using the US government's HF simulator at Ft. Monmouth, NJ. Tests included both the premessage exchange and the message portion of the FAX transmission. Test results show that the FAX integral wire-line model used for Group 3 operation does not work well on realistic, long-haul, HF channels even at the minimum fallback rate of 2400 b/s. Group 2 FAX also fails for most of the cases simulated. Group 1 FAX produces documents on most simulated channels although the quality of the document degrades as the impairments become severe. The degraded documents, however, are usable in most cases View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of GMSK in a land mobile radio channel

    Publication Year: 1991 , Page(s): 607 - 614
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Discriminator detection of Gaussian minimum shift keying (GMSK) in a cellular mobile-communication channel is analyzed. The channel is modeled as a frequency-selective fast Rayleigh fading channel corrupted by additive white Gaussian noise (AWGN) and co-channel interference (CCI). A closed-form expression for the probability of error is derived. Numerical computation is used to obtain the GMSK bit error rate (BER) performance for various combinations of channel parameters. These results show that GMSK gives slightly better performance compared to that for π/4-quadrature phase shift keying (QPSK) previously reported in the literature View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive equalization and diversity combining for mobile radio using interpolated channel estimates

    Publication Year: 1991 , Page(s): 636 - 645
    Cited by:  Papers (50)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    The authors demonstrate the feasibility of a digital cellular radio (DCR) system which employs a jointly adaptive decision-feedback equalizer and diversity combiner. In particular, the authors utilize the current estimates of the channel impulse response (CIR) at each diversity branch to compute the receiver parameters periodically. The authors propose a novel block-adaptive strategy which computes the time-varying CIR by interpolating a set of CIR estimates obtained through periodic training. Although incurring some inherent processing delay and throughput reduction, this interpolation strategy has the advantage of immunity to decision errors which would quite likely occur during a deep fade. It is shown that the system performance is limited, in the form of an irreducible bit error rate at high signal-to-noise ratios (SNRs), by the CIR estimation of the rapidly fading channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The multiple-call hand-off problem in high-capacity cellular communications systems

    Publication Year: 1991 , Page(s): 546 - 557
    Cited by:  Papers (105)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1012 KB)  

    The author presents a preliminary analytical model that characterizes the central issues of the hand-off problem when vehicles can support multiple calls simultaneously. In such cases a cell boundary crossing by a single vehicle can generate multiple hand-off attempts. A suitable vector state representation is identified which casts the problem as a multidimensional birth-death process. An iterative method is used to find implicit hand-off parameters for systems in statistical equilibrium. Theoretical performance characteristics that show blocking, hand-off failure, and forced termination probabilities as functions of communication traffic are determined View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Autonomous adaptive frequency assignment for TDMA portable radio systems

    Publication Year: 1991 , Page(s): 627 - 635
    Cited by:  Papers (57)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    A simple autonomous procedure performed by each radio port (base station) to determine its own transmitting frequency is proposed. This procedure consists of signal strength measurements and an algorithm which selects the frequency with minimum interference from other ports. The algorithm converges rapidly while adapting to changes of operational conditions, such as installing new ports, which changes the system configuration, or adding new buildings, which causes different shadow fading. This method is significantly superior to a random assignment method both in resultant channel quality and in traffic-handling capability. For a regular-grid configuration, this method performs nearly as well as an a priori optimal frequency assignment method. It is also found that this assignment algorithm is robust against short-term signal fluctuations and it can be performed completely autonomously by each radio port View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-dimensional performance of an LMS adaptive array with inverted-F elements

    Publication Year: 1991 , Page(s): 575 - 583
    Cited by:  Papers (2)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The performance of an adaptive array with two inverted-F elements is analyzed by using the method of moments. A random signal model for mobile communication in a typical urban area is used. Three-dimensional analysis is applied to give a clear expression of the array output signal-to-interference plus noise ratio (SINR) performance. Also, a factor called SINR pattern angle ratio (PAR) is introduced with which a quantitative evaluation of the SINR patterns becomes possible. By using the PAR, the array performance for different array parameters such as inverted-F antenna (IFA) element orientations, interelement spacings and incident signal directions are computed. As a result, the IFA element is found preferable to a quarterwave monopole array in the assumed signal environment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Vehicular implementations of public key cryptographic techniques

    Publication Year: 1991 , Page(s): 646 - 653
    Cited by:  Papers (1)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    The author discusses public key cryptography techniques offering solutions to the unique problems associated with transaction authentication procedures using the open communication channel between a vehicle and an unprotected ground terminal. Valuable secrets embedded in costly security modules are not kept at the terminals. Playback of recorded taped communications or attempts at rehashing messages would be useless, and will not assist illicit falsification or forging of subsequent transactions. To prevent the unauthorized use of the crediting facility of a vehicle, an integral part of this facility is to be carried by the driver when the vehicle is not in operation. This can be integrated into existing electronic ignition keys. A public key cryptographic module installed in a vehicle can also be used for theft prevention by enhancing both ignition security and remote controlled door locking/unlocking mechanisms. The same device can be used for authenticating smartcard-based prepayment systems for parking or toll-road usage. This methodology is described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental evaluation of space/frequency/polarization diversity in the indoor wireless channel

    Publication Year: 1991 , Page(s): 569 - 574
    Cited by:  Papers (39)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A series of experiments that were conducted to evaluate the relative merits of frequency, space, and polarization diversities in indoor portable radio channels at 900 MHz are described. Unmodulated tones were used to probe the channel in a typical university work environment. The statistics of the signal envelopes were analyzed to determine the correlation of the field strengths when the signals are separated in space, frequency or polarization. According to the results presented here, the performance of a narrowband system (<200 kHz) at 900 MHz could greatly benefit from a frequency diversity scheme provided that the separation between the two frequencies is greater than approximately 5 MHz. Similarly, the advantage of space diversity is found significant when the two antennas are spaced by 3/4 wavelength or more. Co-polarized and cross-polarized signals are nearly uncorrelated and their relative field strengths differ by less than 2 dB in most locations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An adaptive filtering technique for pilot-aided transmission systems

    Publication Year: 1991 , Page(s): 532 - 545
    Cited by:  Papers (16)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    One of the main design tradeoffs of pilot-based techniques of combating the effects of multipath fading is the pilot filter bandwidth. The approach presented is to store a precalculated bank of pilot filters and automatically select the best one as the signal-to-noise, (SNR) or vehicle speed change. The authors address the issue of adjusting the filter bandwidth as speed changes. They call this technique the filter switching algorithm. This technique can provide a 1.0 dB improvement for a normalized Doppler frequency of 2%; up to 2.0 dB can be gained when operating at a lower Doppler frequency. The algorithm is found to be very robust, in the sense that self-noise and decision direction have little effect on its operation and the resulting bit error rate View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Symbol timing tracking for continuous phase modulation over fast flat-fading channels

    Publication Year: 1991 , Page(s): 615 - 626
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    The symbol timing tracking problem for a class of continuous phase modulation (CPM) schemes transmitted over unfaded and fast flat-fading channels is studied. The specific family of CPM considered is that of M-ary continuous-phase modulation with a modulation index of h=1/M. A particular symbol synchronizer structure that constructs a tone at the symbol frequency by passing the received signal through an Mth power law nonlinearity and multiband filter followed by a squared-envelope nonlinearity and narrowband filter is proposed. The operation and parameters of this symbol synchronizer are discussed as well as the performance of the synchronizer. Simulation results giving the root-mean-square timing jitter of this system for several binary, quaternary and 8-ary instances of modulation using rectangular, raised-cosine, truncated Nyquist III, and truncated tamed FM pulse shapes are presented to illustrate the synchronizer performance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Downlink outage predictions for cellular radio systems

    Publication Year: 1991 , Page(s): 521 - 531
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    A general model for predicting downlink outage due to co-channel interference in cellular radio systems is presented. The model accounts for path loss, log-normal shadowing, Rayleigh fading, and vehicle velocity. The outage predictions are obtained by computer simulation. Various outage control techniques are evaluated, including cell sectoring, transmitter control, and hands-off. It is shown that down link power control is quite useful when hand-offs are used, and that shadowing can have a large effect on the outage predictions. The outage predictions are applied to a digital cellular system that uses quadrature differential phase shift keying (QDPSK) modulation and Reed-Solomon (RS) coding. It is shown that the performance of a coded digital cellular system is largely limited by rapidly moving vehicles View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Vehicular Technology covers land, airborne, and maritime mobile services, vehicular electrotechnology, equipment, and systems identified with the automotive industry.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Yuguang Michael Fang
University of Florida