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Vehicular Technology, IEEE Transactions on

Issue 1 • Date Feb 1992

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Displaying Results 1 - 10 of 10
  • Performance of optimum transmitter power control in cellular radio systems

    Publication Year: 1992 , Page(s): 57 - 62
    Cited by:  Papers (490)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    Most cellular radio systems provide for the use of transmitter power control to reduce cochannel interference for a given channel allocation. Efficient interference management aims at achieving acceptable carrier-to-interference ratios in all active communication links in the system. Such schemes for the control of cochannel interference are investigated. The effect of adjacent channel interference is neglected. As a performance measure, the interference (outage) probability is used, i.e., the probability that a randomly chosen link is subject to excessive interference. In order to derive upper performance bounds for transmitter power control schemes, algorithms that are optimum in the sense that the interference probability is minimized are suggested. Numerical results indicate that these upper bounds exceed the performance of conventional systems by an order of magnitude regarding interference suppression and by a factor of 3 to 4 regarding the system capacity. The structure of the optimum algorithm shows that efficient power control and dynamic channel assignment algorithms are closely related View full abstract»

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  • Performance evaluation of the R-BTMA protocol in a distributed mobile radio network context

    Publication Year: 1992 , Page(s): 24 - 34
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    A reservation multiple-access protocol for mobile communication in a decentralized environment is proposed and investigated both analytically and by simulation. The reservation-busy-tone multiple access (R-BTMA) is a fully distributed and reservation-based protocol. It is a medium access control (MAC) protocol designed for short-range communications between vehicles in a decentralized context (i.e., without a base station). The specificity of this protocol relies on the utilization of two different characteristic channels. Information is transmitted on the data channel (DC), whereas the busy-tone channel (BTC) is used for signalling traffic. The range of the BTC is typically longer than the DC one. The throughput and access delay performance are studied in the particular context of two cells sharing a common BTC. The traffic between the vehicles is supposed to be regular and is parameter sharing. The comparison of the model analysis results to those obtained by the simulative approach shows a satisfactory matching View full abstract»

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  • Nonredundant error correction analysis and evaluation of differentially detected π/4-shift DQPSK systems in a combined CCI and AWGN environment

    Publication Year: 1992 , Page(s): 35 - 48
    Cited by:  Papers (6)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    The application of the nonredundant error correction (NEC) technique to the North American and Japanese digital cellular modulation standard, π/4-shift differential quadrature phase shift keying (DQPSK), in a combined additive white Gaussian noise (AWGN) and cochannel interference (CCI) environment is proposed, analyzed, and theoretically evaluated. The performance for NEC receivers with single, double, and triple error correction capability is theoretically analyzed and evaluated. For the CCI, the general model, which includes M statistical independent interferers also employing the π/4-shift DQPSK modulation format, is adopted. The theoretical symbol error probability versus carrier-to-noise ratio have been obtained with M and the carrier-to-interference ratio (C/I) as parameters. The results indicate significant performance improvements over conventional differentially detected systems. Some of the results have been verified by computer simulation. The gains offered by the NEC receivers increase as C/I decreases and/or M increases. Significant error floor reductions have been observed View full abstract»

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  • An adaptive predistorter for a power amplifier based on adjacent channel emissions [mobile communications]

    Publication Year: 1992 , Page(s): 49 - 56
    Cited by:  Papers (76)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    A slowly adapting predistorter is presented. The approach is to minimize the transmitter output power in spectral regions occupied only by intermodulation (IM) products. In this way, only a spot power measurement is required. This technique relies on the principle that the power amplifier's characteristics vary slowly with time. By monitoring the out-of-band power one can obtain an estimate for the distortion introduced by the power amplifier. Adaptation is accomplished by iterative adjustment of the predistorter parameters to minimize the IM power. For a polynomial predistorter, the authors analytically demonstrate that the IM power is a quadratic function of the coefficients. A variety of algorithms therefore apply. The authors present an analog static predistortion linearization circuit that uses the envelope of the baseband signal to generate the nonlinear functional used in predistorting the input signal. The improvement obtained with an amplitude-modulated input signal was 15 dB in the third- and 5 dB in the fifth-order intermodulation products. The IM improvement could be maintained with the use of a robust direct search algorithm View full abstract»

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  • Vehicle position estimates by multibeam antennas in multipath environments

    Publication Year: 1992 , Page(s): 63 - 68
    Cited by:  Papers (41)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    Vehicle positions in multipath environments are estimated from the angle of arrival of waves received by multibeam antennas installed at two base stations. The estimated root mean square (RMS) position error is about 350 m. This can be reduced to about 200 m by using two kinds of processes: the averaging of time series data and the averaging of two sets of data. The position estimate error is caused by reflection from buildings near the vehicles, and a large error exceeding 500 m is caused by reflections from high buildings located some distance from the vehicle. Precise estimation of vehicle position in multipath environments by measuring angle-of-arrival is difficult because of building reflection View full abstract»

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  • Energy absorption mechanism by biological bodies in the near field of dipole antennas above 300 MHz

    Publication Year: 1992 , Page(s): 17 - 23
    Cited by:  Papers (79)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    The energy absorption mechanism in the close near field of dipole antennas is studied by numerical simulations. All computations are performed and validated applying the three-dimensional multiple multipole software package. The numerical model of the plane phantom is additionally checked by accurate as possible experimental measurements. For the plane phantom, the interaction mechanism can be described well by H-field induced surface currents. The spatial peak specific absorption rate can be approximated within 3 dB by a formula given here based on the incident H-field or antenna current and on the conductivity and permittivity of the tissue. These findings can be generalized to heterogeneous tissues and larger biological bodies of arbitrary shape for frequencies above 300 MHz. The specific absorption rate is mainly proportional to the square of the incident H-field, which implies that in the close near field, the spatial peak specific absorption rate is related to the antenna current and not to the input power View full abstract»

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  • Design of a tapered coaxial resonator filter for mobile communications

    Publication Year: 1992 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The authors describe the design, a simple fabrication technique, and performance of a coaxial resonator filter with tapered inner conductors to be used in mobile radios. The effects of coupling, window area, and temperature on the performance of the filter have also been considered. The passband of the filter is 30 MHz with a center frequency of 925 MHz, 1.15-dB insertion loss, 0.8-dB ripple, and 14.7-dB return loss at the center frequency. The resonant frequency and coupling coefficient stabilities with temperature have been measured at 28.38 ppm/°C and 3.5×10-4/°C, respectively. The 3-dB bandwidth is measured as 32 MHz and a sharp cutoff is observed at -16.5 dB with a bandwidth of 37 MHz for narrow scale and -65 dB with a bandwidth of 84 MHz for wide scale. The fabrication technique developed using a zinc-cast inner conductor and extruded aluminum outer conductor has better reproducibility than the conventional machining technique and is highly cost effective View full abstract»

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  • A simulation study of speech traffic capacity in digital cordless telecommunications systems

    Publication Year: 1992 , Page(s): 6 - 16
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    A computer simulation tool for evaluating the speech traffic handling capability of digital cordless telecommunications systems has been developed. The focus of the paper lies on the teletraffic engineering problems posed by time division multiple access (TDMA) systems operating with time division duplex (TDD) on one radio transceiver in radio environments. The impacts of fixed station separation, fixed station capacity, spatial traffic variability, dynamic channel assignment, microdiversity, and propagation model on the system capacity are investigated. The simulator serves as an invaluable tool for conducting sensitivity studies and its outputs provide useful insights on traffic performance of digital cordless systems View full abstract»

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  • Protocol configuration and verification of an adaptive error control scheme over analog cellular networks

    Publication Year: 1992 , Page(s): 69 - 76
    Cited by:  Papers (6)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    A high-speed and error-free voiceband data communication method using a hybrid automatic repeat request (ARQ) protocol over an analog cellular system is described. The present method adopts an adaptive error control scheme. This error control scheme automatically selects the optimal error correction code according to circuit bit error rate (BER), so as to match it to the frequently changing mobile radio propagation path conditions. This method adopts multiframe rejection as a retransmission scheme for a high throughput efficiency on the burst error circuit. Actual field evaluation was made by mounting this protocol on a CCITT V.22 bis modem with a data transmission speed of 2400 b/s and a modulation method using 16 carrier states over the Advanced Mobile Phone Service (AMPS) in Atlanta, GA, verifying that data communications can be achieved with an average throughput efficiency of 70% over a radio channel having a BER up to 10-2 View full abstract»

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  • Near-far effects in land mobile random access networks with narrow-band Rayleigh fading channels

    Publication Year: 1992 , Page(s): 77 - 90
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB)  

    The near-far effect of random access protocols in mobile radio channels with receiver capture is investigated. To this end, the probability of successful reception of a packet from a terminal at a known distance from the central receiver is obtained taking into account Rayleigh fading, UHF propagation attenuation, and the statistics of contending packet traffic in radio nets employing slotted ALOHA, carrier sense multiple access (CSMA) or inhibit sense multiple access (ISMA) protocols. Various models of receiver capture are compared, namely packet error rates for synchronous detection in slow- and fast-fading channels, and the probability that the signal-to-interference ratio is above a required threshold View full abstract»

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Aims & Scope

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

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Meet Our Editors

Editor-in-Chief
Yuguang Michael Fang
University of Florida