By Topic

Vehicular Technology Conference, 1998. VTC 98. 48th IEEE

Date 21-21 May 1998

Go

Filter Results

Displaying Results 1 - 25 of 195
  • 48th IEEE Vehicular Technology Conference [front matter]

    Page(s): i - xxxviii
    Save to Project icon | Request Permissions | PDF file iconPDF (2385 KB)  
    Freely Available from IEEE
  • Author index

    Page(s): xxxix - xliv
    Save to Project icon | Request Permissions | PDF file iconPDF (491 KB)  
    Freely Available from IEEE
  • Feature based recognition of traffic video streams for online route tracing

    Page(s): 1790 - 1794 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    An approach is presented for the acquisition of route related data by means of recognizing vehicles that pass different survey points. This recognition approach essentially relies on vehicle license plate matrices that are provided by standard video cameras. A recognition pipeline is conceived where the main steps are a frame selection method, a segmentation: technique for the localization of plate matrices, a feature extraction method and a recognition process. The single steps are discussed in detail and recognition rates that have been achieved in a field trial are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of frequency domain multiuser detector for synchronous CDMA communication over Rician fading channels

    Page(s): 1725 - 1729 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The performance of frequency domain multiuser detector (FD-MUD) proposed by Lops, Ricci, and Tulino (see IEEE ISSSTA '96, p.541-5, Mainz, Germany, 1996) is analyzed over a Rician fading channel. The bit error probabilities for FD-MUD with coherent detection and differentially coherent detection are derived. The results are compared with those of the decorrelating detector. Through numerical examples, it is shown that the FD-MUD has a lower bit error rate than the decorrelating detector over a Rician fading channel. It is also shown that the FD-MUD has a robustness to narrowband interference. In addition, the advantages of the FD-MUD over decorrelating detector in implementation of the detector are investigated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Equilibrium traffic assignment using recurrent backpropagation

    Page(s): 2575 - 2579 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The paper presents a discrete time equilibrium traffic assignment model for urban road networks. The equilibrium state can be chosen either user optimized (in the sense of Wardrop's first principle) or system optimized. The model is capable of taking into account various kinds of network characteristics and constraints like o-d-matrices, link capacities, traffic counts and known intersection splitting rates. Congestion phenomena are modeled by traffic dependent link speed and link inflow restrictions. The task is interpreted as a nonlinear dynamic system control problem and a special recurrent neural network, together with its associated error-propagation network, is used for both identification and control of the system. Flow splitting rates serve as control parameters which have to be adjusted according to the minimization of some objective function (comprising the sum of link travel times). The necessary gradient information can be computed very rapidly by means of a modified version of the recurrent backpropagation algorithm. Because of the use of neural-network-like-structures, the process should be suitable to get implemented on massively parallel hardware View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiuser detection using blockwise successive interference cancellation in DS/CDMA systems

    Page(s): 1835 - 1838 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The performance of a new multiuser detector in combination with a blockwise successive interference cancellation (BSIC) scheme for DS/CDMA systems is proposed. The BSIC detector consists of the multistage blocks, which include the power-ranked users to be cancelled. The BSIC scheme is simulated using coherent QPSK modulation under AWGN and Rayleigh fading environments. From the practical implementation point of view, a promising candidate among tile multiuser detectors is the SIC detector due to the lower complexity compared to other multiuser detectors. The SIC scheme. However, has two main problems. The first problem is that each user, once selected, makes no further contribution and refinement for subsequent operations. The second problem is that the hardware complexity of the SIC scheme grows linearly as the number of users increase. We compare the performance and the hardware complexity of the SIC scheme and the BSIC scheme. The experimental results show that as the size of block at the BSIC scheme increases, the performance of the BSIC scheme is improved, outperforming the SIC scheme. The BSIC scheme has low hardware complexity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of threshold setting rules for the mean acquisition times of a DS spread spectrum receiver in certain type of fading

    Page(s): 1735 - 1739 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    This paper describes the meaning of different threshold setting rules for the code acquisition process of a DS spread spectrum receiver. The consideration is made in an AWGN channel where the signal power is assumed to be considerably lower, i.e., faded, part of the time. The performance measure is the mean acquisition time, TMA. A matched filter acquisition is used without any verification mode. In the comparisons, fixed thresholds, thresholds based on constant false alarm (CFAR) criteria and optimal thresholds in the sense to give the minimum TMA are used. The results of a method of using the maximum value at the output of the matched filter are also compared to the threshold cases. The comparisons are made using coherent acquisition. The results indicate that CFAR-method or maximum selection method offers the best performance. By a proper selection of the probability of false alarm in the CFAR-method, the same performance is obtained as by using the optimal thresholds. The selection depends on code length and false alarm penalty time View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Symbol ranking type interference canceller (SRIC) for CDMA system

    Page(s): 2388 - 2392 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    In order to further increase the capacity of the CDMA system, several kinds of interference canceller are proposed. We propose a novel interference canceller named SRIC (symbol ranking type interference canceller). SRIC is very feasible for its small hardware complexity compared with the other multi-user type interference cancellers and is easy to be introduced to the base station afterwards. We have nine variants of SRIC and confirmed their performance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of source-matched channel coding for mobile communications

    Page(s): 2517 - 2521 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    In this paper the applicability of source-sensitivity matched unequal error protection schemes is studied for variable-rate speech transmission on a mobile radio channel. The performance of the unequal error protection scheme is evaluated through simulation taking into account the effects of the channel memory. The simulation of the useful signal and of the interferers is based on the multiplicative fading model developed by Clarke. The effects of channel memory on different error correction and error concealment schemes are evaluated and compared View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Rate control for ABR service in wireless ATM networks

    Page(s): 1905 - 1909 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    This paper proposes a rate control scheme with a binary feedback mechanism for available bit rate (ABR) services in an interconnected wireless/wired asynchronous transfer mode (ATM) network. The rate control system model consists of a single bottleneck node, multiple mobile/fixed traffic sources and a binary feedback scheme. The rate of the mobile ABR source is determined based on the binary feedback that is received from the bottleneck node, as well as on the quality of the wireless link between the mobile source and the base station. A mathematical model for the rate control scheme which takes into consideration the user mobility, wireless channel quality and propagation delays is developed. Markov modulated fluid modeling is used to characterize the stochastic nature of the mobile/fixed sources. We have shown that the system consisting of the multiple mobile/fixed traffic sources, binary feedback scheme, and the bottleneck node server can be modeled using a Markov process. We have derived a set of first-order linear differential equations and appropriate boundary conditions for the stationary distribution of the state process which describes the overall rate control system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigations of single frequency networks for digital mobile radio systems based on COFDM

    Page(s): 2227 - 2231 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    The application of COFDM (coded orthogonal frequency division multiplexing) transmission schemes allows the implementation of power and bandwidth efficient transmitter networks, the so-called single frequency networks. Dependent on the network configuration, the transmission quality can be improved by macro diversity gain, but contrary to that fact, self interference can lower system performance in several locations of the coverage area. The knowledge of these effects is important for network planning. New measurement techniques are required to investigate the properties of single frequency networks. In this contribution, a wideband channel sounder is described for measuring complex transfer functions of the radio channels within a single frequency network. The method is especially designed to distinguish between the signal components of the different transmitters. The complex superposition of the signals in a single frequency network is obtained additionally. The procedure was tested in several field trials. Some results of the evaluation of the measurements are given in the paper View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the performance of single and multi-cell DS-CDMA systems using `non-overlap constellation assignment' to the different groups of spreading codes

    Page(s): 2446 - 2448 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    A method to reduce the effect of intercell and intracell interference in single and multi-cell DS-CDMA systems is considered in this paper. In this method, the users' signatures are not only separated by using different spreading codes but are also partitioned into two or more sub-groups each using an individual constellation for band-pass modulation. Devoting non-overlap parts of the constellation space to the different groups of spreading codes offers capacity enhancement of the system without increasing the processing gain of a standard DS-CDMA system. This transmission method may be combined with joint detection at the receiver to give further performance improvement. By this approach, the complexity of the joint detection techniques can be noticeably reduced View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of dipole and microstrip antenna for a GSM microcell base station

    Page(s): 1969 - 1973 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    This paper presents the analysis of two miniature antennas, namely a dipole and microstrip antenna, which can be used in a GSM 900 MHz system. The performance of the antennas, a vertical dipole and microstrip antenna, is evaluated by calculating and measuring the average field strength in the coverage area. The image theory and the two-slope propagation model are used to calculate the field strength. The received average field strength for a vertical dipole prototype and a microstrip prototype is measured as a function of distance to the microcell antenna and position to the walls. It is concluded that the vertical dipole antenna with polarisation parallel to the mounting wall has the best performance to obtain canyon street coverage View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of double dwell acquisition with continuous integration detector in DS-CDMA system

    Page(s): 2507 - 2511 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    This paper presents the performance of a double dwell acquisition system with a continuous integration detector. In the acquisition system, the first dwell output is combined with the second dwell output to yield the final decision variable. The mean acquisition time is derived and analyzed for the acquisition system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new time-based outage criterion for the forward and reverse links of DS-CDMA cellular systems

    Page(s): 2182 - 2186 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    Previous work on outage criteria and cell admission policies in direct sequence CDMA cellular systems has focused on the reverse, or subscriber-to-base link. Such criteria generally are based on noise at the receiver. We show that a simple received noise rise estimate is not sufficient to declare a blocking or outage situation. We resolve the problem by proposing a new outage calculation which includes both a time sequential factor and simultaneous consideration of the forward link. The outage criterion is based on the inability of the physical transmitting device to produce enough power to generate the subjectively required error rate over some time continuous period. We show how the calculation can be applied to any distribution of subscribers, and cells, and any propagation environment. The outage is calculated not just statistically but can also be located in a realistic environment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Millimeter-wave broadband wireless access system with tracking technology of moving targets

    Page(s): 2057 - 2061 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    There is growing interest in wireless access systems, which can provide multimedia network services. Some wireless access systems which limit the terminal's mobility, already have been proposed. However, a system supporting higher mobility, such as use in a car, is expected in the near future. We are investigating the technical feasibility of such a system. We describe our system and present a new approach for tracking moving targets, which is the key to the system. Finally, some simulation results are also revealed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient maximum likelihood decoding of peak power limiting codes for OFDM

    Page(s): 2081 - 2084 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    We derive an efficient maximum likelihood soft decision decoding method for peak-to-mean power ratio limiting codes, of interest in OFDM transmission schemes. We extend the well known method of decoding first order Reed-Muller codes to the case of Q-ary information vectors and Q-PSK modulation. In addition we describe reduced-complexity methods of decoding, which simulations show to lose only fractions of a dB compared to the maximum-likelihood method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A BER analysis for a candidate satcom channel model for the UMTS

    Page(s): 2338 - 2342 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    This paper is concerned with the performance analysis of UMTS in terms of probability of bit error for DPSK/NCFSK modulation schemes. A wideband channel model is considered with the tapped-delay line structure, random number of taps and randomly varying tap delays. The received signal contains three components, direct path, near echoes, and far echoes. Each component is modelled by different statistics. The direct path is modelled by combining clear Rice and Rayleigh/lognormal statistics, while the near and far echoes are considered to be Rayleigh distributed. For simplicity, the effect of near and far echoes are taken into account by their average power levels rather than by their instantaneous power levels. Effects of shadowing, time factor, and elevation angle are considered. The influence of near and far echoes is considered in different elevation environments View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Migration of adaptive antennas into existing networks

    Page(s): 1670 - 1674 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    This paper addresses migration of adaptive antennas into cellular networks with a conventional antenna technique. Two strategies can be distinguished: an operator can either install adaptive antennas in all cells in one step or gradually introduce adaptive antennas in a step-by-step manner. The latter method is preferred, since it results in lower introduction costs for the operator. The goal with this study has been to investigate whether the step-by-step migration is feasible. Simulations of a realistic heterogeneous network indicate that this approach is indeed possible View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of phase error on M-QAM demodulation in a non-Gaussian environment

    Page(s): 2483 - 2487 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    This paper considers the influence of a deterministic phase error for coherent M-QAM demodulators in a non-Gaussian environment; the latter is modeled as a combination of a white Gaussian process and a filtered Poisson process whose enveloped amplitude obeys the Rayleigh distribution. General results show that when approaching the critical limit, the symbol error rate quickly reaches a plateau having a relatively large width View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A three-dimensional wideband propagation model for the study of base station antenna arrays with application to LMCS

    Page(s): 1805 - 1809 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A model is proposed herein to simulate wideband correlated diversity channel from the point of view of the base station. It is assumed that scattering activity is limited to a local area around the subscriber and possibly additional secondary scattering areas, each being of local extent. Simulation is possible by generating correlated random variates obeying a complex Gaussian law to represent an instance of the impulse response at each antenna element. A mathematical definition of the correlation existing between discrete channel coefficients is provided as a function of separation in space (lag) and separation in frequency. Thus, the channel correlation between antenna elements is characterized by a lag-frequency correlation function in a three-dimensional (cylinder of scatterers) propagation scenario. The mathematical formulation incorporates the effect of arbitrary antenna patterns at the base and at the subscriber station. Simulation proceeds by dividing the band of interest into a number of frequency bins (each smaller than the coherence bandwidth) leading to the construction of a discrete lag-frequency matrix of channel coefficients. Since the model is not concerned with temporal channel variations, it is appropriate for Monte-Carlo simulations for calculations such as outage probability, system capacity, etc View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatial traffic distribution in cellular networks

    Page(s): 1994 - 1998 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A general model describing nonhomogeneities of traffic distributions in cellular networks is presented, together with the results of statistical hypothesis testing. It is shown that the model is applicable to different levels of granularity, e.g. cells and BSC areas. Possible areas of application are capacity estimates, system comparisons and budget planning View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of cellular CDMA systems with space diversity, fading, and imperfect power control

    Page(s): 1868 - 1872 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    It is well known that the capacity of code-division multiple-access (CDMA) systems degrades rapidly with the increase in power control error. The capacity is also affected by small-scale fading such as Rayleigh fading and by the voice activity. We analyze the outage probability of the uplink of a CDMA system. Closed form approximations are provided for two different definitions of the outage encountered in the literature. These expressions provide a simple tool to analyze the system performance as function of diversity, fading, power control error, and voice activity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of nonlinearly amplified multicarrier spread spectrum systems in the presence of multipath fading

    Page(s): 2027 - 2031 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    We analyze the effect of a nonlinearity on the bit error rate performance of multicarrier spread spectrum (MCSS) systems in the presence of multipath fading. A 5th order polynomial model is used to represent the amplifier amplitude nonlinearities (AM/AM) and a flat Rayleigh fading channel is assumed for each modulated carrier. It is found that for the additive white Gaussian noise and multipath fading channel, the bit error degradation from a nonlinear amplification is not as significant as in the additive white Gaussian noise channel alone View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Errors in automatic location identification using timing advance

    Page(s): 1955 - 1958 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    Automatic location identification (ALI) techniques using timing advance (TA) are under active discussion for some TDMA cellular technologies. This technique measures distance from each receiving base station in terms of the amount that the timing of the mobile has to be advanced in order to properly fit into the correct time slot. TA is used as an approximation for TOA (time of arrival-the transit time from mobile station to base station) which allows one to draw circular contours around each receiving antenna; the location of the mobile is at the best intersection of all those contours in the least-squares sense. We analyze the statistical errors from the use of TA as an estimator for TOA and apply the results to example ALI problems. The equipment uses a process whereby a measurement of TOA is made with some intrinsic error and then a broad TA time slot is assigned; the user may not have access to the original TOA measurement. In estimating the errors it is critical to recognize that there is a non-negligible probability that the TOA measurement error is large enough that the wrong TA time slot (i.e., it does not bracket the true value of TOA) may be assigned. Given that the user only knows the time slot, the problem is to find an estimator and its error for the actual TOA View full abstract»

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