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Vehicular Technology, IEEE Transactions on

Issue 4 • Date July 2003

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Displaying Results 1 - 25 of 38
  • Performance analysis of CDMA systems with integrated services

    Publication Year: 2003 , Page(s): 823 - 836
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (765 KB) |  | HTML iconHTML  

    The paper analyzes the performance of unslotted code-division multiple-access schemes with integrated services, namely real-time voice services and nonreal-time data services. In order to support integrated services using a common infrastructure, we apply dedicated mode transmission for real-time services and common channel transmission for nonreal-time services with varying processing gain. Most previous work covers the analysis of the system for fixed or exponential packet length, infinite population and infinite buffer size, where the results mainly depend on the mean values of the traffic. We remove these assumptions and analyze the behavior of the system with respect to voice and data users for the more general and realistic case of finite population, finite buffers, and variable data-packet length. Emphasis is placed on the study of the effect of system parameters and user characteristics on the system performance. Specifically, we show via analysis and simulation that even when the mean data-packet length is small, the system can have bottlenecks due to the packet-length characteristics and, therefore, dynamic adaptation and control of the system is required. Our analytical tool can be used to develop and analyze optimal resource-allocation strategies to maximize the throughput of wireless systems with integrated services. It is shown that optimum variable system parameters can be found when the system parameters and quality-of-service requirements of multimedia services are given. View full abstract»

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  • Effective paging procedure for the optical feeder microcellular system

    Publication Year: 2003 , Page(s): 837 - 846
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    The paper considers a paging problem in the optical feeder microcellular system where group simulcasting and dynamic channel allocation technologies are incorporated. The objective is to propose an effective paging procedure whose performance is measured in terms of paging load, average paging delay, and paging success probability. In the paging procedure, paging signals are transmitted via group simulcasting, for which the control channel is allocated dynamically. The performance of the procedure is analyzed in an approximate queueing network model. The proposed procedure is then compared in performance with a simulation approach, from which the procedure is found to outperform any previous methods in the literature. View full abstract»

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  • An improved tabu search algorithm for the fixed-spectrum frequency-assignment problem

    Publication Year: 2003 , Page(s): 891 - 901
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    A tabu search algorithm with a dynamic tabu list for the fixed-spectrum frequency-assignment problem is presented. For cellular problems, the algorithm can be combined with an efficient cell reoptimization step. The algorithm is tested on several sets of test problems and compared with existing algorithms of established performance. In particular, it is used to improve some of the best existing assignments for COST 259 benchmarks. These results add support to the claim that the algorithm is the most effective available, at least when solution quality is a more important criterion than solution speed. The algorithm is robust and easy to tune. View full abstract»

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  • Maximum-likelihood frame timing instant and frequency offset estimation for OFDM communication over a fast Rayleigh-fading channel

    Publication Year: 2003 , Page(s): 1049 - 1062
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (853 KB) |  | HTML iconHTML  

    A novel maximum-likelihood (ML) technique for frame timing instant and frequency offset estimation in an orthogonal frequency-division multiplexing system is investigated. By taking advantage of the cyclic prefix within the guard interval, the proposed technique can accurately estimate the frame timing instant and frequency offset with no assistance from pilot symbols. The proposed technique also takes fast Rayleigh fading into consideration for the purpose of wireless applications. Furthermore, several combining techniques are also investigated in order to improve the performance of the proposed estimators. Extensive simulation experiments show that the proposed techniques can effectively achieve lower estimation errors in frame timing and frequency offset estimation. View full abstract»

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  • Performance analysis of O3BPSK LDD for asynchronous CDMA systems in the presence of synchronization errors

    Publication Year: 2003 , Page(s): 958 - 969
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (876 KB) |  | HTML iconHTML  

    A convenient signaling scheme, termed orthogonal on-off binary phase-shift keying (O3BPSK), along with a simple one-shot linear decorrelating detector (LDD), was proposed by F.C. Zheng and S.K. Barton (see ibid., vol.47, p.969-76, 1998; Proc. IEEE PIMRC'94, p.194-8, 1994) as a technique for near-far resistant detection in asynchronous direct-sequence code-division multiple-access (DS/CDMA) systems. The temporally adjacent bits from different users in the received signals are decoupled by using on-off signaling, and the data rate is maintained with no increase in the transmission rate by adopting an orthogonal structure. The paper examines the effects of three classes of synchronization errors (time-delay errors, carrier phase errors, and carrier frequency errors) on the performance of the O3BPSK LDD in an asynchronous CDMA near-far environment. It is shown that the performance of the O3BPSK LDD has an advantage over that of the isolation bit insertion detector in the presence of synchronization errors. In addition, numerical results show that the O3BPSK LDD still offers a good near-far resistant property as long as synchronization errors do not exceed some practical limit. View full abstract»

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  • Dynamic model-based filtering for mobile terminal location estimation

    Publication Year: 2003 , Page(s): 1012 - 1031
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1174 KB) |  | HTML iconHTML  

    Mobile terminal location is an important area of research because of its applications in location-sensitive browsing and resource allocation. The paper presents a method for reducing the error in mobile terminal location estimation. A preprocessor using nonparametric estimation is used to reduce the effects of non-line-of-sight and multipath propagation on the location procedure. A model-based dynamic filter is presented that uses an accurate model of mobile terminal motion to combine information from location measurements made at different time instances to create an improved location estimate. The model of mobile terminal motion has a kinematic state space model describing the physical rules governing terminal motion and a control model that describes the human control input into the motion process. Location dependency in the control input model is used to derive a new dynamic filter. This filter provides greatly improved accuracy over previously known location techniques and is much more robust to variations in the mobile terminal motion and nonlinear effects in the propagation environment. View full abstract»

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  • Iterative space-time soft interference cancellation for UMTS-FDD uplink

    Publication Year: 2003 , Page(s): 919 - 930
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (795 KB) |  | HTML iconHTML  

    Two efficient pilot-aided iterative space-time interference cancellation receivers are studied in order to increase the uplink capacity of the Universal Mobile Telecommunication System (UMTS) in frequency-division duplex (FDD) mode. Both iterative schemes use low-complexity beamforming and path combining techniques associated with soft-input soft-output decoding to mitigate the multiple-access interference in space and time. The difference between the two techniques is in the way they deal with unknown channels: the addition of a space-time channel estimation in each iteration on the one hand and iterative adaptive beamforming and path combining on the other hand. Thanks to the iterative structure, the observation signal used for estimation or adaptation contains less interference from one iteration to the following, and soft estimates of coded bits are available for data-aided estimation or adaptation. A detailed complexity analysis shows that renewing beamforming and path combining in each iteration without a-priori knowledge of the channel has no significant impact on the overall complexity of one iteration. Simulations of true UMTS-FDD uplink communications over a wideband directional channel model reveal that near-single user performance can be obtained for very high system loads, whereas more conventional receivers, such as the interference canceller without beamforming and the two-dimensional RAKE receiver, fail in recovering the transmitted information. View full abstract»

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  • Cell-coverage estimation based on duration outage criterion for CDMA cellular systems

    Publication Year: 2003 , Page(s): 814 - 822
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    Previous papers addressing coverage analysis for code-division multiple-access (CDMA) cellular networks have focused on cell expansion from soft handoff or estimation of cell coverage based on an instantaneous outage criterion. Instantaneous outage estimates of cell coverage are a worst case assessment in that the predicted coverage as a function of the number of users is necessarily smaller than the actual coverage. We present the theoretical framework for estimating reverse-link cell coverage based on a duration outage criterion. Our results show that coverage estimates based on duration outage are typically 15%-30% larger than coverage estimates based on instantaneous outage when the correlation distance of the large-scale shadowing environment is small. We compare our theoretical duration outage results of cell coverage with simulated results that considered various large-scale shadowing conditions as well as Rayleigh small-scale fading. The theoretical and simulated coverage results are found to be in very good agreement. The simulations confirm that the presented theoretical duration outage analyses provide accurate and realistic estimates of reverse-link CDMA cell coverage. View full abstract»

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  • A secure and efficient conference scheme for mobile communications

    Publication Year: 2003 , Page(s): 784 - 793
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (545 KB) |  | HTML iconHTML  

    A growing application area in mobile communications is mobile teleconferencing, in which a group of mobile users collaborate in an interactive procedure, such as a board meeting, a task force, a scientific discussion, or even a virtual classroom. Wireless communications transmit conversations via radio, making them more susceptible to eavesdropping and unauthorized access than are conversations carried via wires. Therefore, it is crucial to ensure confidentiality and authenticity in mobile teleconferencing. When deploying secure services in mobile teleconferences, it has to be taken into account that the mobility of users is usually built on portable devices with limited computing capability. A secure conference scheme for mobile communications needs to be executed efficiently on portable devices. We propose a new secure and efficient conference scheme for mobile communications. Based on a modular square root technique, this scheme is secure against eavesdropping, impersonating, and tracking attacks and allows a participant to join or quit a mobile teleconference dynamically. In addition, the scheme is particularly efficient on the mobile user's portable device because the mobile user needs to perform only single modular multiplication plus encryptions and decryptions of a secret key cryptosystem. View full abstract»

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  • On topology improvement of a packet radio network by power control

    Publication Year: 2003 , Page(s): 985 - 998
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1202 KB) |  | HTML iconHTML  

    The packet radio network (PRN) is an attractive architecture for wireless data communication. The code assignment problem in PRN is a classical problem that has been extensively studied. However, we observe that the power control issue has been ignored by most works but may have significant impact on the PRN's performance. Given a set of PRN stations, the network topology can be changed by adjusting each station's transmission power. All existing works, nevertheless, assume that the network topology is given before solving the code assignment problem. We regard code assignment as an independent problem and show how to improve the network topology by power adjustment without violating the original code assignment. The improvement in topology (such as more links in the network) may result in improvement in network throughput. Through simulations, we demonstrate that, although the code assignment problem is NP-complete, our power adjustment schemes can easily improve the network performance by about 10% with polynomial costs. View full abstract»

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  • Channel assignment for initial and handoff calls to improve the call-completion probability

    Publication Year: 2003 , Page(s): 876 - 890
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (753 KB) |  | HTML iconHTML  

    The paper focuses on how to assign channels for initial and handoff calls. Previous schemes give priority to handoff calls by queuing handoff calls, reserving some channels for handoff calls, or subrating existing calls for handoff calls. We queue both initial and handoff calls. We take this idea from derivations of the optimal value for an approximation to the call-completion probability. Our goal is to have higher call-completion probability and still keep forced-termination probability low. We propose four schemes: SFTT (single-queue, FIFO, timeout, average timeout), SPTT (single-queue, priority, timeout, average timeout), DFTS (dual-queues, FIFO, timeout, statistical TDM), and DPTS (dual-queues, priority, timeout, statistical TDM). The four schemes, along with the NPS and FIFO schemes, were simulated and compared. For the SFTT scheme, we also simulated different average timeouts for initial calls. All four proposed schemes have better call-completion probabilities than the NPS and FIFO schemes. Call-completion probabilities can be improved by implementing a priority scheme which serves the waiting call with the least remaining time first. The implementation of statistical multiplexing also has the effect of increasing call-completion probability when the average new-call arrival rates are high. However, both the priority scheme and statistical multiplexing may increase forced-termination probability. View full abstract»

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  • Topology-transparent time division multiple access broadcast scheduling in multihop packet radio networks

    Publication Year: 2003 , Page(s): 970 - 984
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1221 KB) |  | HTML iconHTML  

    Many topology-dependent transmission scheduling algorithms have been proposed to minimize the time-division multiple-access frame length in multihop packet radio networks (MPRNs), in which changes of the topology inevitably require recomputation of the schedules. The need for constant adaptation of schedules-to-mobile topology entails significant problems, especially in highly dynamic mobile environments. Hence, topology-transparent scheduling algorithms have been proposed, which utilize Galois field theory and Latin squares theory. We discuss the topology-transparent broadcast scheduling design for MPRNs. For single-channel networks, we propose the modified Galois field design (MGD) and the Latin square design (LSD) for topology-transparent broadcast scheduling. The MGD obtains much smaller minimum frame length (MFL) than the existing scheme while the LSD can even achieve possible performance gain when compared with the MGD, under certain conditions. Moreover, the inner relationship between scheduling designs based on different theories is revealed and proved, which provides valuable insight. For topology-transparent broadcast scheduling in multichannel networks, in which little research has been done, the proposed multichannel Galois field design (MCGD) can reduce the MFL approximately M times, as compared with the MGD when M channels are available. Numerical results show that the proposed algorithms outperform existing algorithms in achieving a smaller MFL. View full abstract»

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  • The performance of turbo coding over power-controlled fading channel in Ka-band LEO satellite systems

    Publication Year: 2003 , Page(s): 1032 - 1043
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (741 KB) |  | HTML iconHTML  

    The integration of power control and turbo coding is adopted to achieve reliable communications over Ka-band code-division multiple-access (CDMA)-based low Earth orbit (LEO) satellite systems. The effect of imperfect power control on the bit error ratio (BER) performance is analyzed, and the upper bounds on BER are also derived for the case of slow and fast imperfect power control. The analytical and simulation results show that power-control error (PCE) degrades the BER performance of turbo-decoded systems significantly in the waterfall region. In the region of the error floor, the degradation effect slows down and the BER obtained under imperfect power control eventually converges with the BER under perfect power control. Moreover, in the waterfall region, the correlation characteristics of the PCE fluctuation do not degrade the BER performance as anticipated. View full abstract»

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  • Per-survivor processing-based decoding for space-time trellis code

    Publication Year: 2003 , Page(s): 1173 - 1178
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (449 KB) |  | HTML iconHTML  

    The problem of adaptive decoding of space-time trellis codes on time-variant wireless channels is considered. We show that per-survivor processing (PSP) can be adopted to obtain approximated adaptive maximum-likelihood sequence detection (MLSD) of space-time trellis codes when there is no periodically inserted orthogonal pilot sequence. Then we propose a self-tuning least mean square (LMS)-based PSP decoder and a second-order LMS-based one. The former has the advantage that there are only fading rate-independent parameters to be predetermined, while the latter can offer fairly good performance on moderately fast time-varying channels. View full abstract»

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  • Automotive fault diagnosis - part II: a distributed agent diagnostic system

    Publication Year: 2003 , Page(s): 1076 - 1098
    Cited by:  Papers (22)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1276 KB) |  | HTML iconHTML  

    For pt.I see Crossman, J.A. et al., ibid., p.1063-75. We describe a novel diagnostic architecture, distributed diagnostics agent system (DDAS), developed for automotive fault diagnosis. The DDAS consists of a vehicle diagnostic agent and a number of signal diagnostic agents, each of which is responsible for the fault diagnosis of one particular signal using either a single or multiple signals, depending on the complexity of signal faults. Each signal diagnostic agent is developed using a common framework that involves signal segmentation, automatic signal feature extraction and selection, and machine learning. The signal diagnostic agents can concurrently execute their tasks; some agents possess information concerning the cause of faults for other agents, while other agents merely report symptoms. Together, these signal agents present a full picture of the behavior of the vehicle under diagnosis to the vehicle diagnostic agent. DDAS provides three levels of diagnostics decisions: signal-segment fault; signal fault; vehicle fault. DDAS is scalable and versatile and has been implemented for fault detection of electronic control unit (ECU) signals; experiment results are presented and discussed. View full abstract»

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  • A selective interference-cancellation receiver for antenna-array WCDMA communication systems

    Publication Year: 2003 , Page(s): 1162 - 1166
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (395 KB) |  | HTML iconHTML  

    The paper deals with a multiuser cancellation-detection scheme combined with an antenna array for wideband code-division multiple-access (WCDMA) communication systems in which different traffic loads and data rates are considered. This receiver, defined as a space-time selective parallel interference-cancellation detector, should be used at the base station of a WCDMA communication system. Asynchronous users and multipath fading phenomena are considered. The receiver basic assumption is to divide signals into two different groups according to the received power level. The reliable signals are directly detected and cancelled from the whole received signal at each sensor before making the decision about unreliable signals without any further processing delay. Performance evaluations have been carried out in terms of Pe (bit error probability) by means of computer simulations. In particular, it is shown that our receiver exhibits good behavior and lowers the computational complexity in comparison with previously proposed alternatives. View full abstract»

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  • Teletraffic analysis of hierarchical cellular communication networks

    Publication Year: 2003 , Page(s): 931 - 946
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (991 KB) |  | HTML iconHTML  

    The sustained increase of users and the request for advanced multimedia services are amongst the key motivations for designing new high-capacity cellular telecommunication systems. The proposals that are being pursued by several studies and field implementations consider hierarchical architectures and dynamic resource allocation. A hierarchical cellular communication network is analyzed, taking user mobility into account and exploiting dynamic channel-allocation schemes. In particular, a finite number of users has been considered, moving at different speeds in a geographical region covered by a finite number of cells structured in two hierarchical levels: micro- and macrocells. For such a system, mobility and traffic models have been developed, both based on queueing networks analyzing maximum packing (MP), a dynamic channel-allocation scheme. The obtained results, validated by simulation experiments, allow the evaluation of main system-performance parameters in terms of new-call and handoff blocking probabilities, and forced-termination probability as a function of load and system parameters. View full abstract»

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  • Channel assignment using genetic algorithm based on geometric symmetry

    Publication Year: 2003 , Page(s): 860 - 875
    Cited by:  Papers (28)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1020 KB) |  | HTML iconHTML  

    The paper deals with the channel assignment problem in a hexagonal cellular network with two-band buffering, where channel interference does not extend beyond two cells. Here, for cellular networks with homogeneous demands, we find some lower bounds on the minimum bandwidth required for various relative values of s0, s1, and s2, the minimum frequency separations to avoid interference for calls in the same cell, or in cells at distances of one and two, respectively. We then present an algorithm for solving the channel assignment problem in its general form using the elitist model of genetic algorithm (EGA). We next apply this technique to the special case of hexagonal cellular networks with two-band buffering. For homogeneous demands, we apply EGA for assigning channels to a small subset of nodes and then extend it for the entire cellular network, which ensures faster convergence. Moreover, we show that our approach is also applicable to cases of nonhomogeneous demands. Application of our proposed methodology to well-known benchmark problems generates optimal results within a reasonable computing time. View full abstract»

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  • A fast rerouting scheme using reservation in wireless ATM

    Publication Year: 2003 , Page(s): 1125 - 1142
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1524 KB) |  | HTML iconHTML  

    With growing demand for higher bandwidth multimedia services in the wireless domain over the past few years, wireless asynchronous transfer mode (ATM) has emerged as a fine solution. Wireless ATM provides mobility support for mobile ATM users as they move among base stations. One of the key issues to support user mobility is the handoff. For a relatively smaller cell environment in wireless ATM, a handoff scheme should exhibit low handoff delay. Efficient usage of network resources is also required. We propose a fast rerouting scheme for wireless ATM; it is referred to as a path reservation scheme. For localized handoffs, we adopt a wireless cell clustering method. Cell grouping and a path reservation technique are proposed to achieve fast handoffs. The paper presents an analysis of the proposed scheme and simulation results of several handoff schemes compared with the proposed scheme. From the simulation results, our path reservation scheme achieves low handoff delay and efficient usage of network resources such as buffer and bandwidth requirements. View full abstract»

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  • Call management based on the mobile terminal-peak velocity: virtues and limitations in a two-tier cellular system

    Publication Year: 2003 , Page(s): 794 - 813
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1112 KB) |  | HTML iconHTML  

    The aim of the presented research is to study an effective algorithm for the admission control and handoff management of mobile user connections in a realistic urban scenario with a two-tier (micro- and macrocell) cellular coverage. The algorithm behavior is strongly related to the knowledge of the mobility profile of the users. Thus, an analysis of analogous algorithms available in literature and which exploit mobility estimation precedes our design activity. Their advantages and drawbacks have been observed and are used as a starting point for the design of our algorithm. It overcomes the weaknesses that the previous algorithms show when operating in a realistic urban scenario. As a consequence, it reduces the call-blocking probability and minimizes the handoff rate. View full abstract»

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  • An approach to connection admission control in single-hop multiservice wireless networks with QoS requirements

    Publication Year: 2003 , Page(s): 1110 - 1124
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (763 KB) |  | HTML iconHTML  

    We present an approach to connection admission control in single-hop multiservice wireless networks with quality of service (QoS) requirements. The approach consists of two steps: 1) the specification of an admission region that captures the QoS requirements; 2) the formulation of a generalized knapsack problem that captures the connection admission control. To illustrate approach 1), we determine an outage-based admission region; to illustrate approach 2), we investigate the performance of the greedy admission policy in a generalized knapsack problem. View full abstract»

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  • Maltese-cross coaxial balun-fed antenna for GPS and DCS1800 mobile communication

    Publication Year: 2003 , Page(s): 779 - 783
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    A novel antenna in the shape of a Maltese cross has been developed for GPS satellite and DCS1800 personal communication system application. This antenna exhibits good circular polarization (axial ratio <2 dB) and impedance performance over a bandwidth wide enough to cover the frequency band for GPS and DCS1800 reception. The addition of an adjustable clamp and tapering of the shape of the radiating elements improved the overall design. The gain of this antenna has been sufficiently high to compensate for the power loss due to polarization mismatch for the reception of a linearly polarized GSM/DCS1800 signal. A modular design and integration approach is presented to obtain the circular polarization required for GPS application. View full abstract»

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  • Reference-based dual switch and stay diversity systems over correlated Nakagami fading channels

    Publication Year: 2003 , Page(s): 902 - 918
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1471 KB) |  | HTML iconHTML  

    We provide new generic and exact analytical results for the performance of nonideal reference-based dual predetection switch and stay diversity systems in receiving M-ary digitally modulated signals in the presence of additive white Gaussian noise and correlated slow and nonselective Nakagami-m fading channels. Pilot-tone-aided, pilot-symbol-aided, and differential detection (DD) reference-based systems are considered. The impact of symbol alphabet cardinality, normalized distance between antennas, fading severity, and normalized Doppler frequency on the performance of these systems is analyzed. Optimum switching threshold and optimum pilot-to-signal power ratio as a function of channel fading characteristics, normalized distance between antennas, and modulation type are determined. Furthermore, some fixed switching strategies - minimum cost strategy, fixed average strategy, and midpoint strategy - that allow one to obtain diversity gain with a reduced complexity receiver are considered. View full abstract»

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  • Analysis of switching characteristics of the digital hybrid PLL frequency synthesizer

    Publication Year: 2003 , Page(s): 1044 - 1048
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (469 KB)  

    We address the switching characteristics of the digital hybrid phase-locked loop (DH-PLL) frequency synthesizer. We analyze the effects of the division ratio for frequency synthesis and the component errors of a DH-PLL circuit on the switching performance. Gain variation, offset error generated in a digital-to-analog converter, and frequency drift error of voltage-controlled oscillation due to temperature and aging are considered as the errors of the circuit components. From the simulation results, the conventional charge-pump PLL system has much different switching time for the change spacing of the frequency synthesis. On the contrary, the variation of the switching time is not so great in the DH-PLL system when the error magnitude does not exceed the ±4 least significant bit error. To guarantee the required minimum switching speed, it is important that the tolerable error range be determined. View full abstract»

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  • Automotive signal fault diagnostics - part I: signal fault analysis, signal segmentation, feature extraction and quasi-optimal feature selection

    Publication Year: 2003 , Page(s): 1063 - 1075
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB)  

    The paper describes our research in vehicle signal fault diagnosis. A modern vehicle has embedded sensors, controllers and computer modules that collect a large number of different signals. These signals, ranging from simple binary modes to extremely complex spark timing signals, interact with each other either directly or indirectly. Modern vehicle fault diagnostics very much depend upon the input from vehicle signal diagnostics. Modeling vehicle engine diagnostics as a signal fault diagnostic problem requires a good understanding of signal behaviors relating to various vehicle faults. Two important tasks in vehicle signal diagnostics are to find what signal features are related to various vehicle faults, and how can these features be effectively extracted from signals. We present our research results in signal faulty behavior analysis, automatic signal segmentation, feature extraction and selection of important features. These research results have been incorporated in a novel vehicle fault diagnostic system, which is described in another paper (see Yi Lu Murphey et al., ibid., p.1076-98). 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