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Vehicular Technology, IEEE Transactions on

Issue 4 • Date May 2009

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Displaying Results 1 - 25 of 55
  • Table of contents

    Publication Year: 2009 , Page(s): C1 - C4
    Save to Project icon | Request Permissions | PDF file iconPDF (49 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Vehicular Technology publication information

    Publication Year: 2009 , Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (40 KB)  
    Freely Available from IEEE
  • An Analysis of Probability Distribution of Doppler Shift in Three-Dimensional Mobile Radio Environments

    Publication Year: 2009 , Page(s): 1634 - 1639
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (458 KB) |  | HTML iconHTML  

    The Doppler shift (DS) distribution of the signal that is received by a mobile station in 3D mobile radio environments is closely related to the signal's power spectral density (PSD). From the relationship between the arriving angles and the DS, general equations are derived, bridging the probability density function (pdf) of the elevation angle with the pdf of the DS, its variance, and the characteristic function. These equations are then used to analyze the statistic distribution of the DS based on the semispheroid model, which has been recently proposed by Janaswamy. For this particular model, analytical expressions for the pdf and the variance of the DS have been derived, and a definite-integral expression is provided for the characteristic function. When the average strengths of the waves that are distributed on different equal-Doppler-shift surfaces are assumed to be equal, the derived pdf of the DS is equivalent to the signal's PSD, and the derived characteristic function of the DS is equivalent to the signal's autocorrelation function. View full abstract»

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  • Comparative Investigation of Tram Vibrations

    Publication Year: 2009 , Page(s): 1640 - 1646
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1171 KB) |  | HTML iconHTML  

    The aim of this paper is to investigate the vibrations in a new tram model (the ldquoCombino Plusrdquo) developed by Siemens Company, Germany, which was recently launched on a main Budapest road, and in an older tram model withdrawn from the same line. Comparative measurements were made from terminal to terminal (18 sections). The results of this investigation gave us information about the advances made in relation to the vibrational characteristics of trams. This paper summarizes literature concerning the physiological effects of continuous vibration exposures, as well as the standard ISO 2631, to clarify the relevance of the topic and to draw attention to the recorded parameters of the new ldquoCombino Plusrdquo tram. The new ldquoCombino Plusrdquo tram successfully absorbs the vibrations originating from the roughness of the tram rail. This tram produces significantly less vibration for passengers and drivers than the older model tram withdrawn from the main road traffic. The new Combino Plus satisfies the ergonomic requirements and ensures favorable working conditions. View full abstract»

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  • Performance Evaluation of Vehicle-Based Mobile Sensor Networks for Traffic Monitoring

    Publication Year: 2009 , Page(s): 1647 - 1653
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (421 KB) |  | HTML iconHTML  

    Vehicle-based sensors can be used for traffic monitoring. These sensors are usually set with long sampling intervals to save communication costs and to avoid network congestion. In this paper, we are interested in understanding the traffic-monitoring performance that we can expect from such vehicle-based mobile sensor networks, despite the incomplete information provided. This is a fundamental problem to be addressed. A performance evaluation has been carried out in Shanghai, China, by utilizing the vehicle-based sensors installed in about 4000 taxies. Two types of traffic status-estimation algorithms, i.e., the link-based and the vehicle-based, are introduced and analyzed. The results show that estimations of the traffic status based on these imperfect data are reasonably accurate. Therefore, the feasibility of such an application is demonstrated. View full abstract»

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  • Adaptive Haptic Feedback Steering Wheel for Driving Simulators

    Publication Year: 2009 , Page(s): 1654 - 1666
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1204 KB) |  | HTML iconHTML  

    Controlling a virtual vehicle is a sensory-motor activity with a specific rendering methodology that depends on the hardware technology and the software in use. We propose a method that computes haptic feedback for the steering wheel. It is best suited for low-cost, fixed-base driving simulators but can be ported to any driving simulator platform. The goal of our method is twofold. 1) It provides an efficient yet simple algorithm to model the steering mechanism using a quadri-polar representation. 2) This model is used to compute the haptic feedback on top of which a tunable haptic augmentation is adjusted to overcome the lack of presence and the unavoidable simulation loop latencies. This algorithm helps the driver to laterally control the virtual vehicle. We also discuss the experimental results that demonstrate the usefulness of our haptic feedback method. View full abstract»

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  • Condensation Detection Using a Wirelessly Powered RF-Temperature Sensor

    Publication Year: 2009 , Page(s): 1667 - 1672
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (234 KB) |  | HTML iconHTML  

    The formation of condensation on windshields can be counteracted and even prevented through the concerted use of an automobile heating, ventilation, and air-conditioning (HVAC) system. By anticipating the formation of dew, through the temperature of the windshield and dew point in the cabin, a condensation-free windshield can be ensured. A new approach toward a system for condensation detection is reported. It uses an actively powered humidity sensor, as well as a remotely and wirelessly powered temperature sensor system. The wirelessly powered temperature detector, which may be embedded in the windshield of an automobile, obtains its energy via an inductively coupled magnetic field and simultaneously transmits data through a load-modulation technique. Such a system approach offers advantages in terms of cost, system life, and maintenance, in comparison with existing wired systems and other wireless solutions. The system is implemented using off-the-shelf components and is discretely designed around application-specific resonant tanks. The resonant tanks were mathematically characterized and compared with measured values. The read range of the wirelessly powered condensation detector at a frequency of 13.56 MHz is more than 4 cm while consuming a maximum power of approximately 2 mW. The application of this technology as part of a climate-control system is discussed in this paper. System concept, design considerations, and prototype characterization are also included. View full abstract»

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  • OFDM and Its Wireless Applications: A Survey

    Publication Year: 2009 , Page(s): 1673 - 1694
    Cited by:  Papers (96)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (689 KB) |  | HTML iconHTML  

    Orthogonal frequency-division multiplexing (OFDM) effectively mitigates intersymbol interference (ISI) caused by the delay spread of wireless channels. Therefore, it has been used in many wireless systems and adopted by various standards. In this paper, we present a comprehensive survey on OFDM for wireless communications. We address basic OFDM and related modulations, as well as techniques to improve the performance of OFDM for wireless communications, including channel estimation and signal detection, time- and frequency-offset estimation and correction, peak-to-average power ratio reduction, and multiple-input-multiple-output (MIMO) techniques. We also describe the applications of OFDM in current systems and standards. View full abstract»

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  • Optimal Energy Scheduling for Rate-Guaranteed Download Over Faded Multichannel Networks

    Publication Year: 2009 , Page(s): 1695 - 1710
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (951 KB) |  | HTML iconHTML  

    In this contribution, we consider emerging wireless content delivery networks (CDNs), where multiple (possibly nomadic) clients download large-size files from battery-powered proxy servers via faded links that are composed of multiple slotted orthogonal bearers (e.g., logical subchannels). Since the considered transmit proxy servers are battery-powered mobile routers, a still open basic question deals with searching for optimal energy-allocation (e.g., energy scheduling) policies that efficiently split the available energy over the (faded) bearers. The target is to minimize the resulting (average) download time when constraints on the average available energy per information unit (IU), peak-energy per slot, and minimum energy per bearer (e.g., rate-induced constraints) are simultaneously active. The performance and the robustness of the resulting optimal energy scheduler are tested on the last hop of Rayleigh-faded mesh networks that adopt the so-called ldquodirty paper strategyrdquo for broadcasting multiple traffic flows that are generated by proxy servers equipped with multiple antennas . View full abstract»

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  • Modeling of Single-Step Power Control Scheme in Finite-State Markov Channel and Its Impact on Queuing Performance

    Publication Year: 2009 , Page(s): 1711 - 1721
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (678 KB) |  | HTML iconHTML  

    In this paper, we analyze the queuing performance in the finite-state Markov channel (FSMC) when the single-step power control (SSPC) scheme is adopted. To start with, an SSPC model and its extended power control error (PCE) model are proposed and described in detail. Such models can emulate the behaviors of the interaction between the SSPC and an FSMC and the variation of the PCE with high accuracy. Furthermore, the packet error rate that has been recently analyzed by Lee and Chang is adopted to evaluate the service rate, the time average queuing length, and the probability mass function (PMF) of the queuing length variation. Based on these results, a queuing variation model is proposed to emulate the queuing variation in the FSMC. The flooring phenomenon of the queuing length is observed under a particular requirement of an overflow probability when the SNR value is greater than a certain value. This indicates that the tradeoff among the SNR, the buffer size of the queue, and the overflow probability exists. Hence, two different approaches to select the optimal target SNR of the SSPC and the maximum buffer size of the queue under the requested queuing buffer overflow probability are proposed. The improvement of the SSPC, its impact on the system, and the validity of the proposed models are shown in this paper as well. View full abstract»

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  • Performance Evaluation of a Spectrum-Sensing Technique for Cognitive Radio Applications in B-VHF Communication Systems

    Publication Year: 2009 , Page(s): 1722 - 1730
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (943 KB) |  | HTML iconHTML  

    This paper deals with a cognitive radio approach based on a noncooperative spectrum sensing technique for applications in a very-high-frequency (VHF) aeronautical communications system to detect idle VHF channels and allocate them to an additional overlay system or secondary users. In particular, the focus here is on a spectrum sensing technique belonging to the class of energy detectors based on the Welch windowed periodogram. The performance of the proposed detector is presented in terms of the missed detection probability of the primary user under different application conditions. The obtained results and resulting implementation complexity highlight better behavior of the proposed detector with respect to alternative schemes previously proposed in the literature on this subject. View full abstract»

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  • On the Power Allocation and System Capacity of OFDM Systems Using Superimposed Training Schemes

    Publication Year: 2009 , Page(s): 1731 - 1740
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    Channel estimation in multipath environments is typically performed using the pilot-symbol-assisted modulation (PSAM) scheme. However, the traditional PSAM scheme requires the use of dedicated pilot subcarriers and therefore leads to a reduction in the bandwidth utilization. Accordingly, this paper investigates a channel-estimation approach for orthogonal frequency-division multiplexing (OFDM) systems using a superimposed training (ST) scheme, in which the pilot symbols are superimposed onto the data streams prior to transmission. By using equally spaced pilot symbols of equal power and assuming that the number of pilots is larger than the channel order, it is shown that the channel-estimation performance is independent of the number of pilots used. The optimal ratio of the pilot symbol power to the total transmission power is analyzed to maximize the lower bound of the channel capacity. Overall, the current results show that the ST-based channel estimation schemes have a slightly poorer performance than the PSAM scheme but yield higher system capacity. View full abstract»

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  • Max-Min Fair Pre-DFT Combining for OFDM Systems With Multiple Receive Antennas

    Publication Year: 2009 , Page(s): 1741 - 1745
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    For orthogonal frequency-division multiplexing (OFDM) systems equipped with multiple receive antennas, conventional pre-discrete Fourier transform (DFT) combining cannot balance the signal-to-noise ratio (SNR) performance of all subcarriers. This degrades the whole system performance. In this paper, we propose the use of the max-min fair criterion for pre-DFT combining to solve the problem. Semidefinite relaxation (SDR) is employed to approximate the solution. We also present a simple way to effectively reduce the amount of computation without sacrificing much of the performance. Simulation results show that, for both uncoded and coded OFDM systems, the proposed max-min fair pre-DFT combining solved via SDR can outperform conventional pre-DFT combining under various multipath channel environments with affordable computational complexity. View full abstract»

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  • Blind Symbol Synchronization Based on Cyclic Prefix for OFDM Systems

    Publication Year: 2009 , Page(s): 1746 - 1751
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    In this paper, a blind symbol synchronization algorithm is presented for orthogonal frequency-division multiplexing (OFDM) systems, and a new timing function based on the redundancy of the cyclic prefix (CP) is introduced. It proves that the maximum of this function necessarily points to the correct timing offset, irrespective of channel conditions when the signal-to-noise ratio is high. Using the timing function, the timing offset is estimated through a searching algorithm. Channel power profile and channel length information are unnecessary. Simulation results show that the proposed algorithm is robust and outperforms the existing CP-based algorithms, particularly in frequency-selective fading channels. View full abstract»

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  • Body-Worn Distributed MIMO System

    Publication Year: 2009 , Page(s): 1752 - 1765
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1258 KB) |  | HTML iconHTML  

    In this paper, we analyze the performance of novel wearable multiple-input-multiple-output (MIMO) systems, which consist of multiple electrotextile wearable antennas distributed at different locations on human clothing. For wearable applications, a semidirectional radiation pattern of the wearable patch antenna is preferred over an omnidirectional radiation of conventional dipole antennas to avoid unnecessary radiation exposure to the human body and radiation losses. Additionally, the spatial distribution of the antennas is not constrained as a typical handheld unit. Through theoretical modeling and simulation, the wearable MIMO system is shown to demonstrate a significantly higher channel capacity than a conventional system on a handheld platform (e.g., a compact dipole array or a single dipole), due to enhanced spatial diversity and antenna pattern diversity. The unique effects of antenna directivity and location on the MIMO system capacity are investigated in terms of antenna correlation and effective gain under different wireless channel models. The advantage of a wearable system over a conventional system was further confirmed by detailed physical modeling through the combination of full-wave electromagnetic and ray-tracing simulations. Finally, complex channel response matrices were measured to characterize the performance of a body-worn MIMO system in comparison with a reference full-size dipole antenna. The 319% improvement in 10% outage capacity for the body-worn system over the reference system made of a full-size dipole antenna is consistent with the 288% improvement projected by theoretical modeling and the average 300% improvement found in the physical simulation of two typical indoor scenarios. View full abstract»

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  • Resource Allocation for QoS-Aware OFDMA Using Distributed Network Coordination

    Publication Year: 2009 , Page(s): 1766 - 1775
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1047 KB) |  | HTML iconHTML  

    This paper considers resource allocation for downlink orthogonal frequency-division multiple access (OFDMA). We propose a subcarrier and power-allocation method that differentiates users per service type to fulfill the quality-of-service (QoS) requirements of each user. Network coordination improves the performance of users at the border of the cells and, thus, decreases the minimum sum power for users with guaranteed performance (GP). Best effort (BE) users are then scheduled to maximize their sum capacity. The proposed method only assumes causal coordination between base stations and can be seen as a generalized macro diversity scheme suited for distributed networks. Numerical results show that network coordination increases the ratio of satisfied GP users, as well as the average data rate of BE users. View full abstract»

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  • Interference Analysis in a Poisson Field of Nodes of Finite Area

    Publication Year: 2009 , Page(s): 1776 - 1783
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (507 KB) |  | HTML iconHTML  

    The research for analytical models that are able to estimate the amount of interference, which is the most important cause of performance degradation in wireless networks, has received a lot of attention over the past few years. This interest is expected to increase in the next few years due to the advent of new architectures and communication technologies, such as wireless networks sharing the same (unlicensed) frequency band, infrastructureless wireless networks, and ultrawideband (UWB) systems. In this paper, we try to overcome some of the limitations of the existing interference models and propose an analytical framework for the evaluation of any statistical moment of the interference provided by a Poisson field of nodes located on a given region of limited area. The propagation environment we consider is characterized by a deterministic distance-dependent path-loss model and log-normal shadowing. The present methodology can be used to provide a fast and accurate evaluation of the amount of interference in many practical situations. Exact closed-form expressions are given for some specific cases. View full abstract»

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  • Iterative Joint Detection, Decoding, and Channel Estimation in Turbo-Coded MIMO-OFDM

    Publication Year: 2009 , Page(s): 1784 - 1796
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2069 KB) |  | HTML iconHTML  

    An iterative receiver for a multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system is considered to jointly decode the transmitted bits and estimate the channel state. The receiver consists of a list detector, a turbo decoder, and a channel estimator that is based on the space-alternating generalized expectation-maximization (SAGE) algorithm. This paper proposes a way to improve the convergence of the iterative detection and decoding by using a priori information to also recalculate the candidate list, aside from the log-likelihood ratios (LLRs) of the coded bits. A new list parallel interference cancellation (PIC) detector is derived to approximate an a posteriori probability (APP) algorithm with reduced complexity and minimal losses of performance. Furthermore, the organization of spectrally efficient decision-directed (DD) SAGE channel estimation under a constrained number of detector-decoder iterations is optimized by computer simulations, and the SAGE algorithm itself is modified for nonconstant envelope constellations. The list recalculation is shown to improve convergence. It is also shown that the list PIC detector with good initialization outperforms the K-best list sphere detector (LSD) in the case of small list sizes, whereas the complexities of the algorithms are of the same order. Despite the low preamble density and fast-fading channel, the proposed iterative receiver shows robust performance. View full abstract»

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  • Twin-Cell Detection (TCD): A Code Acquisition Scheme in the Presence of Fractional Doppler Frequency Offset

    Publication Year: 2009 , Page(s): 1797 - 1803
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    As a novel code-acquisition scheme, the twin-cell detection (TCD) is proposed for the acquisition in time of spread-spectrum codes in the presence of fractional Doppler frequency offset (FDFO). When the FDFO exists, the correlation peak that is used for detection during the acquisition process is split into two neighboring peaks with smaller magnitudes, which results in a considerable degradation in the overall acquisition performance of conventional schemes. In the TCD, the decision variable for detection is formed by combining two consecutive correlator outputs so that the influence of the reduction in the correlation peak due to the FDFO can be alleviated. The numerical results show that the TCD can offer a better mean-time-to-synchronization performance than the conventional scheme based on the cell-by-cell detection. View full abstract»

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  • Spectrum-Sensing Algorithms for Cognitive Radio Based on Statistical Covariances

    Publication Year: 2009 , Page(s): 1804 - 1815
    Cited by:  Papers (114)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (574 KB) |  | HTML iconHTML  

    Spectrum sensing, i.e., detecting the presence of primary users in a licensed spectrum, is a fundamental problem in cognitive radio. Since the statistical covariances of the received signal and noise are usually different, they can be used to differentiate the case where the primary user's signal is present from the case where there is only noise. In this paper, spectrum-sensing algorithms are proposed based on the sample covariance matrix calculated from a limited number of received signal samples. Two test statistics are then extracted from the sample covariance matrix. A decision on the signal presence is made by comparing the two test statistics. Theoretical analysis for the proposed algorithms is given. Detection probability and the associated threshold are found based on the statistical theory. The methods do not need any information about the signal, channel, and noise power a priori. In addition, no synchronization is needed. Simulations based on narrow-band signals, captured digital television (DTV) signals, and multiple antenna signals are presented to verify the methods. View full abstract»

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  • Design and Performance of Space–Time Precoder With Hybrid ARQ Transmission

    Publication Year: 2009 , Page(s): 1816 - 1822
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (298 KB) |  | HTML iconHTML  

    Multiple-input-multiple-output (MIMO) technology can efficiently increase the system capacity in rich scattering environments without increasing the bandwidth or transmission power. The precoder for MIMO transmission is a processing technique that exploits the channel state information (CSI) by operating on the signal before transmission to effectively improve link performance. A hybrid automatic repeat request (HARQ) scheme can be incorporated with the linear precoder to ensure highly reliable communication. To fully utilize the type-I HARQ diversity gain, particularly in slow-fading channels, we propose the optimal design principle of linear precoders whose column vectors are correspondingly orthogonal to each other. In addition, the practical solution based on codebook is given in this paper. Finally, simulation results demonstrate the effectiveness of the proposed precoders in reducing the detection of bit error rate (BER) and in improving normalized throughput. View full abstract»

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  • Index Policies for Resource Allocation in Wireless Networks

    Publication Year: 2009 , Page(s): 1823 - 1835
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (713 KB) |  | HTML iconHTML  

    We consider the problem of resource allocation for data transfer between the base station and the users within a cell of a wireless telecommunication network with infinite data queues for each user. The aim is to study the tradeoff between the conflicting objectives of maximizing the system throughput and the quality of service (QoS) to an individual user. Using a policy improvement approach based on Markov decision processes, we develop an intuitive and easy-to-implement index policy. We also demonstrate its superior performance over the existing proportional fair metric algorithm through simulation experiments. View full abstract»

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  • Suitability of DAMA and Contention-Based Satellite Access Schemes for TCP Traffic in Mobile DVB-RCS

    Publication Year: 2009 , Page(s): 1836 - 1845
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB) |  | HTML iconHTML  

    The problem of optimizing access and bandwidth sharing among transmission control protocol (TCP) connections in the mobile digital video broadcasting return channel via satellite (DVB-RCS) is tackled in this paper. After sketching the general system architecture, we explicitly deal with the dynamic assignment of bandwidth to TCP connections on the return link, which is accomplished by a network control center (NCC) placed onboard the satellite. Mobile users access the satellite in multifrequency time-division multiple access (MF-TDMA), whereas they receive data from the NCC in time-division multiplexing (TDM). Two different techniques, based on deterministic and random access, are compared in terms of bandwidth usage and average completion time per connection, when the mobile user acts as both server and client. In the server case, to increase the TCP throughput, both packet-level forward error correction (FEC) on data sent by mobile users and a duplicated and delayed acknowledgment technique for TCP acknowledgment traffic from the NCC to the mobile users are applied. An analysis of the packet losses and a simulation campaign of file transfers by employing a realistic channel model has been carried out. The results of the analysis show the convenience of adopting a technique, in addition to the optimal data redundancy in different cases, such as the server or client role of users, their willingness to pay, the file size, and the environment type. View full abstract»

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  • Markov Chain Trust Model for Trust-Value Analysis and Key Management in Distributed Multicast MANETs

    Publication Year: 2009 , Page(s): 1846 - 1863
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2340 KB) |  | HTML iconHTML  

    To increase efficiency in mobile ad hoc networks (MANETs), the multicast MANET is proposed for a sender that sends packets to several receivers through a multicast session. In MANETs, multicast group members frequently change due to node mobility; thus, supporting secure authentication and authorization in a multicast MANET is more critical than that in a wired network with a centralized certificate authentication (CA) server. This paper thus proposes a two-step secure authentication approach for multicast MANETs. First, a Markov chain trust model is proposed to determine the trust value (TV) for each one-hop neighbor. A node's TV is analyzed from its previous trust manner that was performed in this group. The proposed trust model is proven as an ergodic continuous-time Markov chain model. Second, the node with the highest TV in a group will be selected as the CA server. To increase reliability, the node with the second highest TV will be selected as the backup CA server that will take over CA when CA fails. The procedures of the secure authentication for group management are detailed. The security analysis of each procedure is analyzed to guarantee that the proposed approach achieves a secure reliable authentication in multicast MANETs. In addition, several famous attacks have been analyzed and discussed. Numerical results indicate that the analytical TV of each mobile node is very close to that of simulation under various situations. The speed of the convergence of the analytical TV shows that the analyzed result is independent of initial values and trust classes. This is a good feature of analytical models. View full abstract»

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  • Cross-Layer Radio Resource Allocation for Multicarrier Air Interfaces in Multicell Multiuser Environments

    Publication Year: 2009 , Page(s): 1864 - 1875
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (794 KB) |  | HTML iconHTML  

    Packet scheduling over shared channels is one of the most attractive issues for researchers dealing with radio resource allocation in wireless networks as modern systems' different traffic types, with different application requirements, need to coexist over the air interface. Recently, attention has been attracted to multicarrier techniques and the application of cross-layer approaches to the design of wireless systems. In this paper, a radio access network using a multicarrier air interface is considered in a multicell multiuser context. We propose a new cross-layer scheduling algorithm that manages channel, physical layer, and application-related information; we compare its performance with a previously published cross-layer strategy and with simpler well-known channel-aware or channel-unaware techniques and then discuss its optimization. We investigate the performance in terms of perceived user quality and fairness in the presence of mixed realistic traffic composed of H.264 video streaming with tight bounds on the delay jitter and file transfer protocol (FTP) data. To support video traffic, application-suited buffer-management techniques are also considered in conjunction with scheduling, and link adaptation is implemented at the physical layer to better exploit channel fluctuations. The role of scheduling and resource-allocation functionalities are discussed. It is shown that the cross-layer strategy proposed guarantees the same performance obtained by the previously published algorithm while reducing complexity. Moreover, under heavily loaded conditions, the cross-layer scheduling strategy provides a significant gain with respect to simple channel-aware or channel-unaware techniques. 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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Yuguang Michael Fang
University of Florida