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Vehicular Technology, IEEE Transactions on

Issue 7 • Date Sept. 2012

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Displaying Results 1 - 25 of 48
  • Table of contents

    Page(s): C1 - C4
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    Freely Available from IEEE
  • IEEE Transactions on Vehicular Technology publication information

    Page(s): C2
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    Freely Available from IEEE
  • Battery State-of-Health Perceptive Energy Management for Hybrid Electric Vehicles

    Page(s): 2893 - 2900
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (454 KB) |  | HTML iconHTML  

    This paper presents a causal optimal control-based energy management strategy for a parallel hybrid electric vehicle (HEV). This strategy not only seeks to minimize fuel consumption while maintaining the state-of-charge of the battery within reasonable bounds but to minimize wear of the battery by penalizing the instantaneous battery usage with respect to its relative impact on battery life as well. This impact is derived by means of a control-oriented state-of-health model. The results indicate that the proposed causal strategy effectively reduces battery wear with only a relatively small penalty on fuel consumption. Ultimately, in terms of cost of fuel and battery replacements, the total cost of ownership over the entire life of the vehicle is significantly reduced. View full abstract»

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  • Autonomous Platoon Control Allowing Range-Limited Sensors

    Page(s): 2901 - 2912
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1058 KB) |  | HTML iconHTML  

    This paper investigates control design for the platoon of automated vehicles whose sensors have limited sensing capability. A novel hybrid platoon model is established, in which actuator delay (e.g., the fueling and braking delay) and the effect of sensing range limitation are involved. Based on the new model, a framework of guaranteed-cost controller design is presented, which can robustly stabilize the platoon of vehicles with a given level of disturbance attenuation. The obtained controller is complemented by additional conditions that were established to guarantee string stability and zero steady-state spacing error, yielding a useful string-stable platoon control algorithm. The effectiveness and advantage of the presented methodology is demonstrated by both numerical simulations and experiments with laboratory-scale Arduino cars. View full abstract»

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  • Design of Automatic Steering Controller for Trajectory Tracking of Unmanned Vehicles Using Genetic Algorithms

    Page(s): 2913 - 2924
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1855 KB) |  | HTML iconHTML  

    In this paper, an efficient strategy is proposed to design the automatic steering controller for trajectory tracking of unmanned vehicles, which is robust with respect to the inherent nonlinearities and uncertainties of vehicles. The proposed automatic steering controller consists of a feedback part and a feedforward part. First, a fuzzy controller is proposed as the feedback part, and the parameters of membership functions and rules are optimized by genetic algorithms (GAs) to guarantee high performance. Then, a feedforward controller is designed to assist the controller when the vehicle is engaged in a curved section of trajectory, which utilizes preview information regarding upcoming curvature of reference trajectory to calculate a preview steering angle so that it offsets the disturbance of curvature. Both simulation and experimental results show that the proposed strategy can robustly track the reference trajectories under various conditions with high accuracy. View full abstract»

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  • Battery Cell Identification and SOC Estimation Using String Terminal Voltage Measurements

    Page(s): 2925 - 2935
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (657 KB) |  | HTML iconHTML  

    A battery system consists of many battery cells or modules that may have different characteristics. To achieve reliable, efficient, and extended utilization of battery systems, the battery management system (BMS) must keep track of individual cell-level dynamics, state of charge (SOC), state of health (SOH), failure status, and life-expectancy prediction. Current battery technology employs cell or module-level voltage sensors, with high costs for sensors and packaging, and substantial reliability issues. This paper introduces new methods that utilize existing cell-balancing circuits to estimate an individual cell's voltage and current from battery string terminal voltage/current measurements. This is achieved by actively controlling balancing circuits to create partial observability for battery cell subsystems. Control strategies, estimation algorithms, and their key properties are developed. Some typical battery model structures are used to illustrate the usage of the methods. View full abstract»

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  • Torque Coordination Control During Mode Transition for a Series–Parallel Hybrid Electric Vehicle

    Page(s): 2936 - 2949
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1161 KB) |  | HTML iconHTML  

    Mode transitions are significant events in the operation of series-parallel hybrid electric vehicles (SPHEVs) with a clutch serving as the key enabling actuator element. Due to the friction-induced discontinuity of the clutch torque, seamless transition is difficult to achieve. In this paper, a model reference control (MRC) law is proposed to coordinate the motor torque, engine torque, and clutch torque to manage transitions. The control system is overactuated in the sense that three inputs (i.e., three torques) can be manipulated to control the two outputs (angular speeds of the two sides of the clutch). The effects of using different input combinations are analyzed to exploit the overactuation feature of the system, and performance sensitivities to various design factors are studied. The simulation and experimental results from an SPHEV bus demonstrate that the MRC achieves reduced torque interruption, less vehicle jerk, and smaller frictional losses, compared to the conventional operation method. View full abstract»

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  • Analysis and Evaluation of DC-Link Capacitors for High-Power-Density Electric Vehicle Drive Systems

    Page(s): 2950 - 2964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1754 KB) |  | HTML iconHTML  

    In electric vehicle (EV) inverter systems, direct-current-link capacitors, which are bulky, heavy, and susceptible to degradation from self heating, can become a critical obstacle to high power density. This paper presents a comprehensive method for the analysis and comparative evaluation of dc-link capacitor applications to minimize the volume, mass, and capacitance. Models of equivalent series resistance that are valid over a range of frequency and operating temperature are derived and experimentally validated. The root-mean-square values and frequency spectra of the capacitor current are analyzed with respect to three modulation strategies and various operating conditions over practical ranges of load power factor and modulation index in EV drive systems. The modeling and analysis also consider the self-heating process and resulting core temperature of the dc-link capacitors, which impacts their lifetimes. Based on an 80-kW permanent-magnet (PM) motor drive system, the application of electrolytic capacitors and film capacitors has been evaluated by both simulation and experimental tests. The inverter power density is improved from 2.99 kW/L to 13.3 kW/L, without sacrificing the system performance in terms of power loss, core temperature, and lifetime. View full abstract»

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  • Turbo Packet Combining for Relaying Schemes Over Multiantenna Broadband Channels

    Page(s): 2965 - 2977
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1179 KB) |  | HTML iconHTML  

    This paper focuses on turbo packet combining for multirelay systems operating over multiple-input-multiple-output (MIMO) broadband channels. We consider a relaying protocol that represents a generalization of the classical point-to-point hybrid automatic repeat request (ARQ). In this protocol, relays play the role of packet retransmitters instead of the source. Packet combining has been widely studied for the point-to-point hybrid ARQ, and it has been shown that the virtual-antenna -concept-based combining strategy exhibits block error rate (BLER) performance that is very close to the matched filter bound. However, the extension of this combining strategy to cooperative communications operating under the framework of broadband MIMO channels is not straightforward. In this paper, we revisit this combining strategy. First, we build an appropriate system model in such a way that the cooperation is disguised and the multirelay system becomes equivalent to a point-to-point hybrid ARQ. We investigate the outage probability and outage-based power loss of the considered multirelay system. Then, we extend the turbo packet combiner inspired by the virtual antenna concept to cooperative communications. We focus on implementation issues and propose a hybrid combining strategy. Finally, BLER performances are investigated to demonstrate the gain offered by the studied turbo packet combiner. View full abstract»

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  • Performance Analysis for Superposition Modulated Cooperative Relay HARQ Networks

    Page(s): 2978 - 2990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1098 KB) |  | HTML iconHTML  

    In this paper, a two-user superposition modulated cooperative relay hybrid automatic repeat request (HARQ) system is proposed. Two mobile station (MS) uplink communications to the base station (BS) with cooperative assistance of a relay station (RS) are considered. The RS is assumed to be able to perfectly monitor and decode the two MS-to-BS transmitted packets and assist the two MSs by immediately transmitting a cooperative superposition modulated packet that combines the two MS generated packets in the analog domain. The BS is assumed to have perfect channel statistical information and can feed back the appropriate superposition weighting factor to the RS regularly. The HARQ retransmissions, if needed, are then jointly performed by the RS for both MSs instead of separately for each MS. The superposition of the modulated packets is repeatedly retransmitted by the RS to the BS if needed. With the foregoing setting, we derive an information-theoretic achievable rate region and an approximation of the system outage probability. Based on the high SNR behaviors of the approximated system outage probability, we obtain the superposition weighting factor using a simple and efficient searching algorithm. We also analytically derive the HARQ system throughput as the performance metric for comparison. Compared with the traditional relaying HARQ system, our proposed scheme exhibits more than 30% gain in terms of system throughput, depending on the fading statistics of the RS-to-BS and MS-to-BS channels. View full abstract»

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  • Power Allocation for Multiuser Cooperative Communication Networks Under Relay-Selection Degree Bounds

    Page(s): 2991 - 3001
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (691 KB) |  | HTML iconHTML  

    This paper considers the joint power-allocation and relay-selection problems in multiuser cooperative communication networks, where one user can only seek a limited number of relays for cooperation. This relay-selection degree bound is of practical significance. The goal is to optimize the relay selection and power allocation in a distributed manner while respecting certain users' quality-of-service (QoS) requirements. This problem is challenging due to its combinatorial nature, even from a centralized perspective, let alone distributed algorithms (or protocols). For this joint optimization problem with inherent combinatorial nature, this paper resorts to a layering approach. Specifically, the optimal power allocation for a fixed but arbitrary relay-selection configuration is carried out in the physical layer while the relay selection is done in the media access control (MAC) layer. The general idea is to run distributed relay-selection schemes based on a time-reversible Markov chain over a distributed power-allocation algorithm in the physical layer. It turns out that these methods can approximately solve this joint power allocation and the relay-selection problem with a certain performance guarantee. More importantly, the resulting solution can be implemented in a distributed manner. Numerical results are also presented to demonstrate the performance of the algorithms. View full abstract»

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  • An Optimal Probabilistic Multiple-Access Scheme for Cognitive Radios

    Page(s): 3002 - 3014
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (727 KB) |  | HTML iconHTML  

    We study a time-slotted multiple-access system with a primary user (PU) and a secondary user (SU) sharing the same channel resource. The SU senses the channel at the beginning of the slot. If found free, it transmits with probability 1. If busy, it transmits with a certain access probability that is a function of its queue length and whether it has a new packet arrival. Both users, i.e., the PU and the SU, transmit with a fixed transmission rate by employing a truncated channel inversion power control scheme. We consider the case of erroneous sensing. The goal of the SU is to optimize its transmission scheduling policy to minimize its queueing delay under constraints on its average transmit power and the maximum tolerable primary outage probability caused by the miss detection of the PU. We consider two schemes regarding the secondary's reaction to transmission errors. Under the so-called delay-sensitive (DS) scheme, the packet received in error is removed from the queue to minimize delay, whereas under the delay-tolerant (DT) scheme, the said packet is kept in the buffer and is retransmitted until correct reception. Using the latter scheme, there is a probability of buffer loss that is also constrained to be lower than a certain specified value. We also consider the case when the PU maintains an infinite buffer to store its packets. In the latter case, we modify the SU access scheme to guarantee the stability of the PU queue. We show that the performance significantly changes if the realistic situation of a primary queue is considered. In all cases, although the delay minimization problem is nonconvex, we show that the access policies can be efficiently obtained using linear programming and grid search over one or two parameters. View full abstract»

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  • Cooperative Spectrum Sensing With Location Information

    Page(s): 3015 - 3024
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1297 KB) |  | HTML iconHTML  

    In this paper, we address the problem of cooperatively detecting a primary user (PU) among multiple cognitive users (CUs) when their location information is available at a CU base station. For fast detection, each CU reports a power estimate, based on one-snapshot observation of the radio environment, to the CU base station. A generalized likelihood ratio test (GLRT) is developed at the CU base station to first estimate the transmit power of the PU and then form a test variable for detection. The maximum likelihood estimator (MLE) of the unknown transmit power is discussed and analyzed to offer insight into the proposed cooperative spectrum-sensing scheme. In addition, a weighted average estimator (WAE) is proposed, which is computationally more efficient than the MLE. Asymptotic analysis for the proposed GLRT is presented. Performance of the MLE and WAE is examined along with the corresponding Cramer-Rao bound (CRB). Extensive comparisons between the proposed GLRTs and the hard- and soft-decision based spectrum sensing methods are provided, which show the effectiveness of the proposed detector. View full abstract»

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  • Mimicking Full-Duplex Relaying Using Half-Duplex Relays With Buffers

    Page(s): 3025 - 3037
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (797 KB) |  | HTML iconHTML  

    We propose a new relaying scheme referred to as space full-duplex max-max relay selection (SFD-MMRS), which uses relay selection and half-duplex (HD) relays with buffers to mimic full-duplex (FD) relaying. SFD-MMRS allows the selection of different relays for reception and transmission, which, in turn, enables the relays selected for reception and transmission to simultaneously receive and transmit. With SFD-MMRS, the prelog factor 1/2 is removed from the capacity expression, and better performance in terms of both throughput and outage probability is achieved. We provide a comprehensive analysis of the capacity and outage probability of the proposed scheme for a decode-and-forward (DF) protocol in Rayleigh fading. This analysis reveals that the proposed scheme provides better performance, compared with HD MMRS and HD best relay selection (BRS). Moreover, our simulation results show that the capacity of the proposed scheme with HD relays exceeds twice the capacity of BRS with HD relays for any number of relays. Furthermore, the proposed scheme provides full diversity and large signal-to-noise ratio (SNR) gains, compared with competing schemes in the literature. View full abstract»

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  • Outage Probability of Amplify-and-Forward Two-Way Relay Interference-Limited Systems

    Page(s): 3038 - 3049
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (391 KB) |  | HTML iconHTML  

    This paper studies the outage performance for a two-way relay channel using amplify-and-forward (AF) strategy in interference-limited scenarios. The exact integral-form expression for the system outage probability is derived under distinct-power interference environments. The lower bound and the approximation for the outage probability are also derived in closed form. The optimal power allocation between terminals is obtained in the case when the transmit power of the relay is large and when the effect of interference is discussed. Numerical results demonstrate that the lower bound works well in situations where the transmit power of the relay is smaller than that of the source terminals, whereas the approximation fits perfectly with the exact results in general situations and particularly when the power of the relay is larger than that of the source terminals in interference-limited systems. View full abstract»

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  • Opportunistic Decode-and-Forward Relaying With Beamforming in Two-Wave With Diffuse Power Fading

    Page(s): 3050 - 3060
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB) |  | HTML iconHTML  

    In this paper, we propose new opportunistic decode-and-forward (DF) relaying with beamforming for multirelay networks, where an Ns-antenna source communicates with an Nd-antenna destination with the aid of N parallel single-antenna relays. Among these relays, only one relay that correctly decodes the signal from the source and has the highest instantaneous signal-to-noise ratio (SNR) to the destination is selected for transmission. The source employs maximum ratio transmission (MRT) to transmit, whereas the destination performs maximum ratio combining (MRC) to the received signals. To examine the benefits of the proposed scheme, we first derive the exact outage probability for independently but non-identically distributed (i.n.i.d.) two-wave with diffuse power (TWDP) fading channels. We then derive an easy-to-compute expression for the exact outage probability to reduce computational cost. Our results encompass Rayleigh and Rician fading as special cases. We further derive a compact expression for the asymptotic outage probability, which characterizes two factors governing the network performance at high SNRs, i.e., the diversity order and the array gain. We demonstrate that our scheme preserves the maximum diversity order of N × min {Ns, Nd}. Additionally, we derive the optimal power allocation factor, which provides a practical design rule to optimally distribute the total transmission power between the source and the selected relay to minimize the outage probability. View full abstract»

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  • Analysis of Outage Probability and Throughput for Half-Duplex Hybrid-ARQ Relay Channels

    Page(s): 3061 - 3070
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB) |  | HTML iconHTML  

    We consider a half-duplex wireless relay network with hybrid-automatic retransmission request (HARQ) and Rayleigh fading channels. In this paper, we analyze the average throughput and outage probability of the multirelay delay-limited (DL) HARQ system with an opportunistic relaying scheme in decode-and-forward (DF) mode, in which the best relay is selected to transmit the source's regenerated signal. A simple and distributed relay selection strategy is considered for multirelay HARQ channels. Then, we utilize the nonorthogonal cooperative transmission between the source and selected relay for retransmission of source data toward the destination, if needed, using space-time codes. We analyze the performance of the system. We first derive the cumulative density function (cdf) and probability density function (pdf) of the selected relay HARQ channels. Then, the cdf and pdf are used to determine the exact outage probability in the lth round of HARQ. The outage probability is required to compute the throughput-delay performance of this half-duplex opportunistic relaying protocol. The packet delay constraint is represented by L, which is the maximum number of HARQ rounds. An outage is declared if the packet is unsuccessful after L HARQ rounds. Furthermore, simple closed-form upper bounds on outage probability are derived. Based on the derived upper bound expressions, it is shown that the proposed schemes achieve the full spatial diversity order of N + 1, where N is the number of potential relays. Our analytical results are confirmed by simulation results. In addition, simulation shows that our proposed scheme can achieve higher average throughput, compared with direct transmission and conventional two-phase relay networks. View full abstract»

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  • Low-Overhead Interference Mitigation Scheme for Collaborative Channel Assignment in Overloaded Multiantenna Femtocells

    Page(s): 3071 - 3086
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1589 KB) |  | HTML iconHTML  

    This paper proposes a collaborative-based scheme for a transmit antenna channel assignment in overloaded multiantenna femtocells, with the aim of reducing the overhead load. It is assumed that multiple femtocell access points (FAPs) are deployed to sequentially allocate the available resources to scheduled users while reducing the interference experienced by each active user. The FAPs operate concurrently and each of them is allocated an orthogonal channel and employs a transmit array of arbitrary size. The suitable FAP and its associated transmit channel are then identified based on the noncoherently predicted interference power levels on available channels when feedback links are capacity limited. The effect of possible FAP failure or infeasibility to collaborate is characterized for different operating conditions. The applicability of the proposed scheme for specific cases, such as the use of directional antennas in each FAP or shared channels among different FAPs, is also discussed. For arbitrary statistical models of interference power levels on different channels, the average numbers of collaboration requests and examined transmit antenna channels are quantified. Moreover, the statistics of the resulting interference power are derived, which are then used to study various system performance measures. The effect of the interference threshold on the aforementioned measures for processing load and achieved performance is investigated. Numerical and simulations results are presented to support the analytical development and to clarify the tradeoff between the achieved performance enhancement using the proposed scheme and the required processing load for different operating scenarios. View full abstract»

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  • MIMO Zero-Forcing Detection Analysis for Correlated and Estimated Rician Fading

    Page(s): 3087 - 3099
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    Experimental modeling of wireless fading channels performed by the WINNER II project has been shown to fit a Rician rather than Rayleigh distribution, the latter being assumed in many analytical studies of multiple-input-multiple-output (MIMO) communication systems. Unfortunately, a Rician MIMO channel matrix has a nonzero mean (i.e., specular component) that yields, for the matrix product that determines the MIMO performance, a noncentral Wishart distribution that is difficult to analyze. Previously, the noncentral Wishart distribution has been approximated, based on a first-order-moment fit, by a central Wishart distribution and used to derive average error probability (AEP) expressions for zero-forcing (ZF) detection. We first reveal that this approximation and the MIMO performance evaluation tools derived from it may be reliable only for rank-one specular matrices. We then exploit this approximation to derive an AEP expression for a lesser known, yet optimal, MIMO ZF approach that, unlike the conventional approach, accounts for channel estimation accuracy through the channel statistics. After validating this AEP expression for the rank-one case, it is shown that the ZF performance averaged over realistic (i.e., WINNER II) distributions of the Rician K-factor and azimuth spread (AS) can be much worse than that for the average K and AS. Finally, through simulations, it is shown that the optimal detection approach can substantially outperform the conventional approach for ZF for full-rank specular matrices, as well as for minimum mean square error detection for both rank-one and full-rank specular matrices. View full abstract»

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  • Energy-Efficient Delay-Constrained Transmission and Sensing for Cognitive Radio Systems

    Page(s): 3100 - 3113
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    In this paper, we study energy-efficient transmission for Cognitive Radio (CR) that opportunistically operates on the primary user's channel through spectrum sensing. Spectrum sensing and compulsory idling (for incumbent protection) introduce energy overheads for Secondary User (SU) operations, and thus, an appropriate balance between energy consumption in data transmission and energy overheads is required. We formulate this problem as a discrete-time Markov decision process in which the SU aims at minimizing its average cost (including both energy consumption and delay cost) to finish a target traffic payload through an appropriate rate allocation. Based on certainty equivalent control, we propose a low-complexity rate-adaptation policy that achieves comparable performance with the optimal policy. With the low-complexity policy, we quantify the impact of energy overheads (including the power consumption for spectrum sensing and compulsory idling) on the SU transmission strategy. Specifically, the SU rate increases with the increase of energy overheads, whose marginal impact, however, diminishes. Moreover, the marginal impact of energy overheads is more significant for delay-insensitive traffic compared with that for delay-sensitive traffic. To mitigate the loss due to imperfect spectrum sensing, we quantify that the SU decreases (increases) its rate with a larger misdetection probability (false alarm probability). View full abstract»

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  • Performance Analysis of Digital Communication Systems Over Composite \eta{-}\mu /Gamma Fading Channels

    Page(s): 3114 - 3124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    In this paper, we analyze and evaluate the performance of digital communication systems that operate over a composite fading channel following the η-μ/gamma distribution. More specifically, new analytical expressions for the channel capacity under different transmission schemes are derived in the form of infinite series. For the special case of integer μ values, simplified closed-form expressions are also obtained. Moreover, we deduce exact tractable formulas for the average bit error rate (BER) of various modulation schemes. In the high-power regime, simplified capacity and BER expressions are provided, revealing the implications of the model parameters on system performance. The relationship of the presented results with previously reported results on generalized- K and K fading channels is also established. We note that the theoretical results presented herein are given in analytical form, which can efficiently be evaluated. View full abstract»

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  • A Novel Distributed Asynchronous Multichannel MAC Scheme for Large-Scale Vehicular Ad Hoc Networks

    Page(s): 3125 - 3138
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1668 KB) |  | HTML iconHTML  

    This paper proposes a novel distributed asynchronous multichannel medium access control (MAC) scheme for large-scale vehicular ad hoc networks (VANETs), i.e., asynchronous multichannel medium access control with a distributed time-division multiple-access mechanism (AMCMAC-D). The proposed scheme supports simultaneous transmissions on different service channels while allowing rendezvous and broadcast of emergency messages on the control channel. The scheme is distributed, because it handles access to the shared control channel for different access categories without relying on the beacon frames from roadside units. This condition eliminates the overhead that is associated with channel allocation, making the proposed scheme suitable for large-scale networks in terms of the number of active nodes. Service differentiation in the proposed scheme is enhanced by allocating different numbers of time slots for different access categories. We compare the performance of the proposed scheme with the IEEE 1609.4 standard and the asynchronous multichannel Coordination Protocol (AMCP) in terms of throughput, packet delivery rate, collision rate, utilization of service channels, service differentiation, and the penetration rate of noncollided emergency messages. The results show that AMCMAC-D outperforms the IEEE 1609.4 standard and AMCP in terms of system throughput by increasing the utilization of the control channel and service channels. The proposed scheme also demonstrates better performance in terms of packet delivery rate, collision rate on a service channel, load balancing, and service differentiation. Finally, AMCMAC-D mitigates the multichannel hidden terminal and missing receiver problems, which occur in asynchronous multichannel MAC schemes. View full abstract»

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  • Analysis of the Impact of Site Planning on the Performance of Relay Deployments

    Page(s): 3139 - 3150
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1597 KB) |  | HTML iconHTML  

    Network planning tools are routinely used by operators to improve the system performance and to provide a satisfactory service with minimal deployment expenditure. In this context, the deployment flexibility of relay nodes, which mainly stems from the wireless backhaul link, compact physical characteristics, and low power consumption, can be exploited to enhance the system performance. In this paper, we model and analyze two simple approaches that can be used for the planning of two-hop cellular relay networks. The aim of the so-called relay location selection and serving cell selection approaches is to enhance system performance by improving the quality of the wireless relay backhaul link. Location selection takes into account the shadowing properties at the different possible relay node deployment locations, considering only the link quality toward the serving base station. On the other hand, cell selection considers the case where a relay node performs cell reselection from a severely shadowed serving base station to a neighboring cell that is less shadowed. A simple model for evaluating and analyzing the impact of both network planning techniques on the system performance of relay deployments is given. In addition, we present the analytical framework through closed-form derivations of the signal-to-interference ratio (SIR) and end-to-end rate distributions. Performance evaluations that investigate the impact of site planning on the quality of the relay backhaul link, end-to-end rate, resource allocation on the two hops, upper bounds on planning gains, access-link limitations, and the deployment of multiple relay nodes are carried out. Results show significant improvements, which justify the need for relay site planning in relay enhanced networks. View full abstract»

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  • Wireless Mesh Network Capacity Achievable Over the CSMA/CA MAC

    Page(s): 3151 - 3165
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (513 KB) |  | HTML iconHTML  

    This paper presents a theoretical analysis of the maximum throughput of a wireless mesh backhaul network that is achievable over a practical carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol. We resort to the multicommodity flow (MCF) formulation augmented with the conflict-graph constraints, whereas we use a novel approach to take into account the collision overhead in the distributed CSMA/CA MAC. Such overhead due to random access has been ignored by existing MCF-based capacity studies, which assume impractical centralized scheduling and result in aggressive capacity planning, which is unachievable over the CSMA/CA MAC. This paper makes the following three main contributions: 1) we develop a generic method of integrating the CSMA/CA MAC analysis with the MCF formulation for optimal network capacity analysis, which readily generates an upper bound of the network throughput; 2) we define a new concept of CSMA/CA clique and theoretically study its relationship to a CSMA/CA area in terms of throughput; and 3) using the CSMA/CA clique as a tool, we derive a lower bound of the network throughput achievable over the CSMA/CA MAC by clique-based MCF formulation. NS-2 simulation results are presented to demonstrate the tightness of the upper and lower bounds that are newly developed, compared to those based on the MCF formulation assuming a slotted system and centralized scheduling. View full abstract»

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  • A Scalability and Performance Analysis of Preauthentication Algorithms for Wireless Networks

    Page(s): 3166 - 3176
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB) |  | HTML iconHTML  

    Secure wireless networks strive to maintain continuity of service while its subscribers move among fixed access points. In vehicular networks, handovers may happen rapidly, and the service continuity from Mobile IPv6 services provides a distinct advantage. Unfortunately, the requirement to authenticate each subscriber as it is passed to each new access point results in a time delay that translates into breaks in connectivity and undesirable retransmission of packets. To provide continuity of service in secure wireless networks, preauthentication algorithms have been proposed that accomplish the authentication process before the user is officially serviced by the access point. We are particularly interested in preauthentication algorithms that efficiently provide preauthentication to likely “next” access points. This paper compares the performance of three different preauthentication algorithms integrated into Fast Mobile IPv6 using signals from the IEEE 802.21 media independent handover framework. Through analysis and simulation, we compare different alternative preauthentication options using four measures of effectiveness as the basis of comparison. 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