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Vehicular Technology, IEEE Transactions on

Issue 2 • Date Feb. 2014

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Displaying Results 1 - 25 of 53
  • 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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  • Propagation Measurements and Modeling of Crossing Bridges on High-Speed Railway at 930 MHz

    Page(s): 502 - 517
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2882 KB) |  | HTML iconHTML  

    Bridges that cross a railway's right-of-way are one of the most common obstacles for wave propagation along a highspeed railway. They can lead to poor coverage or handover failure but have been rarely investigated before. To describe the influence of this nonnegligible structure on propagation, measurements have been taken at 930 MHz along a real high-speed railway in China. Based on different mechanisms, the entire propagation process is presented by four zones in the case of an independent crossing bridge (ICB) and two zones in the case of groups of crossing bridges. First, all the propagation characteristics, including extra propagation loss, shadow fading, small-scale fading, and fading depth, have been measured and extracted. The results are shown in a complete table for accurate statistical modeling. Then, two empirical models, i.e., ICB and crossing bridges group (CBG), are first established to describe the extra loss owing to the crossing bridges. The proposed models improve on the state-of-the-art models for this problem, achieving a root mean square error (RMSE) of 3.0 and 3.7 dB, respectively. View full abstract»

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  • Statistical Characterization of \kappa { - }\mu Shadowed Fading

    Page(s): 518 - 526
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB) |  | HTML iconHTML  

    This paper investigates a natural generalization of the κ - μ fading channel in which the line-of-sight (LOS) component is subject to shadowing. This fading distribution has a clear physical interpretation and good analytical properties and unifies the one-side Gaussian, Rayleigh, Nakagami- m, Rician, κ - μ, and Rician shadow fading distributions. The three basic statistical characterizations, i.e., probability density function (pdf), cumulative distribution function (cdf), and moment-generating function (mgf), of the κ - μ shadowed distribution are obtained in closed form. Then, it is also shown that the sum and maximum distributions of independent but arbitrarily distributed κ - μ shadowed variates can be expressed in closed form. This set of new statistical results is finally applied to modeling and analysis of several wireless communication systems, e.g., the proposed distribution has applications to land mobile satellite (LMS) communications and underwater acoustic communications (UAC). View full abstract»

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  • A Disturbance-Adaptive Design for VANET-Enabled Vehicle Platoon

    Page(s): 527 - 539
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1632 KB) |  | HTML iconHTML  

    In highway systems, grouping vehicles into platoons can improve road capacity and energy efficiency. With the advance of technologies, the performance of platoons can be further enhanced by vehicular ad hoc networks (VANETs). In the past few years, many studies have been conducted on the dynamics of a VANET-enabled platoon under traffic disturbance, which is a common scenario on a highway. However, most of them do not consider the impact of platoon dynamics on the behaviors of VANETs. Moreover, most existing studies focus on how to maintain the stability of a platoon and do not address how to mitigate negative effects of traffic disturbance, such as uncomfortable passenger experience, increased fuel consumption, and increased exhaust emission. In this paper, we will investigate the dynamics of the VANET-enabled platoon from an integrated perspective. In particular, we first propose a novel disturbance-adaptive platoon (DA-Platoon) architecture, in which a platoon controller shall adapt to the disturbance scenario and shall consider both VANET and platoon dynamics requirements. Based on a specific realization of the DA-Platoon architecture, we then analyze the traffic dynamics inside a platoon and derive desired parameters, including intraplatoon spacing and platoon size, so as to satisfy VANET constraints under traffic disturbance. To mitigate the adverse effects of traffic disturbance, we also design a novel driving strategy for the leading vehicle of a platoon, with which we can determine the desired interplatoon spacing. Finally, we conduct extensive simulation experiments, which not only validate our analysis but also demonstrate the effectiveness of the proposed driving strategy. View full abstract»

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  • A Sensor-Fusion Drivable-Region and Lane-Detection System for Autonomous Vehicle Navigation in Challenging Road Scenarios

    Page(s): 540 - 555
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2801 KB) |  | HTML iconHTML  

    Autonomous vehicle navigation is challenging since various types of road scenarios in real urban environments have to be considered, particularly when only perception sensors are used, without position information. This paper presents a novel real-time optimal-drivable-region and lane detection system for autonomous driving based on the fusion of light detection and ranging (LIDAR) and vision data. Our system uses a multisensory scheme to cover the most drivable areas in front of a vehicle. We propose a feature-level fusion method for the LIDAR and vision data and an optimal selection strategy for detecting the best drivable region. Then, a conditional lane detection algorithm is selectively executed depending on the automatic classification of the optimal drivable region. Our system successfully handles both structured and unstructured roads. The results of several experiments are provided to demonstrate the reliability, effectiveness, and robustness of the system. View full abstract»

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  • Comparison of Different Models and Simulation Approaches for the Energetic Study of a Subway

    Page(s): 556 - 565
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1600 KB) |  | HTML iconHTML  

    This paper compares different models and simulation approaches for an energetic simulation of an automatic subway. For this purpose, several models are carried out from a dynamic model, which is validated by comparison with experimental measurements. Furthermore, two different simulation approaches are compared, i.e., backward and forward approaches. A simplified model is obtained and allows the reduction of the simulation time by 96 compared with the dynamic model by keeping an accuracy value of more than 99%. View full abstract»

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  • Coordinated Control of Motor-Driven Power Steering Torque Overlay and Differential Braking for Emergency Driving Support

    Page(s): 566 - 579
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2495 KB) |  | HTML iconHTML  

    This paper describes a coordinated control of motor-driven power steering (MDPS) torque overlay and differential braking for emergency driving support (EDS). The coordinated control algorithm is designed to assist drivers to overcome hazardous situations. Electrically controllable MDPS and brake system are used as actuators, and a radar and a camera are used as a sensor system. Using environmental and vehicle information obtained from the sensor system, a risk of collision and driver's intention are determined, and a collision avoidance trajectory is generated, incorporating the driver's intention. Based on the generated collision avoidance trajectory, the MDPS overlay torque is determined to assist the driver's speed of response, and differential braking is determined to maximize the minimum vehicle-to-vehicle distance to avoid collision. The performance of the proposed algorithm has been investigated via computer simulations and real-time (RT) human-in-the-loop simulations. The simulation studies show that the controlled vehicle can secure additional vehicle-to-vehicle distance in severe lane change maneuvering for collision avoidance. The success rate of collision avoidance has been investigated for eight test drivers using the human-in-the-loop simulations. It has been shown that most of the test drivers can benefit from the proposed support system. View full abstract»

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  • Robust Sliding Mode-Based Learning Control for Steer-by-Wire Systems in Modern Vehicles

    Page(s): 580 - 590
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1925 KB) |  | HTML iconHTML  

    In this paper, a robust sliding mode learning control (SMLC) scheme is developed for steer-by-wire (SbW) systems. It is shown that an SbW system with uncertain system parameters and unknown external disturbance from the interactions between the tires and the variable road surface can be modeled as a second-order system. A sliding mode learning controller can then be designed to drive both the sliding variable and the tracking error between the steered front-wheel angle and the hand-wheel reference angle to asymptotically converge to zero. The proposed SMLC scheme exhibits many advantages over the existing schemes, including: 1) no information about vehicle parameter uncertainties and self-aligning torque variations is required for controller design; and 2) the control algorithm is capable of efficiently adjusting the closed-loop response based on the most recent history of the closed-loop stability and ensuring a robust steering performance. Both simulations and experiments are presented to show the excellent steering performance and the effectiveness of the proposed learning control methodology. View full abstract»

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  • Combined AFS and DYC Control of Four-Wheel-Independent-Drive Electric Vehicles over CAN Network with Time-Varying Delays

    Page(s): 591 - 602
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1703 KB) |  | HTML iconHTML  

    This paper deals with the lateral motion control of four-wheel-independent-drive electric vehicles (4WID-EVs) subject to onboard network-induced time delays. It is well known that the in-vehicle network and x-by-wire technologies have considerable advantages over the traditional point-to-point communication. However, on the other hand, these technologies would also induce the probability of time-varying delays, which would degrade control performance or even deteriorate the system. To enjoy the advantages and deal with in-vehicle network delays, an H-based delay-tolerant linear quadratic regulator (LQR) control method is proposed in this paper. The problem is described in the form of an augmented discrete-time model with uncertain elements determined by the delays. Delay uncertainties are expressed in the form of a polytope using Taylor series expansion. To achieve a good steady-state response, a generalized proportional-integral control approach is adopted. The feedback gains can be obtained by solving a sequence of linear matrix inequalities (LMIs). Cosimulations with Simulink and CarSim demonstrate the effectiveness of the proposed controller. Comparison with a conventional LQR controller is also carried out to illustrate the strength of explicitly dealing with in-vehicle network delays. View full abstract»

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  • Varying-Domain Optimal Management Strategy for Parallel Hybrid Electric Vehicles

    Page(s): 603 - 616
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2119 KB) |  | HTML iconHTML  

    In this paper, a management strategy is developed to realize the real-time optimal torque distribution between the internal combustion (IC) engine and the electric motor of parallel hybrid electric vehicles (HEVs). Without depending on future information, a set of instantaneous cost functions is defined as the objective of a multiobjective problem, which includes vehicle energy consumption, selected emission species, and an evaluation criterion for the battery state of charge (SOC). The varying-domain method is then utilized to introduce a flexible priority among objectives and to transform the multiobjective problem into a nonlinear programming problem, the optimal solution of which is subsequently found by a genetic algorithm, i.e., GENOCOPIII. A comparison of the simulation results demonstrates the flexibility of the proposed varying-domain optimal management strategy (VOMS) under different driving conditions. Compared with the rule-based management strategy (RBMS) and the weighted sum management strategy (WSMS), the VOMS potentially improves the fuel economy, emission reduction, and stability of the SOC. View full abstract»

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  • Mapping Optimization for a MAP Turbo Detector Over a Frequency-Selective Channel

    Page(s): 617 - 627
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1011 KB) |  | HTML iconHTML  

    In this paper, we consider a bit interleaved coded modulation (BICM) scheme over a frequency-selective channel. At the receiver, a turbo detector composed of a maximum a posteriori (MAP) detector and a MAP decoder is used. We propose to optimize the mapping choice in this context since it is well known that it has a significant impact on the performance of iterative receivers. We consider fixed and Rayleigh fading channels. Based on the Gaussian approximation, we give an analytical upper bound of the bit error probability (BEP) at the output of the detector for fixed channels. Then, we derive an approximate analytical expression of the BEP for both fixed and Rayleigh fading channels when the a priori information provided by the decoder is reliable, and then, most errors at the output of the detector are isolated. We find that the mapping minimizing this expression corresponds to a move away from the symbols differing by only one bit, unlike the Gray mapping. Since an exhaustive search to find this mapping is complicated for high-order modulations, we propose to use the binary switching algorithm (BSA) to approach the solution. Then, based on these results, we propose to adapt the mapping according to the signal-to-noise ratio (SNR) of the transmission. View full abstract»

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  • An Efficient Transmission Strategy for the Multicarrier Multiuser MIMO Downlink

    Page(s): 628 - 642
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1056 KB) |  | HTML iconHTML  

    A new transmission strategy that consists of a spatial scheduling algorithm and two precoding algorithms is developed for multicarrier multiuser (MU) multiple-input-multiple-output (MIMO) systems. The scheduling algorithm, which is called efficient multicarrier ProSched (EMC-ProSched), adopts a novel and effective scheduling metric for each user and can efficiently search for a suitable group of users to be served at the same time on the same frequency. Two precoding techniques are then designed to handle different antenna configurations. For the case where the number of transmit antennas at the base station (BS) is not smaller than the total number of receive antennas at the user terminals (UTs), the linear-precoding-based geometric mean decomposition (LP-GMD) algorithm is proposed. It suppresses the MU interference (MUI) and enables an effective implementation of the same modulation and coding scheme (MCS) on all spatial streams of each user. Consequently, smaller signaling overhead is required compared with the case where a different MCS is applied on each spatial stream. When the total number of receive antennas at the UTs exceeds the number of transmit antennas at the BS, we propose the low-complexity coordinated beamforming (LoCCoBF) algorithm to accomplish the goal of the MUI mitigation and to achieve a high capacity. A system-level simulator with a link-to-system interface is further developed under the framework of the IEEE 802.11ac standard to evaluate the performance of the proposed transmission strategy. The simulation results indicate that a promising performance can be achieved by employing the proposed transmission strategy. View full abstract»

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  • Experimental Evaluation of Layout Designs for 3  \times 3 MIMO-Enabled Radio-Over-Fiber Distributed Antenna Systems

    Page(s): 643 - 653
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1586 KB) |  | HTML iconHTML  

    This paper experimentally demonstrates that, for two representative indoor distributed antenna system (DAS) scenarios, existing radio-over-fiber (RoF) DAS installations can enhance the capacity advantages of broadband 3 × 3 multiple-input-multiple-output (MIMO) radio services without requiring additional fibers or multiplexing schemes. This is true for both single- and multiple-user cases with a single base station and multiple base stations. First, a theoretical example is used to illustrate that there is a negligible improvement in signal-to-noise ratio (SNR) when using a MIMO DAS with all N spatial streams replicated at N RAUs, compared with a MIMO DAS with only one of the N streams replicated at each RAU for N ≤ 4. It is then experimentally confirmed that a 3 × 3 MIMO DAS offers improved capacity and throughput compared with a 3 × 3 MIMO collocated antenna system (CAS) for the single-user case in two typical indoor DAS scenarios, i.e., one with significant line-of-sight (LOS) propagation and the other with entirely non-line-of-sight (NLOS) propagation. The improvement in capacity is 3.2% and 4.1%, respectively. Then, experimental channel measurements confirm that there is a negligible capacity increase in the 3 × 3 configuration with three spatial streams per antenna unit over the 3 × 3 configuration with a single spatial stream per antenna unit. The former layout is observed to provide an increase of ~ 1% in the median channel capacity in both the single- and multiple-user scenarios. With 20 users and three base stations, a MIMO DAS using the latter layout offers median aggregate capacities of 259 and 233 bit/s/Hz for the LOS and NLOS scenarios, respectively. It is concluded that DAS installations can further enhance the capacity offered to multiple users by multiple 3 × 3 MIMO-enabled base stations. Further, designing future DAS systems to support broadband 3 × 3 MIMO systems may not require sign- ficant upgrades to existing installations for small numbers of spatial streams. View full abstract»

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  • SER of Orthogonal Space–Time Block Codes Over Rician and Nakagami- m RF Backscattering Channels

    Page(s): 654 - 663
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1262 KB) |  | HTML iconHTML  

    The multiple-input-multiple-output (MIMO) radio-frequency (RF) identification system applies the RF backscattering principle, and its physical channel exhibits a special kind of cascaded structure different from conventional wireless channels and other cascaded channels (e.g., the keyhole MIMO channel). In this paper, we provide a general formulation to study orthogonal space-time block codes (OSTBCs) for RF backscattering with different fading assumptions and then analytically study the symbol-error-rate (SER) performances for this channel under Rician fading and Nakagami- m fading. We find that the diversity order achieves L for Rician fading and achieves Lmin(mf, Nmb) for Nakagami- m fading. Two receiving antennas (N = 2) can capture most of the receiving side gain regardless of the number of tag antennas L for Rician fading, and this is also applicable to Nakagami- m fading if the two links of the cascaded structure have similar channel conditions. More interestingly, we show that the performance of the this channel is more sensitive to the channel condition (the K factor or the m parameter) of the forward link than that of the backscattering link. View full abstract»

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  • A Lattice-Reduction-Aided Max-Log List Demapper for Coded MIMO Receivers

    Page(s): 664 - 673
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2461 KB) |  | HTML iconHTML  

    The max-log list demapper has been widely employed in the implementations of a coded multiple-input-multiple-output (MIMO) receiver, where only a candidate list of signal vectors is examined in the likelihood-ratio calculation to reduce complexity. Traditionally, the candidate list is generated in the original-lattice domain, which, unfortunately, results in severe degradation in the performance of the demapper if the channel is in ill-condition. In this paper, two new lattice-reduction-aided max-log list demappers are proposed, i.e., one for an iterative receiver and the other for a noniterative receiver. With similar complexity, the proposed demappers provide significant gains over existing demappers, particularly for the cases with a small list size and/or under a spatially correlated channel, due to the new algorithms for the generation of the candidate list. In addition, for the iterative receiver, the prior information coming out of the decoder is exploited to lower the complexity of the demapper. View full abstract»

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  • Scheduling and Network Coding for Relay-Aided Wireless Broadcast: Optimality and Heuristic

    Page(s): 674 - 687
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1848 KB) |  | HTML iconHTML  

    This paper considers the problems of minimizing the completion time and reducing decoding complexity for relay-aided wireless broadcast. Both network coding and scheduling problems are considered. A deterministic network coding algorithm is designed to select innovative encoding vectors, which is applicable to both the base station and the relay. The proposed algorithm can reduce decoding complexity significantly by selecting sparse encoding vectors. Integrating with the proposed network coding algorithm, a scheduling scheme based on dynamic programming is proposed, which is proved to be optimal in terms of minimizing expected completion time. Considering the size of state space and computational complexity of dynamic programming, a greedy scheduling algorithm is also proposed for practical implementation. Simulation shows that the proposed network coding algorithm and scheduling schemes work very well both in reducing completion time and in decoding complexity. View full abstract»

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  • Spatial Spectrum Sharing for Heterogeneous SIMO Networks

    Page(s): 688 - 702
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    In wireless networks for spectrum sharing among heterogeneous nodes, an issue of significant interest is the interference among coexisting systems, and understanding the essential quantities, such as interference distribution, is fundamental to the design of spatial spectrum sharing methods. This paper analyzes the performance of heterogeneously characterized nodes and investigates efficient spectrum sharing methods for single-input-multiple-output (SIMO) networks where nodes with different capabilities and requirements are spatially distributed according to homogeneous Poisson point processes (PPPs). Transmit power control strategies, such as fixed transmit power control and distance-based transmit power control, are applied, and it is demonstrated that their effects on the system performances depend on the multiple-antenna receiving methods. Furthermore, the underlay and overlay methods are considered for use as spectrum sharing methods. In addition, it is demonstrated that careful resource balancing among heterogeneous nodes contributes to minimizing the total amount of wireless resources required to meet the target outage constraints for all nodes, and the two spectrum sharing methods have the same performance in heterogeneous SIMO networks with low node densities. View full abstract»

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  • Efficient Beamforming Training for 60-GHz Millimeter-Wave Communications: A Novel Numerical Optimization Framework

    Page(s): 703 - 717
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1234 KB) |  | HTML iconHTML  

    In this paper, we formulate realistic beamforming (BF) training (or beam steering) in the emerging 60-GHz millimeter-wave communications as a numerical optimization problem. To maximize the receiving SNR, it aims to identify the optimal beam pair from a prescribed codebook using as little overhead as possible. Being a promising numerical method that excludes a functional derivative, the Rosenbrock numerical search may be of great significance to such applications. Nevertheless, for the encountered nonsmooth objective function, a search failure is inevitable due to the local optimum. To meet this challenge, we further present an appealing global numerical algorithm inspired by simulated annealing (SA) mechanics. In sharp contrast to classical schemes, numerical probes that lead to reward improvement are always accepted, and search moves toward worse solutions are also permitted, with a probability associated with an external temperature parameter. By relying on a newly designed two-level annealing schedule, the temperature decreases; thereby, permitting movements to worse solutions is progressively restricted. Consequently, it can basically escape from the local optimum. We then apply this new numerical search to beam switching of 60-GHz communications. Experimental simulations have demonstrated that the developed beam-switching scheme can efficiently discover the optimal beam pair by considerably reducing protocol overhead and energy consumption. View full abstract»

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  • Low-Complexity ICI Suppression Methods Utilizing Cyclic Prefix for OFDM Systems in High-Mobility Fading Channels

    Page(s): 718 - 730
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1166 KB) |  | HTML iconHTML  

    This paper focuses on a simple intercarrier interference (ICI) suppression scheme that linearly combines the intersymbol interference (ISI)-free part of a cyclic prefix (CP) and its corresponding part in an orthogonal frequency-division multiplexing (OFDM) signal to soothe the ICI effect caused by a time-varying channel. In contrast with existing heuristic combining weights in the literature for ICI suppression, we derived three sets of optimum combining weights in different aspects. Through simulations, we show that the proposed combining weights outperform other existing heuristic combining weights. In addition, a simplified implementation is introduced to reduce the computational complexity of combining. Furthermore, the proposed methods can be incorporated with other ICI mitigation methods to further improve the system performance. View full abstract»

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  • On Noisy ARQ in Block-Fading Channels

    Page(s): 731 - 746
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1976 KB) |  | HTML iconHTML  

    Assuming noisy feedback channels, this paper investigates the data transmission efficiency and robustness of different automatic repeat request (ARQ) schemes using adaptive power allocation. Considering different block-fading channel assumptions, the long-term throughput, the delay-limited throughput, the outage probability, and the feedback load of different ARQ protocols are studied. A closed-form expression for the power-limited throughput optimization problem is obtained, which is valid for different ARQ protocols and feedback channel conditions. Furthermore, the paper presents numerical investigations on the robustness of different ARQ protocols to feedback errors. It is shown that many analytical assertions about the ARQ protocols are valid both when the channel remains fixed during all retransmission rounds and when it (in)dependently changes in each round. As demonstrated, optimal power allocation is crucial for the performance of noisy ARQ schemes when the goal is to minimize the outage probability. View full abstract»

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  • Adaptive Interference-Aware Multichannel Assignment for Shared Overloaded Small-Cell Access Points Under Limited Feedback

    Page(s): 747 - 762
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1656 KB) |  | HTML iconHTML  

    This paper proposes a reduced-complexity multichannel assignment scheme for short-range cellular systems. It treats the scenario when a number of small-cell (e.g., femtocell) access points (APs) can be shared to serve active scheduled users. The APs employ isotropic antenna arrays and operate using an open-access control strategy. To improve the reuse ratio of physical resources, the APs are assumed to occupy a single physical channel, wherein coordination among them is infeasible. On the other hand, to improve the spatial coverage, a scheduled user can be served by a single transmit channel from an AP at a time. For the case of overloaded APs and when the feedback links are capacity limited, the scheme attempts to identify the suitable transmit channels from the deployed APs in an adaptive manner such that certain performance and/or processing load limits are satisfied. The effects of some system and design parameters on the outcomes of the scheme are thoroughly discussed. Novel results for the statistics of the resulting interference power are presented, from which results for some performance measures and processing loads are obtained. Numerical and simulations results are provided to clarify the achieved gains, as compared with related models under different operating conditions. View full abstract»

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  • Analysis and Design of Distributed Antenna-Aided Twin-Layer Femto- and Macrocell Networks Relying on Fractional Frequency Reuse

    Page(s): 763 - 774
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1037 KB) |  | HTML iconHTML  

    Distributed antenna systems (DASs) and FemtoCells (FCs) are capable of improving the attainable performance in the cell-edge area and in indoor residential areas, respectively. To achieve high spectral efficiency (SE), both the distributed antenna elements (DAEs) and FC base stations (FBSs) may have to reuse the spectrum of the macrocellular network. As a result, the performance of both outdoor MacroCell (MC) users (OMU) and indoor FC users (IFUs) suffers from CoChannel Interference (CCI). Hence, in this paper, heterogenous cellular networks are investigated, where the DAS-aided MCs and FCs coexist within the same area. Both the outage probability (OP) and the spatially averaged throughput are derived, and the network is optimized either to minimize the OP or to maximize the MC's throughput. Our analysis demonstrates that surprisingly, the unity frequency-reuse (UFR)-based macrocellular system can be optimized in isolation, without considering the impact of FCs. We found that the MCs relying on fractional frequency reuse (FFR) tend to be converted to several small cells, illuminated by the DAEs, when the density of FCs becomes high. View full abstract»

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  • Denoise-and-Forward Network Coding for Two-Way Relay MIMO Systems

    Page(s): 775 - 788
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1495 KB) |  | HTML iconHTML  

    In this paper, we propose a denoise-and-forward network coding (DNF-NC) transmission scheme for its applications in two-way relay multiple-input and multiple-output (MIMO) systems. We first consider a scenario with a single pair of source nodes, and minimum mean square error (MMSE) receiver is applied at each node. The global optimal precoding design based on the mean square error (MSE) criterion can be achieved by solving two independent convex optimization problems. To achieve a better tradeoff between performance and complexity, an alternative power optimization approach is proposed using a channel diagonalization technique. Then, we proceed to considering a more challenging bidirectional communication scenario with multiple pairs of source nodes. With intrapair coordination at the sources, we modify DNF-NC by employing a signal alignment technique to combat interpair interference. The numerical results demonstrate that the proposed DNF-NC schemes can significantly improve bit error rate (BER) performance in both two scenarios, and such performance gains can be achieved with relatively low computational complexity. View full abstract»

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  • Distributed Cooperative Topology Control for WANETs With Opportunistic Interference Cancelation

    Page(s): 789 - 801
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB) |  | HTML iconHTML  

    Cooperative communications has received tremendous interests in wireless systems. The communication performance of a single source-destination pair can be enhanced via the help of relays in traditional cooperative communications. Recent advances in interference cancelation (IC) can further enhance the performance of parallel cooperative transmissions between multiple source-destination pairs. Although some works have been done on cooperative communications, most existing works are focused on link-level physical-layer issues. Consequently, the potential benefits of cooperative communications on network-level upper layer issues, such as topology control, are largely ignored in existing works. In this paper, we study the impacts of cooperative communications, particularly IC-based cooperative communications, on topology control in wireless ad hoc networks (WANETs). We propose a distributed cooperative topology control scheme with opportunistic IC (COIC) to improve network capacity in WANETs by jointly considering both upper layer network capacity and physical-layer cooperative communications with IC. We show that the benefits brought by cooperative communications are opportunistic, which rely on network structures and channel conditions. These opportunistic advantages have significant impacts on network capacity, and our proposed COIC can effectively capture these opportunities to substantially improve network capacity. 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