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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Spectrum Sensing for Cognitive OFDM Over Line-of-Sight Doubly Selective Fading Channels</title>
      <link>https://trid.trb.org/View/1647458</link>
      <description><![CDATA[Spectrum sensing for fast-moving vehicles in cognitive radios over a general line-of-sight (LOS) doubly selective fading channel, which is a practical environment for modern mobile orthogonal frequency-division multiplexing communications, should be addressed. However, time- and frequency-selectivity inherent in radio channels is a limiting factor for the detection performance. By discovering the complement property of correlation profile (introduced by the multipath delay spread) and adopting the proposed estimation for the correlation function of LOS channels (introduced by the mobility), the decision metric can be transformed to the ideal one without time- and frequency-selectivity. As such, the detection performance can be greatly enhanced by the proposed technique without needing any channel equalization techniques on received signals.]]></description>
      <pubDate>Mon, 16 Sep 2019 17:19:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1647458</guid>
    </item>
    <item>
      <title>Resource Allocation for High-Reliability Low-Latency Vehicular Communications With Packet Retransmission</title>
      <link>https://trid.trb.org/View/1640623</link>
      <description><![CDATA[In vehicular communications, safety-critical information exchange has stringent reliability and latency requirements. However, lack of accurate instantaneous channel state information due to high mobility poses a great challenge to meet these requirements and the situation gets more complicated when packet retransmission is considered. Based on only large-scale fading channel information, the authors perform spectrum and power allocation to maximize the sum ergodic capacity of vehicular-to-infrastructure (V2I) links, while guaranteeing reliability and latency requirements of vehicular-to-vehicular (V2V) links. First, for each possible V2I–V2V spectrum reusing pair, the authors analyze the queueing system for the V2V link and derive the packet loss probability and average packet sojourn time under fixed power allocation. Then, an optimal power allocation is derived for each possible pair. Afterwards, the authors optimize the spectrum reusing pattern by addressing a polynomial time solvable bipartite matching problem. Simulation results confirm the accuracy of the proposed queueing analysis. Moreover, the proposed resource allocation strategy can improve the ergodic capacity of the V2I links under the precondition of guaranteeing the V2V links’ requirements on reliability and latency.]]></description>
      <pubDate>Fri, 30 Aug 2019 13:01:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/1640623</guid>
    </item>
    <item>
      <title>Cooperative vehicular communications at intersections over Nakagami-m fading channels</title>
      <link>https://trid.trb.org/View/1637757</link>
      <description><![CDATA[In this paper, the authors study vehicular communications (VCs) at road intersections. They investigate three transmission schemes: direct transmissions (DT), relay transmissions (RT) and hybrid transmissions (HT), in the presence of interference. They model the interferer vehicle locations as a Poisson point process. Using tools from stochastic geometry, they compute the outage probability for the three transmission schemes considering Nakagami-m fading channels. They consider line of sight (LOS) scenarios and non-line of sigh (NLOS) scenarios. They derive the outage probability when the receivers are on the roads (as a vehicle), or outside the roads (as an infrastructure). The authors show that RT is useful only when DT is not possible. They also show that, in LOS scenario, DT is better for high densities of vehicles. They show that HT has better performance for low densities of vehicles and low data rates regardless of the scenario considered. Surprisingly, they find that NLOS scenarios outperform LOS scenarios at intersections. Finally, the authors show that the best relay position in RT is at mid-distance between the source and the destination whereas the best relay in HT is close to the destination. Analytical results are validated by Monte-Carlo simulations.]]></description>
      <pubDate>Mon, 26 Aug 2019 10:30:46 GMT</pubDate>
      <guid>https://trid.trb.org/View/1637757</guid>
    </item>
    <item>
      <title>Multi-Hop D2D Communications With Network Coding: From a Performance Perspective</title>
      <link>https://trid.trb.org/View/1594477</link>
      <description><![CDATA[Multi-hop device-to-device (D2D) communications play an important role in expanding D2D coverage. In this paper, we study a relay-based and network-coding-assisted (in particular, XOR coding) multi-hop D2D communication system. In the system, toward jointly considering the impact of interference and network traffic conditions on the quality of D2D communications, various channel fading models and traffic models are investigated, and the packet loss probability of D2D links is meticulously computed using these models. With the packet loss probability of D2D links, the general closed-form expressions of end-to-end packet loss probability (E2EPLP) of the system with the presence (or absence) of XOR coding are subsequently derived. Our experiments reveal that both the number of relays and the mechanism of XOR coding can affect the system performance. Specifically, the increase in the number of relays will lower the overall system performance (e.g., an increase in the E2EPLP and end-to-end completion time, and a decrease of the end-to-end rate may follow as a result). On the other hand, although the presence of XOR coding unfortunately raises the system E2EPLP, it can effectively improve the end-to-end completion time and end-to-end rate. It is our belief that the analytical approach proposed in this paper and the results found in our work can be useful to peer studies in the context of applying network coding in multi-hop D2D networks.]]></description>
      <pubDate>Tue, 28 May 2019 16:50:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1594477</guid>
    </item>
    <item>
      <title>Real-Time Geometry-Based Wireless Channel Emulation</title>
      <link>https://trid.trb.org/View/1587071</link>
      <description><![CDATA[Connected autonomous vehicles and industry 4.0 production scenarios require ultrareliable low-latency communication links. The varying positions of transmitter, reflecting objects, and receiver cause a nonstationary time- and frequency-selective fading process. In this paper, the authors present the necessary hardware architecture and signal processing algorithms for a real-time geometry-based channel emulator, that is needed for testing of wireless control systems. The authors partition the nonstationary fading process into a sequence of local stationarity regions and model the channel impulse response as sum of propagation paths with time-varying attenuation, delay, and Doppler shift. The authors implement a subspace projection of the propagation path parameters, to compress the time-variant channel impulse response. This enables a low data-rate link from the host computer, which computes the geometry-based propagation paths, to the software defined radio unit, that implements the convolution on a field programmable gate array (FPGA). With the authors' new architecture, the complexity of the FPGA implementation becomes independent of the number of propagation paths. The authors' channel emulator can be parametrized by all known channel models. Without loss of generality, the authors use a parameterization by a geometry-based stochastic channel model, due to its nonstationary nature. The authors provide channel impulse response measurements of the channel emulator, using the RUSK Lund channel sounder for a vehicular scenario with 617 propagation paths. A comparison of the time-variant power delay profile and Doppler spectral density of simulated and emulated channel impulse response showed a close match with an error smaller than -35 dB. The results demonstrate that the authors' channel emulator is able to accurately emulate nonstationary fading channels with continuously changing path delays and Doppler shifts.]]></description>
      <pubDate>Thu, 28 Feb 2019 09:39:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1587071</guid>
    </item>
    <item>
      <title>Exploiting Shadowing Stationarity for Antenna Selection in V2V Communications</title>
      <link>https://trid.trb.org/View/1587070</link>
      <description><![CDATA[Antenna selection (AS) techniques are considered as ideal candidates for vehicle-to-vehicle communications, since they improve system's performance and simultaneously satisfy the hardware and signal processing constraints that exist in these systems. However, the achieved gain over single antenna links is affected by the fast varying wireless channel, since AS is frequently performed using outdated versions of the signal-to-noise ratio (SNR). In this paper, the authors propose an AS technique that exploits the stationarity of large-scale fading. In this context, by employing shadowing information as an AS criterion, the negative consequences of the outdated channel state information (CSI) can be alleviated, since large-scale fading varies more slowly than small-scale fading. The performance of the proposed technique is analyzed using the criteria of outage probability and average output SNR. It is shown that the proposed scheme outperforms the corresponding one that is based on outdated CSI, especially in scenarios with mild fading/shadowing channel conditions. Moreover, the influence of correlated shadowing on the system's performance has been also analytically investigated. The main results have been also verified by empirical data based on measurement campaigns in non-stationary communication conditions.]]></description>
      <pubDate>Thu, 28 Feb 2019 09:39:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1587070</guid>
    </item>
    <item>
      <title>Noncoherent MIMO Signaling for Block-Fading Channels: Approaches and Challenges</title>
      <link>https://trid.trb.org/View/1584345</link>
      <description><![CDATA[The majority of existing wireless communication systems relies on training-based signaling, i.e., schemes that rely on accurate channel estimates for detecting the transmitted symbols. Training requires its own hardware and algorithms and consumes a significant portion of the channel coherence interval, which is typically short in vehicular communications. The drawbacks of training can be alleviated by using noncoherent signaling schemes, which dispense with the training phase altogether. The authors will focus on a particular class of such schemes, i.e., Grassmannian signaling. This scheme is optimal for high signal-to-noise ratio (SNR) communication over noncoherent block-fading channels, which are likely to arise in many future networks.]]></description>
      <pubDate>Mon, 25 Feb 2019 11:47:46 GMT</pubDate>
      <guid>https://trid.trb.org/View/1584345</guid>
    </item>
    <item>
      <title>Fading Modeling in Maritime Container Terminal Environments</title>
      <link>https://trid.trb.org/View/1564276</link>
      <description><![CDATA[In this paper, an analytical model for slow and fast fading effects in maritime container terminals is derived, from fitting distributions to the results of measurements performed in an actual operational environment. The proposed model is composed of a set of equations, enabling to evaluate fading statistical distribution parameters for different system and environments conditions, as a function of frequency, base station antenna height, and average height of container stacks in a deepwater container terminal. The model's coefficients were obtained from a multivariate linear regression of the fitted distributions parameters, allowing to evaluate the different statistical distribution parameters with a negligible mean error and a standard deviation of the error less than 0.65 dB. It is observed that a good fitting is obtained for slow fading with the Lognormal Distribution, the standard deviation ranging in [1.40, 4.81] dB, while fast fading is well modeled by the Nakagami Distribution with the standard deviation ranging in [0.43, 1.26]. Hence, in a conservative perspective, values of 5 and 1.3 dB are proposed to characterize slow and fast fading, respectively.]]></description>
      <pubDate>Tue, 20 Nov 2018 10:17:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1564276</guid>
    </item>
    <item>
      <title>Cooperative Relaying Using Space-Time Block Coded Non-orthogonal Multiple Access</title>
      <link>https://trid.trb.org/View/1475283</link>
      <description><![CDATA[Non-orthogonal multiple access (NOMA) has attracted significant attention in the research community as a potential radio access technology for future wireless networks. In this work, the authors propose a two-phase cooperative decode-and-forward (DF) relaying scheme based on Alamouti (2 x 1 multiple-input single-output mode) space-time block-coded non-orthogonal multiple access (STBC-NOMA). Closed-form solutions for ergodic sum capacity and outage probability of the proposed scheme are analyzed over independent Rayleigh fading channels. Asymptotic approximations for ergodic sum capacity, outage probability, and outage sum capacity at the high signal-to-noise ratio regime are also provided. It has been pointed out that the proposed cooperative relaying system (CRS) using STBC-NOMA can attain significant performance gains compared to the conventional CRS using NOMA and the traditional DF relaying schemes. It is also demonstrated that the relay position between the transmitter and the receiver has a significant impact on the performance of the proposed protocol. In addition, the proximity between analytical and simulation results confirms the efficiency of the proposed protocol.]]></description>
      <pubDate>Fri, 22 Sep 2017 16:45:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/1475283</guid>
    </item>
    <item>
      <title>An Adaptive State Assignment Mechanism Based on Joint Data Detection and Channel Estimation on Fading Meteor Channel</title>
      <link>https://trid.trb.org/View/1471744</link>
      <description><![CDATA[Integrating adaptive modulation and coding techniques into time-varying meteor burst channels with joint data detection and channel estimation at the receiver can greatly increase the average throughput of a meteor burst communication system (MBCS). Although the per-survivor processing algorithm (PSPA) based on joint data and channel estimation provides superior performance and robustness for MBCS, it is very difficult to implement it into practice due to the extremely high computational complexity. An adaptive state reduction scheme using a dimension-down PSPA (ADPSP) with few states in the trellis diagram is proposed based on the slow-fading characteristic of the meteor burst channel. It has the advantages of the dimension-down PSPA (D-PSPA) and the adaptive state reduction scheme based on PSPA proposed in the authors' previous work. The scheme is proposed to reduce the computation complexity and memory size for exponentially decaying meteor burst channels and make the maximum likelihood sequence detection available for adaptive data transmission. Based on the estimation of parameters of the meteor burst channel, the adaptive threshold is obtained in order to decrease the computation complexity of PSPA, where the states close to the correct one in the trellis is selected. Simulation results are presented to validate the theoretical analysis. It is shown that the proposed adaptive state reduction scheme using a D-PSPA can obtain a good tradeoff between the achievable performance and its dynamically computation complexity, as well as provide reliable data transmission for MBCS using adaptive coding and modulation.]]></description>
      <pubDate>Tue, 29 Aug 2017 11:58:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1471744</guid>
    </item>
    <item>
      <title>On the Scaling Behavior of the Average Rate Performance of Large-Scale Distributed MIMO Systems</title>
      <link>https://trid.trb.org/View/1467410</link>
      <description><![CDATA[Multiple-input-multiple-output (MIMO) technology offers the potential for supporting increasingly large-scale data traffic on cellular networks. The author of this paper analyze the performance of the average rate of data traffic in the downlink channel of a large system of distributed base-station antennas, with and without channel state information at the transmitter. Using simulation, the author analyze the effectiveness of various sizes of antenna clusters. Their results show that the highest performance can be achieved by a fully distributed array of base-station antennas.]]></description>
      <pubDate>Fri, 28 Jul 2017 13:00:02 GMT</pubDate>
      <guid>https://trid.trb.org/View/1467410</guid>
    </item>
    <item>
      <title>Jointly Optimized Reed–Muller Codes for Multilevel Multirelay Coded-Cooperative VANETS</title>
      <link>https://trid.trb.org/View/1467409</link>
      <description><![CDATA[In this paper, the authors present the well-known Reed–Muller (RM) codes for multilevel multirelay vehicular adhoc networks, which can enjoy coded-cooperation among network nodes. At first, the authors present the code construction principles for a single node/relay scenario and then extend the design principles to the two-level two-relay and, finally, to multilevel multirelay scenarios. The term “level” refers to the fact that different order RM code is used at each relaying node. Plotkin's construction is exploited to utilize RM codes in such coded-cooperative schemes. To achieve an optimum code at the destination node, proper encoding strategy needs to be employed at the relay node. Therefore, the authors propose a design criteria and an efficient algorithm for proper bit selection at the relay nodes to achieve the best possible code at the destination. It is observed that the increase in the number of levels as well as relays result in better channel code at the destination, as compared to the lesser number of relays, however, at the cost of increased decoding complexity. The channels considered to analyze the bit error rate (BER) performances of proposed coded-cooperative schemes are fast and slow Rayleigh fading channels. At the destination, soft decision maximum likelihood decoding is employed. Numerical simulations show that the single-relay RM coded-cooperative scheme provides significant BER performance gains over the noncooperative and state-of-the-art distributed turbo coded-cooperative schemes under identical conditions.]]></description>
      <pubDate>Fri, 23 Jun 2017 11:40:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1467409</guid>
    </item>
    <item>
      <title>Cognitive Coded Cooperation in Underlay Spectrum-Sharing Networks under Interference Power Constraints</title>
      <link>https://trid.trb.org/View/1459852</link>
      <description><![CDATA[Since the radio-frequency spectrum is fast becoming scarce, increasing the spectral utilization is of utmost importance for the sustainable development of wireless communications systems. In an effort to improve the spectral efficiency, cooperative relaying techniques have recently been integrated into spectrum-sharing environments. In this paper, the authors examine the outage and bit error probabilities of dual-hop cognitive turbo-coded cooperative networks with outdated channel state information (CSI) subject to Rayleigh fading. The authors assume a spectrum-sharing environment where the transmit power conditions of the underlay network are governed by the combined power constraint of the interference in the primary network and the maximum allowable transmission power at the secondary network. In this network, cochannel interference from the primary transmitter on the secondary network is considered, and a single relay that maximizes the received signal-to-noise ratio (SNR) is selected among the secondary relays. To efficiently evaluate the key parameters on the system performance, the authors derive the analytical expressions of the end-to-end outage probability and bit error rate (BER) for the proposed scheme. Assuming binary phase-shift keying (BPSK), the authors obtain explicit upper bounds on the probability of bit error based on the pairwise error probability. Furthermore, the authors present simplified expressions of the outage probability in the high-SNR regime used to quantify the system performance in terms of diversity gain. Finally, simulation results are provided to verify the accuracy of the authors analytical framework.]]></description>
      <pubDate>Fri, 28 Apr 2017 10:44:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1459852</guid>
    </item>
    <item>
      <title>Air–Ground Channel Characterization for Unmanned Aircraft Systems Part II: Hilly and Mountainous Settings</title>
      <link>https://trid.trb.org/View/1459836</link>
      <description><![CDATA[The use of unmanned aircraft systems (UAS) is expanding rapidly. For safe and reliable integration of UAS into the National Airspace System (NAS), control and nonpayload communication (CNPC) system requirements are being developed. The air-to-ground (AG) channel characteristics essentially determine CNPC link performance. The National Aeronautics and Space Administration (NASA) Glenn Research Center has sponsored a comprehensive AG channel measurement campaign in 2013 in both the Land C-bands recently allocated for UAS. These measurements covered nearly all typical ground site (GS) local environments, including over water, hilly, mountainous, suburb, and near urban. As a continuation of results reported for the over-water scenarios, a description of the measurement campaign, measured results, and complete AG channel models for hilly and mountainous terrains are provided in this paper. The path loss is modeled by a modified log-distance path loss model with a correction for flight direction; path loss results are close to those of free space. A strong ground reflection was observed only for some small portions of some of the flight paths. The small-scale fading is well modeled by the Ricean distribution with a K-factor of 29.4 dB in the C-band and 12.8 dB in the L-band. The interband signals are uncorrelated. The spatial correlation for the two intraband channels with an aircraft antenna separation of 1.8 m is greater than 0.85. The C-band root-mean-square delay spread (RMS-DS) is 10 ns most of the time, with a maximum of 1 μs in hilly terrain and 180 ns in mountainous terrain. Tapped delay line (TDL) models accounting for the line of sight (LOS) and up to seven intermittent multipath components (MPCs) were developed, including the MPCs' probability of occurrence, relative power, phase, duration, and excess delay.]]></description>
      <pubDate>Fri, 28 Apr 2017 10:44:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/1459836</guid>
    </item>
    <item>
      <title>LORA: Loss Differentiation Rate Adaptation Scheme for Vehicle-to-Vehicle Safety Communications</title>
      <link>https://trid.trb.org/View/1459881</link>
      <description><![CDATA[The existing study shows that safety applications supported by vehicle-to-vehicle (V2V) communications have the potential to address 80% of all road crash issues. IEEE 802.11p is a key enabling technology to support V2V safety applications. To meet the stringent delay and reliability requirements of these applications, rate adaptation (RA) approaches have been proposed to determine the optimal data transmission rate, according to the channel conditions such as packet losses. However, existing RA solutions cannot be directly applied to V2V safety communications in highway scenarios, which exhibit lots of dynamics and severe packet losses. Moreover, physical (PHY)-layer channel fading and medium-access-control (MAC)-layer interference contribute differently to the packet losses and, thus, should be treated separately. To address these issues, in this paper, the authors propose a LOss differentiation RA (LORA) scheme. LORA can estimate the average packet loss rate (PLR) for each sender and differentiate the fading losses from the interference losses. Extensive evaluation results demonstrate that LORA can provide reliability guarantees for V2V safety applications, as well as a response to environment changes in a real-time manner.]]></description>
      <pubDate>Fri, 28 Apr 2017 10:44:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1459881</guid>
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