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    <title>Transport Research International Documentation (TRID)</title>
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    <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>
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      <title>Transport Research International Documentation (TRID)</title>
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    <item>
      <title>Anomalies in NAVTEX Signal Reception in the Northern Adriatic: Discrepancies between Measurements and Propagation Models</title>
      <link>https://trid.trb.org/View/2696040</link>
      <description><![CDATA[This research analyzes in detail the reception of NAVTEX signals in the northern Adriatic, revealing significant discrepancies between empirical observations and predictions of standard groundwave propagation models. The NAVTEX receiver at a fixed location on shore consistently failed to receive NAVTEX messages during daytime broadcasts from the Split and Piombino stations, despite being within their coverage area. At the same time, signals and messages from the nearest Mondolfo station were reliably received. Signal strength measurements confirmed that the signals from Split and Piombino stations were weak and unstable, while Mondolfo station provided a strong and stable signal. Comparison of these observations with the predictions of propagation models showed that the models predict signal strengths which should be sufficient for detection from all stations, including Split and Piombino. These findings indicate that current propagation models fail to accurately capture complex environmental factors or potential transmitter performance issues. It is concluded that these models cannot be reliably used to predict NAVTEX coverage in such complex maritime environments, which has critical implications for maritime safety due to the inability to receive Maritime Safety Information (MSI) via the NAVTEX system.]]></description>
      <pubDate>Mon, 27 Apr 2026 14:58:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/2696040</guid>
    </item>
    <item>
      <title>Physics-Based Trajectory Design for Cellular-Connected UAV in Rainy Environments Based on Deep Reinforcement Learning</title>
      <link>https://trid.trb.org/View/2591180</link>
      <description><![CDATA[Cellular-connected uncrewed aerial vehicles (UAVs) have gained increasing attention due to the potential to leverage existing cellular infrastructure for reliable communications between UAVs and base stations. They have been used for various applications, including weather forecasting and search and rescue operations. However, under extreme weather conditions such as rainfall, the trajectory design of cellular UAVs is quite challenging due to weak coverage regions in the sky, limitations of UAV flying time, and signal attenuation caused by raindrops. To this end, this paper proposes a physics-based trajectory design approach for cellular-connected UAVs in rainy environments. A physics-based electromagnetic simulator is utilized to take into account detailed environment information and the impact of rain on radio wave propagation. The trajectory optimization problem is formulated to jointly consider UAV flying time and signal-to-interference ratio, and is solved through a Markov decision process using deep reinforcement learning algorithms based on multi-step learning and double Q-learning. Optimal UAV trajectories are compared in examples with homogeneous atmosphere medium and rain medium. Additionally, a thorough study of varying weather conditions on trajectory design is provided, and the impact of weight coefficients in the UAV trajectory design is discussed. The proposed approach has demonstrated great potential for UAV trajectory design under rainy weather conditions.]]></description>
      <pubDate>Fri, 20 Mar 2026 14:10:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2591180</guid>
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    <item>
      <title>Reconfigurable Intelligent Surfaces in Factory Environments: Channel Modeling and Use-Case Analysis</title>
      <link>https://trid.trb.org/View/2601442</link>
      <description><![CDATA[Reconfigurable intelligent surface (RIS) is a breakthrough technology in wireless communications, enabling dynamic control over the propagation environment to enhance signal quality and spectral efficiency. This article introduces a ray-tracing (RT) approach for simulating the impact of RIS technology in realistic scenarios. The fundamental aspects of the RIS model are validated against published measurements. The key novelty is the integration of the validated radar cross-section based RIS model into an RT tool and ensuring compatibility with any propagation range, allowing antennas to be positioned in either near-field (NF) or far-field (FF) conditions relative to the RIS. The model also uniquely addresses practical aspects, such as phase quantization (PQ) and wide-band response, essential for assessing RIS deployments in real-world mobile applications. This article evaluates RIS-assisted coverage enhancement for private industrial networks by applying RT to a complex factory scenario and conducting system-level simulations at 3.7 GHz and 27 GHz. The results underscore RIS’s ability to significantly extend coverage and improve link performance in challenging propagation conditions.]]></description>
      <pubDate>Mon, 22 Dec 2025 16:07:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2601442</guid>
    </item>
    <item>
      <title>Simulation-based evaluation of indoor positioning systems in connected aircraft cabins</title>
      <link>https://trid.trb.org/View/2459154</link>
      <description><![CDATA[With regard to the demanding aircraft cabin environment, this paper delves into the rising use of location-aware radio communication systems to streamline operational processes. The authors propose a hybrid deterministic and stochastic simulation approach, incorporating model-based ray-tracing and empirical residual simulation. The methodology presented allows for the evaluation of localization methods based on geometric relations, serving as both a data generation and validation tool. The authors elaborate how different radio properties and propagation phenomena influence these geometric relations and the localization process. This paper includes a publicly available dataset derived from the simulation approach, facilitating transparency and further analysis in the field of aircraft cabin radio localization systems.]]></description>
      <pubDate>Mon, 27 Jan 2025 15:39:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2459154</guid>
    </item>
    <item>
      <title>Two-Slope Path Loss Model for Curved-Tunnel Environment With Concept of Break Point</title>
      <link>https://trid.trb.org/View/1895355</link>
      <description><![CDATA[The curvature of tunnels introduces an extra loss in the wave propagation. A simulation and measurement study are performed on the straight and the curved tunnels to investigate the extra loss in the curved tunnels in comparison with the straight tunnels at a frequency of 2.4 GHz. This study suggests the existence of two wave propagation mechanisms in the curved tunnel; enhanced waveguiding mechanism induced by rich multipath components from the curved tunnels and degraded waveguiding mechanism due to the blockage from the curved tunnel walls. For efficient radio planning, a new propagation model with curvature dependent break point is proposed. The proposed break point indicates the end of the enhanced waveguiding mechanism and the beginning of the degraded waveguiding mechanism. A two-slope radio wave propagation model is then proposed for radio communications inside curved tunnels by using the determined break point, with performance evaluation.]]></description>
      <pubDate>Mon, 25 Apr 2022 10:06:46 GMT</pubDate>
      <guid>https://trid.trb.org/View/1895355</guid>
    </item>
    <item>
      <title>Long Distance Wireless Radio Frequency Link for the ITS Statewide Network</title>
      <link>https://trid.trb.org/View/1870551</link>
      <description><![CDATA[This project began an investigation into whether it is possible to create a useful microwave communications link across the Gulf of Mexico in order to link the linear Florida Department of Transportation networks in the Florida Keys and Florida Panhandle, creating network redundancy for the first time for both segments. The work in this project has involved the design, procurement, construction, and initial testing of the equipment that will be used to conduct propagation testing under a future project. Originally the scope included the final stage of testing and the actual propagation tests. However, due to project delays, temporary university travel restrictions, and FDOT equipment scheduling issues, the scope was reduced to include only the tasks listed above. All of the work in the revised scope has been completed successfully. A future project will execute the final integrated system testing and deploy the equipment for actual field tests.]]></description>
      <pubDate>Mon, 27 Sep 2021 09:45:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/1870551</guid>
    </item>
    <item>
      <title>Visible Light Communication in 6G: Advances, Challenges, and Prospects</title>
      <link>https://trid.trb.org/View/1754679</link>
      <description><![CDATA[6G networks are expected to provide extremely high capacity and satisfy emerging applications, but current frequency bands may not be sufficient. Moreover, 6G will provide superior coverage by integrating space/air/underwater networks with terrestrial networks, given that traditional wireless communications are not able to provide high-speed data rates for nonterrestrial networks. Visible light communication (VLC) is a high-speed communication technique with an unlicensed frequency range of 400-800 THz and can be adopted as an alternative approach to solving these problems. In this article, the authors present the prospects and challenges of VLC in 6G in conjunction with its advances in high-speed transmissions. Recent hot research interests, including new materials and devices, advanced modulation, underwater VLC (UVLC), and signal processing based on machine learning, are also discussed. It is envisaged that VLC will become an indispensable part of 6G given its high-speed transmission advantages and will cooperate with other communication methods to benefit people's daily lives.]]></description>
      <pubDate>Tue, 22 Dec 2020 09:34:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1754679</guid>
    </item>
    <item>
      <title>Wireless 2.0: Toward an Intelligent Radio Environment Empowered by Reconfigurable Meta-Surfaces and Artificial Intelligence</title>
      <link>https://trid.trb.org/View/1754677</link>
      <description><![CDATA[In this article, the authors introduce Wireless 2.0, the future generation of wireless communication networks, in which the radio environment becomes controllable and intelligent by leveraging the emerging technologies of reconfigurable metasurfaces (RMSs) and artificial intelligence (AI). In particular, the authors emphasize AI-based computational methods and commence with an overview of the concept of intelligent radio environments (IREs) based on RMSs. Then, the authors elaborate on data management aspects, the requirements of supervised learning by examples, and the paradigm of reinforcement learning to learn by acting. Finally, the authors highlight numerous open challenges and research directions.]]></description>
      <pubDate>Tue, 22 Dec 2020 09:34:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1754677</guid>
    </item>
    <item>
      <title>An Outlook on the Interplay of Artificial Intelligence and Software-Defined Metasurfaces: An Overview of Opportunities and Limitations</title>
      <link>https://trid.trb.org/View/1754676</link>
      <description><![CDATA[Recent advances in programmable metasurfaces, known as software-defined metasurfaces (SDMs), offer a paradigm shift from uncontrollable to fully tunable and customizable wireless propagation environments, enabling a plethora of new applications and technological trends. To explore this cutting-edge technological concept, the authors review the architecture and electromagnetic (EM) wave manipulation functionalities of SDMs, detail recent advances toward realizing these programmable functionalities in wireless communication applications, elaborate on how artificial intelligence (AI) can address various constraints introduced by the real-time deployment of SDMs, review state-of-the-art research on the integration of AI with SDMs, and offer a look ahead toward unexplored possibilities of AI mechanisms in the context of SDMs.]]></description>
      <pubDate>Tue, 22 Dec 2020 09:34:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1754676</guid>
    </item>
    <item>
      <title>Radio Localization and Mapping With Reconfigurable Intelligent Surfaces: Challenges, Opportunities, and Research Directions</title>
      <link>https://trid.trb.org/View/1754675</link>
      <description><![CDATA[5G radio for millimeter-wave (mm-wave) and beyond5G concepts at 0.1-1 THz can exploit angle and delay measurements for localization through an increased bandwidth and large antenna arrays, but they are limited in terms of blockage caused by obstacles. Reconfigurable intelligent surfaces (RISs) are seen as a transformative technology that can control the physical propagation environment in which they are embedded by passively reflecting radio waves in preferred directions and actively sensing this environment in receive and transmit modes. While such RISs have mainly been intended for communication purposes, they can provide great benefits in terms of performance, energy consumption, and cost for localization and mapping. These benefits as well as associated challenges are the main topics of this article.]]></description>
      <pubDate>Tue, 22 Dec 2020 09:34:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1754675</guid>
    </item>
    <item>
      <title>Channel Modeling and System Concepts for Future Terahertz Communications: Getting Ready for Advances Beyond 5G</title>
      <link>https://trid.trb.org/View/1725552</link>
      <description><![CDATA[Future terahertz (THz) communications will utilize the frequency spectrum around 300 GHz. This technology provides a promising solution for future high-data-rate communications due to the high available bandwidth. However, the unfavorable channel characteristics are a major barrier for the realization of THz communications. To address the challenges caused by the unfavorable propagation conditions, the world's first THz communication standard includes a channel-modeling document (CMD).]]></description>
      <pubDate>Thu, 10 Sep 2020 09:50:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1725552</guid>
    </item>
    <item>
      <title>Availability of Maritime Radio Beacon Signals for R-Mode in the Southern Baltic Sea</title>
      <link>https://trid.trb.org/View/1714254</link>
      <description><![CDATA[This paper presents an overview of the development of a terrestrial positioning system called Ranging Mode (R-Mode) in the Southern Baltic Sea region which utilizes already existing maritime radio infrastructure. Here, an R-Mode testbed is planned to be set up until 2020 that meets maritime user needs for resilient PNT. First measurements of radio beacon signals on-board a vessel sailing in the Southern Baltic Sea show the good availability of beacon signals in this region. A comparison of received signals with a coverage prediction based on the nominal range of radio beacons shows the shortcoming of this approach and emphasizes the need for more elaborated coverage predictions which consider all effects of medium frequency wave propagation at day and night. In the measurements results the skywave has a major impact on the beacon signal stability in the night. The time stability of the signal amplitude seems to be a good indicator for disturbed reception conditions.]]></description>
      <pubDate>Tue, 23 Jun 2020 12:31:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1714254</guid>
    </item>
    <item>
      <title>Measurements and Analysis of Propagation Channels in Vehicle-to-Infrastructure Scenarios</title>
      <link>https://trid.trb.org/View/1702421</link>
      <description><![CDATA[In this paper,the authors present measurements and analysis of propagation channels in vehicle-to-infrastructure (V2I) scenarios, which are the basis of designing vehicular communication systems. Firstly, the authors propose a deterministic geometry-based method to classify V2I links into three types, i.e., line-of-sight beneath (LOS-B), non-LOS (NLOS), and line-of-sight above (LOS-A), based on the environmental features, where roadside row of trees constitute the main obstacles. Secondly, for each link, the authors investigate the large-scale fading effect on V2I channels, including the path loss exponent and shadowing components. Subsequently, the authors validate the empirical path loss model using extensive measurements and two classical channel models. The results show a good fit with a near-zero mean and tolerable standard deviation of the estimation error. Finally, the authors analyze the small-scale fading effects, including fading depth and distance-dependent Ricean K-Factor, which are very important for accurately predicting the required fading margin and link budget. Through the analysis and simulations, this work provides a reference of the V2I channel characteristics for the test, design, and performance analysis of V2I communication systems.]]></description>
      <pubDate>Tue, 26 May 2020 10:20:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1702421</guid>
    </item>
    <item>
      <title>Propagation Channels of 5G Millimeter-Wave Vehicle-to-Vehicle Communications: Recent Advances and Future Challenges</title>
      <link>https://trid.trb.org/View/1689741</link>
      <description><![CDATA[Wireless vehicular communications and sensing technologies are key to enabling more advanced intelligent transportation systems (ITSs) with improved safety and efficiency. Within the realm of wireless communication, millimeter-wave (mmwave) technology has recently received much attention, providing rich spectrum resources to support the timely transmission of large amounts of data. This is especially important for vehicular applications because the number of sensors on modern vehicles is rapidly increasing and thus generating large amounts of data. To fully exploit this potential, understanding mm-wave vehicle-to-vehicle (V2V) propagation channels is crucial. In this article, the authors review the state of the art in mm-wave V2V channel measurements and modeling, describe recent directional V2V channel measurements performed in the 60-GHz band, and discuss future challenges to be addressed in mm-wave V2V channel measurements and modeling.]]></description>
      <pubDate>Fri, 17 Apr 2020 09:37:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1689741</guid>
    </item>
    <item>
      <title>Characterizing Radio Wave Propagation in Urban Street Canyon With Vehicular Blockage at 28 GHz</title>
      <link>https://trid.trb.org/View/1686492</link>
      <description><![CDATA[The communications between two driving vehicles along a narrow street may be limited by the presence of a third vehicle blocking the transmission. In this work, the authors investigate radio wave propagation at 28 GHz in an urban street canyon scenario by conducting channel measurements, where the vehicle(s) occlude(s) the line-of-sight path. The authors quantify the impact of the car blockage and study the alternative propagation paths, which can be used for establishing a data link. Based on the obtained results, the authors report that besides the low-loss (3.4 dB) reflection from the wall, a radio link through the blocking car may potentially be established for data sharing. Specifically, the attenuation through clear windows is 2 dB, while the attenuation caused by sun protective film is 15 dB. Diffraction over the car and propagation in foliage reduce the multipath power drastically by 21–24 dB and 16–19 dB, respectively, and cannot be associated with reliable links. Finally, measurement results were compared with the ray-based simulation data, which demonstrate agreement to within ± 4.3 dB of measured losses.]]></description>
      <pubDate>Fri, 21 Feb 2020 10:24:20 GMT</pubDate>
      <guid>https://trid.trb.org/View/1686492</guid>
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