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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
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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>Spread Spectrum Data Transmission System for User Unmanned Aerial Vehicles</title>
      <link>https://trid.trb.org/View/2610786</link>
      <description><![CDATA[In today's world of unmanned aerial vehicle (UAV) telecommunications, data transmission is both important and delicate. Various organizations have used special techniques to ensure reliable transmission and stable communication. At this stage, we propose a method that enhances security and makes the transmission of data and image more resistant to interference and eavesdropping while improving signal reliability; this method is based on the Direct Sequence-Spread Spectrum (DS-SS) technique with a new pseudo-noise PN sequence created by merging chaotic and Barker sequences. MATLAB simulates these results for different spreading factors of the new sequence, and we evaluate the performance of the system in a user context on the Additive White Gaussian Noise (AWGN) channel. As a result, the new DS-SS technology improves the quality of data transmitted by UAVs.]]></description>
      <pubDate>Tue, 28 Oct 2025 13:42:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/2610786</guid>
    </item>
    <item>
      <title>CBTC Security and Reliability Enhancements by a Key-Based Direct Sequence Spread Spectrum Technique</title>
      <link>https://trid.trb.org/View/2325282</link>
      <description><![CDATA[A novel key-based Direct Sequence Spread Spectrum (DSSS) technique is proposed as a safety function for Communications-Based Train Control (CBTC) systems. According to well-known railway standards, namely IEEE 1474, IEC 61508, and EN 50128, CBTC systems should satisfy acceptable safety, security, and reliability levels. However, due to their inherent low-power features, prevalent CBTC systems cannot meet those levels perfectly in front of co-band interferences or attackers. Thus, a safety function is required which can be implemented without consuming much energy and restricted resources of CBTC systems. In this paper, the DSSS technique is based on a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG). Comprehensive time-domain analysis shows how this safety function enhances the safety, security, and reliability of CBTC systems concerning the standards mentioned above. It is proved that any inauthentic signal turns into a Gaussian term with significantly mitigated power at the output of the CBTC receiver. It is also established how to determine appropriate communications parameters based on railway properties. The proposed scheme’s failure rate performance is compared with that of similar works. Additionally, computer simulations and experiments verify the efficiency of the proposed safety function.]]></description>
      <pubDate>Fri, 19 Apr 2024 09:48:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/2325282</guid>
    </item>
    <item>
      <title>Parallel Offloading and Resource Optimization for Multi-Hop Ad Hoc Network-Enabled CBTC With Mobile Edge Computing</title>
      <link>https://trid.trb.org/View/2341445</link>
      <description><![CDATA[The emergence of communication-based train control (CBTC) system within urban rail transport has improved the efficiency of safe train operations. At the same time, the CBTC system enhances the reliability of the train system and lowers latency of the data transmission. Nevertheless, there are still certain critical issues that need to be considered in the CBTC: 1) limited coverage and high maintenance costs of wayside equipment; 2) multiple ground devices configuration and complex system architecture; and 3) insufficient computing capacity of the train leads to heavy latency and energy consumption. To cope with the above problems, in this article, the multi-hop ad hoc network coexisting with train-to-train communication and train-to-wayside communication is applied to simplify the networking architecture, together with the employment of mobile edge computing (MEC) servers to provide massive computing and communication resources for trains. Meantime, a new CBTC framework is developed for computing offloading and resource allocation via multi-hop ad hoc network and MEC. Offloading decisions, offloading ratio, computing and communication resource allocation are integrated to minimize latency and energy consumption. Furthermore, the proposed problem is a mixed-integer non-convex problem that is transformed into a solvable convex problem, and the consensus alternating direction method of multipliers-based (ADMM) algorithm is employed to solve the problem. The simulation results show that the authors' proposed method has remarkable advantages over other schemes.]]></description>
      <pubDate>Tue, 20 Feb 2024 09:25:34 GMT</pubDate>
      <guid>https://trid.trb.org/View/2341445</guid>
    </item>
    <item>
      <title>Error-Driven Information-Passing Policy for Model-Based Position Tracking in Vehicular Networks</title>
      <link>https://trid.trb.org/View/2313974</link>
      <description><![CDATA[The emerging Vehicle-to-Everything (V2X) communication technologies, i.e. Dedicated Short-Range Communications (DSRC) and Cellular-V2X (C-V2X), enhance the performance of the vehicular safety applications by increasing the range of perception, leading to more reliable vehicles' situational awareness. However, the scalability issue of such communication technologies, especially in congested urban areas, requires the employment of information dissemination strategies that avoid wasting network resources. Piggybacking compressed information over periodic Basic Safety Messages (BSM) and Model-Based Communication (MBC) are amongst such strategies to enhance situational awareness while addressing the scalability issue. Leveraging these notions, the authors propose a network-aware error-driven content selection technique to piggyback the information that is of more importance to the receiving vehicles. In addition, two different modeling schemes, i.e. a deterministic constant acceleration and yaw rate, and a probabilistic Bayesian inference modeling scheme have been introduced and their prediction performances under such content selection technique are compared to an existing distance-dependent piggybacking algorithm. Through simulations based on realistic traffic data, the authors show that our proposed Bayesian modeling scheme combined with the proposed content selection algorithm can improve the overall tracking accuracy by 53% compared to existing distance-dependent content selection approaches.]]></description>
      <pubDate>Wed, 27 Dec 2023 10:28:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2313974</guid>
    </item>
    <item>
      <title>Performance analysis of IEEE 802.11p preamble insertion in C-V2X sidelink signals for co-channel coexistence</title>
      <link>https://trid.trb.org/View/2304610</link>
      <description><![CDATA[Spectrum scarcity is one of the main challenges of future wireless technologies. When looking at vehicle-to-everything (V2X), this is amplified as spectrum sharing could impact road safety and traffic efficiency. It is therefore of particular importance to study solutions that allow the coexistence, in the same geographical area and in the same channels, of what are today the main V2X access technologies, namely IEEE 802.11p and long term evolution (LTE)-V2X sidelink Mode 4. In this paper, in addition to studying the impact of mutual interference, which is found to have a strong impact especially on the former and under congested channel conditions, a mitigation solution is extensively studied. The solution is based on the insertion of the IEEE 802.11p preamble at the beginning of each LTE-V2X sidelink transmission. The proposal, which is also under discussion within the standardization bodies, requires no changes to the IEEE 802.11p protocol stack and minor changes to LTE-V2X sidelink. This solution is directly applicable to upcoming IEEE 802.11bd and extendable to new radio (NR)-V2X sidelink. The paper shows, through analysis and simulations in free-flow and dense scenarios, that the proposal enables mitigation of collisions caused by co-channel coexistence under low and high load conditions. The improvement is guaranteed even in cases of congestion when combined with additional countermeasures. Regarding the latter aspect, in particular, different approaches are compared, demonstrating that acting on the congestion control mechanisms is a simple but effective solution.]]></description>
      <pubDate>Fri, 22 Dec 2023 08:46:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2304610</guid>
    </item>
    <item>
      <title>Two-Hop Connectivity to the Roadside in a VANET Under the Random Connection Model</title>
      <link>https://trid.trb.org/View/2156261</link>
      <description><![CDATA[In this paper, the authors compute the expected number of vehicles with at least one two-hop path to a fixed roadside unit (RSU) in a multi-hop, one-dimensional vehicular ad hoc network (VANET) where other cars can act as relays. The pairwise channels experience Rayleigh fading in the random connection model, and so exist, with probability function of the mutual distance between the cars, or between the cars and the RSU. The authors derive exact equivalents for the expected number of cars with a two-hop connection to the RSU when the car density $\rho$ tends to zero and infinity, and determine its behaviour using an infinite oscillating power series in $\rho$, which is accurate for all regimes. The authors also corroborate those findings to a realistic situation, using snapshots of actual traffic data. Finally, a normal approximation is discussed for the probability mass function of the number of cars with a two-hop connection to the RSU.]]></description>
      <pubDate>Fri, 21 Apr 2023 09:49:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/2156261</guid>
    </item>
    <item>
      <title>Spread Spectrum Coded Radar for R2R Interference Mitigation in Autonomous Vehicles</title>
      <link>https://trid.trb.org/View/2005786</link>
      <description><![CDATA[Autonomous Vehicles (AVs) rely on a set of radar sensors operated on frequency modulated waveforms. Due to the large bandwidth requirement of frequency modulated radars, only a limited number of proximate vehicles can be allowed for a concurrent transmission within the available spectrum. However, with the explosive growth of AVs, the available spectrum may soon reach its capacity. As a results, the coexistence of multiple AVs working on same resource, may lead to the problem of Radar-to-Radar (R2R) interference, also known as radar blindness. In this paper, the authors propose the notion of coded waveforms to minimize the R2R interference among the vehicles operating on the same resource. Specifically, the spread spectrum codes have been used as another degree of freedom (i.e., along with time-frequency resources) to spread the inter-vehicular radar interference over the wider spectrum, which enable to orthogonalize more number of AVs over the available range of spectrum. In addition, the authors have formulated a Spread Spectrum-based Radar Transmission Scheme (SS-RTS), and described the transmission and reception through SS-RTS. Also, the SS-RTS has been compared with the existing Graph-based Resource Allocation (GRA) scheme. Further, simulation results verified that SS-RTS significantly reduces the inter-vehicular R2R interference and outperforms GRA in terms of blind probability.]]></description>
      <pubDate>Thu, 15 Sep 2022 09:20:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/2005786</guid>
    </item>
    <item>
      <title>Latency and Reliability of mmWave Multi-Hop V2V Communications Under Relay Selections</title>
      <link>https://trid.trb.org/View/1745678</link>
      <description><![CDATA[Timely and reliable information sharing among autonomous vehicles (AVs) provides a promising approach for reducing traffic congestion and improving traffic efficiency in future intelligent transportation systems. In this paper, the authors consider millimeter-wave (mmWave) based multi-hop vehicle-to-vehicle (V2V) communications to facilitate ultra-reliable low-latency information sharing among AVs. The authors propose a novel framework for performance analysis and design of relay selection schemes in mmWave multi-hop V2V communications, while taking into account the mmWave signal propagation characteristics, road topology, and traffic conditions. In particular, considering the minimum tracking distance requirement of road traffic, the headway, i.e., the distance between adjacent AVs, is modeled as shifted-exponential distribution. Moreover, the authors model the communication path losses using the Manhattan distance metric in the taxicab geometry, which can more accurately capture the characteristics of mmWave signal propagation in urban grid roads than conventional Euclidean distance geometry. Based on the proposed model, the authors investigate the latency and reliability of mmWave multi-hop V2V communications for three widely adopted relay selection schemes, i.e., random with forward progress (RFP), most forward with fixed radius (MFR), and nearest with forward progress (NFP), respectively. Furthermore, the authors propose a novel relay selection scheme for joint optimization of the single-hop forward progress (FP) and single-hop latency according to the AVs’ instantaneous locations and an estimate of the residual multi-hop latency. Simulation results show that, by balancing the current single-hop latency and the residual multi-hop latency for the multi-hop V2V network, the proposed relay selection scheme significantly outperforms the MFR, NFP and RFP in both multi-hop transmission latency and reliability of mmWave V2V communications.]]></description>
      <pubDate>Thu, 29 Oct 2020 09:24:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/1745678</guid>
    </item>
    <item>
      <title>Low-Delay Path Selection for Cluster-Based Buffer-Aided Vehicular Communications</title>
      <link>https://trid.trb.org/View/1745661</link>
      <description><![CDATA[Channel gain based path selection has been recently proposed to simplify the network design of a cluster-based cross-layer multihop vehicular communications. In vehicular network systems, end-to-end packet delay increases with the growing number of vehicles associated in that path. In delay-sensitive application, the information exchange must be successfully carried out very quickly to ensure the quality of infotainment services. In the case of excessive packet delay, some important information either are needed to be enqueued before reaching the destination or are lost. The packet loss makes it impractical to deploy the network in practice. In this paper, a new delay-sensitive buffer-aided relay selection is proposed using the channel-based greedy scheduling algorithm (CGSA) to overcome the limitations imposed by processing delay. The proposed scheme significantly minimizes average delay by selecting a set of alternative paths based on individual node buffer status. This scheme has less packet delay than existing Max-link scheme with very close system performances, making it an ideal candidate for delay-sensitive applications. Finally, both analytical and simulation results are provided to demonstrate the performance improvement of the proposed algorithm compared with the existing relaying schemes.]]></description>
      <pubDate>Wed, 21 Oct 2020 09:52:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1745661</guid>
    </item>
    <item>
      <title>SDP-IGD: An Iterative Power Allocation Technique for Cluster-Based Multihop Vehicular Communications</title>
      <link>https://trid.trb.org/View/1737408</link>
      <description><![CDATA[This paper addresses the formulation of power allocation for cluster based multihop vehicular relaying communications in order to improve the network quality-of-services (QoS). The cluster-to-cluster (C2C) channel is completely depend on the power gain of vehicle-to-vehicle (V2V) channel that increases the difficulties of the power allocation problem. To meet this goal, the authors have derived a global channel obtained by joint V2V and C2C cooperation. The most challenging aspect is however the joint V2V and C2C power allocation of the global channel due to the association of its multi-variables objective function. To solve this problem, we apply an alternative optimization technique to make the global problem into a series of sub-problems. We then apply a semi-definite programming (SDP)-based iterative gradient descent (SDP-IGD) power allocation to assign power in each relay. The SDP-IGD power allocation algorithm has been extended from Lagrange Multiplier (LM) that provides better performance than separate LM technique. The minimum mean-square error (MMSE)-decision feedback equalizer (MMSE-DFE) is designed at the receiver to improve the signal detection capability under exact channel state information (CSI) in all forward-and-backward links. Finally, simulation results confirm that the authors' proposed solution performs significantly superior compared to other solutions found in the literature.]]></description>
      <pubDate>Tue, 29 Sep 2020 09:58:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/1737408</guid>
    </item>
    <item>
      <title>Spectrum Sharing for UAV Communications: Spatial Spectrum Sensing and Open Issues</title>
      <link>https://trid.trb.org/View/1725548</link>
      <description><![CDATA[Unmanned aerial vehicles (UAVs) are attracting increasing attention for applications such as video streaming, surveillance, and delivery using reliable line-of-sight (LOS) links. Nevertheless, due to the large radio-frequency (RF) transmission footprint from a UAV transmitted to ground nodes, UAV communications may significantly deteriorate the performance of cochannel ground communication links. With the lack of a dedicated spectrum, researchers need to design efficient spectrum-sharing policies for UAV communications to enhance spectral efficiency (SE) and control interference-to-ground communications. One technique for spectrum sharing is spatial spectrum sensing (SSS), which enables devices to sense spatial spectrum opportunities and reuse them aggressively and efficiently by controlling the SSS radius. The goal of this article is to introduce the fundamentals, challenges, and applications of SSS for UAV spectrum access and discuss open research problems for realizing UAV spectrum sharing, including dynamic spectrum access for swarm UAV networks, artificial intelligence (AI)-enabled UAV spectrum access, blockchain-based UAV spectrum access, multichannel access for UAVs, and the integration of UAVs into cellular networks.]]></description>
      <pubDate>Thu, 10 Sep 2020 09:50:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1725548</guid>
    </item>
    <item>
      <title>Spectral Efficiency Optimization and Interference Management for Multi-Hop D2D Communications in VANETs</title>
      <link>https://trid.trb.org/View/1729999</link>
      <description><![CDATA[D2D communications are considered as effective means to achieve vehicle-to-vehicle (V2V) communications, which can be used to improve the performance in vehicular ad hoc networks (VANETs). In this paper, the authors investigate the resource allocation and interference management based on clustering mechanism in the D2D communications under-laying VANETs aiming to optimize resource utilization efficiency. Firstly, given the transmission resources of intra-cluster for D2D communications, the authors design a vehicle clustering algorithm to improve intra-cluster resource efficiency and nullify the intra-cluster interference. Secondly, by analyzing the wireless service in VANETs, a cooperative communication scheme with optimized resource utilization is proposed to maximize intra-cluster spectral efficiency. Thirdly, when uplink spectrums are shared, an interference neutralization (IN) model is developed to manage inter-cluster interference, while each vehicle is equipped with one antenna and there is no extra antenna for interference cancellation. In accordance with the IN model, a cross-layer optimization frame for multi-hop VANETs is proposed to maximize the end-to-end throughput of multiple coexisting communication sessions. To evaluate the performance, the authors select the method without cooperative communication and IN as a benchmark and compare it against the method with cooperative communication only and the method with both cooperative communication and IN. The simulation results show that the method that uses cooperative communication and IN can dramatically increase the throughput. Furthermore, the throughput gains increase along with vehicle density growing in VANETs.]]></description>
      <pubDate>Thu, 27 Aug 2020 09:59:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/1729999</guid>
    </item>
    <item>
      <title>Optimal Best Path Selection Algorithm for Cluster-Based Multi-Hop MIMO Cooperative Transmission for Vehicular Communications</title>
      <link>https://trid.trb.org/View/1653153</link>
      <description><![CDATA[Multiple-input multiple-output (MIMO) cooperation in cluster-to-cluster communication has shown improved network quality of services by utilizing less transmission power over the fading environment. This is an enhancement from the traditional cluster-based single-input single-output multi-hop relaying used in vehicular communications. In this paper, the authors deploy multi-hop MIMO clustering relay into vehicular communication for a two-lane road transportation scenario. The authors deploy precoder and receiver filter in each MIMO link that is characterized by a narrowband classical three-dimensional time-varying channel. With the aid of the precoder and minimum mean square error receiver filtering algorithm in MIMO communication, the authors derive the end-to-end network signal-to-noise ratio to find the optimal best path using max-min theory with equal power allocation in precoder matrices that minimizes the network mean square error. A low-cost close-optimal best path selection method is also proposed through mathematical modeling. Computer simulation results demonstrate the validity of the theoretical investigations in this work.]]></description>
      <pubDate>Tue, 19 Nov 2019 14:12:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1653153</guid>
    </item>
    <item>
      <title>An Anti-Interference Scheme for UAV Data Links in Air–Ground Integrated Vehicular Networks</title>
      <link>https://trid.trb.org/View/1666120</link>
      <description><![CDATA[As one of the main applications of the Internet of things (IoT), the vehicular ad-hoc network (VANET) is the core of the intelligent transportation system (ITS). Air–ground integrated vehicular networks (AGIVNs) assisted by unmanned aerial vehicles (UAVs) have the advantages of wide coverage and flexible configuration, which outperform the ground-based VANET in terms of communication quality. However, the complex electromagnetic interference (EMI) severely degrades the communication performance of UAV sensors. Therefore, it is meaningful and challenging to design an efficient anti-interference scheme for UAV data links in AGIVNs. In this paper, the authors propose an anti-interference scheme, named as Mary-MCM, for UAV data links in AGIVNs based on multi-ary (M-ary) spread spectrum and multi-carrier modulation (MCM). Specifically, the Mary-MCM disperses the interference power by expanding the signal spectrum, such that the anti-interference ability of AGIVNs is enhanced. Besides, by using MCM and multiple-input multiple-output (MIMO) technologies, the Mary-MCM improves the spectrum utilization effectively while ensuring system performance. The simulation results verify that the Mary-MCM achieves excellent anti-interference performance under different EMI combinations.]]></description>
      <pubDate>Tue, 19 Nov 2019 14:12:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1666120</guid>
    </item>
    <item>
      <title>IEEE 802.11p MAC with Spectrum Sensing Scheme Reliable for VANET Using the Intelligent Transportation System</title>
      <link>https://trid.trb.org/View/1646828</link>
      <description><![CDATA[In congested areas, enough spectrum is needed to transmit safety and non-safety messages. Spectrum Sensing with Distributed TDMA (SSD-TDMA) accesses the channel in a distributed fashion to avoid the collision and the cyclic autocorrelation function is used to detect the energy at the vehicle level for broadcast signal. All information is aggregated for making a decision for data delivery in vehicular environments. The spectrum sensing method is employed to sense broadcast signals for finding out the occupancy status of the spectrum and availability of the licensed frequency bands. The performance of spectrum sensing technique and slot allocation based on the timestamp of a vehicle entering in the RSU coverage area in distributed manner is judged at a congested city state of affairs using the ns2 simulator. The proposed approach SSD-TDMA represents an effective and warranted conversation over Vehicular Adhoc Network (VANET) measured through the reduced delay and overhead of packet constraints.]]></description>
      <pubDate>Wed, 18 Sep 2019 09:17:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1646828</guid>
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