Showing papers in "IEEE Vehicular Technology Magazine in 2016"
TL;DR: The potential benefits and challenges of the 5G wireless heterogeneous network (HetNet) that incorporates massive MIMO and mmWave technologies are discussed.
Abstract: There has been active research worldwide to develop the next-generation, i.e., fifth-generation (5G), wireless network. The 5G network is expected to support a significantly large amount of mobile data traffic and a huge number of wireless connections and achieve better costand energy-efficiency as well as quality of service (QoS) in terms of communication delay, reliability, and security. To this end, the 5G wireless network should exploit the potential of new developments, including superdense and heterogeneous deployment of cells and massive antenna arrays [i.e., massive multiple-input, multiple-output (MIMO) technologies] and utilization of higher frequencies, particularly millimeter-wave (mmWave) frequencies. This article discusses the potential benefits and challenges of the 5G wireless heterogeneous network (HetNet) that incorporates massive MIMO and mmWave technologies.
372 citations
TL;DR: To handle increasing traffic, ensure passenger safety, and provide real-time multimedia information, a new communication system for HSR is required to replace the current GSM-railway (GSM-R) technology with the next-generation railway-dedicated communication system providing improved capacity and capability.
Abstract: High-speed railways (HSRs) improve the quality of rail services, yield greater customer satisfaction, and help to create socioeconomically balanced societies [1]. This highly efficient transport mode creates significant challenges in terms of investment, technology, industry, and environment. To handle increasing traffic, ensure passenger safety, and provide real-time multimedia information, a new communication system for HSR is required. In the last decade, public networks have been evolving from voice-centric second-generation systems, e.g., Global System for Mobile Communications (GSM) with limited capabilities, to fourth-generation (4G) broad-band systems that offer higher data rates, e.g., long-term evolution (LTE). It is thus relevant for HSR to replace the current GSM-railway (GSM-R) technology with the next-generation railway-dedicated communication system providing improved capacity and capability.
253 citations
TL;DR: UAVs can be operated as unmanned aerial BSs (UABSs), which can be deployed rapidly as a part of the heterogeneous-network (HetNet) architecture, however, due to their mobile characteristics, interference management in the network becomes challenging.
Abstract: Communications play an important role during public-safety operations. Because the current communication technologies heavily rely on the backbone network, the failure of base stations (BSs) due to natural disasters or malevolent attacks causes communication difficulties for public-safety and emergency communications. Recently, the use of unmanned aerial vehicles (UAVs), such as quadcopters and gliders, has gained attention in publicsafety communications (PSCs). They can be operated as unmanned aerial BSs (UABSs), which can be deployed rapidly as a part of the heterogeneous-network (HetNet) architecture. However, due to their mobile characteristics, interference management in the network becomes challenging.
172 citations
TL;DR: The fundamental physics and the related system structure of a promising wireless charging technique, i.e., distributed laser charging (DLC), are presented and a pair of wireless charging network architectures are proposed, which illustrate the potential of DLC in realizing the fully charged utopia for any device, anywhere, and anytime.
Abstract: Increasing the battery-recharge period of smartphones is becoming a challenge since their power consumption is increased as a result of enhanced functions that require sophisticated multimedia signal processing. An attractive solution is constituted by wireless charging, which is capable of replenishing the battery over the ether. Given this motivation, we present the fundamental physics and the related system structure of a promising wireless charging technique, i.e., distributed laser charging (DLC). Relying on DLC's unique features, we may be capable of transmitting approximately 2 W of power up to a distance of about 10 m. Following the comparison of the other three major wireless charging techniques, i.e., inductive coupling, magnetic resonance coupling, and microwave radiation, we demonstrate the benefits of DLC in the context of mobile applications. We then propose a pair of wireless charging network architectures, i.e., a DLC-aided, infrastructure-based network and a DLC-based ad-hoc network. These network architectures illustrate the potential of DLC in realizing the fully charged utopia for any device, anywhere, and anytime.
161 citations
TL;DR: The decision to standardize the narrowband (NB) Internet of Things (IoT), a new NB radio technology to address the requirements of the IoT, was achieved in the Third-Generation Partnership Project's (3GPP's) Radio Access Network Plenary Meeting 69.
Abstract: A major milestone was achieved in the Third-Generation Partnership Project's (3GPP's) Radio Access Network Plenary Meeting 69 with the decision to standardize the narrowband (NB) Internet of Things (IoT), a new NB radio technology to address the requirements of the IoT. The new technology will provide improved indoor coverage, support of a massive number of low-throughput devices, low delay sensitivity, ultralow device cost, low device power consumption, and optimized network architecture. The technology can be deployed in-band, utilizing resource blocks within a normal long-term evolution (LTE) carrier, or in the unused resource blocks within an LTE carrier's guard-band, or stand alone for deployments in dedicated spectrum. The NB-IoT is also particularly suitable for the refarming of Global System for Mobile Communications (GSM) channels.
128 citations
TL;DR: In this article, the authors provide insights on fundamental issues related to UDN deployment, such as determining the infrastructure density required to support the given traffic load requirements and the benefits of network-wise coordination, demonstrating the potential of UDNs for 5G wireless networks.
Abstract: The extreme traffic load that future wireless networks are expected to accommodate requires a rethinking of the system design. The initial estimations indicate that, unlike the evolutionary path of previous cellular generations that was based on spectral efficiency improvements, the most substantial amount of future system performance gains will be obtained by means of network infrastructure densification. By increasing the density of operator-deployed infrastructure elements along with incorporation of user-deployed access nodes (ANs) and mobile user devices acting as infrastructure prosumers, having one or more ANs exclusively dedicated to each user is expected to become feasible, introducing the ultradense network (UDN) paradigm. Although it is clear that UDNs are able to take advantage of the significant benefits provided by proximal transmissions and increased spatial reuse of system resources, large node density and irregular deployment introduce new challenges, mainly due to the interference environment characteristics that are vastly different from previous cellular deployments. This article attempts to provide insights on fundamental issues related to UDN deployment, such as determining the infrastructure density required to support the given traffic load requirements and the benefits of network-wise coordination, demonstrating the potential of UDNs for fifth-generation (5G) wireless networks.
84 citations
TL;DR: The age of autonomous vehicles is fast approaching, according to new survey results by the World Economic Forum, and most city authorities believe that applications such as shared self-driving vehicles are coming very quickly and will have the potential to be the last-mile solution for public transport.
Abstract: The age of autonomous vehicles is fast approaching, according to new survey results by the World Economic Forum. Nearly 60% of consumers in cities around the world are willing to travel in self-driving vehicles. In the consumer survey among 5,500 respondents in ten countries, acceptance is highest in emerging markets, such as China, India, and the United Arab Emirates; and about 50% in the United States and the United Kingdom; and acceptance rates were lowest in Japan and Germany. As part of a project, the World Economic Forum also conducted interviews with over 20 city policy makers and transport authorities from cities such as Dubai, Helsinki, New York, Amsterdam, Singapore, and Toronto about their expectations for self-driving vehicles. The survey showed that most city authorities believe that applications such as shared self-driving vehicles are coming very quickly and will have the potential to be the last-mile solution for public transport. City planners and governments thus need to prepare for the introduction of self-driving cars?smart mobility cities such as Gothenburg and Singapore are already doing so.
69 citations
TL;DR: A key characteristic of these channels is their temporal variability and inherent time-changing statistics, which have a major impact on electromagnetic propagation prediction.
Abstract: Intelligent transportation systems (ITSs) are currently under intense research and development for making transportation safer and more efficient. The development of such vehicular communication systems requires accurate models for the propagation channel. A key characteristic of these channels is their temporal variability and inherent time-changing statistics, which have a major impact on electromagnetic propagation prediction.
49 citations
TL;DR: This article presents the E2E 5G platform that is being developed by the Centre Tecnol?gic de Telecomunicacions de Catalunya (CTTC), the first known platform capable of reproducing such an ambitious scenario.
Abstract: The Internet of Things (IoT) will facilitate a wide variety of applications in different domains, such as smart cities, smart grids, industrial automation (Industry 4.0), smart driving, assistance of the elderly, and home automation. Billions of heterogeneous smart devices with different application requirements will be connected to the networks and will generate huge aggregated volumes of data that will be processed in distributed cloud infrastructures. On the other hand, there is also a general trend to deploy functions as software (SW) instances in cloud infrastructures [e.g., network function virtualization (NFV) or mobile edge computing (MEC)]. Thus, the next generation of mobile networks, the fifth-generation (5G), will need not only to develop new radio interfaces or waveforms to cope with the expected traffic growth but also to integrate heterogeneous networks from end to end (E2E) with distributed cloud resources to deliver E2E IoT and mobile services. This article presents the E2E 5G platform that is being developed by the Centre Tecnol?gic de Telecomunicacions de Catalunya (CTTC), the first known platform capable of reproducing such an ambitious scenario.
46 citations
TL;DR: Two new concepts for the development of highly directional steerable mmWave antennas are proposed and analyzed and modular antenna array (MAA) technology, which allows the creation of large-aperture, high-gain adaptive antenna arrays in a cost-effective and scalable manner is proposed.
Abstract: Modern millimeter-wave (mmWave) communication systems for large indoor areas and most outdoor scenarios require high-gain antennas with beam-steering ability to support user mobility or beam switching for reconfigurable backhauling. In this article, two new concepts for the development of highly directional steerable mmWave antennas are proposed and analyzed. The first one is modular antenna array (MAA) technology, which allows the creation of large-aperture, high-gain adaptive antenna arrays in a cost-effective and scalable manner. Two MAA configurations based on the existing phased subarray module are considered and analyzed for mmWave small-cell access and backhauling. The second prospective technology that fulfills the required antenna parameters for mmWave smallcell flexible backhauling is the lens-array antenna (LAA). The combination of the dielectric lens for aperture increasing with only one subarray module with beam-steering capabilities may provide 25?30-dBi total antenna gain with azimuth sector sweeping !45?.
38 citations
TL;DR: The rigorous system-level evaluation conducted for this study delivers important conclusions on the effects of user mobility in emerging D2D-centric systems and proposes an assessment methodology for D1D-enabled systems.
Abstract: Next-generation device-to-device (D2D) communication technology, in which a cellular network assists proximal users at all stages of their interaction, is rapidly developing. Previous research has thoroughly characterized D2D performance aspects from discovery to connection establishment, security, and service continuity; however, prospective D2Denabled applications and services envision highly opportunistic device contacts as a consequence of unpredictable human user mobility. Therefore, mobility's impact on D2D communication requires careful investigation to understand the practical operational efficiency of future cellular-assisted D2D systems. This article offers a first-hand tutorial on various implications of D2D mobility across different user movement patterns and mobility-related parameters and proposes an assessment methodology for D2D-enabled systems. The rigorous system-level evaluation conducted for this study delivers important conclusions on the effects of user mobility in emerging D2D-centric systems.
TL;DR: Power line communication (PLC) in the context of invehicle data networks can provide high-speed data connectivity via the exploitation of the existing power network, with clear potential benefits in terms of cost and weight reduction.
Abstract: This article deals with power line communication (PLC) in the context of invehicle data networks. This technology can provide high-speed data connectivity via the exploitation of the existing power network, with clear potential benefits in terms of cost and weight reduction. The focus is on two scenarios: an electric car (EC) and a cruise ship. An overview of the wiring infrastructure and the network topology in these two scenarios is provided. The main findings reported in the literature related to the channel characteristics are reported. Noise is also assessed with emphasis on the EC context. New results from the statistical analysis of measurements made in a compact EC and in a large cruise ship are also shown. The channel characteristics are analyzed in terms of average channel gain (ACG), delay spread (DS), coherence bandwidth (CB), and achievable transmission rate. Finally, an overall comparison is made, highlighting similarities and differences while taking into account the conventional combustion engine car and the largely investigated in-home scenario.
TL;DR: This article delivers useful practical contemplation of stray current calculation and monitoring endeavors in dc mass-transit systems by interpreting stray current calculations carried out at the design stage for real-life conditions and determining safety margins to cope with calculations following oversimplifying assumptions.
Abstract: This article delivers useful practical contemplation of stray current calculation and monitoring endeavors in dc mass-transit systems. We focus on interpreting stray current calculations-carried out at the design stage for real-life conditions-and on determining safety margins to cope with calculations following oversimplifying assumptions. We also discuss the general specifications and benefits of the direct stray current monitoring method, through addressing the implications that arise from implementing the alternative rail potential monitoring method informatively quoted in European (EN) Standards.
TL;DR: In this paper, the authors proposed a wireless body area network (WBAN) for continuous health monitoring and reducing the invasiveness of surgery, which can be collected over a longer period of time, and physicians are able to perform more reliable analysis.
Abstract: Technological advances in biomedical engineering have significantly improved the quality of life and increased the life expectancy of many people. One component of such advanced technologies is represented by wireless in vivo sensors and actuators, such as pacemakers, internal drug delivery devices, nerve stimulators, and wireless capsule endoscopes (WCEs). In vivo wireless body area networks (WBANs)and their associated technologies are the next step in this evolution and offer a cost-efficient and scalable solution along with the integration of wearable devices. In vivo WBAN devices are capable of providing continuous health monitoring and reducing the invasiveness of surgery. Furthermore, patient information can be collected over a longer period of time, and physicians are able to perform more reliable analysis by exploiting this big data rather than relying on the data recorded in short hospital visits.
TL;DR: A novel framework for integrating context awareness and self-healing is proposed, and a detailed context-based detection/diagnosis mechanism is developed, and the approach is evaluated in a real small-cell deployment, showing the feasibility and usefulness of the proposed context-aware self- healing system.
Abstract: This article proposes the use of context information for automatic failure management, known as self-healing, in small-cell indoor scenarios. Self-healing is one of the main functions of self-organizing networks (SONs) aiming to automate the administration, operation, and management of mobile communications infrastructure. In current deployments, the increasing use of low-power base stations, known as small cells, introduces challenges in classic self-healing procedures. This article analyzes those issues and identifies the context of user equipment (UE) as the main source of information to overcome them. Subsequently, a novel framework for integrating context awareness and self-healing is proposed, and a detailed context-based detection/diagnosis mechanism is developed. Finally, the approach is evaluated in a real small-cell deployment, showing the feasibility and usefulness of the proposed context-aware self-healing system.
TL;DR: A performance evaluation of CGR over time-varying topologies of a range of sizes is presented to have an understanding of its usability in a space-vehicle communication network with a large number of nodes.
Abstract: Delay-tolerant networking (DTN) is considered one of the most suitable technologies to handle challenging spacevehicle communications. Routing is critical in the DTN architecture. Contact graph routing (CGR) is a dynamic system that computes routes through a time-varying topology of scheduled communication contacts in the DTN architecture. There is an urgent need to study the scalability of CGR to very large networks. Following a discussion of CGR's operation, we present a performance evaluation of CGR over time-varying topologies of a range of sizes. The intent is to have an understanding of its usability in a space-vehicle communication network with a large number of nodes.
TL;DR: IEEE 802.11 is a working group operating under the sponsorship of the IEEE Local Area Network (LAN)/Metropolitan Area Network Standards Committee (LMSC) responsible for writing standards focusing on wireless LANs.
Abstract: IEEE 802.11 is a working group operating under the sponsorship of the IEEE Local Area Network (LAN)/Metropolitan Area Network Standards Committee (LMSC). It is responsible for writing standards focusing on wireless LANs (WLANs). A WLAN's typical transmission range is up to 100 m. Unlicensed spectrum is generally considered, including 2.4 GHz, 5 GHz, and 60 GHz, with a few exceptions, such as the lightly licensed spectrum being considered in IEEE 802.11y and the TV whitespace being considered in IEEE 802.11af.
TL;DR: In this article, a joint 5G technologies trial was conducted by NTT DOCOMO and Ericsson in an outdoor environment, using the 15 GHz frequency band with two simultaneously connected mobile devices of a downlink bitrate of more than 10 Gb/s each.
Abstract: Ericsson and NTT DOCOMO announced that in a joint fifth generation (5G) technologies trial, the companies achieved a cumulative 20 Gb/s of data throughput in an outdoor environment, using the 15-GHz frequency band with two simultaneously connected mobile devices of a downlink bitrate of more than 10 Gb/s each In a separate trial, the companies also achieved data throughput that exceeded 10 Gb/s at a distance of approximately 70 m from the base station Moreover, the tests reached data transmissions exceeding 9 Gb/s at a distance of approximately 120 m from the base station The trials used Ericsson 5G radio prototypes with multiple user, multiple-input, multiple-output (MU-MIMO) and massive MIMO to increase downlink throughput Ericsson 5G radio prototypes use MU-MIMO to transmit data to several user devices using the same time and frequency resources, thus increasing the system?s spectral efficiency Massive MIMO?the combination of MIMO and beamforming with a large number of antenna elements-improves both throughput and energy efficiency With beam tracking, Ericsson 5G radio prototypes track the position and movements of a given device and point one or more beams in the best direction for that device in real time, to ensure consistently reliable connections These beams can originate from multiple transmission points Each compact 5G radio prototype, the size of a piece of carry-on luggage, supports the equivalent of 40 long-term evolution (LTE) carriers
TL;DR: In this paper, a simple model to characterize the attenuation due to the isolated density of thin trees in an air-to-ground (satellite to mobile or helicopter to mobile) communication channel is proposed.
Abstract: We propose a simple model to characterize the attenuation due to the isolated density of thin trees in an air-to-ground (satellite-to-mobile or helicopter-to-mobile) communication channel. We analyzed the effect of the mobile receiver displacement, moving from far to near the tree along the direct ray path direction for different species of trees at X band (8-12 GHz) and Ku band (12-18 GHz) frequencies. Apart from a free-space region, we have identified two different scattering zones: a diffuse scattering-dominant region around the tree trunk, within which the signal level is modeled according to a statistical distribution function; and a zone where the diffraction on the tree crown prevails, modeled considering knife-edge diffraction loss with a correction of the tree height.
TL;DR: A framework for context-aware (CA) self-optimization in smallcell environments is described, and a particular self- Optimization use case, load balancing (LB), is used to evaluate the benefits of the proposed approach.
Abstract: Self-organizing network (SON) mechanisms in cellular systems automate network management procedures to improve performance while reducing operational expenditure (OPEX) and capital expenditure (CAPEX). Within the area of SON research and development, self-optimization is an especially hot research topic, and key use cases have been defined by Third-Generation Partnership Project (3GPP) standards. This article proposes to apply the context-awareness concept to self-optimizing small-cell networks. Context information provides valuable additional data to enhance self-optimization mechanisms. In this context, a framework for context-aware (CA) self-optimization in smallcell environments is described, and a particular self-optimization use case, load balancing (LB), is used to evaluate the benefits of the proposed approach. The results show that the proposed CA-LB algorithms increase the users? satisfaction, while the optimization time is significantly reduced.
TL;DR: Audi's research car, the Audi A7 piloted driving concept, internally nicknamed Jack, is now driving more naturally and signals upcoming lane changes by activating the turn signal and moving closer to the lane marking first, much like human drivers would do to indicate their intentions.
Abstract: Audi's research car, the Audi A7 piloted driving concept, internally nicknamed Jack, is now driving more naturally. Jack knows how to autonomously perform all of its driving maneuvers on the expressway and has now learned how to show consideration for other road users by adapting its driving style to the situation at hand. To this end, it now passes trucks with a slightly wider lateral gap. It also signals upcoming lane changes by activating the turn signal and moving closer to the lane marking first, much like human drivers would do to indicate their intentions. The cooperative attitude of Jack is especially apparent when other vehicles want to merge into the lane, such as on an expressway. Based on the selected driving profile, the test car decides whether to accelerate or brake, depending on which is best suited to handling the traffic situation harmoniously for all road users.
TL;DR: This research examines the challenges and opportunities presented by rigid requirements as well as emerging technology trends that are aimed at introducing improvements to the 5G wireless world.
Abstract: Wireless networks have made huge progress over the past three decades. Nevertheless, emerging fifth-generation (5G) networks are under pressure to continue in this direction at an even more rapid pace, at least for the next ten to 20 years. This pressure is exercised by rigid requirements as well as emerging technology trends that are aimed at introducing improvements to the 5G wireless world.
TL;DR: Progressive system improvement is achieved by the successive introduction of novel techniques, including orthogonal frequency division multiplexing (OFDM) and multiple-input, multiple-output (MIMO) antenna techniques, which helped to boost the performance of Wi-Fi to gigabit-persecond speed.
Abstract: The first few widely accepted amendments to IEEE 802.11 wireless networking specifications, namely IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g, featured relatively low spectral efficiencies and data rates. Driven by technological advances in signal processing and communications theory, sustained improvement in spectral efficiency, coverage, and quality of service has been achieved in IEEE 802.11n and IEEE 802.11ac. Particularly, progressive system improvement is achieved by the successive introduction of novel techniques, including orthogonal frequency division multiplexing (OFDM) and multiple-input, multiple-output (MIMO) antenna techniques. Some advanced transmission techniques, especially multiuser (MU)-MIMO and transmit beamforming, have also helped to boost the performance of Wi-Fi to gigabit-persecond speed, and they have led to the current state of the art, namely IEEE 802.11ac in 2.4- and 5-GHz bands, and IEEE 802.11ad in the 60-GHz frequency band.
TL;DR: In this article, various retransmission mechanisms are considered for providing end-to-end ETCS data integrity in LTE and are validated in simulations, which model worst-case conditions regarding train locations, traffic load, and base-station density.
Abstract: The European Train Control System (ETCS) is the leading signaling system for train command and control. In the future, ETCS may be delivered over long-term evolution (LTE) networks. Thus, LTE performance offered to ETCS must be analyzed and confronted with the railway safety requirements. It is especially important to ensure the integrity of the ETCS data, i.e., to protect ETCS data against loss and corruption. In this article, various retransmission mechanisms are considered for providing end-to-end ETCS data integrity in LTE. These mechanisms are validated in simulations, which model worst-case conditions regarding train locations, traffic load, and basestation density. The simulation results show that ETCS data integrity requirements can be fulfilled even under these unfavorable conditions with the proper LTE mechanisms.
TL;DR: In addition to acquiring Otto, a startup introducing self-driving technology on existing trucks, Uber teamed up with Volvo Car Corporation to create autonomous ride-hailing vehicles.
Abstract: i»?In addition to acquiring Otto, a startup introducing self-driving technology on existing trucks, Uber teamed up with Volvo Car Corporation to create autonomous ride-hailing vehicles. Volvo and Uber engineers will collaborate on vehicle development, and Uber will add its self-developed autonomous driving systems to the Volvo base vehicle. The base vehicle will be developed on Volvoâs modular scalable product architecture (SPA). The project will enhance to the scalability of the SPA platform to include the safety, redundancy, and new features required for autonomous vehicles to be permitted on the road.
TL;DR: Multipath Transmission Control Protocol integration in the ERTMS protocol stack in a test bed is evaluated as a way to use heterogeneous radio bearers seamlessly and simultaneously and validated by comparing the obtained results to the European Integrated Radio Enhanced Network requirements.
Abstract: The European Rail Traffic Management System (ERTMS) is becoming a worldwide de facto standard for high-speed railway signaling. A major shortcoming of this system is that it is attached to a single radio-bearer technology, the Global System for Mobile Communications-Railway (GSM-R). The migration of ERTMS toward Internet Protocol (IP) provides the opportunity to make ERTMS unaware of the underlying communication technology by establishing train-to-ground connectivity via multiple bearers. In this article, we evaluate Multipath Transmission Control Protocol (MPTCP) integration in the ERTMS protocol stack in a test bed as a way to use heterogeneous radio bearers seamlessly and simultaneously. We validate this strategy by comparing our obtained results to the European Integrated Radio Enhanced Network (EIRENE) requirements and demonstrate its functionality as a seamless fail recovery strategy.
TL;DR: The G7 Declaration on Automated and Connected Driving will address fundamental issues related to the harmonization of the regulatory framework and the role and obligations of drivers using this new technology.
Abstract: To make a significant contribution to increasing road safety and improving mobility worldwide, the transport ministers of the group of seven states (G7) and the European Commissioner for Transport will jointly support developments in the field of automated and connected driving. Their G7 Declaration on Automated and Connected Driving [1] will address fundamental issues related to the harmonization of the regulatory framework and the role and obligations of drivers using this new technology.
TL;DR: An update on Wi-Fi Alliance, which is a global, nonprofit industry association of approximately 700 leading companies from dozens of countries devoted to seamless interoperability, is shared.
Abstract: i»?In my past two âStandardsâ columns, I provided an extensive update on the latest standardization developments of Wi-Fi in IEEE 802.11, which is a working group operating under the sponsor IEEE Local and Metropolitan Area Networks (LAN/ MAN) Standards Committee. In this column, I would like to share an update on Wi-Fi Alliance, which is a global, nonprofit industry association of approximately 700 leading companies from dozens of countries devoted to seamless interoperability.
TL;DR: Numerical and empirical results suggest that the model provides an accurate tool for analyzing diffraction effects of tunnel discontinuities with sharp edges on the process of radio propagation, and offers sufficient versatility to assimilate a variety of discontinuous geometries involving sharp edges in a tunnel environment.
Abstract: The overall performance of a communication-based train control (CBTC) system largely depends on the performance of its data communications subsystem (DCS). The DCS network in almost all CBTC commercial system products marketed in the last decade uses radio communications in the open industrial, scientific, and medical (ISM) bands (2.4 or 5.8 GHz) to establish the bidirectional data link between central/wayside and onboard segments. Key factors in ensuring stable and sound radio communication are the number of wayside access points and locations of their antennas. Radio propagation modeling aims to provide optimal and reasonably reliable assurance of stable communication. However, the diffraction impact of sharp corners and edges in tunnels on the radio propagation process has been unaccounted for in the majority of models. The purpose of the present research is to incorporate the effect of diffraction coupling due to sharp edges in tunnel sections, including geometrical discontinuities such as cross junctions and L bends, through ray-mode conversion. The proposed modeling approach offers sufficient versatility to assimilate a variety of discontinuous geometries involving sharp edges in a tunnel environment. Numerical and empirical results suggest that the model provides an accurate tool for analyzing diffraction effects of tunnel discontinuities with sharp edges on the process of radio propagation.