| 1. |
- Abbas, Taimoor, et al.
(författare)
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A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations
- 2015
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877.
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Tidskriftsartikel (refereegranskat)abstract
- The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading.
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| 2. |
- Baiocchi, Andrea, et al.
(författare)
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Age of Information in IEEE 802.11p
- 2021
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Ingår i: 2021 IFIP/IEEE International Symposium on Integrated Network Management (IM). - : IEEE. - 9783903176324 - 9781728190419 ; , s. 1024-1031
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Konferensbidrag (refereegranskat)abstract
- Vehicle-to-Everything (V2X) communication is essential for facilitating connected and automated driving, where vehicles and other road traffic participants share data instantaneously and cooperate to solve tricky traffic situations in milliseconds. This paper proposes two stochastic models for the V2X standard IEEE 802.11p to characterize amongst other things the Age of Information (AoI), a recently-proposed metric that measures the freshness of information. The first model is based on renewal process analysis of a tagged station with mean field approximation, while the second one adopts Markov chain approach with network level view. Analytical results show that IEEE 802.11p, given its adaptability to event-triggered and aperiodic messaging, supports advanced cooperative driving scenarios.
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| 3. |
- Belyaev, Evgeny, et al.
(författare)
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Live video streaming in IEEE 802.11p vehicular networks : Demonstration of an automotive surveillance application
- 2014
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Ingår i: Computer Communications Workshops (INFOCOM WKSHPS), 2014 IEEE Conference on. - Piscataway, United States : IEEE Press. - 9781479930883 ; , s. 131-132
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Konferensbidrag (refereegranskat)abstract
- Prospective IEEE 802.11p-enabled automotive video applications are identified. Preliminary experimental results of inter-vehicular live video streaming for surveillance applications are presented. A test-bed for the demonstration of the achievable visual quality under different channel conditions is described.
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| 4. |
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| 5. |
- Bilstrup, Urban, et al.
(författare)
-
A fault tolerance test enabling QoS in a Bluetooth piconet
- 2004
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Konferensbidrag (populärvet., debatt m.m.)abstract
- An important trend, in personal area networks, is that time critical application becomes more common, e.g., voice over IP, video phone calls, network games. This segment of applications demands for quality of service (QoS) guarantees, to provide the correct functionality. The Bluetooth standard provides an optional interface to support QoS guarantees, but the standard does not suggest any actual implementation. A wireless communication channel is stochastic by nature, providing QoS guarantees with this precondition make traditional deterministic real-time theory obsolete. In this paper a probabilistic fault tolerance test enabling quality of service guarantees in a Bluetooth piconet is given. The basic Bluetooth network architecture is based on a master-slave configuration, i.e., a point to point connection. More advanced network architectures are possible where up to eight Bluetooth equipped units can be active members of one network (piconet). Furthermore, several piconets can interconnect and form a so called scatternet.
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| 6. |
- Bilstrup, Urban, et al.
(författare)
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Capacity limitations in wireless sensor networks
- 2003
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Ingår i: ETFA 2003. - Piscataway, N.J. : IEEE. - 0780379373 ; , s. 529-536
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Konferensbidrag (refereegranskat)abstract
- It is expected that wireless sensor network will be used in home automation and industrial manufacturing in the future. The main driving forces for wireless sensor networks are fault tolerance, energy gain and spatial capacity gain. Unfortunately, an often forgotten issue is the capacity limits that the network topology of a wireless sensor network represents. In this paper we identify gains, losses and limitations in a wireless sensor network, using a simplified theoretical network model. Especially, we want to point out the stringent capacity limitations that this simplified network model provide. Where a comparison between the locality of the performed information exchange and the average capacity available for each node is the main contribution.
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| 7. |
- Christoph, Mecklenbräuker, et al.
(författare)
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Vehicle-to-Vehicle Communications
- 2012
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Ingår i: Pervasive Mobile and Ambient Wireless Communications, Roberto Verdone and Alberto Zanella, editors. Springer. - London : Springer London. - 9781447123149 ; , s. 577-608
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Fricke, Katrin, et al.
(författare)
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Impact of Left Ventricular Morphology on Adverse Outcomes Following Stage 1 Palliation for Hypoplastic Left Heart Syndrome: 20 Years of National Data From Sweden
- 2022
-
Ingår i: Journal of the American Heart Association. - : John Wiley & Sons. - 2047-9980. ; 11:7
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Hypoplastic left heart syndrome is associated with significant morbidity and mortality. We aimed to assess the influence of left ventricular morphology and choice of shunt on adverse outcome in patients with hypoplastic left heart syndrome and stage 1 palliation. METHODS AND RESULTS: This was a retrospective analysis of patients with hypoplastic left heart syndrome with stage 1 palliation between 1999 and 2018 in Sweden. Patients (n=167) were grouped based on the anatomic subtypes aortic-mitral atresia, aortic atresia-mitral stenosis (AA-MS), and aortic-mitral stenosis. The left ventricular phenotypes including globular left ventricle (Glob-LV), miniaturized and slit-like left ventricle (LV), and the incidence of major adverse events (MAEs) including mortality were assessed. The overall mortality and MAEs were 31% and 41%, respectively. AA-MS (35%) was associated with both mortality (all other subtypes versus AA-MS: interstage-I: hazard ratio [HR], 2.7; P=0.006; overall: HR, 2.2; P=0.005) and MAEs (HR, 2.4; P=0.0009). Glob-LV (57%), noticed in all patients with AA-MS, 61% of patients with aortic stenosis-mitral stenosis, and 19% of patients with aortic atresia-mitral atresia, was associated with both mortality (all other left ventricular phenotypes versus Glob-LV: interstage-I: HR, 4.5; P=0.004; overall: HR, 3.4; P=0.0007) and MAEs (HR, 2.7; P=0.0007). There was no difference in mortality and MAEs between patients with AA-MS and without AA-MS with Glob-LV (P>0.15). Patients with AA-MS (35%) or Glob-LV (38%) palliated with a Blalock-Taussig shunt had higher overall mortality compared with those palliated with Sano shunts, irrespective of the stage 1 palliation year (AA-MS: HR, 2.6; P=0.04; Glob-LV: HR, 2.1; P=0.03). CONCLUSIONS: Glob-LV and AA-MS are independent morphological risk factors for adverse short-and long-term outcome, especially if a Blalock-Taussig shunt is used as part of stage 1 palliation. These findings are important for the clinical management of patients with hypoplastic left heart syndrome.
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| 9. |
- Lidström, Kristoffer, 1981-, et al.
(författare)
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A Modular CACC System Integration Design
- 2012
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - Piscataway : IEEE Press. - 1524-9050 .- 1558-0016. ; 13:3, s. 1050-
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the Halmstad University entry in the GrCooperative Driving Challenge, which is a competition in vehicle platooning. Cooperative platooning has the potential to improve traffic flow by mitigating shock wave effects, which otherwise may occur in dense traffic. A longitudinal controller that uses information exchanged via wireless communication with other cooperative vehicles to achieve string-stable platooning is developed. The controller is integrated into a production vehicle, together with a positioning system, communication system, human€“machine interface (HMI). A highly modular system architecture enabled rapid development testing of the various subsystems. In the competition, which took place in May 2011 on a closed-off highway in The Netherlands, the Halmstad University team finished second among nine competing teams._x000D_
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| 10. |
- Lidström, Kristoffer, 1981-, et al.
(författare)
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Halmstad University Grand Cooperative Driving Challenge 2011 Technical Paper
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Traffic congestion is a large and growing problem in many countries due to an ever increasing number of vehicles. Increasing capacity by simply extending the road infrastructure is in many places impossible due to space and cost limitations. Everyday, people spend countless hours in car queues all over the world. The existing road infrastructure must be better utilized to save time and to reduce energy use. By enabling wireless communication between vehicles (V2V) and between vehicles and infrastructure (V2I) the flow of traffic can be better controlled in order to increase not only efficiency but also safety and comfort. Cooperative platooning is one way to increase efficiency by allowing vehicles to form road trains behind a lead vehicle. The Grand Cooperative Driving Challenge (GCDC) is an attempt to move towards a quicker deployment of cooperative platooning. This extended abstract gives an overview of Halmstad University’s team and its technical and organizational approach in preparing a vehicle for the competition.
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| 11. |
- Mecklenbräuker, Christoph, et al.
(författare)
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Vehicle-to-Vehicle Communications
- 2012
-
Ingår i: Pervasive Mobile and Ambient Wireless Communications. - London : Springer London. - 9781447123156 - 9781447123149 ; , s. 577-608
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter discusses major results and conclusions from Special Interest Group C bringing together various aspects of mobile to mobile communication from all working groups. Vehicle-to-vehicle communication scenarios are emphasized. Traffic telematics applications are currently under intense research and development for making transportation safer, more efficient, and cleaner. Communication systems which provide “always on” connectivity at data rates between 1 and 10 Mb/s to highly mobile surface traffic (cars and trains) are urgently required for developing traffic telematics applications and services. Currently much attention is given to advanced active safety, but the application area also ranges to improved navigation mechanisms and infotainment services. mobile to mobile communications need to be reliable and trusted: Drivers in cars which are equipped with vehicle to vehicle communications need to rely on the accuracy and timeliness of the exchanged data. Automotive manufacturers, road authorities, broadcast companies, and telecom providers are the key players in the value chain for such future systems. These communication systems provide an extended information horizon to warn the driver or the vehicular systems of potentially dangerous situations in an early phase.
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| 12. |
- Shahin, Hady, et al.
(författare)
-
Human serum albumin as a clinically accepted cell carrier solution for skin regenerative application
- 2020
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The rules governing Medicinal Products in the European Union necessitates the production of cell-based therapy in good manufacturing practice facilities. The produced cells may need several hours in transportation to reach the application sites. In this study, we investigated four candidate solutions for transporting human keratinocytes. The solutions are (1) normal saline, (2) saline with 2.5% human serum albumin (Saline + HSA), (3) chemically defined, xeno-free keratinocyte media and (4) keratinocyte media with pituitary bovine extract (PBE-media). One million keratinocytes from three donors were suspended in each solution and kept at 4 °C for up to 24 h. Cells kept in Saline + HSA showed higher viability after 1, 3 and 24 h. Then, equal number of viable cells were seeded on collagenous matrix and cultured for 48 h. The adhesion and colonization were higher in the cells kept in PBE-media, while the keratinocyte surface marker, cytokeratin 14, was present in all studied groups. These results confirmed the suitability of Saline + HSA as a cell transportation solution for clinical use, which will be the choice for the planned clinical trial. Keratinocyte PBE-media can be an alternative for cells transported for research purpose, if the same media type is going to be used in the following experiments.
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| 13. |
- Sidorenko, Galina, 1985-, et al.
(författare)
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Safety of Automatic Emergency Braking in Platooning
- 2022
-
Ingår i: IEEE Transactions on Vehicular Technology. - Piscataway : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 71:3, s. 2319-2332
-
Tidskriftsartikel (refereegranskat)abstract
- A platoon comprises a string of consecutive highly automated vehicles traveling together. Platooning allows for increased road utilization and reduced fuel consumption due to short inter-vehicular distances. Safety in terms of guaranteeing no rear-end collisions is of utmost importance for platooning systems to be deployed in practice. We compare how safely emergency braking can be handled by emerging V2V communications on the one hand and by radar-based measurements of existing AEBS on the other. We show that even under conservative assumptions on the V2V communications, such an approach significantly outperforms AEBS with an ideal radar sensor in terms of allowed inter-vehicle distances and response times. Furthermore, we design two emergency braking strategies for platooning based on V2V communications. The first braking strategy assumes centralized coordination by the leading vehicle and exploits necessary optimal conditions of a constrained optimization problem, whereas the second -- the more conservative solution -- assumes only local information and is distributed in nature. Both strategies are also compared with the AEBS.
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| 14. |
- Sidorenko, Galina, 1985-, et al.
(författare)
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Vehicle-to-Vehicle Communication for Safe and Fuel-Efficient Platooning
- 2020
-
Ingår i: 2020 IEEE Intelligent Vehicles Symposium (IV). - Piscataway : Institute of Electrical and Electronics Engineers (IEEE). - 9781728166735 ; , s. 795-802
-
Konferensbidrag (refereegranskat)abstract
- A platoon consists of a string of vehicles traveling close together. Such tight formation allows for increased road throughput and reduced fuel consumption due to decreased air resistance. Furthermore, sensors and control algorithms can be used to provide a high level of automation. In this context, safety – in terms of no rear-end collisions – is a key property that needs to be assured. We investigate how vehicle-to-vehicle communication can be used to reduce inter-vehicle distances while guaranteeing safety in emergency braking scenarios. An optimization-based modeling scheme is presented that, under certain restrictions, provides an analytical calculation of inter-vehicle distances for safe braking. In contrast to earlier simulation-based approaches, the framework allows for computationally efficient solutions with explicit guarantees. Two approaches for computing braking strategies in emergency scenarios are proposed. The first assumes centralized coordination by the leading vehicle and exploits necessary optimal conditions of a constrained optimization problem, whereas the second – the more conservative solution – assumes only local information and is distributed in nature. We illustrate the usefulness of the approaches through several computational simulations. © 2020 IEEE.
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| 15. |
- Sjöberg Bilstrup, Katrin
(författare)
-
Predictable and Scalable Medium Access Control for Vehicular Ad Hoc Networks
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis work investigates two medium access control (MAC) methods, when used in traffic safety applications over vehicular ad hoc networks (VANETs). The MAC methods are carrier sense multiple access (CSMA), as specified by the leading standard for VANETs IEEE 802.11p, and self-organizing time-division multiple access (STDMA) as used by the leading standard for transponders on ships. All vehicles in traffic safety applications periodically broadcast cooperative awareness messages (CAMs). The CAM based data traffic implies requirements on a predictable, fair and scalable medium access mechanism. The investigated performance measures are channel access delay, number of consecutive packet drops and the distance between concurrently transmitting nodes. Performance is evaluated by computer simulations of a highway scenario in which all vehicles broadcast CAMs with different update rates and packet lengths. The obtained results show that nodes in a CSMA system can experience unbounded channel access delays and further that there is a significant difference between the best case and worst case channel access delay that a node could experience. In addition, with CSMA there is a very high probability that several concurrently transmitting nodes are located close to each other. This occurs when nodes start their listening periods at the same time or when nodes choose the same backoff value, which results in nodes starting to transmit at the same time instant. The CSMA algorithm is therefore both unpredictable and unfair besides the fact that it scales badly for broadcasted CAMs. STDMA, on the other hand, will always grant channel access for all packets before a predetermined time, regardless of the number of competing nodes. Therefore, the STDMA algorithm is predictable and fair. STDMA, using parameter settings that have been adapted to the vehicular environment, is shown to outperform CSMA when considering the performance measure distance between concurrently transmitting nodes. In CSMA the distance between concurrent transmissions is random, whereas STDMA uses the side information from the CAMs to properly schedule concurrent transmissions in space. The price paid for the superior performance of STDMA is the required network synchronization through a global navigation satellite system, e.g., GPS. That aside since STDMA was shown to be scalable, predictable and fair; it is an excellent candidate for use in VANETs when complex communication requirements from traffic safety applications should be met.
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| 16. |
- Sjöberg-Bilstrup, Katrin, et al.
(författare)
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Scalability issues of the MAC methods STDMA and CSMA of IEEE 802.11p when used in VANETs
- 2010
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Ingår i: 2010 IEEE International Conference on Communications Workshops (ICC). - Cape Town, South Africa : IEEE Computer Society. - 9781424468249 - 9781424468263 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Position messages will be the foundation for many emerging traffic safety applications based on wireless communications. These messages contain information about the vehicle’s position, speed, direction, etc. and are broadcasted periodically by each vehicle. The upcoming IEEE 802.11p standard, intended for vehicle unpredictable behavior of its medium access control (MAC) scheme, which imply that traffic safety applications cannot be supported satisfactorily when the network load increases. We study the MAC mechanism within IEEE 802.11p being a carrier sense multiple access (CSMA) algorithm and compare it with a self-organizing time division multiple access (STDMA) scheme when used for broadcasting periodic position messages in a realistic highway scenario. We investigate their scalability in terms of the number of vehicles that the VANET can support using metrics such as channel access delay, probability of concurrent transmissions and interference distance. The results show that STDMA outperforms CSMA of 802.11p even when the network is not saturated.
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| 17. |
- Sjöberg, Katrin, 1972-, et al.
(författare)
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Delay and interference comparison of CSMA and self-organizing TDMA when used in VANETs
- 2011
-
Ingår i: IWCMC 2011. - New York, NY : IEEE Press. - 9781424495399 - 9781424495375 ; , s. 1488-1493
-
Konferensbidrag (refereegranskat)abstract
- IEEE 802.11p is the proposed wireless technology for communication between vehicles in a vehicular ad hoc network (VANET) aiming to increase road traffic safety. In a VANET, the network topology is constantly changing, which requires distributed self-organizing medium access control (MAC) algorithms, but more importantly the number of participating nodes cannot be restricted. This means that MAC algorithms with good scalability are needed, which can fulfill the concurrent requirements on delay and reliability from road traffic safety applications. The MAC method of IEEE 802.11p is a carrier sense multiple access (CSMA) scheme, which scales badly in terms of providing timely channel access for a high number of participating nodes. We therefore propose using another MAC method: selforganizing time division multiple access (STDMA) with which all nodes achieve timely channel access regardless of the number of participating nodes. We evaluate the performance of the two MAC methods in terms of the MAC-to-MAC delay, a measure which captures both the reliability and the delay of the delivered data traffic for a varying number of vehicles. The numerical results reveal that STDMA can support almost error-free transmission with a 100 ms deadline to all receivers within 100 m, while CSMA suffers from packet errors. Moreover, for all considered cases, STDMA offers better reliability than CSMA.
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| 18. |
- Sjöberg, Katrin, et al.
(författare)
-
How severe is the hidden terminal problem in VANETs when using CSMA and STDMA?
- 2011
-
Ingår i: IEEE Vehicular Technology Conference (VTC Fall). - Piscataway, N.J. : IEEE conference proceedings. - 1090-3038. - 9781424483280 ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- The hidden terminal problem is often said to be the major limiting performance factor in vehicular ad hoc networks. In this article we propose a definition of the hidden terminal problem suitable for broadcast transmissions and proceed with a case study to find how the packet reception probability is affected by the presence of hidden terminals. Two different medium access control methods; carrier sense multiple access (CSMA) from IEEE 802.11p and self-organizing time division multiple access (STDMA), are subject of investigation through computer simulations of a highway scenario with a Nakagami fading channel model. The results reveal that the presence of hidden terminals does not significantly affect the performance of the two MAC protocols. STDMA shows a higher packet reception probability for all settings due to the synchronized packet transmissions.
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| 19. |
- Sjöberg, Katrin, et al.
(författare)
-
Measuring and using the RSSI of IEEE 802.11p
- 2010
-
Ingår i: 17th World Congress on Intelligent Transport Systems, ITS 2010, Busan, South Korea, 25-29 October 2010.
-
Konferensbidrag (refereegranskat)abstract
- The scalability of intelligent transport systems (ITS) applications is difficult to test in a field operational test (FOT) due to the high number of ITS equipped vehicles required. Therefore, computer simulations for evaluating different wireless communication technologies for ITS different applications can serve as a complement. In this paper we present results from lab measurements conducted on the CVIS hardware platform equipped with the upcoming standard IEEE 802.11p. We have measured the packet error rate versus the signal-to-noise ratio (SNR) for different packet lengths. This lab measurement is the first step towards an outdoor measurement campaign which also considers interference. The outdoor measurements will then be fed into a computer simulator together with a realistic channel model for evaluating the scalability of VANETs in a highway scenario.
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| 20. |
- Sjöberg, Katrin, 1972
(författare)
-
Medium access control for vehicular ad hoc networks
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cooperative intelligent transport systems (C-ITS), where vehicles cooperate by exchanging messages wirelessly to avoid, for example, hazardous road traffic situations, receive a great deal of attention throughout the world currently. Many C-ITS applications will utilize the wireless communication technology IEEE 802.11p, which offers the ability of direct communication between vehicles, i.e., ad hoc communication, for up to 1000 meters. In this thesis, medium access control (MAC) protocols for vehicular ad hoc networks (VANET) are scrutinized and evaluated. The MAC protocol decides when a station has the right to access the shared communication channel and schedules transmissions to minimize the interference at receiving stations. A VANET is a challenging network for the MAC protocol because the number of stations in is unknown a priori and cannot be bounded. Therefore, the scalability of the MAC method has a major influence on the performance of C-ITS applications. Two different MAC protocols are studied: carrier sense multiple access (CSMA) of 802.11p and self-organizing time division multiple access (STDMA). These two MAC methods are examined with re-spect to the communication requirements and protocol settings arising from C-ITS standardization. Based on these constraints, suitable performance measures are derived such as MAC-to-MAC delay and detection distance, where the former catches both the delay and reliability. In STDMA, the channel access delay is upper-bounded and therefore known before transmission, since regardless of the number of stations within radio range, all stations are always guaranteed timely channel access. In CSMA, the channel access delay is not upper-bounded and it is unknown until transmission commences, as it is based on the instantaneous channel load and stations can experience a random delay when in backoff. The evaluation of CSMA and STDMA is performed through extensive computer simulations, model-ling a 10 km highway with six lanes in each direction. Vehicles travel along the highway and broad-cast position messages periodically with different update rates. Two different channel models have been used during the evaluations, one distinguishing between a receiver being in line-of-sight (LOS) or obstructed LOS (OLOS) from the transceiver, while the other does not consider this. The simulation results, for both channel models, show that CSMA has on average a smaller channel access delay than STDMA. However, the results also reveal that STDMA always achieves a better reliability than CSMA, especially for distances of 100-500 meters between transmitter and receiver. The distance, at which approaching stations receive the first messages from each other, is up to 100 meters longer for STDMA than CSMA. This thesis therefore concludes that STDMA is a very suitable MAC method for VANET-based C-ITS applications.
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| 21. |
- Sjöberg, Pia, et al.
(författare)
-
Comparison of 2D and 4D Flow MRI in Neonates Without General Anesthesia
- 2023
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 57:1, s. 71-82
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundNeonates with critical congenital heart disease require early intervention. Four-dimensional (4D) flow may facilitate surgical planning and improve outcome, but accuracy and precision in neonates are unknown.PurposeTo 1) validate two-dimensional (2D) and 4D flow MRI in a phantom and investigate the effect of spatial and temporal resolution; 2) investigate accuracy and precision of 4D flow and internal consistency of 2D and 4D flow in neonates; and 3) compare scan time of 4D flow to multiple 2D flows.Study TypePhantom and prospective patients.PopulationA total of 17 neonates with surgically corrected aortic coarctation (age 18 days [IQR 11–20]) and a three-dimensional printed neonatal aorta phantom.Field Strength/SequenceA 5 T, 2D flow and 4D flow.AssessmentIn the phantom, 2D and 4D flow volumes (ascending and descending aorta, and aortic arch vessels) with different resolutions were compared to high-resolution reference 2D flow. In neonates, 4D flow was compared to 2D flow volumes at each vessel. Internal consistency was computed as the flow volume in the ascending aorta minus the sum of flow volumes in the aortic arch vessels and descending aorta, divided by ascending aortic flow.Statistical testsBland–Altman plots, Pearson correlation coefficient (r), and Student's t-tests.ResultsIn the phantom, 2D flow differed by 0.01 ± 0.02 liter/min with 1.5 mm spatial resolution and −0.01 ± 0.02 liter/min with 0.8 mm resolution; 4D flow differed by −0.05 ± 0.02 liter/min with 2.4 mm spatial and 42 msec temporal resolution, −0.01 ± 0.02 liter/min with 1.5 mm, 42 msec resolution and −0.01 ± 0.02 liter/min with 1.5 mm, 21 msec resolution. In patients, 4D flow and 2D flow differed by −0.06 ± 0.08 liter/min. Internal consistency in patients was −11% ± 17% for 2D flow and 5% ± 13% for 4D flow. Scan time was 17.1 minutes [IQR 15.5–18.5] for 2D flow and 6.2 minutes [IQR 5.3–6.9] for 4D flow, P < 0.0001.Data ConclusionNeonatal 4D flow MRI is time efficient and can be acquired with good internal consistency without contrast agents or general anesthesia, thus potentially expanding 4D flow use to the youngest and smallest patients.Evidence Level1Technical EfficacyStage 2
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| 22. |
- Ström, Erik, 1965, et al.
(författare)
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Requirements and test methods for vehicular antenna systems supporting cooperative ITS applications
- 2015
-
Ingår i: IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM). - 9781479972159
-
Konferensbidrag (refereegranskat)abstract
- Antenna systems are crucial for the link performance of§ any wireless systems, including those supporting cooperative intelligent transport system (C-ITS) applications. It is therefore of great importance to define performance metrics that are relevant for C-ITS applications and a framework for measuring the metrics. In this paper, we propose to measure performance by cumulative distribution functions based on the output SNR of the antenna system under test. The SNR samples are collected with respect to the time scales relevant for C-ITS applications. The framework is suitable for both computer simulations and over-the-air measurements and can handle antenna systems that are time-varying and have multiple output ports.
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| 23. |
- Thunberg, Johan, 1982-, et al.
(författare)
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Efficiently Bounding the Probabilities of Vehicle Collision at Intelligent Intersections
- 2021
-
Ingår i: IEEE Open Journal of Intelligent Transportation Systems. - New York, NY : IEEE. - 2687-7813. ; 2, s. 47-59
-
Tidskriftsartikel (refereegranskat)abstract
- Intelligent intersections have the potential to serve as an integral part of tomorrow’s traffic infrastructure. Wireless communication is key to enabling such technology. We consider a scenario where two flows of vehicles are to traverse an intelligent intersection. We investigate safety in emergency braking scenarios, where one of the vehicles in a flow suddenly decides to emergency brake and emergency braking messages are broadcast to affected vehicles. We provide a framework for computing lower bounds on probabilities for safe braking – collisions between vehicles are to be avoided. If we require that a crash or collision, for example, occurs at most once in a million scenarios, our approach allows for computation of lower bounds on the time-varying (or distance-varying) packet loss probabilities to ensure this. One of the benefits of the proposed framework is that the computational time is reduced; eliminating, for example, the need for time-consuming Monte Carlo simulations.
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| 24. |
- Thunberg, Johan, 1982-, et al.
(författare)
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Vehicle-to-Vehicle Communications for Platooning : Safety Analysis
- 2019
-
Ingår i: IEEE Networking Letters. - Piscataway : Institute of Electrical and Electronics Engineers (IEEE). - 2576-3156. ; 1:4, s. 168-172
-
Tidskriftsartikel (refereegranskat)abstract
- Vehicle-to-vehicle (V2V) communication is the key technology enabling platooning. This paper proposes an analytical framework that combines the characteristics of V2V communication (packet loss probabilities and packet transmission delays) with the physical mobility characteristics of vehicles (speed, distance between vehicles and their brake capacities). First, we present the feasible region of communications delays which guarantees safe emergency braking in platooning scenarios. Second, we derive a bound on the probability of safe braking. The presented framework is applied to understand the performance of the state-of-the-art V2V communication protocol for platooning.
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