Current Issue : January - March Volume : 2016 Issue Number : 1 Articles : 6 Articles
The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel\ncommunication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V\nchannel models to be implemented in advanced VANET system simulators for performance evaluation.The impact of shadowing\ncaused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this\npaper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway\nscenarios.The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles,\nand non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that\nvehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to\nincorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results\nare presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading....
The application of unmanned aerial vehicles (UAV) for short range civilian applications has\nreached new dimensions with the advent of modern yet affordable autonomous guidance\nsystems. Low altitude light weight UAV systems were developed that have capability for\nsemi-autonomous and autonomous way point navigation with a payload of sensing system.\nWhile UAV I was utilized to test the feasibility of application with manual control using\nradio control and first person wireless video, UAV II was built for autonomous flight and\nfield data collection. With UAV II, in addition to an autopilot navigation system, a Global\nPositioning Satellite (GPS) receiver and fight stabilization sensors were utilized for system\nstability and guidance during completely autonomous flights. Both the UAVs successfully\nperformed in flight conditions for terrain mapping of property, range, agricultural and natural\nresource management with respect to initial test flights, flight parameter calibration and field\ntrials. In UAV II, average calibration parameters were +/-0.64 deg. for pitch, +/-3.35 deg. for\nroll in speed range of 40 - 50 mph indicating good flight stability. The UAVs were tested\nover a user set waypoint path on fields, facilities/properties, and urban locales, altitude\nranging 100 ft to 1000 ft, speed from 25 to 60 mph, and maneuvers including straight paths,\nturns, and banks. An autonomous image acquisition system was developed that records\nimages and videos with onboard sensors at specified time, frequency and coverage area. Georeferenced\naerial images were created to 4 in. resolution using mosaic images and post\nprocessing software. UAV I and UAV II maintained intended flight path parameters within\n55 ft. and 8.23 ft. spatial position or cross track error, respectively....
The article reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard.\nExperiments for both intra-vehicle and out-of-vehicle environments were carried out. It was observed that the\nlarge-scale variations (LSVs) of the power delay profiles (PDPs) can be best described through a two-term exponential\ndecay model, in contrast to the linear models which are suitable for popular ultra-wideband (UWB) systems operating\nin the 3- to 11-GHz band. The small-scale variations (SSVs) are separated from the PDP by subtracting the LSV and\ncharacterized utilizing logistic, generalized extreme value (GEV), and normal distributions. Two sample Kolmogorov-\nSmirnov (K-S) tests validated that the logistic distribution is optimal for in-car, whereas the GEV distribution serves\nbetter for out-of-car measurements. For each measurement, the LSV trend was used to construct the respective\nchannel impulse response (CIR), i.e., tap gains at different delays. Next, the CIR information is fed to an 802.11p\nsimulation testbed to evaluate the bit error rate (BER) performance, following a Rician model. The BER results strongly\nvouch for the suitability of the protocol for in-car as well as out-of-car wireless applications in stationary environments....
The vehicular ad hoc network (VANET) technology based on the approved IEEE 802.11p standard\nand the appendant inter-vehicle communication (IVC) has the potential to dramatically change the\nway transportation systems work. The fundamental idea is to change the individual behavior of\neach vehicle by exchanging information among traffic participants to realize a cooperative and\nmore efficient transportation system. Certainly, the evaluation of such systems is a comprehensive\nand challenging task in a real world test bed, therefore, simulation frameworks are a key tool to\nanalyze IVC. Several models are needed to emulate the real behavior of a VANET in all aspects as\nmuch realistically as necessary. The intention of this survey is to provide a comprehensive overview\nof publications concerning IVC simulations of the year 2013 and to see how IVC simulation\nhas changed since 2009. Based on this analysis, we will answer the following questions: What simulation\ntechniques are applied to IVC? Which aspects of IVS have been evaluated? What has\nchanged within five years of IVC simulations? We also take a closer look at commonly used software\ntools and discuss their functionality and drawbacks. Finally, we present open questions concerning\nIVC simulations....
Hybridization is the most promising vehicular technology to get significant improvements of the vehicle efficiency and performance\nin the short-term. Mechanical transmissions for hybrid vehicles are very often multiple modes transmission, which permit\nimproving the performance in different working conditions. In this context, optimal design and control of these transmissions are\na key point to improve the performance of the vehicles, and mathematical models which supports the design can play an important\nrole in this field. In this work, an approach for evaluating the performance of Output Compound Split e-CVT (electric Continuously\nVariable Transmission) in steady-state is proposed. This approach, in addition to a kinematic analysis of the device, leads to the\ncalculation of the internal power circulation modes and the efficiency of the device in different working conditions....
Vehicular ad hoc networks (VANETs) have been quite a hot research area in the last few years. Due to their unique characteristics\nsuch as high dynamic topology and predictable mobility, VANETs attract so much attention of both academia and industry. In\nthis paper, we provide an overview of the main aspects of VANETs from a research perspective. This paper starts with the basic\narchitecture of networks, then discusses three popular research issues and general research methods, and ends up with the analysis\non challenges and future trends of VANETs....
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