Current Issue : April - June Volume : 2011 Issue Number : 2 Articles : 6 Articles
A joint vehicle-vehicle/vehicle-roadside communication protocol is proposed for cooperative collision avoiding in Vehicular Ad Hoc Networks (VANETs). In this protocol, emergency warning messages are simultaneously transmitted via Vehicle-to-Vehicle (V2V) and Vehicle-to-Roadside (V2R) communications in order to achieve multipath diversity routing. In addition, to further improve communication reliability and achieve low latency, a Multi-Channel (MC) technique based on two nonoverlapping channels for Vehicle-Vehicle (V2V) and V2R (or R2V) is proposed. The simulation results demonstrate that the proposed joint V2V/V2R (R2V) communication protocol is capable of improving the message delivery ratio and obtaining low latency, which are very important merits for highway traffic safety....
The problem of distributing a large amount of data from multiple sources in an urban area is investigated. We explore an opportunistic approach for information collection, in which a vehicle obtains information about resources from encountered vehicles. This protocol could be applied in both dense and sparse vehicular networks. Due to the highly dynamic nature of the underlying vehicular network topology, we depart from architectures requiring centralized coordination, reliable MAC scheduling, or global network state knowledge, and instead adopt a distributed paradigm with simple protocols. In other words, a reliable dissemination is introduced from multiple sources when each node in the network shares a limited amount of its resources for cooperating with others. By using rateless coding at the Road Side Unit (RSU) and using vehicles as data carriers, an efficient way to achieve reliable dissemination to all nodes (even disconnected clusters in the network) is described....
Micro- and nano air vehicles are defined as ââ?¬Å?extremely small and ultra-lightweight air vehicle systemsââ?¬Â with a maximum wingspan length of 15?cm and a weight less than 20 grams. Here, we provide a review of the current state of the art and identify the challenges of design and fabrication. Different configurations are evaluated, such as fixed wings, rotary wings, and flapping wings. The main advantages and drawbacks for each typology are identified and discussed. Special attention is given to rotary-wing vehicles (helicopter concept); including a review of their main structures, such as the airframe, energy storage, controls, and communications systems. In addition, a review of relevant sensors is also included. Examples of existing and future systems are also included. Micro- and nano-vehicles with rotary wings and rechargeable batteries are dominating. The flight times of current systems are typically around 1 hour or less due to the limited energy storage capabilities of the used rechargeable batteries. Fuel cells and ultra capacitors are promising alternative energy supply technologies for the future. Technology improvements, mainly based on micro- and nanotechnologies, are expected to continue in an evolutionary way to improve the capabilities of future micro- and nano air vehicles, giving improved flight times and payload capabilities....
We construct strict Lyapunov functions for fully nonlinear slowly time-varying Lipschitz systems. The Lyapunov functions about input-to-state stable to a closed invariant set for slowly time-varying lipschitz control systems also be constructed....
Recent advancement in vehicular wireless applications is also a major contributing factor in spectrum scarcity. Cognitive radio system is a mechanism which allows unlicensed cognitive users (CUs) to utilize idle unused bands. Fast and reliable detection of primary legacy user is the key component of cognitive radio networks. However, hidden terminal and low SNR problems due to shadow fading put fundamental limit to the sensing performance and practical entailments in design of the cognitive vehicular networks. Extensive modeling is being carried out to specify varying channel characteristics, particularly multipath fading and shadowing. Energy detection-(ED-) based spectrum sensing is a viable choice for many vehicle-to-vehicle (V2V) and vehicle to-road-side infrastructure (V2I) communications. This paper examines the performance of spectrum sensing using ED over Gamma-shadowed Nakagami-m composite fading channel to cater for both small-and-large scale fading. The results highlight the notable impact of shadowing spread and fading severity on detection performance. The relevant simulation results are presented to support our analytical results for average detection probability. Furthermore, these results are investigated and compared to other compound and classical channels....
In recent times, the number of vehicles with a rear-view camera has been increasing. The rear-view camera can be utilized as a sensor for monitoring a collision from behind the vehicle in a driving scene. To prevent rear-end collisions, we have been developing a technology that detects approaching vehicles from images obtained using an onboard rear-view camera. In conventional vehicle detection methods, often, camera-view images are used. However, it is difficult to accurately estimate the position of a distant approaching vehicle using such images. In this paper, we propose an improved method to accurately estimate the position of distant approaching vehicles by using virtual top-view images. The displacement of the vehicle in the top-view image is proportional to its speed. Thus, the proposed method can provide the accurate position of the distant vehicle. We describe the details of the proposed method and its availability by the experiment using actual images....
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