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Recent studies demonstrate that Cognitive Radio (CR) technology can increase the spectrum efficiency of wireless systems, provided that the activity of primary users (PUs) must be carefully protected. For this reason, several sensing schemes leverage the cooperation among nodes to increase the accuracy of PU detection. In this paper, we propose to employ the CR principles in the vehicular environment...
In ad hoc networks the broadcast nature of the radio channel poses a unique challenge because the wireless links have time-varying characteristics in terms of link capacity and link-error probability. In mobile networks, particularly in vehicular ad hoc networks (VANETs), the topology is highly dynamic due to the movement of the nodes, hence an on-going session suffers frequent path breaks. In this...
Vehicle Ad Hoc Networks (VANET) may exhibit different behavior depending on traffic and the time of day. Consider the potential worm attack in time-variant VANET channel, we use measured vehicle traffic data to model VANET worm spreading and patching. We also discuss the contributing factors for the differences observed.
In vehicular ad-hoc networks, status update messages are used to disseminate vehicle state information so that each vehicle can track movements of its neighbors. In this paper, we focus on the aggregated power level from this kind of active safety messages and its impact on DSRC channel quality. With macroscopic model and LWR (Lighthill-Whitham-Richards) PDE, we show how the probability distribution...
The success of VANET safety mechanisms, e.g. pre-crash warning and collaborative collision avoidance, relies on good proximity-awareness of each subject vehicle. Prior analysis shows that a self-information dissemination control on each car, which adapts communication rate based on estimation error and channel congestion, can achieve higher tracking accuracy than others in a multi-access channel....
This paper focuses on the mathematical analysis of two forwarding schemes in Vehicle Ad Hoc Networks (VANETs): Position-Based Routing (PBR) and Contention-Based Forwarding (CBF). Although PBR and CBF have been intensively studied, most of the work was based on simulations without in-depth mathematical analysis. It is well known that the received power at a receiver in VANETs is stochastic, thus, there...
We derive analytical bounds for the maximum acceptable message delivery latency and the minimum required retransmission frequency of 802.11-based vehicle-to-vehicle (V2V) communication protocols for rear-end collision avoidance applications. Using a microscopic car-following model of highway traffic combined with a probabilistic two-ray ground propagation model of the V2V wireless channel, we numerically...
In this contribution, we estimate the spatial diversity order and spatial correlations from channel sounder measurements of doubly-selective vehicle-to-vehicle MIMO radio channels in the 5.2 GHz band. Ivrlac and Nossek [1] have defined a diversity measure for MIMO Rayleigh fading channels which is based on the spatial correlations of the channel. Subsequently, Nabar et al. [2] have shown the existence...
An experimental study of the Doppler coherence time properties of Vehicle-to-Vehicle (V2V) wireless channels at 5.9 GHz in both rural and highway environments is presented. Simultaneous RF and mobility measurements were conducted in environments near Pittsburgh, Pennsylvania. The average Doppler spread was observed to depend linearly on effective speed, defined as the square root of the sum of the...
In this article, we have reported experimental studies of signal strength as a function of vehicle separation for outdoor vehicle-to-vehicle propagation at 5.9 GHz. Statistical measurement campaigns were conducted in highway and rural driving environments. These measurements were used to obtain parameters for a dual-slope log-normal propagation model. The effects of antenna pattern variations for...
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