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In cognitive radio systems, the primary user location and transmit power are valuable information in order to create an efficient secondary network that uses spatial spectrum holes without introducing interference to the primary users. Since primary users cannot be assumed to cooperate, their locations and transmit powers need to be estimated at the secondary users. Existing localization techniques,...
This paper describes a few aspects of the work that led to the first experiments ever carried out on the road with an accident warning system based on vehicle-to-vehicle (V2V) communications. The mentioned experiments were performed in Los Angeles as part of a collaboration project between two teams, one from the University of Bologna and one from UCLA. In essence, driving along a few of the most...
Mobile Vehicular Clouds are emerging as systems architectures suitable to provide services to both drivers and external customers. The paper describes a Pics-on-Wheel architecture and prototype implementation based on the idea of open mobile cloud. A simulation study based on San Francisco taxi cab traces shows that the Pics-on-Wheel service yields latencies in the order of 5 minutes in well frequented...
The design of emerging multi-tier dense wireless networks, which integrate opportunistically deployed devices into legacy infrastructure networks, will hugely benefit from a thorough understanding of the spatial structure of existing large-scale unplanned deployments. However, detailed and precise datasets which would enable acquiring such knowledge are unavailable and non-trivial to generate. In...
Due to the increasing deployment of city-wide IEEE 802.11 networks for nomadic Internet access, there is a great potential for users wanting to access the network while being on the move. However, due to the limited coverage range of single access points in these networks, handovers between them need to be carefully managed. This issue becomes critical if we consider vehicular users, where the high...
We study the feasibility of multi-channel beaconing for efficient data dissemination in vehicular networks. Beaconing, i.e., sending small one-hop broadcasts in a periodic fashion, is now a state of the art method for information dissemination in vehicular networks. The main research challenge is to minimize the communication delay while efficiently using the wireless medium without ever overloading...
Available simulation studies on communication performance of Vehicular Ad-Hoc Networks (VANETs) in highway scenarios are based on different propagation models, often without empirical validation. In this paper, we present the results of a 5.9 GHz vehicle-to-vehicle (V2V) highway measurement campaign using commercial off-the-shelf hardware to gain insights into adequate path loss modeling. As most...
Our society is highly dependent on mobile communications. However, coverage to mobile devices may be inadequate in a variety of infrastructure and outage circumstances. In particular, in disaster scenarios both victims and rescuers need network access to the outside world to aid in the search and rescue operation, while local wireless infrastructures may have been damaged. A hybrid mobile ad hoc network...
Information about primary user (PU) location can enable several key capabilities in cognitive radio (CR) networks. In this paper we consider PU localization using received-signal-strength (RSS) and direction-of-arrival (DoA) estimates from sectorized antenna. Abstracting from practical antenna types, we define a sectorized antenna as an antenna that can be set to different operating modes, each of...
In this paper we explore the interplay of node density, mobility and cooperation in routing decisions for mobile networks. Specifically, routing is based on a novel metric that jointly accounts for all three aforementioned attributes and helps identify the most promising venue available for getting the message closer/faster to the destination, even in dynamically changing environments. The effectiveness...
This paper investigates a novel solution for efficiently broadcasting in vehicular networks. In high congested traffic scenarios, one of the most serious problems is the increase of packet collisions and medium contentions among vehicles which attempt to communicate. The effect results in a very high number of message copies and collisions within the vehicular network, which is sometimes called as...
This paper deals with the problem of modeling shadow fading for wireless links in mobile ad-hoc networks (MANET). In contrast to broadcasting or cellular applications, the links in a MANET generally cannot be analyzed indepen-dently. Thus the evaluation of routing techniques and network protocols for future systems requires a realistic modeling of the correlation of the links. In the following a novel...
The support of LTE for vehicular safety applications has been studied in recent years. One problem is the bandwidth capability of LTE to support regularly transmitted cooperative awareness messages. In this paper, we discussed the effect of different scheduling methods on cooperative message transmissions. The capacity of dedicated connection has been analyzed and compared with different configurations...
In monitoring scenarios, Wireless Sensor Networks commonly transmit measurements from a large number of sensor nodes to a central data sink. This communication pattern is known as concast. Different approaches have been proposed to improve the energy-efficiency of concast and thus the lifetime of the WSN. However, energy-efficiency evaluations that are close to reality are missing. This paper systematically...
The rise of mixed mobile networks of WiFi, cellular small cells and traditional base stations, opens new challenges in optimising user's access to the networks. In fact, this mix of Radio Access Networks (RAN) become more heterogeneous as various technologies such as LTE, UMTS and WiMAX operates at the small cells. To fully utilise the capacity of such rich field of heterogeneous wireless connectivity,...
Multi-hop wireless networks, such as ad-hoc and mesh networks, suffer from inherent topology dynamics due to unstable wireless links and node mobility. Stable addressing, as needed for reliable routing, in such evolving, challenging network conditions is thus a difficult task. Efficient multi-hop wireless communication in these networks then requires a fully decentralized, scalable routable addressing...
In Delay-Tolerant Networks (DTN), individual nodes with much higher rates of sending new bundles than average can degrade the delivery rate of other nodes substantially. They have a much higher impact on the overall network fairness than in traditional networks because of DTN — specific properties, such as decentralized design and the store-and-forward approach. Authenticated resource management schemes...
Community urban sensing is one of the emerging applications enabled by the growing popularity of mobile user devices, like smartphones and in-vehicle monitoring systems. Such devices feature sensing and wireless communication capabilities, which enable them to sample large-scale phenomena, like air pollution and vehicular traffic congestion, and upload these data to the Internet. In this work, we...
Multicast video streaming is experiencing a significant growth in wireless networks thanks to the resources provided by 4G/LTE and WiFi services. However, wireless communications are affected by attenuation, shadowing, fading, and unpredictable interference, that make multicast services extremely difficult (no ARQ). Nodes close to the streaming source (e.g., a node or an AP), however, always experience...
For mobile delay-tolerant networks, different mobility models have been utilized to assess the performance of routing algorithms and applications. Substantial work has gone into understanding the contact characteristics of mobile users to allow evaluation under conditions that approximate the real world. One important finding has been recognizing that contacts humans make at a macroscopic level is...
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