312 research outputs found
Cross-Layer Radio Resource Allocation for Multicarrier Air Interfaces in Multicell Multiuser Environments
Performance analysis of multi-hop framed ALOHA systems with virtual antenna arrays
We consider a multi-hop virtual multiple-input-multiple-output system, which uses the framed ALOHA technique to select the radio resource at each hop. In this scenario, the source, destination and relaying nodes cooperate with neighboring devices to exploit spatial diversity by means of the concept of virtual antenna array. We investigate both the optimum number of slots per frame in the slotted structure and once the source-destination distance is fixed, the impact of the number of hops on the system performance. A comparison with deterministic, centralized re-use strategies is also presented. Outage probability, average throughput, and energy efficiency are the metrics used to evaluate the performance. Two approximated mathematical expressions are given for the outage probability, which represent lower bounds for the exact metric derived in the paper
Asymptotics of the Packet Speed and Cost in a Mobile Wireless Network Model
An infinite number of nodes move on R^2 according
to a random waypoint model; a single packet is traveling
towards a destination (located at an infinite distance away) using
combinations of wireless transmissions and physical transport
on the buffers of nodes. In earlier work [1] we defined two
performance metrics, namely, the long-term average speed with
which the packet travels towards its destination, and the rate
with which transmission cost accumulates with distance covered.
Analytical expressions were derived for these metrics, under
specific ergodicity assumptions. In this paper we give a precise
description of the induced Markov process, we show that it is
indeed (uniformly) geometrically ergodic, and that the law of
large numbers holds for the random variables of interest. In
particular, we show that the two performance metrics are well-
defined and asymptotically constant with probability one.European Union’s
Horizon 2020 Research and Innovation programme under
grant agreement No. 645220 (Road-, Air- and Water-based
Future Internet Experimentation - RAWFIE)
On the performance of a uav-aided wireless network based on nb-iot
In recent years, interest in Unmanned Aerial Vehicles (UAVs) as a means to provide wireless connectivity has substantially increased thanks to their easy, fast and flexible deployment. Among the several possible applications of UAV networks explored by the current literature, they can be efficiently employed to collect Internet-of-Things (IoT) data because the non-stringent latency and small-size traffic type is particularly suited for UAVs’ inherent characteristics. However, the implications coming from the implementation of existing technology in such kinds of nodes are not straightforward. In this article, we consider a Narrow Band IoT (NB-IoT) network served by a UAV base station. Because of the many configurations possible within the NB-IoT standard, such as the access structure and numerology, we thoroughly review the technical aspects that have to be implemented and may be affected by the proposed UAV-aided IoT network. For proper remarks, we investigate the network performance jointly in terms of the number of successful transmissions, access rate, latency, throughput and energy consumption. Then, we compare the obtained results on different and known trajectories in the research community and study the impact of varying UAV parameters such as speed and height. Moreover, the numerical assessment allows us to extend the discussion to the potential implications of this model in different scenarios. Thus, this article summarizes all the main aspects that must be considered in planning NB-IoT networks with UAVs
Trajectories and resource management of flying base stations for C-V2X
In a vehicular scenario where the penetration of cars equipped with wireless communication devices is far from 100% and application requirements tend to be challenging for a cellular network not specifically planned for it, the use of unmanned aerial vehicles (UAVs), carrying mobile base stations, becomes an interesting option. In this article, we consider a cellular-vehicle-to-anything (C-V2X) application and we propose the integration of an aerial and a terrestrial component of the network, to fill the potential unavailability of short-range connections among vehicles and address unpredictable traffic distribution in space and time. In particular, we envision a UAV with C-V2X equipment providing service for the extended sensing application, and we propose a UAV trajectory design accounting for the radio resource (RR) assignment. The system is tested considering a realistic scenario by varying the RRs availability and the number of active vehicles. Simulations show the results in terms of gain in throughput and percentage of served users, with respect to the case in which the UAV is not present
Performance evaluation of the dynamic trajectory design for an unmanned aerial base station in a single frequency network
Using an Unmanned Aerial Base Station (UABS) i.e., a base station carried by a UAV (Unmanned Aerial Vehicle) or drone, is a promising approach to offer coverage and capacity to those users that are not being served by the base stations of the terrestrial network. In this paper, we propose an approach to the design of the drone's trajectory to account for the quickly varying user traffic and pattern. This approach is based on the identification of clusters made of nearby users to be served. The decision on which cluster to visit next by the UABS depends on a cost-function considering the distance to the next cluster, the user density and spread in the cluster, and the direction compared to the previously visited cluster. Furthermore, we propose a radio resource assignment algorithm to minimize the interference from the UABS to the terrestrial network when both are operating in the same frequency band. The potential improvements in terms of network capacity (sum throughput) and user satisfaction are estimated in this study
Bluetooth or 802.15.4 technologies to optimise lifetime of wireless sensor networks: Numerical comparison under a common framework
This paper aims at comparing through simulations the network lifetime of a wireless sensor network using Bluetooth-enabled or IEEE802.15.4 compliant devices. The evaluation is performed under a common reference framework, namely the EMORANS scenario for wireless sensor networks. Since the two enabling technologies rely on different MAC paradigms, suitable definition of the performance metrics is needed, in order to make the comparison meaningful. Thus, the paper has also a methodological objective. In particular, three different definitions of network lifetime are introduced, and a comparison of performance obtained by applying the different definitions is provided. Then, the comparison between the two standards is introduced: it is shown that there are no orders of magnitude of difference in network lifetime when the two technologies are used and the choice of the technology depends on the application requirements
Optimizing investments in national-scale forest landscape restoration in Uganda to maximize multiple benefits
Forest loss and degradation globally has resulted in declines in multiple ecosystem services and
reduced habitat for biodiversity. Forest landscape restoration offers an opportunity to mitigate these
losses, conserve biodiversity, and improve human well-being. As part of the Bonn Challenge, a global
effort to restore 350 million hectares of deforested and degraded land by 2030, over 30 countries have
recently made commitments to national forest landscape restoration. In order to achieve these goals,
decision-makers require information on the potential benefits and costs of forest landscape
restoration to efficiently target investments. In response to this need, we developed an approach using
a suite of ecosystem service mapping tools and a multi-objective spatial optimization technique that
enables decision-makers to estimate the potential benefits and opportunity costs of restoration,
visualize tradeoffs associated with meeting multiple objectives, and prioritize where restoration could
deliver the greatest benefits.Wedemonstrate the potential of this approach in Uganda, one of the
nations committed to the Bonn Challenge. Using maps of the potential benefits and costs of
restoration and efficiency frontiers for optimal restoration scenarios, we were able to communicate
how ecosystem services benefits vary spatially across the country and how different weights on
ecosystem services objectives can affect the allocation of restoration across Uganda. This work
provides a generalizable approach to improve investments in forest landscape restoration and
illuminates the tradeoffs associated with alternative restoration strategies.UKAid from the UK
government through the International Union for
Conservation of Nature’s KnowFor program as well as by the Natural Capital Project, a partnership between
the University of Minnesota, Stanford University, the
World Wildlife Fund, and the Nature Conservancy.
MG was supported by the National Research Foundation
of South Africa (Grant Number 98889).http://http://iopscience.iop.org1748-9326am2017Plant Scienc
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