The emergence of the Internet of Things (IoT) and its applications has taken the attention of several researchers. In an effort to provide interoperability and IPv6 support for the IoT devices, the ...Internet Engineering Task Force (IETF) proposed the 6LoWPAN stack. However, the particularities and hardware limitations of networks associated with IoT devices lead to several challenges, mainly for routing protocols. On its stack proposal, IETF standardizes the RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks) as the routing protocol for Low-power and Lossy Networks (LLNs). RPL is a tree-based proactive routing protocol that creates acyclic graphs among the nodes to allow data exchange. Although widely considered and used by current applications, different recent studies have shown its limitations and drawbacks. Among these, it is possible to highlight the weak support of mobility and P2P traffic, restrictions for multicast transmissions, and lousy adaption for dynamic throughput. Motivated by the presented issues, several new solutions have emerged during recent years. The approaches range from the consideration of different routing metrics to an entirely new solution inspired by other routing protocols. In this context, this work aims to present an extensive survey study about routing solutions for IoT/LLN, not limited to RPL enhancements. In the course of the paper, the routing requirements of LLNs, the initial protocols, and the most recent approaches are presented. The IoT routing enhancements are divided according to its main objectives and then studied individually to point out its most important strengths and weaknesses. Furthermore, as the main contribution, this study presents a comprehensive discussion about the considered approaches, identifying the still remaining open issues and suggesting future directions to be recognized by new proposals.
The Internet of Things (IoT) is based on interconnection of intelligent and addressable devices, allowing their autonomy and proactive behavior with Internet connectivity. Data dissemination in IoT ...usually depends on the application and requires context-aware routing protocols that must include auto-configuration features (which adapt the behavior of the network at runtime, based on context information). This paper proposes an approach for IoT route selection using fuzzy logic in order to attain the requirements of specific applications. In this case, fuzzy logic is used to translate in math terms the imprecise information expressed by a set of linguistic rules. For this purpose, four Objective Functions (OFs) are proposed for the Routing Protocol for Low Power and Loss Networks (RPL); such OFs are dynamically selected based on context information. The aforementioned OFs are generated from the fusion of the following metrics: Expected Transmission Count (ETX), Number of Hops (NH) and Energy Consumed (EC). The experiments performed through simulation, associated with the statistical data analysis, conclude that this proposal provides high reliability by successfully delivering nearly 100% of data packets, low delay for data delivery and increase in QoS. In addition, an 30% improvement is attained in the network life time when using one of proposed objective function, keeping the devices alive for longer duration.
The Internet of Things (IoT) is an emerging paradigm that proposes the connection of objects to exchange information in order to reach a common objective. In IoT networks, it is expected that the ...nodes will exchange data between each other and with external Internet services. However, due to deployment costs, not all the network devices are able to communicate with the Internet directly. Thus, other network nodes should use Internet-connected nodes as a gateway to forward messages to Internet services. Considering the fact that main routing protocols for low-power networks are not able to reach suitable performance in the displayed IoT environment, this work presents an enhancement to the Lightweight On-demand Ad hoc Distance-vector Routing Protocol-Next Generation (LOADng) for IoT scenarios. The proposal, named LOADng-IoT, is based on three improvements that will allow the nodes to find Internet-connected nodes autonomously and dynamically, decreasing the control message overhead required for the route construction, and reducing the loss of data messages directed to the Internet. Based on the performed assessment study, which considered several number of nodes in dense, sparse, and mobility scenarios, the proposed approach is able to present significant results in metrics related to quality-of-service, reliability, and energy efficiency.
This paper presents the Intertropical Convergence Zone (ITCZ) as the possible source mechanism of the medium-scale traveling ionospheric disturbances (MSTIDs) propagating to the southeast direction ...over the South American region. Using the data collected by the GNSS dual-frequency receivers network from January 2014 to December 2019, detrended TEC maps were generated to identify and characterize 144 MSTIDs propagating southeastward over the South American low-latitude and equatorial region. We also used images from the Geostationary Operational Environmental Satellite (GOES) 13 and 16 in the infrared (IR) and water vapor (WV) channel, and reanalisys data from the National Centers for Environmental Prediction (NCEP) of the National Oceanic and Atmospheric Administration (NOAA) to study the daily features and seasonal migration of ITCZ. In the winter, when ITCZ migrates to the northern hemisphere around 10–15° N, 20 MSTIDs propagated southeastward. During summer, when the ITCZ lies within the continent, around 0–5° S 80 MSTIDs were observed to propagate southeastward; in the equinoxes (spring and fall), 44 MSTIDs were observed. Again, the MSTIDs propagating southeastward showed a clear seasonality of their local time dependence; in summer, the MSTIDs occurred frequently in the evening hours, whereas those in winter occurred during the daytime. We also found for the first time that the day-to-day observation of ITCZ position and MSTIDs propagation directions were consistent. With regard to these new findings, we report that the MSTIDs propagating southeastward over the South American region are possibly induced by the atmospheric gravity waves, which are proposed as being generated by the ITCZ in the troposphere. The mean distribution of the horizontal wavelength, period, and phase velocity are 698 ± 124 km, 38 ± 8 min, and 299 ± 89 m s−1, respectively. For the first time, we were able to use MSTID propagation directions as a proxy to study the source region.
Multicast improvement for LOADng in Internet of Things networks Sobral, José V.V.; Rodrigues, Joel J.P.C.; Rabêlo, Ricardo A.L. ...
Measurement : journal of the International Measurement Confederation,
December 2019, 2019-12-00, 20191201, 2019-12-01, Letnik:
148, Številka:
C
Journal Article
Recenzirano
Odprti dostop
•Novel mechanism to support multicast data forwarding for LOADng.•Construction of a multicast routing tree able to routing data both upward and downward.•Performance evaluation of the proposed ...solution through a real testbed.
The Lightweight On-demand Ad hoc Distance-vector Routing Protocol – Next Generation (LOADng) is an emerging routing solution for low-power wireless networks, which is receiving much attention and is being adopted in Internet of Things (IoT) networks. Although the current literature has introduced improvements to allow the protocol to fulfill the requirements of a higher set of IoT applications, the multicast support stills a deficiency of the protocol. Thus, to overcome this limitation, this study proposes a multicast improvement for LOADng. The proposal, named Multicast LOADng (M-LOADng) introduces a new route discovery process to enable the construction of a multicast routing tree and perform forwarding multicast data messages. The proposed solution also introduces mechanisms to reduce the control message overhead and increase the reliability of the route discovery process. Further, M-LOADng allows multicast data transmission in three different modes. The conducted experiments, through a real testbed, show that the proposed solution can reach a reliable and constant performance in terms of quality-of-service, energy consumption, and memory usage, even when increasing the multicast group size.
Routing protocols represent an important issue on the Internet of Things (IoT) scenarios since they are responsible for creating paths and forwarding data packets among the network nodes. In mobile ...IoT scenarios, the topology changes caused by the movement of nodes makes the work of routing protocols more difficult. Thus, the current IoT routing solutions tend to present strong limitations and a poor performance in these scenarios, generally requiring complex additional improvement to better support the mobility of the devices. In this context, the Lightweight On-demand Ad hoc Distance-vector Routing Protocol - Next Generation (LOADng), is an emerging solution for IoT networks that despite being adequate for a mobile environment due to its reactive functioning still lacks in performance. Thus, this paper proposes a novel solution to enhance the performance of LOADng in mobile IoT networks. The improved version, LOADng-IoT-Mob, introduces a mechanism that permits nodes to be aware of the availability of their neighbors through the harnessing of control messages. As a result, these nodes can shorten paths and avoid sending data packets through broken routes due to the movement of the nodes. Additionally, a short periodical control message is introduced, allowing the nodes to update their routing table, even with a low control message frequency. Furthermore, a new routing metric is proposed for creating routes based on the reliability of the link and proximity of the neighboring nodes. Finally, through computational simulations, the performance of the LOADng-IoT-Mob is studied under multiple scenarios varying the network size, the number of mobile devices, and maximum nodes' speed. The results obtained demonstrate the efficiency of the proposed solution in terms of packet delivery ratio, latency, and power and overhead efficiency, with a slight increase in memory consumption.
Mammal diversity affects carbon concentration in Amazonian soils. It is known that some species traits determine carbon accumulation in organisms (e.g., size and longevity), and are also related to ...feeding strategies, thus linking species traits to the type of organic remains that are incorporated into the soil. Trait diversity in mammal assemblages – that is, its functional diversity – may therefore constitute another mechanism linking biodiversity to soil organic matter (SOM) accumulation. To address this hypothesis, we analyzed across 83 mammal assemblages in the Amazon biome (Guyana), the elemental (by ED‐XRF and CNH analysis) and molecular (FTIR‐ATR) composition of SOM of topsoils (401 samples) and trait diversity (functional richness, evenness, and divergence) for each mammal assemblage. Lower mammal functional richness but higher functional divergence were related to higher content of carbonyl and aliphatic SOM, potentially affecting SOM recalcitrance. Our results might allow the design of biodiversity management plans that consider the effect of mammal traits on carbon sequestration and accumulation in soils.
Mammal diversity affects carbon concentration in soils, but the diversity of traits in mammal assemblages – that is, its functional diversity – may constitute another mechanism linking biodiversity to soil organic matter (SOM) accumulation. We found that lower mammal functional richness but higher functional divergence increases the content of carbonyl and aliphatic SOM, potentially affecting SOM recalcitrance. Our results might allow the design of biodiversity management plans that consider the effect of mammal traits on carbon sequestration and accumulation in soils.
Objectives
The aim of this study was to investigate the prevalence of oral and maxillofacial lesions among older adults (≥60 years) from representative regions in Brazil.
Design
Retrospective ...descriptive cross‐sectional study.
Setting
Biopsy records were obtained from the archives of four Brazilian referral centers of oral diagnosis between 2000 and 2016.
Participants
A total of 45,506 biopsy records of all patients were analyzed, of these 7,259 persons aged 60 and older were selected.
Measurements
Data such as gender, age, race, anatomical location, and histopathological diagnosis were collected and categorized. Pearson's chi‐square test (P < .005) was used to evaluate differences in the frequency of the several groups of oral lesions.
Results
Oral and maxillofacial lesions were diagnosed in 7,259 older people, including 59.4% women (P < .001) and 61.3% white patients (P = .07). The most commonly affected sites were the cheek mucosa (20.3%) and mandible (8.9%) (P < .001). Reactive and inflammatory lesions were the most common lesions, followed by neoplasms. Oral squamous cell carcinoma was the most prevalent neoplasm (83.4%) (P < .001).
Conclusion
Knowledge of oral diseases obtained from biopsy records provides more accurate data about the diagnosis and oral health of elderly patients. These indicators thus support the development of specific health policies for the prevention and treatment of oral and maxillofacial lesions that affect this population.
Biodiversity affects many ecosystem functions and services, including carbon cycling and retention. While it is known that the efficiency of carbon capture and biomass production by ecological ...communities increases with species diversity, the role of vertebrate animals in the carbon cycle remains undocumented. Here, we use an extensive dataset collected in a high-diversity Amazonian system to parse out the relationship between animal and plant species richness, feeding interactions, tree biomass and carbon concentrations in soil. Mammal and tree species richness is positively related to tree biomass and carbon concentration in soil-and the relationship is mediated by organic remains produced by vertebrate feeding events. Our research advances knowledge of the links between biodiversity and carbon cycling and storage, supporting the view that whole community complexity-including vertebrate richness and trophic interactions-drives ecosystem function in tropical systems. Securing animal and plant diversity while protecting landscape integrity will contribute to soil nutrient content and carbon retention in the biosphere.
PDF
