Delay-Tolerant ICN and Its Application to LoRa

Connecting long-range wireless networks to the Internet imposes challenges due to vastly longer round-trip-times (RTTs). In this paper, we present an ICN protocol framework that enables robust and efficient delay-tolerant communication to edge networks. Our approach provides ICN-idiomatic communication between networks with vastly different RTTs. We applied this framework to LoRa, enabling end-to-end consumer-to-LoRa-producer interaction over an ICN-Internet and asynchronous data production in the LoRa edge. Instead of using LoRaWAN, we implemented an IEEE 802.15.4e DSME MAC layer on top of the LoRa PHY and ICN protocol mechanisms in RIOT OS. Executed on off-the-shelf IoT hardware, we provide a comparative evaluation for basic NDN-style ICN [60], RICE [31]-like pulling, and reflexive forwarding [46]. This is the first practical evaluation of ICN over LoRa using a reliable MAC. Our results show that periodic polling in NDN works inefficiently when facing long and differing RTTs. RICE reduces polling overhead and exploits gateway knowledge, without violating ICN principles. Reflexive forwarding reflects sporadic data generation naturally. Combined with a local data push, it operates efficiently and enables lifetimes of >1 year for battery powered LoRa-ICN nodes.Comment: 12 pages, 7 figures, 2 table

Variation in stem mortality rates determines patterns of above-ground biomass in Amazonian forests: implications for dynamic global vegetation models

This is the final version of the article. Available from Wiley via the DOI in this record.Understanding the processes that determine above-ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. The relationship between stem mortality rates and AGB varies among different regions of Amazonia, indicating that variation in wood density and height/diameter relationships also influences AGB. In contrast to previous findings, we find that woody NPP is not correlated with stem mortality rates and is weakly positively correlated with AGB. Across the four models, basin-wide average AGB is similar to the mean of the observations. However, the models consistently overestimate woody NPP and poorly represent the spatial patterns of both AGB and woody NPP estimated using plot data. In marked contrast to the observations, DGVMs typically show strong positive relationships between woody NPP and AGB. Resolving these differences will require incorporating forest size structure, mechanistic models of stem mortality and variation in functional composition in DGVMs.This paper is a product of the European Union's Seventh Framework Programme AMAZALERT project (282664). The field data used in this study have been generated by the RAINFOR network, which has been supported by a Gordon and Betty Moore Foundation grant, the European Union's Seventh Framework Programme projects 283080, ‘GEOCARBON’; and 282664, ‘AMAZALERT’; ERC grant ‘Tropical Forests in the Changing Earth System’), and Natural Environment Research Council (NERC) Urgency, Consortium and Standard Grants ‘AMAZONICA’ (NE/F005806/1), ‘TROBIT’ (NE/D005590/1) and ‘Niche Evolution of South American Trees’ (NE/I028122/1). Additional data were included from the Tropical Ecology Assessment and Monitoring (TEAM) Network – a collaboration between Conservation International, the Missouri Botanical Garden, the Smithsonian Institution and the Wildlife Conservation Society, and partly funded by these institutions, the Gordon and Betty Moore Foundation, and other donors. Fieldwork was also partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico of Brazil (CNPq), project Programa de Pesquisas Ecológicas de Longa Duração (PELD-403725/2012-7). A.R. acknowledges funding from the Helmholtz Alliance ‘Remote Sensing and Earth System Dynamics’; L.P., M.P.C. E.A. and M.T. are partially funded by the EU FP7 project ‘ROBIN’ (283093), with co-funding for E.A. from the Dutch Ministry of Economic Affairs (KB-14-003-030); B.C. [was supported in part by the US DOE (BER) NGEE-Tropics project (subcontract to LANL). O.L.P. is supported by an ERC Advanced Grant and is a Royal Society-Wolfson Research Merit Award holder. P.M. acknowledges support from ARC grant FT110100457 and NERC grants NE/J011002/1, and T.R.B. acknowledges support from a Leverhulme Trust Research Fellowship

Poster: DSME-LoRa : A Flexible MAC for LoRa

LoRa is a popular technology that enables long-range wireless communication (kilometers) at low energy consumption. The transmission exhibits low throughput and underlies duty cycle restrictions. Long on-air times (up to seconds) and range are susceptible to interference. In parallel, common LoRa-devices are battery driven and should mainly sleep. LoRaWAN is the system that defines the LoRa PHY, MAC, and a complete vertical stack. To deal with the above limitations, LoRaWAN imposes rigorous constraints, namely, a centralized network architecture that organizes media access, and heavily reduced downlink capacity. This makes it unusable for many deployments, control systems in particular. In this work, we combine IEEE 802.15.4 DSME and LoRa to facilitate node-to-node communication. We present a DSME-LoRa mapping scheme and contribute a simulation model for validating new LoRa use-cases. Our results show 100% packet delivery and predictable latencies irrespective of network size

WIP: Exploring DSME MAC for LoRa : A System Integration and First Evaluation

LoRa is a popular wireless technology that enables low-throughput (bytes) long-range communication (km) at low energy consumption (mW). Its transmission, though, is on one side prone to interference during long on-air times, and on the other side subject to duty cycle restrictions. LoRaWAN defines a MAC and a vertical stack on top of LoRa. LoRaWAN circumvents the above limitations by imposing a centralized network architecture, which heavily reduces downlink capacity and prevents peer-to-peer communication. This makes it unusable for many deployments. The Deterministic and Synchronous Multichannel Extension (DSME) of IEEE 802.15.4e benefits of time-slotted communication and peer-to-peer communication and has the potential to overcome LoRaWAN limitations. In this work, we implement DSME on top of LoRa in the open source IoT OS RIOT and open the field for first evaluation experiments on real hardware. Initial results indicate that DSME-LoRa not only enables reliable peer-to-peer communication for constrained IoT devices, but also scales with an increasing number of nodes

Results of investigation at the Miravalles geothermal field, Costa Rica. Resultados de las investigaciones en el campo geotermico de Miravalles, Costa Rica; Parte 2, Muestreo de fluidos pozo abajo

Samples of the geothermal fluids in the Miravalles, Costa Rica, geothermal system were collected from production wellbores using downhole fluid samplers, from flowing wellheads using miniseparators, and from hot springs that discharge in the area. The reservoir fluid at Miravalles is a neutral-chloride-type water, but fumaroles and acid-sulfate springs are present within the main thermal area, and there are bicarbonate-rich hot springs that are clearly related to the neutral-chloride reservoir fluids. Dissolved gases are primarily a mixture of CO{sub 2} with air, but samples collected in the fumarolic areas also contain H{sub 2}S. Water-stable isotope analyses suggest local meteoric recharge, and the reservoir fluid shows oxygen isotopic shifts of about 2.5% due to high-temperature oxygen exchange between water and rock. Chemical geothermometer temperatures are consistent with the measured downhole temperature of 220{degrees} to 255{degrees}C. This pattern of neutral-chloride reservoir fluids with acid-sulfate springs near the source region and bicarbonate-rich chloride hot springs at the periphery of the system suggests a lateral outflow type of hydrothermal system. In addition to the geochemical evidence, temperature profiles from several of the wells show temperature reversals that are characteristic of lateral outflow plumes. We find no evidence for the underlying, higher temperature (300{degrees}C) system, which has been suggested by other investigators. 24 refs., 14 figs., 6 tabs

The new metals and alloys compilation, a powerful materials analysis tool

A new compilation of Metals and Alloys indexes of powder diffraction and structural data has been completed. This compilation is designed to make characterization of metallic and related nonmetallic materialsl easier and more accurate. To achieve these goals, the existing Metals and Alloys Powder Diffraction File (M A PDF) contents were greatly increased to make the M A PDF contents similar to standard metallurgical references. Then six new indexes based on the M A PDF were developed

Magnetic ordering in (Y sub 1-x Pr sub x )Ba sub 2 Cu sub 3 O sub 7 as evidenced by muon spin relaxation

Using the zero-field-muon-spin-relaxation ({mu}SR) technique we have found clear evidence for antiferromagnetic ordering of Cu moments within the CuO planes of (Y{sub 1-x}Pr{sub x})Ba{sub 2}Cu{sub 3}O{sub 7}. The Neel temperatures are approximately 285 K, 220 K, 35 K, 30 K, and 20 K for x = 1, 0.8, 0.6, 0.58, and 0.54, respectively. For x = 0.50 we observe a fast-relaxing component of the muon polarization in addition to a long-time tail, reminiscent of spin-glass behavior. This region of the phase diagram (0.5{le}x{le}0.54) corresponds to the existence of both superconductivity and magnetism. The fully developed local magnetic field for x>0.54 is found to be {approximately}16 mT, but decreased to {approximately}12 mT at T = 17 K for the x = 1 sample, presumably due to the onset of Pr-ion ordering. Magnetic ordering also occurs in PrBa{sub 2}Cu{sub 3}O{sub 6}; the Neel temperature is {approximately}325 K. 7 refs., 4 figs