Jouni Tervonen

Performance Analysis and Comparison of Bluetooth Low Energy with IEEE 802.15.4 and SimpliciTI

Bluetooth Low Energy (BLE) is a recently developed energy-efficient short-range wireless communication protocol. In this paper, we discuss and compare the maximum peer-to-peer throughput, the minimum frame turnaround time, and the energy consumption for three protocols, namely BLE, IEEE 802.15.4 and SimpliciTI. The specifics and the main contributions are the results both of the theoretical analysis and of the empirical measurements, which were executed using the commercially available hardware transceivers and software stacks. The presented results reveal the protocols’ capabilities and enable one to estimate the feasibility of using these technologies for particular applications. Based on the presented results, we draw conclusions regarding the feasibility and the most suitable application scenarios of the BLE technology.

Improved models for long-term prediction of tropospheric scintillation on slant paths

The prediction models for tropospheric scintillation on Earth-satellite paths from Karasawa, Yamada, and Allnutt (1988) and the ITU-R are compared with measurement results from satellite links in Europe, the United States, and Japan at frequencies from 7 to 30 GHz and elevation angles of 3 to 33/spl deg/. The existing prediction models relate the long-term average scintillation intensity to the wet term of refractivity at ground level. The comparison shows that the seasonal variation of scintillation intensity is well predicted by this relation, but for the annual average some additional meteorological information is needed. A much better agreement with measurement results is found when a parameter representing the average water content of heavy clouds is incorporated. This confirms the assumption that scintillation is, at least partly, associated with turbulence inside clouds. The asymmetry between the distributions of signal fade and enhancement can also be explained by turbulence inside clouds. The asymmetry depends on the intensity of the scintillation, which is consistent with the theory assuming a thin layer of cloudy turbulence. A new model based on this theory predicts the distributions of signal fade and enhancement significantly better.

Prediction model for the diurnal behavior of the tropospheric scintillation variance

Tropospheric scintillation is caused by variations of the refractive index due to turbulence. The only meteorological input parameter for two common current scintillation models by Karasawa et al. (1988) and by the ITU-R is the monthly average of the wet part of the refractivity N/sub wet/ at ground level, which is not directly associated with turbulence. The diurnal correlation between N/sub wet/ and scintillation variance is very weak. Because clouds and cloud formation are closely associated with the turbulence, quantitative cloud parameters were looked for. Cloud type information based on edited synoptic cloud reports are available from the common database of CDIAC and NCAR. Both diurnal and seasonal variations between scintillation variance and average amount of Cumulus type clouds are well correlated. Using this cloud information together with N/sub wet/, a new method for tropospheric scintillation variance predicting also the diurnal variations is introduced. This model is derived and tested using scintillation measurements at four sites in different climates in Finland, United Kingdom, Japan, and Texas.

Multihop data transfer service for Bluetooth Low Energy

Bluetooth Low Energy (BLE) is one of the recently developed protocols enabling energy-efficient short-range radio communication. One of limitations of BLE is the support for data transferring over only a single hop. In the paper, we suggest the mechanism enabling the multihop data transfers between the nodes in BLE networks. To ensure portability, the suggested mechanism is designed as BLE service, which uses only the integral components of BLE stack. We discuss in details the suggested multihop service, its implementation and present the results of evaluation, which confirm feasibility and reveal features of the suggested solution. To the best of our knowledge, this paper reports the first implementation of the multihop data transfer over the BLE networks.

Frequency dependence of amplitude scintillation

In the prediction models of tropospheric scintillation on Earth-satellite paths from Karasawa, Yamada, and Allnutt and ITU-R, the frequency dependence of scintillation is expressed as a power law with a different exponent for each model. This is verified using a collection of measurement results from different satellite links in Europe, the US, and Japan at frequencies from 4 to 50 GHz and elevation angles from 2.5 to 52/spl deg/. It shows that the exponent of the power law varies widely among the results from the different sites. Possible explanations of this are: (1) the frequency dependence of scintillation due to cloudy turbulence is different from that due to clear-sky turbulence and this kind of scintillation may be present to different extents in the various databases due to climatic differences and different clear-sky selection procedures or (2) angle-of-arrival fluctuations due to turbulence have a different frequency dependence and this effect may have some impact on the measured scintillation at some of the sites.

Semi-infrastructured mobile ad-hoc mesh networking

The paper presents the role and architectural views of ad-hoc mesh networking in extending the edge-coverage of the future mobile networks. The key architectural principles and elements of the ad-hoc mesh networks when integrated to the legacy networks and forming the semi-infrastructured ad-hoc networks are introduced. Placement of the ad-hoc mesh networks in the future network environment and the enabling technologies that practically could realize them are outlined. The reasons that make the ad-hoc networking technology attractive for extending the coverage of the future mobile networks are introduced. Finally, the performance comparison of the ad-hoc mesh networking vs. point-to-multipoint (PMP) has been evaluated by simulation results.

Optimization of microcontroller hardware parameters for Wireless Sensor Network node power consumption and lifetime improvement

In this article the results for study of the influence of different microcontroller hardware parameters on the system overall power consumption and thus also on the system lifetime are presented. The influence of the supply voltage, clock frequency and emplacement of the program in the microcontroller memory for MSP430 microcontroller, which is often used nowadays in Wireless Sensor Networks (WSN) nodes, were evaluated. Additionally, we have studied the influence of different power supply systems for the node lifetime and figured out the optimal microcontroller working mode parameters, which allowed to maximize the amount of microcontroller operations for power supply charge using a normal battery and an energy harvesting system based on light energy harvesting. Although the motivation of this article has been the requirements of energy efficient WSN solutions obtained results are as well applicable to any microcontroller based embedded system that is working in harsh energy conditions.

Backward and forward scattering by the melting layer composed of spheroidal hydrometeors at 5-100 GHz

This paper addresses the behavior of the differential reflectivity, specific attenuation, and specific phase shift due to a melting layer composed of oblate-spheroidal hydrometeors. The results are based on a melting layer model and scattering computations derived from the point-matching technique with the truncation and recurrence adjusted. Computations at 5-100 GHz for five raindrop size distributions at rain rates below 12.5 mm/h are presented. In general, the reflectivity factor and differential reflectivity features with height at centimeter wavelengths agree with available radar measurements. At millimeter wavelengths, contributions to the radar backscatter from smaller hydrometeors become more and more important as the frequency increases and approaches 100 GHz. This should be instructive for utilizing millimeter wavelength radar techniques in radar remote sensing studies of the melting layer. Corresponding vertical profiles of the specific attenuation and phase shift are also presented at 5-100 GHz. The differential attenuation and phase shift indicate the particle shape effects. These attenuation and phase shift become more and more considerable as the frequency increases. Such forward scattering calculations should prove useful for studying propagation effects caused by the melting layer for satellite-earth communications, including depolarizations.

Scintillation effects on total fade distributions for Earth-satellite links

Scintillation effects on the cumulative fade distributions for Earth-satellite links are considered. Two combination methods for scintillation and attenuation distributions are compared using filtered and unfiltered 11.2 GHz beacon measurements from Austin, TX, on a 5.8/spl deg/ elevation path. A combination method based on the assumption of independent scintillation and attenuation phenomena is proposed. Attenuation and total fade distributions at 19.8 and 29.7 GHz from Kirkkonummi, Finland, on a 12.7/spl deg/ elevation path, are presented for a summer period. The effects of attenuation and scintillation are also calculated using meteorological data from several radiosonde stations. The calculations show that the relative significance of the scintillation is smaller at frequencies from 20 to 50 GHz than at 12 GHz.

Wireless Sensor Networks in industrial environment: Real-life evaluation results

The paper summarizes the results of the RealFusion project. One of the main objectives of this project was to study the Wireless Sensor Networks (WSN) in real-life industrial environment. The results for the evaluation of different radios utilizing 433 MHz, 868 MHz and 2.4 GHz license-free industrial, scientific and medical (ISM) bands in real-life industrial environment are presented in the paper. Also, the paper discusses the results of development and evaluation of two real-life industrial WSN use cases: the WSN for remote monitoring the amount of bulk substances in the silos of a refractory materials factory and the WSN for remote warehouse monitoring.