Search results for "Communication channel"
showing 10 items of 349 documents
A microcontroller-based portable electrocardiograph system
2004
The ambulatory acquisition and monitorization of electrocardiograms (ECG) under not controlled conditions, is a practice of paramount importance in cardiology diagnosis nowadays. The ECGs are acquired while patients develop their normal life, using a portable device. The storage capacity of such devices usually ranges from 24 to 48 hours. ne systems used to perform this task are the so-called Holter systems. In this paper we describe a low cost single channel Holter system, based on a microcontroller, to register the ECG signal continuously during up to 48 hours. This microcontroller system runs off batteries, and includes many peripherals such as a display, keyboard, serial interface, soli…
Exploiting programmable architectures for WiFi/ZigBee inter-technology cooperation
2014
The increasing complexity of wireless standards has shown that protocols cannot be designed once for all possible deployments, especially when unpredictable and mutating interference situations are present due to the coexistence of heterogeneous technologies. As such, flexibility and (re)programmability of wireless devices is crucial in the emerging scenarios of technology proliferation and unpredictable interference conditions. In this paper, we focus on the possibility to improve coexistence performance of WiFi and ZigBee networks by exploiting novel programmable architectures of wireless devices able to support run-time modifications of medium access operations. Differently from software…
Experiments on Longitudinal and Transverse Bedload Transport in Sine-Generated Meandering Channels
2021
Bedload grains in consecutive meandering bends either move longitudinally or across the channel centerline. This study traces and quantifies the grains’ movement in two laboratorial sine-generated channels, i.e., one with deflection angle θ0 = 30° and the other 110°. The grains originally paved along the channels are uniform in size with D = 1 mm and are dyed in various colors, according to their initial location. The experiments recorded the changes in the flow patterns, bed deformation, and the gain-loss distribution of the colored grains in the pool-bar complexes. We observed the formation of two types of erosion zones during the process of the bed deformation, i.e., Zone 1 in the foresi…
A comparison of Microtops II and satellite ozone measurements in the period 2001-2011
2013
Daily average total ozone Microtops measurements obtained during several campaigns conducted from 2001 to 2011 at latitudes from 31 to 68N and in different seasons are compared with satellite observations. The Microtops ozone is derived using different wavelength combinations (Channel I, 305.5/312.5. nm; Channel II, 312.5/320. nm; and Channel III, 305.5/312.5/320. nm). Satellite data from TOMS, OMI, GOME, and GOME-2 are used in the comparison. The three Microtops channels show a high correlation with the satellite retrievals. Channel I shows the best results and produces a mean bias deviation (MBD) less than 2.14% with respect to TOMS, OMI and GOME. The MBD increases to 3% in the comparison…
Optimizing channel selection for cognitive radio networks using a distributed Bayesian learning automata-based approach
2015
Consider a multi-channel Cognitive Radio Network (CRN) with multiple Primary Users (PUs), and multiple Secondary Users (SUs) competing for access to the channels. In this scenario, it is essential for SUs to avoid collision among one another while maintaining efficient usage of the available transmission opportunities. We investigate two channel access schemes. In the first model, an SU selects a channel and sends a packet directly without Carrier Sensing (CS) whenever the PU is absent on this channel. In the second model, an SU invokes CS in order to avoid collision among co-channel SUs. For each model, we analyze the channel selection problem and prove that it is a so-called "Exact Potent…
An Improved Receiver Architecture for Cyclic-Prefixed OFDM
2009
A novel Orthogonal Frequency Division Multiplexing receiver architecture to be employed with standard (e.g. Wireless LAN) transmitters is proposed. It features enhanced error-rate performance with flexible computational complexity and robustness to imperfect channel estimation. It is based on exploitation of the redundancy available in the cyclic prefix after cancellation of interference from the previous block. In order to show the effectiveness of our proposal, a number of comparisons to the standard per-subcarrier receiver and a previously existing method are reported.
Modeling of Resonance Phenomena in Self-Oscillating System of Agricultural Machines
2021
Factors affecting the interaction of the active cultivator paw with the soil environment are considered in this article. It was established that the active oscillating effect of tillage machines on the environment leads to reduction in its traction characteristics, and the design of symmetrical movable paw is capable of self-oscillation in a horizontal plane. It was developed the theoretical model of oscillatory movements that takes into account the main structural parameters of working bodies represented by symmetrical cultivator paws of the active type. For laboratory studies, a circular soil channel is used, which ensures the movement of the soil relative to the stationary working body f…
STUDIES ON THE CONSTRUCTION AND FUNCTIONING OF MACHINES FOR FERTILIZER DISTRIBUTION
1970
SUMMARY The researches were made on the machine of fertiliz er distribution MA 3,5, which has a capacity of 3,5 m 3 . It is used for transport and spreading solid chem ical fertilizers. It is tracted by tractor U 650 and is actioned from the p ower prize of tractor and from the right support wheels. This machine is formed of frame with catching equipment, bin, distribution equipment, transmision and mechanisms of adjustment and getting in function. The metal frame is supported by 2 pairs of wheels w ith tires, which afford a big mobility during work to the machine . . The distributor is of centrifugal type, formed of a horizontal disc with 6 pallets with adjusted position. Above the disc is…
Performance analysis of amplify-and-forward cooperative communication systems with channel estimation errors
2008
Cooperative diversity is a transmission technique that achieves a diversity gain by using a combination of the relayed signal and the direct signal. In this paper, we study the symbol-error-rate (SER) performance of a cooperative communication system operating in an amplify-and-forward (AF) mode, where the channel state information (CSI) available at the receiver is an estimate of the channel gains with estimation errors. We derive both the probability density function and the moment generating function of the instantaneous signal-to-noise ratio (SNR) at the destination terminal. These statistical quantities are then applied to study the performance of an AF cooperative communication system…
Global sensitivity of aviation NO<sub>x</sub> effects to the HNO<sub>3</sub>-forming channel …
2013
Abstract. The impact of a recently proposed HNO3-forming channel of the HO2 + NO reaction on atmospheric ozone, methane and their precursors is assessed with the aim to investigate its effects on aviation NOx induced radiative forcing. The first part of the study addresses the differences in stratospheric and tropospheric HOx-NOx chemistry in general, by comparing a global climate simulation without the above reaction to two simulations with different rate coefficient parameterizations for HO2 + NO → HNO3. A possible enhancement of the reaction by humidity, as found by a laboratory study, particularly reduces the oxidation capacity of the atmosphere, increasing methane lifetime significantl…