1,721,277 research outputs found
Improved Nyquist Pulses
No full textIn this letter, we propose two new Nyquist (intersymbol interference free) pulses that exhibit better error probability performance in the presence of sampling errors than the popular raised-cosine and a recently proposed pulse by Beaulieu, Tan, and Damen. The new pulses are also robust to the root and truncation operations
Rethinking chronic obstructive pulmonary disease.
No full textChronic obstructive pulmonary disease (COPD) is a complex polygenic disease characterized by an abnormal inflammatory response to smoke, and results in a progressive and debilitating condition with declining lung function. The reasons why some smokers get COPD are not known. We suggest that corticosteroid resistance, which derives from oxidative stress, might actually be the cause of COPD and represent the starting point of the pathology. The absence of response to corticosteroids would let the disease develop, impairing the organism capacity to suppress any kind of inflammatory process. Corticosteroid resistance may derive from smoke induced oxidative stress and plausibly impairs the organism capacity to suppress inflammation. Many factors may contribute to the development and persistence of corticosteroid resistance: inefficient antioxidant defences, a corticosteroid response less efficient or more sensitive to oxidative conditions, and also any other concomitant factor, environmental, genetic or intercurrent, which would contribute to amplify inflammation and hence oxidative stress. One or more of these factors might represent the variable component of the disease, which gives origin to COPD heterogeneity. This hypotheses may also explain why the disease persists after quitting smoking, as an inflammatory process severe enough to generate a strong oxidative stress may support itself by maintenance of corticosteroid resistance
Noise determinism in multi-conductor narrow band PLC channels
No full textThis paper presents an analysis of the noise in multi-conductor power grid networks. This is relevant in multiple-input multiple-output (MIMO) power line communications. In particular, we consider in-building networks and the narrow band spectrum 3-500 kHz. The noise is acquired between the Live and Protective-Earth and between the Neutral and Protective-Earth conductor pairs in a number of outlets. The results show a prominent impulsive time variant behavior. More interestingly, the noise signals in the two conductor pairs are not only correlated, but statistically dependent and in many cases identical. This suggests a form of determinism of the noise signals that can be exploited by spatial noise canceling techniques, one of which is presented in this paper
Stochastic geometry for the analysis of small radio cells and PLC back-hauling
No full textAlthough powerlines have not been designed for data transmission, recent technical developments in Power Line Communication (PLC) have pushed the offered capacity much higher than expected, making PLC an interesting technology for last mile connections like the back-hauling considered in this work. On the other hand, cellular traffic is doubling every year, and this growth trend is not expected to end soon. Small cells have been advocated as a solution to fragment the network and increase the local capacity; in addition, new generation of mobile communication is likely to employ high frequency bands that will cover smaller areas, hence, an increase in cell density is expected. This will increase the challenge for the realization of a cost effective high performance back-haul to bridge the small cell network with the core network. Nowadays, the back-haul portion of the network is either wireless or high speed wireline (ADSL, optical fiber). This paper introduces the idea of employing PLC to support back-hauling for small radio cells. To assess the back-haul requirements and the performance of the integrated radio-PLC network, a topology model is proposed to describe both the small radio cell network layout and the power delivery grid used to both power and”data” connect the base stations. Then, a parametric cell traffic model is considered to measure the overall traffic to be transported through the PLC network and determine whether (under the power grid topology constraints) the PLC back-haul can meet the traffic demands
Non Intrusive Network Impedance Estimation with State of the Art PLC Modems
No full textThe knowledge of the Power Line (PL) network impedance is relevant to improve the performance of the communication system and enable smart grid monitoring and diagnostics. This paper introduces a new method to estimate the PL grid impedance exploiting only voltage measurements and changes of the load at the receiver side of the Power Line Communication Modem (PLM). The proposed estimation technique is called Non Intrusive (NI) because does not require signals to be injected at the measurement port. But signals originated from a remote node are exploited for the impedance estimation. The exploitation of PLMs not only as communication devices but also to sense the Power Line Network (PLN) parameters, will promote new applications in the domain of PL diagnostics and allow better PL grid monitoring. The method was evaluated through simulations and real measurements. The proposed approach applies to both single and multi-conductor technologies at different frequency bands
Analysis of High-Frequency Impedance Measurement Techniques for Power Line Network Sensing
No full textPower line network topology identification using admittance measurements and total least squares estimation
No full textIn this paper, we consider the identification of a smart grid network topology by means of admittance measurements performed at the network nodes. We show how the application of the transmission line theory allows the identification of the node-to-node connections. Thereby, a topology identification algorithm is presented. The identification error due to the network noise is reduced by performing repeated measurements, either at different time instants or over a set of frequencies, at each network node. The information is then fused by means of the total least square regression technique, which is also compared to a simpler estimator. A thorough analysis of the results is then presented, which shows good reliability of the proposed algorithm
Power line fault detection and localization using high frequency impedance measurement
No full textThe reliability and quality of electrical power networks are affected by the occurrence of electrical faults. In this paper, we propose a novel method to identify the occurrence of faults in distribution networks, based on impedance measurements performed at the central distribution office. The measurements can be performed using PLC modems that belong to the energy metering infrastructure. The fault is detected by means of continuous impedance monitoring and afterwards its distance from the central office is estimated using the same measurement traces, without requiring additional information. Different type of faults are tested, and the effect of the measurement bandwidth and the electrical noise on the measurement is also assessed
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