Оценка помехоустойчивости многочастотных систем связи при воздействии импульсного шума

Impact of impulsive noise on performance of uncoded and coded OFDM system is considered with account for the fact that the length of modulation symbol can be com.parable with average length of noise pulses. Temporal dynamics of noise is described by a Markov model. Theoretical calculations and simulation results lead to the following conclusions: efficient averaging of noise level takes place if average duration of noise pulses does not exceed 1% of OFDM symbol length; during the noise burst power losses due to impulsive nature of noise can reach 2…2,5 dB. Multi-frequency com.munication system, impulse noise, data transmission over the power line.Рассмотрено влияние импульсного шума на некодированные и кодированные многочастотные (OFDM) системы с учетом того, что длительность символа может быть сопоставима со средней длительностью импульса шума. Временна́я динамика возникновения импульсов шума описана марковской моделью. Теоретические расчеты и результаты моделирования позволяют заключить, что эффективное усреднение уровня шума происходит, если средняя длительность его импульсов не превосходит 1 % от длительности OFDM-символов. Во время действия пачки импульсов энергетические потери, обусловленные импульсным характером шума, могут достигать 2…2,5 дБ

Estimation of noise stability of multi-frequency com.munication systems when pulse noise impacting

Impact of impulsive noise on performance of uncoded and coded OFDM system is considered with account for the fact that the length of modulation symbol can be com.parable with average length of noise pulses. Temporal dynamics of noise is described by a Markov model. Theoretical calculations and simulation results lead to the following conclusions: efficient averaging of noise level takes place if average duration of noise pulses does not exceed 1% of OFDM symbol length; during the noise burst power losses due to impulsive nature of noise can reach 2…2,5 dB. Multi-frequency com.munication system, impulse noise, data transmission over the power line

Constraints on fluid origins and migration velocities along the Marmara Main Fault (Sea of Marmara, Turkey) using helium isotopes

Fluids venting from the submarine portion of the Marmara Main Fault (part of the North Anatolian Fault system, Turkey) were sampled in Ti bottles deployed by submersible. The fluids consist of mixtures of fault derived gases, fault related cold seep fluids, and ambient seawater; these components can readily be distinguished using the isotopes of He and the He/Ne ratios. 3He/4He ratios range between 0.03±0.1 and 4.9±0.4 Ra, indicating that both crustal and mantle derived sources of helium are sampled by the fault. The dominant gas in all the samples analyzed is methane with the abundance of CO2 below detection (≤2%) in the mantle rich (high 3He/4He) fluids. This is in contrast to nearly all mantle derived fluids where the C species are dominated by CO2. While high CH4/CO2 ratios may reflect organic or inorganic reactions within the crust which reduce mantle derived CO2 to methane, this is not a priori necessary: we show that simple dilution of mantle fluids with methane produced within local sediments could result in the high 3He/4He, methane rich gases currently emanating from the fault. This observation is supported by an anticorrelation between 3He/4He and C/3He, which is consistent with addition of C and 4He simultaneously to the fluids. The highest 3He/4He ratios were found in the Tekirdag Basin, at the foot of the escarpment bordering the Western Sea of Marmara, where seismic data are consistent with the presence of a fault network at depth which could provide conduits permitting deep-seated fluids to rise to the surface. The lack of recent volcanism, or any evidence of underlying magmatism in the area, along with low temperature fluids, strongly suggests that the 3He-rich helium in these fluids was derived from the mantle itself with the Marmara Main Fault providing a high permeability conduit from the mantle to the surface. Assuming that the mantle source to the fluids originally had a 3He/4He ratio of 6 Ra, the minimum fluid velocities (considering only vertical transport and no mixing with parentless 4He) implied by the high 3He/4He ratios are of the order of 1-100 mm yr−1

Understanding and study perspectives on tectonic evolution and crustal structure of the Paleozoic Chinese Tianshan

The Chinese Tianshan Belt is one of the key regions for the understanding of tectonics of the Central Asian Orogenic Belt (CAOB). An international field excursion and workshop were organized to conduct a common observation and discussion on the tectonic evolution of the Chinese Tianshan. This report summarizes the main achievements, including acknowledged geological features, controversial and remaining scientific problems, and discussion of a tentative geodynamic model. Thus, it is helpful to clarify what has been done in the past, what should be improved and what needs to be done in the future and therefore to better understand the tectonics of the Chinese Tianshan Belt and the CAOB as well