scholarly journals Determination of Clock Synchronization Errors in Distributed Networks

2018 ◽  
Vol 56 (2) ◽  
pp. 610-632 ◽  
Author(s):  
Weiguo Xia ◽  
Ming Cao
Keyword(s):  
Clock Synchronization ◽  
Distributed Networks ◽  
Synchronization Errors

scholarly journals Challenges in Clock Synchronization for On-Site Coding Digital Beamformer

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Satheesh Bojja Venkatakrishnan ◽  
Elias A. Alwan ◽  
John L. Volakis
Keyword(s):  
Clock Synchronization ◽  
Digital Signal ◽  
Data Converter ◽  
Analog To Digital ◽  
Synchronization Errors ◽  
Digital To Analog Converters ◽  
Field Programmable ◽  
Programmable Gate Arrays ◽  
Signal Synchronization ◽  
Signal Processors

Typical radio frequency (RF) digital beamformers can be highly complex. In addition to a suitable antenna array, they require numerous receiver chains, demodulators, data converter arrays, and digital signal processors. To recover and reconstruct the received signal, synchronization is required since the analog-to-digital converters (ADCs), digital-to-analog converters (DACs), field programmable gate arrays (FPGAs), and local oscillators are all clocked at different frequencies. In this article, we present a clock synchronization topology for a multichannel on-site coding receiver (OSCR) using the FPGA as a master clock to drive all RF blocks. This approach reduces synchronization errors by a factor of 8, when compared to conventional digital beamformer.

scholarly journals Influence of synchronization errors оn the noise immunity of coherent reception of M-PSK signals

2019 ◽  
Vol 7 (5) ◽  
pp. 47-61 ◽  
Author(s):  
G. V. Kulikov ◽  
Nguyen Van Dung
Keyword(s):  
Information Transfer ◽  
Noise Immunity ◽  
Clock Synchronization ◽  
Signal To Noise Ratio ◽  
Dynamic Error ◽  
Radio Waves ◽  
Satellite Television ◽  
Synchronization Errors ◽  
Dynamic Errors ◽  
Ieee 802.11 Wireless Networks

Signals with multiple phase-shift keying (M-PSK) have long been successfully used for highspeed information transfer in many applications – a number of adopted protocols of IEEE 802.11 wireless networks, digital satellite television DVB-S, DVB-S2/S2X systems, cellular networks CDMA and others. The most important characteristic of such systems is their noise immunity, which depends not only on the propagation conditions of radio waves in the communication channel, but also on the quality of operation of the component nodes of the information transmission systems themselves. The paper investigates the influence of the inaccuracy of estimating the frequency and phase of the carrier and the inaccuracy of the clock synchronization system on the noise immunity of coherent reception of M-PSK signals. Analytical expressions were obtained by statistical radio engineering methods. The expressions allow calculating the dependence of the probability of a bit error on the signal-to-noise ratio for various errors of the receiver auxiliary systems. In this case, the magnitudes of the errors were assumed to be either constant (static error) or dynamically changing (dynamic error). The dynamic errors were modeled using the Monte Carlo method, and the dynamic errors themselves were assumed to be Gaussian random variables. It is shown that the inaccuracy of estimating these parameters strongly influences the noise immunity of the coherent reception of the M-PSK signal, and this effect increases with increasing signal positionality. Estimates of the maximum permissible errors of the analyzed systems are given. When M-PSK signals are received, a tolerable value of the frequency of the reference oscillations can be considered as a ∆ωTs value of about 0.05. The allowable inaccuracy of the carrier phase estimation depends on the positioning of the signal and varies from π/36–π/72 for 2PSK to π/180 for 32PSK. The allowable time offset of the clock moments can be considered the value of 3–5% of the clock interval duration.

scholarly journals Nonrecursive algorithm for remote geolocation using ranging measurements

2006 ◽  
Vol 2006 ◽  
pp. 1-9 ◽  
Author(s):  
P. L. Kaufmann ◽  
R. Vilhena de Moraes ◽  
H. K. Kuga ◽  
L. A. Beraldo ◽  
C. N. Motta Marins ◽  
...  
Keyword(s):  
Clock Synchronization ◽  
Algebraic Solution ◽  
Propagation Time ◽  
Clock Signal ◽  
The Earth ◽  
Remote Determination ◽  
Synchronized Clocks

The objective of this work is to present a new algebraic solution for the problem of remote determination of geographic coordinates of a target, using a new remote geopositioning system being developed in Brazil. It can be useful for double-check measurements obtained with other methods, for certain critical applications, being capable to perform independently from them. This system requires three-reference bases on the surface of the earth with synchronized clocks and a repeater in space. Calculations are derived from measurements of propagation time of clock signal transmitted by one base to all bases and target, via a transponder in space. The algorithm also provides the “instantaneous” determination of the repeater position in space and brings other applications in navigation and remote clock synchronization. The algorithm has been successfully tested through computational software.

scholarly journals Influence of phase and clock synchronization errors on the noise immunity of coherent reception of signals with quadrature amplitude modulation

2021 ◽  
Vol 9 (2) ◽  
pp. 35-43
Author(s):  
G. V. Kulikov ◽  
A. A. Lelyukh ◽  
E. V. Batalov
Keyword(s):  
Amplitude Modulation ◽  
High Speed ◽  
Noise Immunity ◽  
Clock Synchronization ◽  
Signal To Noise Ratio ◽  
Phase Error ◽  
Relative Displacement ◽  
Quadrature Amplitude Modulation ◽  
Digital Television ◽  
Synchronization Errors

Signals with quadrature amplitude modulation (QAM) is widely used for high-speed transmission of information in many radio systems and, in particular, in digital television systems. In the receiver, which is part of the transceiver equipment of such systems, there is a block for the formation of reference oscillations and a clock synchronization block. Due to hardware instabilities and propagation conditions, phase and clock errors may occur, which cause additional errors during demodulation of the received signal, and which can significantly impair the noise immunity of the reception. The paper investigates the effect of phase and clock synchronization errors on the noise immunity of coherent reception of QAM signals. Using the methods of statistical radio engineering, the parameters of the distributions of processes in the receiver are obtained and the probability of bit error is estimated. The dependences of the probability of bit error on the magnitude of the phase error in the formation of the reference oscillations and on the relative displacement of the clock moments, as well as on the signal-to-noise ratio, are obtained. It is shown that these errors can greatly reduce the noise immunity of the reception, and with an increase in the positioning of the signals, this effect increases. If we assume that the admissible reception energy loss is 0.5 dB due to each of these errors, then the allowable phase error is from ~3° at M = 4 to ~1° at M = 64, and the allowable clock synchronization error, respectively, is from ~5% at M = 4 to ~2% at M = 64. To provide more stringent requirements for the magnitude of losses, the requirements for the indicated errors increase significantly.

scholarly journals Numerical determination of frequency behavior in cloaking structures based on L-C distributed networks with TLM method

2008 ◽  
Vol 16 (13) ◽  
pp. 9344 ◽  
Author(s):  
Cèdric Blanchard ◽  
Jorge Portí ◽  
Juan-Antonio Morente ◽  
Alfonso Salinas ◽  
Bae-Ian Wu
Keyword(s):  
Distributed Networks ◽  
Numerical Determination ◽  
Tlm Method ◽  
Frequency Behavior

A modified approach for automated reference point determination of SLR and VLBI telescopes

2018 ◽  
Vol 85 (10) ◽  
pp. 616-626 ◽  
Author(s):  
Michael Lösler ◽  
Cornelia Eschelbach ◽  
Stefan Riepl
Keyword(s):  
Reference Point ◽  
Terrestrial Reference Frame ◽  
Reference Points ◽  
Combination Process ◽  
Local Ties ◽  
Synchronization Errors ◽  
Space Geodetic Techniques ◽  
Point Determination ◽  
Technical Effort

AbstractThe International Terrestrial Reference Frame (ITRF) is derived by combining several space geodetic techniques. Basically, a meaningful combination of the geodesic space techniques is impossible without further geometrical information, i. e. local-ties. Local-tie vectors are defined between the geometrical reference points of space geodetic techniques at co-location stations. These local-ties are introduced during the inter-technique combination process, to overcome the weak physical connection between the space geodetic techniques. In particular, the determination of the reference point of radio telescopes or laser telescopes is a challenging task and requires indirect methods. Moreover, the Global Geodetic Observing System (GGOS) strives for an automated and continued reference point determination with sub-millimeter accuracy, because deviations in local-ties bias global results.This investigation presents a modified approach for automated reference point determination. The new approach extends the prior work of Lösler but evades the synchronization between the terrestrial instrument and the telescope. Thus, synchronization errors are omitted and the technical effort is reduced. A proof of concept was carried out at Geodetic Observatory Wettzell in 2018. Using a high-precision, mobile laser-tracker, the reference point of the Satellite Observing System Wettzell (SOS-W) was derived. An extended version of the in-house developed software package HEIMDALL was employed for a mostly automated data collection. To evaluate the estimated reference point, the derived results are compared with the results of two approved models.

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