Papers by Nicholas Avlonitis
39th International Communications Satellite Systems Conference (ICSSC 2022)
38th International Communications Satellite Systems Conference (ICSSC 2021)
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Advances in Communications Satellite Systems Proceedings of The 36th International Communications Satellite Systems Conference (ICSSC-2018), 2019
The DVB-S2 standard has been optimised for provision of broadband multimedia services to geograph... more The DVB-S2 standard has been optimised for provision of broadband multimedia services to geographically dispersed fixed satellite end-users under line-of-sight (LOS) channel condition. However, continuing growth in demand for mobile broadband services via satellite necessitates a detailed examination of the DVB-S2 technology to assess its suitability for application in the mobile satellite environment. The environment is affected by signal fading due to path blockage, multipath propagation and shadowing, Doppler shift which is expressed by the Rician channel K-factor parameter values. In this paper, a model was developed in MATLAB® to simulate transmission scenarios through a mobile satellite channel, in order to investigate the bit-error-rate (BER) performance of the 16-APSK and 32-APSK modulation formats for different coding rates. This modelling of higher modulation formats of the DVB-S2 standard until now, has not been addressed adequately in related literature. Moreover, the mobility effect over the BER performance is not well investigated in the literature especially for high modulation schemes. Results obtained by simulation indicate a significant degradation in the system's BER when compared to a line-of-sight channel condition. Which even becomes worse with added varying mobility scenarios. However, higher Rician channel K-factor values tend to improve the link quality closer to that of the AWGN. These results highlight a crucial need to develop improved receiver processing and new switching thresholds applicable to the mobile satellite environment that deliver improved link availability as well as enhanced data throughput for different mobility scenarios.
Journal of Atmospheric and Solar-Terrestrial Physics, 2016
A study on rain statistical parameters such as one minute rain intensity, possible number of minu... more A study on rain statistical parameters such as one minute rain intensity, possible number of minute occurrences with respective percentage of time in a year has been evaluated for the purpose of communication link design at Ka, Q, V bands as well as at Free-Space Optical communication links (FSO). To understand possible outage period of a communication links due to rainfall and to investigate rainfall pattern, Automatic Weather Station (AWS) rainfall data is analysed due its ample presence across India. The climates of the examined AWS regions vary from desert to cold climate, heavy rainfall to variable rainfall regions, cyclone effective regions, mountain and coastal regions. In this way a complete and unbiased picture of the rainfall statistics for Indian region is evaluated. The analysed AWS data gives insight into yearly accumulated rainfall, maximum hourly accumulated rainfall, mean hourly accumulated rainfall, number of rainy days and number of rainy hours from 668 AWS locations. Using probability density function the one minute rainfall measurements at KL University is integrated with AWS measurements for estimating number of rain occurrences in terms of one minute rain intensity for annual rainfall accumulated between 100 mm and 5000 mm to give an insight into possible one minute accumulation pattern in an hour for comprehensive analysis of rainfall influence on a communication link for design engineers. So that low availability communications links at higher frequencies can be transformed into a reliable and economically feasible communication links for implementing High Throughput Services (HTS).
2003 High Frequency Postgraduate Student Colloquium (Cat. No.03TH8707), 2003
Multi-level modulations schemes for optical communication systems use less bandwidth for a given ... more Multi-level modulations schemes for optical communication systems use less bandwidth for a given data rate, and so besides having potential spectral efficiency advantages, may also provide reduced sensitivity to fiber dispersion and nonlinearities. In this paper we model the propagation of 4-level amplitude shift keying signals, and compare their performance, for both return-to-zero and non-retum-to-zero formats, to on-off keying. At the cost of a backto-back sensitivity penalty, significantly increased dispersion reach is shown, and reduced impact of nonlinearities is also demonstrated in a multi-channel environment.
Applied Physics Letters, 2015
2014 International Conference on Electronics and Communication Systems (ICECS), 2014
ABSTRACT The study of rain statistics, including average and extreme conditions, plays a signific... more ABSTRACT The study of rain statistics, including average and extreme conditions, plays a significant role in predicting link availability and in calculating required tradeoff margins for the designing of a ground to space RF link. In this paper the cumulative distribution of average rainfall measured for 15 years is used in order to obtain probabilities of exceedance of rainfall rates using cumulative time statistics and empirical models for the Indian subcontinent. The results are compared with the rain rates extracted from the ITU-R model for the locations under study. The calculated rainfall rates suggest significant variances in the climatic features such as probability of heavy rain and number of rainy days in a year. The analysis shows that the ITU-R model underestimates the rainfall intensity rates by 32.6%, 26.2% and 40.7%, 19% at higher and lower percentage of time when compared with measured rain rate data from Indian Metrological department. It is shown that the discrepancy between the empirical model and ITU-R model at higher percentage of time results in a 15 to 5 dB difference in predicted signal attenuation depending on the region, percentage of time and frequency. Adaptive Power Control is proposed as a means to improve the link availability during period of higher intensity rainfall.
This effort focuses on the comparison of On Off Keying (OOK) to incoherent 4-ary Amplitude Shift ... more This effort focuses on the comparison of On Off Keying (OOK) to incoherent 4-ary Amplitude Shift Keying (ASK). We show that a 0.4 bits/s/Hz improvement in spectral efficiency is obtained by utilising 4-ary ASK. We determined the filter steepness required to achieve this maximum obtainable spectral efficiency. The comparison of OOK and 4-ary ASK in terms of dispersion tolerance for Non-Return-to-Zero and Return-to-Zero is performed. We also prove that cross phase modulation, on its own, should not affect the maximum obtainable spectral efficiency of 4-ary ASK. Finally, we present simulation work showing that 4-ary ASK can potentially increase the capacity of Kerr effect limited DWDM systems. For the first time, comparison of 4-ary ASK and OOK is performed in the nonlinear regime.
A study on rain statistical parameters such as one minute rain intensity, possible number of minu... more A study on rain statistical parameters such as one minute rain intensity, possible number of minute occurrences with respective percentage of time in a year has been evaluated for the purpose of communication link design at Ka, Q, V bands as well as at Free-Space Optical communication links (FSO). To understand possible outage period of a communication links due to rainfall and to investigate rainfall pattern, Automatic Weather Station (AWS) rainfall data is analysed due its ample presence across India. The climates of the examined AWS regions vary from desert to cold climate, heavy rainfall to variable rainfall regions, cyclone effective regions, mountain and coastal regions. In this way a complete and unbiased picture of the rainfall statistics for Indian region is evaluated. The analysed AWS data gives insight into yearly accumulated rainfall, maximum hourly accumulated rainfall, mean hourly accumulated rainfall, number of rainy days and number of rainy hours from 668 AWS locations. Using probability density function the one minute rainfall measurements at KL University is integrated with AWS measurements for estimating number of rain occurrences in terms of one minute rain intensity for annual rainfall accumulated between 100 mm and 5000 mm to give an insight into possible one minute accumulation pattern in an hour for comprehensive analysis of rainfall influence on a communication link for design engineers. So that low availability communications links at higher frequencies can be transformed into a reliable and economically feasible communication links for implementing High Throughput Services (HTS).
2009 11th International Conference on Transparent Optical Networks, 2009
Abstract We derive a differential Q factor model for DPSK signals detected by delay line demodula... more Abstract We derive a differential Q factor model for DPSK signals detected by delay line demodulators. The parameters involved in the model are related to signal characteristics such as phase noise linewidth, OSNR and power fluctuations, and can therefore be directly monitored from it. Moreover, its validity is tested and confirmed under various phase noise and amplitude fluctuations scenarios. In addition, performance bounds based on phase noise levels can also be derived from the model The simplicity of this fast model ...
IEE Proceedings - Optoelectronics, 2006
The authors model and characterise the performance of 10 Gbit/s 4-ary amplitude shift keying (ASK... more The authors model and characterise the performance of 10 Gbit/s 4-ary amplitude shift keying (ASK) systems in dispersive environments at 1550 nm. Both non-return-to-zero (NRZ) and return-to-zero (RZ) formats are examined, with comparisons to on-off keying (OOK) in each case. Both single amplified links and cascaded fibre-amplifier links are modelled. While 4-ary ASK systems suffer a back-to-back sensitivity penalty of up to 7 dB with respect to OOK, they offer a significantly reduced dispersion sensitivity, particularly for RZ formats. This suggests advantages for M-ary coding in future systems employing optical time division multiplexing. Optimal level spacing for ASK is analysed and approximations for different noise regimes are shown to fit well to detailed calculations. Sensitivity to extinction ratio is examined; RZ systems are shown to have higher sensitivity than NRZ for both 4-ary and OOK. Finally, the authors show that frequency drift, or equivalently, a de-tuning in the centre frequency of the optical filter, is more severe for OOK than for 4-ary ASK, especially in the case of non-fully dispersion uncompensated systems.
Unmanned/Unattended Sensors and Sensor Networks X, 2014
Journal of Lightwave Technology, 2000
In this paper, the authors derive the moment generating function (MGF) of the decision variable f... more In this paper, the authors derive the moment generating function (MGF) of the decision variable for a practical optical differential quadrature phase shift keying (DQPSK) receiver affected by phase noise and the amplifier spontaneous emission noise. The effect of the different optical filters, Gaussian, Fabry-Pérot (FP), and optical integrator, on the phase noise is examined. Using the saddle point approximation, the authors obtain numerically the bit error rate (BER) for the above system, as a function of the optical-signal-to-noise ratio (OSNR) and the source linewidth. The model is found to agree with previous published simulation results and the Monte Carlo simulations presented in this paper. The authors also calculate the BER floors for DQPSK inflicted by the phase noise and compare its performance with differential phase shift keying (DPSK). Finally, the authors examine the effect of interferometric demodulation on the relative intensity noise (RIN) spectra and the impact on the DQPSK system performance. In particular, the authors examine the influence of system dispersion on the receiver sensitivity.
The study of rain statistics, including average and extreme conditions, plays a significant role ... more The study of rain statistics, including average and extreme conditions, plays a significant role in predicting link availability and in calculating required tradeoff margins for the designing of a ground to space RF link. In this paper the cumulative distribution of average rainfall measured for 15 years is used in order to obtain probabilities of exceedance of rainfall rates using cumulative time statistics and empirical models for the Indian subcontinent. The results are compared with the rain rates extracted from the ITU-R model for the locations under study. The calculated rainfall rates suggest significant variances in the climatic features such as probability of heavy rain and number of rainy days in a year. The analysis shows that the ITU-R model underestimates the rainfall intensity rates by 32.6%, 26.2% and 40.7%, 19% at higher and lower percentage of time when compared with measured rain rate data from Indian Metrological department. It is shown that the discrepancy between the empirical model and ITU-R model at higher percentage of time results in a 15 to 5 dB difference in predicted signal attenuation depending on the region, percentage of time and frequency. Adaptive Power Control is proposed as a means to improve the link availability during period of higher intensity rainfall.
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Papers by Nicholas Avlonitis