Powerline communications (PLC) has emerged in recent times as a viable compliment to existing wir... more Powerline communications (PLC) has emerged in recent times as a viable compliment to existing wireless communication networks, and it is expected to eventually provide a strong competition to its rivals in the near future. PLC networks consist of numerous segments of branching elements which results in a multiple reflection scenario, a behaviour analogous to that of mobile radio channels. As a result, a multipath modeling approach has found popularity among researchers in capturing the propagation effects in PLC channels. The accuracy of the model is controlled by the number of paths considered in the solution process since there exist theoretically an infinite number of paths between the transmitter and receiver. Thus, the number of dominant or significant paths is critical to the solution process. An unnecessarily large number of paths will result in a solution that is resource intensive with minimal improvement in accuracy, while a relatively smaller choice of number of paths will lead to an inaccurate solution. In this light, an optimum number of paths is required to minimize the resource/accuracy quotient. In this paper, a branched powerline network is considered as a lattice structure and the signal propagation is conveniently represented with a bouncing diagram. The transmission and reflection paths are easily traceable in this representation. Due to possible infinite paths presented to a propagating signal as it travels towards the receiver, an expression that represents only the dominant paths is derived. In this consideration, a restriction is placed on the definition of a “dominant” path. Since there are no standards governing this assumption, only first order reflections are considered to carry a reasonable amount of energy to have a meaningful contribution towards the total signal level at the receiver. This assumption is one order above the classical two-ray propagation theory applicable to wireless networks. In our derivation, we have considered the possibility of having equal path lengths traversed over different routes. The general model is applicable to a PLC network of any size with a receiver place anywhere in such a network.
The power line network presents a readily available medium that can be utilized for the delivery ... more The power line network presents a readily available medium that can be utilized for the delivery of both low and high data rate communication services. This ready available infrastructure implies that the cost of network set up is very low compared to other technologies, like fiber optics. However, the power line channel is very noisy and presents a hostile environment for communication purposes. But, given the expansive and extensive coverage of the power line network; it presents the most ubiquitous medium, and therefore there is need for a thorough understanding of the channel characteristics, one of the most important being noise. In this paper, we present both parametric and nonparametric models of the noise encountered in an indoor power line network. The models are derived both parametrically and non-parametrically from noise measurements carried out in both frequency and time domains.
The super high frequency and the millimeterwave frequency bands are promising solutions to cope w... more The super high frequency and the millimeterwave frequency bands are promising solutions to cope with the increasing demand for higher data rates. Accurate channel modelling is vital for the performance analysis of wireless networks. Line-of-sight (LOS) probability is an essential parameter in channel modeling. It gives an insight into the probability of having a clear LOS connection between the transmitting and receiving antennas. There is a lack in characterising the LOS probability based on measurements in indoor corridor channels. In this paper, we parameterise and compare the performance of LOS probability models that are adopted by well-known standards. Also, a new LOS probability model is proposed based on the criteria of the minimum mean square error (MMSE) between the model and real measured data. The data was collected in a typical indoor corridor environment at 14, 18, and 22 GHz frequency bands. The results generally show that our proposed model outperforms the standard models in terms of its accuracy of fitting the real measured data with the minimum possible MSE. In addition, this paper studies the impact of the operating frequency on the LOS probability models' performance. The research finding reveals that the models' accuracy has a random behaviour with the frequency. Therefore, more investigations should be conducted to understand the models' behaviour over a wide range of frequencies to improve the precision of the LOS probability models for enclosed indoor channels.
Rain cell size is an input requirement for rain-induced attenuation studies. It is useful in esti... more Rain cell size is an input requirement for rain-induced attenuation studies. It is useful in estimating the extent of a given radio link path that will traverse the rain medium in a given rain event. The \Synthetic Storm" approach, which requires 1-minute integration time data, is used to derive the proposed rain cell sizes for various climatic zones within South Africa. The conversion of the readily available 1-hour integration time rain rate data to the desired 1-minute rain rate is carried out flrst for some locations and then validated by the existing measurement data and proposed global conversion factors. By the use of rain-induced attenuation prediction equation for terrestrial links that requires rain cell size as input, contour plots of speciflc attenuation for two high bandwidth frequencies used in terrestrial link implementations is presented. Site diversity separation distance map is proposed as well from the link budget analysis for each location to achieve an all time link availability of 99.99% of time.
International Journal on Communications Antenna and Propagation, Dec 31, 2017
With a view to establish a measurement-based profile and prediction model of slant path attenuati... more With a view to establish a measurement-based profile and prediction model of slant path attenuation due to subtropical rain, rainfall data as well as received signal level (RSL) over a 12 GHz satellite TV Receive Only (TVRO) link were monitored simultaneously over a period of about two years in Durban South Africa (28087’S, 30098’E). The rain rate (R0.01) exceeded at 0.01% of time at the location seasonally and over the period of measurement was obtained as 69 mmh-1. The variation pattern of the received signal in clear air over the period was investigated and its relationship with fluctuations of atmospheric parameters other than rain was established by multiple regression. Event-by-event correlation of the rain rate data with that of the RSL in the time domain was carried out, resulting in a reliable subtropical rain attenuation profile which was used to develop a model for slant path rain attenuation due to subtropical precipitation. The model was validated by comparison with the generalized ITU-R model. The latter was found to slightly overestimate path attenuation at rain rates higher than 30 mm/h. The path attenuation exceedance probability over the link is also presented.
Difierent techniques has been proposed by various authors in difierent regions of the world to mo... more Difierent techniques has been proposed by various authors in difierent regions of the world to model the solution to radio wave propagation problems, but most of these techniques have not considered modeling the primary parameters on which other radioclimatology factors are based. This paper has therefore focused on working from the basics, by considering the initial parameters on which radioclimatological factors were based. These initial parameters namely; temperature, pressure and humidity were modeled with vertical height increase using one year radio propagation data and six years radio propagation data in Durban, KwaZulu Natal province of South Africa. A simplifled statistical technique is employed in the analysis of this data. 1. INTRODUCTION The propagation of electromagnetic waves around the earth is in∞uenced by the properties of the earth and the atmosphere (1{5). The earth is an inhomogeneous body whose electromagnetic prop- erties vary considerably as we go from one point to another, its properties varying with temperature, pressure and humidity. According to ITU-R Recommendation P.530 (3), the propagation loss on a terrestrial line-of-sight path relative to free space loss is the sum of difierent contributions which includes: attenuation due to atmospheric gases; difiraction fading due to obstruction or partial obstruction of the path; fading due to multipath and attenuation due to precipitation. Each of these contributions has its
This paper presents an alternative approach to model the transfer characteristics of power lines ... more This paper presents an alternative approach to model the transfer characteristics of power lines for broadband power line communications (PLC). The model is developed by considering the power line to be a two-wire transmission line and the theory of transverse electromagnetic (TEM) wave propagation applied. The characteristic impedance and attenuation constant of the power line are determined through measurements. These parameters are used in model simplification and determination of other model parameters for typical indoor multi-tapped transmission line system. The transfer function of the PLC channel is determined by considering the branching sections as parallel resonant circuits attached to the main line. The model is evaluated through comparison with measured transfer characteristics of known topologies and it is in good agreement with measurements.
While rainfall is a major cause of communication impairment at microwave and millimeter bands, th... more While rainfall is a major cause of communication impairment at microwave and millimeter bands, the effect of rain attenuation in the Ethiopian microwave links, has so far remained as unstudied. Therefore, in this paper, the rain rate distribution at 15 minutes integration time is predicted for different percentage of time of the year based on two years of rain intensity data obtained from National Meteorological Agency (NMA) of Ethiopia. The rainfall rate for one minute integration time not exceeded 0.01% of the time is calculated using ITU-R and Chebil designations, it is found that the highest rainfall rate at 0.01 % of time for any location in Ethiopia, does not exceed 64 mm/h. The ITU-R model is then applied to estimate and analyze rainfall attenuation over terrestrial radio links for ten sites in Ethiopia. The attenuation is predicted for frequencies from 1-150 GHz, with variable distances. The results show that Bahirdar is predicted to experience the largest effect of rain attenuation whereas, Dubti, has the lowest attenuation.
Parameter estimation of linear regression models usually employs least squares (LS) and maximum l... more Parameter estimation of linear regression models usually employs least squares (LS) and maximum likelihood (ML) estimators. While maximum likelihood remains one of the best estimators within the classical statistics paradigm to date, it is highly reliant on the assumption about the joint probability distribution of the data for optimal results. In this paper we use the Generalized Method of Moments (GMM) to address the deficiencies of LS/ML in order to estimate the underlying data generating process (DGP). We use GMM as a statistical technique that incorporate observed noise data with the information in population moment conditions to determine estimates of unknown parameters of the underlying model. Periodic impulsive noise (short-term) has been measured, deseasonalized and modeled using GMM. The numerical results show that the model captures the noise process accurately.
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Aug 1, 2018
The ever-increasing demand for telecommunication services and the already established power line ... more The ever-increasing demand for telecommunication services and the already established power line network makes power line communication (PLC)a very attractive mode of data transmission. However, the power line cables are designed for the transmission of high voltage at low frequencies, which is contrary to the low voltages, and high frequencies needed for the transfer of data signals. Moreover, the power line network is randomly loaded. This in turn results in impedance mismatch with considerable noise and high attenuation. The variant nature of input impedance requires impedance profiling of the PLC network. It is with this profiling that impedance adaptive techniques can be designed and applied to both the input and output of PLC modems, which tend to operate at 50 Ω. If the behaviour of PLC network impedance can be modelled, then the characteristics of the power line network can be known. This will in turn ensure the design of more efficient and effective impedance matching networks. This paper describes modelling of input impedance in a power line channel using parallel resonance circuits. TR5048 Vector Network Analyzer was used to obtain impedance measurements for a frequency range of 1–30 MHz at the power line communication laboratory at the University of KwaZulu-Natal, Durban, South Africa for different test network topologies and configurations considering the extreme cases that include open-circuit and short-circuit terminations. It is observed that the position of the maximum values of impedance depends on the number of branches, the length of the branch and the terminating load impedance. The model shows a good agreement with measurement. The impedance measured was then profiled into minimum, average and maximum bounds.
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Aug 1, 2018
Fifth generation wireless communication networks will demand massive bandwidth for high data rate... more Fifth generation wireless communication networks will demand massive bandwidth for high data rates. The millimeter wave frequency bands will play an important role in the 5G wireless networks due to the available huge chunk of bandwidth. Deployment of wireless networks will require an appropriate path loss model for site-specific environments such as indoor corridors. Structural design and building materials call for development of such models. This work presents a multi-frequency dual-slope large-scale path loss model based on measurements performed in two distinct indoor environments made of glass and concrete. Measurements were conducted at 14 to 22 GHz in typical indoor corridors using a costume-designed channel sounder based on Rohde and Schwarz SMF 100 A signal generator and FSIQ 40 signal analyzer with 120 MHz bandwidth for distances ranging 2 m to 24 m in line-of-sight and non-line-of-sight scenarios. The acquired measurement data of 36,000 directional power delay profiles for 18 transmitter-receiver combinations were analyzed to model a directional dual-slope path loss model for vertically polarized antennas. The directional dual-slope path loss was synthesized with consideration of propagation mechanisms such as reflection and diffraction effectively causing modal attenuation as the signal propagates along the corridor due to wave guiding effect. A breakpoint was established that demonstrates the effects of modal attenuation in a waveguide like corridor. The model was evaluated by performing a comparative analysis on the directional dual-slope path loss model on various indoor corridors with different structural design and materials with well-known alfa-beta-gamma model. The results were observed to give a better prediction of path loss at 14 to 22 GHz over ABG model as fitted to the measurement data. Moreover, the results show that the wave guiding effect is pronounced after the breakpoint due to both free space and multi-modal propagation.
In this paper we will discuss the estimation of powerline communication (PLC) asynchronous impuls... more In this paper we will discuss the estimation of powerline communication (PLC) asynchronous impulsive noise volatility by studying the conditional variance of the noise time series residuals. In our approach, we use the Generalized Autoregressive Conditional Heteroskedastic (GARCH) models on the basis that in our observations, the noise time series residuals indicates heteroskedasticity. By performing an ordinary least squares (OLS) regression of the noise data, the empirical results show that the conditional variance process is highly persistent in the residuals. The variance of the error terms are not uniform, in fact, the error terms are larger at some portions of the data than at other time instances. Thus, PLC impulsive noise often exhibit volatility clustering where the noise time series is comprised of periods of high volatility followed by periods of high volatility and periods of low volatility followed by periods of low volatility. The burstiness of PLC impulsive noise is therefore not spread randomly across the time period, but instead has a degree of autocorrelation. This provides evidence of time-varying conditional second order moment of the noise time series. Based on these properties, the noise time series data is said to suffer from heteroskedasticity. Numerical results provide evidence that the proposed model is capable of providing an accurate stochastic representation of the impulsive noise in the 1-30MHz frequency band. The parameter estimates of the model indicates a high degree of persistence in conditional volatility of impulsive noise which is a strong evidence of explosive volatility.
Powerline communications (PLC) has emerged in recent times as a viable compliment to existing wir... more Powerline communications (PLC) has emerged in recent times as a viable compliment to existing wireless communication networks, and it is expected to eventually provide a strong competition to its rivals in the near future. PLC networks consist of numerous segments of branching elements which results in a multiple reflection scenario, a behaviour analogous to that of mobile radio channels. As a result, a multipath modeling approach has found popularity among researchers in capturing the propagation effects in PLC channels. The accuracy of the model is controlled by the number of paths considered in the solution process since there exist theoretically an infinite number of paths between the transmitter and receiver. Thus, the number of dominant or significant paths is critical to the solution process. An unnecessarily large number of paths will result in a solution that is resource intensive with minimal improvement in accuracy, while a relatively smaller choice of number of paths will lead to an inaccurate solution. In this light, an optimum number of paths is required to minimize the resource/accuracy quotient. In this paper, a branched powerline network is considered as a lattice structure and the signal propagation is conveniently represented with a bouncing diagram. The transmission and reflection paths are easily traceable in this representation. Due to possible infinite paths presented to a propagating signal as it travels towards the receiver, an expression that represents only the dominant paths is derived. In this consideration, a restriction is placed on the definition of a “dominant” path. Since there are no standards governing this assumption, only first order reflections are considered to carry a reasonable amount of energy to have a meaningful contribution towards the total signal level at the receiver. This assumption is one order above the classical two-ray propagation theory applicable to wireless networks. In our derivation, we have considered the possibility of having equal path lengths traversed over different routes. The general model is applicable to a PLC network of any size with a receiver place anywhere in such a network.
The power line network presents a readily available medium that can be utilized for the delivery ... more The power line network presents a readily available medium that can be utilized for the delivery of both low and high data rate communication services. This ready available infrastructure implies that the cost of network set up is very low compared to other technologies, like fiber optics. However, the power line channel is very noisy and presents a hostile environment for communication purposes. But, given the expansive and extensive coverage of the power line network; it presents the most ubiquitous medium, and therefore there is need for a thorough understanding of the channel characteristics, one of the most important being noise. In this paper, we present both parametric and nonparametric models of the noise encountered in an indoor power line network. The models are derived both parametrically and non-parametrically from noise measurements carried out in both frequency and time domains.
The super high frequency and the millimeterwave frequency bands are promising solutions to cope w... more The super high frequency and the millimeterwave frequency bands are promising solutions to cope with the increasing demand for higher data rates. Accurate channel modelling is vital for the performance analysis of wireless networks. Line-of-sight (LOS) probability is an essential parameter in channel modeling. It gives an insight into the probability of having a clear LOS connection between the transmitting and receiving antennas. There is a lack in characterising the LOS probability based on measurements in indoor corridor channels. In this paper, we parameterise and compare the performance of LOS probability models that are adopted by well-known standards. Also, a new LOS probability model is proposed based on the criteria of the minimum mean square error (MMSE) between the model and real measured data. The data was collected in a typical indoor corridor environment at 14, 18, and 22 GHz frequency bands. The results generally show that our proposed model outperforms the standard models in terms of its accuracy of fitting the real measured data with the minimum possible MSE. In addition, this paper studies the impact of the operating frequency on the LOS probability models' performance. The research finding reveals that the models' accuracy has a random behaviour with the frequency. Therefore, more investigations should be conducted to understand the models' behaviour over a wide range of frequencies to improve the precision of the LOS probability models for enclosed indoor channels.
Rain cell size is an input requirement for rain-induced attenuation studies. It is useful in esti... more Rain cell size is an input requirement for rain-induced attenuation studies. It is useful in estimating the extent of a given radio link path that will traverse the rain medium in a given rain event. The \Synthetic Storm" approach, which requires 1-minute integration time data, is used to derive the proposed rain cell sizes for various climatic zones within South Africa. The conversion of the readily available 1-hour integration time rain rate data to the desired 1-minute rain rate is carried out flrst for some locations and then validated by the existing measurement data and proposed global conversion factors. By the use of rain-induced attenuation prediction equation for terrestrial links that requires rain cell size as input, contour plots of speciflc attenuation for two high bandwidth frequencies used in terrestrial link implementations is presented. Site diversity separation distance map is proposed as well from the link budget analysis for each location to achieve an all time link availability of 99.99% of time.
International Journal on Communications Antenna and Propagation, Dec 31, 2017
With a view to establish a measurement-based profile and prediction model of slant path attenuati... more With a view to establish a measurement-based profile and prediction model of slant path attenuation due to subtropical rain, rainfall data as well as received signal level (RSL) over a 12 GHz satellite TV Receive Only (TVRO) link were monitored simultaneously over a period of about two years in Durban South Africa (28087’S, 30098’E). The rain rate (R0.01) exceeded at 0.01% of time at the location seasonally and over the period of measurement was obtained as 69 mmh-1. The variation pattern of the received signal in clear air over the period was investigated and its relationship with fluctuations of atmospheric parameters other than rain was established by multiple regression. Event-by-event correlation of the rain rate data with that of the RSL in the time domain was carried out, resulting in a reliable subtropical rain attenuation profile which was used to develop a model for slant path rain attenuation due to subtropical precipitation. The model was validated by comparison with the generalized ITU-R model. The latter was found to slightly overestimate path attenuation at rain rates higher than 30 mm/h. The path attenuation exceedance probability over the link is also presented.
Difierent techniques has been proposed by various authors in difierent regions of the world to mo... more Difierent techniques has been proposed by various authors in difierent regions of the world to model the solution to radio wave propagation problems, but most of these techniques have not considered modeling the primary parameters on which other radioclimatology factors are based. This paper has therefore focused on working from the basics, by considering the initial parameters on which radioclimatological factors were based. These initial parameters namely; temperature, pressure and humidity were modeled with vertical height increase using one year radio propagation data and six years radio propagation data in Durban, KwaZulu Natal province of South Africa. A simplifled statistical technique is employed in the analysis of this data. 1. INTRODUCTION The propagation of electromagnetic waves around the earth is in∞uenced by the properties of the earth and the atmosphere (1{5). The earth is an inhomogeneous body whose electromagnetic prop- erties vary considerably as we go from one point to another, its properties varying with temperature, pressure and humidity. According to ITU-R Recommendation P.530 (3), the propagation loss on a terrestrial line-of-sight path relative to free space loss is the sum of difierent contributions which includes: attenuation due to atmospheric gases; difiraction fading due to obstruction or partial obstruction of the path; fading due to multipath and attenuation due to precipitation. Each of these contributions has its
This paper presents an alternative approach to model the transfer characteristics of power lines ... more This paper presents an alternative approach to model the transfer characteristics of power lines for broadband power line communications (PLC). The model is developed by considering the power line to be a two-wire transmission line and the theory of transverse electromagnetic (TEM) wave propagation applied. The characteristic impedance and attenuation constant of the power line are determined through measurements. These parameters are used in model simplification and determination of other model parameters for typical indoor multi-tapped transmission line system. The transfer function of the PLC channel is determined by considering the branching sections as parallel resonant circuits attached to the main line. The model is evaluated through comparison with measured transfer characteristics of known topologies and it is in good agreement with measurements.
While rainfall is a major cause of communication impairment at microwave and millimeter bands, th... more While rainfall is a major cause of communication impairment at microwave and millimeter bands, the effect of rain attenuation in the Ethiopian microwave links, has so far remained as unstudied. Therefore, in this paper, the rain rate distribution at 15 minutes integration time is predicted for different percentage of time of the year based on two years of rain intensity data obtained from National Meteorological Agency (NMA) of Ethiopia. The rainfall rate for one minute integration time not exceeded 0.01% of the time is calculated using ITU-R and Chebil designations, it is found that the highest rainfall rate at 0.01 % of time for any location in Ethiopia, does not exceed 64 mm/h. The ITU-R model is then applied to estimate and analyze rainfall attenuation over terrestrial radio links for ten sites in Ethiopia. The attenuation is predicted for frequencies from 1-150 GHz, with variable distances. The results show that Bahirdar is predicted to experience the largest effect of rain attenuation whereas, Dubti, has the lowest attenuation.
Parameter estimation of linear regression models usually employs least squares (LS) and maximum l... more Parameter estimation of linear regression models usually employs least squares (LS) and maximum likelihood (ML) estimators. While maximum likelihood remains one of the best estimators within the classical statistics paradigm to date, it is highly reliant on the assumption about the joint probability distribution of the data for optimal results. In this paper we use the Generalized Method of Moments (GMM) to address the deficiencies of LS/ML in order to estimate the underlying data generating process (DGP). We use GMM as a statistical technique that incorporate observed noise data with the information in population moment conditions to determine estimates of unknown parameters of the underlying model. Periodic impulsive noise (short-term) has been measured, deseasonalized and modeled using GMM. The numerical results show that the model captures the noise process accurately.
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Aug 1, 2018
The ever-increasing demand for telecommunication services and the already established power line ... more The ever-increasing demand for telecommunication services and the already established power line network makes power line communication (PLC)a very attractive mode of data transmission. However, the power line cables are designed for the transmission of high voltage at low frequencies, which is contrary to the low voltages, and high frequencies needed for the transfer of data signals. Moreover, the power line network is randomly loaded. This in turn results in impedance mismatch with considerable noise and high attenuation. The variant nature of input impedance requires impedance profiling of the PLC network. It is with this profiling that impedance adaptive techniques can be designed and applied to both the input and output of PLC modems, which tend to operate at 50 Ω. If the behaviour of PLC network impedance can be modelled, then the characteristics of the power line network can be known. This will in turn ensure the design of more efficient and effective impedance matching networks. This paper describes modelling of input impedance in a power line channel using parallel resonance circuits. TR5048 Vector Network Analyzer was used to obtain impedance measurements for a frequency range of 1–30 MHz at the power line communication laboratory at the University of KwaZulu-Natal, Durban, South Africa for different test network topologies and configurations considering the extreme cases that include open-circuit and short-circuit terminations. It is observed that the position of the maximum values of impedance depends on the number of branches, the length of the branch and the terminating load impedance. The model shows a good agreement with measurement. The impedance measured was then profiled into minimum, average and maximum bounds.
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Aug 1, 2018
Fifth generation wireless communication networks will demand massive bandwidth for high data rate... more Fifth generation wireless communication networks will demand massive bandwidth for high data rates. The millimeter wave frequency bands will play an important role in the 5G wireless networks due to the available huge chunk of bandwidth. Deployment of wireless networks will require an appropriate path loss model for site-specific environments such as indoor corridors. Structural design and building materials call for development of such models. This work presents a multi-frequency dual-slope large-scale path loss model based on measurements performed in two distinct indoor environments made of glass and concrete. Measurements were conducted at 14 to 22 GHz in typical indoor corridors using a costume-designed channel sounder based on Rohde and Schwarz SMF 100 A signal generator and FSIQ 40 signal analyzer with 120 MHz bandwidth for distances ranging 2 m to 24 m in line-of-sight and non-line-of-sight scenarios. The acquired measurement data of 36,000 directional power delay profiles for 18 transmitter-receiver combinations were analyzed to model a directional dual-slope path loss model for vertically polarized antennas. The directional dual-slope path loss was synthesized with consideration of propagation mechanisms such as reflection and diffraction effectively causing modal attenuation as the signal propagates along the corridor due to wave guiding effect. A breakpoint was established that demonstrates the effects of modal attenuation in a waveguide like corridor. The model was evaluated by performing a comparative analysis on the directional dual-slope path loss model on various indoor corridors with different structural design and materials with well-known alfa-beta-gamma model. The results were observed to give a better prediction of path loss at 14 to 22 GHz over ABG model as fitted to the measurement data. Moreover, the results show that the wave guiding effect is pronounced after the breakpoint due to both free space and multi-modal propagation.
In this paper we will discuss the estimation of powerline communication (PLC) asynchronous impuls... more In this paper we will discuss the estimation of powerline communication (PLC) asynchronous impulsive noise volatility by studying the conditional variance of the noise time series residuals. In our approach, we use the Generalized Autoregressive Conditional Heteroskedastic (GARCH) models on the basis that in our observations, the noise time series residuals indicates heteroskedasticity. By performing an ordinary least squares (OLS) regression of the noise data, the empirical results show that the conditional variance process is highly persistent in the residuals. The variance of the error terms are not uniform, in fact, the error terms are larger at some portions of the data than at other time instances. Thus, PLC impulsive noise often exhibit volatility clustering where the noise time series is comprised of periods of high volatility followed by periods of high volatility and periods of low volatility followed by periods of low volatility. The burstiness of PLC impulsive noise is therefore not spread randomly across the time period, but instead has a degree of autocorrelation. This provides evidence of time-varying conditional second order moment of the noise time series. Based on these properties, the noise time series data is said to suffer from heteroskedasticity. Numerical results provide evidence that the proposed model is capable of providing an accurate stochastic representation of the impulsive noise in the 1-30MHz frequency band. The parameter estimates of the model indicates a high degree of persistence in conditional volatility of impulsive noise which is a strong evidence of explosive volatility.
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Papers by Thomas Afullo