Radio over fiber (RoF) is an empowering technology for the next-generation wireless networks incl... more Radio over fiber (RoF) is an empowering technology for the next-generation wireless networks including fifth generation cloud radio access networks. In this paper, we propose a new fronthaul interface which has been demonstrated for a 20-MHz LTE signal having 64-Quadrature amplitude modulation (QAM) modulation over 50 km of standard single-mode fiber. The proposed methodology potentially reduces the overall bandwidth requirement of the link. The performance analysis has been demonstrated for conventional analog RoF (A-RoF) and proposed digital RoF (D-RoF). As a figure of merit, the performance evaluation of the two architectures is reported by analyzing error vector magnitude (EVM), signal-to-noise ratio and eye-opening penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 50 km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog-to–digital-converter resolution bits. For the D-RoF link, the EVM was measured to be less than 2 % at 50 km. This is within the LTE specifications, proving it as a cost and power effective solution for next-generation wireless networks.
Machine learning (ML) methodologies have been looked upon recently as a potential candidate for m... more Machine learning (ML) methodologies have been looked upon recently as a potential candidate for mitigating nonlinearity issues in optical communications. In this paper, we experimentally demonstrate a 40-Gb/s 256-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF) system for 50 km of standard single mode fiber length which utilizes support vector machine (SVM) decision method to indicate an effective nonlinearity mitigation. The influence of different impairments in the system is evaluated that includes the influences of Mach-Zehnder Modulator nonlinearities, in-phase and quadrature phase skew of the modulator. By utilizing SVM, the results demonstrated in terms of bit error rate and eye linearity suggest that impairments are significantly reduced and licit input signal power span of 5dBs is enlarged to 15 dBs.
We propose a 10-Gb/s 64-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF)... more We propose a 10-Gb/s 64-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF) system for 50 km of standard single mode fiber length which utilizes Reinforcement Learning (RL) SARSA based decision method to indicate an effective decision which mitigates nonlinearity. By utilizing RL-SARSA algorithm, the results demonstrate that significant reduction can be obtained in terms of bit error rate.
Analog Radio-over-Fiber (A-RoF) communication technology constitutes a promising technique for ne... more Analog Radio-over-Fiber (A-RoF) communication technology constitutes a promising technique for next generation radio access networks thanks to its relatively low bandwidth requirements. Within this context, an efficient predistortion technique is proposed, which can be applied to reduce the impairments of A-RoF systems due to the combined effects of frequency chirp of the laser source and chromatic dispersion of the optical channel. The radio frequency signal is firstly put in digital form through an analog to digital converter, then the predistortion operation is realized, and finally the resulting signal is put again into analog form. A comprehensive analysis on the theoretical basis of the proposed approach is presented, together with the approximations introduced, which makes it practically realizable. The improvements on the quality of the received signal due to the proposed solution are illustrated with reference to scenarios of applicative interest. The performance of proposed technique is evaluated in terms of adjacent channel leakage ratio and error vector magnitude when long term evolution signal is applied at the input.
The article proposes a Digital Predistortion (DPD) methodology that substantially
meliorates the ... more The article proposes a Digital Predistortion (DPD) methodology that substantially meliorates the linearity of limited range Mobile Front Haul links for the extant Long-Term Evolution (LTE) and future (5G) networks. Specifically, the DPD is employed to Radio over Fiber links that contrive of Vertical Cavity Surface Emitting Lasers (VCSELs) working at 850 nm. Both, Memory and Generalized Memory Polynomial models are implied to Single Mode (SM) and Multi-Mode (MM) VCSELs respectively. The effectiveness of the proposed DPD methodology is analyzed in terms of Normalized Mean Square Error, Normalized Magnitude, Normalized phase and Adjacent Channel Power Ratio. The demonstration has been carried out with a complete (Long Term Evolution) LTE frame of 10 ms having 5 MHz bandwidth with 64-QAM modulation configuration. Additionally, the effectuality of the proposed DPD technique is evaluated for varying levels of input power and link lengths. The experimental outcomes signify the novel capability of the implied DPD methodology for different link lengths to achieve higher system linearization.
International Topical Meeting on Microwave Photonics (MWP), 2018
This article proposes a Digital Predistortion (DPD) technique in order to enhance the linearity o... more This article proposes a Digital Predistortion (DPD) technique in order to enhance the linearity of short and limited range Mobile Front Haul (MFH) links for the present Long-Term Evolution (LTE) and future (5G) cellular networks. The proposed technique is applied to 850 nm Single Mode Vertical Cavity Surface Emitting Lasers (VCSELs) and Standard Single-Mode Fibers (SSMFs) low cost and low consumption Radio-over-Fiber (RoF) link. Memory Polynomial is employed using Indirect Learning Architecture (ILA). Moreover, the resilience of the DPD approach to changes in input power levels is investigated. The improvements in the quality of the received signal due to the proposed solution are illustrated with reference to scenarios of applicative interest. The performance of proposed technique is evaluated in terms of Adjacent Channel Power Ratio (ACPR) and Normalized Mean Square Error (NMSE) for entire LTE frame of 10ms for 5 MHz band signal having 64 QAM modulation format.
In recent years, the demand of efficient and broadband wireless access has escalated, for which R... more In recent years, the demand of efficient and broadband wireless access has escalated, for which Radio over Fiber (RoF) is considered as an appropriate solution. In this paper, we present a Digitized Transmission of 20 MHz LTE signal having 64 quadrature amplitude modulation over 70 Km of Standard Single Mode Fiber (SSMF) for broadband wireless signal transportation and distribution applications. The performance analysis has been evaluated for conventional Analog Radio over Fiber (A-RoF) and proposed Digital Radio over Fiber (D-RoF). The bandpass sampling technique is discussed and employed for digitizing the RF signal. As a figure of merit, the performance evaluation of two architectures is reported by analyzing the Error Vector Magnitude (EVM), Signal to Noise Ratio and Eye-Opening Penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 70 Km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog to digital converter (ADC) resolution bits. An experimental validation of the proposed analytical D-RoF model is done for 30 Km of SSMF, whose experimental results are in line with the analytical ones. The evaluated parameters are within the LTE specifications, proving this is a cost and power effective solution for next generation wireless networks.
IEEE Microwave and Wireless Components Letters 2019(1):1-3 , 2019
The article unfolds a digital predistortion (DPD) technique that improves the linearity of limite... more The article unfolds a digital predistortion (DPD) technique that improves the linearity of limited range mobile front haul links for the contemporary long-term evolution (LTE) and future (5G) networks. In particular, the proposed technique is applied to radio-over-fiber links based on single-mode (SM) vertical cavity surface emitting lasers emitting at 850 nm and standard SM fibers. Both the memory and generalized memory polynomial models are exploited for the predistorter and identified by utilizing indirect learning architecture. The impact of the DPD technique is observed by the link performance improvement in terms of normalized mean square error and adjacent channel power ratio, referring to complete LTE frames of 10 ms occupying 5-MHz bandwidth and having 64-quadrature amplitude modulation format. Furthermore, the effectiveness of the DPD approach, when varying input power levels, is investigated. The experimental results demonstrate the capability of the proposed DPD technique to achieve promising linearization performance.
Radio over fiber (RoF) is a promising solution for the next-generation wireless networks includin... more Radio over fiber (RoF) is a promising solution for the next-generation wireless networks including fifth-generation Cloud/Centralized Radio Access Network (C-RAN). There exists a possibility to use Sigma Delta Modulated RoF (S-DRoF) that combines the advantages of analog RoF and digital RoF by means of sigma delta modulation (SDM) at the transmitter side subsequently replacing the employment of expensive and high-speed digital-to-analog converters. In this paper, we demonstrate the usage of second-order SDM for LTE 20 MHz signal having 64 QAM modulation on a central carrier frequency of 1.14 GHz for the implementation of S-DRoF for 20 km of standard single mode fiber with baud rate from 25 to 100 Mbaud. Furthermore, a comprehensive analysis of the design of SDM is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude, constellations and adjacent channel power ratio. The results show that the proposed architecture performance is in with accordance to the limitations set by the 3GPP (Third Generation Partnership Project) standards and is a reasonable choice either for upgrading installed systems as well as for the new deployments.
Sigma Delta Radio over Fiber (S-DRoF) systems are looked upon as an enabling technology due to th... more Sigma Delta Radio over Fiber (S-DRoF) systems are looked upon as an enabling technology due to their advantages that comes due to combination of analog and digital radio over fiber (RoF) systems. In this paper, we have proposed and experimentally demonstrated a Multi-stAge-noise-SHaping (MASH) based Sigma Delta Modulated RoF system targeting 5G C-RAN (cloud/centralized radio access network) fronthaul applications. The evaluation has been done for LTE 20 MHz signal having 256 quadrature amplitude modulation with a carrier frequency of 3.5 GHz up to 5 Km of Standard Single Mode Fiber (SSMF). Furthermore, a comprehensive analysis of the design is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude (EVM) and adjacent channel leakage ratio. It is concluded that S-DRoF substantiates the desired range of the 5G C-RAN fronthaul networks.
Radio over fiber (RoF) is an empowering technology for the next-generation wireless networks incl... more Radio over fiber (RoF) is an empowering technology for the next-generation wireless networks including fifth generation cloud radio access networks. In this paper, we propose a new fronthaul interface which has been demonstrated for a 20-MHz LTE signal having 64-Quadrature amplitude modulation (QAM) modulation over 50 km of standard single-mode fiber. The proposed methodology potentially reduces the overall bandwidth requirement of the link. The performance analysis has been demonstrated for conventional analog RoF (A-RoF) and proposed digital RoF (D-RoF). As a figure of merit, the performance evaluation of the two architectures is reported by analyzing error vector magnitude (EVM), signal-to-noise ratio and eye-opening penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 50 km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog-to–digital-converter resolution bits. For the D-RoF link, the EVM was measured to be less than 2 % at 50 km. This is within the LTE specifications, proving it as a cost and power effective solution for next-generation wireless networks.
Machine learning (ML) methodologies have been looked upon recently as a potential candidate for m... more Machine learning (ML) methodologies have been looked upon recently as a potential candidate for mitigating nonlinearity issues in optical communications. In this paper, we experimentally demonstrate a 40-Gb/s 256-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF) system for 50 km of standard single mode fiber length which utilizes support vector machine (SVM) decision method to indicate an effective nonlinearity mitigation. The influence of different impairments in the system is evaluated that includes the influences of Mach-Zehnder Modulator nonlinearities, in-phase and quadrature phase skew of the modulator. By utilizing SVM, the results demonstrated in terms of bit error rate and eye linearity suggest that impairments are significantly reduced and licit input signal power span of 5dBs is enlarged to 15 dBs.
We propose a 10-Gb/s 64-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF)... more We propose a 10-Gb/s 64-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF) system for 50 km of standard single mode fiber length which utilizes Reinforcement Learning (RL) SARSA based decision method to indicate an effective decision which mitigates nonlinearity. By utilizing RL-SARSA algorithm, the results demonstrate that significant reduction can be obtained in terms of bit error rate.
Analog Radio-over-Fiber (A-RoF) communication technology constitutes a promising technique for ne... more Analog Radio-over-Fiber (A-RoF) communication technology constitutes a promising technique for next generation radio access networks thanks to its relatively low bandwidth requirements. Within this context, an efficient predistortion technique is proposed, which can be applied to reduce the impairments of A-RoF systems due to the combined effects of frequency chirp of the laser source and chromatic dispersion of the optical channel. The radio frequency signal is firstly put in digital form through an analog to digital converter, then the predistortion operation is realized, and finally the resulting signal is put again into analog form. A comprehensive analysis on the theoretical basis of the proposed approach is presented, together with the approximations introduced, which makes it practically realizable. The improvements on the quality of the received signal due to the proposed solution are illustrated with reference to scenarios of applicative interest. The performance of proposed technique is evaluated in terms of adjacent channel leakage ratio and error vector magnitude when long term evolution signal is applied at the input.
The article proposes a Digital Predistortion (DPD) methodology that substantially
meliorates the ... more The article proposes a Digital Predistortion (DPD) methodology that substantially meliorates the linearity of limited range Mobile Front Haul links for the extant Long-Term Evolution (LTE) and future (5G) networks. Specifically, the DPD is employed to Radio over Fiber links that contrive of Vertical Cavity Surface Emitting Lasers (VCSELs) working at 850 nm. Both, Memory and Generalized Memory Polynomial models are implied to Single Mode (SM) and Multi-Mode (MM) VCSELs respectively. The effectiveness of the proposed DPD methodology is analyzed in terms of Normalized Mean Square Error, Normalized Magnitude, Normalized phase and Adjacent Channel Power Ratio. The demonstration has been carried out with a complete (Long Term Evolution) LTE frame of 10 ms having 5 MHz bandwidth with 64-QAM modulation configuration. Additionally, the effectuality of the proposed DPD technique is evaluated for varying levels of input power and link lengths. The experimental outcomes signify the novel capability of the implied DPD methodology for different link lengths to achieve higher system linearization.
International Topical Meeting on Microwave Photonics (MWP), 2018
This article proposes a Digital Predistortion (DPD) technique in order to enhance the linearity o... more This article proposes a Digital Predistortion (DPD) technique in order to enhance the linearity of short and limited range Mobile Front Haul (MFH) links for the present Long-Term Evolution (LTE) and future (5G) cellular networks. The proposed technique is applied to 850 nm Single Mode Vertical Cavity Surface Emitting Lasers (VCSELs) and Standard Single-Mode Fibers (SSMFs) low cost and low consumption Radio-over-Fiber (RoF) link. Memory Polynomial is employed using Indirect Learning Architecture (ILA). Moreover, the resilience of the DPD approach to changes in input power levels is investigated. The improvements in the quality of the received signal due to the proposed solution are illustrated with reference to scenarios of applicative interest. The performance of proposed technique is evaluated in terms of Adjacent Channel Power Ratio (ACPR) and Normalized Mean Square Error (NMSE) for entire LTE frame of 10ms for 5 MHz band signal having 64 QAM modulation format.
In recent years, the demand of efficient and broadband wireless access has escalated, for which R... more In recent years, the demand of efficient and broadband wireless access has escalated, for which Radio over Fiber (RoF) is considered as an appropriate solution. In this paper, we present a Digitized Transmission of 20 MHz LTE signal having 64 quadrature amplitude modulation over 70 Km of Standard Single Mode Fiber (SSMF) for broadband wireless signal transportation and distribution applications. The performance analysis has been evaluated for conventional Analog Radio over Fiber (A-RoF) and proposed Digital Radio over Fiber (D-RoF). The bandpass sampling technique is discussed and employed for digitizing the RF signal. As a figure of merit, the performance evaluation of two architectures is reported by analyzing the Error Vector Magnitude (EVM), Signal to Noise Ratio and Eye-Opening Penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 70 Km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog to digital converter (ADC) resolution bits. An experimental validation of the proposed analytical D-RoF model is done for 30 Km of SSMF, whose experimental results are in line with the analytical ones. The evaluated parameters are within the LTE specifications, proving this is a cost and power effective solution for next generation wireless networks.
IEEE Microwave and Wireless Components Letters 2019(1):1-3 , 2019
The article unfolds a digital predistortion (DPD) technique that improves the linearity of limite... more The article unfolds a digital predistortion (DPD) technique that improves the linearity of limited range mobile front haul links for the contemporary long-term evolution (LTE) and future (5G) networks. In particular, the proposed technique is applied to radio-over-fiber links based on single-mode (SM) vertical cavity surface emitting lasers emitting at 850 nm and standard SM fibers. Both the memory and generalized memory polynomial models are exploited for the predistorter and identified by utilizing indirect learning architecture. The impact of the DPD technique is observed by the link performance improvement in terms of normalized mean square error and adjacent channel power ratio, referring to complete LTE frames of 10 ms occupying 5-MHz bandwidth and having 64-quadrature amplitude modulation format. Furthermore, the effectiveness of the DPD approach, when varying input power levels, is investigated. The experimental results demonstrate the capability of the proposed DPD technique to achieve promising linearization performance.
Radio over fiber (RoF) is a promising solution for the next-generation wireless networks includin... more Radio over fiber (RoF) is a promising solution for the next-generation wireless networks including fifth-generation Cloud/Centralized Radio Access Network (C-RAN). There exists a possibility to use Sigma Delta Modulated RoF (S-DRoF) that combines the advantages of analog RoF and digital RoF by means of sigma delta modulation (SDM) at the transmitter side subsequently replacing the employment of expensive and high-speed digital-to-analog converters. In this paper, we demonstrate the usage of second-order SDM for LTE 20 MHz signal having 64 QAM modulation on a central carrier frequency of 1.14 GHz for the implementation of S-DRoF for 20 km of standard single mode fiber with baud rate from 25 to 100 Mbaud. Furthermore, a comprehensive analysis of the design of SDM is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude, constellations and adjacent channel power ratio. The results show that the proposed architecture performance is in with accordance to the limitations set by the 3GPP (Third Generation Partnership Project) standards and is a reasonable choice either for upgrading installed systems as well as for the new deployments.
Sigma Delta Radio over Fiber (S-DRoF) systems are looked upon as an enabling technology due to th... more Sigma Delta Radio over Fiber (S-DRoF) systems are looked upon as an enabling technology due to their advantages that comes due to combination of analog and digital radio over fiber (RoF) systems. In this paper, we have proposed and experimentally demonstrated a Multi-stAge-noise-SHaping (MASH) based Sigma Delta Modulated RoF system targeting 5G C-RAN (cloud/centralized radio access network) fronthaul applications. The evaluation has been done for LTE 20 MHz signal having 256 quadrature amplitude modulation with a carrier frequency of 3.5 GHz up to 5 Km of Standard Single Mode Fiber (SSMF). Furthermore, a comprehensive analysis of the design is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude (EVM) and adjacent channel leakage ratio. It is concluded that S-DRoF substantiates the desired range of the 5G C-RAN fronthaul networks.
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Papers by Usman Hadi
meliorates the linearity of limited range Mobile Front Haul links for the extant Long-Term
Evolution (LTE) and future (5G) networks. Specifically, the DPD is employed to Radio over
Fiber links that contrive of Vertical Cavity Surface Emitting Lasers (VCSELs) working at
850 nm. Both, Memory and Generalized Memory Polynomial models are implied to Single
Mode (SM) and Multi-Mode (MM) VCSELs respectively. The effectiveness of the proposed
DPD methodology is analyzed in terms of Normalized Mean Square Error, Normalized
Magnitude, Normalized phase and Adjacent Channel Power Ratio. The demonstration has
been carried out with a complete (Long Term Evolution) LTE frame of 10 ms having 5
MHz bandwidth with 64-QAM modulation configuration. Additionally, the effectuality of
the proposed DPD technique is evaluated for varying levels of input power and link lengths.
The experimental outcomes signify the novel capability of the implied DPD methodology
for different link lengths to achieve higher system linearization.
meliorates the linearity of limited range Mobile Front Haul links for the extant Long-Term
Evolution (LTE) and future (5G) networks. Specifically, the DPD is employed to Radio over
Fiber links that contrive of Vertical Cavity Surface Emitting Lasers (VCSELs) working at
850 nm. Both, Memory and Generalized Memory Polynomial models are implied to Single
Mode (SM) and Multi-Mode (MM) VCSELs respectively. The effectiveness of the proposed
DPD methodology is analyzed in terms of Normalized Mean Square Error, Normalized
Magnitude, Normalized phase and Adjacent Channel Power Ratio. The demonstration has
been carried out with a complete (Long Term Evolution) LTE frame of 10 ms having 5
MHz bandwidth with 64-QAM modulation configuration. Additionally, the effectuality of
the proposed DPD technique is evaluated for varying levels of input power and link lengths.
The experimental outcomes signify the novel capability of the implied DPD methodology
for different link lengths to achieve higher system linearization.