This special issue includes extensions of invited and top-scored optical networking papers that were presented at the Optical Fiber Communication (OFC) Conference, held in San Diego, CA, March 11-15, 2018. We present an overview of the array of topics covered in the papers, tied in with some historical perspectives on OFC.
{"title":"Introduction to the OFC 2018 special issue","authors":"J. M. Simmons","doi":"10.1364/JOCN.11.00OFC1","DOIUrl":"https://doi.org/10.1364/JOCN.11.00OFC1","url":null,"abstract":"This special issue includes extensions of invited and top-scored optical networking papers that were presented at the Optical Fiber Communication (OFC) Conference, held in San Diego, CA, March 11-15, 2018. We present an overview of the array of topics covered in the papers, tied in with some historical perspectives on OFC.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125887745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To accommodate the service paradigm shift driven by the now amazingly wide variety of services, telecom operators must overcome many challenges in redesigning their network infrastructure to attain system flexibility, scalability, and cost effectiveness. A key part of the solution is the recent advent of network virtualization based on commodity hardware. We propose a unique edge-server architecture that combines network virtualiza- tion with advanced digital signal processing (DSP) technology. Our architecture has the server's central processing unit running application layer functions and a generalpurpose accelerator running dissimilar physical layer functions, including advanced DSP. To elucidate the power budget capability of our coherent detection scheme, a hardware experiment demonstrates the optical power budget of 45.2 dB for quadrature phase-shift keying signals of 5 Gbit/s bit rate.
{"title":"Coherent receiver DSP implemented on a general-purpose server for a full software-defined access system","authors":"Sang-Yuep Kim, Takahiro Suzuki, J. Kani, A. Otaka","doi":"10.1364/JOCN.11.000A96","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A96","url":null,"abstract":"To accommodate the service paradigm shift driven by the now amazingly wide variety of services, telecom operators must overcome many challenges in redesigning their network infrastructure to attain system flexibility, scalability, and cost effectiveness. A key part of the solution is the recent advent of network virtualization based on commodity hardware. We propose a unique edge-server architecture that combines network virtualiza- tion with advanced digital signal processing (DSP) technology. Our architecture has the server's central processing unit running application layer functions and a generalpurpose accelerator running dissimilar physical layer functions, including advanced DSP. To elucidate the power budget capability of our coherent detection scheme, a hardware experiment demonstrates the optical power budget of 45.2 dB for quadrature phase-shift keying signals of 5 Gbit/s bit rate.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123185679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Paolucci, F. Civerchia, A. Sgambelluri, A. Giorgetti, F. Cugini, P. Castoldi
Next-generation edge nodes interfacing innovative IT clusters, 5G fronthaul, and internet of things (IoT) gateways to the optical metro/core network will require advanced and dynamic online quality of service (QoS) per-flow traffic treatment, assuring ultra-low latency requirements. However, current software-defined networking (SDN) implementations (e.g., OpenFlow) do not support forwarding procedures based on the network state, profile variations, and the history of flow statistics at the node level. Currently, such procedures require intervention by the SDN controller, leading to scalability issues and additional latency in data plane forwarding. Moreover, severe security challenges are expected to affect such nodes and threaten IT resources. Thus, increasing bandwidths will require direct deep packet inspection to avoid involvement of the SDN controller, as performed currently, or dedicated and costly security systems. This paper leverages on the potential of the programming protocol-independent packet processors (P4) open source language, recently introduced by the inventors of OpenFlow, to program the data plane structure and behavior of an SDN switch. P4 is able to instantiate custom pipelines and stateful objects, enabling complex workflows, user-defined protocols/headers, and finite state machines enforcement. Moreover, P4 allows portable implementations over different hardware targets, thus opening the way to open source fully programmable devices. Special effort is dedicated to motivate and apply P4 within a multilayer edge scenario, proposing the architecture and the applicability of an SDN P4-enabled packet-over-optical node. Moreover, three specific multilayer use cases covering dynamic traffic engineering (TE) (e.g., traffic offload and optical bypass) and cybersecurity (e.g., distributed denial of service port scan) are discussed and addressed through P4-based solutions. Experimental evaluations have been conducted over a multilayer SDN network exploiting reference P4 software switches (i.e., the behavioral model version 2, or BMV2) and field-programmable gate arrays (FPGAs) at 10 gigabit Ethernet optical interfaces. Extensive results report effective dynamic TE and cybersecurity mitigation enforcement at P4 switches without any controller intervention, showing excellent scalability performance and overall latencies practically in line with current commercial OpenFlow switches.
{"title":"P4 Edge node enabling stateful traffic engineering and cyber security","authors":"F. Paolucci, F. Civerchia, A. Sgambelluri, A. Giorgetti, F. Cugini, P. Castoldi","doi":"10.1364/JOCN.11.000A84","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A84","url":null,"abstract":"Next-generation edge nodes interfacing innovative IT clusters, 5G fronthaul, and internet of things (IoT) gateways to the optical metro/core network will require advanced and dynamic online quality of service (QoS) per-flow traffic treatment, assuring ultra-low latency requirements. However, current software-defined networking (SDN) implementations (e.g., OpenFlow) do not support forwarding procedures based on the network state, profile variations, and the history of flow statistics at the node level. Currently, such procedures require intervention by the SDN controller, leading to scalability issues and additional latency in data plane forwarding. Moreover, severe security challenges are expected to affect such nodes and threaten IT resources. Thus, increasing bandwidths will require direct deep packet inspection to avoid involvement of the SDN controller, as performed currently, or dedicated and costly security systems. This paper leverages on the potential of the programming protocol-independent packet processors (P4) open source language, recently introduced by the inventors of OpenFlow, to program the data plane structure and behavior of an SDN switch. P4 is able to instantiate custom pipelines and stateful objects, enabling complex workflows, user-defined protocols/headers, and finite state machines enforcement. Moreover, P4 allows portable implementations over different hardware targets, thus opening the way to open source fully programmable devices. Special effort is dedicated to motivate and apply P4 within a multilayer edge scenario, proposing the architecture and the applicability of an SDN P4-enabled packet-over-optical node. Moreover, three specific multilayer use cases covering dynamic traffic engineering (TE) (e.g., traffic offload and optical bypass) and cybersecurity (e.g., distributed denial of service port scan) are discussed and addressed through P4-based solutions. Experimental evaluations have been conducted over a multilayer SDN network exploiting reference P4 software switches (i.e., the behavioral model version 2, or BMV2) and field-programmable gate arrays (FPGAs) at 10 gigabit Ethernet optical interfaces. Extensive results report effective dynamic TE and cybersecurity mitigation enforcement at P4 switches without any controller intervention, showing excellent scalability performance and overall latencies practically in line with current commercial OpenFlow switches.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115933295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Digital radio over fiber (D-RoF), one of the candidates for 5G mobile fronthaul networks, is known for its high reliability and strong robustness against nonlinear channel degradations, which makes it suitable for short-reach fronthaul links supporting ultra-reliable low-latency communication in 5G. However, traditional D-RoF technology is limited by its lower bandwidth efficiency. In this paper, based on our previous work, advanced data-compression techniques with adaptive non-uniform quantizers and differential coding are discussed for a significant improvement of bandwidth efficiency in fronthaul networks. High-order differential coding based on a least- mean-square algorithm has been proposed to further improve the compression ratio with low complexity and high adaptability. By jointly applying a non-uniform quantizer and a differentiator, the signal-to-quantization-noise ratio and bandwidth efficiency can be improved by around 10 dB and 40%-60%, respectively, depending on the modulation formats in our proposed solution. We have experimentally demonstrated the transmission of 200 Gbps fronthaul links over a fiber distance of 80 km. The system is capable of encapsulating 110 × 120 MHz 5G new radio carriers with error-vector magnitude lower than 0.8%.
{"title":"Statistical data compression and differential coding for digital radio-over-fiber-based mobile fronthaul","authors":"Mu Xu, Z. Jia, Jing Wang, L. A. Campos, G. Chang","doi":"10.1364/JOCN.11.000A60","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A60","url":null,"abstract":"Digital radio over fiber (D-RoF), one of the candidates for 5G mobile fronthaul networks, is known for its high reliability and strong robustness against nonlinear channel degradations, which makes it suitable for short-reach fronthaul links supporting ultra-reliable low-latency communication in 5G. However, traditional D-RoF technology is limited by its lower bandwidth efficiency. In this paper, based on our previous work, advanced data-compression techniques with adaptive non-uniform quantizers and differential coding are discussed for a significant improvement of bandwidth efficiency in fronthaul networks. High-order differential coding based on a least- mean-square algorithm has been proposed to further improve the compression ratio with low complexity and high adaptability. By jointly applying a non-uniform quantizer and a differentiator, the signal-to-quantization-noise ratio and bandwidth efficiency can be improved by around 10 dB and 40%-60%, respectively, depending on the modulation formats in our proposed solution. We have experimentally demonstrated the transmission of 200 Gbps fronthaul links over a fiber distance of 80 km. The system is capable of encapsulating 110 × 120 MHz 5G new radio carriers with error-vector magnitude lower than 0.8%.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121815699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Tanimura, T. Hoshida, T. Kato, Shigeki Watanabe, H. Morikawa
To address the open and diverse situation of future optical networks, it is necessary to find a methodology to accurately estimate the value of a target quantity in an optical performance monitor (OPM) depending on the high-level monitoring objectives declared by the network operator. Using machine learning techniques partially enables a trainable OPM; however, it still requires the feature selection before the learning process. Here, we show the OPM that uses a convolutional neural network (CNN) with a digital coherent receiver to deal with the abundance of training data required for convergence and pre-processing of input data by human engineers needed for feature (representation) extraction. To proof a concept of the OPM based on CNN, we experimentally demonstrate that a CNN can learn an accurate optical signal-to-noise-ratio (OSNR) estimation functionality from asynchronously sampled data right after intradyne coherent detection. We evaluate bias errors and standard deviations of a CNN-based OSNR estimator for six combinations of modulation formats and symbol rates and confirm that the proposed OSNR estimator can provide accurate estimation results (<0.4 dB bias errors and standard deviations). Additionally, we investigate filters in the trained CNN to reveal what the CNN learned in the training phase. This is a valuable step toward designing autonomous "self-driving" optical networks.
{"title":"Convolutional neural network-based optical performance monitoring for optical transport networks","authors":"T. Tanimura, T. Hoshida, T. Kato, Shigeki Watanabe, H. Morikawa","doi":"10.1364/JOCN.11.000A52","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A52","url":null,"abstract":"To address the open and diverse situation of future optical networks, it is necessary to find a methodology to accurately estimate the value of a target quantity in an optical performance monitor (OPM) depending on the high-level monitoring objectives declared by the network operator. Using machine learning techniques partially enables a trainable OPM; however, it still requires the feature selection before the learning process. Here, we show the OPM that uses a convolutional neural network (CNN) with a digital coherent receiver to deal with the abundance of training data required for convergence and pre-processing of input data by human engineers needed for feature (representation) extraction. To proof a concept of the OPM based on CNN, we experimentally demonstrate that a CNN can learn an accurate optical signal-to-noise-ratio (OSNR) estimation functionality from asynchronously sampled data right after intradyne coherent detection. We evaluate bias errors and standard deviations of a CNN-based OSNR estimator for six combinations of modulation formats and symbol rates and confirm that the proposed OSNR estimator can provide accurate estimation results (<0.4 dB bias errors and standard deviations). Additionally, we investigate filters in the trained CNN to reveal what the CNN learned in the training phase. This is a valuable step toward designing autonomous \"self-driving\" optical networks.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130756278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Asaka, H. Ujikawa, H. Uzawa, Hirotaka Nakamura, J. Kani, A. Otaka, J. Terada
To quickly meet the diverse requirements imposed by emerging new services on optical access networks, we recently proposed the new concept of "flexible access system architecture" (FASA), which features the disaggregation of time-critical applications. This paper introduces our activities on FASA along with related technical trends. As our key ongoing challenge, the modularization of the dynamic bandwidth assignment function in a passive optical network is reviewed, and information on its use cases, approach, and sequences is given. Furthermore, a reference hardware implementation of FASA for mobile service is described.
{"title":"Disaggregation of time-critical applications in flexible access system architecture [invited]","authors":"K. Asaka, H. Ujikawa, H. Uzawa, Hirotaka Nakamura, J. Kani, A. Otaka, J. Terada","doi":"10.1364/JOCN.11.000A33","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A33","url":null,"abstract":"To quickly meet the diverse requirements imposed by emerging new services on optical access networks, we recently proposed the new concept of \"flexible access system architecture\" (FASA), which features the disaggregation of time-critical applications. This paper introduces our activities on FASA along with related technical trends. As our key ongoing challenge, the modularization of the dynamic bandwidth assignment function in a passive optical network is reviewed, and information on its use cases, approach, and sequences is given. Furthermore, a reference hardware implementation of FASA for mobile service is described.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130586179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Following the extensive investigations of the research community throughout the last five years regarding transmission performance when roughly doubling the channel symbol rate in WDM systems from generic 32 GBaud to more than 60 GBaud, this evolution is about to appear in the field in the next twelve months. The general sense is that it will reduce the cost per transmitted gigabit per second (Gb/s), once the related faster optoelectronic interfaces become mature enough. This paper refines this consideration by quantifying the related transponders saving per Gb/s on three distinct backbone WDM networks equipped with elastic optoelectronic regenerators. It also reports how much extra network capacity stems from routing individual 64 GBaud subcarriers 75 GHz apart to serve connections, the capacities of which range from 100 Gb/s to 1 Tb/s. It eventually discusses the impact on the network performance when constraining the regenerators' placement along the light paths of the accommodated services or when simplifying the elastic regenerators by avoiding internal electrical traffic regrooming.
{"title":"How 64 GBaud optical carriers maximize the capacity in core elastic WDM networks with fewer transponders per Gb/s","authors":"T. Zami, B. Lavigne, M. Bertolini","doi":"10.1364/JOCN.11.000A20","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A20","url":null,"abstract":"Following the extensive investigations of the research community throughout the last five years regarding transmission performance when roughly doubling the channel symbol rate in WDM systems from generic 32 GBaud to more than 60 GBaud, this evolution is about to appear in the field in the next twelve months. The general sense is that it will reduce the cost per transmitted gigabit per second (Gb/s), once the related faster optoelectronic interfaces become mature enough. This paper refines this consideration by quantifying the related transponders saving per Gb/s on three distinct backbone WDM networks equipped with elastic optoelectronic regenerators. It also reports how much extra network capacity stems from routing individual 64 GBaud subcarriers 75 GHz apart to serve connections, the capacities of which range from 100 Gb/s to 1 Tb/s. It eventually discusses the impact on the network performance when constraining the regenerators' placement along the light paths of the accommodated services or when simplifying the elastic regenerators by avoiding internal electrical traffic regrooming.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124169929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Huaiyu Zeng, Xiang Liu, Sharief Megeed, Andy Shen, F. Effenberger
We review recent advances in the field of fiber-wireless convergence to better support cloud radio access networks via high-speed low-latency mobile fronthaul between remote radio units and baseband units. We also present how digital signal processing (DSP) may be used to support both common public radio interfaces (CPRI) in a point-to-point architecture and Ethernet-based CPRI in a point-to-multipoint architecture to achieve high bandwidth efficiency and low processing latency. The use of DSP-enabled next-generation passive optical networks (PON), such as 50 Gb/s PON, to support mobile fronthaul in a resource-efficient manner will also be discussed.
{"title":"Digital signal processing for high-speed fiber-wireless convergence [invited]","authors":"Huaiyu Zeng, Xiang Liu, Sharief Megeed, Andy Shen, F. Effenberger","doi":"10.1364/JOCN.11.000A11","DOIUrl":"https://doi.org/10.1364/JOCN.11.000A11","url":null,"abstract":"We review recent advances in the field of fiber-wireless convergence to better support cloud radio access networks via high-speed low-latency mobile fronthaul between remote radio units and baseband units. We also present how digital signal processing (DSP) may be used to support both common public radio interfaces (CPRI) in a point-to-point architecture and Ethernet-based CPRI in a point-to-multipoint architecture to achieve high bandwidth efficiency and low processing latency. The use of DSP-enabled next-generation passive optical networks (PON), such as 50 Gb/s PON, to support mobile fronthaul in a resource-efficient manner will also be discussed.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114996231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Proietti, Xiaoliang Chen, Kaiqi Zhang, Gengchen Liu, M. Shamsabardeh, A. Castro, L. Velasco, Zuqing Zhu, S. Yoo
In multi-domain elastic optical networks with alien wavelengths, each domain needs to consider intradomain and interdomain alien traffic to estimate and guarantee the required quality of transmission (QoT) for each lightpath and perform provisioning operations. This paper experimentally demonstrates an alien wavelength performance monitoring technique and machine-learning-aided QoT estimation for lightpath provisioning of intradomain/ interdomain traffic. Testbed experiments demonstrate modulation format recognition, QoT monitoring, and cognitive routing for a 160 Gbaud alien multi-wavelength light- path. By using experimental training datasets from the testbed and an artificial neural network, we demonstrated an accurate optical-signal-to-noise ratio prediction with an accuracy of ~95% when using 1200 data points.
{"title":"Experimental demonstration of machine-learning-aided QoT estimation in multi-domain elastic optical networks with alien wavelengths","authors":"R. Proietti, Xiaoliang Chen, Kaiqi Zhang, Gengchen Liu, M. Shamsabardeh, A. Castro, L. Velasco, Zuqing Zhu, S. Yoo","doi":"10.1364/JOCN.11.0000A1","DOIUrl":"https://doi.org/10.1364/JOCN.11.0000A1","url":null,"abstract":"In multi-domain elastic optical networks with alien wavelengths, each domain needs to consider intradomain and interdomain alien traffic to estimate and guarantee the required quality of transmission (QoT) for each lightpath and perform provisioning operations. This paper experimentally demonstrates an alien wavelength performance monitoring technique and machine-learning-aided QoT estimation for lightpath provisioning of intradomain/ interdomain traffic. Testbed experiments demonstrate modulation format recognition, QoT monitoring, and cognitive routing for a 160 Gbaud alien multi-wavelength light- path. By using experimental training datasets from the testbed and an artificial neural network, we demonstrated an accurate optical-signal-to-noise ratio prediction with an accuracy of ~95% when using 1200 data points.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124026027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Time synchronization is a long-standing challenge in distributed systems like indoor/outdoor positioning, coordinated multi-point in 4G/5G mobile communication, etc., which require nanosecond-level high-reliable time sync networks. At present, a widely adopted solution for time sync networks is the precision time protocol specified in IEEE 1588v2, which can provide sub-microsecond sync accuracy. In addition, a novel network time sync method called distributed time synchronization has also been proposed recently, which can achieve 50-ns-level accuracy and stronger survivability in metro, regional, and backbone networks. However, both of the above methods encounter difficulties in achieving nanosecond sync accuracy and network reliability simultaneously. In this paper, by analyzing the main factors influencing the degradation of time sync accuracy, we reveal that the finite clock resolution is a major barrier to achieving nanosecond-level time synchronization. In order to establish a low-cost, high-reliability, and sub-nanosecond-level time sync network, we propose a novel network time sync method called double-frequency distributed time synchronization (DF- DTS). By selecting two specific and distinct frequencies for the sending and receiving clocks of the nodes/devices being synchronized, the time sync errors induced by the finite clock resolution can be reduced by a statistical approach. We set up a theoretical model for the DF-DTS and analyze the time sync accuracy through both mathematical derivations and network simulations. Furthermore, we propose a failure-restoration mechanism to enhance the reliability of DF-DTS networks by improving the time sync accuracy under failures and reducing the failure recovery time. Finally, we conduct both point- to-point and network time sync experiments to validate the proposed DF-DTS method. The results demonstrate that DF-DTS can achieve sub-nanosecond-level sync accuracy that is 1-2 orders of magnitude higher than the clock resolution in a prototype four-node DF-DTS network. Moreover, a network simulation under failure cases is conducted, and the results show that our method has significant advantages in both time sync accuracy and recovery time in the failure-restoration process compared to IEEE 1588v2.
{"title":"High-reliability sub-nanosecond network time synchronization method enabled by double-frequency distributed time synchronization","authors":"Ruijie Luo, Nan Hua, Xiaoping Zheng, Bingkun Zhou","doi":"10.1364/OFC.2018.M2E.6","DOIUrl":"https://doi.org/10.1364/OFC.2018.M2E.6","url":null,"abstract":"Time synchronization is a long-standing challenge in distributed systems like indoor/outdoor positioning, coordinated multi-point in 4G/5G mobile communication, etc., which require nanosecond-level high-reliable time sync networks. At present, a widely adopted solution for time sync networks is the precision time protocol specified in IEEE 1588v2, which can provide sub-microsecond sync accuracy. In addition, a novel network time sync method called distributed time synchronization has also been proposed recently, which can achieve 50-ns-level accuracy and stronger survivability in metro, regional, and backbone networks. However, both of the above methods encounter difficulties in achieving nanosecond sync accuracy and network reliability simultaneously. In this paper, by analyzing the main factors influencing the degradation of time sync accuracy, we reveal that the finite clock resolution is a major barrier to achieving nanosecond-level time synchronization. In order to establish a low-cost, high-reliability, and sub-nanosecond-level time sync network, we propose a novel network time sync method called double-frequency distributed time synchronization (DF- DTS). By selecting two specific and distinct frequencies for the sending and receiving clocks of the nodes/devices being synchronized, the time sync errors induced by the finite clock resolution can be reduced by a statistical approach. We set up a theoretical model for the DF-DTS and analyze the time sync accuracy through both mathematical derivations and network simulations. Furthermore, we propose a failure-restoration mechanism to enhance the reliability of DF-DTS networks by improving the time sync accuracy under failures and reducing the failure recovery time. Finally, we conduct both point- to-point and network time sync experiments to validate the proposed DF-DTS method. The results demonstrate that DF-DTS can achieve sub-nanosecond-level sync accuracy that is 1-2 orders of magnitude higher than the clock resolution in a prototype four-node DF-DTS network. Moreover, a network simulation under failure cases is conducted, and the results show that our method has significant advantages in both time sync accuracy and recovery time in the failure-restoration process compared to IEEE 1588v2.","PeriodicalId":371742,"journal":{"name":"IEEE/OSA Journal of Optical Communications and Networking","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133422966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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